Industrial + Specialty Printing - January/February 2012 issue

January/february 2012

www.industrial-printing.net

Materials and Methods For Printed OLEDs P. 20

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CONTENTS

INDUSTRIAL + SPECIALTY PRINTING January/February 2012 • Volume 03/Issue 01

16

FEATURES

12 Printing Solar PV

Alan Rae, Ph.D., TPF enterprises LLC Find out how to take advantage of the more interesting opportunities, printing techniques, and materials requirements.

16 Inkjet Technology and Printed Electronics

Tim Phillips, Ph.D., Xennia Technology Ltd. The use of inkjet printing in electronics manufacturing is just beginning.

Discover how you can take advantage of each technological advancement.

COLUMNS 10 Business Management

Kari Freudenberger, ST Media Group Int’l This article discusses ways to use Website landing pages to prompt visitors to take action.

30 Printed Electronics

Chris Wargo, PChem Associates A Guide to High-Performance Conductive Ink

36 Printing Methods

Mark White, Fabrico Solar PV System labels come with very specific printing requirements. Learn about some of them here.

20 Revolutions in Display and Lighting Manufacturing

38 Industry Insider

26 Future for Functional Printing

40 Shop Tour

Barry Young, OLED Association This article explores printing technologies for OLEDs and examines the ways in which OLEDs are transforming how we define structure and light.

Gail Flower See what experts have to say about what’s in store for industrial applications.

John Fraser, Ohio Gravure Technologies The microelectronics industry is experiencing growth in active electronic circuits printed in high volumes on inexpensive substrates.

In-mold electronics is among the processes unique to San Diego, CA-based Canyon Graphics.

DEPARTMENTS 4 Editorial Response 6 Product Focus 39 Advertising Index ON THE COVER

www.linkedin.com/ groups?gid=2658424 www.twitter.com/iSPmag

www.facebook.com/iSPmag

B

industrial-printing.net/ news-trends/functionality-blog

INDUSTRIAL + SPECIALTY PRINTING, (ISSN 2125-9469) is published bi-monthly by ST Media Group International Inc., 11262 Cornell Park Dr., Cincinnati, OH 45242-1812. Telephone: (513) 421-2050, Fax: (513) 362-0317. No charge for subscriptions to qualified individuals. Annual rate for subscriptions to non-qualified individuals in the U.S.A.: $42 USD. Annual rate for subscriptions in Canada: $70 USD (includes GST & postage); all other countries: $92 (Int’l mail) payable in U.S. funds. Printed in the U.S.A. Copyright 2012, by ST Media Group International Inc. All rights reserved. The contents of this publication may not be reproduced in whole or in part without the consent of the publisher.

The publisher is not responsible for product claims and representations. POSTMASTER: Send address changes to: Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. Change of address: Send old address label along with new address to Industrial + Specialty Printing, P.O. Box 1060, Skokie, IL 60076. For single copies or back issues: contact Debbie Reed at (513) 421-9356 or Debbie.Reed@ STMediaGroup.com. Subscription Services: ISP@halldata.com, Fax: (847) 763-9030, Phone: (847) 763-4938, New Subscriptions: www.industrial-printing.net/subscribe.

The cover shows OLED printing on flexible substrates. Cover courtesy GE Global Research, Niskayuna, NY. Cover design by Keri Harper.

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EDITORIAL RESPONSE

Photovoltaics in the Long Run GAIL FLOWER

www.industrial-printing.net

STEVE DUCCILLI Group Publisher steve.duccilli@stmediagroup.com

Editor

On November 30, 2011, The Omaha WorldHerald Co. announced that Warren Buffett said he would buy the newspaper from his home town for $200 million because wellrun newspapers have a future and Omaha is a vibrant community that he wanted to support. Many newspapers are struggling in a changing and monetarily stretched time in history. Is digital the answer? Who knows, but independent thought, even coverage, and an informed community are vital to a democracy—and this is one example of supporting such thought in the future.

About the same time, The Washington Post reviewed Berkshire Hathaway Chairman Warren Buffett’s debate about tax fairness. When Buffett said that his secretary paid a higher tax rate than he does, everyone started thinking about it.

Now President Obama has weighed in with what he calls the Buffett Rule, proposing a minimum effective tax rate on all income, irrespective of its source. Why not take from the rich to support the poor by taxing them evenly? This is as old fashioned as Robin Hood. Some people, it appears, have too much money and openly admit it.

Couldn’t some of that money support the development of solar power as a boost to the economy?

As a matter of fact, in December 2011, Buffett’s wind-energy company jumped into supporting solar energy, agreeing to purchase the Topaz Solar Farm project in Central California for more than $2 billion.

Forbes reported that MidAmerican Energy Holdings, owned by Berkshire Hathaway and other investors, agreed to acquire the 550-megawatt pant on the Carrizo Plain one of California’s remaining large prairies.

The agreements seem to be in place.

First Solar will construct and operate

Industrial + Specialty Printing

GREGORY SHARPLESS Associate Publisher gregory.sharpless@stmediagroup.com

the Topaz project. Construction began in November 2011 and will continue to be complete by 2015, providing lots of new jobs in a state that could use this type of investment. Pacific Gas and Electric has signed a 25-year agreement to purchase electricity from Topaz. California’s mandate to generate 33% of its power from renewable sources is closer to being met.

So what’s the problem? There are the wildflowers, the reintroduced pronghorn antelope, the antelope squirrel, and other species to look out for because they live on the Carrizo Plain. There’s also the problem of eventual e-waste, and California is a state known for forward thinking when it comes to electronics.

In 2008, Samsung launched a recycling program for all Samsung product lines.

Beginning that year, consumers could drop off their Samsung-branded consumer electronics sold in the U.S. at collection sites in each state in a take-back program.

Nokia expanded its take-back program to make recycling easier for any mobile phone, mobile-phone battery, or mobile-phone accessory.

However, for the acres and acres of PV cells, what’s the plan for taking care of the end-of-lifecycle products? Fortunately, there are some sustainable-technology communities, such as the Silicon Valley Toxics Coalition (SVTC), that have a vision of electronic products that result in sustainable communities and worksites, wherever the high-tech industry happens to exist (www.etoxics.org).

Sustainable energy is vital, especially clean energy, for lots of reasons. But a really longterm vision that includes what to do with the products we create integrates more of what it means to be human.

4 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

GAIL FLOWER Editor gail.flower@stmediagroup.com BEN P. ROSENFIELD Managing Editor ben.rosenfield@stmediagroup.com KERI HARPER Art Director keri.harper@stmediagroup.com LINDA VOLZ Production Coordinator linda.volz@stmediagroup.com BUSINESS DEVELOPMENT MANAGER STEVE DUCCILLI steve.duccilli@stmediagroup.com EDITORIAL ADVISORY BOARD Joe Fjelstad, Brendan Florez, Dolf Kahle, Bruce Kahn, Ph.D., Rita Mohanty, Ph.D., Scott Moncrieff, Randall Sherman, Mike Young, Wim Zoomer

JERRY SWORMSTEDT Chairman of the Board TEDD SWORMSTEDT President KARI FREUDENBERGER Director of Online Media

CUSTOMER SERVICE Industrial + Specialty Printing Magazine Customer Service P.O. Box 1060 Skokie, IL 60076 ISP@halldata.com F: 847-763-9040

advisory board

Joe Fjelstad

Verdant Electronics

Joseph Fjelstad (josephfjelstad@aol.com) is a 34-year veteran of the electronics-interconnection industry and is an international authority, author, columnist, lecturer, and innovator who holds more than 150 issued and pending US patents in the field. He is the founder and president of Verdant Electronics, a firm dedicated to environmentally friendly electronics assembly. He is co-founder and CEO of SiliconPipe, a specialist in high-speed interconnection-architecture design, much of which is based on flexible-circuit technology. Prior to founding SiliconPipe, he worked with IC-package-technology developer Tessera Technologies, where he was appointed the company’s first fellow. Fjelstad and his innovations have received many industry awards and accolades.

rita mohanty, ph.d.

Speedline Technology

Rita Mohanty (rmohanty@speedlinetech.com) is the director of advanced development at Speedline Technology and a certified Six Sigma Master Black Belt instructor. She has more than 15 years of experience in industries and academics relating to engineering and electronic polymers, electronic packaging, and board assembly. She is a patent holder and has authored and edited books on electronics and numerous technical papers. Mohanty is active in and holds various leadership positions with IMAPS, SMTA, IPC, iNEME, and SGIA. She received her Ph.D. in chemical engineering from the University of Rhode Island.

Scott MonCrieff Canyon Graphics Inc.

brendan florez Polyera

Joseph Fjelstad (josephfjelstad@aol.com) is a 34-year veteran of the electronics-interconnection industry and is an international authority, author, columnist, lecturer, and innovator who holds more than 150 issued and pending US patents in the field. He is the founder and president of Verdant Electronics, a firm dedicated to environmentally friendly electronics assembly. He is co-founder and CEO of SiliconPipe, a specialist in high-speed interconnection-architecture design, much of which is based on flexible-circuit technology. Prior to founding SiliconPipe, he worked with IC-package-technology developer

Dolf Kahle

Visual Marking Systems, Inc.

Dolf Kahle (rkahle@vmsinc.com) is the CEO of Twinsburg, OH-based Visual Marking Systems, Inc., (VMS), a company that specializes in the OEM durable-product-identification market and manufactures overlays, decals, and decorative trim for Fortune 1000 companies. Beyond the OEM market, VMS also produces fleet graphics, P-O-P products, and durable signage for the public-transportation market. VMS is an ISO 9000- certified company that enjoys statewide recognition as a Lean Enterprise. Kahle is an active member of SGIA, SPIRE, and GPI. He served on the SGIA board for more than 10 years and was its chairman in 1999. He is currently the chairman of SPIRE. He holds a bachelor’s degree in mechanical engineering from the University of Michigan and an MBA from Arizona State University.

Bruce kahn, ph.d.

Scott Moncrieff (NEED EMAIL ADDRESS HERE) is president and CEO of Canyon Graphics Inc. located in San Diego, California.

Mr. Moncrieff started Canyon Graphics over 30 years ago and has specialized in In-mold Decoration for the last 9 years. As one of the few totally vertically integrated IMD companies in the US, Canyon Graphics has produced millions of film appliqués and IMD parts during this period. Having been involved in printed electronics over the years has made it possible for Canyon Graphics to develop various IME (In-mold Electronics)

RANDALL SHERMAN New Venture Research

Randall Sherman (rsherman@newventureresearch. com) is the president and CEO of New Venture Research, a technology market research firm. He holds a B.S. in astrophysics, an M.S. in electrical engineering from the University of Colorado, and an M.B.A. from Edinburgh School of Business. Visit www. newventureresearch.com for more information.

mike young

Imagetek Consulting Int’l.

Mike Young (mikeyyoung@aol.com) has spent 40 years as a specialist in high-definition graphic and industrial screen printing. He is an SGIA Fellow, a member of the Academy of Screen Printing Technology, and a recipient of the prestigious Swormstedt Award for technical writing. He frequently writes for industry trade publications and speaks at international industry events. Young has published several technical books on advanced screen-printing techniques and frequently conducts seminars for high-profile screen-printing companies worldwide. Young is a consultant with Imagetek Consulting Int’l.

wim zoomer

Technical Language

Printed Electronics Consulting

Bruce Kahn (bkahn@electronicsprinting.com) is a consultant who specializes in the multidisciplinary fields of printable electronics, nanotechnology, RFID, and smart packaging.

Kahn holds a Ph.D. in chemistry from the University of Nebraska and is the author of more than 75 publications, including the recently published “Developments in Printable Organic Transistors,” “Printed and Thin Film Photovoltaics and Batteries,” and “Displays and Lighting: OLED, e-paper, electroluminescent and beyond.” He is a frequent lecturer and author, and he regularly teaches workshops in the U.S. and abroad.

Wim Zoomer (wimzoomer@planet.nl) is owner of Nijmegen, Netherlands-based Technical Language, a consulting and communication business that focuses on flatbed and reelto-reel rotary screen printing and other printing processes. He has written numerous articles for international screen-printing, art, and glass-processing magazines and is frequently called on to translate technical documents, manuals, books, advertisements, and other materials in English, French, German, Spanish, and Dutch. He is also the author of the book, “Printing Flat Glass,” as well as several case studies that appear online. He holds a degree in chemical engineering. You can visit his Website at www.technicallanguage.eu. january/february 2012 |

product focus

The latest equipment and materials for industrial printing

Industrial Inkjet Printer Industrial Inkjet Ltd. (www.industrialij. com) calls its XYPrint a complete, highly accurate inkjet system designed for a wide range of materials-deposition applications, lab use, or pilotline manufacturing. It uses fixed printheads from Konica Minolta under which materials scan along two axes at speeds up to 60 in./sec (1.5 m/sec).

XYPrint supports a maximum image area of 11.69 x 8.27 in. (297 x 210 mm) and subdrop size sizes of 42, 14, and 4 pl. Printheads are available for water-based, solvent, oil, or UV inks. Special printhead versions are available to accommodate strong solvents, acids, or alkalis. The system’s operating software allows access to printhead parameters (waveform, voltage, and frequency), imaging resolution, ICC profiles, and more. Options include variable-image software, remote control via TCP/IP, heated vacuum platen, alignment camera, UV lamp, and more. Custom systems can be produced.

Portable CPV Tracker Soitec (www.soitec.com) recently announced that it has expanded its family of concentrator photovoltaic (CPV) products with the new Plug&Sun, a model the company says is easy to install and is the first standalone mini-tracker consisting of 3 sq m of highly efficient modules. Plug&Sun is designed for use in sunny regions with no power grid or unreliable grid connections. According to Soitec, the mobile power-generating station’s durability and tolerance for high temperatures make it well suited for remote usage.

Plug&Sun aims to supplement or replace existing electrification solutions, such as power generators or other forms of renewable energy. Soitec cites efficiency close to 30% and notes that each Plug&Sun uses a two-axis tracker to generate up to 2.3 kWp of electricity. It is compatible with the different electrical standards, allowing it to power common electrical devices.

| Industrial + Specialty Printing www.industrial-printing.net

Laser Cutter

Spar tanics

Spartanics (www.spartanics.com) recently debuted the L-350, billed as a high-speed laser cutter with a single-head design that supports a 210-Îźm spot size in a (350-mm) cutting field at speeds as fast as (80 m/min). The system is engineered to automate webspeed optimization. It includes UV coating stations, lamination, and slitting and sheeting options. Spartanics says superior cut quality is achieved with polyester, polycarbonate, polypropylene, metalized and paper materials, and more. Sealed CO2 supplies are used to power lasers, Spartanics explains, to minimize costs for CO2 and to avoid the inherent quality issues of open systems for CO2 delivery.

Inkjet Films

Inkjet Print Controller

3M Commercial Graphics (www.3m.com) calls 3M Scotchcal Graphic Film Series IJ10 and Series IJ11 its most budget-friendly addition to its product line. The films support inkjet printing with UV, solvent, eco-solvent, and latex inks. They come in 164-ft (50-m) rolls. According to 3M the films are perfect for permanentadhesive applications such as signage, decals, and more. IJ10 and IJ11 are 3.1-mil vinyl products with a clear (IJ10) or gray-colored (IJ11) permanent, pressure-sensitive adhesive. Available in gloss and matte finishes, the films can be protected by IJ10-114, a clear product that can be used as a digitally printable clear film and an overlaminate.

Dimatix Print Systems (www.dimatix.com) describes its Merlin D2 as a general- purpose, console-style, industrial inkjet print controller that supports a wide variety of configured printhead clusters. The controller is capable of driving a total of 48 Spectra 256-jet printheads configured in one- to four-printhead clusters.

Each head cluster can be one to four colors. Merlin D2 also can be configured to support various jetting fluids, including those formulated for food applications. Fluid and electrical umbilicals up to 35 ft (10.7 m) connect the controller to the printhead clusters.

The controller may be operated in a standalone, distributed-networked mode or via standard industrial-line-control interfaces. An optional user-interface monitor and keyboard allows for the local access and control of functional parameters through a graphical user interface based on the Windows XP operating system.

Screen Press for Conveyorized Manufacturing Systematic Automation Inc.

Systematic Automation Inc. (www.systauto.com) has developed a screen-printing machine that prints on flat products while in motion on a conveyor. The printer is engineered to match product speed with the screen movement. As Systematic Automatic explains it, an encoder on the conveyor sends information to the printer’s servo motor to match speed, even if the speed varies during the print cycle. The modular design permits mounting to an existing production line. Screen printing of ceramic, solvent, or UV inks and adhesives are examples of compatible the applications.

Visualizer Tool for Metallic Imaging Color-Logic (www.color-logic.com) recently revealed that its Process Metallic Color System will ship with FX-Viewer, a new tool designed to enable graphic designers and brand owners to visualize the complete array of Color-Logic metallic and special effects on their designer workstations. Color-Logic says users previously had no means of accurately visualizing Color-Logic metallic hues or special effects, because the Process Metallic Color System creates five-color files for printing with metallic inks or with white inks on metallic substrates. FX-Viewer creates the metallic look and special effects of Color-Logic files on the desktop workstation monitor. Color-Logic customers who are current with their maintenance agreements will receive one copy and may buy additional copies at a discount.

SEND US YOUR PRODUCT NEWS Email ben.rosenfield@stmediagroup.com

january/february 2012 |

ADA Kits for Engraving Systems Roland DGA Corp. (www.rolanddga.com) has introduced ADA Sign Solutions, a kit designed exclusively for use with the company’s EGX350 and EGX-400/600 engraving machines. Roland says the kits come with everything needed to produce tamper-resistant ADA and Raster Braille signage, enabling EGX users to meet state and federal mandatory compliance regulations that go into effect on March 15, 2012. The new ADA regulations apply to any sign that designates permanent rooms and spaces, and where goods and services are made available to the public, including resorts, hotels, hospitals and other medical facilities, entertainment and cultural sites, and educational facilities.

Each kit builds on a Roland EGX engraver with an engraving tool set, Braille and profile cutters, CADlink EngraveLab Expert software, Rowmark engravable ADA-compliant materials, adhesive sheets, an Accent Signage Raster Pen License Kit, and a self-contained chip-removal system. The EGX-350 ADA Kit comes standard with a Manual Raster Pen; the EGX-400 and EGX-600 ADA Kits include both the Manual and Auto-Raster Pen.

Polyester film Eastman Kodak Company’s Industrial Materials Group (www. kodak.com) recently announced the development of what the company says is a next generation of polyester film with extraordinarily low haze-growth characteristics when the film is subjected to high heat in a variety of industry applications. The new film is an extension to the Kodak ESTAR (PET) Film portfolio. According to Kodak, it features improved haze stability along with high clarity, optical-grade surface quality, and shrinkage characteristics of 1% or less in the machine and transverse directions. The film is manufactured with a proprietary inline process to control shrinkage and haze and is available without any coating or with an adhesion-promoting primer on one or both sides of the film. The film is available in a thickness of 127 μm, with a maximum width of 56.75 in. (1441 mm).

Nanopowder Ink Novacentrix (www.novacentrix.com) manufactures spherical aluminum nanopowder with an average particle size of 25 m2/gm.

The powder has 75% active aluminum content by mass and a 2-3 nm oxide passivation layer, the company says. The high specific surface area leads to high reaction rates, making it suitable for systems such as primers, propellants, and explosives. The powder for ink is available in 50 – 150 gram evaluation quanitities and comes packed under argon, and shipped in oxygen-barrier bags (up to 200 gm per bag).

| Industrial + Specialty Printing www.industrial-printing.net

Roland DG A Corp.

Inks for Industrial Applications Independent Ink (www.independentink.com) recently announced the availability of a house-brand of inks and fluids for industrial applications. Ten different products are represented in this brand category for different types of industrial inkjet printers, including drop-on-demand, valvejet, and continuous inkjet, as well as name brands including XAAR, Trident, Videojet, and more. Formulations include Yellow (starter pack), Yellow to UV Clear (quart), White (starter pack), Black (quart), Absolute Black (42-ml P45A cartridge), Fast Dry Black (42-ml P45A cartridge), and Wash (quart).

Radio-Activated Display PolyIC GmbH & Co. KG (www.polyic.com) introduced Polylogo| RAD (radio-activated display), a system composed of two components: an activator, which is similar to RFID readers and provides energy by transmitting on a standardized frequency of 13.56 MHz; and a radio-powered tag made from printed electronics (a display, rectifier and an antenna). Typical applications are for product marketing, games, brand protection, and authenticity control. These thin and flexible inlays can be processed into credit-card formats or into packaging.

Screen Cleaner Franmar Chemical (www.franmar.com) says it formulated its Green Again screen cleaner to work safely without odors. The products is created from upcycled vegetable oil and is bottled by gravity. According to Franmar, Green Again is non-toxic and non-evaporable, rinses off with water, leaves no residue, is 100% biodegradable, and is safe for drains. Green Again bottles are made from recycled materials and a packed and shipped in recycled cardboard. Franmar says Green Again is recognized by the U.S. EPA.

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business management

Turning Clicks into Customers Through Custom Landing Pages Kari Freudenberger ST Media Group

What is the most important shot in a game of pool? The next one.

When developing your online strategy, don’t forget to line up your shots. Plan the whole experience.

Advertising gives you visibility. Your ad gets you noticed. But how do you turn a click into a customer? Create a clear path from attraction to acquisition.

The key to generating customers is to turn your Website into a customer acquisition engine that gets web visitors to do something: Learn more. Sign up. Call.

Buy. To arrive at your goal, you have to lead people.

Getting them there Marketing methods such as search engine optimization, banner ads, promotions, direct mail, e-mail, television, and print advertising should not lead visitors to your home page. Home pages often have too many options and no clear path to follow.

When developing a marketing campaign intended to take someone to a Web page, create a unique page designed especially for that campaign. This landing page is a stand-alone page to which you can send your customers that drives them to action.

It targets specific audiences and leads them directly to a sale, or when necessary, directs them deeper into your site.

A landing page is a more effective marketing tool than a regular Web page because it is specifically designed to highlight one or a few products or services.

It is typically more focused than other Web pages. At their simplest level, landing

pages provide limited information with two options: buy now or learn more.

The landing page is a hard sell. The intent is to lead a visitor to conversion. It should contain enough information about the specific product or service to motivate a transaction. The transaction is the final step in the experience. Sometimes it’s making a purchase, but it can be as simple as filling out a contact form. The point is the person on the other end of the website gives you what you want.

The call to action The singular purpose of a landing page is to make someone do something—to generate a transaction. The most important part of a landing page is called the primary call to action. It prompts visitors to do something by stating exactly what you want them to do.

The primary call to action is to buy now (or sign up, get a quote, or whatever you decide leads to conversion). This receives prime real estate and a prominent graphical treatment on the landing page. Most often, designers use a button with the specific verb on it: Buy Now, Get a Quote, etc.

The secondary action to learn more is slightly less noticeable, but it is still highlighted somehow on the page. This streamlines the conversion process, allowing those customers who are ready to buy to act and providing those customers who need more information with the resources they want.

An effectively designed landing page does not provide every piece of information

10 | Industrial + Specialty Printing www.industrial-printing.net

Sample landing page

a visitor might want before the transaction.

That’s where the secondary call to action comes in: Learn More. This directs the visitor deeper into your Website, where they can find more detailed information about what you’re offering.

An effective landing page may have two options, but the calls to action all eventually lead to the same place: the acquisition page. Landing pages are all about customer acquisition.

Navigation Landing pages are unique in that they are merely means to an end and, therefore, do not have to follow the same constructs of a company Website. While it follows

usability best practices to have global navigation for your site on every page, the landing page can survive without it. If it confuses the customer and detracts from those calls to action, it’s better to leave it off. Whatever you choose to do, make sure the navigation is clear and simple.

Usability Making your site easy to use relates directly to customer acquisition and conversion. The site must be organized to make the content and navigation as intuitive as possible and to point to the calls to action.

Note that all pages on the site, not just the landing pages, should include a prominent call to action.

An intuitive site allows the visitors to reassure themselves that your offerings are right for them. It encourages visitors to explore the offerings to their own level of comfort. That does not mean that the content should be endlessly deep, requiring visitors to dig and dig. A critical decision point is how much to give them before you

require them to transact with you. The idea is to allow the visitor to intuitively self-select any selling point they need about any of your products or services.

Landing-page guidelines When building a landing page, certain guidelines should be followed to make it as effective as possible.

Your landing page should graphically match your advertising campaign. Create your landing page to reflect the look and feel of your banner ad, direct mail piece or television commercial. Don’t concern yourself as much with branding the landing page to match the company. They’ll see your corporate brand when they land at the conversion page.

The action you advertise should be available on the landing page. If your advertisement is all about saving 20% on your product, make sure the landing page provides the means to do that. Don’t send customers on a wild goose chase to perform an action. Get it right up front on

that first landing page so conversion is as easy as possible.

Show only the product(s) you’re advertising. This is a tricky one. While you may want to include related products on a landing page, it’s best to stick to the bare minimum; otherwise, you give your customers too many options, making it harder for them to make that snap decision. Customer acquisition on the Web requires simplicity and easy maneuvering.

You need to predict what your customers want and then give it to them in as few steps as possible.

Landing pages are all about turning a click into a customer. By making landing pages a part of your online marketing strategy, you lead your visitors right down the path to conversion.

Kari Freudenberger ST Media Group

Kari Freudenberger is the director of online media, ST Media Group Int’l, Cincinnati, OH.

january/february 2012 | 11

COVER STORY

PRINTING SOLAR PV

This article reviews some of the more interesting opportunities and relates them to printing techniques and materials requirements.

Alan Rae, Ph.D. TPF Enterprises LLC

A

s the photovoltaics (PV) market grows rapidly, at a rate of nearly 20 GW installed in 2011, there is an increasing focus on roll-to-roll and other printing methods as a way to reduce costs and improve performance.

The solar PV industry is at a challenging point in its life cycle. World solar-module capacity at more than 50 GW is more than twice the current annual installation rate. According to Lux Research (www. luxresearchinc.com), crystalline-siliconmodule prices have dropped precipitously to about $1 per peak watt, and only about 25 cents of this is the actual solar cell.

The dramatic drop in module costs means that crystalline-silicon cells are starting to challenge the thin-fi lm market, which still has a cost advantage—but not as large as it was a year ago.

Furthermore, it is not easy to install solar panels yet in many parts of the U.S.—apart from the administrative effort and multiple inspections needed, which can be different in each state, there is a real cost to consider. The average cost of installing a system in the U.S. is about $5.25 per peak watt and the paperwork cost, reportedly averaging about $1 per

watt, is about equal to the cost of the module. The economic downturn is hitting subsidies worldwide. We are seeing a shakeout of higher cost companies like Solyndra, and there is a great deal of uncertainty as countries like the UK and Spain dramatically change feed-in tariffs, causing dramatic swings in demand.

The counterpoint is that there is a lot of positive energy. The low prices mean that energy generation by solar PV is becoming much more competitive with other energy sources that are not reducing in cost. The Department of Energy’s SunShot program looks to provide funds to enable lower installed costs through reductions in module cost, concentrating on thin fi lm where the materials content is lower and reducing the balance of system costs by using microinverters and other techniques to lower balance of system costs. Other programs, such as Solar America Cities, have established ways of simplifying the paperwork.

At the SPI Solar meeting in Dallas in October 2011, the consensus among companies I interviewed was that the U.S. will become the largest installer of solar PV in 2013 as we move off the bottom of the

12 | INDUSTRIAL + SPECIALTY PRINTING www.industrial-printing.net

construction cycle. GE just gave the thinfi lm market a real vote of confidence by announcing a fast-track 400 MW of CdTe manufacturing capacity in Aurora, CO. So what does this mean to the printing industry? It means we will see more conventional and innovative printing techniques used to increase efficiency (more watts per unit area) and to lower costs (more watts per dollar).

A quick word on nomenclature. In the solar industry, thin fi lm refers to anything that isn’t crystalline silicon. Some cells are printed using what would be referred to in the electronics or ceramics industry as thick-fi lm inks and techniques, but here all non-crystalline-silicon cells are referred to as thin fi lm.

PRINTING TECHNOLOGIES AND THEIR APPLICATIONS There are three key aspects to printing a solar cell or module: the substrate, the equipment, and the ink. In the case of solar, the substrate can be silicon, glass, stainless steel, or a polymer such as polyester; all the normal printing and deposition techniques, both sheet fed and roll to roll, are under consideration—but

the solar PV inks can have some unique requirements.

Inks used in the PV industry may be functional semiconductors (e.g. Si, organic semiconductors, or compound semiconductors such as CdTe), conductors (e.g.

Ag, solder, conductive adhesives, and Al), or may be process aids (e.g. masks, etchants, and insulators). These represent a very wide range of materials and processing conditions. Every printing technique has different requirements ranging from 0.001-0.04 Pa.s for drop-on-demand inkjet, to 0.5-50 Pa.s for screen printing, to 30-100 Pa.s for offset lithography—a viscosity range spanning five orders of magnitude!

Functional material content will be affected by printing-process requirements, ranging from 1% by weight for inkjet to 90% by weight for screen printing. Several printing technologies may be needed to produce a single device—screen and inkjet printing, for example. This in itself can present challenges as the cycle time for printing and drying/curing technologies have to be matched; a print time in milliseconds and a curing time of minutes just won’t work as efficiently as matched processes. Even so, the combined cycle time may still be faster than conventional manufacturing. All inks and pastes must necessarily provide: • Printability: the right combination of viscosity, wetting, tack, pot life, etc.

• Processability: rapid drying or curing, preferably below 200°C if they are to be used on organic substrates • Properties: durability and optical, electrical, and electronic performance They must also provide these properties at the lowest possible cost using low-toxicity and available components that must be readily recycled. At 200 W per panel 20 GW means 100 million panels at 60 lb each—that works out to about 2.5 million tons, not including racking materials and balance of systems (racking, tracking, cabling, inverters etc.), and that is a lot of material to recycle in 25 years.

It’s also a lot of material to sell every year into the PV industry and to process as the panels are being made.

INKJET ETCHANT & DOPANT COMBINATION

Heat. Narrow feature etched and n-dopant diffused.

InkJet

SiNx:H P-Type Si

SCREEN PRINTING Figure 1 An illustration of the etchant/dopant process (courtesy of Trident)

CRYSTALLINE SILICON We have three examples of creative solutions in the crystalline-silicon area: Innovalight’s screen-printed selectiveemitter dopant, Trident’s inkjet-deposited etchant/dopant (Figure 1), and DEK’s double-printed silver-paste process.

Innovalight, located in Sunnyvale, CA, and acquired by DuPont in July of 2011, has developed proprietary silicon inks that, used in conjunction with matched DuPont metallization pastes, are designed to boost the amount of electricity produced from sunlight by enabling the production of superior selective-emitter solar cells.

According to industry estimates, selectiveemitter technology could represent 13% of crystalline-silicon solar-cell production by 2013 and up to 38% by 2020.

Innovalight’s silicon ink interacts with the crystalline-silicon wafer and allows a selective doping of the wafer to create the selective emitter structure on a cell.

This is designed to enable a more efficient collection of electrons in the photovoltaic process and improve the baseline efficiency by an absolute 1%.

This product is screen printable; in a typical solar-cell-manufacturing factory, at the back end, just before the solar cell is completed, a screen press is used to print metallic-ink contacts on the wafer, or on the solar cell. The same type of screen press is already used throughout the industry and can be readily configured to print the silicon ink at the front end of the process.

Trident etchant, a single-step, noncontact inkjet process is engineered to enable more efficient front contacts by etching through the silicon nitride (SiNx) anti-reflective coating layer (ARC), then diffusion-doping the silicon emitter. This selective-emitter approach can decouple the metallization process from the etching/doping process, maximizing the results of both areas. Combining the etching and doping processes also eliminates the need for very precise alignment of etchant and dopant in two separate processes.

As a non-contact process, use of the this process can result in up to a 10x reduction in wafer scrap compared to the use of contact selective-emitter processes such as screen or laser etching. Scrap rates currently range from 0.5-1.0% and can be reduced to as low as 0.1%. The etchant/ n-dopant was developed and is manufactured by Alpha PV Technologies for Trident Solar as the result of a collaborative effort of both companies. The material can be jetted from the newly developed Trident 256Jet-S printhead (Figure 2) and etch through the ARC layer when heated to 350°C. When heated to 800°C the n-dopant diffuses into the silicon active emitter. All that is needed to complete the process is a water rinse.

A silicon solar cell needs conductive paths, typically printed with silver pastes, on the front side of the wafer. These current collectors are designed to conduct the electrical current from the silicon without shadowing too much of the wafer surface.

JANUARY/FEBRUARY 2012 | 13

DEK’s work on this process in terms of ink characteristics, screen parameters (mesh size, tension, emulsion) and printing parameters (alignment, squeegee pressure, print speed, off-contact, and print pressure) reportedly achieves aspect-ratio improvements of up to 40%.

Figure 2 (top) The 256Jet-S printhead (courtesy of Trident) Figure 3 (bottom) Roll-to-roll organic-cell printing (courtesy of Konarka)

Any part of the wafer surface not receiving light due to an opaque conductor cannot produce current, reducing cell efficiency.

So intuitively, fewer current collectors should increase efficiency but, unfortunately, printing fewer conductive tracks also reduces the efficiency because silicon is a semiconductor and the extra current generated is more than offset by resistive losses.

Increasing the performance of the silver interconnects is vital to maximizing efficiency and lowering cost—especially when a high silver price ($5 per troy ounce in 2003, $35 per troy ounce in 2011) means that the silver cost can be nearly half the cell cost. Double printing to create a narrow, triangular deposit that minimizes shading but maximizes conductivity has been commercialized by DEK and others to meet this need.

Thin film—inorganic, organic, and hybrid systems In thin film we also have three examples—inorganic cells (NanoSolar and Solexant), organic cells (Konarka’s polymer systems), and hybrid cells (NextGen’s printable/paintable hybrid cells) In inorganic thin-film cells, the majority of manufacturers use vapor-deposition techniques—CVD, sputtering, etc.—and use laser-scribed traces to control electrical pathways. The technology is very similar to producing flatscreen monitors and TVs. These techniques are effective but can be capital-intensive. Printing is an attractive option to reduce cost.

One such company printing thinfilm cells is Nanosolar, which is printing CIGS—copper indium gallium sulfide-selenide. Nanosolar announced in October, 2011 that the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) certified an aperture efficiency of 17.1% for a solar cell fabricated using Nanosolar’s technology for non-vacuum printing on flexible foil. This is significantly higher than other reported efficiencies.

Nanosolar’s process is designed to enable significant cost savings when compared to conventional, vacuum-based deposition techniques. In addition, its high-throughput roll-to-roll printing method delivers a higher capital efficiency and better materials utilization. Together, these advantages can give Nanosolar a path to lower manufacturing costs than competing photovoltaics technologies.

Solexant’s nanocrystal films, made from high-efficiency inorganic materials, are also flexible. Developed at Lawrence Berkeley National Lab (LBNL) by Paul Alivisatos, Ph.D., and his team, Solexant’s printable-nanocrystal technology platform can produce flexible, thin films using a variety of materials through a fast and simple deposition process. Solexant’s first commercial products will be based on printed CdTe nanocrystals. The company plans to commercialize solar cells based

14 | Industrial + Specialty Printing www.industrial-printing.net

on other higher efficiency printed nanocrystal materials over the next few years.

Konarka is a manufacturer of polymer-based, printed, organic-photovoltaic (OPV) technology. Its Power Plastic is semi-transparent and available in multiple colors sizes, giving design freedom to architects and builders for building integrated photovoltaics (BIPV) and other glass applications. Power Plastic’s flexibility enables it to conform to curves and contours. These panels can be bonded or laminated to a variety of materials and create independent power sources out of tension-membrane structures, café umbrellas, awnings, and tents. It is manufactured in a roll-to-roll process (Figure 3) at low cost and low energy consumption, making it favorable for the environment.

Konarka’s organic solar cells are made of recyclable materials and engineered to be unbreakable and non-toxic. To date, they have achieved independently labcertified efficiencies at a category world record 8.4% and are characterized by better weak-light behavior than alternative technologies. Performance is very good at sub-optimal angle of incidence and at elevated temperature unlike traditional photovoltaic materials. With Power Plastic, carbon molecules (fullerene and semiconducting polymers) generate electricity under the influence of light. The solar cells are printed in a cost-effective, roll-toroll process in various widths and lengths.

NextGen Solar is a very early stage company developing inorganic/organic-hybrid material. NextGen won a Clean Energy Trust Award—in fact, the joint Grand Prize—in March, 2011, for these hybrid cells. NextGen Solar PV cells are based on engineered and patent-pending light-harvesting, conductive nano-materials that are potentially at least two times more efficient and at least 40% less expensive than today’s best thin-film solar technologies. NextGen Solar accomplishes these efficiencies by introducing a new type of three-dimensional thin film made of conductive organic and inorganic nanomaterials, which uniquely reduces or eliminates a variety of efficiency losses inherent in other existing technologies. Lower costs arise from dramatically simpler manufacturing methods (solution-based liquids, self-assembly, no cleanroom or high-temperature processes, commercially available

precursors, commercially conventional thin film printing), and are based on less expensive/more abundant raw materials.

The prognosis for printed solar cells Although the market penetration of rollto-roll printed solar cells is low—currently less than 1% of solar-module production— almost all cells use some form of printing.

In general, the techniques used are familiar to the conventional printing industry, but the level of precision and line widths may not be. DEK quotes a precision of ± 12.5 μm at 2 cpk) and line widths of 60 μm to maximize current collection and minimize cell shading and cost.

Chemistry constraints may also require novel solutions such as Trident corrosion-resistant printheads—definitely not the disposable inkjet cartridges we are all used to seeing in our color printers.

Perhaps the biggest threat to printing in crystalline-silicon solar PV is the price of silver. Speculation and demand drive

the silver price and cause significant pain to module manufacturers. A great deal of work is being devoted to backside connection involving minimal silver by using transparent conductive oxides and other non-printed techniques.

The largest threat to printed thin-film modules is the efficiency of vapor-phase deposition—sputtering, CVD, and similar techniques. Although these are vacuum processes and highly capital intensive, they are used in high volume by the flatscreen-display/TV industry, where economies of scale and the availability of Gen 10 glass (2.9 x 3.1 m, 9 x 10 ft) and the equipment to process it have turned conventional wisdom upside down.

Printing has a lot of advantages in the solar PV arena—low cost, non-vacuum, established technology, established infrastructure, roll-to-roll, high-volume capability, flexible or planar substrates—all the characteristics we know and love. Time will tell whether other technologies can be displaced by, or will displace, printed solar

PV technologies. While the jury is still out on the level of market penetration of roll-to-roll processes, I join many others in looking forward to a positive verdict.

Alan Rae, Ph.D.

TPF Enterprises LLC Alan Rae, Ph.D., has worked in the electronics, ceramics, nanotechnology and “clean tech” industries for more than 25 years in the UK and U.S., managing global businesses and technology development at a startup, operating company and at the corporate level. He currently runs TPF Enterprises LLC, a technology commercialization and business development company he founded in 2009, based at the UB Technology Incubator.

He is active in electronics industry associations and standards work. He holds director and VP positions with four new companies and consults for two Fortune 100 companies in alternative energy. He also is technical editor for Global Solar Technology.

january/february 2012 | 15

feature story

Inkjet Technology and Printed Electronics

The use of inkjet printing in electronics manufacturing may be nascent, but as this article explains, each technological advancement makes the process easier to implement.

Tim Phillips

Xennia Technology Ltd. Figure 1 An industrial inkjet system designed for printed-electronics applications

I

n recent years, piezoelectric drop-ondemand inkjet technology has garnered significant interest in the field of printed electronics (Figure 1). The basic process of the technology is as follows: Every nozzle in an inkjet printhead contains an ink chamber attached to the ink reservoir. At the back of the chamber is a piezoelectric crystal that vibrates when it receives a charge of electricity. The crystal vibrates inward, extruding an ink droplet from the nozzle and then vibrates outward to replenish the ink in the chamber by pulling more in from the attached reservoir (Figure 2). This mechanism allows the printing of complex, repeatable patterns as defined by a digital image file.

While printing ink onto paper with a desktop digital printer (or onto many other substrates using an industrial system) is common, the same piezoelectric inkjet process can be used to deposit conductive materials instead, hence the term printed electronics. It should be also be noted that while piezoelectric technology is not the only useful approach to printed electronics its preferable drop size and resolution makes it the current industry standard.

Drop-on-demand inkjet deposition of nano-particle conductive inks has already found niches in the fields of photovoltaics, OLEDs, displays, and RFID. Flexibility sets inkjet apart from traditional methods; inkjet technology allows for the additive deposition of thin-line circuits on a range of substrates

(Figure 3), including those that are three dimensional. This also cuts costs because materials are only deposited where necessary.

This is especially significant because some conductive materials are very expensive.

Inkjet is also non-contact, which means fragile substrates will not be damaged as they are with other methodologies. Printing electronics using inkjet is also significantly less labor intensive and removes the need for expensive tooling or consumables that are a necessary burden in traditional circuit manufacture. The process of tooling is not only time consuming and expensive, but storage and replacements also are an added detriment. Using inkjet, alterations for deposition patterns can be made immediately because there is no wait for a new mask or screen.

Conductive inks Most circuit boards are printed using expensive vacuum deposition and photolithographic patterning, both of which produce high amounts of environmentally damaging toxic waste. This issue does not apply with inkjet technology. Inkjet also enables the use of biodegradable organic materials that cause less harm to the environment.

However, due to the lower stability of organic materials, printed electronic products typically have a shorter life time than their conventionally produced counterparts. Due to the fact that inkjet nozzles are of a very small diameter, this leads to rheological

16 | Industrial + Specialty Printing www.industrial-printing.net

constraints for the ink. The ink typically needs to have a surface tension >35 mN/m and a viscosity of 1-10 cP. These rheological constraints, along with curing temperature issues and expensive material costs, currently impact the amount of applications available for inkjet conductive inks. However, it is expected that as ink compositions and hardware become more advanced, greater opportunities will start to present themselves.

Conductive inks are diverse in terms of composition, functionality, and cost. For this reason, choosing the correct ink for your application is crucial. Inks with the highest conductivity contain silver in the form of nanoparticles, pellets, or flakes. To achieve conductivity levels near to that of bulk silver, high-temperature (greater than 350ËšC) post-process firing or sintering is required.

Due to this restricting factor, applications for this kind of ink are niche. However, there is a small minority of silver-based conductive inks that allow for lower firing temperatures (as low as 70-150ËšC). This enables printing circuits on substrates, such as plastic, that would be unable to withstand the higher firing temperature necessary for most other silver-based inks.

The sintering of silver particles at low temperature presents a difficult technical challenge for manufacturers in creating a successful ink formula. For this reason, conductive inkjet inks fireable at low temperatures are scarce in the market and come

1. Piezo crystal deforms when electrical pulse applied

2. Drop displaced from nozzle

Figure 2 This illustration depicts the basic functions of a piezo inkjet printhead.

at a higher price. Constantly fluctuating silver prices also make cost planning for long-term projects problematic. Applications that use silver-based conductive inks are typically high margin and low volume.

Carbon-based inks are a cheaper alternative but are typically two orders of magnitude less conductive than silver. Carbon-based inks typically suffer from poor substrate adhesion, low flexibility, and poor rub resistance. For these reasons their applications are greatly reduced. One application where carbon-based inks are prevalent is EMI/RF shields for monitor screens.

Copper has been used as a lower-cost alternative to silver but is prone to pyrophoric oxidization, which reduces conductivity significantly. Copper inks also require high-temperature sintering, which restricts applications. The copper can be encapsulated with a thin layer of silver to allow sintering but prevent oxidization. Conductive inks based on graphene are an interesting prospect for the future, particularly for thin, printed, flexible substrates. Graphene is extremely thin and allows electronics to travel at a rapid pace. Compared to silver, graphene is also considerably less expensive, but manufacturers must ensure the precision of the ink-film thickness as differences of a few nanometers can cause a big change in conductivity.

Photovoltaics Solar cells, also known as photovoltaics (PV), are used to convert the sun’s energy into electricity (Figure 4). Because this energy is sustainable and emission free, implementation of solar panels is expected to become much more prevalent in the future as the earth’s natural resources become depleted and more emphasis is placed on reducing our carbon footprint. A current challenge for the mass commercialization of photovolta-

Figure 3 The technical challenge of sintering silver particles at low temperatures makes these conductive inkjet inks scarce and priced at a premium.

ics is increasing cell efficiency in terms of the percentage of photons hitting the cells that are converted to electricity while also bringing costs down to levels comparable to other sources of electrical energy generation.

Modern solar cells typically have around 15% efficiency and rising—a massive improvement compared to the 1950s, when solar-cell efficiency was around 4%.

Ongoing research by the U.S. Department of Energy’s National Renewable Energy Laboratory suggests that the use of inkjet technology in the production of thin-film and rigid, silicon-based solar cells could be extremely significant for the future.

The additive nature of inkjet technology could help streamline production and render expensive vacuum equipment—essential in other production techniques—unnecessary.

Because photovoltaics production involves the deposition of expensive materials (silver inks can cost more than $1000/kg), inkjet’s ability to drop on demand means significantly less waste and thus reduced production costs.

Resists for wet chemical etching and metallization could be inkjet deposited, which would cut material costs due to digitally controlled quantities and precise deposition.

Photovoltaics production also requires the creation of extremely fine contact lines.

This process can be performed using laser technology but can lead to damage and breakage. These pitfalls are avoided because inkjet is non-contact. Fine contact lines can be produced using screen printing, but inkjet allows conductive ink to be deposited in a finer pattern and is also significantly cheaper.

Finer lines are also preferable in terms of functionality because they leave more surface area on the panel to absorb and convert light.

Researchers, including the Oregon State University and the EU NOVA-CIGS project, have been experimenting with printing solar

cells based on a compound called chalcopyrite (CIGS), which contains copper, indium, gallium, and selenium elements. While more than 90% of solar panels are produced using silicone, CIGS will perhaps offer an economical alternative. CIGS is different from most thin film materials in that it doesn’t degrade from exposure to sunlight and is easy and cheap to produce and install.

Radio Frequency Identification (RFID) RFID is an emerging wireless technology used primarily for identifying and keeping track of items. Although uncompetitive and high component and manufacturing costs have stalled mass adoption of RFID, these hindrances are likely to become negated in the future as production processes become more effective. In terms of functionality, RFID offers several distinct advantages over barcodes. RFID uses tags that are able to read and write; barcodes are read-only and are unable to send out important information regarding the tracked items. With barcodes, every item of inventory must be scanned individually to keep figures correct—with RFID this process is automatic. It has also been reported that the advanced product tracking offered by RFID allows for greater understanding of consumer buying trends and thus gives indicators on how to manage stock effectively. Barcodes will still be the preferred technology for some applications, but it is clear that RFID will continue to expand in many areas.

Although for the most part inkjet is still an overlooked technology in the field of RFID, it has been used to deposit conductive tracks in some devices. However, the goal to lower material costs has led companies to start investigating the use of paper as a substrate for RFID/sensing applications. This will enable the use of direct printing technoljanuary/february 2012 | 17

Figure 4 A considerable amount of research is devoted to reducing the cost of producing solar cells while increasing their overall efficiency.

ogy, such as inkjet, instead of expensive and wasteful metal-etching processes. This is particularly crucial where additional efficient, low cost and rapidly deposited conductive tracks are required for devices which use sensors and batteries.

Paper also has the advantage of being perceived as a green, biodegradable substrate.

With environmental legislation continually becoming more stringent, it becomes an extra incentive for manufacturers to research this area. The current roadblock preventing paper substrates from becoming prevalent in RFID is that paper cannot survive the high sintering temperatures required for conductive inks to adhere to the substrate.

Organic light-emitting diodes OLEDs are flat-layer light-emitting devices made of a series of thin-film organic compounds positioned between two conductors.

The device emits a bright light when an electrical signal is received. OLED devices are typically 100-500 nm thick; approximately 200 times thinner than a human hair.

Because OLEDs do not require a backlight and are extremely thin, they have found special niche in the fields of displays and lighting. OLEDs can be used in flexible and transparent displays, potentially making them valuable for applications where displays are required on unusual substrates. OLEDs could be embedded in curved surfaces, windows, or car windshields more effectively than conventional displays. Another key characteristic of OLED technology is low power consumption. Currently OLEDs are primarily available as small displays on devices such as mobile phones due to manufacturing

limitations. Larger, mass-produced displays are likely to appear on the market within the next few years.

Commercially available OLEDs are currently produced using vacuum deposition, which involves heating the organic modules in a vacuum chamber until they condense as thin films onto the substrate. This method is not only expensive, but also inefficient and difficult to scale up for larger substrates.

Inkjet has been highlighted as a potential new deposition methodology that, if successful, will bring high-quality OLED displays to the market at a lower price than competing display technologies.

Instant specification moderations can be made on an inkjet production line, which means it will be possible for the same machine to switch between printing displays of different sizes with little hassle and expense.

Panasonic, in researching using inkjet to deposit organic compounds onto a polymer surface, suggests their new displays will offer a color rendering index of 95 (currently fluorescent illumination technology offers figures in the high 80s).

E textiles The term E textiles, or smart textiles, refers to fabrics with integrated electrical components to create digital capabilities such as sensing, communication, and information processing. Complex electronic networks containing devices such as pressure sensors and LEDs have already been prototyped successfully for a wide range of uses, both functional and decorative. This amalgamation of textiles and electronic technology has lead to some truly unique and potentially

18 | Industrial + Specialty Printing www.industrial-printing.net

revolutionary applications.

Wearable technology has garnered much interest in terms of personal fashion due to the limitless new options it gives us in distinguishing our identity. However, much of the impetus for innovations in the field of E textiles has come from the military, where their implementation could prove vital for the lives of soldiers on the battlefield.

One prolific area of research has been in the development of bio-monitoring textiles that track the wearer’s vital signs, such as heart rate and body temperature, and then raise alerts if they move outside of designated safe parameters. This technology would not only be greatly valuable to the military, but also in medical, sporting, and public-safety sectors. The light cotton fabric of the Sensatex’s SmartShirt, for example, is integrated with conductive fibers that acquire analog physiological signals and through a small personal controller digitize and transmit the data wirelessly to a remote source for analysis.

Another area of military research for E textiles is adaptive camouflage. It will automatically change the color of the soldier’s fatigues as he passes through different environments. Demand for the use of conductive inks in electronic products is growing. Innovations in conductive-ink technology have been particularly significant in the area of organic electronics, where printable conductors are required as a component in complete devices and displays. Ongoing developments in these areas will ultimately lead to wider adoption of industrial inkjet technology.

The author would like to thank Jack Knopfler, market researcher, Xennia Technology, Ltd., for his contributions to this article.

Tim Phillips

Xennia Technology Ltd. Tim Phillips, Ph.D., is the marketing manager at Xennia Technology, Ltd. He graduated from the University of Cambridge in 1991 with an MA Honours degree in Natural Sciences, and completed his Ph.D. in liquid crystal physics and chemistry at the University of Bristol in 1994. He has also recently completed an Executive MBA at the University of Warwick. Phillips went to work for Xennia in 2007 responsible for R&D sales and in 2010 joined the marketing team.

inkjet SOURCE

A paid advertising supplement to iSP Magazine.

For information please contact steve.duccilli@stmediagroup.com.

The DMP-2800 printer allows the deposition of fluidic materials utilizing a disposable printhead cartridge. This lab-top printer can create and define patterns over an area of about 200 x 300 mm onto substrates up to 25 mm thick with an adjustable Z height.

The temperature of the vacuum platen, which secures the substrate, is adjustable up to 60°C. A waveform editor and a drop-watcher allows manipulation of the electronic pulses to the printhead for optimization of the fluid jetting characteristics. This system enables easy printing of structures and samples for process verification and prototyping. www.dimatix.com

Industrial Inkjet XYPrint 100

The XYPrint 100 is a complete, high accuracy inkjet system designed for a wide range of materials deposition applications. The unit is a benchtop printer for process or material development and can be utilized for small scale or pilot line manufacturing using Konica Minolta printheads. The IIJ XYPrint 100 uses full production standard Konica Minolta inkjet printheads for the highest accuracy, repeatability and reliability.

The XYPrint 100 is an ideal, low cost development unit for material manufacturers, research and academia institutes and printing companies. Konica Minolta printheads are known for their high quality and ease of use. The XYPrint 100 provides a fully scalable to production development solution.

The DMP-5000 is a non-contact, fluid deposition system capable of jetting many fluids using multiple Dimatix printheads interchangeably.

It has a printable area of 500 x 500 mm with an accuracy and repeatability of ± 5 µm and ± 1 µm. A temperature controlled vacuum platen is used to register, maintain and thermally manage substrates during printing.

An integrated drop visualization system captures droplets in-flight as ejection parameters are adjusted producing a tuned printhead and fluid combination.

Electronics allow the printhead to be calibrated on a per nozzle basis compensating for channel-to-channel variability. A second camera allows substrate measurements, alignment, and observations of fluid drying behavior, with droplet measurement and placement calculations. www.dimatix.com

Based in Cambridge, United Kingdom, Xaar is a leading independent developer of core inkjet technology and a manufacturer of a range of industrial printheads, including the Xaar 1001, which incorporates Xaar’s patented TF Technology™. The first printhead designed for high productivity single-pass printing, the Xaar 1001 is opening the potential of inkjet to an ever broadening range of industrial applications including printed electronics. The company supplies a range of supporting equipment and services to help printer manufacturers and integrators, and has developed unique capabilities to help ink manufacturers to formulate fluids optimised for inkjet. www.xaar.co.uk

www.industrialij.com

january/february 2012 | 19

cover story

Revolutions in Display and Lighting Manufacturing This article discusses printing technologies for OLEDs and examines the ways in which OLEDs are transforming the way we define structure and light.

Barry Young

OLED Association

20 | Industrial + Specialty Printing www.industrial-printing.net

• Lifetimes (L70) in the range of 100,000 hours at 1000 cd/m2 and 50,000 hours at 3000 cd/m2 • A doubling of luminous efficiency using new light extraction methods • Flexible substrates with transparency at >50% • Low-cost manufacturing These gains in market acceptability and the accompanying growth projections are backed by a number of real world activities: • Samsung (SMD) produced more than 30 million smartphone OLED displays in Q3 2011, up almost 100% Q/Q. • Samsung and LG Display report avail-

ability of 55-in. AMOLED TVs in 2012, built on Gen 8.5 Fabs (2200 x 2520 mm).

• Sumitomo to open facility to make polymer material, hinting at a customer that will make 40-in. TVs on plastic.

• Japan Display buys sixth Gen Fab from Panasonic—will convert it from a-Si to p-Si and manufacture AMOLED displays.

• Osram, Panasonic, Philips, and Lumiotec announce new OLED lighting products.

• GE and Fraunhofer pursue roll-to-roll production of OLED lighting panels.

• Samsung announced the production of a flexible display for 2012.

• BOE (China) announces plans and Capex to build a sixth Gen Fab in Mongolia.

• DuPont announces joint development agreement with Korean display maker to use nozzle printing for TVs. The principle of light from OLEDs was discovered in the 1960s, but it took work by Ching Tang and Steve Van Slyke of Kodak in the late 1980s to make OLEDs function over a reasonable time. They discovered that if the light-emitting material were surrounded by injection and transport layers, the lifetime would increase. Their work to design a stack

of organic material in 1987 led to the origin of an industry. There are many stack designs, as shown in Figure 2.

The single-stack design is used for displays, while the multiple-stacked designs are used in lighting and for some TVs. The commercial production of all current OLED display and lighting products use smallmolecule material in a powder form that is deposited on a glass substrate under vacuum.

VTE is a mature technology that uses a fine metal mask (FMM) for patterning of the RGB sub-pixels for displays and layers of red, green, and blue for deposition. Herein lies the opportunity for printing, because when the light emitting material is deposited using the FMM, the material-utilization rate is 3-5%, and when the other organic material is deposited without the FMM, the material utilization is 20-25%.

Patterning requires that each color have its own source. This is the case for printing, which has been made by a number of companies and scientists: • Printing has high material utilization in the range of 75-85%.

• Printing enables fine patterning.

450% 400%

25,000 20,000 Growth

rganic light-emitting diodes (OLEDs) are a new entry in the display and lighting markets, and while production is currently limited to some form of vacuum thermal evaporation (VTE), there are several programs working on placing chemicals into solution for printing.

Printing OLEDs appears to solve many of the problems inherent in the evaporation process, including high material utilization in the range of 75-85% vs. 3-20% for evaporation; fine patterning, which is limited to 15µm for evaporation; less expensive than vacuum deposition; compatible with roll-toroll manufacturing and very thin substrates (<100 µm); expanded at very low capital costs by increasing width of the substrate or by speeding up the roll; conductive polymers used to print organic TFTs; operation at atmosphere and at low temperatures; enables the use of plastic, creating new form factors.

Printing is faster, more efficient, scalable, and lower cost than VTE. The opportunity for printing OLEDs is substantial because OLED technology used in lighting and displays is today a $4 billion market and is expected to grow to more than $25 billion by 2017, as depicted in Figure 1.

The CAGR for OLED revenue between 2011 and 2017 is forecasted to be 37%. This growth is being driven by the performance improvements that OLEDs have in the display and lighting industries, as summarized in Table 1.

Moreover, the future is even more promising as the technology matures and OLEDs reach new levels of performance driven by the advances in organic material, new stack designs, and the maturation of the manufacturing process:

US$ (M)

O

15,000 10,000 5,000 0

2009 2010

2011

2012

2013

2014

2015 2016 2017

BLUE EML R G EML HTL

HIL

ITO Single Stack • Only 6-7 Organic Layers • Simpler to manufacture • E xcellent color stability with Aging

Figure 2 OLED-stack designs

BL

BL

R G EML HIL BL

HIL

50% 0%

Cathode ETL

Cathode ETL BL

200% 150% 100%

Lighting TVs Small/Medium Displays Y/Y Growth

Figure 1 Predicted growth in OLED applications

Cathode ETL

350% 300% 250%

HTL

CGL ETL

BLUE EML HTL

ITO

BLUE EML HTL HIL BL

R G EML CGL ETL

BLUE EML

R G EML

HIL

HTL

ITO

Stacked • Vertically stacking multiple OLED units • Less current at same luminance • Increases luminous efficiency • reduces resistive power losses • reduces heat generation • Longer lifetime at same luminance january/february 2012 | 21

LCD

High contrast

Diffuse lighting source

Fast response time

Thin form factor

Thin form factor

Unique configurations

Accurate colors

Robust

Low power consumption

Transparent and flexible

Wide viewing angle

Suitable for roll-to-roll manufacturing

Scanning Line

Scanning Line Power Source Line

No glare

Switching TFT

LCD

Data Line

Lighting Characteristics

Blackest blacks

Data Line

Display Characteristics

OLED

Switching TFT

OLED

Transparent and flexible Table 1 OLED performance in displays and lighting

• Printing equipment is less expensive than vacuum deposition (VTE).

• Printing is compatible with roll-to-roll manufacturing and very thin substrates (<100 µm).

• Roll-to-roll processes can be expanded at very low capital costs by increasing width of the substrate or by speeding up the roll.

• OLEDs in solution can be printed, and new approaches to organic transistors allow printing.

• Printing can be performed at atmosphere and at low temperatures.

These arguments work perfectly for printing, but displays have an additional component—the active matrix, which is made using thin film lithography. Active matrixes are required for OLED displays with more than 100 rows—and that, in effect, applies to 99% of the display industry. Thin-film processing is similar to lithography used by semiconductors, except that a 12-in. wafer is replaced by a glass as large as 3 m x 3 m. The OLED active-matrix design is based on a two thin-film transistor (TFT) and one capacitor structure, as shown in Figure 3, and is compared to an LCD design, which is much simpler. The major difference is the existence of the driving TFT for OLEDs, which has a very high duty cycle compared to the switching TFT, which has a low duty cycle. When the TFT is on for a long time, it generates heat and, in some materials such as a-Si, the threshold voltage changes, which creates a non-uniform image.

OLEDs also use higher currents, leading to the need for active material.

Another challenge targeted by the printing industry is to use conductive polymers for organic TFTs (OTFTs). OTFTs have been successfully implemented to print active matrixes for electrophoretic displays used in e-books. Figure 4 shows a schematic of an

Figure 3 LCD vs. active-matrix OLED

organic TFT and the process needed for print printing. The issues for OTFTs include: • Mobility: OLEDs use p-Si at 50 to 100 cm2/Vsec and are also being tested with IGZO at 15-20 cm2/vsec. OTFTs have mobilities of <2 cm2/vsec. Because OLEDs operate at large currents, the OTFTs could be too large for the required pixel densities.

• Reliability: The driving TFT would be a challenge for organic material.

Printed OTFTs have been used by Plastic Logic to drive an electrophoretic display, but the uniformity, mobility, and reliability were quite relaxed when compared to the OLED requirements. Printing OLEDs is supported by a well-defined OLED-manufacturing process. The natural state of polymer (fluorescent) material is in solution, and DuPont and Universal Display recently developed phosphorescent material in solution. Prototype printing tools have been built by a number of companies. Much has been written, in this magazine an other sources, about how OLEDs will be printed in the future.

The challenge of printing OLEDs Three printing approaches have been practiced for the deposition and patterning steps.

Inkjet and nozzle printing can be used to make TVs, and screen printing can be used to make lights, but there is no printing technology ready for displays with 300 pixels/in. (ppi), required in smartphones, tablets, and comparable applications.

Inkjet printing is a well-understood process that is used in LCD production for one-drop fill of liquid-crystal material and for color filters. While work was started by CDT, now Ulvac and Epson, there are no commercial uses of inkjet printers in OLEDs. The pixel-pitch requirement is less than 10 μm. Inkjet printing is probably limited to

22 | Industrial + Specialty Printing www.industrial-printing.net

resolutions of 200 ppi with acceptable yields, which does not meet all the smart phone specs of >300 ppi. Therefore, inkjet printing is seen as a large-substrate technology and particularly attractive for TV manufacture at Gen 8 and even higher, where pixel densities are ~100 ppi. A number of issues have been resolved over the past 10 years, including: • Capability of printheads to support lowvolume droplet delivery (<10 pl) • The use of massive granite stages to stabilize printing platforms and minimize the deviation of the droplet relative to its desired placement point • Design of the frame and the printhead unit to ensure minimal torque • Operation at several meters per minute as required for an acceptable TACT • Pre-printing formation of a well structure into which the inkjet will focus its droplets. The well is formed by using a black matrix and a traditional photolithographic process on top of the driving TFT array and the exposed ITO, which forms the anode of the pixel cell. Solutions adopted include mixing a surface-segregating, hydrophobic material in part of the black matrix and actually constructing a dual-bank structure with a hydrophobic and a hydrophilic section.

• While CDT reports that spin-coated lifetimes and those from printed structures are now essentially equivalent purveyors of “solution-processable OLED materials,” some are skeptical that actual lifetimes and efficiencies may fall far short of published data.

• Proprietary work has resolved the short- and long-range uniformity problem, and short-range brightness variations are now within the required ± 3%.

• Uneven pixel-to-pixel brightness caused by differences in the volume of OLED material has been resolved by presetting the

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packaging TFT Array

Fi gure 5 An example of the ways in which OLEDs define ceilings, space, and building architecture (source: KVA)

volume delivered by each nozzle.

To meet the throughput requirements, all three colors must be printed one pass.

The other layers—the hole-transport layer and the electron-blocking layer—must also be printed. The challenging engineering and software feat has delayed the introduction of inkjet printing for OLED TV displays.

Solution-processable blue material still falls short of the performance required for TV service with an acceptable lifetime at a color point of CIEy = 0.08. Solution-processed OLEDs, be they polymer OLEDs from Sumitomo Chemical or solution-processed small molecules for UDC or Merck or others, will surely come of age by 2015 if some critical issues are resolved.

Nozzle printing, developed by DuPont and Dai Nippon Screen, is targeted for displays and is designed to solve the problems of low material utilization and scalability, because it does not use a FMM. Samsung is testing the process. Nozzle printing currently has a minimum pixel pitch of 40 µm and is not suitable for the high-pixel-density smartphone market. In addition, performance and lifetimes of the material are substantially less than the phosphorescent material used in commercial displays. The yields, uniformity, and stability have yet to be tested by independent panel makers.

Screen printing, developed more than 1000 years ago, has recently been applied to the production of wafer-based solar photovoltaic (PV) cells; the mesh and buses of silver are printed on the front; the buses of silver are printed on the back. Subsequently, aluminum paste is dispensed over the whole surface of the back for passivation and surface reflection. The process must have a high yield and controlled print thickness, indicating

Organic Semiconductor: π-conjugated material Formation of thin film (coating, printing) Molecular ordering for improved mobility Patterning S/D electrode: thin film/material patterning (Au, Ni, Pd, SOM, conducting polymer) Insulators: thin film/material design (Organic Polymer, inorganic materials) Subsrate: PET, PC, PAR Gate Metal: thin film/patterning

Metal (AI): sputter/lithography

Conducting polymer: inkjet printing

Figure 4 Schematic of an organic TFT and the process needed for print printing

that the technique might useful for OLED displays and lighting, where the organic layers range from 200 Å to more than 500 Å.

Substrates and encapsulation OLED displays and lighting use glass as the substrate and as a cover. Glass is very flat, has a relatively high transition temperature (Tg), high permeability, and is relatively low cost: ~ $50/m2. Organic material is susceptible to destruction by moisture and certain gases. The high permeability of glass creates a very protective environment, while plastic is just the opposite. It is not flat, has a low Tg, low permeability, and is relatively expensive.

To use a plastic substrate, a barrier layer is needed consisting of layers of inorganic and organic material. The barrier layer can also be used to encapsulate a device by depositing it directly onto the OLED stack. The issue with barrier layers is the cost and the time to deposit the material.

Roll-to-roll manufacturing of OLEDs A novel approach has been developed for highly efficient small-molecule-OLED stack deposition on flexible webs in a roll-to-roll process as a major cost reduction step. The use of a flexible substrate opens up new degrees of freedom in system design and could be competitive for general signage and lighting applications. Metal foils or plastic used as a substrate for the deposition of organic light-emitting diodes with the doped charge transport layers, the so-called p-i-n OLED technology, will allow a direct OLED deposition on the substrate with low operating voltage. The Center of Organic Materials and Electronic Devices Dresden (COMEDD) of Fraunhofer IPMS and GE Plastics are each experimenting with roll-to-roll lines for research and development for OLED lighting.

24 | Industrial + Specialty Printing www.industrial-printing.net

The roll-to-roll line consists of a vacuum coater for small-molecule depositions, a roll-to-roll encapsulation unit under inert atmosphere, and an optical inspection system.

New opportunities enabled by printing The largest opportunity for printing OLEDs is the lighting application because an active matrix is not required and the potential for roll-to-roll manufacturing allows the production of virtually unlimited size and growth.

DuPont/Dai Nippon Screen also has an opportunity for printing TVs, but their major licensee Samsung is well on its way to use a form of vacuum thermal evaporation to produce the first OLED TVs, while LG seems to have been shut out of the technology.

Panel manufacturers are seeking a solution to patterning OLED material, and if inkjet printing is ready in 2015, it may well be adopted. The use of roll-to-roll and plastic substrates could enable a whole new range of products. Figure 5 shows how flexible and transparent OLEDs could be used to create a revolution in the way we create define ceilings, space, and building architecture. There are significant challenges toward getting to printed OLEDs, but it is likely that these types of products will appear on the market after 2015—and the world of printing and OLEDs will never be the same.

Barry Young

OLED Association Barry Young is managing director of the OLED Association. He also serves as the CEO of YMR, characterizing the 100+ LED producers in terms of reactors, wafers, die capacity, yielded die and die revenue. He has a business degree from CUNY and has performed graduate work at George Washington University.

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FEATURE STORY Gail Flower

26 | INDUSTRIAL + SPECIALTY PRINTING

Photos courtesy of Paul von Schwartzenfeld with permission from IDTechEx from the Printed Electronics & Photovoltaics USA 2011 show floor.

N

o one can really predict the future.

However, to get a well-rounded sampling of where functional and decorative printing is headed, we asked a few of those attending the 2011 SGIA Expo in New Orleans, LA, and those attending IDTechEx’s Printed Electronics & Photovoltaics USA conference in Santa Clara, CA, what they projected. And this industry is chockablock with opinions. The following comments resulted from their responses and our observations.

SLOWER THAN EXPECTED “Functional transistor printing is still alive and well, but I think the general consensus is that things have taken longer to mature than expected, as this area is requiring not only new materials but also new printing equipment and procedures in an industry (semiconductor) that has historically used very different methods,” says Brendan Florez.

Some companies, like Thin Film Electronics, have demonstrated fully printed, addressable memories, but these tend to be lab-scale, and it will take some time to scale up to acceptable yields using largescale manufacturing processes. With that in mind, there are other functional printing technologies that are more mature and represent very promising technologies (printed electroluminescence, printed conductors, and printed photovoltaics). “I think we’ll continue to see functional printing as something becoming more prevalent with time, but time is still the key,” Florez notes.

Though there’s no unifying market force; the “printed electronics industry is heading toward, finding out about, and serving

markets as they develop,” says Wolfgang Mildner. As applications and markets mature, we will see printing methods adapting to the latest needs and businesses growing accordingly, he claims. Looking at the variety of tradeshows focusing on printed electronics points toward early interest and investment in this type of printing.

“The pressure-sensitive-labeling industry is still strong, however—our growth has slowed primarily based on the economy,” says John Bennett. When consumers buy less, the demand for labels slacks. “The only real area in our industry that benefits from a slow economy is where labels and marketing are used to capture the consumers’ attention,” he adds.

Brand markets and grocery and mass merchandisers tend to change price more frequently in this type of economy; therefore, there are more demands for media that can present these changes to the consumer.

“One challenge will be raw-material supply in acrylic monomers and where the large vendors, such as Dow and BASF, determine they prefer to sell. We won’t be able to avoid price inflation, and this will likely make it a challenging year with regard to holding down costs,” Bennett explains.

If you look at the growth of trade shows that feature printed electronics, membrane switches, specialty printing, and flexible substrates, most associations jumped into the foray with independent trade shows, then absorbed this topic back into their main shows when growth in the area was slower than expected. Both the IPC and SGIA had independent shows for functional printed electronics and then absorbed the topic as part of their main conferences in

the future as the economy remains tentative. However, the IDTechEx conference in the U.S. grew, expanding the coverage of the show to also showcase photovoltaics.

Shorter runs Most interviewees agreed that shorter runs with variable printing lots and faster turnaround times can be expected for functional printing.

“New opportunities arise for all in an industry that rapidly progresses and demands higher quality at shorter runs,” says Eric Matsumoto.

More industrial accounts are looking for smaller quantities (less inventory commitment) with shorter lead times (and, of course, better pricing), adds printer Dolf Kahle. This happens with any market: OEM, P-O-P, and fleet. He sees the OEM business requesting more direct printing on their products. The limitations tend to be the height of the Z-plane and the flatness of the printed surface. Print projects range from one piece to 600,000 pieces per year, he says.

Mike Bacon agrees that shorter runs and shorter lead times require flexible, agile printing and converting equipment. Flexo and screen-printing processes for varied applications and longer job runs fit some applications; however, digital printing and laser cutting inline fit the faster changeover times, reduction of operators, and design times. Screen-printing systems in the field producing RFID labels and conductive ink products are also benefiting from inline laser systems, he says.

“Without reservation, we see the industry heading to faster response times and shorter production runs,” says Jim Lambert.

“Customization, localization and the ability to change labels dynamically is creating a whole new market for label printing,” Companies that would traditionally run hundreds of thousands of labels are now being asked to run 20,000-50,000 labels.

These types of reductions and the ability to avoid printing plates and cutting dies have made digital printing and laser cutting a popular choice.

Software helps optimize efficiencies and control automated functions for shorter runs. “Runs are short and the applications are more creative and sophisticated,” says Danielle Mattiussi. From a software perspective of the market, this means diverse

files and complex graphics that need to be prepared for print extremely efficiently to keep the presses at maximum capacity.

Although run lengths are declining, trends such as variable-data printing, versioning, QR codes, and new substrate capabilities are creating excitement in the wide-format-graphics market, according to David Murphy. The wide-format-graphics industry is rapidly moving to digital printing solutions that enable personalized messages and variable-data printing for deeper engagement with audiences by the brand owner, adds Harel Ifhar.

Herb Gieseler sees lots of trends including shorter runs. “First off is the continued reduction in the labor component though automation—not only on large-run products, but also even on low- to mediumvolume type products. Everything from new manufacturing methods, such as cellular manufacturing, digital printing, and digital fabrication, is covered. As the speed and accuracy increase with these new processes, so will the inherent benefits of minimal set ups. With this occurring more and more, it actually begins to reduce the chasm in manufacturing costs between East and West. I see a shift in the future back to more domestic production as these improvements are made as opposed to outsourcing or off-shore manufacturing. I also believer there will be more of a move toward valueadded systems.”

Instead of supplying a switch to add at the end of the project, there will be more of a movement toward complete integrated systems. Finally, with the economy headed in the current direction, we will continue to see the consolidation of companies and assets, Gieseler claims.

Hiroshi Ono agrees that run sizes are getting ever shorter and turnaround times faster—and this will continue. The market for short-run production and even personalized products continues to grow across every facet of the printing industry. He sees UV-LED technology usage as an enabler for printing on unconventional substrates and printing directly on products as a trend. “To stay competitive in this environment, screen, industrial, and specialty printers need to invest in nimble digital devices,” he says.

PANEL OF RESPONDENTS FLEXcon, Spencer, MA

John Bennett, VP Product Identification

Fujifilm Dimatix, Santa Clara, CA

Chuck Griggs, VP Applications Engineering

GMG Americas, Hingham, MA Juergen Roesch, Manager, Business Development

Henkel Electronic Materials, LLC Douglass Dixon, Marketing Communications Director

Hewlett-Packard, Graphics Solutions, San Diego, CA David Murphy, Director of Marketing

Hewlett-Packard, Scitex Industrial Printing Solutions, Netanya, Israel Harel Ifhar, Marketing Manager

Hop Industries, Lyndhurst, NJ

Eric Matsumoto, Account Representative

Imagetek Consulting Int’l.

Mike Young, Consultant

INX International, Digital Division, San Leandro, CA Jim Lambert, VP and General Manager

InfoTrends, Rockville, MD Tim Greene, Director

MACtac Graphic Roll Label, Stow, OH Kim Hensley, Product Manager

ONYX Graphics, Inc., Salt Lake City, UT

Danielle Mattiussi, Director, Product Marketing

PANNAM Imaging, Cleveland, OH

Herb Gieseler, Senior Technology Engineer

Polyera Corp., Skokie, IL

Brendan Florez, Assistant General Manager

PolyIC GmbH and Co. KG, Fuerth, Germany

Wolfgang Mildner, Managing Director

Roland DGA Corp., Irvine, CA

Hiroshi Ono, Group Product Manager

Spartanics, Rolling Meadows, IL Mike Bacon, VP Sales and Marketing

Sun Chemical, Parsippany, NJ Curt Baskin, Marketing Manager

Visual Marking Systems, Inc., Twinsburg, OH Dolf Kahle, CEO

Z Corporation, Burlington, MA Joe Titlow, VP Product Management

Sustainability more important Many of the master classes at Printed january/february 2012 | 27

Photos courtesy of Paul von Schwartzenfeld with permission from IDTechEx from the Printed Electronics & Photovoltaics USA 2011 show floor.

Electronics & PV USA stressed sustainability. The T-INK review of product applications, for example, talked about Smart Plastic in an in-mold format. The technology integrates a 3D, smart plastic part in a thin format. It integrates through using the right chemistries, many different printing systems, films, resins, and electronics to create smart plastics in cars, consumer products, and white goods.

The ink is touch- and motion-activated in printed applications and replaces switches, wires, buttons speakers, lights, and sensors.

Why would you want to integrate flexible, conductive inks into standard presses at high-speed production rates onto most substrates (paper, textile, vinyl, metal or glass) using screen printing, offset, gravure, flexo or stamping? A cost savings and functional product results—heated strollers, coats, workwear, stadium seats, and sportswear). The objective is to make a button-free, clean, in-mold surface from low-cost, eco-friendly products. Surfaces are sealed and can be wiped clean, and printing is inside all of the molded parts.

The chemistries are designed for a low-carbon footprint, using less product, and all surfaces are sealed through in-mold technology.

New opportunities In 3D printing of prototypes, Joe Titlow expects to see more accessible products as price points drop and systems become easier to use. Companies that print industrial products are now investing in 3D printing to show what final products will look like long before they’re printed.

Wim Zoomer says that many different printing styles will be used to produce a variety of industrial products. Some techniques will slowly replace screen-printing technology. Inks and new application technologies will be compatible to meet the requirements of miniaturization in specially printed electronic. Lines and spaces must print finer than 40 μm for short production runs and for prototyping. However, screen printing applied in industrial applications maintains an acquired position when long production runs are required, such as 70- to 80-μm lines and spaces for manufacturing solar cells.

Curt Baskin sees opportunities in printing directly on plastic and glass containers where chemical and product resistance properties may be needed in the ink system. In electronic materials, silvers and other dielectric inks will remain printed via screen printing in the near future. Printing on plastic cards will grow, making use of heavy metallic colors as smart-card printing with embedded intelligence grows.

28 | Industrial + Specialty Printing www.industrial-printing.net

Though printing in traditional ways may be decreasing, there are new applications, such as printed electronics, photovoltaics, ceramics, and textile products, that are increasing for industrial printing, says Chuck Griggs.

In agreement, Tim Green adds that there are tremendous innovations happening all the time in conductive inks, material deposition, printhead technologies, and substrates that enable digital printing systems, tools, and technologies to be applied to the wide range of applications that fall under the specialty printing headings.

PE will grow despite the economy “With the only relative certainty about 2012 being market uncertainty, the notion that there is anything remotely close to a sure thing in the electronics industry might give some people pause,” says Douglass Dixon.

But, here’s one prediction he is willing to make: For 2012 and the years soon thereafter, the printed-electronics sector will continue to grow. The rate of growth might be debatable, but the fact that printed-electronics processes are finding their way into increasingly more applications is undisputable. The need for ever more efficient, high-throughput, low-cost, flexible-form-factor applications has driven development of printed-electronics materials and processes, and they are now enabling everything from touchscreens and RFID antennae to medical sensors and flexible circuits.

That’s welcome news for companies that make materials for the industry, such as Henkel. Understanding the formulation complexities and the frequent interdependence and compatibility requirements of various conductive inks and adhesives is important in advancing printed electronics for the modern age. And, while printed-electronics techniques have been in existence for more than 20 years, Dixon firmly believes the possibilities for these applications are just now really coming into their own.

Cooperative partnerships Partnerships between companies to combine the expertise of each to create an innovative, new product in the field of functional printing can be seen as a growing trend to help bring practical ideas to market.

For instance, Kodak and Heraeus announced a development of transparent films that can be patterned easily to provide a cost-effective alternative to indium-tin-oxide (ITO) films. They demonstrated patterning Kodak HCF-225 Film/ESTAR Base using Heraeus technologies such as Clevios Etch and masking

polymer Clevios SET G to yield completely invisible conductive patterns for a variety of touchscreen applications at IDTechEx’s Printed Electronics & Photovoltaics USA conference.

In the Heraeus booth, blinking LED lights with no visible connections in the clear substrate provided one demonstration.

For another, Mark Juba, general manager, Industrial Films Group at Eastman Kodak Company, and Brian Johnston, director, Kodak External Alliances Venture Capital University Investments, showed us a 14-in. touchscreen panel that was fabricated using Kodak HCF-225 Film/ESTAR Base and the Heraeus Clevios PEDOT:PSS coating with a surface resistivity of 225 ohms/sq.

“We used conventional printing processes, including a UV-cured and heat-processed inks,” Juba says.

For demonstration purposes, they selected a common touchscreen operation of selecting merchandise, then adding up the sale automatically using their new transparent touchscreen materials. Juba says the technology’s development is all about friendships between cohorts in related fields—and it could be lucrative for both companies.

At the PE conference, SouthWest Nano Technologies exhibited carbon-nanotube applications based on V2V Ink technology developed by alliance partner Chasm Technologies, Inc. for printed electronics and touchscreens. They demonstrated various applications that were made using flexo, gravure, and screen printing. SWeNT tailored the carbon-nanotube materials for applications using its CoMoCAT process that’s designed to help customers print large-area, low-cost devices for a wide range of applications, including energy-efficient lighting, affordable photovoltaics, improved energy storage, and printed electronics.

In an earlier announcement before the PE and PV USA show, the FlexTech Alliance focused on developing the electronicdisplay and flexible, printed-electronics industry-supply chains, talked about the completion of a multi-phase project with Henkel Corporation and the Flexible Display Center at Arizona State University. The object of the project was to develop debondable laminating adhesives to enable activematrix-backplane fabrication of flexible substrates. The result is a process that can use the manufacturing infrastructure already in place for LCD displays to fabricate

flexible, large-area displays or novel-formfactor applications with minimum process modification or capital investment.

Conclusions Though it has taken a while to mainstream many of the latest examples of functional printing, the market continues to grow at a healthy pace. The biggest roadblocks seem to be in getting familiar with new materials,

such as nanoconductive inks, and with finding the financial support for initial R&D. At the latest shows in the industry, SGIA 2011 and IDTechEx PE & PV USA, partnerships abound to get around many barriers. And printing methods include whatever makes sense with using these materials: screen printing, in-mold, gravure, 3D, inkjet, flexo, and others. From year to year, you can see the industry progress at a healthy clip.

january/february 2012 | 29

printed electronics

A Guide to High-Performance Conductive Ink Chris Wargo

PChem Associates

What is conductive ink? Before answering that question, it might be interesting to present what conductive ink isn’t. Conductive ink isn’t sexy. It doesn’t get much coverage in the mainstream science media.

Conductive ink isn’t revolutionary or recent.

The first patents for conductive inks were issued more than100 years ago. Conductive ink isn’t high science. No one will ever win a Nobel Prize for making a better conductive ink. But what conductive ink is tends to be more important than what it isn’t. Conductive ink is the foundation on which the emerging printed-electronics industry will be built; therefore, it is important for anyone in the industry (or considering entering the industry) to understand the pros and cons of different types of conductive inks.

Selecting a conductive ink is sometimes fairly straightforward. If a printer with a flatbed screen-printing press wishes to enter the printed-electronics market, then the choices are limited by the available screen inks on the market. If a researcher is interested in depositing very thin conductors with frequently changing designs, then an inkjet ink might be the only option.

However, it’s important even for users with seemingly simple needs to understand the possibilities outside their application to address business threats or future changes in manufacturing needs.

When selecting an ink is product driven and not process driven, the degrees of freedom are greater, and a deeper understanding of all the available options on the market becomes more important. Such a

broad understanding is particularly important to a design engineer or a manufacturer who is building a new production line. It is imperative that these users understand the strengths and limits of different ink technologies to design and deliver the best product and process for the lowest manufacturing cost.

There is a wide array of conductive inks on the market, and it isn’t possible to dig deeply into the details of every product class. Instead, this article focuses only on

to fill a cost/performance gap in between silver and carbon, but they can’t approach the conductivity of silver inks. Copper inks show great promise in long-term material cost reduction, but as of now they require expensive specialty curing systems due to the high oxidation potential of copper (nonconductive oxides).

The silver inks that will be discussed here fall into two general classes, polymer thick film (PTF) and nano silver inks. The nano silver inks are further divided into

Today, screen printing is by far the most common method for printing conductive ink. Many flatbed printing lines are meeting today’s demand for printed electronics, and rotary screen offers an increased throughput for a screen-printable conductor. high-conductivity inks suited for conventional manufacturing techniques. As such, all the inks discussed will be silver based.

Silver is used almost exclusively in highperformance conductive inks due to its physical and chemical properties—intrinsic conductivity, sintering temperature, oxidation behavior, etc.

Carbon inks are fairly common in lowperformance devices such as toys, but they are unsuitable for what is generally considered to be part of the emerging printed electronics market. Graphene inks promise

30 | Industrial + Specialty Printing www.industrial-printing.net

aqueous and organic classes. The properties of each of these ink classes, including some deposition technologies, are described below.

Characteristics of silver-based inks Table 1 summarizes the characteristics of the types of silver-based inks currently marketed to printed electronics. PTF inks are currently the most common types of conductive inks on the market. They consist of conductive particles dispersed in

150°C

Print speed The print speed of a printed conductor is determined not only by the speed of the printing operation, but also by the material’s curing requirements and available heating equipment on the press. Whether printing or curing is the rate-determining step depends on both the type of printing and the type of conductor being printed.

Press speed is often the limiting factor.

However, this is not to suggest that different materials will not allow different relative print speeds.

Curing is typically the rate-determining step for high-speed printing. Curing of many conductive inks requires more heat for longer periods of time. Figure 1 shows curing times for different classes of conductive inks taken from various manufacturer data sheets. While it is theoretically possible to make any ink cure on any press by extending the length of the curing oven, practical equipment installations limit cure time to minutes for screen printing and seconds for flexo.

At higher speeds, the heat-transfer mechanism also becomes important.

Infrared or conductive heating can lead to much faster cures than convective heating.

Simply selecting a high-speed printing process is not sufficient to ensure fast production throughput. For example, highspeed roll-to-roll inkjet processes have been developed, but production rates are still limited by the silver nano-inkjet inks that require minutes to cure in conventional ovens. The maximum print speed achieved for conductors known to the author has been 660 ft/min using aqueous nano-flexo inks in a 55-ft convective/conductive drying tunnel.

PTF Inks

140

Resistivity (µohm-cm)

a non-conductive resin. Nano-inkjet inks consist of silver nanoparticles—particles smaller than 100 nm—stabilized and dispersed in an organic (solvent) medium.

Some of the properties of this ink are also relevant to non-inkjet formulations of organically dispersed nanosilver, but such formulations are less common than the inkjet versions at this time. Aqueous nanosilver formulations are similar to the solvent-based nanosilver, but the chemistry of the aqueous system imparts many different properties than the solvent systems.

120 140 100 80

InkjeT Nano

60 40

Aqueous Nano

20

0.1

1

10

100

1000

10000

Time(s) Figure 1 Cure rates of different types of silver-based conductive inks

Characteristic

Print Speed Performance Resolution Print Thickness Roughness Liquid Medium Ease of Use Scalability Price Cost per device

PTF Screen ink Slow Good Good Very Thick Rough Solvent Easy Good Low Medium

PTF Flexo Ink Medium Good Very Good Thick Rough Solvent Easy Excellent Low Medium

Nano inkjet Slow Excellent Excellent Very Thin Smooth Solvent Easy Poor Very High High

Aqueous Nano Flexo Fast Excellent Excellent Very Thin Smooth Aqueous Moderate Excellent High Low

Aqueous Nano Screen Medium Excellent Good Thin Smooth Aqueous Moderate Good High Low

Table 1 Summary of the characteristics of silver-based inks

Performance The performance of a conductive ink is based mostly on an intensive property of a material known as conductivity. Intuitively, we know that metals are more electrically conductive than carbon, which is more conductive than wood, which is more conductive than glass, etc. There is a similar hierarchy among metals as well.

Silver is more conductive than copper, which is more conductive than gold, which is more conductive than iron, etc. Most high-performance conductive inks use silver for its high conductivity and its low propensity to form non-conductive oxides like copper does. However, not all silver inks are created equal. PTF inks rely on polymeric binders to hold the silver flakes or particles together. These binders tend to coat the flakes, forming a resistive barrier

in between each of the conductive silver particles.

Most silver nano-ink undergoes a process known as sintering. Due to the high surface-area-to-volume ratio of the silver nanoparticles, the particles can fuse together at temperatures much lower than the melting point of the bulk metal. This process results in a continuous electrical pathway throughout the cured conductor.

However, because of voids and formulation additives, no silver nano-ink can reach the performance of bulk silver after being cured at temperatures below the melting point.

Typically, PTF inks are 15 to 30 times more resistive than bulk silver, while silver nano-inks are two to six times more resistive. Because of the better performance of silver nano-inks, significantly less ink can january/february 2012 | 31

Property

PTF screen ink

Aqueous Nano Screen

Thickness, microns

8.1

1.6

Ra, microns

1.35

0.11

Rz, microns

20.2

1.26

Table 2 Typical thickness and roughness measurements for PTF and nano screen inks

be used to achieve equivalent electrical properties. Although all silver nano-inks cure to similar performance ranges, they do so at different rates as noted in the previous section. This is because without some form of stabilization, the sintering process would be spontaneous at room temperature and the nanoparticles would agglomerate in the ink container.

Silver nanoparticles dispersed in an aqueous medium tend to have a slightly lower destabilization threshold. This allows the aqueous inks to cure faster than similarly sized nanoparticles stabilized in an organic medium, while still maintaining acceptable shelf life characteristics.

As a result of the faster curing kinetics, aqueous nano-inks can be better suited to high speed printing processes than other conductive inks.

Print thickness The thickness of a printed conductor is determined by several factors. The print method, particle size, ink rheology, and solids loading all determine the resulting dry-film thickness (DFT) of the print after drying/curing. The thickness of PTF inks tends to be much greater than that of nanoparticle inks deposited with equivalent printing conditions. This is the result of two factors: solids loading and particle size.

In general, PTF inks require a greater solids loading than nano-inks. This is because the ratio of conductive particle to binder must remain high for the cured film to maintain conductivity. There are also rheological issues that occur when diluting PTF inks with volatile solvents which also cause the inks to suffer in terms of their

Print process Devices/hr Print hours required (incl. setup/cleanup) Equipment cost/hr Total equipment run cost Cured print thickness (microns) Ink cost/kg Cost/device Ink required, kg Total ink cost Total manufacturing cost

PTF Screen (sheet) 140,400 8.12 $200 $1,624 9.5 $1,000 $0.011 10.83 $10,827 $12,451

Aqueous Nano Flexo 1,404,000 2.71 $500 $1,355 1.0 $2,400 $0.007 2.74 $6,574 $7,929

Table 3 Cost breakdown for PTF screen printing vs. aqueous nano flexo printing (at $43.40/troy oz silver pricing)

electrical properties if diluted too much.

Particle size is also a limiting factor for minimum DFT. To be conductive, a flakebased ink must maintain several layers of flakes to ensure a properly formed conductive pathway. With flake thickness on the order of 1 μm, it becomes impossible to achieve a printed conductor less than a few microns thick.

In contrast, nanoparticle inks suffer from the inability to deposit very thick films. Because of the small particle size and lower solids loading required to maintain stable suspensions with a printable rheology, nanoparticle inks have difficulty depositing cured films more than 1 μm with flexography or 5 μm thick with screen printing. If the conductor interfaces with low-impedance circuitry requiring very low conductor resistances, then PTF is the better suited material because it can deliver a lower sheet resistance resulting from extremely thick laydowns. If thickness/ resistance requirements are less critical, then nanoparticle inks can be used to print thinner traces that still meet the design specifications while saving material costs.

Resolution The resolution of a print (fineness of features) is determined by both the ink and the print process. In general, flexo is capable of producing finer features than screen printing using typical equipment.

Typical line-width limits for screen printing are 3-4 mils (75-100 μm), while flexography can achieve lines as narrow as 25 μm repeatably with conventional printing plates.

However, at this fine resolution, particles size comes into play. PTF inks with typical

32 | Industrial + Specialty Printing www.industrial-printing.net

particle sizes of 5-15 μm are less suited to print from 10-μm-wide plate surfaces than nano-inks with 20-nm particle sizes.

Roughness The roughness of a print may or may not be of critical importance, depending on the intended application (Table 2). Applications involving stacked constructions often require the use of dielectric layers or insulators in between functional materials. Any high degree of roughness or intermittent large peaks can cause shorts though the dielectric into another layer of conductive or functional ink.

Roughness can be characterized in multiple ways, but two of the most common are Ra and Rz. Ra is the arithmetic average roughness of the conductor. It is calculated by determining the average deviation from the average value of the film height. In simple terms, it’s how unflat the surface is.

Ra makes no distinction to the wavelength of the roughness, however, so it does not distinguish between long rolling hills and a field of boulders and craters.

Rz describes the maximum peak height of a measured sample. High Rz values often indicate a spike in the printed surface, such as a large protruding flake or a particle agglomerate. High Rz values often indicate a high propensity to short through a subsequent dielectric layer. Ra and Rz measurements must be taken carefully to be meaningful. The measurements should be taken over locally flat areas to avoid the rolling-hills effect. The goal of the measurements is to look for short wavelength roughness and spikes which would short through a dielectric layer.

It is perfectly reasonable to assume that a short run on an in-house flatbed screen press with a PTF ink can be more cost effective than starting up a new process with a new nano ink on a contracted flexo press requiring oven upgrades.

Liquid medium Due to formulation and stabilization requirements, the majority of conductive inks on the market today are still solvent based.

In the case of PTF based inks, solvent systems are required to solvate the resins and binders in the inks. As with graphics inks, non-polar systems give a formulator more degrees of freedom with their formulations.

This often results in an ink with better print densities, press life, and flow properties. The tradeoff for this more agreeable ink lies in the environmental impacts associated with the VOCs in the ink.

Depending on local regulations and manufacturer’s policies, scrubbers or incinerators may need to be installed on a press in order to run many PTF inks.

To get around this issue, UV PTF inks have been developed, at a cost in terms of performance. Because there are no volatiles in the UV ink, more resin is generally left behind in the cured ink compared to a solvent based PTF. This additional resin is non-conductive, and decreases the effective conductivity of the cured ink.

Most silver nano-based inks are formulated in a solvent medium as well. This is because the most common stabilization method for silver nanoparticles is steric stabilization, where long-chain hydrophobes are attached to the primary particles to prevent premature agglomeration. The stabilization method for aqueous nano-inks is different, however, with a more complex surfactant chemistry stabilizing the particles. Like aqueous graphics inks, aqueous nano-inks contain minimal amounts of VOCs. The tradeoffs for the low VOC content are similar to what is experienced with aqueous graphics inks. In facilities without VOC concerns, solvent-based inks may be more desirable, depending on other production, cost, and performance criteria.

Ease of use Most printers who have used both solventbased and aqueous-based inks will attest to

an easier process when using the solventbased inks. The same is true for conductive inks. This is not to imply that aqueousbased conductive inks are unreasonably difficult to use, but rather they will require more care and maintenance during their use.

Aqueous inks have at least two more properties that require monitoring/controlling than solvent based inks: ambient humidity and ink pH. In a very dry environment, the solids concentration of an aqueous conductive ink can drift upward due to evaporation. Over time, this can influence the print quality of the ink by changing the ink’s rheology. In extreme cases, failures can begin to develop due to clogged screens or anilox rolls. Attention must be given to the ink during long press runs with low rates of ink consumption to avoid such situations. The issue can (and should) also be minimized by controlling the local humidity at the print station.

Monitoring pH also is important. Inks that drift outside of their ideal pH range can also exhibit an extreme change in rheology. An ink’s pH does not often need to be adjusted through the course of a press run, but it ideally should be adjusted before any subsequent press run. Solvent-based PTF inks also have some issues that nanoinks do not have. For most nano-inks, it is visibly obvious when an ink is cured due to a color change from an unsintered to a sintered state. Most PTF inks have similar appearance in an uncured, partially cured, and fully cured state. As such, it can be difficult to visually asses if the conductivity of the finished product has changed due to process perturbations.

Scalability Scalability is an important consideration for selecting a conductive ink. If a process is being built for an existing market demand, that process may not meet anticipated demands as the industry grows. While inkjet printing of conductors is very popular

34 | Industrial + Specialty Printing www.industrial-printing.net

for academic and R&D processes, its scalability is very limited. Although highspeed inkjet lines exist, there are material limitations in many of the inks themselves that are not suitable for fast production.

Organically stabilized nano-inks tend to have much slower cure times than PTF and aqueous nano-inks and are not suitable for conventional printing/curing lines.

Today, screen printing is by far the most common method for printing conductive ink. Many flatbed printing lines are meeting today’s demand for printed electronics, and rotary screen offers an increased throughput for a screen-printable conductor. However, if some of the market projections for printed electronics are met, then screen printing may have a difficult time keeping up with demand. Flexography promises to offer production speeds as high as 1000 ft/min, with speeds in excess of 600 ft/min in use today. Migration from a screen process to flexographic process following demand will not always be possible, as products may be locked into existing process/material qualifications.

Price PTF ink is an established technology that has been around for more than 50 years. In its simplest form, a PTF ink can be made by mixing silver flake with white glue or nail polish. However, it would be unfair to sweepingly call PTF formulation simple, because as with any formulation, optimization requires knowledge and experience.

Still, the materials and manufacturing processes required to make PTF inks are less expensive than those required to make nanoparticle inks. As a result, on a pound to pound basis, PTF inks tend to be significantly cheaper than nano particle inks.

PTF inks are currently the most widely used silver ink at the time of the writing of this article. As such, PTF has the advantages of economies of scale that silver nano-inks have not yet obtained. It should be noted that most of the non-scalable manufacturing technologies for silver nano-production have been weeded out of the market at this point in time. Economies of scale should be realizable for most commercial silver nano-inks when the market demand for them increases.

Cost/device The higher price on a liquid-ink basis of

silver nano-inks is often an initial concern for potential users of the technologies. If the assumption were true that to manufacture a given device, equal quantities of ink were to be used, then that concern would be valid. However, two key aspects of nanoinks must be considered when making any cost assessment. First, nano-inks are more conductive than PTF inks and require less material to achieve the same product performance. Second, for a given print method, nano-inks deposit less material than PTF inks.

In the simplest cost model we can present, it can be shown that printing onefourth of the amount of an ink that cost twice as much, still results in a 50% savings on material costs (Table 3). Additionally, other costs must be factored into cost/device calculations, most notably the process cost for the material. A material that can run on a high-speed flexo line will incur lower production costs than a material that needs to be run on a sheet-fed screen press.

However, capital investment costs must also be considered if appropriate. It is perfectly reasonable to assume that a short run on an in-house flatbed screen press with a PTF ink can be more cost effective than starting up a new process with a new nano ink on a contracted flexo press requiring oven upgrades.

Conclusion Choosing the right conductive ink depends on a lot of different factors, including the equipment that’s available, the required performance, and the cost budget for the device being printed. There is no one-sizefits-all solution. With some careful analysis and a better understanding of the strengths and weaknesses of different types of ink on the market, better decisions can be made when selecting an ink for a given design or process.

Chris Wargo

PChem Associates Chris Wargo is a Research Engineer at PChem Associates, a producer of aqueous silver nano-inks. He holds a B.S. in chemical engineering from New Jersey Institute of Technology.

Wargo heads PChem’s Engineering and Applied Technology efforts. He has worked in the field of conductive inks for the past 11 years, with prior positions in formulations and particle synthesis.

Sakurai presents the most precise cylinder screen press available for industrial and multi-pass overlay printing

• Maestro MS-80SD with optical camera registration

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The Maestro prints on a wide range of substrates such as plastic film for electronic applications, membrane switches, display panels, touch screens, paper, board and foil.

The ultra high precision 31-5/8” x 21-3/4” MS-850SD operates at speeds up to 2,000 IPH and accepts stock from .001” to .0031” with precise registration.

To learn more and arrange a demo, contact David Rose: 847-490-4900 or david@sakurai.com ZZZ VDNXUDL FRP january/february 2012 | 35

printing methods

Avoiding Problems with Solar PV System Labels Mark White Fabrico

As solar PV installations continue to grow in the U.S., manufacturers and installers are faced with demands for lifecycle warranties of 20 years or more. Not only do PV systems need to function at rated levels for that time period, but the labels on the systems are also expected to last as long, despite weather conditions, UV exposure, and other factors that affect durability and readability.

Manufacturers of PV systems need to avoid problems due to poor label design and construction, while meeting international, state, and local regulations.

There are many components of a PV system that require labels, including: modules/ panels, interconnects, inverters, and electrical panels/enclosures. Labels are important for production control, traceability, branding, power rating, and other identification tasks. In addition to meeting regulations, labels provide important performance and output information that owners and installers require. The label can also provide confirmation that a specific module conforms exactly to what the customer ordered.

Working with an experienced materials converter and adhesives supplier can help manufacturers avoid unnecessary risks caused by inadequate labels. To avoid label problems, solar system manufacturers need to consider standards, environmental conditions, durability, readability, and cost.

Standards In addition to standards that apply to all electrical products, including UL, CSA, TUV, IEEE, RoHS, and others, solar system labels must meet National Electrical Code (NEC) and International Fire Code (IFC) standards. In the United States, these

standards are then subject to state and local regulations.

NEC section 690 specifies that labels must be durable, unalterable material permanently attached to the device. They must meet current electrical standards and be approved by a nationally recognized testing laboratory, such as UL, CSA, ETL, etc. PV modules/panels need to meet IEEE 1262 (listed to UL 1703) and inverters must meet IEEE 929, 1374, and 1547 (listed to UL 1741). They must also meet IEC 61215/IEC 61646 standards.

Permanent labels are expected to be applied to all components in a system, including the connection to the power grid.

PV modules/panels are labeled with the following types of information: module type, electrical ratings, safety warning, and certifications.

PV power source information must also be posted at the disconnect, which could be part of the inverter. This label includes information on rated maximum power current and voltage, maximum system voltage, and short-circuits voltage. Other labels can be required at the AC disconnect, the location of the ground fault protection, and the utility connection. If the system uses batteries for energy storage, there will be similar labels there.

Types of solar labels Solar labels can include identification labels on the back of solar panels, solar-rating labels, branding labels, solar reflective labels, and warning labels. All have requirements for durability, color, text height, and visibility, as well as resistance to the elements.

Labels attached to the back of solar

36 | Industrial + Specialty Printing www.industrial-printing.net

panels must be able to withstand extreme UV and weather conditions, including sunlight, heat, cold, rain, snow, ice, and high humidity, and remain readable for 20-25 years. They convey critical power rating and product information that’s necessary to ensure manufacturer’s guarantees. A rubbing test is often recommended on these labels, which includes 15 seconds of rubbing on the label with a mixture of alcohol and water to ensure that the serial number remains readable.

In addition to the ability to withstand harsh environmental conditions, labels must adhere firmly to the module, usually the EVA (ethyl vinyl acetate) backsheet. Branding labels are often attached to the panel frame and ensure that the manufacturer’s name and market identity remain visible throughout the module’s life.

Solar-rating labels typically offer a white printable area that includes key power information. These and the panel labels are often laminated for protection.

Solar reflective labels are impact- and scratch-resistant and are normally placed inside enclosures or in dimly lit areas where information requires reflective lettering.

Material considerations A label comprises a facestock, adhesive, liner, and top coat (overlaminate). Label facestocks can be characterized as either paper, film, or metal. Paper facestocks include: coated or uncoated papers, laminated foils, metalized papers, holographic papers, and destructible papers. Film facestocks include: • Polyethylene Terephthalate (polyester, PET, Mylar) • Polypropyene (cast PP, BOPP)

• Polyethylene (PE, HDPE, MDPE, LDPE, Tyvek) • Polyolefins • Polyvinyl Chloride (PVC, flex vinyl) • Polystyrene Metal facestocks can include: anodized metal nameplates, metal bar-code nameplates, and foil bar-code labels.

While paper labels are less expensive than film, film is better suited for solar applications because it is durable, has a long lifecycle, works well outdoors, and can withstand moisture. Polyesters and acrylates are very popular substrates for solar applications. Metal nameplates and foil labels can feature thicker standard materials and are often used for frame labels.

Generally, label adhesives can be rubber-based or acrylic-based. Rubber-based adhesives can have high initial tack, longterm adhesion, good wetting (and bonding) with low-surface-energy (LSE) substrates (plastics), narrow operating-temperature range, poor solvent resistance, and poor UV stability. Acrylic-based adhesives can be characterized with: medium initial tack, long-term adhesion that builds bond strength over time, less affinity to LSE substrates, wide operating-temperature range, good solvent resistance, and UV stability.

Acrylic-based adhesives are now available in formulations that work well with LSE plastics, making these adhesives a popular choice for solar label applications.

Other considerations for adhesives can involve the ability to handle moisture, tolerance for contaminants on the substrate (like oils on metal surfaces), the ability to die cut them into custom shapes, and the availability of the adhesive in a thick caliper to provide strong bonding on textured surfaces, often found in solar applications.

Prior to adhering the label, the liner protects the adhesive on the label during manufacturing, shipping, and handling. Two popular liners include 40-lb super calendered liner, which is easy to die cut and typically used for roll-to-roll applications with paper facestocks; and 50-lb super-calendered liner used with film facestocks. In addition, there are many specialty release liners available, such as machine finished, polyester roll-to-roll liners that are very durable, but not printable, polypropylene—very strong, less expensive than polyester, 44-lb poly-coated kraft paper, natural kraft, and

Figure 1 Roll-to-roll printing facilitates high-speed, high-volume manufacture of labels for a variety of applications.

100-lb tag. The liner is an important part of the label; it affects the ability of the label to lay flat during application and throughout its lifecycle.

The final layer in a label is the topcoat, which can be a laminate, a UV varnish, or some combination of both. A UV varnish is applied as a liquid and dries as a coating. It seals the printing ink to the substrate. It is not as durable as a laminate, but it is able to withstand extreme environmental conditions.

Laminates are generally clear polyester or polypropylene coatings. They are very durable and can protect against extremes in weather, moisture, and UV radiation.

Laminates are the topcoat of choice for most solar labels.

Printing considerations Most label printing (Figure 1) is done via flexography, a form of letterpress that uses a raised, inked surface to impress directly on the facestock. A flexographic press has flexible plates, quick-drying inks, fewer cylinders than a letterpress, and little waste.

Inks used have a relatively high resistance to UV rays and are often similar to inks used in automotive and aerospace applications. Inks can be black and white or color. Thermal-transfer printing is often used in solar-label applications.

Solar labels need to be tested to ensure that they can live up to the rigors of the application. Testing could include UV testing, prohesion testing, and thermal cycling. UV testing can incorporate light, heat, and moisture. Prohesion testing uses a salt spray/fog and high humidity. Thermal

cycling tests for delamination, cracking, and bubbling caused by heat extremes.

Working with a converter who can actively participate in the test process allows for the consideration of alternatives at every step in the label design to reduce costs, increase durability, increase manufacturability, and improve integration into solar-system manufacturing and assembly.

In conclusion Labels for solar PV systems are a critical, but often overlooked, part of the manufacturing, sales, and use lifecycle. As demand for 25-year warranties increases, labels are expected to perform as well as the system itself. Durability in extreme weather and operating conditions, plus readability over a 25-year or greater period is key for quality control and tracking, as well as important electrical, installation, and warning information on every part in the solar system, up to and including the connection to the grid.

Working with an experienced flexible-materials converter and adhesive supplier can help solar manufacturers to ensure that they are producing quality labels to match their systems and meeting industry and regulatory standards.

Mark White Fabrico

Mark R. White III is the technical sales representative, printing, for Fabrico and is responsible for all printing and label-printing activities. He is located at company headquarters in Kennesaw, GA, and can be reached at mwhite@fabrico.com. january/february 2012 | 37

industry insider

Printing Microelectronics John Fraser

Ohio Gravure Technologies The microelectronics industry is developing the ability to print active electronic circuits on inexpensive and non-traditional substrates in extremely large volumes.

Some of the potential products are intelligent RFID tags, intelligent packaging, large-area devices such as solar-cell arrays and LED panels, smart sensors for food and medical uses, and energy storage. The substrates will be low cost with low temperature characteristics and will eventually be processed on wide-web printing equipment. The electronic components will also be large-area and low-temperature devices.

The volume of the end products being manufactured will be measured in square kilometers rather than square centimeters.

And the intelligence of the new products will enable the next era of revolutionary social changes.

I see the microelectronics industry as presently developing the basic processes and materials for printed electronics. The industry does not yet have good materials for semiconductor performance, although conductors and insulators are well enough defined so that process development for small conductors and small conductor spacings can be investigated in detail.

Inasmuch as the printed-semiconductor chemistry is poorly defined, so also is the associated substrate incompletely defined.

The microelectronics industry has a lot of work to do on material definition. Polymers, glasses, and metals are all candidates as materials for both the substrate and the printing cylinder, and all must be compatible with the chemistries that emerge for the semiconductor materials. A critical characteristic of the new semiconductormaterial processes is that they must be processed at low temperature and at ambi-

ent gas pressures. These are the enabling characteristics of high-volume, low-material-cost products.

Gravure printing is ideal for the materials being printed as electronic devices and compatible with a large variety of substrate materials. The gravure process holds the ink in cups or depressions below the surface of the image-carrying cylinder and because of the rather large volume of the ink-carrying cup, solid materials can be carried in the inks as well. The mechanical properties of the ink, such as viscosity, density, and chemistry can vary widely. The material of the cylinder can be almost any metallic material or synthetic and can be tailored for compatibility with the process and chemistry of the ink, the substrate, and the processing steps of the product. Gravure has already been proven at line widths and spacings down to individual microns with the microelectronic-process materials presently being investigated.

Process machinery is in development in the 100- to 1-Îźm accuracy range to respond to the new needs of the microelectronics industry. Mechanical techniques developed for the submicron-semiconductor industry certainly are appropriate for the microelectronics industry, and they are a part of the design for high accuracy. Conventional printing, however, does not profit from lines and accuracies below about 100 Îźm. The eye does not see misregistration or detail variations at that level, and there is no profitability in designing conventional printing machinery to handle that level of accuracy. In the microelectronics world of products of large-volume output, the accuracies that fall between the semiconductor and conventional printing are the

38 | Industrial + Specialty Printing www.industrial-printing.net

technological enablers. So the production environment of microelectronics will be one of a synthesis of the best practices of the semiconductor and printing industries.

An example of a predicted product is an RFID tag as a near-term goal of microelectronics. By including logic and memory capability on the tag, enough information can be included to individually tag each item on a storeâ&#x20AC;&#x2122;s shelf. Lighting by light-emitting diodes (LEDs) has the promise of the highest efficiency and lowest maintenance of present technologies. With the cost of energy soaring, it is likely that staggering amounts of LED illumination devices, perhaps in the form of ceiling tiles, will be needed. This requires a process capable of producing thousands of square kilometers of product.

The present level of development of the microelectronics industry is to solve process problems, and the greatest immediate need is for process machinery to support development. As the processes stabilize, larger and faster production equipment will become necessary. Ohio Gravure Technologies looks forward to an exciting future in this large and growing new industry.

John Fraser

Ohio Gravure Technologies John Fraser is a physicist with Ohio Gravure Technologies. He works in product R&D and manufacturing processes. He has been with Ohio Gravure Technologies and its predecessors for 28 years. Fraser holds or has participated in multiple patents with respect to gravure technology and unrelated fields. He works with mechanical, electrical and electronic, optical, magnetic, servomechanisms, and general physical applications. He has been a physicist for more than 40 years.

ADVERTISING INDEX

January/February 2012

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ASYS Group Americas Inc

IFC

MacDermid Autotype

AWT World Trade Inc..

25

Mimaki USA

OBC

Douthitt Corp.

3

Novacentrix

33

Dynamesh Inc.

29

Ohio Gravure

15

FlexTech

9

RH Solutions

11

Fujifilm Dimatix

19

Sakurai USA

35

Graphic Parts International

25

Spartanics

35

Industrial Inkjet

19

ST Book Store

25

IPC Apex Expo

IBC

Xaar Americas

19

Kammann USA Inc.

25

Xenon Corporation

9

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The Power of Organic Phot ovoltaics A Look at Diec Technologies utting Opportunities Medical Elec Abound in tronics

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CANYON GRAPHIC, INC. location San Diego, CA When Canyon Graphics was established in 1981, the core business revolved around precision screen printing, lamination, and fabrication of labels, control-panel overlays, and membrane switches. Today, Canyon has developed additional processes and technologies, including forming, 3D trimming, automation, injection molding, and in-mold decoration. Most recently, Canyon developed a process for in-mold printed electronics (IME) along with a decorative appliquÊ (IMD) in a thin form factor of less than 3 mm. To learn more about the company, visit www.canyongraphics.com. other info

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Automated work cell for manufacturing in-mold-decorated buttons used in an appliance application

knife plotter used for prototype 4 Digital and short-run applications

2 Canyon Graphics Facility in San Diego, CA

5 Automated roll-to-roll screen printing press.

work cell making appliance 3 Automated control panels

6 Assembled, in-mold decorated button modules

40 | Industrial + Specialty Printing www.industrial-printing.net

Innovation drives results

In this economy, innovation is everything and IPC APEX EXPO 2012 is where you’ll find the information to inspire it!

We are gathering the brightest minds, top suppliers and most exciting technologies to help you discover innovative ways to manufacture, manage your supply chain and succeed in 2012. Learn at the world’s premier technical conference with leading experts and a new track on printed electronics. With an exhibit hall overflowing with advanced and emerging technologies in printed board design, manufacturing, printed electronics and electronics assembly, this event is second to none.

Register early for FREE exhibit hall admission and extra savings at

www.IPCAPEXEXPO.org

New Focus on Printed Electronics • Technical Conference • Standards Development • Exhibition www.IPCAPEXEXPO.org/printed-electronics

• DESIGN • PRINTED BOARDS • ELECTRONICS ASSEMBLY • TEST with a new focus on printed electronics

INFORMATION that INSPIRES INNOVATION

Use your smart phone reader!

Enter for a chance to win a free All-Access Registration or a free hotel stay!

Flex your UV options UV LED TABLETOP FLATBED PRINTER

Expand your UV industrial printing in new directions with the UJF-3042FX and its new flexible ink sets and primer ink for printing on practically anything.

DYE UJF-3042FX SUB INK

Expanded Ink Sets

PR-100 is a NEW UV Primer ink that can be used in

Mimaki’s tabletop-sized UJF-3042FX is a versatile and affordable UV LED flatbed printer with a generous print area of 11.8” x 16.5” for printing on a growing choice of substrates and dimensional objects up to 1.9” thick.

Now with the addition of our new Primer and Flexible inks for optimal adhesion, your substrate choices open up to plastics, metals, glass and more.

C M Y K lc lm + W + Cl

LF-140 is a NEW UV Flexible ink offering 6-color printing along with white and clear. More flexible than LH-100 ink, making it less likely to crack during post-processing.

C M Y K + W

Use the UJF-3042FX for: one-offs, prototypes, industrial and interior signage, molded switches and panels, packaging, ID badges, promotional items. You’ll find the application options are more flexible than ever.

LF-200 is a NEW UV Ultra-Flexible ink that is able to stretch up to 200% without cracking.

C M Y K + W + Cl

LH-100 is a UV Hard ink that excels in scratch and

 Scan to see UJF-3042FX applications. or go to: www.mimakiusa.com/qr-ads/121511/UJF3042FX/apps/

Focused on solutions.

combination with LF-140 and LF-100 inks. This primer ink is simultaneously under-printed as a spot ink with CMYK.

chemical resistance and is ideal for media that does not require bending or folding after printing.

Listen. Connect. Deliver.

EMAIL INFO ATL

888-530-3988

BOS

888-530-3986

CHI

info15@mimakiusa.com

888-530-3985

LA

888-530-3987

www.mimakiusa.com

© 2012 Mimaki USA, Inc.

Mimaki 3042FX_FBC_ISP0112.indd 1

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