PCB-komponenter SMT / THR
TA B L E O F C O N T E N T S
TA B L E O F C O N T E N T S
1
From THT to SMT – the evolution of PCB assembly
4
2
THR – the revolution in PCB assembly
5
3
The SMT process for modules with THR components
6
3.1 The process steps at a glance
6
3.2 Design of the PCB and stencil
6
3.3 Paste printing
10
3.4 Placement
12
3.5 Reflow soldering
14
3.6 Quality control
16
4
18
SL-SMT – Weidmüller’s innovative THR components for the SMT process
APPLICATION INFORMATION
3
1 FROM THT TO SMT
T H E E V O L U T I O N O F P C B A S S E M B LY
THT – assembly with leaded components
components and the soldering process
When use is made of Through-Hole-
is used, PCBs can be equipped with SMD
There are still applications in which
Technology
the
components both on one side and on
SMDs and leaded components have
standard process in module production
both sides. They are assembled with
to be placed on the PCB. Up to now,
up to a few years ago, the wire terminals
machines, for example "Pick & Place" or
in the case of modules with such
of the components are inserted into
"Collect
systems, which
component mixes use has been made of
the holes on the printed circuit board.
process all components in the state in
two different soldering processes: firstly
Boards are assembled manually or
which they were delivered, dispensing
reflow soldering for the SMDs followed
with special placement machines. The
with special preparation of components.
by (mostly manual) placement of the
(THT),
which
employed. Thus, when the SMT process
was
&
Place"
so-called manual or wave soldering
leaded components with subsequent In the SMT process, use is made of
process is used.
SMT compatibility in the case of modules with component mixes
manual or wave soldering.
reflow soldering, for example infrared, Drawbacks of THT:
convection and vapour phase soldering.
• production is time-consuming and
Contrary to the wave soldering process, only a solder paste deposit applied to the
costly
PCB is melted on.
• low function density • increased susceptibility to faults
PCB double-sided mixed assembly with THT and SMD components
due to a lack of manual precision
Manual placement and the use of manual/wave
soldering
for
SMT
manufactured PCBs is a costly and critical process, which can lead to quality defects. There is a need for Single-side PCB assembly with THT components
achieving consistent SMT compatibility, i.e. making leaded components suitable for the SMT reflow soldering process in PCB double-sided assembly with SMD components
SMT – assembly with SMD components
order to reduce manufacturing costs and to eliminate the wave soldering process,
With the advent of Surface-Mount-
Advantages of SMT:
which is susceptible to faults.
Devices
• high quality
The special process developed for this
Technology has increasingly taken the
• lower processing cost
purpose is known by various names on
place of THT. And the trend towards
• smaller components
the market, namely Through-Hole-Reflow
producing electronic modules by surface
• high packing and integration density
(THR), Pin-in-Paste (PIP) or Pin-In-Hole-
mounting is continuing.
• optionally single-sided or double-
Intrusive-Reflow (PIHIR).
(SMD),
Surface-Mount-
As the current standard process in
sided assembly
electronic module production, SMT is defined by the method of processing 4
APPLICATION INFORMATION
2 THR
T H E R E V O L U T I O N I N P C B A S S E M B LY
Through-Hole-Reflow is a process for joining THT components using the SMT reflow soldering process. In addition to conventional SMD placement, when THR is employed the SMD components are placed onto the SMT board together with leaded components and are soldered in the reflow process. Mechanically not stressable connection: e.g."Gull Wing" type
The THR process was the result of the awareness that stable soldered joints are still needed for heavy components such
Advantages of THR:
as coils or transformers and wherever
• stable connection to the PCB
mechanical forces act on the PCB
• only one soldering process
(e.g. in the case of connection terminals,
• manual/wave soldering is eliminated
connectors,
• automatic component placement
relay
sockets,
etc.).
Considering mechanical criteria, SMD
• lower production cost
soldered joints are not suitable for heavy components.
For THR components to be processed in the SMT process, certain demands have
A SMT compatible product is always
to be met. These are described in greater
a compromise between optimum SMT
detail in Chapter 3.
capability and maximum stability of the soldered joint. With push-through pins, THR ensures a stable joint between the THT
components
and
the
PCB.
100% SMT process compatibility is achieved at the same time.
Mechanically stressable connection: THT
APPLICATION INFORMATION
5
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
3.1 The process steps at a glance
1
3.2 Design-in
The design of a printed circuit board
The SMT production process begins with
for SMD components is generally very
design of the PCB. It is as early as in
easy to produce. Once the design of the
this first step that the later smooth
soldered joints has been defined, to
sequence of the production process and
avoid process errors the hole layout of
thus the quality of the PCB a s s e m b l y
the stencils for paste printing is often
process are defined. In comparison
defined about 10% smaller.
Design-In: design of the PCB and
with the classical SMD or Through-Hole-
stencil layout for THR components
Technology, a few special features have
By contrast, in the case of THR
to be observed in the design of PCBs
components a drill hole must be filled
for THR components. Special design
with solder paste. In this case, the
recommendations contribute towards
quality of the soldering process depends
ensuring
on what degree of filling of the holes
an
optimum
production
process.
with solder paste can be achieved in the printing process.
2
To optimise the degree of filling,
Paste printing: solder paste applied
Weidm端ller recommends the following
into THR placement holes
steps:
3.2.1 define the diameters of placement holes and soldering eyelets
3.2.2 calculate the solder volume or
3
Placement: inserting the THR component pins in the solder paste
4
Reflow soldering: melting on the
solder paste
the necessary paste volume
3.2.3 determine the degree of solder paste filling
3.2.4 design the stencil layout
5
Quality control: assessment of the finished THR soldered joint
6
APPLICATION INFORMATION
3.2.1 Defining the diameters of placement holes and soldering eyelets
The
tolerances
of
the
PCBs,
the
Soldering eyelet diameter:
placement machine and the component
The volume of the soldering meniscuses
must be taken into account as further
should also be optimised so as to
To calculate the necessary paste volume,
factors in determining the placement
minimise the solder volume. This is
first define the volume of the soldered
hole
automatic
achieved by minimising the soldering
joint in accordance with the required
placement process. For example, in
eyelet diameter in comparison with
quality. For an adequate soldered joint,
the case of connectors the position of
diameters as are usual in classical
the internationally recognised quality
the pin end in the pitch is subject to
Through-Hole-Technology.
standard IPC A610B calls for a 75%
special tolerances, with the result that
filling height in the PCB (see also
it is the respective manufacturer's task
Recommended soldering eyelet diameter
Section 3.5 "Quality control").
to optimise the pin end position's circle
for through-hole soldered joints:
The designer first defines the relevant
of throwout.
diameter
for
the
diameter of the placement hole and of
placement hole diameter
the soldering eyelet. Both parameters
Weidm端ller recommends the following
+
determine
as suitable placement hole diameters
2 x residual ring width
the
necessary
soldering
volume for a given THR component.
=
for THR soldering processes:
soldering eyelet diameter Placement hole diameter:
For round pins:
For THR soldered joints (contrary to
pin diameter + at least 0.3 mm
The residual ring width usually amounts
wave
For rectangular pins:
to 0.3 mm. For THR components such
pin diameter + at least 0.25 mm
as connectors a slight increase in the
soldering),
a
slightly
larger
placement hole diameter is advisable because melting-on of the paste in the
residual ring width to about 0.4 mm is
hole needs sufficient space. Solder
advisable for reasons of higher soldered
pastes also consists of a mixture of
joint stability and reparability.
soldering globules and admixtures (flux), and are categorised according to grain sizes. To avoid jamming or friction of the pin in the hole with these soldering globules during the placement process,
Soldering eyelet diameter
the chosen grain size should be as small as possible.
Residual ring width Placement hole diameter Placement hole layout for THR pins
APPLICATION INFORMATION
7
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
3.2.2 Calculating the solder volume or the necessary paste volume
3.2.3 Determining the degree of solder paste filling
The solder volume that is necessary for
For an optimum layout of the PCB, it
an optimum soldered joint is calculated
makes sense to check whether the
as follows:
previously calculated necessary paste volume can be achieved at all. Therefore,
placement hole volume
in a test the degree of solder paste filling
+
should be determined in a PCB hole.
meniscus volume
According to the test setting, a test PCB
–
with the defined hole diameters, for
terminal pin volume
example is entered in the paste printing
=
process. The filling height of the holes in
Degree of filling approx. 120 %
solder volume
Determining the degree of filling
3.2.4 Design of the stencil layout
the PCB can then be checked visually. If the optimal degree of solder paste filling was achieved, the standard design Pin
rule can be used for the stencil hole design: stencil hole diameter about 10% smaller then soldering eyelet. Diverse process parameters contribute towards a situation in which the degree of hole filling is not achieved. In this case, several possibilities of optimising the
Solder meniscus
degree of filling are at the printed
Placement hole
circuit board designer's disposal:
Necessary solder volume for THR soldered joint
Once the solder volume has been
The following applies:
• optimising the printing parameters (see Section 3.3 "Paste printing")
determined, the necessary paste volume
• optimising the stencil layout: If there
can also be calculated. Due to the high
100% filling of the PCBs thickness
evaporation factor of the solder paste in
=
is not enough paste, printing over the
the soldering process (generally about
100% degree of filling
soldering eyelet is advisable. Various
50%), it amounts to approximately twice
forms of asymmetrical printing can
the volume:
also be applied. As an alternative, stepped and additive stencils or paste volume
= solder volume x 2
double printing by means of extremely thick stencils can also be applied. If there is too much paste, webs over the breakouts of the stencil may function as a paste brake.
8
APPLICATION INFORMATION
Stencil hole diameter
Additional design factors : For a smooth SMT production process, the following factors should also be observed when designing a module:
• shadow formation in the reflow oven, caused by high housings of the THR components, can be avoided by an adequate distance between the components
Stencil hole layout assuming adequate degree of paste filling
• the components' contact faces must be taken into account to ensure that the insulator does not come into contact with the paste • fixing by glueing may be necessary if, in the case of double-sided
Stencil hole diameter about 10% smaller than soldering eyelet diameter
modules, a THR component is placed on the first placement side
Solutions and recommendations from Weidmüller In a first draft of the printed circuit board and stencil layout, you can safely work with the known standard process parameters.
For their SL-SMT pin headers with short pins (1.5 mm), Weidmüller suggests the following PCB design: Placement hole diameter: 1.5 mm Soldering eyelet diameter: 2.3 mm Stencil hole diameter: 2.1 mm (assuming adequate degree of paste filling) Stencil hole diameter: 2.8 mm (if the degree of paste filling is not enough) Valid for: PCB thickness: 1.5 - 1.6 mm Stencil thickness: 0.12 - 0.18 mm
APPLICATION INFORMATION
9
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
For an optimum degree of solder paste
3.3 Paste printings
filling, the following process parameters Preparation of the PCB, i.e. applying
must be taken into account in the paste
solder paste on the soldering pads, is
printing process:
one of the most important steps in the SMT production process. The quality
• stencil thickness:
achieved here has a crucial influence
generally 120 to 200 µm
on the quality of all further process
• optimum coordination of the solder paste grain size (20-40 µm) and
steps. The soldering result in the subsequent
placement
and
reflow
Open stencil printing process
volume percentage of the flux (mostly 50%)
process is determined by the necessary paste volume and thus the degree
In closed printing systems such as
• coordination of squeegee speed and
of solder paste filling during paste
"ProFlow", however, a paste deposit with
pressure: a higher degree of filling
application. For optimum filling of the
a variably adjustable pressure travels
with open paste systems is achieved
THR holes within the usual process
over the stencil. The advantage: better
by a lower speed or a flatter angle
tolerances, printing of the solder paste in
monitoring of the pressure and printing
(e.g. 45° instead of 60°)
two different stencil printing processes
speed permits paste printing by High-
has asserted itself, namely the open and
Speed Fine-Pitch Technology as well as
closed stencil printing processes.
controlled filling of the THR hole. Various stencil variants can be used depending
In the open stencil printing process,
on the chosen technology, namely the
a metal or plastic squeegee pushes the
low-cost standard metal stencils or even
roll of solder paste over the stencil.
expensive "exotic" variants such as
The drawback of this process is that both
stepped or double printing stencils.
the pressure and the printing speed can only be varied within a very limited range.
Pin header (open and closed ended):
2 to 8 poles
Pin header (flanged LF): recommended inside diameter
9 to 24 poles 2 to 24 poles
d I = 1.4
+0.1
mm
d I = 1.5 +0.1 mm
finished hole *1): paste volume VP [mm 3] / filling level fp [%] after print minimum solder joint shape
2.4 mm 3 / 70 %
3.1 mm 3 / 85 %
optimum solder joint shape
2.9 mm 3 / 90 %
3.5 mm 3 / 100 %
Example of a recommended paste volume or degree of filling for SL-SMT pin headers accord. to data sheet
10
APPLICATION INFORMATION
Various requirements for the leaded components can now be derived from these parameters:
• as the housing of the leaded component must not touch the solder paste, its stand-off height should be at least 0.3 mm • the pin cross-section geometry, the pin tip and its length must be optimised to minimise the paste volume needed
If the degree of solder paste filling is too low, then it is advisable to overprint to achieve the necessary paste volume. Overprinting means that the stencil hole diameter is designed to be larger than the soldering eyelet diameter and the paste is printed over an area larger than the soldering eyelet, and out onto the PCB. This can, of course, cause soiling of the underside of the stencil, which can be removed by a shorter cleaning
Overprinting can lead to soiling of the underside of the stencil
cycle of the stencil.
Solutions and recommendations from Weidmüller To realise the lowest possible paste volume in stencil printing, the SL-SMT pin headers from Weidmüller feature short octagonal pins with chamfered pin ends. Above all thanks to the pin length of only 1.5 mm for standard pc boards with a thickness of 1.6 mm, a filling degree of 90 % only is adequate for an optimal solder joint shape. Therefore in most cases normal single-layer stencils for fine-pitch technology and the standard process parameters for the squeegee speed and pressure can be used during paste printing.
Further advantage: in the placement process, the paste is forced out of the placement hole to a lesser extent.
APPLICATION INFORMATION
11
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
The following parameters must be
This
observed with regard to the optimum
requirements
Automatic sequential placement is one of
placement suitability of leaded terminal
elements:
the placement processes that is used
elements and thus easy integration
most frequently in the SMT process. Use
into the placement process with usual
is made of both pick & place systems
standard placement systems:
3.4 The placement process
results
in for
the
following
leaded
terminal
• minimised weight for an placement speed that is as high as possible • minimised component length for a
and of collect & place systems (chip shooter). In the pick & place station, only
high rotation and transport speed
one components is taken from the
and thus maximum placement
component feeder by means of a vacuum
performance • minimised height to avoid a
pipette, and is placed on the pcb. Tray packaging accord. to IEC 286-5
restriction of the travel height over the PCB and thus to prevent
• packaging in line with standards:
collisions
fully automatic feeding of the terminal elements with tape-on-reel or tray is possible • dimensional stability of the component: lowest possible water absorption during storage under Pick & Place head transports SL-SMT 3.5
normal climatic conditions ensuring
By contrast, a chip shooter transports
pitch fidelity of the component
several components to the corresponding
• suction surface of the component:
placement position and deposits them
determined in relation to the weight
there.
or size for the use of standardised
Packaging of the components is the
vacuum nozzles
basis for the use of both processes.
• precision of the pin end position:
A distinction is made between tape-on-
smallest possible tolerances
reel, tray, tube and bulk. The pick & place
(in addition to hole position and
process with tape-on-reel or tray has
machine placement tolerance)
established itself for leaded terminal
prevent problems caused by collision
elements.
of the component with the PCB
12
Tape-on-reel packaging accord. to IEC 286-3
• minimised tooling effort by using components in high packed numbers to achieve lower product and tooling costs
APPLICATION INFORMATION
Changes in length because of water absorption
% PA 4.6: 1 % => 0.5 mm / 50 mm => „50.5“ mm (total length for a 10 pole pin header)
1.0
50.5 Pin header SL-SMT with pick & place pad
LCP: 0.03 % => 0.015 mm / 50 mm => „50.015“ mm (total length for a 10 pole pin header)
50.015
0.03
mm Total length for a 10 pole pin header with pitch 5.00 mm Dimension changes because of water absorption for different materials.
Solutions and recommendations from Weidmüller To avoid quality-reducing dimensional changes, the SL-SMT pin headers from Weidmüller are made of LCP (Liquid Crystal Polymer). LCP is particularly distinguished by very low water absorption.
The SL-SMT pin headers have a low height thanks to the use of short pins (1.5 mm). This is why the height of the tape-on-reel or tray packaging can also be very low. The result: a large number of packaged units in each reel. The antistatic packaging in line with standards also permits fully automatic placement using commercially available pick & place systems.
Further advantages of the short pins of the SL-SMT are optimised travel height and the precision of the pin end position, thus avoiding collisions between the components and the PCB. And, as the SMT-optimised pin headers from Weidmüller are very light, they also maximise placement performance.
APPLICATION INFORMATION
13
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
Each of the three processes calls for a
Soldering heat resistance is tested for
special process temperature curve,
the highest category A, by dipping the
The most important step in the SMT
which also applies to THR components.
component in a soldering bath:
production
As increased use will be made of
The insulator floats on the surface of
printing is the reflow soldering process.
unleaded
the solder and all soldering contacts
This process is characterised by melting
increased temperatures in the future,
are immersed. The minimum
of an existing solder deposit. During the
the demands on the temperature load
requirement is 260 °C/10 sec.
process about 50% of the paste volume
carrying capacity of components will
evaporates. The aim of reflow soldering
continue to rise.
3.5 Reflow soldering
process
besides
paste
soldering
processes
with
is to enable soldering of all THR joints in all soldering processes.
For use in the reflow soldering process, the following factors or requirements are
Currently three different reflow soldering
crucial in regards to THR components:
processes are needed in industrial applications:
• Soldering heat resistance:
Melted isolation body due to inadequat thermal resistance of the plastic
the shape and the functionality of the
Moreover, the component's suitability
component must not be damaged by
for passing through the soldering
exploits heat radiation with natural
the soldering process. In this respect,
process twice (double-sided
convection, as generated by quartz
all components can be checked with
assembly) must be guaranteed.
or area radiators, for example, to heat
a test method that is described in
the module.
EN 61760-1. This process permits the
• Infrared soldering:
measurement of THR component’s • Convection soldering: heats up the module by force
thermal resistance by means of a simulation.
convection by means of the
process gas such as air or nitrogen.
• Vapour phase soldering:
Temperature (°C)
circulation of large volumes of a
Melting 240° C 230° C 215° C
uses a condensating saturated vapour phase as the transmission
180° C 160° C 150° C
medium which dissipates its
Approx. 60sec > 180° C
130° C
condensation heat directly to the surface of the medium.
Pre-heating
Usual
Time (sec)
Infrared soldering, convection soldering – temperature/time diagram (temperature on connection)
14
APPLICATION INFORMATION
• Thermal coefficient of expansion:
• Solution:
The most frequent sources of faults are:
very long components such as
make components out of highly
multiple-pin connectors, which
temperature-resistant plastics with
exhibit a significantly different
low water absorption.
• Errors in component design: accessibility of the soldered joints for
thermal response to that of the PCB
the thermal transmission medium
material may lead to sagging of the
Even if apparently all factors and
(e.g. air) is restricted by neighbouring
module after soldering or in the
requirements
components. This can, however, be
cooling phase. To avoid this problem,
participating in the reflow soldering
defined in advance by means of an
the temperature response of the
process have been met, though, in some
appropriate component design.
components and PCB materials
cases the desired production quality
• Errors in PCB design:
should be as similar as possible.
cannot be achieved.
for
the
components
copper terminal faces that are too
Usual materials such as PBT or
large lead to heat sinks on the
PA 6.6, which are used in connectors
soldering eyelets.
designed for wave soldering
• Faults of the soldering machine:
processes are therefore not suitable
the melting temperature that is
for reflow processes.
necessary for the solder paste at the soldered joint is not reached due to inadequate efficiency of the reflow soldering machine or of the programmed process profile.
Solutions and recommendations from Weidmüller Weidmüller manufactures long components such as multiple-pin pin headers out of fibre-glass reinforced LCP (Liquid Crystal Polymer). This high temperature-resistant, Melted isolation body due to inadequat thermal resistance of the plastic
halogen-free insulator has a melting point of 335 °C and therefore exhibits high stability of shape and very good soldering heat resistance. Weidmüller surpasses
• Water content:
EN 61760-1 and subjects its terminal elements to 2 x 260 °C/10 sec. for a double
only components made of insulators
passage through the process. The SL-SMT pin headers made of LCP even withstand
with minimum water absorption
2 x 290 °C/30 sec. and are therefore oriented to the future and can also be used in
prevent bubble formation during the
every lead-free soldering process.
soldering process and thus modification of the insulator's
One further advantage of LCP is its extremely low thermal coefficient of expansion.
surface.
Measured on the SL-SMT pin header from Weidmüller, it amounts to 0.16% at 260 °C = 0.08 mm for a length of 50 mm, for example. It therefore exhibits a thermal response that is similar to that of common PCB base material, for example FR4, with the result that sagging of a pcb after the soldering process is avoided in any case.
APPLICATION INFORMATION
15
3 THE SMT PROCESS
FOR MODULES WITH THR COMPONENTS
In the case of X-ray inspection, a
Standards:
so-called radiographic evaluation is
Various standards have come into force
Quality control concludes the SMT
run by means of an automated X-ray
in the past years to enable objective
production process. The aim of this
microscope. In addition the inspection
quality control. Besides other acceptance
process step is to enable swift and
processes during the production process,
test criteria for the production quality
simple assessment, by suitable means,
an important inspection step consists
of electronic modules, the assessment
of the quality of the soldered joints of
of destruction tests. Carried out on
criteria based on the IPC-A-610B have
THR components with short or long pins.
samples, they serve to check measurable
been acknowledged the world over.
The same rules apply to quality control of
quantities:
According to IPC-A-610B, the quality
3.6 Quality control
the THR technology as to reflow or wave-
requirements for THR soldered joints are
soldered THT components.
subdivided
into
three
categories.
Generally the requirements of category 3 Inspection method:
are decisive for high-power electronics
Quality control in parallel with the
in industrial applications. The following
process can be realised by means of
values have been defined for the total
different processes. At the moment,
number of five assessment criteria:
mostly optical or X-ray inspection is used. The optical test evaluates the shape, reflection and colour of soldered joints.
Cross-section of the THR-solder joint with short pin
• analysis of the degree of filling by
• circumferential wetting of the primary side (i.e. the component
means of a cross-section through the
side from the component's point of
soldered joint
view), the terminal and the sleeve
• mechanical inspection of the force needed to pull the pins out of the
must not fall below 270° • vertical solder filling must be at least 75%
through plated holes
Optical test of soldered joints below the housing body.
When done manually, a magnifying glass or a microscope is used and, in the automated process, a computercontrolled camera performs computerassisted image evaluation.
75 %
Dimensioning the filling height for through-hole soldered joints in accordance with IPC-A-610B
16
APPLICATION INFORMATION
• circumferential wetting of the
These requirements apply to long pins:
in the case of surface connections with
secondary side (i.e. underside from the point of view of the component) must not fall below 330° • solder wetting of the original land face (i.e. residual ring in the case of
For comparison:
• the soldered joints on the secondary side must be visible
SMD components, the required pull-out force amounts only to about 15 – 20 N.
• by comparison, soldered joints on the primary side are not necessary
THR soldered joints) on the primary side is defined as 0% • solder wetting of the original land
In the case of destructive inspections in conjunction with THR components,
face on the secondary side must be
demands are also placed on the PCB.
at least 75%
The force needed to pull the pins out of the soldered joint is checked to ensure
With regard to quality control, these
the quality of PCB production:
standards result in several requirements for leaded components. It is necessary
Required pull-out force:
to take into account the fact the two
- for short pins: approx. > 150 N
different designs are normally used for
- for long pins with solder meniscus on
the THR process:
Short pin pulled out with pull-out force of >150N
the primary and secondary sides: approx. > 220 N
• shorter pins in comparison with the PCBs thickness • longer pins in comparison with
Solutions and recommendations from Weidmüller
the PCBs thickness (approx.
Short pins with a solder meniscus only on the primary side attains a comparably
1.0 – 1.5 mm overhang)
high stability which is otherwise only possible when using the conventional THT. Hence THR components - like Weidmüllers SL-SMT - fitted with short THR pins have
The following requirements apply in the
a considerable advantage over real surface-mount connections.
case of short pins: The special design of the SL-SMT pin headers from Weidmüller permits visual • the soldered joints on the primary
inspection of a PCBs primary side, even in the case of variants with an 180°
side of the PCB must be visible
outgoing direction, thus creating the prerequisite for quality control in parallel
• in the case of components with pins
with the process.
under the insulator, the height of the stand-off or the product design must
However it is important that the control side of the components is not concealed by
be adequately dimensioned for visual
other high elements. Weidmüller recommends therefore, during the layout of the
inspection
PCB, to take into consideration the placement possibilities of the components on the primary or quality inspection side.
APPLICATION INFORMATION
17
4 S L - S M T – W E I D M Ü L L E R ' S I N N O VAT I V E
THR COMPONENTS FOR THE SMT PROCESS
The new standard in the SMT process
SL-SMT are consistent!
SL-SMT are extraordinary!
SL-SMT are made of high-grade LCP
SL-SMT use short pins with a length
(Liquid Crystal Polymer).
of only 1.5 mm.
of experience in the SMT production
Your advantages:
Your advantages:
process and the concentrated know-
• maximum pitch fidelity and
• double-sided SMT placement with
how about what demands it places
dimensional stability in the
on THR components. This is why
placement process
of printed circuit board assembly comes from
Weidmüller:
the
SL-SMT
pin
headers. Every SL-SMT pin header incorporates Weidmüller's many years
SL-SMT pin headers not only fulfill
• required paste volume minimised
• thermal response similar to that
these requirements, they also offer
of common PCB materials
you the optimum workflow in automatic
• temperature-resistant for all
two-sided PCB assembly, thus reducing
common soldering processes
your production costs by up to 30%.
a PCB thickness >= 1.5 mm
• simplified paste printing process • no-problem outgassing of the flux in the soldering process
• maximum orientation to the future: halogen-free and capable of recycling • maximum design flexibility: available in versions from 2 to 24 pins
1.5 mm
• guaranteed assumption of the necessary temperature in the soldering process thanks to a reduced metal mass • lower component height avoids collisions in the placement process • reduced packaging height permits the use of standard feeders • optimised quantity in each packaged reel 2 to 24 poles
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APPLICATION INFORMATION
SL-SMT are innovative!
• optimised stability in the soldered
SL-SMT are intelligent!
joint in comparison with round pins SL-SMT feature an integrated paste
• minimisation of the placement force
SL-SMT are obtainable in the intelligent
space with stand-off height of at
needed, for setting the pins
packaging design – suitable for several
least 0.3 mm.
into the paste by the placement
pin number variants.
machines Your advantages: • only one feeder width is necessary for several pole numbers • compatible with all common pick & place placement systems • lowest possible packaging heigth
0.3 mm
for a higher quantity per reel • antistatic ESD materials for problem-free placement Your advantages: • very simple stencil design for standard layout or for printing over
Optimised pin tip
• design-compatible with standard pin headers because there is no additional stand-off Pin header with 180° outgoing direction and open ends: SL-SMT 5.08/8/180
SL-SMT are application-optimised!
SL-SMT feature octagonal pins which are specially designed at the ends.
Your advantages: • minimisation of the necessary through hole diameter and thus of the necessary paste volume • better recognition in vision systems thanks to enlarged reflection faces
Product specific packaging design
APPLICATION INFORMATION
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PCB-kompendium EL-nr. 79 00 011 163