Marquez - Nguyen - TI Dallas -Acid & ASAP-1

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Proceedings of the 32nd International Symposium for Testing and Failure Analysis November 12-16, 2006, Renaissance Austin Hotel, Austin, Texas, USA

New Approach: Sample preparation techniques for plastic small outline package (front-side and backside). Erwin Marquez and Dat Nguyen Texas Instruments Inc 12500 TI Blvd. M/S 8738 Dallas, Texas 75243 Email: erwin-marquez@ti.com, Phone: 214-8868913

To enable successful failure analysis for this package type, we developed a failure analysis sample preparation method, which facilitates backside and front-side failure analysis methods.

Abstract As device packages become smaller, the job of failure analysts becomes more difficult. Other complex configurations such as Small Outline Packages (SOP) pose unique problems. The difficulty of removing the encapsulant while preserving the integrity of the die, bond pads, bond wires and lead frame interconnects on a small outline package pose a serious problem. A new sample preparation technique is offered in order to expose the front side and backside of the die. This technique dramatically reduced the risk of damage and ensures the functionality of the device after decapsulation.

Introduction In this paper, two sample preparation techniques for Small Outline Package (SOP) devices will be presented. The first technique is for front side sample preparation. A new procedure using a jet etching system decapsulation was developed specifically for small outline package devices. The encapsulant is removed while preserving the integrity of the die, bond pads, bond wires and lead frame interconnects. In addition, we will show a method to eliminate the need for repackaging for backside sample preparation. Both techniques allow the failure analysts to do front-side or backside analysis on any small package device.

Figure 2: Plastic small outline package on US nickel.

Sample preparation procedure (Front-side) One solution to the problem is to insert a second layer between the gaskets. An Aluminum strip was inserted between the gaskets before running the automated jet etching system. Removing the plastic to expose the die usually involves bending the leads out straight and using an automated jet etching system. A small window (about the size of the die) will be cut on the Al strip using a sharp stencil under the microscope. Once set, the software enables an entire etching program to be completed. This procedure includes the following four steps:

The Small Outline Package (SOP) is a low-profile rectangular surface-mount component package. Its chip is bonded to an inner land contact area (usually a lead frame). External terminals exit parallel to the seating plane on two opposite sides of the molded, flat package. SOP uses gull wing formed leads and is a surface mount package with a fixed lead pitch.

1. 2. 3. 4.

Figure 1: Cross-sectional view of a SOP device (Cavity up). CopyrightŠ 2006 ASM InternationalŽ

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Mounting the device in the position gasket. Placing with the Aluminum tape in order to define the area to be removed. Mounting the second gasket. Running the recipe from the automated jet etcher.


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