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Accelerated Temperature Cycle Test and Coffin-Manson Model

Accelerated Temperature Cycle Test and Coffin-Manson Model

Accelerated Temperature Cycle Test and Coffin-Manson Model

for Electronic Packaging

Helen Cui, RF Micro Devices

Key Words: Accelerated Reliability Testing, Temperature Cycle, Coffin-Manson Model, Activation Energy

SUMMARY & CONCLUSIONS

Temperature cycle profiles at various stress levels were investigated for accelerated reliability testing of electronic device packaging. Failure Analysis was conducted for test failures to determine their root cause failure mechanisms and failure modes. Weibull analysis was conducted for failures with the main failure mechanisms (such as solder fatigue, mechanical cracks). The Coffin-Manson model has been used to model crack growth due to repeated temperature cycling. A good correlation was obtained between the Coffin-Manson model and the test results, and Activation Energy (EA) was determined. The limitation and application of the Coffin-Manson model are further discussed.

The main failure mechanism determined by failure analysis was Via Cracking in the package substrate. The acceleration factor between different stress levels was determined by Weibull analysis of test data. The Coffin-Manson model was used to correlate the test data and determine the activation energy related to via crack failure

mechanism. The Coffin-Manson model with determined

Activation Energy could be used to estimate product reliability

Accelerated Temperature Cycle Test and Coffin-Manson Model

under different application conditions for the same main failure mechanism.

1. INTRODUCTION

Today’s electronic packaging continues to shrink in size

and reaches higher packing density and higher reliability.

Accelerated test is needed to save test time and cost and reduces cycle time to market. Various temperature cycling

profiles are employed to evaluate the effect of stress on life

and to detect the unknown failure modes. The temperature cycle profile can be characterized by • High extreme temperature (Tmax ), • Low extreme temperature (Tmin ), • Temperature change ∆T, ∆T = Tmax - T min • Ramp rates, • Dwell times at extreme temperatures. Figure 1 shows a schematic of temperature cycle profile. Product life could be significantly affected by the maximum temperature (Tmax ) the temperature change (∆T) dwell time and ramp rate. The larger of Tmax , ∆T, dwell time, and ramp rate indicate the higher stress level. Temperature Cycling tests are used to characterize product capability and to detect unknown failure modes (e.g., die crack, via crack) during technology development, product design verification, and product qualification. Often, the stress level of the test temperature profiles far exceeds the product field application stress level. This leads to accelerated test. Test results at the high stress level need to be extrapolated to the low stress level, i.e., field application stress level. It is critical that the main failure mechanism remains

the same for the high stress level and low stress level. For new technology (or designs for which the field failure mechanisms are unknown) it is critical to conduct failure analysis to determine root cause failure mechanisms and failure modes.

Figure 1 Temperature cycle profile schematic

In this study, a 6mm x 8mm electronic packaging module with three die was tested with variety of temperature cycling profiles for accelerated tests. Via cracking was verified through temperature cycle tests. Weibull analysis was conducted on failures corresponding to the via crack failure

Temperature ∆T

Accelerated Temperature Cycle Test and Coffin-Manson Model

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