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|BGA Life Prediction under Combined Temperature and Power Cycling|
|Keywords: solder reliability, combined temperature and power cycling, damage superposition|
|Life time of electronic products is limited by a set of competing failure mechanisms brought on by their use and surrounding environment. Solder interconnect failure is a known life limiting failure mechanism that is driven by repeated temperature excursions. Thermal fatigue reliability of solder interconnections is conventionally assessed by simple temperature cycling tests, which apply a constant temperature range, fixed dwell times and ramp rates during the test. From these tests, fatigue models have been developed to predict life expectancy of solder joints. However, under on and off cycles, non-constant work loads, and changes in surrounding environment, electronic devices are not subjected to simple temperature cycling during their life. To address complex cycles, Miner's rule has been applied. While this approach has been accepted for tin-lead solder, the acceptability for use with lead-free solders must be examined. A combined temperature and power cycling test was conducted on Plastic Ball Grid Array (PBGA) packages. Using the Engelmaier model, the cycles to interconnect failure were predicted by applying the linear superposition. Modeling approaches included characterizing the resultant complex temperature profile, dividing the complex temperature cycle into multiple simple cycles (with constant ΔT), assessing the simple cycles and applying Miner's rule. Model predictions were compared with test results. The segmentation of complex temperature cycle was found to impact the accuracy of the prediction.|
|Fei Chai, Research Assistant
CALCE, University of Maryland
College Park, MD