Strategy for designing accelerated aging tests to evaluate IGBT power modules lifetime in real operation mode

Abstract

Accelerated aging tests are widely used in electronics industry to validate the technological choices of packaging, especially when significant lifetime is required. The thermal coefficient of expansion mismatch between the soldered materials results in crack propagation in the solder joints, which irreversibly increases the thermal resistance of the assembly and progressively leads to the failure of the module. Accelerated testing is very expensive and can last a long time, so that such experiments must be optimized. In addition, thermomechanical behavior of the assembly under realistic operating conditions for long times can be studied in shorter times thanks to finite element simulations. Non-linear finite element simulations have been carried out to make a correlation between accelerated aging tests and real operation. Stress-strain history under representative thermal loading has been determined in both cases. The energy dissipated in solder joints has been calculated and has been used as an estimator of the damage in the solder joint. Finally, thermal fatigue experiments with representative samples have allowed validating the previous results. This study is a step toward the understanding of the correlation between accelerated testing and actual operating conditions.