Evaluation of Fatigue Life of Semiconductor Power Device by Power Cycle Test and Thermal Cycle Test Using Finite Element Analysis

摘要

To accurately predict the fatigue life of a power device, a fatigue life evaluation method that is based on the power cycle is presented in terms of an algorithm based on a combination of electrical analysis, heat analysis, and stress analysis. In literature, the fatigue life of power devices has been evaluated on the basis of the thermal cycle. This cycle is alternately repeated within a range from a high temperature to a low temperature. In an actual operating environment, however, a power device works in a power cycle that consists of being switched ON and OFF. To accurately predict the fatigue life cycle of a device, then, the evaluation should take account of this important aspect of the power cycle. To verify the utility of the evaluation method presented in this study, the results for a power cycle based on the combined use of electrical analysis, heat analysis, and stress analysis are compared to the results based on the thermal cycle, as found in the literature. Our conclusion is that the fatigue life cycle as estimated by the thermal cycle test is higher than that estimated by the power cycle.