Lifetime Modeling of SiC MOSFET Power Modules During Power Cycling Tests at Low Temperature Swings

The goal of this work is to assess the power cycling performance of silicon carbide MOSFETs at low temperature swings and investigate the previously reported discrepancy between common lifetime model and power cycling test results. Additionally, the impact of the minimum temperature on the power cycling performance was examined. For this purpose, power cycling tests with temperature swings between 40 K to 100 K and at minimum temperatures of 20°C and 40°C are performed. The results confirm, that the lifetime of SiC MOSFETs is significantly underestimated at low temperature swings by state-of-the-art lifetime models, when the model is fitted to power cycling test results at high temperature swings, which is in agreement with previous reports. Furthermore, the test results suggest that the discrepancy increases even further towards lower temperature swings, which can be modeled by a change of the Coffin-Manson exponent at a threshold temperature swing. This could be a possible indication of the transition from plastic to elastic deformation as the prevalent fatigue mechanism. Moreover, the tests at different minimum temperatures show a significantly higher impact of the baseline temperature on the lifetime at low temperature swings compared to high temperature swings. This may indicate that the threshold temperature swing for the transition from plastic to elastic deformation is impacted by the minimum temperature.