Power Cycling Performance of 3.3 kV SiC-MOSFETs and the Impact of the Thermo-Mechanical Stress on Humidity Induced Degradation

Recently, silicon carbide (SiC) power modules of the 3.3 kV voltage class became available and are a promising candidate to replace silicon power modules in traction applications. However, the more than three times higher Young’s Modulus compared to silicon leads to a reduced lifetime under thermo-mechanical stress. This could pose a significant obstacle in their implementation, since traction applications are particularly demanding in their mission profiles with respect to load cycling, but also to environmental conditions. Thus, the thermo-mechanical stress is not just limiting the lifetime itself, but might also promote the humidity induced degradation due to delamination or micro-cracks. In this work, multiple power cycling tests at different temperature swings on 3.3 kV SiC MOSFET chips in a power module were performed, to assess their ruggedness under thermo-mechanical stress. Before or afterwards, these modules were tested under standard HV-H3TRB conditions to verify the interaction between thermo-mechanical and humidity stress on the robustness of the modules.