Power Cycling Modeling and Lifetime Evaluation of SiC Power MOSFET Module Using a Modified Physical Lifetime Model

This study aims to explore the solder fatigue lifetime of a developed high-voltage (1.7 kV/100 A) SiC power MOSFET module for on-board chargers (OBCs) subjected to power cycling test (PCT) in accordance with AQG 324. To achieve this goal, a design for reliability (DfR) methodology is established, which couples three-dimensional (3D) thermal computational fluid dynamics (CFD) analysis with 3D transient thermal-mechanical finite element analysis (FEA). The time-dependent viscoplastic behavior of the solder layer is taken into consideration in this FEA by virtue of the Anand model. In addition, a modified physical fatigue lifetime model based on Coffin-Manson formula considering the correlation between a failure criterion and a physical damage characteristic is proposed to effectively estimate the solder fatigue lifetime. The coefficients of the modified physical lifetime model are derived by curve-fitting the experimental solder fatigue lifetime data of a commercial 1.2 kV/25 A SiC power MOSFET module and the corresponding calculated equivalent strain increments using the DfR methodology. The proposed DfR methodology together with the constructed fatigue lifetime model are tested on the prediction of the solder fatigue lifetime of the developed high voltage SiC power module, and their validity are demonstrated by comparing the predicted results with the corresponding PCT experimental results. Finally, parametric analysis is performed to seek a design guideline for enhanced solder fatigue lifetime of the developed SiC power MOSFET module.