Thermal Coupling Affected Power Cycling Lifetime of the 6.5 kV IGBT Module

High-voltage and high-power IGBT modules typically include both IGBT and FRD chips in parallel. As the power level increases, the thermal coupling between the IGBT and FRD chips in the module is very serious, affecting the module's reliability. However, in power cycling test, only the reliability of IGBT chips is considered by heating the IGBT chips, while the influence of the thermal coupling between IGBTs and FRDS on the reliability of IGBTs is ignored. To investigate the effect of thermal coupling between IGBT and FRD chips, the power cycling tests (PCTs) on IGBT and FRD chips in the same 6.5 kV module are alternately conducted in this paper. The test results show that the IGBT lifetime is reduced by 30.94% affected by FRD thermal cycling and the FRD lifetime is reduced by 46.65% affected by IGBT thermal cycling.