Heat cycle failure point prediction by 3D thermal stress analysis for medium voltage power module

The structural optimization of power modules for reliability can be performed without physical prototyping if the structural weakness in modules can be assessed on a 3D model. In this study, 3D thermal stress simulation is investigated as a predictive tool for the heat cycle test (HCT) failure point of the medium voltage power module. The module has a multilayer structure of two different ceramics (A1203 and A1N) to reduce the parasitic capacitance. In this complex structured module, the failure point of actual test samples are shown to coincide with weakness points of the thermo-mechanical stress in the 31) simulation. The heat cycle test (125/-40 degrees C) was used for simulation and testing. The failure point of the module was predominantly copper delamination from the A1N substrate surface after HCT 100 cycles. The delaminated locations were matched to points in the simulation that has 2 characteristics, high peeling stresses points and high shape deformation of copper pattern at the simulation results. This observation applies to copper patterns only connected to the ceramics, while copper patterns connected to other adjacent layers did not follow this trend.