A Fully Coupled Model of Multi-Chip Press-Pack IGBT for Thermo-Mechanical Stress Distribution Prediction

In this article, a fully coupled multiphysical model of multichip press-pack insulated gate bipolar transistor (PPI) considering surface roughness is proposed. This model realizes the coupling of the electrical-, thermal- and mechanical domains through contact resistance. The simultaneous prediction of temperature and stress under various surface roughness is achieved. First, the fully coupled model and the contact resistance model are established. Second, both thermomechanical stress under the clamping phase and heating phase are analyzed. The influence of the surface roughness on the thermo-mechanical stress distribution is also investigated based on the proposed model. Results show that the surface roughness does not affect the thermomechanical stress distribution under the heating phase, while the amplitudes increase with surface roughness. Third, the correctness of the model is verified by the temperature measurement and deterioration observation results. The observed fretting scratches on the additional metallization area after the power cycling test validates the correctness of the deformation prediction. Finally, the strain-life fatigue model of PPI is established, it turns out that the surface roughness has an impact on the fatigue life of the chip metallization area.