An Improved Cauer Model of IGBT Module: Inclusive Void Fraction in Solder Layer

The void in the solder layer is one of the most important aging forms of the insulated-gate bipolar transistor (IGBT) module. In this article, the influence mechanism of different void fractions on the thermal conductivity and specific heat capacity of the solder layer is studied. An improved Cauer model considering the void damage of the solder layer is established, and its model parameter extraction method is proposed. In addition, the temperature dependence of the Cauer model and its parameter is discussed in this article. In order to facilitate the experimental study of void damage in the solder layer, we customized IGBT modules with different void fractions. The influence of void morphology on the thermal properties of the solder layer is studied by the finite-element method, and the research purpose is to verify that void fraction can represent the effect of the voids on IGBT thermal characteristics. Considering the thermal resistance and thermal capacitance affected by the voids in the solder layer, their calculation methods are given in detail. Then, under different loads, the IGBT modules with different void fractions are tested. The robustness of the improved Cauer model is verified by the experimental and numerical simulation results. The results show that the improved Cauer model has higher accuracy than the traditional Cauer model.