Influence of the clamping force on the power cycling lifetime reliability of press pack IGBT sub‐module

Abstract

The clamping force is the most important parameter of Press Pack IGBTs (PP IGBTs) as it not only affects the electrical, thermal, and mechanical characteristic, but also the long lifetime reliability. Too little clamping force increases the contact resistance and junction temperature. Too much clamping force makes the silicon chips mechanical damage. However, it is quite complex and time-consuming to obtain the influence of the clamping force on the long-time reliability through the power cycling test because that many tests are needed to execute under a large range of clamping forces. Here, a single IGBT chip sub-module is proposed to simulate the long lifetime reliability through the finite element method under various clamping forces. Both the thermal contact resistance within different contact interfaces that affects the junction temperature of silicon chips a lot and the elastic-plastic model that affects the lifetime of specific material layers are considered in this finite element model to make it more accurate. The combination of Coffin–Mason and Basquin model is proposed to obtain the power cycling lifetime of the sub-module based on simulation results. A clamping force range is obtained and this also gives a guideline for the power cycling test.