A Multi-Layer RC Thermal Model for Power Modules Adaptable to Different Operating Conditions and Aging

Semiconductor devices are often the most vulnerable components of power electronics converters among which thermal failures are the most likely ones. Thus, more accurate but straightforward thermal models are needed to efficiently do actions such as lifetime prediction, thermal management, etc. This paper presents a Foster-type equivalent transient thermal model developed through finite element simulations for a commercial Si IGBT power module. Such thermal models can easily merge into circuit simulation programs and even can be employed as real-time temperature estimators. However, fixed thermal models may give large errors in different operating conditions. In addition, they become unable to satisfactorily estimate temperatures over time, because of the thermal aging phenomenon. Thus, in this study, the thermal model of the power module is developed to be adapted to different boundary conditions - ambient temperature, and cooling system – as well as thermal aging of solder joints, which is the most common failure in the power modules. Also, the thermal model features the effect of power loss, and the cross-coupling effect among nearby semiconductor dies. Comparisons with FEM verify the performance of the studied thermal model.