Frequency-Domain Thermal Coupling Model of Multi-Chip Power Module

Abstract

The high-power density design of the IGBT power module may lead to complicated thermal behaviors, and the thermal-coupling effect among multiple chips is a major focus in the field of thermal modeling and characterization. Unfortunately, the existing modeling methods simply describe thermal coupling effect as a superposition of temperatures caused by lateral thermal diffusion. In reality, it is not only the temperature of semiconductors which is important but also of the heat flow characteristics in heat transfer process. In this paper, the thermal coupling effect has been explained in another perspective that it is the result of the overlap between heat flow paths. Frequency domain analysis of heat flow has been first conducted by FEM simulations, and a novel thermal model considering the heat flow coupling has been proposed. This approach focuses on the thermal modeling of the heat coupling effect in cooling system and greatly simplifies the thermal modeling of the heat coupling effect inside power module because it has been discovered that the coupling region is mainly contained in the section from the baseplate to the heatsink. As a result, the proposed method has the advantage of not only having some physical meaning, but also having a relatively simple modeling and characterization process when compared to existing methods. The proposed thermal coupling model is verified by both simulation and experiment, and the application for electro-thermal simulation of electric machine drive complex mission profiles composed of multi-timescale thermal dynamics is also provided.