Distributed Thermal Modeling for Power Devices and Modules With Equivalent Heat Flow Path Extraction

Dynamic temperature information at critical locations has been a critical indicator to safely use power devices and modules; however, most of the existing 3-D thermal modeling methods are time-consuming and complicated, which seriously limits their application in practical temperature distribution estimation. Assisted by finite-element method (FEM), the proposed distributed thermal model takes the cross-coupling effects into account among multiple heat sources. Based on the extracted equivalent heat flow paths from FEM steady-state thermal simulations, a novel method of extracting thermal resistance and thermal capacitance ( $RC$ ) is presented for yielding temperatures at critical positions. More importantly, FEM and experimental results successfully prove the effectiveness of our proposed distributed model in accurately simulating the temperature distribution information for different monitoring points on a single chip, as well as different chips in a power module. Compared with prior-art 3-D thermal modeling methods, the time cost to establish our model is considerably lowered as the transient temperature responses and thermal impedance matrix are no longer required. Meanwhile, reduction in the number of $RC$ parameters simplifies the identification process, which further improves the practicability and generalization ability of the proposed distributed thermal model.

I. Introduction

With the outstanding performance in switching transients [1], [2], IGBTs and SiC MOSFETs have been widely used in many important realms [3], [4], [5]; however, the harsh operating environment accompanied by extreme operating conditions render them one of the most vulnerable parts that mainly undermine the reliability of power conversion equipment. Relevant research indicates that over half of power device failures result from a high junction temperature swing [6]. As a result, it is essential to accurately estimate IGBT or SiC MOSFET module temperature information for the purposes of thermal management and condition monitoring of entire power conversion systems.