Heat Sink Effects in Power Module Design: Multiphysics Simulation with Multiple Heat Sources

Abstract

With the rising demand for electric vehicles, manufacturers must develop more reliable, higher-power modules to meet stringent longevity and performance requirements. Consequently, multiple power modules often share a single liquid-cooling channel. However, most studies focus on package-level thermal management under idealised boundary conditions, overlooking the significant inlet-to-outlet temperature gradient brought by the heat sinks. This study employs a multi-physics simulation of a complete water-cooled heat sink with small elliptical pins, comprising two active metal brazed (AMB) substrates each bearing silicon carbide MOSFET chips. Water is used as the coolant. The simulation examines the temperature and stress distributions under different input power conditions. The results show that the detailed heat sink model captures a pronounced inlet-to-outlet temperature gradient which, in turn, induces non-uniform strain distribution within the solder layers—especially at the interfaces between the AMB substrates and the heat sink casing. Under high-power cycling, these stresses are significantly amplified, thereby increasing the risk of delamination and premature failure. In contrast, simulations employing an idealised cold plate boundary condition fail to reveal these critical phenomena. Overall, the findings underscore the necessity of integrating comprehensive thermal and mechanical analyses into the design process, thus enabling the optimisation of thermal management strategies for high-power semiconductor modules in next-generation electric vehicle applications.