Thermal Management and Experimental Validation of a Copper-Inlay PCB for SiC MOSFETs in High-Power EV Fast Chargers

Abstract

Efficient thermal management is essential to ensure reliability and performance in high-power electric vehicle (EV) fast-charging converters employing silicon carbide (SiC) MOSFETs. SiC MOSFETs are widely adopted in next-generation power converters due to their high efficiency, fast switching capability, and ability to operate at high temperatures. This paper presents an integrated thermal management strategy combining a copper-inlay printed circuit board (PCB) with a hybrid aluminum cold plate containing embedded copper pipes to improve heat spreading and SiC MOSFET die-to-coolant thermal performance. A complete analytical and simulation-based framework is developed to evaluate the thermal resistance of each layer in the conduction path, starting with the SiC MOSFET die, then the solder joint, copper inlay, thermal interface material (TIM), and cold plate, and finally the circulating coolant. The power-loss profiles of the SiC MOSFETs and diodes were calculated using analytical switching-loss and conduction loss models. Finite-element simulations in COMSOL Multiphysics quantify the internal temperature distribution and evaluate the impact of PCB configuration, TIM conductivity, and coolant flow rate on the SiC MOSFET die and package surface temperature. Results show that the copper-inlay PCB reduces thermal resistance by more than 30 percent compared to via-based boards, lowering the MOSFET package surface temperature from approximately 130 °C to 102 °C under identical power dissipation. Parametric analysis demonstrates that selecting an optimized TIM conductivity of 5 W/(m·K) and a coolant flow rate of 1 GPM reduces the SiC MOSFET die temperature from 102 °C to about 41 °C. Experimental validation using a fabricated prototype showed strong correlation with simulation results in terms of spatial temperature distribution and hotspot locations, confirming the accuracy of the thermal model. The proposed multilayer copper-inlay and cold-plate configuration provides a compact, reliable, and scalable thermal solution for next-generation SiC-based high-power EV fast-charging converters.