Liquid-Cooled GaN and SiC Power Modules for Electric Vehicles

Advanced packaging of power modules is very important. Packaging optimization is one of the solutions to improve performance. WBG devices have higher power density than Si devices and require better thermal design considerations to maintain optimal working conditions. For example, changing the package type from SO-8 to LGA can improve power loss.

Recently, the 9th International Third Generation Semiconductor Forum (IFWS) & the 20th China International Semiconductor Lighting Forum (SSLCHINA) were held in Xiamen. During the "3rd Automotive Semiconductor Innovation Cooperation Summit", Professor Wu Weidong of the University of Toronto, Canada, gave a keynote speech on "GaN and SiC Liquid Cooling Power Modules for Electric Vehicles" and shared relevant research progress. It involved assembly processes, thermal and electrical considerations, three-dimensional stacked output stages, design examples, etc.

The report points out that power converters for electric vehicle applications require effective heat dissipation through liquid cooling. Liquid coolers and power modules are usually designed independently by automotive parts and semiconductor manufacturers, which may lead to inefficient thermal channels. An alternative manufacturing process for compact GaN intelligent power modules (IPMs), an all-in-one design, connects the IPM directly to the liquid cooler. For liquid-cooled power modules (typical design process), traditional liquid-cooled power modules are usually manufactured independently, and semiconductor manufacturers responsible for other packaging processes are not involved. In the future, a joint design approach is needed to optimize the thermal performance of liquid-cooled power modules.

The report introduces custom-designed liquid-cooled power modules, module manufacturing process flow, typical test setup, typical PCB applications, thermal considerations of power modules, thermal analysis-finite element analysis simulation, design examples-double-sided stacking, double-sided stacking components (3D view, power loop), the impact of parasitic inductance of power loops, etc. The report points out the challenges of module design based on WBG devices, involving electrical performance (small system volume) and thermal performance design (large system volume). In terms of vertical power module design, it involves the temperature distribution of power modules based on VDMOS and the efficiency of vertical power modules and thermal imaging images under the infrared camera lens.

The report points out that joint design based on mechanical, electrical and thermal considerations must be carried out from the beginning. The placement/geometry of AMB and WBG power transistor die affects the trade-off between thermal and electrical performance. Wider spacing provides better thermal performance, but at the expense of electrical performance degradation. Future research will continue to explore different AMB materials and packaging structures, and continue to explore cost-effective liquid-cooled packaging with excellent thermal management and electrical performance.