Achieving Low Thermal Stress in a PCB/AMB Hybrid SiC Power Module Using Fluidic Connections Based on Liquid Metal

Due to the mismatch of coefficient of thermal expansion (CTE) among different material layers, power modules are usually under substantial thermomechanical stress during operation. This problem becomes more significant for silicon carbide (SiC) power modules because the Young’s Modulus of SiC crystal is very high. To tackle this problem, this paper utilizes liquid metal (LM) as the interface material inside a PCB/AMB hybrid SiC power module. The LM layer not only acts as a thermal interface material, but can also conduct the drain current of the device. Compared with solder which is a rigid connection, LM is a fluidic material that can decouple the strain between the die and the AMB substrate while maintaining the thermal and electrical connection. FEA simulations show that the thermal stress caused by the mismatch of the CTE is reduced by 83%. Sample modules are fabricated and tested, revealing that the LM connection can provide the same electrical and thermal performance as solder. This article reveals the potential of using fluidic interconnection inside SiC power modules, providing a new solution to improve their reliability without adding complexity and cost.