A Benchmark Study on the Thermal Performance and Life of Different Structures of SiC Chip Modules

Five typical power modules with an SiC chip, which have actually been developed by automobile industry, were investigated by using finite element analysis (FEA). The main differences in these structures are single side cooling or double side cooling, insulation structure with direct bonded copper (DBC) or resin sheet, and Ag sintering or soldering joint. Furthermore, in single side cooling, the bonding material of heat sink is Ag sinter or silicone grease, and in double side cooling, there are one or two layers of copper sheet at the top and bottom respectively. The authors have studied the thermal performance and reliability of these modules. Firstly, the thermal performance of each module was compared by the maximum junction temperature T
jmax
when the same power cyclic test (PCT) conditions were applied to the modules. Based upon the analytical results, it has been confirmed that the designs of insulation structure, heat spreader and the bonding materials of the heat sink give big impact to the T
jmax
. The cooling structure is another important factor to the thermal performance.Based upon the PCT analytical results, the nonlinear strain in each joint layer was compared. It was found that the bonding materials of the heat sink is the key factor to improve the reliability.