High Reliability and Low Thermal Resistance Spacer Based on Via-DPC for Double-Side Cooling Module

The double-sided cooling (DSC) power modules are sandwich packaging with more soldering interfaces, which suffer higher thermal-induced stress than traditional wire-bonding packaging. Considering reliability and thermal conductivity, state-of-the-art spacers were implemented as a buffer to lower the stress. This article introduced a spacer made of direct-plated copper (DPC) with vias to reduce the thermomechanical stresses in the DSC power module. The DPC-via-spacer (DVS) consists of AlN ceramic with close CTE to SiC devices and copper layers with stress-strain relieved edge design. Single-switch DSC modules with copper spacer, molybdenum spacer, and DVS were designed and fabricated. Simulation results showed that, at a power loss of 90W, the thermally induced strain at the most vulnerable solder layer of the module with the DVS was reduced by 80% compared to that of the module with the copper spacer. Compared with the Mo spacer, the junction temperature is reduced by 4% under a similar stress-strain behavior. Considering skin effect under 500MHz frequency, the electrical resistance of the DVS is 92.6% and 50.5% of that of the copper spacer and the Mo spacer, respectively. Power cycling test results showed that the lifetime of the modules with DVS is 50% and 20% longer than that of the modules with copper spacer and Mo spacer, respectively. The results prove that DVS can reduce the thermomechanical stress-strain on the solder layer and enhance the reliability of the power module.