Packaging and characterization of silicon and SiC-based power inverter module with double sided cooling

Thermal management and especially cooling attracts more and more attention during phases of conception and fabrication of power modules to increase their field operation time and/or power density. Indeed thermal power losses impact the reliability of power systems, which are in a same time converging towards always higher power density and performances. Since standard solder die attach and wire bonding are reaching their limits, a novel concept of assembly has been realized with double sided cooling (DSC), as fully integrated part of the power module. Half-bridge modules either based on IGBTs and silicon diodes or based on SiC-devices have been assembled by combining Transient Liquid Phase Bonding (TLPB) and Transient Liquid Phase Soldering (TLPS). SiC and silicon wafers were prepared by deposition of a high density area array of Cu posts. In order to switch 1200V / 25A copper posts were electroplated 80 μm in height with a thin tin cap for flip chip bonding by TLPB. To attach a second DCB substrate on the backside, a TLPS paste was used. All interconnects of the modules are formed by intermetallic bonds for the target purpose of increased capability in heat dissipation, improved reliability and higher operation temperatures. Results on fabrication, thermal characterization and active power cycling (ATj = 125 K) are here also reported.