A Way to Reduce Leakage Current and Improve Reliability of Wire-Bonds for 300-A Multichip SiC Hybrid Modules

In this article, pressureless sintering of nanosilver paste is proposed to enhance the reliability of wire-bonds with SiC chips by both alleviating thermomechanical stresses and enhancing thermal coupling of bonding wires and chips. A multichip 1200-V/300-A SiC hybrid module with six Si IGBTs and 12 SiC Schottky barrier diodes (SBDs) is demonstrated. The lifetime of the wire-bonds with the SiC SBD bonded by the pressureless sintered nanosilver is ~27.9% longer than that by the high-temperature solder under power cycling with constant temperature swing. The lifetime of the wire-bonds with the IGBT also bonded by the pressureless sintered nanosilver is ~46.2% longer than that by the high-temperature solder under power cycling with constant conduction current. Furthermore, not only the cost of 1700-V SiC SBDs is quite similar to that of 1200-V ones but also the leakage current of the 1200-V/300-A SiC hybrid module can be reduced greatly using 1700-V SiC SBDs as free-wheeling diodes instead of the regular 1200-V ones. Considering the much larger leakage current of a SiC SBD compared with that of a Si p-i-n diode. It is feasible to use a SiC SBD with higher blocking voltage to reduce the significant leakage current of the free-wheeling SBD with almost no cost increase.