Reliability of SiC MOSFET with Danfoss Bond Buffer Technology in Automotive Traction Power Modules

This paper describes reliability investigations in terms of power cycling tests for a new generation of top-side sintered or soldered 1200 V silicon carbide (SiC) MOSFETs for use in an advanced power module, designed for operation with 800 V bus voltage in electric vehicle drive trains. The MOSFETs were packaged with different bonding and joining technologies. A power module assembly technique using sintered SiC MOSFETs interconnected with a sintered copper (Cu) foil and attached Cu wires was compared with both soldered and silver sintered die bonding combined with bonded aluminum (Al) wires to evaluate the reliability of three different techniques. Compared to the Al wire bonded assemblies with lift-off or solder degradation as the type of failure, heavy Cu wires with Danfoss Bond Buffer(r) (DBB(r)) on SiC achieved a significant increase in power cycling capability compared to traditional soldered packaging techniques. A shift in failure mechanism away from the interconnect technologies and towards a chip top metallization degradation was detected.