Highly reliable high-temperature superplastic Al-Zn eutectoid solder joining with stress relaxation characteristics for next generation SiC power semiconductor devices

A new high-temperature lead-free solder joint which withstands temperatures up to 300°C and utilizes superplasticity in an Al-Zn eutectoid alloy has been developed to realize SiC power semiconductor devices. The joining process consists of interfacial cleaning of the joint formed utilizing superplasticity of the Al-Zn-eutectoid alloy at 250°C followed by bonding in the solid-liquid coexisting temperature range in order to control microstructures and to reduce occurrence of voids. The developed SiC/SiN substrate joints with void-free and stress relaxation effects show outstanding reliability in temperature cycle tests from −40°C to 300°C for 5000 cycles.