Cold Atmospheric Plasma Metallization of Power Semiconductor Devices with CuSn Pseudo-Alloys for Diffusion Soldering

Cold atmospheric plasma spraying is used to produce thin coatings of copper and tin between 20-80 μm thickness for use in diffusion soldering. This study presents an alternative process to apply composite solders directly onto power electronic bare dies. The formation of intermetallic phases may be promoted by the homogeneous distribution of the Cu and Sn particles as they are presented not in a layered structure but as a pseudo alloy within the coating. The Cu and Sn powder is mixed in situ using two powder conveyors, enabling adjustable mix ratios. The presented approach has been shown to produce a homogeneous particle distribution within the coating. Furthermore, preliminary experiments indicate the feasibility of the technology for applications in diffusion soldering.