Highly variable Sn-Cu diffusion soldering process for high performance power electronics

A Sn-Cu-based diffusion soldering process is presented that is capable of producing high temperature resistant joints for small area dies, like MOSFETs as well as for larger IGBTs and even large area baseplate or cooler-contacts. It is shown how the lateral infiltration process, needed to produce these joints, is influenced by the choice of the respective Cu-paste system. Furthermore, materials analysis on bulk material samples, including tensile testing, metallography and fracture analysis, show how the choice of paste system also affects the microstructure and hence the mechanical behavior of the bulk material. First results from power-cycling investigations on one of the selected paste-systems show a more than tenfold increase of lifetime compared to a SnAgCu305 solder reference.