Optimized thin-film diffusion soldering for power-electronics production

This paper gives an overview on diffusion soldering or transient liquid-phase soldering (TLPS), where the conventional electronic production processes have been optimized for being capable of producing highly durable pore-free TLPS bonds. The growth of intermetallic phases (IMP) with control of temperature and time has been investigated in production line perspective. The samples processed under optimized vacuum based vapor-phase soldering along with realization of thin solder layers down to less than 10μm are demonstrated. As a result, pore-free diffusion soldered joints filled with Cu₆Sn₅ and Cu₃Sn phases near the chip-substrate interface have been realized. Formations of IMP with changes in optimized solder profile, solder paste, chip metallization, substrate roughness and solder paste thickness are discussed.