Interfacial reaction and growth behavior of IMCs layer between Sn-58Bi solders and a Cu substrate

This paper reports on the interfacial reaction and growth behavior of intermetallic compounds (IMCs) layer (eta-Cu6Sn5 + epsilon-Cu3Sn) between molten Sn-58Bi solder and Cu substrate for various liquid-solid soldering temperatures and times. In addition, the Bi segregation at the Cu3Sn/Cu interface was also discussed, too. It was found that the Cu6Sn5 IMC could be observed as long as the molten solder contacted with the Cu substrate, while the Cu3Sn IMC was formed at the interface between Cu6Sn5 and Cu substrate as the higher soldering temperature and/or longer soldering time were applied. Both thickness of total IMCs layer and Cu6Sn5 grains size increased with increased soldering temperature or time. The growth of the Cu-Sn IMCs layer during soldering exhibited a linear function of the soldering temperature and 0.27 power of soldering time. With soldering temperature increasing (above 280 A degrees C in this present study), Bi was accumulated at the Cu3Sn/Cu interface and resulted in some isolated Bi particles were formed.