Effects of soldering temperature and cooling rate on the as-soldered microstructures of intermetallic compounds in Sn-Ag/Cu joint

The as-soldered microstructures of intermetallic compounds (IMC) in Sn-Ag/Cu joint were investigated under different soldering temperatures and cooling rates. Scalloped, faceted, prismatic and hexagonal shape Cu6Sn5 grains were observed at the solder/Cu interface, respectively. Scalloped shape grains were found at 250°C. At higher soldering temperatures such as 275 °C and 300°C, faceted grains were dominant and the other two were mainly discovered under smaller cooling rates. Simultaneously, large plate-like Ag3Sn formed in virtue of interfacial Cu6Sn5 under furnace cooling, which was discussed based on the solidification sequence.