Microstructures and properties of Bi-11Ag solder doped with small amounts of Sn

In this paper, the Bi-11Ag solders with additions of 1wt.%, 3wt.%, and 5wt.% Sn are prepared to investigate the microstructure, melting characteristic, and tensile strength of the solder joint. The result shows that the melting temperature decreases to 154 °C as the Sn continuously added; the microstructure was refined when the addition of Sn was below 5wt.%, as it reach 5wt.% or more, the dendritic microstructure become coarse; tensile strength jumped to 43.3MPa from 53.9MPa with the addition of Sn. It is because that the Sn diffuses to the interface and then forms the Ag
₃
Sn intermetallic compound(IMC) layer, it is significantly superior to the mechanical bonding formed by grain boundary groove in the case of without Sn.