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

Abstract

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 Ag3Sn intermetallic compound(IMC) layer, it is significantly superior to the mechanical bonding formed by grain boundary groove in the case of without Sn.