Effects of different fluxes on the characteristics of Sn-Zn solders

The wetting characteristics of Sn-Zn solders with three different types of flux were researched by wetting balance method. Results indicated that Sn-Zn solders exhibited excellent wettability using ZnCl2-NH4Cl flux. Additionally, the spreading of Sn-9Zn solder on Cu substrate with different types of flux was investigated, and the characteristics of the intermetallic compounds (IMC) between the solder and substrate were also analyzed and compared, results showed that a flat IMC layer was present adjacent to the Cu substrate while a scallop IMC layer was close to the solder. Moreover, the characteristics of IMC and the appearances of soldered joints varied by using different fluxes. Plenty of ZnO exists on the surface of Sn-Zn solders, thus removing the ZnO is critical for the flux of Sn-Zn solders.