Microstructure and properties of Sn-Zn-Bi-(P,Nd) lead-free solders

Microstructure, mechanical properties, oxidation resistance and wettability of Sn-8Zn-3Bi lead-free solder doping with P and Nd were studied in this paper.Primary Zn phase was observed in the microstructure of Sn-8Zn-3Bi alloying with separate P element.By adding P together with Nd not only the formation of the primary Zn phase can be inhibited, the massive microstructure of the solder also can be refined.It was the reason that the solder plastic improved, and the elongation reached 48%.P element in solder melts was apt to loss in the process of long term heating.A diffusion barrier layer could form at the surface of the Sn-8Zn-3Bi solder by doping with P and Nd, which reduced the loss of P, and the oxidation rate decreased as well.With the improved oxidation resistance, the Sn-8Zn-3Bi-0.1P-0.05Nd solder showed high wetting performance.