Effect of rapid solidification on mechanical properties of a lead free Sn–3.5Ag solder

The melt-spinning processes of Sn–3.5Ag, Sn–3.5Ag–2In, Sn–3.5Ag–2Bi and Sn–3.5Ag–2Zn lead free solders were investigated and analyzed. The results showed that formation of intermetallic compounds of ɛ-Ag3Sn, In0.2Sn0.8 and AgZn embedded in Sn matrix phase, were produced during melt-spinning technique not found under equilibrium conditions. Addition of small amount (2 wt.%) In, Bi, or Zn refines the grain size, increases Hv, delay the fracture strength and improves creep resistance. The ternary alloys exhibits mechanical properties superior to that of the binary alloy Sn–3.5Ag because it has a uniform fine dispersion of precipitates and small effective grain size. It is found that in the lead free solder has composition of Sn–3.5Ag–2In, Sn–3.5Ag–2Bi and Sn–3.5Ag–2Zn melt-spun alloys, have eutectic composition which could be attributed to the shift of eutectic point under rapid solidification. The addition of indium, bismuth and zinc to the Sn–Ag binary system lowers the melting temperature.