About peritectic Sn-5Sb free solder alloy has encountered major attention for high temperature electronic applications, particularly on step soldering technology, flip-chip connection. In the running work, a small addition of quantity of Ag and Cu were combined to Sn-5Sb solder alloy to study the effect of a third element combination on the microstructural, thermal and mechanical properties. The study shows that the superplasticity of Sn-5Sb solder is reduced by Ag and Cu additions. The stress-strain curves gained were highly dependent on strain rate and temperature. More strain rates gave more stress-strain curve and more strain at fracture. The tensile manner of the alloys is strain rate and temperature dependence. Stress-strain characteristics of the Sn-5Sb binary, Sn-5Sb-1Ag and Sn-5Sb-1Cu ternary alloys were investigated at various strain rates (SR, ε·) from 5.56×10^-4 to 1.26×10^-3 s ^-1 and deformation temperatures from 303 to 403 K. Addition of 1Ag, and 1Cu to the binary Sn-5Sb alloy raised the yield stress σy, the ultimate tensile stress (UTS), and ductility (total elongation εT ). Increasing the strain rate (ε· ) increased both σy and (UTS) according to the power law σ =Cε·m. A normal decrease of total elongation εT with strain rate (ε· ) was observed according to an empirical equation of the form εT =Aexp(-λε· ); A and λ are constants depending on the experimental condition. The results gained were explained in terms of the difference of the interior microstructure in samples. The Ag and Cu addition refines the microstructure, enhancing the mechanical properties, and form new intermetallic compounds (IMCs).