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Sn–5wt%Sb is one of the materials considered for replacing Pb-bearing alloys in electronic packaging. The creep tests were conducted to investigate the effect of the heat treatments on the mechanical properties of Sn-5wt%Sb lead-free solders. Samples were heat treated at temperatures of 313, 333 and 353 K to produce a range of different grain sizes. Tow-load creep tests were carried out at each temperature for the wire samples to alloys. The results obtained show that there is a relationship between the heat-treatment temperature and the microstructure and that this, in turn, affects the creep properties of the alloys. From the steady state creep rate the stress exponent is described in terms of the heat treatment temperatures. The stress exponent (n) were determined to clarify the deformation mechanism. Based on the n values, it is suggested that the rate controlling creep-deformation mechanism is dislocation climb. Comparisons are made with all alloys on the creep resistance of solder alternatives. The effect of annealing temperature against the strain rate indicated that in increasing annealing temperature, the strain rate is increasing, might be due to the increasing in the grain size. This study revealed that the solder alloy Sn–5wt%Sb have the potential to give a good combination of higher creep resistance and rupture time.