Indentation creep study of lead-free Sn–5%Sb solder alloy

Abstract

Creep behavior of the lead-free Sn–5%Sb solder alloy in the cast and wrought conditions was investigated by long time Vickers indentation testing under a constant load of 15 N and at temperatures in the range 298–405 K. Based on the steady-state power law creep relationship, the stress exponents were determined for the cast and wrought materials. These exponents, depending on the testing temperature, were in the range 4.8–2.9 and 13.7–6.0 for the wrought and cast conditions, respectively. The activation energy of 46.8 kJ mol −1 which is very close to the activation energy for grain boundary diffusion of β-Sn, together with a very fine grain size of 4.5 μm and a uniform distribution of fine SnSb particles, may suggest that the dominant creep mechanism in the wrought condition is grain boundary diffusion. However, for the cast material with a coarse grain size of 280 μm, the n-values of 13.7 to 6.0 and the activation energy of 66.5 kJ mol −1 are indicative of a dislocation creep mechanism over the whole temperature range investigated.