Creep Behavior of Sn-3.5Ag and Sn-5Sb Lead-free Solder Alloys at Elevated Temperatures

Abstract

In order to acquire the relevant creep characteristics such as stress exponent and activation energy, creep strain tests were conducted on Sn-3.5Ag and Sn-5Sb systems of solder alloys in the intermediate temperature regime from 353K to 453K corresponding to the homologous temperatures η=0.715∼0.917 and η=0.699∼0.897 for two alloys, respectively.
It was found that an apparent creep-activation energy of both Sn-3.5Ag and Sn-5Sb solder alloys had a changing point at theη=0.82 under the higher stress of 9.8MPa. At the lower stress of 4MPa, the change point was found only for Sn-5Sb alloy.
Moreover, under the lower stress level (less than 6MPa), the stress exponent of the both solder alloys indicated n Nearly Equal 1, while under the higher stress region (more than 9.8MPa), the stress exponent of the both solders showed n>7.
Determining factors of creep deformation were discussed in relation with the temperature and stress regimes. It was considered that the deformation of the both solder alloys is dominated by the rate of the dislocation climb/dislocation glide at the higher temperature and stress regime.