Creep behaviour of Sn–3.8Ag–0.7Cu under the effect of electromigration: Experiments and modelling

In this paper, creep behaviour of Sn–3.8Ag–0.7Cu (SAC) lead-free solder under the collective effect of electromigration, stress and temperature was investigated. Firstly, the conventional creep test was improved so that high current density can be applied to the ribbon sample and serve as one of the experimental control variables. Experimental results indicate that creep rate of the SAC was greatly affected by electromigration (EM) and its linear dependence on current density and stress was revealed. Then a unified phenomenological creep model with variables of stress, temperature and current density was set up based on the fact that both the mechanisms of conventional creep and electromigration are vacancy diffusion type. Coefficients in the unified creep model were determined from the experimental results by curve fitting, and numerical results of the unified creep model are found to fit the experimental results quite well.