In this study, a large number of creep tests were carried out to study the effect of stress level and testing temperature on the creep behavior of 63 Sn/37Pb solder in a systematic manner. Based on the dislocation controlled creep mechanism and Gibbs’ free-energy theory, a new creep constitutive model was proposed. The model was found to describe accurately the creep flow of the solder and to be capable of explaining the issues of stress and temperature dependent stress exponent and activation energy in the Arrhenius power-law creep model. Furthermore, the model was employed to predict accurately the long-term reliability of solder joints in a PBGA assembly.

In this study, a large number of creep tests were carried out using miniature specimens in order to investigate the creep behavior of 63Sn/37Pb eutectic solder alloy over a wide temperature range from −40 to 150°C and stress range from 0.75 to 70 MPa. Based on dislocation and diffusion theories, two unified constitutive models were developed to describe the dislocation-controlled and diffusion-controlled creep behaviors observed. It was found that the two models accurately predict the experimental data. A deformation mechanism map was established for this eutectic solder alloy in order to interpret the creep mechanism under different temperature and loading conditions.

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