Electric current-assisted creep behaviour of Sn–3.0Ag–0.5Cu solder
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The creep behaviour of Sn–3.0Ag–0.5Cu lead-free solder specimens with a diameter of 1.0 mm is investigated subjected to tensile forces from 10 to 25 N under electric currents ranging from 0 to 20 A. Due to the Joule heating effect, the solder temperature induced by electric current is measured to quantify the deterioration of tensile behaviour. Based on the observed steady-state creep deformation, the creep strain rate varies linearly with the tensile stress in the natural logarithmic coordinate with a stress threshold for the electric current between 0 and 10 A, and the natural logarithm of creep rate has a linear relationship with the square of current density. By revealing the dislocation climbing as the dominate creep mechanism under the coupled mechanical–electric–thermal loading, a modified Norton’s model is proposed which shows exponential dependence on the square of current density and the natural logarithm of tensile stress with the stress exponent enriched as a quadratic function of current density.
This work was supported by the National Natural Science Foundation of China (Nos. 51508464 and 11572249), the Natural Science Foundation of Shaanxi Province (No. 2017JM1013), the Fundamental Research Funds for the Central Universities (No. 3102016ZY017) and the Astronautics Supporting Technology Foundation of China (No. 2017-HT-XG).
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