Creep behavior of micro-scale Cu/Sn–3.0Ag–0.5Cu/Cu joints under electro-thermo-mechanical coupled loads

Abstract

The creep behavior of line-type micro-scale Cu/Sn–3.0Ag–0.5Cu/Cu joints under electro-thermo-mechanical coupled loads with a high current density of 1.0 × 104 A/cm2 was characterized, in comparison with those without current stressing. Results show that under electro-thermo-mechanical coupled loads all joints exhibit typical three-stage creep characteristics similar with that of joints under the mechanical stress only, implying that the mechanical stress still dominates the creep deformation process of joints. The steady-state creep rate increases with the externally applied stress and temperature regardless of current stressing. Notably, the creep of joints under electro-thermo-mechanical coupled loads is accelerated in terms of an increase in the steady-state creep rate, compared with that without current stressing. The essential factors influencing the steady-state creep rate of joints are the damage effect and Joule heating induced by electro-thermo-mechanical coupled loads. Moreover, the results manifest that the creep activation energy and stress exponent of joints are independent of current stressing. The creep mechanisms of solder joints under electro-thermo-mechanical coupled loads and without current stressing are lattice diffusion.