Creep Behavior of Annealed Lead-free Solder for High-power Electronic Device
The present paper investigated the annealing effect on creep behaviour of lead-free Sn-3.0Ag-0.5Cu (w.t., SAC305) solder material. According to the previous finding by nanoindentation and uniaxial tensile experiments, the optimal annealing condition of SAC305 solder was believed as 210°C for 12h to minimize the residual stress and stabilize the mechanical property of annealed solder. In order to simulate the high-temperature environment of high-power devices, the annealing temperature at 210°C is adopted with varying duration from 12 hours to 48 hours as the creep deformation usually results from long-term working conditions. The creep deformations in the time history for different cases are compared and discussed. Steady-state creep rate is also calculated to quantitatively reflect the annealing effect on creep resistance. In general, a longer duration of annealing at 210°C will increase the specimen’s time to failure and decrease the steady-state creep rate. Besides, failure modes of annealed specimens are examined by scanning electron microscopy images. It is found that with increasing the annealing duration, the specimen intends to fracture in a more ductile way with a greater ultimate tensile strain.