Influence of dwell time and loading rate on low cycle fatigue behavior of lead-free solder joints

Low cycle fatigue tests on 96.5Sn-3Ag-0.5Cu solder joints were carried out using micro-uniaxial fatigue testing system at 25 ℃ with different dwell time (1-20 s) and different strain rates (0.01-0.08 mm/s). The results show that dwell time of 1-20 s has little influence on fatigue life of solder joints at 25 ℃. With the increasing of strain rates, the fatigue life of solder joints reduced gradually, and fracture mode was transformed from ductile fracture to brittle fracture. Fatigue cracks tended to initiate around the solder/IMC interfaces at the edge of the joints with different loading speeds, and then propagated within the solder proximately along the IMC interfaces. The fracture morphology of solder joints with different strain rates consisted mainly of propagation region and final fracture region.