2005 Volume 46 Issue 11 Pages 2335-2343
The low-cycle fatigue behavior of Sn–3.5 mass%Ag, Sn–0.7 mass%Cu lead-free solders and Sn–37 mass%Pb solder were investigated at a strain rate of 0.1%/s with a non-contact extensometer at room temperature (22±3°C). In addition, the relationship between the surface features in the low-cycle fatigue test and the fatigue life of those solders were investigated by image processing. The fatigue lives of Sn–3.5 mass%Ag and Sn–0.7 mass%Cu were better than that of Sn–37 mass%Pb. The low-cycle fatigue behavior on each solder followed Coffin–Manson equation. The surface deformation in fine wrinkles was observed in the low-cycle fatigue test at each solder. The surface features for each solder were evaluated by image processing from the surface deformation. The surface features in the low-cycle fatigue test did not appear until under 10% of the fatigue life for Sn–3.5 mass%Ag, until 10% of the fatigue life for Sn–0.7 mass%Cu, and until 20% of the fatigue life for Sn–37 mass%Pb.