Fatigue Damage Evaluation by Surface Feature for Sn-3.5Ag and Sn-0.7Cu Solders

摘要

The low-cycle fatigue behavior of Sn-3.5 mass percetn Ag, Sn-0.7 mass percent Cu lead-free solders and Sn-37 mass percent Pb solder were investigated at a strain rate of 0.1 percent/s with a non-contact extensometer at room temperature (22 +- 3 deg 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 percent Ag and Sn-0.7 mass percent Cu were better than that of Sn-37 mass percent 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 percent of the fatigue life for Sn-3.5 mass percent Ag, until 10 percent of the fatigue life for Sn-0.7 mass percent Cu, and until 20 percent of the fatigue life for Sn-37 mass percent Pb.