AN EVALUATION OF FATIGUE DAMAGE IN LOW-CYCLE RANGE FOR SN-3.5AG, SN-0.7CU LEAD-FREE SOLDERS AND SN-PB EUTECTIC SOLDER USING IMAGE PROCESSING TO SURFACE FEATURE

摘要

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