The low cycle fatigue (LCF) behavior of as-cast Sn-0.7mass%Cu lead-free solder and compared with those of conventional Sn-37mass%Pb solder were investigated at strain rate 0.1%/s under various temperatures, R.T. (room temperature), 80 o C, 120 o C. In addition, the relationship between the surface feature in the LCF test and the fatigue life of these solders at R.T. were investigated. The fatigue life of Sn-0.7Cu decreased with increasing temperature. And the fatigue life of Sn-0.7mass%Cu was better than that of the Sn-37mass%Pb solder at R.T. and 80 o C. The surface deformation as fine meshes during the LCF test of Sn-0.7mass%Cu did not appear until 10% of fatigue life. Although over 10% of fatigue life, surface deformation that was caused by micro cracks and these link up occurred with increasing number of cycles.

The low-cycle fatigue behavior and the relationship between the surface features in the low-cycle fatigue testing and the fatigue life of Sn-3.5Ag and Sn-0.7Cu lead-free solders were investigated at strain rate of 0.1%/s with a non-contact extensometer at room temperature ( 22 o C), 80 o C and 120 o C. In addition the fatigue life using the surface deformation of those solders were defined and estimated from the surface features of solders investigated by image processing and compared with Coffin-Manson type of fatigue behavior of solders. The fatigue life of Sn-3.5Ag solder was superior to that of Sn-0.7Cu solder under temperatures of 80 o C and 120 o C. The fatigue life defined from surface deformation indicated a close behavior to Coffin-Manson type of fatigue behavior in those solders. This method could identify the low-cycle fatigue life of solders from the surface deformation.