Low Cycle Fatigue Properties and Surface Feature by an Image Processing of Sn-0.7Cu Lead-free Solder

Abstract

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.