Volume 7, Issue 5 (May 2010)
Tensile Properties of Sn-10Sb-5Cu High Temperature Lead Free Solder
The Sn-10Sb-5Cu high temperature lead free solder was developed, and the mechanical property of such bulk solder and the solder joint was investigated in the present work. The microstructure of the Sn-10Sb-5Cu bulk solder was composed of long strip-like Cu6Sn5 and square Sn3Sb2 intermetallic compounds (IMCs). In the solder joint, the IMCs were the same as in the bulk solder but with a much finer microstructure. The test results showed that the tensile properties of the Sn-10Sb-5Cu bulk solder were sensitive to the strain rate. The higher the strain rate, the higher the ultimate strength. The ductility after fracture was enhanced by lowering strain rates. The fracture elongation approached 6.5 % when the strain rate was 10−5/s. Compared with that of the bulk Sn-10Sb-5Cu solder, the tensile strength of the Sn-10Sb-5Cu/Cu solder joint was much lower. The joint showed excellent plasticity with a large nominal engineering strain of 80 % during tensile tests. The tensile strength of the solder joint decreased after some aging time. However, the strength remained at about 80 % of the original value after aging for 15 days at the temperature of 150°C. The difference in the tensile properties between bulk solder and solder joint resulted from the difference in microstructures. Coarser Cu6Sn5 IMC in the bulk solder led to the higher ultimate strength, and the finer Cu6Sn5 IMC in the solder joint resulted in much better fracture ductility of the solder joint.