Effect of thermomechanical fatigue on drop impact properties of Sn-Ag-Cu lead-free solder joints

Drop impact property after the solder joints were subjected to thermomechanical fatigue stresses were investigated. The solder compositions were SAC105 (Sn-1Ag-0.5Cu), SAC305 (Sn-3Ag-0.5Cu), and LF210N (Sn-2Ag-1Cu-0.05Ni) and the temperature range of the thermomechanical fatigue was from -45 degree of centigrade to +125 degree of centigrade. After 200 cycles of thermomechanical treatment, the drop property of SAC105 and SAC305 is almost the same low level whereas the drop property of LF210N keeps as-reflowed level. Microstructural observation revealed the difference of the fracture mode in these three solder compositions.