Abstract: Based on the home-made multiphysics field coupling device, investigation was carried on the fracture behavior and the growth of intermetallic compounds (IMC) at the interface between Sn-3.0Ag-0.5Cu lead-free solder and Cu substrate. The results show that in the multiphysics field and 30-150 ℃ thermal fatigue cycles,the more the thermal fatigue cycles, the faster the IMC grows in the same aging temperature. The morphology of IMC changes from the scallop shape into the layered shape in a shorter cycle time. The growth of IMC is slowing down after 400 cycles. When the cycles are 600, the void gathered and grow up, resulting in interface cracks and fatigure failure. With the increasing thermal cycles, the shear strength of joint drops quickly and it also has a tendency to brittle fracture.