Effect of interface structure on fatigue life under thermal cycle with SAC305 solder joints

During the service time, the interface profile of interconnection and morphology of intermetallic compounds (IMC) changes owning to the atomic diffusion in solder bump joint, and they also have significant influence on the thermal fatigue behavior, especially the formation of fatigue cracks in the joint. In this paper, the equivalent plastic strain is calculated by finite element method (FEM) with ANSYS software to investigate the influence of IMC layer in SAC305 solder joint. And then, the Coffin-Manson lifetime prediction equation is used to predict the fatigue life with different IMC roughness and thickness. As a result, with the increase of the thickness of IMC, the fatigue life of solder joints reduce significantly. Furthermore, rougher surface of IMC layer results in a higher solder joint fatigue life. The equivalent plastic strain of the solder joints decreases with the increasing of the roughness of IMC interface. When the roughness decreases from 2.0 μm to 1.5 μm, the thermal fatigue life of the solder joints can be reduced by 72%.