Voids in BGA (Ball Grid Array) solder joints have been considered as a main defect in assembly. By taken the EBGA (Enhanced-BGA) solder joints as an example in this paper, the unified viscoplastic Anand constitutive equation has been employed to represent the viscoplastic deformation behavior and nonlinear finite element method has been applied to study the effect of size, location of voids on the fatigue life of solder joints, therefore the theoretical reference to establishing the inspection criteria of voids in BGA solder joints has been supplied.