Abstract: Finite element method is used to analysis the soldered joint reliability of FCBGA, the unified viscoplastic Anand constitutive equation is employed to represent the viscoplastic deformation behavior of Sn63Pb37 alloy.The results shows that the stress concentrated on the top surface of the chip-edge FCBGA corner soldered joint and present cyclical changes with time, stress relaxation and accumulated enhancement trend of stress can be obvious acquired from the curve.Select three different ball size device for the study, it indicates that the ball size of 0.4 mm×0.28mm has the maximal soldered joint stress, 0.46 mm×0.34mm ball second, and 0.52 mm×0.4mm ball minimum.Based on the analysis of plastic work accumulation can acquire the same trend.The trends is obtained by the consistent results with practical application of the device.At the same time provide a basis for the theoretical research of flip-chip devices.