Abstract: Warpage and stress arising from the assembly process of a TSV interposer have important impacts on the reliability of microbumps. In this paper, two assembly processes, the top-down process and the bottom-up process, are simulated by the finite element method. By comparing the warpage and stress induced in the two assembly processes, an optimized process is obtained. The mechanical behavior of microbumps during each step of the optimized process is investigated by focusing on the effect of microbump location on the microbump reliability. The results show that the TSV-copper deformation has significant impact on the plastic work density of the microbump, the microbumps should be designed to keep away from the underfill fillet. In the case of the microbump located right up on the TSV, the plastic work density of the microbump array is the lowest and has an almost uniform distribution.