With the development of microelectronic packaging technology and the Pb-free process of electronic products, it is important to study the reliability of Pb-free solder bumps under thermal-electric coupling conditions to improve the operational reliability of Pb-free components. This paper proposes a simulation method of Pb-free solder bumps to simplify the analysis process and reduce costs, offering a guiding significance to the reliability assessment of electronic components. First, based on the theory of atomic migration and vacancy exchange mechanism, considering three driving forces of "electron wind", temperature gradient and stress gradient, a numerical algorithm of atomic migration void prediction is put forward. Next, using ANSYS parametric design language (APDL) and Matlab program as the carrier, a finite element analysis method of void evolution simulation is established. Then, selecting Sn3.0Ag0.5Cu Pb-free solder bumps in the chip-scale package (CSP) as the research object, the void nucleation and growth process of solder bumps under thermal-electric coupling conditions is simulated, and the void evolution simulation result of bumps is given. It can be proved that this simulation method can effectively predict the process of void formation and evolution.