This study designed and produced a special microsolder specimen (Sn3.8Ag0.7Cu) to equalize current density under stressing. The specimen was generated to avoid temperature gradient and thermal migration. The inelastic deformation of the solder with electromigration (EM) alone was then measured with moiré interferometry. In addition, the EM-induced solder stress was evaluated using a finite element method (FEM). The precision of the FEM model was verified by comparing the simulated results with the experimental results with respect to EM-induced deformation. Findings indicated that the maximum spherical stress in the solder can reach 50 MPa. Moreover, the vacancy concentration is much higher on the cathode end than on the anode end. The simulation results can illustrate the failure mode of a solder and can therefore provide a basis for the comprehensive evaluation of solder reliability under EM.