Abstract: By employing the potential energy controlling equation for SnPb solder joint formation in surface mount technology,the 3D solder joint geometry were numerically simulated.Based on the calculated potential energy data for the solder joint system,the stand-off height and the self-alignment effects for misaligned placement were investigated.The results show that the stand-off height increases near linearly with the increase of solder volume.The increases of stand-off height and solder volume can enhance the self-alignment of chip component.Moreover,a regression model for stand-off height was put forward.