Numerical studies of the mechanical response of solder joint to drop/impact load

The geometry of the solder ball is one of several factors which have significant effects on the reliability of interconnects of electronic packages. Intensive studies of the thermo-mechanical reliability of BGA packages with different solder balls have been reported in recent years. Only a few studies of the geometric shape effect on the reliability of solder joints under drop loading conditions could be found in the literature. Because of the different failure modes and failure mechanisms, the geometric shape effects on the reliability of solder joints could be very different under thermo-mechanical loading condition and drop loading condition. In this paper, the effects of the solder ball geometry on the reliability under drop loading conditions are systematically studied with numerical simulations. The solder ball shape is predicted by using the Surface Evolver software. The solder ball geometry is parameterized with solder volume, diameter, height, and pad size. The variation of stresses on the solder joint/pad interface with solder volume and pad diameter is obtained from numerical simulations. The effect of the solder ball geometric parameters on the drop damage is discussed.