Reliability optimization design of Ball Grid Array (BGA) solder joints is a major concern in area array electronics packaging technology. In this paper, shapes of the solder joints and their reliability were predicted and analyzed. Through the variations of lower pads’ diameters, the shapes of full array BGA solder joints with different solder volumes were predicted by using surface evolver software. Based on the results of shape prediction, 3-D finite element models were established with MSC.MARC and the distribution of the stress and strain in the BGA solder joints under thermal cyclic loading were simulated. Finally, fatigue lives of the BGA solder joints with different solder volumes were calculated, and the diameter ratios of lower pad to upper pad for these two kinds of BGA assemblies with the best reliability were optimized.