Analysis of stress and strain in BGA solder joints under power cyclic load

The finite element analysis model of ball grid array (BGA) solder joints is established. Based on the ANAND constitutive equation, the distribution of stress and strain of BGA solder joints under power cyclic load is analyzed. A experimental platform was built to measure the stress and strain of BGA packaged devices under power cyclic load, and the feasibility of simulation analysis was verified. Orthogonal experimental design was completed by setting height and diameter of solder joint, pad diameter, and thickness of FR4 substrate as parameters. Through nonlinear regression analysis, a highly-fit quantitative evaluation model was obtained for power-cycling stress in BGA solder joints. The results show that the influence of BGA solder joint structural parameters on solder joint stress is sorted as pad diameter, FR4 substrate thickness, solder joint diameter and solder joint height. The pad diameter has a significant effect on BGA solder joint stress, and solder joint diameter, height and FR4 substrate thickness have no significant effect on BGA solder joint stress. The optimal combination of structural parameter level is 0.39 mm for the solder joint height, 0.42 mm for the solder joint diameter, 0.34 mm for the pad diameter and 0.8 mm for the FR4 substrate thickness. With the optimal combination, the stress and strain of BGA solder joints are significantly reduced.