Abstract: Taguchi method is applied to evaluate the solder joint reliability of PBGA (plastic ball grid array)under thermal cycling test by using nonlinear finite element method.The size and thickness of PCB (printed circuit board), the size and thickness of substrate, the diameter and height of solder joint, the thickness of die and the thickness of EMC are eight control factors that are selected to configure in L18 orthogonal array.The best control factor combination of PBGA can be decided as a combination with A₁,B₃,C₁,D₂,E₂,F₃,G₃,H₃ based on the optimization of Taguchi method, which solder joint diameter A, PCB size B, die thickness F and solder joint height G are four most important factors among them.The results show that the experimental data and predictive value of optimization are 2.87964 and 0.88286 larger than those of original state separately.