Stress analysis and parameter optimization of Fine-Pitch BGA solder joints under cantilever plate torsion conditions

Abstract

In this paper, a 3D finite element model of the solder joints of a 165-PIN PLASTIC FBGA (13x15) package was developed using ANSYS software according to the packaging of a static storage device. Then, the model was loaded with cantilever plate torsion model conditions and finite element simulation analysis was performed. In order to analyze the effects of different combinations of parameters with different levels of solder joint material, solder joint height, pad diameter and PCB board thickness on the maximum stress in FBGA solder joints, we designed 16 sets of orthogonal test scenarios using SPSS software and simulated the established finite element models in turn. After multi-factor ANOVA on the experimental data using SPSS software, the results showed that the maximum stresses in the FBGA joints were not uniformly distributed under the torsional loading conditions of the cantilever plate, with the maximum stresses in the joints occurring at the outermost edge of the joints near the side of the applied load that contacts the PCB surface. At 95% confidence level, the PCB board thickness has the most significant effect on the maximum stress in the solder joint among the four factors: solder joint material, solder joint height, pad diameter and PCB board thickness. After optimizing the combination of the given factor levels, the best combination that minimizes the maximum stress in the solder joint is obtained, and the results of the simulation show that the maximum stress in the FBGA solder joint is significantly reduced.