QFP solder joint bending stress analysis and parameter optimization under constant temperature field conditions

Abstract

In this paper, a three-dimensional finite model of a 100-PIN QFP package solder joint package is established using ANSYS software. The QFP model is loaded with bending stress conditions at a constant temperature field of 125°C for 600 seconds, and finite element simulation analysis is performed to explore the solder joint reliability according to the static storage package. In order to analyze the effects of different levels of PCB thickness, chip thickness, solder joint height and solder joint spacing on the solder joint stress, nine sets of orthogonal experiments with 4 factors and 3 levels are designed in this paper, and the corresponding nine sets of finite element models are built based on the orthogonal experimental groups for stress analysis. Then the experimental data were visualized by extreme difference analysis and one-way ANOVA was performed by SPSS software to obtain the optimal combination and verify the correctness of the combination. The results show that under the condition of bending stress loaded on QPF solder joints at a constant temperature of 125°C for 600 seconds, the stress distribution in the solder joints is not uniform and the maximum stress appears on the outermost side of the solder joints, near the side where the applied load touches the surface of the PCB. The optimal combination of parameters is 0.8mm PCB thickness, 1.2mm chip thickness, 0.08mm solder joint height and 0.5mm solder joint spacing, under which the maximum bending stress of QPF solder joint is significantly reduced.