基于回归分析和遗传算法的BGA焊点功率载荷热应力分析与优化

Thermal Stress Analysis and Optimization of BGA Solder Joint Power Load Based on Regression Analysis and Genetic Algorithm

建立了球栅阵列BGA(Ball Grid Array)焊点有限元分析模型,选取焊点高度、焊点最大径向尺寸、上焊盘直径和下焊盘直径作为设计变量,以焊点应力作为目标值,采用响应曲面法设计了29组不同水平组合的焊点模型并建模进行仿真计算,建立了焊点应力与结构参数的回归方程,基于回归方程结合遗传算法对焊点结构参数进行了优化,获得了焊点应力最小的结构参数最优水平组合.结果表明:对于无铅焊料SAC387,焊点应力随焊点的高度增加而减小,随最大径向尺寸的减小而减小;应力最小的焊点水平组合为:焊点高度0.38mm、最大径向尺寸0.42mm、上焊盘直径0.34mm和下焊盘直径0.35mm;对最优水平组合仿真验证表明优化后焊点最大应力下降了4.66MPa,实现了BGA焊点的结构优化.

The finite element analysis model of BGA(Ball Grid Array) solder joints is established.The height of solder joints,the maximum radial dimension of solder joints,the diameter of upper and lower solder joints are selected as design variables,and the stress of solder joints is taken as target value.29 groups of solder joints with different levels are designed and simulated by response surface methodology.The regression equation of solder joint stress and structural parameters is established.The structural parameters of solder joint are optimized based on the regression equation and genetic algorithm,and the optimal level combination of structural parameters with minimum solder joint stress is obtained.The results show that for lead-free solder SAC387,the solder joint stress decreases with the increase of solder joint height,and decreases with the decrease of maximum radial dimension;the combination of solder joint level with minimum stress is:solder joint height 0.38 mm,maximum radial dimension 0.42 mm,upper pad diameter 0.34 mm and lower pad diameter 0.35 mm.The results show that the maximum stress of the solder joint decreases by 4.66 MPa after optimization,and the structure optimization of BGA solder joint is realized.