功率循环载荷下BGA焊点应力与应变分析

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

建立了球栅阵列封装(ball grid array,BGA)焊点有限元分析模型,基于ANAND本构方程,分析了BGA焊点在功率循环载荷下应力与应变的分布情况,并搭建试验平台,完成了功率循环载荷下BGA封装器件应力与应变的测量试验,验证了仿真分析的可行性.选取焊点高度、焊点直径、焊盘直径和FR4基板厚度完成了正交试验分析,通过非线性回归分析得到高拟合度的BGA焊点功率循环应力量化评价模型.结果表明,BGA焊点结构参数对焊点应力影响大小排序为焊盘直径、FR4基板厚度、焊点直径和焊点高度,焊盘直径对BGA焊点应力影响显著,焊点直径、焊点高度和FR4基板厚度对BGA焊点应力影响不显著;最优参数水平组合为焊点高度0.39 mm、焊点直径0.42 mm、焊盘直径0.34 mm和FR4基板厚度0.8 mm,最优水平组合下BGA焊点应力与应变明显降低.创新点:(1)基于ANAND本构方程,模拟分析了BGA焊点在功率循环载荷下应力与应变分布.(2)分析了结构参数对焊点应力的影响显著性,并通过优化模型结构参数获得最佳结构参数组合.(3)通过非线性回归分析获得BGA焊点功率循环应力与结构参数之间的量化评价模型.

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 highlyfit 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 com-bination 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.Highlights:(1)Based on the ANAND constitutive equation,the stress and strain distribution of BGA solder joints were simulated and analyzed under power cyclic load.(2)The effect of structural parameters on stress of solder joint was analyzed,and the optimal combination was obtained through model parameter optimization.(3)A quantitative evaluation model between the power-cycling stress of BGA solder joint and structural parameters was obtained by nonlinear regression analysis.