基于扭转载荷的微尺度CSP焊点应力应变分析与优化

Stress and Strain Analysis and Optimization of Micro-scale CSP Solder Joints Based on Torsion Load

建立了微尺度芯片尺寸封装焊点有限元分析模型并对其进行扭转应力应变仿真分析与实验验证.分析了焊点材料、焊点直径、焊盘直径和焊点高度对焊点扭转应力应变的影响;以焊点材料、焊点直径、焊盘直径和焊点高度为设计变量,采用响应面法设计了29组不同水平组合的焊点模型并获取了相应焊点扭转应力,建立了焊点扭转应力与焊点结构参数的回归方程,结合遗传算法对焊点结构参数进行了优化.结果表明:焊点材料为SAC305时扭转应力应变最大,焊点最大扭转应力应变随焊点直径和焊盘直径增加而减小、随焊点高度增大而增大;最优焊点结构参数水平组合为:焊点材料SAC305、焊点直径0.22mm、焊盘直径0.14mm和焊点高度0.14mm;仿真验证表明最优焊点最大扭转应力下降了3.7MPa.

The finite element analysis model of micro-scale chip scale package(CSP)solder joints is set up and stress and strain analysis are performed under torsion load,and the verification experiment is also carried out.The influence of solder joint diameter,solder joint diameter,pad diameter and solder joint height on the torsion stress and strain of micro-scale CSP solder joints are analyzed.The solder joint material,solder joint diameter,pad diameter and solder joint height are selected as design variables;29 groups of solder joints with different levels are designed and simulated by response surface methodology.The regression equation of solder joint torsion stress and structural parameters is established.The structural parameters of solder joint are optimized based on the regression equation and genetic algorithm.The results show that the maximum torsion stress and strain occurs with the solder joints material of SAC305,the maximum solder joint torsion stress and strain decreases with the increase of solder joint diameter and pad diameter,and increases with the increase of solder joint height;the optimal combination of solder joint level is the solder joint material of SAC305,the solder joint diameter of 0.22mm,the pad diameter of 0.14 mm and the solder joint height of 0.14mm,and simulation verification result shows the maximum stress of the solder joint decreases by 3.7MPa after optimization.