底充胶叠层PBGA无铅焊点随机振动应力应变分析

Stress and strain distribution of PBGA stacked lead-free solder joints with underfill with random vibration

建立了底充胶叠层塑料球栅阵列(plastic ball grid array,PBGA)无铅焊点三维有限元分析模型,研究了PBGA结构方式、焊点材料、底充胶弹性模量和密度对叠层无铅焊点随机振动应力应变的影响.结果表明,底充胶可有效降低焊点内的随机振动应力应变;在其它条件相同下,对于Sn95.5Ag3.8Cu0.7,Sn96.5Ag3Cu0.5,Sn-3.5Ag和Sn63Pb37这四种焊料,采用Sn-3.5Ag的底充胶叠层焊点内的随机振动最大应力应变最小,采用Sn96.5Ag3Cu 0.5的焊点内的最大应力应变最大;随着底充胶弹性模量的增大,叠层无铅内的随机振动应力应变值相应减小;随着底充胶密度的增大,叠层无铅内的随机振动应力应变值相应增大.

The 3D finite element analysis model of plastic ball grid array( PBGA) stacked lead-free solder joints with underfills was developed. By using ANSYS the finite element analysis was performed based on the model with random vibration.The influences of PBGA assembly structure,solder joint material,underfill elastic modulus and underfill density on PBGA stacked lead-free solder joint stress and strain under random vibration load were respectively studied. The results show that comparing to the no-underfill stacked solder joints the stress and strain in the stacked solder joint can be effectively reduced under random vibration load. When other conditions being equal,forSn95. 5Ag3. 8Cu0. 7, Sn96. 5Ag3Cu0. 5, Sn-3. 5Ag and Sn63Pb37,the lead free Sn-3. 5Ag stack solder joint has the minimum stress and strain while the lead-free SAC305 stack solder joint has the maximum stress and strain in the solder ball.The stress and strain in the lead-free stacked solder was reduced with the increase of underfill elasticity modulus. With the increase of the underfill density, the stress and strain in the stacked lead-free solder joint increased correspondingly.