摘要
测量了有无芯下填料 B型和 D型两种倒扣芯片连接器件的焊点温度循环寿命 ,运用超声显微镜 (C- SAM)和扫描电镜 (SEM)观察了焊点微结构粗化和裂纹扩展 ,并采用三维有限元模拟方法分析了焊点在温度循环条件下的应力应变行为 .结合实验和模拟结果 ,建立了预估焊点疲劳寿命的 Coffin- Manson半经验方程 ,得到方程中的系数C=5 .5 4 ,β=- 1.38.模拟给出的焊点中剪切应变的轴向分布与实验得到的焊点在温度循环过程中的微结构粗化一致 .填充芯下填料后的倒扣芯片连接由于胶的机械耦合作用 ,降低了焊点的剪切变形 ,但热失配引起的器件整体弯曲增强 ,芯片的界面应力增大 .
The thermal fatigue failure of SnPb solder joints of flip chip on board with and without underfill is investigated for two types of flip chip packages by conducting thermal cycling tests,C SAM observations and cross section inspections.Meanwhile,the corresponding 3D finite element simulations are performed to analyze the effects of underfill on thermomechanical behavior of packaging assemblies.The half experiential Coffin Manson equation with material constant C =5 54, β =-1 38 is fitted from the combination of the lifetime measured and the shear plastic strain range simulated by 3D model.The axial strain distribution in solder joint from simulations is coincided very much with the distribution of microstructure coarsening from the cross section inspection.The mismatch of thermal expansion results in an integral warpage of assemblies in the case with underfill,which decreases the shear deformation of solder joint and increases the interface stress on the chip.The interface stress distribution from the 3D simulation agrees very well with the experimental observations.
基金
国家自然科学基金重点资助项目 (批准号 :1983 40 70 )
