【摘要】 对比了充胶和未充胶塑料封装球栅阵列 (PBGA)器件在 - 40℃～ 12 5℃温度循环条件下的热疲劳寿命 ,采用光学显微镜研究了失效样品焊点的失效机制 ,并分析了充胶提高器件热疲劳寿命的机制。实验发现 :底充胶可使PBGA样品的寿命从 5 0 0周提高到 2 0 0 0周以上 ,失效样品裂纹最先萌生于最外侧焊球中近硅芯片界面外边缘处 ,界面处焊料组织粗化及界面脆性金属间化合物Ni3Sn2 和NiSn3 相的生成均促使裂纹沿该界面从焊球边缘向中心扩展。PBGA焊点界面处裂纹的萌生和扩展是该处应力应变集中、焊料组织粗化以及生成脆性金属间化合物等各种金属学和力学因素共同作用的结果。更多还原

【Abstract】 Failure mechanism, as well as failure cycles of two groups of plastic ball grid array(PBGA) samples (with/without underfill) under thermal cycling conditions in the range of -40?℃～125?℃, were presented. The experiment results show that underfill can improve the thermal cycle life of PBGAs drastically, from 500 cycles to over 2?000 cycles. Highly concentrated stress and strain induced by the mismatch of thermal expension coefficient between the BGA component and the printed circuit board, coarsened grain and two kinds of intermetallic compounds (Ni 3Sn 2/NiSn 3) which formed during reflow and thermal cycle and their negative effects on the reliability of solder joints were discussed. It is found that the initiation and propagation of micro crack are caused by all the three factors above. The initiation of the crack and direction of its propagation were also presented.更多还原