倒装焊底充胶分层与SnPb焊点热疲劳的可靠性

采用实验和有限元模拟，研究了底充胶分层和ＳｎＰｂ焊点的可靠性。结果表明，底充胶分层易发生在芯片／底充胶界面边缘处；当底充胶与芯片粘合强度较弱时，底充胶的早期分层是焊点中裂纹萌生扩展从而导致失效的直接原因；当底充胶与芯片粘合强度较强时，分层可以削弱底充胶对焊点的机械耦合作用，从而影响焊点的热循环寿命，此时，焊点热疲劳裂纹是焊点失效的直接原因。

UNDERFILL DELAMINATION AND THERMAL FATIGUE RELIABILITY OF TIN-LEAD SOLDER JOINT OF FCOB

The thermal fatigue lifetime of tin-lead (SnPb) solder joints can be greatly increased by applying underfill encapsulant in flip chip on board (FCOB) assembly. However, the underfill delamination could correspondingly reduce the reliability of solder joints. By conducting thermal cycling test and finite element simulation, the underfill delamination and the SnPb solder joint reliability were investigated in this study. The results show that the underfill delamination initiates at the edge of chip/underfill interface. If the underfill did not have a good adherence to the chip, the fatigue crack initiation and propagation in the solder joints, which lead the solder joints to fail, should be caused directly by the incipient underfill delamination. If the underfill had a good adherence to the chip, the mechanical coupling effect of the underfill could be weakened by the underfill delamination, which should influenced lifetimes of the solder joints, moreover) the dominant failure mode should be the fatigue crack in the solder joints.