在热-机械疲劳(Thermomechanical Fatigue, TMF)条件下，无铅互连焊点会发生再结晶和微观组织演变，焊点局部再结晶区的晶体取向发生显著改变，裂纹在焊点的再结晶区萌生扩展直至最终失效。然而，目前关于无铅互连焊点的再结晶机制及再结晶行为对其失效模式的影响机制未有定论。而且，尚无针对焊点TMF晶体取向演变进行的电子背散射衍射(Electron Backscattered Diffraction, EBSD)原位观察实验的相关报道，这主要是由于在TMF后，无铅互连焊点横截面存在污染物，使得EBSD花样的标定变得很困难。申请者发现采用石英管封装焊点横截面的方法可以有效地解决这一问题。本项目基于EBSD原位观察及分析，开展无铅互连焊点再结晶形成机制及再结晶行为对其失效模式影响机制的研究，将极大程度地提高对无铅互连焊点可靠性的认识水平。

Recrystallization behavior and microstructural changes are observed in Pb-free solder joints during thermomechanical fatigue (TMF). The orientations of solder joints can be changed significantly by recrystallization. The initiation and propagation of cracks are frequently accompanied with recrystallization until the final failure of Pb-free solder joints. However, the underlying formation mechanism of recrystallization and its role in the failure of Pb-free solder joints are still not well understood. Also, in-situ electron backscattered diffraction (EBSD) observation, an effective way to clarify the mechanism of recrystallization, has not been reported mainly due to its inability of pattern indexing from the cross-section contamination after TMF. The applicants found that a method of encapsulating cross-sectioned joint in glass tube could be applied to solve the problem. In this study, based on the in-situ EBSD observations and analysis, the underlying formation mechanism of recrystallization and its role in the failure of Pb-free solder joints are discussed, contributing to a better understanding of the reliability of Pb-free solder joints.