Fu Xing, Liu Min, Xu KeXin, Chen Si, Shi YiJun, Fu ZhiWei, Huang Yun, Chen HongTao, Yao RuoHe
School of Electronics and Information, South China University of Technology, Guangzhou 510640, China.
Department of Reliability Design Research, China Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, Guangzhou 510610, China.
Materials (Basel). 2020 Dec 2;13(23):5497. doi: 10.3390/ma13235497.
The in-situ observation of Sn-3.0Ag-0.5Cu solder joints under electromigration was conducted to investigate the microstructure and grain orientation evolution. It was observed that there was a grain rotation phenomenon during current stressing by in-situ electron backscattered diffraction (EBSD). The rotation angle was calculated, which indicated that the grain reorientation led to the decrease of the resistance of solder joints. On the other hand, the orientation of β-Sn played a critical role in determining the migration of Cu atoms in solder joints under current stressing migration. When the angle between the electron flow direction and the c-axis of Sn (defined as ) was close to 0°, massive CuSn intermetallic compounds were observed in the solder bulk; however, when was close to 90°, the migration of the intermetallic compound (IMC) was blocked but many Sn hillocks grew in the anode. Moreover, the low angle boundaries were the fast diffusion channel of Cu atoms while the high grain boundaries in the range of 55°-65° were not favorable to the fast diffusion of Cu atoms.
对Sn-3.0Ag-0.5Cu焊点进行电迁移原位观察，以研究其微观结构和晶粒取向演变。通过原位电子背散射衍射（EBSD）观察到，在电流应力作用下存在晶粒旋转现象。计算了旋转角度，结果表明晶粒重新取向导致焊点电阻降低。另一方面，β-Sn的取向在确定电流应力迁移下焊点中Cu原子的迁移方面起着关键作用。当电子流动方向与Sn的c轴之间的夹角（定义为）接近0°时，在焊料块体中观察到大量CuSn金属间化合物；然而，当接近90°时，金属间化合物（IMC）的迁移受阻，但阳极处生长了许多Sn小丘。此外，低角度边界是Cu原子的快速扩散通道，而55°-65°范围内的高角度边界不利于Cu原子的快速扩散。
