Yue Wu, Ding Chao, Qin Hongbo, Gong Chenggong, Zhang Junxi
School of Materials Engineering, Lanzhou Institute of Technology, Lanzhou 730050, China.
School of Mechanical and Electronic Engineering, Guilin University of Electronic Technology, Guilin 541004, China.
Materials (Basel). 2021 May 11;14(10):2486. doi: 10.3390/ma14102486.
The crystallographic characteristic effect of Cu substrate on cathode dissolution behavior in line-type Cu/Sn-3.0Ag-0.5Cu (SAC305)/Cu solder joints during electromigration (EM) was investigated by scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and first-principles calculations. The SEM and EBSD results show that the crystallographic characteristic of Cu substrate is crucial to cathode dissolution behavior under a direct current of 1.5 × 10 A/cm at 125 °C ± 2 °C. When the (001) plane of copper grain adjacent to the CuSn/Cu interface is perpendicular or nearly perpendicular to the current direction, local cathode dissolution tips are easily formed, whereas the (111) plane remains mostly undissolved, which finally leads to the inhomogeneous cathode serrated dissolution in the substrate. The first-principles calculation results reveal that the different surface energies and energy barriers of the different crystallographic planes of Cu grains in the substrate are responsible for the local cathode dissolution tips. Adjusting the copper grain in a substrate to a crystal plane or direction that is difficult to dissolve during EM is a promising method for improving the reliability of solder joints in the future.
通过扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和第一性原理计算，研究了铜基板对线型铜/锡-3.0银-0.5铜（SAC305）/铜焊点在电迁移（EM）过程中阴极溶解行为的晶体学特征效应。SEM和EBSD结果表明，在125℃±2℃、1.5×10 A/cm的直流电流下，铜基板的晶体学特征对阴极溶解行为至关重要。当与CuSn/Cu界面相邻的铜晶粒的（001）面垂直或近乎垂直于电流方向时，容易形成局部阴极溶解尖端，而（111）面大多保持未溶解状态，最终导致基板中阴极出现不均匀的锯齿状溶解。第一性原理计算结果表明，基板中铜晶粒不同晶面的表面能和能垒差异是导致局部阴极溶解尖端的原因。在未来，将基板中的铜晶粒调整到在电迁移过程中难以溶解的晶面或方向，是提高焊点可靠性的一种有前景的方法。
