Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, Liaoning 110016, China.
Microsc Microanal. 2013 Aug;19 Suppl 5:105-8. doi: 10.1017/S1431927613012439.
Kirkendall void formation at the solder/metallization interface is an important reliability concern for Cu conductors and under-bump metallization in microelectronic packaging industry, whose mechanism is still hard to be understood for different individual cases. In the present work, two typical solder/Cu-diffusing couples, eutectic SnIn/Cu and SnBi/Cu, were studied by scanning/transmission electron microscopy to investigate the microstructural evolution and voiding process after soldering and then solid-state aging. It was concluded that Kirkendall voids formed between two sublayers within Cu2(In,Sn) phase in eutectic SnIn/Cu solder joint, whereas they appeared at the Cu3Sn/Cu interface or within Cu3Sn for eutectic SnBi/Cu solder joint. Besides the effect of impurity elements, the morphological difference within one intermetallic compound layer could change the diffusing rates of reactive species, hence resulting in void formation in the reaction zone.
在微电子封装工业中，焊点/金属化界面的 Kirkendall 空洞形成是铜导体和凸点下金属化的一个重要可靠性问题，其机制对于不同的具体情况仍然难以理解。在本工作中，通过扫描/透射电子显微镜研究了两种典型的焊锡/Cu 扩散偶，共晶 SnIn/Cu 和 SnBi/Cu，以研究焊接和随后的固态时效后微观结构的演变和空洞形成过程。结果表明，在共晶 SnIn/Cu 焊点中，Kirkendall 空洞形成于 Cu2(In,Sn) 相的两个亚层之间，而在共晶 SnBi/Cu 焊点中，它们出现在 Cu3Sn/Cu 界面或 Cu3Sn 内部。除了杂质元素的影响外，同一金属间化合物层内的形态差异会改变反应性物质的扩散速率，从而导致反应区形成空洞。
