Abstract A non-uniform copper oxide layer with several hundred nanometers thick was observed covering the surface of 10 μm-diameter Cu/SnAg microbump. Tin whiskers were also found to form on the weak spots of this copper oxide layer, where were localized stress relief centers. The HRTEM results reveal the existence of twin grain boundary between tin whisker and neighboring grain. Numerous dislocations at the twin boundary provide paths for the tin atoms to slip into tin whisker. It is the first time that the existence of copper oxide layer and the relationship between copper oxide layer and tin whiskers growth was studied and revealed in micron-level bumps. This present study has significant meaning for 3D electronic packaging as small size microbumps become increasingly prevalent and in which, surface diffusion becomes more important.

中文翻译：

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不均匀氧化铜层对小直径SnAg微凸块中锡晶须生长及锡晶须生长行为的影响

摘要 在直径为 10 μm 的 Cu/SnAg 微凸块表面上观察到一层不均匀的数百纳米厚的氧化铜层。还发现在该氧化铜层的薄弱点上形成了锡晶须，这些地方是局部应力消除中心。HRTEM 结果表明锡晶须和相邻晶粒之间存在孪晶晶界。双晶边界处的许多位错为锡原子滑入锡须提供了路径。首次在微米级凸块中研究和揭示氧化铜层的存在以及氧化铜层与锡晶须生长的关系。本研究对 3D 电子封装具有重要意义，因为小尺寸微凸点变得越来越普遍，其中表面扩散变得更加重要。