Abstract Electromigration (EM) causes intermetallic and void growth that decreases the reliability and lifetime of solder joints. As a diffusion-controlled process, EM is highly dependent on the fastest diffusion pathways in a structure. In anisotropic β-tetragonal Sn those pathways are along high angle grain boundaries and along the c-axis of the Sn grains. A bicrystal sample with two major grain orientations and two major grain boundary types was EM tested for 100 h. EM was interrupted at intervals for x-ray microtomography to reveal the 3D evolution of intermetallic compounds (IMCs) and voids within the joint. Quantitative IMC growth along high angle grain boundaries and twins was captured for the first time and related to the effective Cu diffusivity of multiple grains. Using a correlative approach that combined scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) mapping, IMC growth and morphology were linked to the evolution of the Sn grain structure. Unusual void shrinkage and void splitting behavior were connected to uneven cathode interface consumption and thermal compression.

中文翻译：

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双晶纯锡焊点中 Cu6Sn5 金属间化合物和空洞的四维 (4D) 微观结构演变

摘要 电迁移 (EM) 会导致金属间化合物和空隙增长，从而降低焊点的可靠性和使用寿命。作为扩散控制过程，EM 高度依赖于结构中最快的扩散路径。在各向异性 β-四方 Sn 中，这些路径沿着大角度晶界和 Sn 晶粒的 c 轴。对具有两种主要晶粒取向和两种主要晶界类型的双晶样品进行 100 小时的 EM 测试。X 射线显微断层扫描每隔一段时间中断 EM，以揭示金属间化合物 (IMC) 和接头内空隙的 3D 演变。沿大角度晶界和孪晶的定量 IMC 生长首次被捕获，并且与多个晶粒的有效 Cu 扩散率有关。使用结合扫描电子显微镜 (SEM) 和电子背散射衍射 (EBSD) 映射的相关方法，IMC 生长和形态与 Sn 晶粒结构的演变有关。异常的空隙收缩和空隙分裂行为与不均匀的阴极界面消耗和热压缩有关。