Abstract βSn nucleation is a key step in the formation of microstructure in electronic solder joints. Here, the heterogeneous nucleation of βSn is studied in undercooled tin droplets spread on the facets of various intermetallic compounds (IMCs). Nucleation undercoolings are measured in solidifying droplets and are linked to orientation relationships (ORs) measured by electron backscatter diffraction (EBSD). Preferred ORs developed on all IMCs studied. For the more potent nucleants (αCoSn3, IrSn4, PtSn4, PdSn4) the ORs represent relatively simple atomic matches. ORs with lower potency nucleants (Cu6Sn5, Ag3Sn, Ni3Sn4) had more complex atomic matches that are explored based on matching of the closest packed atomic rows. βSn solidification twinning is shown to be more complex than has been reported previously: both nucleation on an IMC facet and cyclic twinning of that grain occurred in many droplets on Cu6Sn5, Ag3Sn, Ni3Sn4; in all twinned droplets the Sn twinning axis occurred along a direction on the IMC with the lowest linear atomic disregistry; and interrelated cyclic twins formed consisting of up to five rings of cyclic twins all related by shared Sn axes.

中文翻译：

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单晶金属间化合物锡滴凝固过程中的成核和孪晶

摘要 βSn成核是电子焊点微观结构形成的关键步骤。在这里，在散布在各种金属间化合物 (IMC) 面上的过冷锡滴中研究了 βSn 的异相成核。成核过冷度是在凝固的液滴中测量的，并且与通过电子背散射衍射 (EBSD) 测量的取向关系 (OR) 相关联。在研究的所有 IMC 上开发的首选 OR。对于更有效的成核剂（αCoSn3、IrSn4、PtSn4、PdSn4），OR 代表相对简单的原子匹配。具有较低效力成核剂（Cu6Sn5、Ag3Sn、Ni3Sn4）的 OR 具有更复杂的原子匹配，这些原子匹配基于最紧密排列的原子行的匹配进行探索。βSn 凝固孪晶显示出比之前报道的更复杂：IMC 面上的成核和晶粒的循环孪晶都发生在 Cu6Sn5、Ag3Sn、Ni3Sn4 上的许多液滴中；在所有孪晶液滴中，Sn 孪晶轴沿 IMC 上具有最低线性原子失配的方向发生；和相互关联的环状孪晶形成，由多达五个环状孪晶环组成，所有环都通过共享的 Sn 轴相关联。