Abstract Cu6Sn5 is the most prominent intermetallic compound developing upon soldering Cu-containing base materials with typical Sn-based lead-free solders. The order-disorder transition occurring at 430–490 K and the possibly associated build-up of stresses is regarded as relevant for reliability of solder joints. In the present work, contradictory reports on the crystal structures and actual composition of the Cu6Sn5 intermetallic are explained by composition-dependent occurrence of the “classical” commensurately ordered η' phase and of an incommensurately ordered, more Cu-rich η phase. The previously reported η8-Cu5Sn4 and η4+1-Cu46Sn37 structures with different unit cells and symmetries are actually approximants of the η phase.

中文翻译：

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Cu6Sn5 金属间化合物：调和成分和晶体结构

摘要 Cu6Sn5 是在含铜基材与典型的锡基无铅焊料焊接时产生的最突出的金属间化合物。发生在 430-490 K 的有序-无序转变以及可能相关的应力积累被认为与焊点的可靠性有关。在目前的工作中，关于 Cu6Sn5 金属间化合物的晶体结构和实际组成的相互矛盾的报告是通过“经典”相称有序 η' 相和非相称有序、更富铜 η 相的组成依赖出现来解释的。先前报道的具有不同晶胞和对称性的 η8-Cu5Sn4 和 η4+1-Cu46Sn37 结构实际上是 η 相的近似值。