Nucleation and growth of Ag3Sn in Sn-Ag and Sn-Ag-Cu solder alloys
Nucleation and growth of Ag3Sn in Sn-Ag and Sn-Ag-Cu solder alloys
复制标题
DOI：
10.1016/j.actamat.2023.118831
复制
发表时间：
2023-03-16
期刊：
影响因子：
9.4
通讯作者：
Gourlay, C. M.
中科院分区：
文献类型：
--
作者：
Cui, Y.;Xian, J. W.;Gourlay, C. M.
焊点中的大Ag3Sn板会影响电子器件的可靠性，然而，影响其成核和形态的因素尚不清楚。在这里，研究了 Ag3Sn 的多面凝固作为熔体过冷度的函数，揭示了从单晶 {001} 板到循环孪晶板的转变，然后到由孪晶介导的支化产生的高度支化结构。实时X射线成像证明Ag3Sn循环孪晶来自一个共同点，表明它们在过冷熔体中的成核过程或生长的早期阶段开始。焊接到铜基板上显着催化 Ag3Sn 成核。这被证明是由于 Ag 溶质在 Cu6Sn5 反应层之前被排斥到液体中而产生的结构过冷，以及 Cu6Sn5 扇贝之间凹槽中的几何催化作用和 Ag3Sn 在 Cu6Sn5 上的异相成核的额外贡献。 Cu6Sn5 反应层上 Ag3Sn 成核的相对容易性是电子焊点中经常报道的大板的原因。
Large Ag3Sn plates in solder joints can affect the reliability of electronics, however, the factors affecting their nucleation and morphology are not well understood. Here, the faceted solidification of Ag3Sn was studied as a function of melt undercooling, revealing transitions from single crystal {001} plates to cyclic twinned plates and then to highly branched structures created by twin mediated branching. Real-time X-ray imaging proved that Ag3Sn cyclic twins come from a common point, indicating they initiate in the process of nucleation or in the very early stages of growth in the undercooled melt. Soldering to copper substrates significantly catalysed Ag3Sn nucleation. This is shown to be due to constitutional supercooling generated by Ag solute rejection into the liquid ahead of the Cu6Sn5 reaction layer, with additional contributions from geometrical catalysis in the grooves between Cu6Sn5 scallops and heterogeneous nucleation of Ag3Sn on Cu6Sn5. The relative ease of Ag3Sn nucleation on the Cu6Sn5 reaction layer is responsible for the large plates often reported in electronic solder joints.