The predicted growth behavior of intermetallic compound (IMC) induced by electromigration of a Cu/organic solderability preservative (OSP)/Sn-2.5Ag solder/electroless nickel electroless palladium immersion gold (ENEPIG)/Cu joint was calculated for a current density of 14 kA/cm² and current application time of 600 h and validated experimentally. Under as-reflow conditions, thin Cu₃Sn and scallop-shaped Cu₆Sn₅ layers were produced near the OSP interface, and a (Cu, Ni)₆Sn₅ layer was formed near the ENEPIG interface. Cu₆Sn₅ islands and Ag₃Sn with a β-Sn matrix were formed in the solder. The mobilities of Cu, Ni, and Sn atoms at the OSP and ENEPIG interfaces were calculated, and a relationship was found between IMC thickness and current application time. Under electron flow from the OSP to ENEPIG interface, the predicted total thickness (26.6 μm) of the IMCs (Cu₃Sn, Cu₆Sn₅, and (Cu, Ni)₆Sn₅), was in agreement with the experimental value (24.7 μm). With electron flow reversed, the predicted IMC thickness (14.2 μm) was similar to the experimental value (13.2 μm). The application of current during electromigration only coarsened Cu₆Sn₅, regardless of the direction of electron flow. Finally, the Ni plating layer on the ENEPIG surface finish prevented the diffusion of Cu and suppressed electromigratory IMC growth by approximately 50%.

Graphic abstract

中文翻译：

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在具有 OSP 和 ENEPIG 表面处理的 Sn-2.5Ag 焊点中由电迁移引起的金属间化合物生长的原位观察和建模

Cu/有机可焊性保护剂 (OSP)/Sn-2.5Ag 焊料/化学镀镍化学镀钯浸金 (ENEPIG)/Cu 接头电迁移引起的金属间化合物 (IMC) 的预测生长行为计算为电流密度为 14 kA/cm ²和 600 小时的电流应用时间并通过实验验证。在回流条件下，在OSP界面附近产生薄的Cu ₃ Sn和扇贝形Cu ₆ Sn _{5层，在ENEPIG界面附近形成(Cu, Ni) 6} Sn ₅层。Cu ₆ Sn ₅岛和 Ag ₃在焊料中形成具有 β-Sn 基体的 Sn。计算了 OSP 和 ENEPIG 界面处 Cu、Ni 和 Sn 原子的迁移率，并发现了 IMC 厚度与电流施加时间之间的关系。_{在从 OSP 到 ENEPIG 界面的电子流下，IMC（Cu 3} Sn、Cu ₆ Sn ₅和（Cu，Ni）₆ Sn ₅ ）的预测总厚度（26.6 μm）与实验值一致（ 24.7 微米）。随着电子流的逆转，预测的 IMC 厚度 (14.2 μm) 与实验值 (13.2 μm) 相似。在电迁移过程中施加电流只会粗化 Cu ₆ Sn ₅，无论电子流向如何。最后，ENEPIG 表面光洁度上的 Ni 镀层阻止了 Cu 的扩散并将电迁移 IMC 生长抑制了大约 50%。

图形摘要