Efficient diffusion barriers are necessary to prevent the formation of copper-tin intermetallic compounds (IMCs) in advanced packaging for Sn/Cu micro-bumps. This study investigated the interfacial properties of solder and Ni, Co-9W, Co-20W, Co-20Fe-10W, and Co-36Fe-17W barriers and determined the thickness of IMCs formed between Sn and these barriers after up to 15 reflows. Among the five barriers, Co-36Fe-17W proved to be the most effective in inhibiting the reaction of liquid Sn solder. At the Sn/Co-W interface, CoSn₃ IMC was formed, while at the Sn/Co-Fe-W interface, CoSn₃ IMC and FeSn₂ IMC were observed. The contact angles of these layers were measured and found to be 18°, 22°, 25°, 29°, and 27°, respectively. The results showed that an increase in W content in Co-W led to an increase in the contact angle, while the intrinsic wettability of Co-Fe-W decreased with an increase in Fe content. The shear strengths of the five joints were 27 MPa, 31 MPa, 25 MPa, 25 MPa, and 26 MPa, respectively, with different fracture modes observed. The Co-Fe-W-Sn layer was partially peeling from the diffusion barriers in SAC305/Co-20Fe-10W, and the fracture surfaces exhibited an irregular and rough state, which was attributed to the increasing Fe and W contents. These findings offer valuable insights for enhancing the reliability of electronic packages.

Graphical Abstract

中文翻译：

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回流条件下 Co-W 和 Co-Fe-W 扩散势垒对焊料/Cu 界面可靠性的影响

有效的扩散阻挡层对于防止 Sn/Cu 微凸块先进封装中铜锡金属间化合物 (IMC) 的形成是必要的。本研究研究了焊料与 Ni、Co-9W、Co-20W、Co-20Fe-10W 和 Co-36Fe-17W 阻挡层的界面特性，并确定了经过 15 次回流后在 Sn 和这些阻挡层之间形成的 IMC 的厚度。在五种屏障中，Co-36Fe-17W 被证明是抑制液态锡焊料反应最有效的。在Sn/Co-W界面处，形成CoSn ₃ IMC，而在Sn/Co-Fe-W界面处，观察到CoSn ₃ IMC和FeSn ₂ IMC。测量这些层的接触角，发现它们分别为18°、22°、25°、29°和27°。结果表明，Co-W中W含量的增加导致接触角增大，而Co-Fe-W的固有润湿性随着Fe含量的增加而降低。 5个接头的剪切强度分别为27 MPa、31 MPa、25 MPa、25 MPa和26 MPa，观察到不同的断裂模式。 SAC305/Co-20Fe-10W 中 Co-Fe-W-Sn 层从扩散势垒中部分剥离，断口呈现不规则且粗糙的状态，这归因于 Fe 和 W 含量的增加。这些发现为提高电子封装的可靠性提供了宝贵的见解。

图形概要