本研究探討Sn/Co、Sn/(Ni,Co)在250°C下之界面反應。多數之無鉛銲料組成主要以Sn為主。近年來銅導線製程已成為電子元件內導線(interconnect)的主流。在元件製作完成之後，須將積體電路和其他相關的電子或訊號電路，共同連接於一系統中，以提供電能輸入與訊號溝通的連線，或提供此晶片系統操作時所需要的機械強度。近年來覆晶技術在電子構裝中受到極大的重視，在銲料與UBM多層金屬間之界面反應更顯重要，(Ni,Co)合金為UBM阻障層的材料系統之ㄧ，以避免銲料直接與線路反應，造成電子元件通路失效。
本研究製備不同組成之Sn-Ni-Co合金，藉由熱處理、金相分析、組成分析，以探討Sn/Ni-Co之界面反應與Sn-Ni-Co三元系統之250oC相平衡等溫橫截面圖。Co-Sn與Ni-Sn的二元介金屬相分別具有相當顯著的Ni與Co之溶解度。在250oC，CoSn3與CoSn2之Ni溶解度分別為9.12at%與30.4at%，Ni3Sn4之Co溶解度為18.87at%，但它們在Sn組成上的變化上則很小。值得注意的是Sn-Ni-Co三元系統中存在一個三元相之單相區(Ni,Co)Sn4。
Sn/Co的界面反應，在24小時內，Sn/Co界面生成相皆為單純的CoSn3，Sn/Ni-1at%Co和Sn/Ni界面反應類似，界面生成相皆為單純的Ni3Sn4，而Sn/Ni-3at%Co、Sn/Ni-3at%Co界面生成相為(Ni,Co)Sn4及Ni3Sn4，Sn/Ni-20at%Co界面生成相包括一薄層結構，厚度約5~10□m，為相圖上並不存在的介穩相(metastable phase)，暫定為(Ni,Co)3Sn7相，以及由此上述薄層凹處長出的樹枝狀結構，厚度約350□m，為相圖上存在的(Ni,Co)Sn4穩定相，經TEM鑑定後(Ni,Co)Sn4為一結晶結構(crystalline)。Sn/Ni-40at%Co反應初期出現(Ni,Co)2Sn7相，經TEM觀察分析後期繞射圖譜與(Ni,Co)3Sn7類似，同樣呈現散亂的繞射點與streak，反映出(Ni, Co)2Sn7與(Ni, Co)3Sn7之結構相類似，都是小晶粒組成，且都疑似有第二相的存在。(Ni,Co)3Sn7亦為一介穩相，Sn/Ni-40at%Co反應8小時後出現CoSn2穩定相。
在250℃左右，在1000小時內，Sn/Ni之界面反應只觀察到Ni3Sn4相。但由Sn/Ni-Co的界面反應可以發現與Ni/Sn界面反應截然不同，表示加入Co之後界面生成相會有很大變化，將對Sn/Ni界面反應造成相當程度的影響。

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