覆晶(Flip-Chip)接合封裝技術中，一個銲錫凸塊往往連結兩個不同的金屬化墊層UBM (Under Bump Metallization)。當兩種完全不同的UBM結構與銲錫形成接點時，銲錫會與Ni墊層與Cu墊層同時發生界面反應。此種兩界面反應交互作用是一個非常重要且值得探討的問題。第一章回顧有關Sn/Ni與Sn/Cu兩界面反應交互影響的報導，我們發現Cu原子自Cu墊層溶解進入銲錫並擴散至Sn/Ni界面生成Cu-Sn化合物。此一Cu原子擴散的驅動力來自於靠近Sn/Ni界面的Cu溶解度降低而造成銲錫中存在一Cu的濃度梯度。本論文進一步利用一系列不同的metal/Sn/Cu三明治結構來探討兩個不同界面反應間其交互作用。 第二章中，將深入探討Ni/Sn/Cu三明治結構中Cu原子擴散的動力學機制。經短時間的迴銲反應，Cu端為典型Cu6Sn5化合物，而一三元化合物(Cu,Ni)6Sn5於Ni端生成。長時間的迴銲反應後，發現Cu端的Cu6Sn5化合物生長厚度隨時間的增加而維持一定厚度值，相反地，Ni端的(Cu,Ni)6Sn5生長迅速並與時間則呈一線性關係。由結果得知，此三元化合物(Cu,Ni)6Sn5的生長由Sn/Cu6Sn5界面的Cu dissolution flux所控制。經計算Cu6Sn5化合物於液態錫的溶解常數為0.13 ( It has been reported that as Ni and Cu bond pads are soldered to form a joint, Sn/Ni and Sn/Cu interfacial reactions would interact mutually, as reviewed in chapter 1. The dissolved Cu atoms from the Cu pad would move toward the Ni pad, then, a Cu-Sn compound layer formed on the Sn/Ni interface. In our previous study, the driving force of the migration of dissolved Cu atoms toward the Ni side has been proposed to attribute to the reduction of the Cu solubility near the Sn/Ni interface. This dissertation discusses the coupling effects between two interfacial reactions using a series of different metal/Sn/Cu sandwich structures. In chapter 2, we further study the Cu diffusion mechanism in Ni/Sn/Cu sandwich structure. Using Ni/Sn/Cu sandwich sample, the mutual interaction between Sn/Ni and Sn/Cu interfacial reactions has been studied. On the Cu side, the major interfacial reaction product is Cu6Sn5, on the other hand, a ternary (Cu,Ni)6Sn5 compound layer formed on the Ni side. We found that the growth kinetics of the interfacial compound layers on the both sides would reach a steady-state in the late stage of reflow. The interfacial compound layer on the Cu side would remain a constant thickness. On the contrary, the interfacial compound layer on the Ni side grew in a relatively fast rate, which was found to be linear with time. Our results indicate that the growth of the ternary (Cu,Ni)6Sn5 compound layer was controlled by the Cu dissolution flux at the solder/Cu6Sn5 compound interface. The dissolution constant of the Cu6Sn5 compound into the molten Sn was determined to be 0.13 (
