摘要
在全球環保意識抬頭綠色化影響之下，加上歐盟在其RoHS指令中明確要求在2006年7月起，任何於歐洲銷售之電子產品皆不可含有鉛、鎘等有害物質，故未來電子產品無鉛化勢在必行。 本論文乃探討無鉛銲料與Pt、Cu基材間之界面反應，欲了解以Pt墊層取代原先之Au/Ni表面處理層之界面反應。本論文將報導SnAg-Cu銲料中銅濃度變化對於銲料與Pt基材介面反應之影響，觀察界面生成物之種類、微結構以及形態變化；此外，為了解Pt、Cu間之交互作用，另以SnAg-Pt銲料與Cu基材進行反應作為對照組，以利分析。 第一部份實驗選用Sn3Ag和Sn3Ag0.5Cu分別與Pt基材進行界面反應，由固/液反應以及固/固反應之實驗結果可觀察到界面皆生成一層連續之PtSn4介金屬。然而固/固反應時，發現在SnAg銲料中添加適量的Cu元素可有效的抑制界面PtSn4介金屬之生長。 第二部份實驗選用Sn3.5Ag-xCu銲料，(其中x =2、5及10 (wt.%))。研究發現固/固反應時，銲料中Cu濃度介於2-10 wt.%範圍時，Cu濃度對於抑制PtSn4介金屬之生長效果並無明顯差異，但仍優於銲料中Cu濃度為0.5 wt.%時之抑制效果。此外，當熱處理時間拉長至2000小時時，銲料內之化合物Cu6Sn5與Ag3Sn已回到界面形成一層連續層覆蓋在PtSn4上。 另外一組對照組選用Sn3.5Ag-yPt銲料，其中y分別為0.5、1及3(wt.%)，與Cu基材進行界面反應。有趣的是，在液態中，隨著Pt濃度的增加，界面介金屬Cu6Sn5之微結構有顯著的差異，分別有層狀、圓形、柱狀以及扇貝狀的形態。 上述之研究結果中得知在SnAgCu/Pt亦或SnAgPt/Cu系統中，依EPMA偵測反應生成物PtSn4 與Cu6Sn5 化合物鑑定之結果得知：PtSn4內未偵測到Cu之訊號，於Cu6Sn5內亦無Pt之訊號，故Pt-Sn系統及Cu-Sn系統的二元反應是獨立的，Pt與Cu無交互影響、無交互作用。 若欲以Pt取代Au/Ni表面處理層，需具有良好之潤濕性。故測試Pt與SnAg0.5Cu無鉛銲料間之潤濕性質，取Ni基材作為對照組。整體而言，使用RMA助銲劑時，Pt、Ni基材之潤濕性質皆優於水溶性助銲劑；就Pt、Ni之潤濕性質而言，Ni之潤濕性稍優於Pt。但Pt之潤濕性仍在可接受的範圍內。
並列摘要
Au/Ni is the most common surface finishes for Cu soldering pads in ball-grid-array (BGA) and other electronic packages. The Au layer is for oxidation protection, and the Ni layer serves as a solderable diffusion barrier. Platinum also has good properties for a wetting layer. Because platinum has a lower dissolution rate than nickel and good resistance to oxidation, gold is not needed for oxidation protection. The object of this investigation is to study interaction between Sn-rich solder contain a small amount of copper and platinum and copper substrate. Firstly, Sn-3Ag, Sn-3Ag-0.5Cu were reacted with platinum by typical reflow process at a peak reflow temperature of 235 ℃. After reflow, a continuous intermetallics layer formed at the solder/platinum interface. Comparing the interfacial reaction of the Sn-3Ag system with the Sn-3Ag-0.5Cu system, Sn-Ag solders contain a small amount copper can suppress the consumption rate of platinum effectively. Secondly, Sn-3.5Ag-xCu (x = 2,5, and 10 wt.%) were reacted with platinum by reflow at 250 ℃. After aging, the consumption rate of platinum of the concentration of copper between 2-10 wt.% is slower than the concentration of copper is 0.5 wt.%. The extents of suppressing the growth rate of PtSn4 for the cases with Cu concentration from 2 to 10 wt% are almost the same. After 2000 h aging, a continuous IMCs layer formed and covered in the PtSn4. Thirdly, Sn-3.5Ag-yPt (y = 0.5,1, and 3 wt.%) were reacted with copper by reflow at 250 ℃. In the liquid reaction, the morphology of Cu6Sn5 depended on the composition of platinum in the solder. However, the result of EPMA analysis showed that the copper signal can not be detected in the PtSn4 intermetallic compound and the platinum signal can not be detected in the Cu6Sn5 intermetallic compound in the SnAgCu/Pt and SnAgPt/Cu system. On the other word, the binary reaction of Pt-Sn system and Cu-Sn system is independent. There is no interaction between Pt and Cu. Finally, wetting properties of Sn-3Ag-0.5Cu on Pt and Ni substrates at 240 °C were determined by using a wetting balance technique. In the analysis of wetting time, the wettability of Pt was close to Ni.
參考文獻
延伸閱讀
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