| 研究生: |
賴彥均 Lai, Yen-Chun |
|---|---|
| 論文名稱: |
SAC/Cu之回銲界面組織演變與拉伸破壞特性研究 A Study on the Interfacial Microstructure and Tensile Fracture Characteristics of Reflowed SAC/Cu Joints |
| 指導教授: |
陳立輝
Chen, Li-Hui 呂傳盛 Lui, Truan-Sheng |
| 學位類別: |
碩士 Master |
| 系所名稱: |
工學院 - 材料科學及工程學系 Department of Materials Science and Engineering |
| 論文出版年: | 2009 |
| 畢業學年度: | 97 |
| 語文別: | 中文 |
| 論文頁數: | 67 |
| 中文關鍵詞: | 界面 、銲錫 、錫銀銅 、回銲 、拉伸 |
| 外文關鍵詞: | solder, SAC, reflow, interface, tensile |
| 相關次數: | 點閱:96 下載:4 |
| 分享至: |
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銲錫合金常用於電子封裝中做為線路之間訊號連結使用。銲錫與銅基板接合後,其界面處IMC層之組織形貌隨著回銲條件之不同而異。SAC305 (Sn-3.0 wt.%Ag-0.5 wt.%Cu)為常用之無鉛銲錫合金,近年來低銀含量化之相關研究甚多,然銀含量對接合特性之相關影響仍尚待釐清。本實驗將Sn及SAC (SAC105、SAC205及SAC305)合金分別與銅進行回銲,在10 min至60 min範圍之回銲時間內,觀察錫銅固液界面特徵與變化。此外亦將各試片進行拉伸試驗,觀察固液界面組織演變對拉伸破壞性質之影響。
實驗結果顯示,隨著回銲時間增長,界面附近局部反應較劇烈之位置生成IMC層,並因銅基材發生熔融,界面有往銅端遷移傾向。隨著錫湯內因銅之溶入導致銅含量濃度上升,促進界面附近IMC組織成長。結果導致界面附近游離相、基地內晶出相數量亦有增加趨勢。SAC合金中,銀含量較高試料之界面成長速率較快,此時由於銀原子不直接參與界面反應,因此凝固後試料之基地組織變化大致相同於塊材,隨銀含量增加共晶區面積為增加傾向。此外,界面處IMC層與銲錫基地間微硬度差異極大,導致拉伸變形過程於IMC與基地交界處發現為裂紋產生之初始位置。裂紋傳播方式主要沿著IMC層與基地交界處傳播,以及界面附近游離IMC相間之連結,其中主裂紋於基地內沿著共晶區傳播。SAC合金中,銀含量較高之試料,由於基地內共晶區較大,導致裂紋主要沿基地內共晶組織傳播。
總之,回銲時間較短者其裂紋傳播以界面IMC層為主,拉伸強度隨IMC層厚度增厚而上升,此時延性極低。回銲時間較長者則傾向為界面附近游離相沿共晶相串連為主,其拉伸強度不受IMC層厚度影響,延性亦較前者為高。SAC合金中,銀含量較高試料裂紋傾向在基地內之共晶相傳播,顯示其延性值高於銀含量較低試料。
Solder joints serve as electrical connections in electronic packages. In solder/substrate interface, IMC forms and the morphology changes with different reflow processes. Lead-free SAC305 solder is used in recent year, researches on SAC solder were trended to low Ag contents, but the effect of Ag and IMC morphology on the joint properties is still unknown. In this study, the IMC microstructure revolution of Sn/Cu and SAC/Cu joints with 10~60 min reflow time is investigated. Besides, with the tensile test, its effect on tensile fracture characteristics is discussed.
The results showed that after reflow soldering, Cu was partially molten and interface between solder and Cu moved to Cu side. As reflow time increased, Cu contents in solder has rosen, IMC layer grew and some IMC was found in solder matrix near solder/Cu interface. In SAC solder, high Ag contents induced fast interface growth rate. Ag didn’t react in interface directly, and the eutectic area in matrix was increased as Ag contents rising. In addition, because of great hardness difference, cracks initiated at IMC/solder and propagated at interface IMC layer or eutectic area in matrix. In SAC solder, high Ag contents with large eutectic area let the cracks propagate in matrix easily.
When reflow time is short, crack prefers to initiate at IMC layer, its joint strength rising as thickness of IMC layer grows, but the elongation is very low. As reflow time increasing, cracks become to initiate at the IMC in matrix near solder/Cu interface. In this case the thickness of IMC layer has no effect on joint strength, and elongation has increased. In SAC solder, the elongation increase as Ag contents rising because the cracks prefer to propagate in matrix with high Ag contents.
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