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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
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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.

    中文摘要 I 英文摘要 II 總目錄 III 表目錄 VI 圖目錄 VII 第一章 前言 1 第二章 文獻回顧 2 2.1 銲錫於電子封裝之上應用 2 2.2 無鉛銲錫合金介紹 2 2.2.1 錫鉛合金與銲錫之無鉛化 2 2.2.2 錫銀銅無鉛銲錫合金 3 2.3 錫銅接合界面 3 2.4 銲點接合強度與破壞特性 4 2.4.1 拉伸與推剪力試驗 4 2.4.2 研究現況 5 第三章 實驗方法 11 3.1 接合試片製作 11 3.2 接合試片組織觀察 11 3.2.1 顯微組織觀察 11 3.2.2 IMC成分分析與試片元素分布 12 3.3 機械性質測試 12 3.3.1 微硬度試驗 12 3.3.2 拉伸試驗 13 第四章 實驗結果 18 4.1 顯微組織觀察結果 18 4.1.1 Sn/Cu界面 18 4.1.2 SAC/Cu界面 19 4.2 微硬度及拉伸試驗結果 20 4.2.1 微硬度試驗結果 20 4.2.2 拉伸試驗結果 20 4.2.2.1 拉伸性質 20 4.2.2.2 拉伸次表面觀察 21 第五章 討論 44 5.1 錫銅固液接合組織特徵 44 5.1.1 界面形貌變化 44 5.1.2 回銲過程中銅原子之行為 44 5.1.3 銀含量效應 46 5.2 接合組織與拉伸破壞特性之關係 47 5.2.1 界面形貌對裂紋傳播之影響 47 5.2.2 拉伸性質與裂紋傳播模式比較 48 5.2.3 接合組織對拉伸性質之影響 49 第六章 結論 62 參考文獻 63 表2-1 常見之無鉛銲錫合金優劣性比較 6 表3-1 不同銲錫成分試片之回銲條件 14 表5-1 錫銅系統之擴散係數 51 圖2-1 錫鉛二元系統相圖 7 圖2-2 錫銀銅三元系統 (溫度單位:℃): (a) Sn-Ag-Cu相圖;(b) 共晶區局部放大 8 圖2-3 錫銀二元系統相圖 9 圖2-4 錫銅二元系統相圖 10 圖3-1 實驗流程圖 15 圖3-2 石墨模尺寸示意圖 (單位:mm) 16 圖3-3 接合試片尺寸示意圖 (單位:mm): (a) 觀察用接合試片;(b) 拉伸用接合試片 17 圖4-1 不同回銲時間Sn/Cu試片界面處OM組織觀察: (a) 10 min;(b) 20 min;(c) 30 min;(d) 60 min 23 圖4-2 EDS分析結果 (回銲60 min之Sn/Cu試片): (a) Cu3Sn;(b)Cu6Sn5;(c) 游離Cu6Sn5相; (d) 晶出Cu6Sn5相 24 圖4-3 Sn/Cu試片IMC層厚度比較 (PL:平面層,CL:柱狀層) 25 圖4-4 不同回銲時間Sn/Cu試片基地內OM組織觀察: (a) 10 min;(b) 20 min;(c) 30 min;(d) 60 min。 26 圖4-5 Sn/Cu試片銅含量與回銲時間比較 27 圖4-6 SAC305/Cu試片OM組織觀察 (界面/基地組織): (a) 20 min;(b) 30 min;(c) 60 min 28 圖4-7 回銲60 min之SAC/Cu試片OM組織觀察 (界面/基地組織): (a) SAC105;(b) SAC205;(c) SAC305 (同圖4-6(c)) 29 圖4-8 IMC平面層 (PL)與柱狀層 (CL)厚度比較: (a) SAC305/Cu試片;(b) 回銲60 min接合試片 30 圖4-9 回銲60 min之SAC/Cu試片共晶區面積率比較 31 圖4-10 SAC305/Cu試片EPMA分析結果: (a) 回銲20 min;(b) 回銲60 min 32 圖4-11 回銲60 min之SAC/Cu試片line scan分析結果: (a) SAC105;(b) SAC205;(c) SAC305 33 圖4-12 不同組織間微硬度比較 (回銲60 min之SAC305/Cu試片) 34 圖4-13 界面附近微硬度變化: (a) SAC305/Cu試片;(b) 回銲60 min接合試片 35 圖4-14 基地內β-Sn微硬度比較 36 圖4-15 SAC305/Cu試片拉伸性質比較: (a) 強度;(b) 延性 37 圖4-16 回銲20 min接合試片拉伸性質比較: (a) 強度;(b) 延性 38 圖4-17 回銲60 min接合試片拉伸性質比較: (a) 強度;(b) 延性 39 圖4-18 SAC305/Cu試片拉伸次表面OM觀察: (a) 20 min;(b) 30 min;(c) 60 min 40 圖4-19 回銲20 min接合試片拉伸次表面OM觀察: (a) SAC105;(b) SAC305 (同圖4-18 (a));(c) Sn 41 圖4-20 回銲60 min接合試片拉伸次表面OM觀察: (a) SAC105;(b) SAC205;(c) Sn 42 圖4-21 SAC305/Cu試片拉伸次表面BEI觀察: (a) 20 min;(b) 30 min;(c) 60 min 43 圖5-1 錫銅固液界面移動示意圖 52 圖5-2 錫銅固液界面IMC形貌成長示意圖 53 圖5-3 圓弧狀界面形貌變化示意圖: (a) 階段I;(b) 階段II;(c) 階段III 54 圖5-4 Sn/Cu試片界面處至基地內組織變化: (a) 10 min;(b) 20 min;(c) 30 min;(d) 60 min 55 圖5-5 回銲60 min之SAC/Cu試片界面處至基地內組織變化: (a) SAC105;(b) SAC205;(c) SAC305 56 圖5-6 三種型態之裂紋傳播模式: (a) 型態I;(b) 型態II;(c) 型態III 57 圖5-7 不同接合試片拉伸強度與IMC層厚度比較: (a) SAC305/Cu試片;(b) 回銲60 min試片 58 圖5-8 不同破壞型態拉伸性質比較: (a) 強度;(b) 延性 59 圖5-9 不同破壞型態拉伸強度與IMC層厚度比較:(a) 型態I; (b) 型態II;(c) 型態III;(d) 基地內部破壞 60 圖5-10 回銲60 min之SAC/Cu試片共晶區面積率與延性比較 61

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