一般我們常見的電子資訊產品，含多樣主動及被動元件，其封裝積體電路IC是最主要的零件，而其可靠度(reliability)將決定整個產品的壽命和是否可以運作的最主要關鍵。因此必須將晶片有效且可靠的封裝起來，而且由線路接點外接至印刷電路板上運作，這方面的技術統稱電子構裝。
一般在導線架上電鍍材料的選擇，錫鉛合金為最受歡迎的材料，但基於法令與環保意識的高漲，而且鉛有害人體，被禁止使用，因此純錫適合作為替代材料。然而使用純錫會有自發性的錫鬚成長（tin whisker growth）問題，會造成IC短路而使整個元件失效，而現今的元件以輕薄短小為趨勢，接腳和其間距勢必也跟著變小變窄，因此錫鬚成長的問題顯得更為重要。所以探討錫鬚晶的生長行為與如何抑制錫鬚的生長是現今電子封裝產業的重要議題。
而在大部分的文獻研究中，皆認同tin whisker是由於壓應力所造成，瞭解壓應力來源並且加以消除是解決tin whisker的根本之道。文獻提到的壓應力主要來源為(1)介金屬化合物的生成，(2)基材/鍍錫層膨脹係數差異的界面應力，(3)導線架沖切的加工殘留應力等。因此本研究的第一個實驗重點在於Cu/Sn介金屬化合物的形成對錫鬚晶成長的探討，結果發現在室溫下Cu6Sn5的介金屬為主要的相，並且會沿著鍍錫層生長而對鍍錫層產生壓應力，因此藉由whisker的生長來釋放壓應力。
而在本研究的第二到第四個部分將探討不同的鍍錫層電鍍條件（溫度、預先鍍鎳層的選用以及使用不同電鍍錫液的配方）與錫鬚晶成長之間的相關性研究，進而改善抑制錫鬚成長。在溫度對錫鬚晶成長的影響方面，在150°C下，IMC為層狀生長，對鍍錫層是造成張應力，因此沒有觀察到whisker的生長，故將試片在150°C下前處理1小時可以有效的防止錫鬚的生長。在鍍鎳層對錫鬚晶成長的影響方面，在銅基板上加上一層大約1

New environmental regulations enforce the electronic industry to replace Pb-Sn solder due to Pb could contaminate our environment. Pure Sn has good material properties such as solderability, conductivity and anti-corrosion. Pure Sn is a good candidate to replace Pb-Sn solder. One of the disadvantages of pure Sn is the whisker growth phenomenon. Whisker problem has become a major concern in electronic industry due to the trend toward component miniaturization and pitch reduction.
It is well understood that the root cause for tin whisker growth is the compressive stress within the tin layer. In the literature, the main stress sources are, (1) the intermetallic layer induced interface stress, (2) the difference of thermal expansion coefficient between Sn layer and substrate and (3) the mechanical residual stress from trim-form operation after tin plating. In our study, we used the electrochemical electrolysis method and Cross-section Polisher (CP) to examine the tin whisker growth mechanism. In the result, we can clearly show the Cu6Sn5 phase grow up in the tin grain boundary regions and demonstrate that the Cu6Sn5 phase formation is the main cause of the tin whisker growth.
We also discuss the relationship of tin whisker growth and tin-plating process parameters that include the temperature effect; Ni underlay effect and tin-plating bath effect. For the temperature effect, the Cu6Sn5 is the major phase at 150°C aging. The mechanism behind its growth mechanism was grain boundary diffusion at the earlier stage and then the bulk diffusion in the later stage. The application of 150°C post-heat treatment could drive the bulk diffusion and form a layer type Cu6Sn5 phase to eliminate the whisker growth. For the Ni underlay effect, the Ni underlay can block the Cu atom diffusion to the tin layer and changed the tin layer stress state from compressive to tensile. Therefore, the tin whisker can be eliminated. For the tin-plating bath effect, in the sulfuric acid base and uses Triton X-100 as the surface active agent, may transform the whisker type to particular tin grain type. Thus, this tin-plating solution can restrain the tin whisker growth.

壹、前言 1
1-1 研究背景 1
1-2 研究動機 2
貳、文獻回顧 3
2-1 Development of metallic whisker 3
2-2 Cu/Sn and Ni/Sn interfacial reactions 3
2-2-1 Cu/Sn interfacial reactions 4
2-2-2 Ni/Sn interfacial reactions 5
2-3 Whisker growth mechanism 5
2-4 Factors of Whisker Growth 6
2-4-1 Substrate material 6
2-4-2 Plating material 7
2-4-3 Grain Size and Shape 7
2-4-4 Plating thickness 8
2-4-5 Stress 9
2-4-6 Temperature 9
參、實驗方法 11
3-1 錫鬚生長的研究 11
3-1-1 實驗目的 11
3-1-2 試片製作 11
3-1-3 試片處理 12
3-1-4 試片分析 12
3-2 溫度對錫鬚成長影響的研究 12
3-2-1 實驗目的 12
3-2-2 試片製作 12
3-2-3 試片處理 13
3-2-4 試片分析 13
3-3 鍍鎳層對錫鬚生長的影響 13
3-3-1 實驗目的 13
3-3-2 試片製作 13
3-3-3 試片處理 14
3-3-4 試片分析 14
3-4 使用不同配方的鍍錫液對鍍錫層的影響 14
3-4-1 實驗目的 14
3-4-2 試片製作 14
3-4-3 試片處理 15
3-4-4 試片分析 15
肆、研究結果 16
4-1 錫鬚生長的研究 16
4-1-1 室溫下錫鬚生長的觀察 16
4-1-2 室溫下IMC生長的觀察 16
4-2 溫度對錫鬚成長影響的研究 17
4-2-1 150°C前處理一個小時後室溫下表面鍍錫層的觀察 17
4-2-2 150°C下IMC生長的觀察 17
4-3 鍍鎳層對錫鬚生長的影響 18
4-4 使用不同配方的鍍錫液對鍍錫層的影響 19
4-4-1 硫酸base B tin grain growth的觀察 19
4-4-2 硫酸base B IMC生長的觀察 20
伍、研究討論 22
5-1 錫鬚生長的研究 22
5-1-1 錫鬚晶生長機制的探討 22
5-1-2 厚度對錫鬚生長的影響 23
5-1-3 應力的計算 24
5-1-4 錫鬚晶生長長度的估算 24
5-2 溫度對錫鬚晶生長影響的探討 27
5-2-1 150°C前處理一個小時後對錫鬚生長的影響 28
5-2-2 應力的計算 28
5-2-3 150°C下Cu-Sn IMC與孔洞的生長機制 29
5-2-4 150°C下Cu-Sn IMC的生長曲線圖 30
5-2-5 150°C下時效前處理時間的決定 31
5-3 鍍鎳層對錫鬚晶生長影響的探討 31
5-3-1 應力產生的計算 32
5-3-2 Ni-Sn IMC與孔洞的生長機制 32
5-3-3 Ni underlay厚度的決定 33
5-4 使用不同鍍錫液對鍍錫層的影響研究 34
5-4-1 特殊錫晶粒的生長機制 35
5-4-2 溫度對錫晶粒生長的影響 35
5-4-3 鍍鎳層對錫晶粒生長的影響 36
5-5 甲基磺酸base與硫酸base鍍錫層表面結構的比較 37
5-6 Ni-underlay與Non-underlay鍍錫層表面結構的比較 38
5-7 錫鬚生長改善防制的探討 39
陸、結論 41
柒、參考文獻 44
捌、圖 51

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