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，所以探討錫鬚晶的生長行為與如何抑制錫鬚是現今電子封裝產業的重要議題。
電子元件在用於電連接的部位鍍上純錫沉積層，所述純錫沉積層為一微晶粒純錫層，其中各晶粒在與沉積表面垂直的方向上的尺寸小於其在與上述沉積表面平行的方向上的尺寸，稱它為非規則錫晶粒結構。研究中利用電子元件的電鍍方法，包括步驟︰調節錫鍍液成分，該錫鍍液包括起始劑和光亮劑；使該電子元件通過該錫鍍液，以在該電子元件的用於電連接的部位沉積一微晶粒純錫層的方式。利用實驗計畫法中，將不同錫粒結構及厚度組合，再經由高溫高濕及室溫錫鬚測試後，發現非規則錫晶粒結構的腐蝕機制，金屬間化合物的表面,及錫原子本身的擴散行為，總合研究結果後，與現有常見結構相比，其具有可有效防止錫鬚產生之優點。

In past years, legislative pressures (particularly in Japan and Europe) had forced the electronics industry to eliminate Pb from their end products and manufacturing processes. With respect to factors such as ease of converting existing tin-lead plating systems, ease of manufacture and compatibility with existing assembly methods, pure tin plating is seen by many in the industry as a potentially simple and cost effective alternative to SnPb-based systems. The problem of spontaneous tin whisker formation, a characteristic of pure tin, still needs to be addressed, as it can lead to device failure by shorting two terminals on electronic devices. This possibility gives rise to major reliability concerns.
The study relates to an electronic component with pure tin deposit layer on the part for electric connection, wherein pure tin deposit layer is a fine grained tin deposit layer composed of grains with smaller size in the direction perpendicular to the deposit surface than in the direction parallel to the deposit surface. It is called irregular tin grain structure. It applies a process for plating an electronic component, so as to form a pure tin deposit layer on the part for electric connection, comprising the steps of: adjusting the composition of tin plating solution in which starter additive and brighter additive are included; moving the electronic component through the tin plating solution, so as to form a fine grained tin deposit layer on the part for electric connection. We performed a DoE by depositing different tin grain structures with variant thickness. After whisker test in high temperature/high humidity and room condition, we confirmed corrosion mechanism, intermetallic morphology, and different behaviour of tin atoms. To summarize the studies, as compared with the prior arts, irregular grain structure can validly inhibit the whisker growth.

1 Introduction 1
2 Literature review 4
2.1 Substrate effects 4
2.2 Plating thickness 5
2.3 Grain size and shape 6
2.4 Environmental stresses 6
2.4.1 Temperature 6
2.4.2 Moisture 7
2.4.3 Thermal cycling 8
2.5 Internally applied mechanical stresses 8
2.5.1 Plating chemistry and process 8
2.5.2 Diffusion of substrate elements into tin layer 9
2.5.3 Intermetallic formation 9
2.6 Externally applied mechanical stress 9
2.7 Electric field 10
2.8 NEMI Survey rank 10
3 Hypothesized mechanism 12
4 Experiment 18
4.1 Purpose 18
4.2 Sample preparation 20
4.3 Whisker test 22
4.4 Analysis method 23
5 Result and discussion 25
5.1 Deposit grain structure next to the substrate material 26
5.2 Whole thickness of the deposit layer 28
5.3 Thickness of irregular grain structure on the bottom layer 29
5.4 Plating thickness of the deposit layer close to the deposit surface 29
5.5 Deposit grain structure close to the deposit surface 30
5.6 Plating condition 31
5.7 Different copper based material 32
5.8 Corrosion mechanism 33
5.8.1 Vertical columnar grain structure (Type C) 35
5.8.2 Irregular grain structure (Type B) 36
5.8.3 Mixed grain structure (Type C+B) 37
5.8.4 Corroded Tin composition 39
5.9 Confirmation of whole IMC morphology 39
5.9.1 Vertical Columnar grain structure (Type C) 40
5.9.2 Semi-columnar grain structure (Type A) 41
5.9.3 Irregular grain structure (Type B) 42
5.9.4 Mixed type I (A+C) 43
5.9.5 Mixed type II (B+A) 43
5.9.6 Mixed type III (A+B) 44
5.10 Stress release behavior within various grain structures 45
5.10.1 Vertical columnar type grain structure (Type C) 46
5.10.2 Semi-columnar grain structure (Type A) 46
5.10.3 Irregular type grain structure (Type B) 47
5.10.4 Mixed type structure (Type B+A) 48
5.10.5 Theory of stress release behavior 48
5.11 Micro-structure confirmation 50
6 Conclusion 52
7 Reference 55
8 Appendix 61

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