臺灣博碩士論文加值系統

銅墊層與錫銲料接點是現今微電子構裝工業中最為廣泛使用且相當可靠的銲點系統之一。因此，銅錫交互擴散系統的相關研究至今仍被眾多學者們探討著。然而，銅錫二元系統界面生成的介金屬層Cu3Sn和Cu6Sn5對銲點可靠度具有極大的影響。因此，釐清銅錫介金屬Cu3Sn和Cu6Sn5的生成與成長機制對於未來無鉛銲點的發展是相當重要的。在此博士論文中，將深入探討銅墊層與錫銲料間的界面反應。於第三章，我們首先探討銅錫擴散偶(diffusion couple)在不同溫度下其三個決定介金屬成長的界面，Cu/Cu3Sn(界面I)、Cu3Sn/Cu6Sn5(界面II)和Cu6Sn5/Sn(界面III)在銅錫交互擴散中的位移和位移方向，藉以了解介金屬的成長過程。由掃描式電子顯微鏡(Scattering Electron Microscopy, SEM)的分析結果指出當擴散達到平衡時:(1)介金屬Cu3Sn和Cu6Sn5的厚度比(或介金屬成長速率比)趨近一個定值(REquilibrium)。(2)界面II(Cu3Sn/Cu6Sn5)的位移停止。針對此現象，我們將做一系列深入的固態擴散動力學探討，以釐清在銅錫交互擴散達平衡的狀態下，介金屬Cu3Sn和Cu6Sn5的成長機制。此外，根據擴散達平衡的狀態下，建立一個動力學的模型來估算銅原子和錫原子在介金屬Cu3Sn和Cu6Sn5的本質擴散係數(DIMCs)。最後在第四章，我們將深入探討銅基材微結構(銅晶格優選方向)對銅錫界面反應中介金屬的成長和Kirkendall voids生成的影響。結果指出，由高晶格優選方向(111)和(220)銅基材所構成的銅錫銲點，其界面Kirkendall voids的生成相當的劇烈且伴隨著介金屬Cu3Sn異常的成長機制。

Cu-based bond-pad/Sn-based solder is the most common and reliable soldering system in the current electronic package industry. Investigation of IMC layer formation and growth is important for the further optimization of Pb-free soldering. Hence, the interfacial reaction between Sn-based solders and Cu bond pad has become a serious issue for the solder joint. In this work, we will first investigate three interfaces (Interface I: Cu/Cu3Sn; Interface II: Cu3Sn/Cu6Sn5; and Interface III: Cu6Sn5/Sn) displacement and direction in various reaction temperatures for observing the detailed evolution of the IMCs growth. Aged Sn/Cu couples were examined by the metallurgical examination, SEM (Scattering Electron Microscopy) analysis to investigate the IMCs (Cu3Sn and Cu6Sn5) growth in solid-state reaction. The results indicate that as the interdiffusion reach equilibrium stage: (1) the thickness ratio, (or growth rate ratio) between Cu3Sn and Cu6Sn5 layers tend to a constant (REquilibrium) during the interfacial reaction, and (2) the movement of the interface II (Cu3Sn/Cu6Sn5) is almost stationary. According to this phenomenon, we will discuss with the detail growth kinetics of the Cu-Sn intermediate phases, (Cu3Sn and Cu6Sn5) layers which are defined by the movement of three interfaces (Cu/Cu3Sn, Cu3Sn/Cu6Sn5, and Cu6Sn5/Sn) in Chapter 3. Furthermore, we will construct a reliable kinetic model to evaluate the intrinsic diffusivity of Cu and Sn atoms in the Cu3Sn and Cu6Sn5 layers. In Chapter 4, we discussed the microstructure effect of the Cu substrate on Cu-Sn intermetallic compounds evolution and Kirkendall voids formation. While highly (111) and (220) preferred-orientation Cu substrates reacted with Sn, serious Kirkendall voids formed at the interfaces between Sn and (111) and (220) preferred-orientation Cu substrates. Also, the abnormal Cu3Sn growth was found to highly associate with serious Kirkendall formation.

Table of contents
Abstract (Chinese) I
Abstract (English) II
Table of contents III
List of figures VI
List of tables IX
Chapter 1 Background 1
1.1 The evolution of the electronic IC packaging technology 1
1.2 Pb-free solders 3
1.3 Introduction of Cu-Sn interdiffusion system 6
1.4 Diffusion properties of the Cu-Sn interdiffuison system 8
1.5 Kirkendall effect in solid-state diffusion 11
1.6 Kirkendall voids in Cu-Sn solder joint 14
Chapter 2 Motivation 17
2.1 Diffusion parameters and growth mechanism of IMCs in Cu-Sn system 17
2.2 Microstructure effect of Cu substrate on interfacial reaction and Kirkendall voids formation with Sn solders 18
Chapter 3 Mechanism of IMCs growth in Cu-Sn system 19
3.1 The IMCs evolution in Cu/Sn solder joint 19
Experimental procedures 19
Experimental results 19
3.2 Growth kinetics of interfacial Cu3Sn and Cu6Sn5 in solid-state diffusion 27
Discussion 28
Conclusion 31
3.3 The relationships between four atomic fluxes ("J" _("Cu," 〖"Cu" 〗_"3" "Sn" ), "J" _("Cu," 〖"Cu" 〗_"6" "S" "n" _"5" ), "J" _("Sn," 〖"Cu" 〗_"3" "Sn" ), and "J" _("Sn," 〖"Cu" 〗_"6" "S" "n" _"5" )) in Cu-Sn interdiffusion 33
Discussions 33
Conclusion 36
3.4 Determination of the intrinsic diffusivities in Cu3Sn and Cu6Sn5 37
Discussions 37
3.5 The IMCs evolution and the growth kinetic in Cu/ electroplating Sn joint 42
Experimental Results 42
Discussions 42
Conclusion 44
3.6 Summary 46
Chapter 4 Microstructure effect of the Cu substrate on the formation of Kirkendall voids in the Cu-Sn system 47
4.1 The evolution of Cu-Sn interfacial compounds growth in the different orientation-preferred Cu substrates 47
Experimental procedure 47
Experimental results and discussions 49
Conclusion 52
4.2 The formation of Kirkendall voids in Cu-Sn interdiffusion system 58
4.3 Microstructure effect of the Cu substrate on the formation of Kirkendall voids 61
Discussion 61
Chapter 5 Summary 68
References 69
Appendix 72

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