金銦、銀銦、銅銦錫之界面反應及相平衡

Abstract

低溫銲料的使用在工業界日益受到重視。其降低製程溫度的所帶來的優勢包括，減少電力加溫產生的碳排放、減輕PCB載板翹曲引發的失效，降低對熱敏感元件的損傷等，並且可以用於step soldering的後半段製程。鑒於銦及錫銦合金的低熔點及延展性，以及銅、銀、金為常用的端點連接金屬及表面處理鍍層，本研究探討了金銦固態擴散偶的界面化合物生長行為，以及銅銦錫三元系統暨銀銦二元系統之相平衡，為焊接的冶金學提供基礎科學資料。 研究方法包括試片製備恆溫熱處理的合金及擴散偶，並使用SEM、EPMA、EBSD、XRD、DSC、TEM等工具進行微結構的觀察及實驗相圖的測定。 在金銦固態界面反應的部分，本人將金銦擴散偶置於攝氏125及150度持溫後，分析接合處微結構隨時間的演變。除了展現組構及描述生長動力曲線，本研究確認金銦擴散偶會產生雙相共存區，乃非典型的二元擴散偶會產生的微結構。 在銅銦錫相平衡的部分，本實驗建立了攝氏一百度及一百四十度的等溫截面，並分析各相的晶體結構。其中Cu(In,Sn)2擁有相當程度的Sn固溶度，直至銅與共晶銦錫之界面反應經常觀測到的組成比為2Cu3In1Sn的介金屬，且前人所報導的Cu2In-Cu6Sn5連續單相區實際上被至少一個tie triangle所分割，並不連續。 在銀銦相平衡的部分，本實驗修正了相邊界及各invariant reaction的數值，釐清不同版本的銀銦相圖之爭議部分，如γ-ζ之不對稱相邊界等。此外，富銦之ζ (hcp)相存放在室溫數十天後即可觀察到部分區域相變成室溫平衡二相共存的組織。

The use of low-temperature solder materials has garnered increasing attention in the industry. The advantages of reducing process temperatures include minimizing the carbon emission associated with electric heating, alleviating failure caused by warping of printed circuit boards (PCBs), reducing damage to heat-sensitive components, and facilitating step soldering in later stages of the process. Given the low melting point and ductility of indium and indium-tin alloys, along with the widespread use of copper, silver, and gold as connecting metals and surface treatment coatings, this study investigates the growth behavior of intermetallic compounds at the gold-indium solid-state diffusion couple interface, as well as the phase equilibria of the copper-indium-tin ternary system and the silver-indium binary system. These findings aim to provide fundamental metallurgical knowledge for soldering applications. The research methods include preparing alloy samples and diffusion couples for isothermal heat treatment, followed by microstructural analysis and phase diagram determination using SEM, EPMA, EBSD, XRD, DSC, and TEM techniques. For the gold-indium solid-state interface reaction, gold-indium diffusion couples were placed at temperatures of 125°C and 150°C, and the microstructural evolution at the joint was analyzed over time. In addition to characterizing the texture and describing growth kinetics, the study confirms the formation of a two-phase coexistence region in the gold-indium diffusion couple, an atypical microstructure for a binary diffusion couple. For the copper-indium-tin phase equilibria, isothermal sections at 100°C and 140°C were constructed, and the crystal structure of each phase was analyzed. The Cu(In,Sn)₂ phase exhibited significant Sn solubility, leading to the frequent observation of the intermetallic with the composition ratio of 2Cu3In1Sn at the interface between copper and the eutectic indium-tin alloy. Moreover, the previously reported continuous single-phase region between Cu₂In and Cu₆Sn₅ is, in fact, interrupted by at least one tie triangle, forming separate single-phase fields. For the silver-indium phase equilibria, phase boundaries and the invariant values of several invariant reactions were revised, clarifying contentious features of previous silver-indium phase diagrams, such as the asymmetric phase boundary between the γ and ζ phases. Additionally, after several weeks of storage at room temperature, a partial phase transformation was observed in the indium-rich ζ (hcp) phase, resulting in a microstructure containing the corresponding room-temperature equilibrium two-phase coexistence.