使用銦作為低溫銲接材料之研究

Abstract

隨著物聯網(IoT)的快速發展，由於低溫接合技術可以避免物聯網系統中的感測器、執行器及光電元件等熱敏感元件在接合過程中因為高溫環境而導致失效，多年来一直被產業界及學術界廣泛研究。而在眾多低溫接合技術中，固液擴散(SLID)接合是目前最可靠的接合技術，但值得注意的是，固液擴散製程的製程溫度還是受到所採用的銲料合金的熔點所限制，目前廣泛使用的高錫無鉛合金銲料的熔點對於上述的熱敏材料而言依舊過高，因此開發具有低熔點的新型合金銲料是目前產業界非常關注的議題。在本研究中鑑於銦的熔點僅156.76 ℃，因此我們選擇銦做為我們研究下一代低溫銲料的對象，並選擇常用的銅和鎳作為基板材料。 本研究包含了純銦與基板材料在180 ℃下的固液反應以及100 ℃、120 ℃和140 ℃下的固固反應。為了解決研磨和拋光過程中碳化矽和鑽石磨料容易嵌入於較軟的銦中的問題，我們另外使用氬離子拋光對試片進行處理。拋光後的試片我們透過具有背向散射電子偵測器的掃描式電子顯微鏡對介面的形態和微結構變化進行分析，並同時使用能量色散X射線分析化合物的組成，及使用高功率X光繞射儀鑑定在介面處所形成的介金屬化合物的晶體結構。研究的最後，我們根據上述介面反應的實驗成果，開發了一個最高溫僅160 ℃的低溫接合技術。

With the rapid growth in the internet of things (IoT), low-temperature bonding has been investigated intensively over years because it can prevent the risk of bond failure induced by the heat localization at sensors, actuators, and optoelectronic devices embedded in IoT systems. Among numerous low-temperature bonding strategies, solid-liquid interdiffusion (SLID) bonding is the most reliable bonding technique at present. However, it should be noted that there is a limit to how low the reflow temperature can go, which is the melting point of the solder alloy employed. To that end, since the melting points of the widely used high-Sn Pb-free alloys are high for heat-sensitive materials, development of new solder alloys with low melting points is essentially needed. In this research, Indium was chosen as the next-generation low temperature solder materials due to its melting point of 156.76℃. Commonly used Cu and Ni was chosen as the substrate materials. Solid-liquid reaction at 180 ℃ and solid-solid reactions at 100 ℃, 120 ℃, and 140 ℃ between In and substrates were carried in this research. To address the problem of the embedment of the SiC and diamond abrasives in the soft indium phase during grinding and polishing, additional argon ion milling polishing was used for final polishing to obtain artifact-free cross-sectional samples. Afterwards, the morphology of the interfacial layers and the microstructure evolution of the intermetallics at the interface were examined by scanning electron microscope equipped with a backscattered electron detector. Energy dispersive X-ray spectroscopy was utilized for the compositional analysis. A high-power X-ray diffractometer with a Cu-Kα source was used to identify the crystallographic structure of the intermetallics formed at the interface. Based the aforementioned results, a 160 ℃ low-temperature bonding method was developed for fine pitch chip-stacking application by SLID bonding technology at the end of this research.