Microwave assisted synthesis of Ni nanoparticles for patternable conductive pastes
|關鍵字:||導電膠;鎳奈米粒子;燒結;conductive paste;Ni nanoparticles;sintering|
|摘要:||相較於傳統上使用光學微影技術的薄膜製程，因其良好的電性以及容易操作使用等特性，導電膠已被廣泛應用在用於製作印刷電路板上的導體電路以及網版印刷太陽能電池的上下電極中。而銀這種金屬則最常被使用來做為導電膠內部的導電填料因為它出色的導電率以及良好的化學穩定性，然而，在高溫製程中發生的離子遷移現象以及材料本身的高成本等因素，使得我們必須去尋找另一個合適的低價位的替代材料。在各種不同的研究以及實際應用上所使用的過的金屬材料中，像是金、鉑、銅和鎳等金屬，鎳是一個非常具有潛力的替代性材料，因為其具備了比銀更低的價位還有優於銅的化學穩定性。也因此有非常多的研究使用了像是聲化學沉積、微乳膠法、多元醇法以及水熱法等合成方法來製備分散性佳適合用來做噴墨塗佈的鎳奈米粒子。在我們的研究當中，我們選擇使用有機金屬熱分解法來製備鎳奈米粒子，而其透過了微波輔助加熱來分解油胺與甲酸鎳的複合物，並藉此來合成得到單一分散性的鎳米粒子。這些收集到的奈米粒子經過乾燥處理後與環氧樹脂等有機黏結劑混合製作成導電膠，並且依不同固含量條配出不同黏度和電性的成品並直接以圖案化的方式塗佈到矽基板，之後進行退火熱處理來去除多餘的有機雜質和提供一個合適的燒結環境來降低電阻值，藉由使用這些相對低溫且低成本的製程最後我們得到了一個擁有1 mm最小線寬而其導電率約等於10-2 "Ω∙cm" 的導電細線。|
Conductive pastes have been widely used for the formation of thick film conductors such as conductive features in printed circuit boards and electrical contacts in silicon solar cells by screen-printing process owing to its good electrical properties and more accessible process compared to traditional thin ﬁlms processes accompanied by photolithography. Silver is probably the most common fillers due to its excellent electrical properties and chemical durability. However, as a result of problems such as ion migration at high temperature as well as high cost than other kinds of materials, it is essential to find another substitute for silver. Among various materials studied and used as conductive fillers including gold, palladium, nickel and copper, nickel have been considered as a potential alternative because of its low cost than silver and high chemical stability compared to copper. Therefore, several techniques such as sonochemical deposition, microemulsion synthesis, polyol methods, and hydrothermal reactions, have been developed to produce nano-scale nickel particles, which are companied with good dispersibility and therefore be favorable for the printing process. In this study, we selected thermal decomposition of organometallic compounds for the preparation of Ni nanoparticles. Monodisperse Ni nanoparticles were synthesized by the pyrolysis of Ni formate complex with oleylamine under microwave irradiation. These synthesized nanoparticles were collected and mixed with epoxy resins and other organic binders to fabricate conductive fluids as pastes with various solid contents, patterning them onto substrates by direct printing. Annealing process will be conducted to provide a sintering condition in order to reduce electrical resistance. After this high-temperature process, we successfully obtained conductive features with the line width of 1 mm and resistivity of about 10-2 Ω∙cm through a relatively low temperature and low cost process.