聚二氧乙基噻吩/聚苯乙烯磺酸與石墨鍍銀複合導電膠製備及其導電特性之研究

Abstract

本實驗共分成三個部分討論 : 第一部分為製備導電粒子的研究 ; 第二部分為製備聚二氧乙基噻吩 : 聚苯乙烯磺酸複合物(PEDOT:PSS)懸浮液的研究 ; 第三部分為製備導電膠的研究。希望降低銀比例的同時，也維持著良好的導電度。 在粒徑分析後，可得知本實驗所合成出銀披覆石墨皆在1~2 μm左右，並從SEM圖像觀察，粒子形狀皆為扁平雪片狀，均為適合填充於導電膠中的條件。經過敏化活化程序的導電粒子，銀鍍層較為緻密 ; 使用銀鍍液中銀離子進行自身活化的方法經過EDX、XRD與ICP分析後證實可以完全取代價格昂貴的氯化鈀。在石墨中添加少量石墨烯進行無電鍍反應會使得鍍層較為鬆散，只能使用石墨烯直接進行鍍銀反應。 合成PEDOT:PSS薄膜時，在懸浮液中添加極性溶劑可以改變膜的形態，並提高導電度，其中又以DMSO效果較佳。最後得到最好導電度值321.5 S/cm，其條件為PEDOT:PSS重量比1 : 1及含7.5 wt%的DMSO。 製備導電膠實驗方面，在高溫低壓的環境下使其硬化，會有較低的電阻係數。經過敏化活化的銀披覆石墨的確較未敏化活化的樣品好，且自身活化方法的樣品可以完全取代氯化鈀。使用烷基硫醇作為導電粒子的分散劑，發現四碳鏈的丁硫醇有最好的效果。在低填充率的狀況下添加PEDOT:PSS能有效降低電阻係數。最後在導電膠中添加少量銀披覆石墨烯粉末，發現未加入丁硫醇作為分散劑時，添加銀披覆石墨烯只會造成電阻係數提高 ; 在丁硫醇修飾表面後，發現銀披覆石墨烯占導電粒子15wt%時可得到最低的電阻係數。本實驗最佳的兩個結果分別為1.02x10-4 ohm-cm(Ag 44.43 wt%) 與1.55x10-4 ohm-cm(Ag 38.87 wt%)。

The thesis was divided into three parts. The first part presented the preparation of conducting particles. The second part illustrated the synthesis of poly(3,4-ethylenedioxythiolphene):poly(styrenesulfonate) (PEDOT:PSS). In the last part, we combined these two conductive materials into ECAs for optimizing the resistivity with less silver weight percentage. Conductive particles were investigated by Particle Size Analyzer and SEM to ensure the suitable size and flake morphology in ECAs. We also showed the samples with sensitization and activation process had less graphite exposure, and confirmed self-activation method could replace Pd-activation method in eletroless plating process by EDX, XRD and ICP analysis. In addition, the performance of silver eletroless plating on graphene surface was better than it on graphite/graphene composite particles. Conductivity measurements showed that using nitrogen-pretreatment water and dialysis would help the polymerization and purification of PEDOT:PSS, thus increasing the conductivity. Adding organic solvent would transform the morphology of PEDOT:PSS film, which had huge influence on conductivity. In this study, the best conductivity of PEDOT:PSS film was 321.5 S/cm, which reached as PEDOT:PSS weight ratio was 1:1 and with 7.5 wt% DMSO. In the study of preparing electrically conductive adhesives, higher curing temperature and lower pressure got lower resistivity. Adding alkyl-thiol as dispersant would decrease the resistivity, and the best of them was butanethiol. In addition, adding PEDOT:PSS also did decrease the resistivity, but it was not so effective at high filling ratio. Silver plated graphene particles without butanethiol as dispersant would dramatically enhance the resistivity. After surface modification with butanethiol, silver plated graphene particles turned to be beneficial for decreasing resistivity. In this thesis, the better resistivity of ECAs were 1.02x10-4 ohm-cm(Ag 44.43 wt%) and 1.55x10-4 ohm-cm(Ag 38.87 wt%).