聚二氧乙基噻吩�聚苯乙烯磺酸(PEDOT:PSS)之製備與其含無電鍍銀微粒之導電膠的導電度研究

Abstract

本實驗共分成三大部分：第一部分為製備聚二氧乙基噻吩：聚苯乙烯磺酸複合物(PEDOT:PSS)懸浮水溶液的研究；第二部分為製備導電粒子的研究；第三部份為製備導電膠的研究及對導電顆粒組成進行改良。最終希望維持良好導電度下，降低元素銀的填充率。 藉由TGA及導電度的分析，可得知氮氣充泡處理及透析袋過濾有助合成PEDOT:PSS產物之品質。SEM分析可看出DMSO可以改變PEDOT:PSS分子構型，提高導電度。最後藉由調高PEDOT:PSS重量比例至1:1.5及加入7.5wt% DMSO得到最好的導電度314.55 S/cm。 於製備導電粒子前，先以SEM及粒徑分析得知原始的石墨粉GS-75平均粒徑為2.379μm且構型是扁平雪片狀，皆是最適合做為導電粒子的條件。將導電顆粒分為經過敏、活化及未經過敏、活化鍍銀程序後，以SEM、XRD、EDX及ICP觀察得知經過敏、活化的樣品無論鍍銀量、銀的包覆情形皆較另外一組樣品好。再經粒徑分析後得到平均粒徑為3.028μm，仍在適合作為導電粒子的範圍中。 製備導電膠實驗方面，發現使用較高的硬化溫度以及低壓環境下使導電膠硬化，可得較良好的導電度；且經過敏、活化的鍍銀導電顆粒的確較未經過敏、活化的樣品佳。實驗中也發現，於低填充率時添加PEDOT:PSS能有效增高導電度；以40wt%填充率為例，當PEDOT:PSS與EPOXY重量比為3:4時的導電度為444.87 S/cm，此值已是未添加PEDOT:PSS樣品的二倍多。 最後添加奈米銀粒子企圖於銀披覆石墨顆粒中形成二級結構，發現未加入丁基硫醇作為分散劑時，奈米銀的添加只會造成導電度下降。以丁基硫醇作為分散劑修飾粒子表面後，發現奈米銀與銀披覆石墨顆粒重量比達2:8時可使導電度最佳化。實驗中以70wt%填充率(實際元素銀填充率為35.21wt%)、環氧樹脂與PEDOT:PSS重量比4:3、以丁基硫醇修飾過後的奈米銀與銀披覆石墨導電粒子重量比2:8時達到最佳導電度9.66 x 103 (S/cm)。

This thesis presents the study of the Electrically Conductive Adhesives (ECAs) which includes preparation and analysis, and is presented in three parts. First part presents the synthesis of Poly(3,4-ethylenedioxythiophene):Poly- (StyreneSulfonate) (PEDOT:PSS). The second part illustrates the preparation of Silver-plated graphite conductive particles. In the last part, these two conductive materials are combined into ECAs for optimizing the conductivity with less Silver filling ratio. TGA and conductivity measurements show that Nitrogen-bubbling and dialysis help the polymerization and purification of PEDOT:PSS, thus increasing the conductivity. Adding DMSO transforms the morphology of PEDOT:PSS, which have huge influence on conductivity. Increasing the weight ratio of PEDOT in PEDOT:PSS significantly enhances conductivity, but the solution will become less homogeneous. In this study, the highest conductivity of PEDOT:PSS film is 314.55 S/cm, which is reached as PEDOT:PSS weight ratio is 1:1.5 and with 7.5wt% DMSO. In the study of conductive particles’ preparation, SEM images, EDX and XRD analysis show that sample with sensitization and activation has more silver exposure. ICP analysis evidences that sensitization and activation effectively raises the weight ratio of silver adsorbed, up to 40.1wt%. Sample is further investigated by Particle Size Analyzer and SEM to ensure the suitable size and morphology for conductive particles in ECAs. In the study of ECAs, higher curing temperature and lower pressure guarantee better conductivity. Adding PEDOT:PSS does enhance the conductivity, but it is not so effective at high filling ratio. Silver nano-particles without butanethiol as dispersant will dramatically lower the conductivity. After surface modification with butanethiol, Silver nano-particle turns to be beneficial for conductivity at low weight ratio. The highest conductivity measured in this study is 9.66 x 103 (S/cm). It’s obtained when total filling ratio is 70 wt% in which 20 wt% of conductive particles are butanethiol-treated silver nano-particles.