異方向性導電膜應用於平面顯示器壓合條件的研究

Abstract

行動電話等通訊，視聽器材液晶顯示屏的解析度不斷的提高，目前較新之顯示屏幾乎皆以VGA ( video graphics array ) 級 ( 640 X 480 畫素 ) 為主流。液晶顯示屏因需要較高解析度和較佳的顏色飽和度，所以其結構需要較高數量的映像點和電器訊號接點，在接合技術方面也需要更精密之加工來構裝液晶顯示屏驅動晶片，而異方性導電膜 (ACF, Anisotropic Conductive Film) 之應用正是可以達到輕薄短小且高密度及高效能化的材料之ㄧ。 在壓合製程中，異方性導電膜是將驅動晶片固定於ITO（indium tin oxide）導電玻璃上之介面材料，籍由異方性導電膜中之導電粒子連接驅動晶片上的凸塊與玻璃基板上的ITO導電金屬層而達成電氣導通之目的。本研究即探討製程中ACF導電粒子的變形形態與施加壓力及壓合溫度與壓痕大小之間的關係。並以田口式參數設計規劃實驗，進行實驗分析以找出較佳的壓合條件參數組合。 實驗結果顯示，壓合溫度、壓力對壓合後ACF中之導電粒子之變形有極顯著之影響。我們發現，當接合壓力越大，導電顆粒子被壓的越扁，接觸面積越大，則接觸阻抗越低，甚至於造成導電粒子壓碎，導電粒子捕捉率愈小，造成生產良率降低，反之接合壓力太小會導致接觸面積不足，接觸阻抗太大，造成導電不良及顯示屏訊號畫像異常。

Resolution of the LCD (liquid crystal display) panels which are been used on the mobile phones and many other visual apparatus, is continuously improving. Currently, the LCD panels on the mobile phones use VGA (video graphics array), with a resolution of 640 X 480 pixel, as the main display. Demand for higher resolution and better color quality requires greater numbers of pixels and more inter connections between the electrical contacts, which in turn, requires more advanced skills in packaging the LCD with the drive ICs. The anisotropic conductive films have advantages like thin, light weight, higher conductive particles density and more effective than many other bonding materials are widely used in the packaging process. In the bonding process, the ACF contact the drive ICs with the ITO (indium tin oxide) conductive glass. Conductive particles embedded within the ACF become conductive when pressures were applied on the film. However, conductivities of the particles rely on the bonding temperature, and pressure. The main purpose of this study is investigating the relation between bonding temperature, pressure, bonding speed and particles deformation shapes after bonding. An experimental parameter combination was organized by Taguchi method and bonding experiments conducted according to this parameter combinations. Experiment results show that bonding pressure and temperature, temperature, have very significant effects on the conductivities, deformation shapes of the conductive particles in the ACF. Higher pressure usually causes the particles deform more flat which in turn increase the contact area of the particles with the bumps, thus reduce the contact resistivity. In extreme cases, the particles were completely crashed and made unfunctional. On the other hand, smaller pressure induces insufficient contact area which will greatly increase contact resistivity and cause abnormal display of the LCD panels.