表面金屬化碳纖維複合薄膜之電磁波屏蔽影響研究

A Study on Electromagnetic Shielding Effectiveness of Surface Metallization Carbon Fiber Composite Films

張哲源(Che-Yuen Chang)

指導教授 ： 鄭大偉

國立臺北科技大學/工程學院/材料科學與工程研究所/碩士(2007年)

摘要

近年來，由於電子科技發展快速與日常生活品質之提升，電子、電機、資訊與通訊等電子資訊產品便應運而生，改善人們便利舒適之生活品質。但電子資訊產品所產生之高密度電磁波輻射，已形成一新的公害問題，不僅會對其它電子資訊產品造成電磁波輻射干擾(Electromagnetic Interference, EMI)，影響電子資訊產品正常之運作，亦會對人體造成危害。最直接且有效率之電磁波輻射干擾防治方式，是將電子資訊產品外殼進行電磁波屏蔽，阻隔本身散出或外界環境之電磁波輻射干擾。
隨著電子資訊產品皆朝向輕薄短小之設計理念發展，高分子材料具有優良之加工性，質輕美觀柔軟，耐腐蝕性佳，低成本且易設計成各種形狀等優點。將本質絕緣之高分子材料經過適當之改善，結合導電填充材料製成填充型導電性高分子複合材料，即可應用於電磁波屏蔽，並可大幅提升高分子材料之應用價值。
本研究是將研磨成適當長度之碳纖維，分別進行無電電鍍(Electroless Plating)銀與銅金屬，製備表面金屬化碳纖維，並以高分子混摻法(Polymer Blending)，與水性聚氨基甲酸酯(Waterborne Polyurethane, WPUR)製成具有電磁波屏蔽功能之水性PUR複合薄膜。
研究結果顯示，碳纖維之長度、填充量、無電電鍍金屬與含量，以及厚度皆會影響水性PUR複合薄膜之電磁波屏蔽效益。將研磨成平均長度約為124.3 μm之碳纖維，進行無電電鍍銅，製成銅含量約為23.1 vol.%之表面金屬化碳纖維，以15 vol.%之填充量，製成厚度約為0.2 mm的水性PUR複合薄膜。其複合薄膜之表面電阻約為1.46×100 Ω/cm2，頻率於900與1800 MHz，電磁波屏蔽效益皆約為30 dB，頻率於2450 MHz，電磁波屏蔽效益約為25 dB，其電磁波屏蔽效果最高可達99.9 %。厚度由0.2 mm堆疊增加至0.8 mm，頻率於900 MHz，電磁波屏蔽效益可提升至約為49 dB，頻率於1800 MHz，電磁波屏蔽效益可提升至約為45 dB，頻率於2450 MHz，電磁波屏蔽效益可提升至約為42 dB，其電磁波屏蔽效果最高可達99.99 %。

關鍵字

電磁波屏蔽 ； 導電性高分子複合材料 ； 碳纖維 ； 無電電鍍 ； 高分子混摻法 ； 水性聚氨基甲酸酯 ； 電磁波屏蔽效益

並列摘要

Due to the rapid development of the electronic technology, electronic, electrical, information, and communication products have greatly improved people’s daily lives. At the same time, however, high density electromagnetic radiation produced by those products has also emerged as a new type of pollution, which forms electromagnetic interference (EMI) that affects the normal operation of other electronic products and causes harmful effects to human body. The most effective and direct prevention of EMI is the formation of electromagnetic shielding on the housing of electronic products, which may isolate EMI emitted from themselves as well as from the surrounding.
In order to make electronic equipment lighter, polymers are currently used widely for their inherent advantages, such as light weight, good-looking appearance, flexility, chemical resistance, low cost, easy formation, etc. Although polymers are electrically insulated, their value may be highly increased by proper modifications. For example, they can fabricate into fill-type conductive polymer composites applicable to electromagnetic shielding.
In this work, carbon fibers are grinded to proper length and plated with silver and copper on their surface by electroless plating so as to make fiber surface metallization; in addition, polymer blending method is employed to produce electromagnetic shielding composite films from the mixture of waterborne polyurethane and the carbon fibers.
The result shows that the length of the carbon fibers, the amount of fillers, the type of electroless plating material, and the thickness of the composite films may affect the effectiveness of the electromagnetic shielding composite films of waterborne polyurethane. In our research, the surface resistivity of the composite films is 1.46×100 Ω/cm2 when the starting carbon fibers are grinded to an average length of 124.3 μm and treated by electroless cooper plating to make them surface metallization carbon fibers with a cooper content around 23.1 vol.% and filled to an amount of 15 vol.% to fabricate 0.2 mm waterborne polyurethane composite films. The electromagnetic shielding effectiveness (EMSE) thereof is about 30 dB when the frequencies were 900 and 1800 MHz. In contrast, when the frequency was 2450 MHz, the electromagnetic shielding effectiveness was 25 dB. The electromagnetic shielding effectiveness can reach to 99.9 %. When the thickness of the composite films increased to 0.8 mm, the corresponding electromagnetic shielding effectiveness can be increased to 49, 45 and 42 dB at 900,1800 and 2450MHz, respectively. In addition, the electromagnetic shielding effectiveness can be up to 99.99 %.

並列關鍵字

Electromagnetic Shielding ； Conductive Polymer Composite ； Carbon Fiber ； Electroless Plating ； Polymer Blending ； Waterborne Polyurethane ； Electromagnetic Shielding Effectiveness

參考文獻

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