熱塑性複合材料電磁波屏蔽效益之研究

A Study of Electromagnetic Shielding Effectiveness of thermoplastic Composites

張博豪(Bo-Hao 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，隨著電子產品大眾化、精密化的發展趨勢，並且3C電子產品使用率之提升，人體接觸電磁波的機會也愈來愈多，使得外來電磁波的干擾亦形成一種新的污染公害。有鑑於此，為了有效降低電磁波干擾及影響，選用質輕的金屬材料或導電性高分子複合材料，是目前屏蔽電磁波之重要發展方向。而導電高分子材料因加工自由度高、質輕等優點而廣泛應用於電磁波遮蔽材料。
導電高分子填充材料多使用碳纖維、碳黑及金屬粉末，其中碳纖維具有高導電性、低密度及複合材料之補強特性，故本研究碳纖維作為填充材料，將碳纖維經過無電電鍍處理，使其表面分別披覆金屬鎳及銅，增加碳纖維之導電度，混摻於聚丙烯(PP)高分子基材中，製成具有電磁波屏蔽功能之高分子複合材料，研究不同高分子成型方式與金屬鍍層對於碳纖維電學性質及複合材料電磁波屏蔽效益之影響。
根據實驗結果顯示，以熱壓成型的方式製作高分子複合材料可獲得較佳的電磁波遮蔽效果，以碳纖維10 vol.%添加量製作之碳纖維複合材料，相對於射出成型的方式，平均遮蔽效果由27dB提升至54dB。而當碳纖維表面披覆不同金屬鍍層時，可有效降低碳纖維之電阻係數，進而提升複合材料之電磁波遮蔽效果，分別在4 vol.%添加量下，經過無電電鍍銅與鎳處理之碳纖維製成之複合材料，其電磁波遮蔽效果分別由22dB提升至43dB與40dB。

關鍵字

碳纖維 ； 聚丙烯 ； 複合材料 ； 電磁波屏蔽 ； 無電電鍍 ； 熱壓成型

並列摘要

In recent years, since the polymer embraces a great number of superb characteristics, such as light weight, design flexibility, low costs, mass production capability, and etc, it is widely applied in 3C electronic product. However, using plastic housings has a serious problem with electromagnetic interference(EMI). It could cause noise signals and even malfunction of the electronic appliances due to their poor electrical conductivity. But it can be easily converted to highly conductive material by adding electric conductivity particles to damp the EMI pollution.

Among the various conductive fillers, carbon fibers have been proved to be a good candidate for EMI shielding. However, the electrical resistivity of a carbon fiber is much higher than the metal filler, so it must to use a greater number of carbon fibers in order to achieve the same shielding effect. In recent years, the Electroless plating is the new techniques of surface treatment of carbon fibers used to improve the electrical conductivity of carbon fiber. The copper-coated and nickel-coated carbon fibers have been proved to be a good candidate for EMI shielding.
The result showed that the shielding effectiveness(SE) of carbon fiber filled polypropylene composites was found to be higher SE than the others fillers under the same volume percentage. In addition, high electromagnetic shielding was obtained for the composite with carbon fibers at the longer length. The average of SE of composites containing 10 vol.% carbon fiber was measured to be 53 dB at frequency of 900 MHz 、1800 MHz and 2450 MHz. The copper-coated and nickel-coated carbon fibers could improve the SE of composites form 22 dB to 40 dB and 43 dB at 4 vol. %.

並列關鍵字

Carbon fiber ； polypropylene ； Electroless plating ； Electromagnetic Shielding Effect

參考文獻

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