塑膠鍍膜技術已被應用於電器產品外殼，以提供塑膠外殼電磁防護的效果。 本文根據傳輸線理論和平面波遮蔽效應理論，分析並驗證多層金屬薄膜於塑膠基板上的電磁防護效應。分析結果顯示由於金屬薄膜厚度不足，所提供的吸收效應有限，反射效應成為整體防護效應的主要來源。為得到較佳的反射效應需要使用高導電性的金屬材料，並且以多層薄膜的設計來提升反射效應，進而增加整體防護效果。對於多層金屬薄膜而言，當相鄰兩層金屬的排列為靠近基板的金屬層較遠離基板的金屬層有較高的導電率/導磁率比時，此兩金屬層間的界面可提供正的反射效應；另當使用高導電率材料為接觸空氣的最外層金屬薄膜時，則可以提高金屬與空氣界面的反射效應。所有的分析結果都經由實驗得到驗證。需要特別注意的是，實驗中金屬薄膜是由真空蒸鍍法製作，製作過程中因諸多因素造成金屬薄膜有些微小缺陷，而這些缺陷使得金屬薄膜的導電性改變，影響了電磁防護的效果。

　　Conductive coatings are applied to plastic substrates to provide protection of electronic equipment against electromagnetic interference. A model of electromagnetic shielding effectiveness of multilayer metallic thin films on plastic substrates is developed based an transmission line and plane wave theory. Analyses show that with limited film thickness, the shielding effectiveness provided by absorption loss is negligible while the reflection loss becomes dominant. Shielding effectiveness of a metallic thin film shield is mainly by the reflection and thin film with high conductivity is thus desirable. For multilayer metallic thin films, the positive shielding effectiveness is achieved by placing thin film with higher conductivity/permeability ratio closer to the substrates. Analyses show that multilayer thin film shielding effectiveness is also increased mainly by the reflection performance, and using the conductive material as the final (top) layer leads to better shielding effectiveness. All analytical results are validated by experiments. It should be noted that metallic thin films are fabricated in an electron vapor deposition system. The defects of the thin film during fabrication process leads to the change of electrical properties thus affecting the shielding effectiveness.

References
ASTM, “Standard Test Methods for Measuring Adhesion by Tape Test,” ASTM D3359-02, 2002.
ASTM, “Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials,” ASTM D4935-99, 1999.
Bhatgadde, L. G. and Joseph, S., “Electroless Techniques for EMI Shielding,” Proceedings of the International Conference on Electromagnetic Interference and Compatibility, pp. 443-445, Dec 1997.
Brown, B. E., Hill, J. T., and Archibald, L. D., “ RFI/EMI Shielding of Plastics Enclosures,” International Conference on Electromagnetic Compatibility, pp. 285-289, Sep 1992.
Dai, S. G., Li, P. L., Jou, W. S., Wu, T. L. and Cheng, W. H., “Effect of Carbon-fiber Orientation on the EM Shielding for the Plastic Laser Module Packages,” Proceedings of Electronic Components and Technology Conference, pp. 1675-1679, May 2002.
De Bruyn, K., Van Stappen, M., De Deurwaerder, H., Rouxhet, L., and Celis, J. P., “ Study of Pretreatment Methods for Vacuum Metallization of Plastics,” Surface and Coating Technology, vol. 163-164, pp. 710-715, Jan 2003.
Guan, D., Huang, W., Chen, J. and Tu, M., “Study on the Magnetic Shielding Composite Coating in Low Frequency,” International Symposium on Electromagnetic Compatibility, pp.586-588, May 2002.
Joo, J. and Lee, C. Y., “High Frequency Electromagnetic Interference Shielding
Response of Mixtures and Mutilayer Films Based on Conducting Polymers,” Journal of Applied Physics, vol. 88, no. 1, pp.513-518, Jul 2000.
Kodali, V. P., Engineering Electromagnetic Compatibility: Principles, Measurements, and Technologies, IEEE Press, pp. 1-8, pp. 204-213, 1996.
Kraus, J. D. and Fleisch, D. A. and Russ, S. H., Electromagnetics with Applications, McGraw-Hill, pp. 169-239, 1999.
Morris, K., “ Much Ado about Mobile Phones,” The Lancet Oncology, vol. 2, no. 3, p. 124, Mar 2001.
Paul, C. R., Introduction to Electromagnetic Compatibility, Wiley, pp. 1-2, pp. 633-665, 1992.
Rahman, H., Saha, P. K., Dowling, J. and Curran, T., “ Shielding Effectiveness Measurement Techniques for Various Materials Used for EMI Shielding,” IEEE Colloquium on Screening of Connectors, Cables and Enclosures, pp. 9/1-9/6, Jan 1992.
Rowberry, P., “Investigation into the Electromagnetic Shielding of Plastics and Composites for High Volume Applications,” IEEE Colloquium on Screening of Connectors, Cables and Enclosures, pp. 5/1-5/5, Jan 1992.
Schelknuoff, S. A., Electromagnetic Waves, D. Van Nostrand Company, Inc., 1943.
Schulz, R. S., Plantz, V. C., and Brush, D. R., “Shielding Theory and Practice,” IEEE Transactions on Electromagnetic Compatibility, vol. 30, no. 3, pp. 187-201, Aug 1988.
Trenkler, Y. and McBride, L. E., “ Shielding Improvement by Mutilayer Design,” IEEE International Symposium on Electromagnetic Compatibility, pp. 1-4, Aug 1990.
White, D. R. J., A Handbook On Electromagnetic Shielding Materials and Performance, Interference Control Technologies, Inc., pp.1.1-1.40, pp. 2.1-2.10,1980.