건·습식 융합프로세스를 이용한 전자파 차폐 코팅막의 제작과 특성 평가

Abstract

A lot of electronic machineries used in electronics, telecommunications and computer field are driving our present society into information oriented hi-tech society generating electromagnetic waves. These waves are harmful to human bodies and may cause other electronic devices to be affected. Therefore, studies and researches for electromagnetic wave shielding have been performed and the needs for electromagnetic wave shielding materials are rapidly increasing steadily.

Almost all the materials used for electromagnetic shielding are metals such as aluminium, nickel and copper. Because of hardness and weight, these materials are hard to be applied to hi-tech environment where smaller and lighter materials are preferred. From this point of view, electromagnetic wave shielding fibers using wet process are being replaced quickly in these applications. However, we can also expect limits of fibers like metal-case as hi-tech environment is getting more and more advanced and complicated. Finally, the needs for plating skills on plastic films were raised naturally.

In this study, Cu thin films for electromagnetic wave shielding were prepared on PET film and Ni-coated PET film by using Dry and Wet coating method, such as evaporation method, DC sputtering method and copper sulfate(CuSO4). After that, Zn thin film and Ni thin film were prepared onto the Cu thin films by using evaporation dry process and Ni electro plating wet process as a finishing treatment, respectively. Morphology and composition rate of every film were investigated by scanning electron microscopy(SEM) and energy dispersive X-ray spectrometer(EDX), respectively. In addition, their conductivity and corrosion resistance were evaluated by surface impedance test and natural potential test.

SEM and EDX results of Cu thin films showed grain size get bigger and Cu composition rate increase as gas pressure of vacuum chamber become Lower. The result of conductivity test and corrosion resistance test revealed Cu thin films which were formed with bigger grain size and high Cu composition rate have superior properties.

Zn thin film by dry evaporation process and Ni thin film by wet electro plating process on Cu thin films were largely contributed to corrosion resistance. However, Ni thin film by wet process made conductivity of all specimen worse, the other hand, Zn thin film by dry process made it better to improve condictivity of specimens just prepared by dry process.

Consequently, Cu thin film prepared by CuSO4 wet process still showed better performance than the others in all properties such as conductivity, corrosion resistance. Nevertheless, Cu thin films prepared by dry process like evaporation and sputtering method can be acceptable for commercial standard of electromagnetic wave shielding and have improvement potential.