Conductive polymeric materials for electromagnetic interference (EMI) shielding

EMI/RFI encompasses all frequencies in the electromagnetic spectrum. The proliferation of electronic devices has resulted in a pressing demand for lighter, cheaper and more reliable materials which can prevent EMI emissions from an electronic device and protect that device from outside sources of EMI. Traditionally, conductor-filled plastics have been used for EMI shielding. Although these materials offer good shielding effectiveness, there still exist some drawbacks such as heavy weight, corrosion of metal fillers and non-homogenous dispersion of the fillers inside the polymer matrix. For reducing the electromagnetic emission from printed circuit boards, a conformal coating with lossy dielectric properties are required.; Light weight metal fiber composite coating is prepared by impregnating highly dispersed short metal fibers into a UV curable polymer matrix. Efficient electrical contacts between the thin fibers result in fiber network with high electrical conductivity. This metal fiber composite coating offers satisfactory EMI shielding effectiveness over a frequency of 45 MHz to 1.4 GHz.; Conductive polyaniline coated foam materials, also light weight are prepared through an easy, low cost process. These materials offer significant microwave absorbing effectiveness at a wide frequency range from 4 to 18 GHz.; UV curable conformal coating with relative permittivity of 7.0 and loss tangent of 0.39 has been development to reduce the crosstalk over printed circuit boards. The coating can reduce 80% crosstalk effect on microstrip line test coupon without affecting the transmission signals.