Shielding effectiveness testing of conductive paints of copper powders filled alkyd resin

Electrically conductive paints can be made by adding electrically conductive fillers to typically insulating polymers. Resins with an electrical resistivity of 10(0)Omega cm can be used for electromagnetic interference shielding application. In this paper, a kind of conductive paints made of alkyd resin filled with copper powders was prepared, and its shielding effectiveness tested. The result showed that at the frequency less than 1 GHz the SE values are higher than 40dB, but at the frequency of 1 to 5GHz the SE values are approximately 30dB. The reason was theoretically analyzed. Effect of adding Ni powders on the conductivity and SE values was thereafter studied. The result showed that adding less than 10%(wt%) of Ni powders did not cause remarkable decrease of conductivity but did cause remarkable improvement of SE. The SE value of the paints containing 7% of Ni powders was more than 40 dB at the frequency from 50 MHz to 20 Hz.