I. INTRODUCTION ELECTROMAGNETIC shi

I. INTRODUCTION
ELECTROMAGNETIC shielding is becoming a critical requirement for components with plastic housing,due to the increasing
Restrictions on electromagnetic emissions, and the need for protection of electronic equipments from environmental
Electromagnetic interference (EMI).As known, plastic materials in their original state are completely trans-parent to radio-frequency
Signals .Conventional shielding .techniques use one or more conductive metal layers; typical practical solutions include conductive
Paints or zine arc spray on the interior housing surface. Such coated shieding tends to reduce their electromagnetic properties because
Of oxidation, abrasion, scratching, or loss of abhesion of the metallic film. A significant improvement over these techniques consist of
The use of conductive composite materrials with high EMI shielding characteristics.Such a materials can be obtained adding chemical
Additives , conductive carbon black ,conductive fibers,and nickel-coated graphite fibers to the pure resin. Such composite materials combine both the high electrical as well as thermal conductivity of the exceptionally high strength-to-weight ratio of fiber reinforcement