Pastes for electromagnetic interference shielding

A paste has been developed for electromagnetic interference shielding by mixing stainless steel fibers (8-μm diameter) and graphite flakes (5 μm) in a water-based graphite colloid (containing submicron graphite flakes and a binder) in a volume ratio 0.5:20:100. The resulting coating of thickness 0.1–0.2 mm after drying exhibits shielding effectiveness of 34 dB at 1 GHz, primarily due to reflection. The paste is superior to those containing graphite flakes or carbon filaments (0.1-μm diameter), due to the higher shielding effectiveness of the steel fibers. The graphite flakes in the paste serves to help suspend the steel fibers, in addition to contributing to shielding.