Electronic module rfi/emi shielding

Abstract

A system, i.e. method and materials for RFI/EMI shielding an electronic module in a computer or other electronic product is described. In one embodiment of the invention predetermined areas of the module, such as connectors, mounting holes, and electrically insulated portions of the cases of high heat-dissipation electronic devices of the module, are masked. Thereafter, a relatively tichk, substantially continuous, electrically insulating conformal coating, in liquid state, is applied to all exposed surfaces of the module by a suitable technique, such as dipping or spraying. The preferred coating is a polymer-resin coating of a predetermined high viscosity and may be applied unfilled or filled with an electrically-insulating, thermally-conductive solid, such as powdered metal oxide, e.g. aluminum oxide. The applied conformal coating is set or cured, and a substantially continuous electrically conductive coating is applied over the insulating coating by a suitable technique, such as spraying or plating. The conductive coating has an electrical resistivity adequate for the required level of suppression of the RFI/EMI emissions from the module. Finally, the masking is removed from the masked areas of the module. In another embodiment of the invention, the electrically insulating coating is applied as a film which is vacuum formed in place, or the film may be pre-formed to conform with the module being shielded. The electrically conductive coating is then applied as above described.