Abstract
Over the last decade there has been an increasing trend to replace metals with plastics in the areas of computers, business and industrial equipment, automotive and telecommunications. Economics is usualy the driving force due to the trend toward downsizing and more complex designs. A consequence of taking advantage of the full function design flexibility of plastics is increased susceptibility to EMI/RFI due to the inherent dielectric nature of the plastic itself.
To alleviate electromagnetic interference, it is necessary to utilize shielding techniques that protect the sensitive electronic devices from incoming interference generated by foreign sources, while also limiting the emittance of unwanted radiation produced by the device itself. In addition to typical design considerations, engineers must now also decide how best to address EMI shielding requirements. The ability to address both shielding and design requirements will, to a large degree, depend on the shielding technology chosen.
In selecting the correct shielding technology, several key issues must be considered: shielding effectiveness, coating uniformity (especially with applications involving complex designs) and resistance of the shielding media to environmental exposure. Many materials have been considered with mixed results. Electroless plating is now widely used as the coating of choice to address shielding requirements.
This paper will discuss the capabilities of selevtive and double-sided electroless multilayer coatings to address the issues involved in achieving control of EMI. Included is information on the shielding effectiveness of electroless coatings for near-field and far-field conditions and after temperature humidity cycling. The performance of electroless coatings will also be compared to alternate shielding techniques.
