EMI Shielding Selection: Coatings, Films, Gaskets and Seams

Shielding effectiveness

Shielding reduces the coupling of electromagnetic energy into or out of an enclosure. Its performance is expressed as shielding effectiveness in dB over a frequency range; more dB means more attenuation. The first step is to define how much attenuation you need and over which frequencies, because that drives the choice of material and construction.

Coatings, films, gaskets and absorbers

Conductive coatings and paints turn a plastic enclosure into a conductive shell and are a common retrofit for shielding. Shielding films and foils provide continuous conductive layers on panels and windows. Gaskets and conductive elastomers seal the joints and doors where enclosures open. Absorber materials complement shielding by damping internal reflections and resonances rather than reflecting energy back.

No single material does everything: a continuous conductive shell handles the broad shielding, while gaskets and absorbers deal with the openings and internal behavior.

Apertures, seams and the weakest link

Real enclosures leak at their openings, not their walls. Seams, doors, cable penetrations, displays and ventilation apertures usually set the achievable shielding, so they deserve the most attention. A well-shielded panel with an untreated seam performs like the seam, not the panel — treat the whole enclosure as a system and address the weakest points first.

What to specify

Define the target attenuation and frequency range, the enclosure material and geometry, the openings that must be preserved, environmental needs (temperature, corrosion, outdoor use) and whether grounding is available. With that, a supplier can recommend coatings, gaskets and absorbers that work together.

Frequently asked questions

Coating or gasket — which do I need?

Usually both. A conductive coating forms the shielded shell; gaskets seal the joints and openings. Coatings cannot seal moving seams, and gaskets cannot shield large panels — they solve different parts of the problem.

How many dB of shielding is enough?

It depends on how much interference you must keep in or out and any compliance target. Define the required attenuation over frequency and the supplier can match materials and construction to it.

Why do apertures matter so much?

Openings and seams are the main leakage paths. An enclosure is only as good as its weakest opening, so treat seams, doors, vents and cable entries as carefully as the walls.

Where do absorbers fit into shielding?

Absorbers complement shields by damping internal reflections and resonances instead of reflecting energy back, improving the enclosure's internal electromagnetic behavior.