EMI/RFI shielding materials

With the heavy volumes of data being transmitted these days over the RF spectrum, designers are required to spend a good deal of their time developing ways to mitigate the effects of EMI/RFI. Depending on the application, there may be several ways to achieve the desired result.

Many times, EMI/RFI shielding is accomplished at a system level, where an enclosure is used as a Faraday cage. Interconnects such as sockets and RF connectors are also enclosed, often enough, with a housing that acts as a Faraday device.

Interconnects and other high-frequency components such as inductors and capacitors typically will be built with materials that thwart interference. And, of course, cables feature jacketing and insulation to limit the undesirable effects of EMI/RFI.

Knowing how busy our readers are, I’ve compiled a variety of shielding-related products to help with the selection.

Materials

Tech-Etch (www.tech-etch.com) offers standard and custom board-level shielding manufactured using a photochemical etching process to provide design flexibility and reduce cost. A standard two-piece design features a spring-finger style attachment between fence and cover and can be customized to almost any possible configuration.

Standard and board-level shielding from Tech-Etch

Part of the company’s Flex-Tech product line, Leader Tech’s (www.leadertechinc.com) Slot-Lok circuit-board shielding design and manufacturing process uses standardized manufacturing methods to produce a new level of PCB shield design and production flexibility. The proprietary concept has also helped reduce standard industry design-to-delivery lead times from 8 weeks to only 2 weeks.

Slot-Lok shields are made from RoHS-compliant materials and feature an audible click to confirm retention of the CBS cover.

Leader Tech’s Slot-Lok circuit-board shielding design and manufacturing process

Featuring a flammability rating of UL 94 V-0, the Soft-Shield 4850 EMI multiplanar gasket from Chomerics (www.chomerics.com) is a conductive soft-foam-based gasket suiting consumer and commercial electronics, telecom, and IT applications such as backplanes, I/O panels, and access panel cabinet seals. The gasket provides low closure force for stable electrical performance, incorporates silver-plated fibers, and is fully RoHS compliant.

The LNP Faradex family of specialty compounds from Sabic Innovative Plastics (www.sabic-ip.com) improve EMI/RFI shielding performance compared to traditional metals, without increasing the loading of stainless steel fibers. Alloys of polycarbonate and acrylonitrile butadiene styrene, the compounds suit a variety of automotive applications as well as in housings for electronic devices and telecom applications.

The V Series variable finger-snap-on BeCu gaskets from Tech-Etch (www.tech-etch.com) provides an EMI/RFI shielding effectiveness of up to 100 db attenuation. Each gasket is offered in five different finger patterns and snap-on mounting provides fast, secure installation with high durability.

The V Series variable finger-snap-on BeCu gaskets from Tech-Etch

The Premier PEI-140 lightweight, electrically conductive plastic from Chomerics (www.chomerics.com) offers EMI shielding of high-temperature avionic applications. The material maintains provides up to 85 dB in aerospace applications, complies with avionics smoke density requirements in the event of an on-board fire.

The BMIS-226 and BMIS-208 frame and cover board-level shielding products provide off-the-shelf solutions for customers who do not need or want high volumes or the investment that comes with custom tooling.

The Polyvent/M12 protective vents from W.L. Gore (gore.com/protectivevents) offer a solution for equalizing pressure in telecommunications equipment exposed to severe weather conditions. Available in both plastic and metal, the vents allow air and gases to flow freely in and out of equipment housings.

The EMIgard Series conductively plated, optical fine wire mesh from Dontech (www.dontechinc.com) enables EMI/RFI shielding of electronic displays and enclosures. The products are manufactured in 304 stainless steel, copper, and custom alloys.

Meshes are available from 50 to 250 openings per inch in standard sheet sizes of 22 x 28 in. or in precut sizes.

Ralph Raiola