EMI/RFI shielding materials and devices

With increased use of wireless in every environment, more companies are offering products that are creatively designed to aid in the battle against electromagnetic/radio-frequency interference. The following materials and devices are but a few examples of such recent products.

Materials

Diamondshield coating for soft substrates from Morgan Advanced Ceramics’ Diamonex division (Allentown, PA) not only provides an exceptionally hard (2-3 GPa) and transparent coating for, say, MP3 players or cell phones, but it can also be formulated to provide electrical insulation. With a very low index of refraction and virtually no absorption in the visible spectrum, the coating is easier to apply and less expensive than alternatives, and is also hydrophobic.

Laird Technologies (Delaware Water Gap, PA) is offering its T-BLS system, which costs about $0.40/in. 2 in 100,000-piece quantities, that not only provides board-level RF shielding but RoHS-compliant cooling of electronic devices as well. A single-assembly solution, it can reduce component and parts count, save space, and reduce costs.

Laird Technologies’ T-BLS shielding

The company also provides MaxAir vent panels that, unlike traditional metal units, use a RoHS-compliant nickel-copper-plated polycarbonate honeycomb material. The $0.25 to $0.80/in.2 panels provides EMI shielding while creating a rigid, frame-free vent that provides press-to-fit assembly and greater airflow.

MacAir vent panels from Laird Technologies

Connectors

Providing the required isolation and EMI suppression for 10/100/1000 Base-T applications, Compressor Series MagJack right-angle jack RJ-45 connectors from Bel Stewart Connector (Glen Rock, PA) features a two-tier, 19.94-mm compressed profile. At $1.75 to $2.25 per port, the connectors come in 6-, 8-, 12-, and 16-port versions, with options for up to two LEDs per port.

The $5 to $95 Series 700, 600, 500, 100, E and F EMI-filtered D-subminiature connectors from Spectrum Control (Fairview, PA) come in shell sizes of 9, 15, 25, 37, and 50. The units are available in RoHS-compliant versions and termination options include PC mount, wirewrap, solder cup, and 90° PCB.

Spectrum Control’s EMI-filtered D-subminiature connectors

Enclosures

With up to 100 dB of EMI/RFI shielding, the low-weight F-series cabinets from Optima EPS/Elma (Tucker, GA) come in sizes up to 44 U high and 19-, 24-, and 30-in. wide, as well as in three styles—non-gasketed, NEMA12/UL-508, and Shielded EMC/NEMA. Designed to handle dust, moisture, and EMC suppression, the less-than-$800 cabinets suits applications such as computer simulation, test and measurement, industrial control, and computer storage installations, and can be supplied with integrated cooling, cable management, and power distribution systems.

Teko Enclosures’ Tekam aluminum instrument cases

Designed to speed installation of electronics, Tekam instrument cases from Teko Enclosures (Bridgeville, PA) are made of aluminum to enhance RFI/EMI protection and come with molded-rubber gaskets for sealing the mating faces of the end panels and case extrusion. Priced starting at $21, the 2.75 x 2.36 x 1.22 in. to 6.89 x 4.17 x 1.81-in. units have a series of internal guide rails for mounting the PCBs and can be purchased with flat end panels for handheld or portable use, or end panels with integrated wall-mounting ears.

Components and ICs

With RDS(on) as low as 0.075 Ω and a FREDFET body diode recovery speed of less than 250 ns MOS 8 MOSFET and FREDFET devices from Microsemi (Irvine, CA) offer reduced EMI as well as improved oscillation immunity, lower peak slew rates, and high dv/dt ruggedness capability. The devices have a lower thermal resistance and higher current ratings for each die size and package type than previous devices The RoHS-compliant FETs were designed for high-power switchmode applications from battery chargers to arc welding and plasma cutting, are priced from $7.34 ea/1,000, and come in versions with current and voltage ratings of 19 to 75 A and 500 to 1200 V, respectively.

Microsemi’s MOS 8 MOSFET, FREDFET devices

With EMI levels of –110-dBm, the Fairchild Semiconductor (South Portland, ME) FIN324C µSerDes serializes and deserializes data going to/from sensors and displays in portable applications such as cell phones and MP3 players. Able to improve reliability and reduce wire count, parts count, and cost, the 1.6 to 3.0-V IC consumes 4 mA at 5.44 MHz, offers 15-kV ESD protection, supports dual displays, needs no external timing-reference devices, and costs $1.66 to $1.74 each in 1,000-piece quantities.

Offered in values from 1.2 to 330 µH, the 6.70 (W) x 5.60 (L) x 1 (H)-mm DR331-5 surface-mount inductor from Datatronic Distribution (Romoland, CA) protects against EMI. DCRs range from 0.08 to 15 W, and current ratings are from 0.13 to 2.1 A. Operating temperature range is from –40° to 85°C.

Fairchild Semiconductor’s FIN324C SerDes serializer/deserializer

Offered in ultra-compact leadless packages, the VEMI EMI filter arrays from Vishay Intertechnology (Malvern, PA) feature a 0.6-mm profile and 0.4-mm pitch. The four-channel VEMI45AA-HNH, six-channel VEMI65AA-HCI, and eight-channel VEMI85AA-HGK arrays attenuate signals by more than 30 dB in frequencies from 900 MHz to 2.3 GHz.

The FN 3025/3026 three-phase EMC filter from Schaffner EMC (Edison, NJ) features a plastic housing. The filters are equipped transparent hinged safety covers, low Y-capacitor filter circuitry, and electrical connections based on motor-drive technology. Rated from 20 to 50 A and continuous operating voltages of 3 x 520 Vac, the FN 3025 version suit traditional screw mounting. The FN 3026 mounts on TS 35 DIN-rails.

—Richard Comerford