Electromagnetic interference shielding, or EMI shielding, is the process of reducing the electromagnetic field in a space through the use of barriers or covers made of conductive or magnetic materials. The usage of EMI shielding is well established in computers, automotive electronics, medical devices, telecommunications, and is now expanding in the appliances market. Electronic devices are getting smaller and smaller. Hence, the challenge is to design smaller enclosures with dense circuits that perform at higher speeds.
By Belal Khan
EMI shielding products
Listed below are a few of the commonly used EMI shielding products and their key features:
Electrically conductive foil and fabric tapes: This is a thin material with electrically conductive adhesive on one or both sides. It is easy to cut and bond.
Electrically conductive adhesive transfer tape: Provides bonding and electrical conductivity in the Z axis or XYZ axes. These come in a variety of thickness options and adhesive properties; the tape is also easy to die-cut.
Electrically conductive foam gaskets: These are very soft, highly compressible, thin, conductive foam with adhesive on one side. They are good for designs that need to be taken apart for servicing.
Electrically conductive gaskets: These are less compressible than foam, and are available in a thin format with single- or double-sided adhesive. They are good for designs that need to be taken apart for servicing.
EMI absorbers: These offer flexibility to designers as shielding is possible without grounding. Absorbers are effective in controlling the specific frequency band that is causing interference.
Multi-function products: These are products that can be used for both shielding and absorbing, yet are very thin and easy-to-install due to adhesive backing.
Flux field directional materials: These multi-layer construction materials consist of a primary, inner soft magnetic foil layer with a protective PET cover film and an acrylic pressure-sensitive adhesive. These are suitable for RFID, NFC and wireless power applications.
Silicon heat transfer compounds: These are designed for transferring heat away from electrical and electronic devices such as transistors, power diodes, semiconductors, ballasts and thermocouple wells. They have high thermal conductivity, a high dielectric constant and a high dissipation factor. When used with heat sinks or metal, they do not dry or harden. They contain zinc oxide and polydimethyl siloxane.
Thermal grease: This has a low thermal resistance and is non-corrosive. It uses a synthetic oil base that is thermally stable as well as electrically insulating. It is used to improve the thermal interface contact conductivity between heat sinks, LEDs, motors and heat-generating electronic components such as central processing units (CPUs), graphics processing units (GPUs) chipsets, power components and so on.
A thermally conductive epoxy resin: This is formulated with undiluted Bisphenol F epoxy resin for superior physical properties and pigmented with high purity aluminium oxide to provide excellent thermal conductivity at a reasonable cost. It is pigmented black for better thermal absorption and emission.
Applications
- Communications and telecommunications
- Computers and data processing
- Aviation and aerospace
- Defence
- Medical and health
- Automotive
- Office equipment
- Electronics
- Instrumentation and control systems
- Home electronics, audio and video equipment
- Appliances
- Radios, TVs, cables and recording devices
Products available in the market
SunKyoung S.T Co. Ltd
The company offers EMI elastomers, which are made of metal particles in silicone, with a great technique for compounding and controlling shapes. The products have high conductivity as well as good shielding and sealing effects. They are used in telecommunications, IT as well as in medical, industrial, electronic and military equipment.
Product: Conductive coating silicon
Key features
- High conductivity
- Excellent sealing effectiveness (waterproof and dust proof)
- RoHS compliant
- Great resilience
- Better inner core resilience, compared to conventional solid-filled conductive silicone products
- Thin conductive coating layer provides good EMI shielding effectiveness
- More reasonable shielding cost due to use of conductive filler only on thin layer
- Very low compression force required to seal the applied places
Contact details: www.sunkyoungst.en.ec21.com
Indian distributor: Progressive Engineers, Ph: 0260-2997744, +91-9324249478; www.progressiveengineers.net
Protectron Electromech (P) Ltd
Protectron Electromech (P) Ltd is a supplier of EMI/RFI shielding products to the commercial and military markets. It has over 20 years’ experience in the RF shielding field. It designs and manufactures both standard catalogue and customised shielding products.
The complete shielding product line includes all sizes, shapes, compositions and mounting options.
Key features- Different types of designs available like SMT, through-hole, single part and double part construction
- Positive locking between shield frame and lid to withstand bumps and vibration tests
- Available in different types of materials, e.g., brass, phosphor bronze, copper, CRCA, stainless steel, nickel silver, beryllium copper, mu-metal, etc.
- Available in tray, tape and reel packing to facilitate production in pick-and-place SMT/through-hole assembly machines
Contact details: www.protectron.in
MG Chemicals
The 838AR total ground carbon conductive coating is an economical, conductive paint that is used to create grounded, conductive, static-free surfaces, or to provide cost-effective shielding from electromagnetic or radio frequency interference (EMI/RFI) at frequencies below 1MHz. The cured coating is a durable acrylic lacquer pigmented with a highly conductive carbon powder. The easy-to-use aerosol uses a solvent based system that can be air-cured at room temperature. It offers excellent conductivity and strong adhesion to plastics.
The acrylic resin coat is smooth, hard, durable, scratch-resistant and abrasion-resistant, so that painted surfaces may be used as static-free workbenches.
Product: 838AR total ground carbon conductive coating
Key features
- Cost-effective conductive coating
- Provides > 50dB of EMI/RFI shielding at frequencies < 1 MHz
- Smooth, durable, abrasion-resistant finish
- Surface resistivity of approximately 136 Ω/sq. for one coat (~1 mil)
- Quick drying time, no heat curing required, easy to apply
- Mild solvent system, safe on polystyrenes
- Strong adhesion to acrylic, ABS, polycarbonate and other injection moulded plastics
- Adheres well to wood
- Low VOC; HAP-free; does not contain toluene, xylene or MEK
Contact details: www.mgchemicals.com
Indian distributor: Progressive Engineers, Ph: 0260-2997744, +91-9324249478; www.progressiveengineers.net
