ENCLOSURE GASKETS


Specialist gasket profiles offer enhanced EMC protection


Andy Pye looks at the different material and profile options available when selecting an EMC shielding gasket.


E Material


Conductive fabric over foam material Carbon-filled conductive rubber


Silver-filled conductive rubber


Oriented wires in silicone rubber Fingerstock Knitted wire


xtruded sections of standard gasket profiles provide a simple and effective means of sealing enclosures, cabinets, vehicles and HVAC


installations to common IP ratings such as IP44, IP55, IP65 and IP66. Paint protection and compensation of varying gap thicknesses are further important factors in gasket application. Extruded gaskets for enclosures and other purposes are available in self- adhesive, self-grip (clip-on), channel fixing and window type (with expansion insert). The range supplied by EMKA now includes in excess of 730 sections with or without a spring clip mounting spine for environmental sealing, equipment protection or personnel protection. Materials used include EPDM, NBR, CR, PVC and silicone, as well as many with an EMC-compatible coating. A bespoke custom design service is also available. Self-locking gaskets clad in conductive fabric (a polyester fabric with a nickel- based electrochemical treatment) are


available in various sections according to the standards available. They offer electrical conductivity, electromagnetic shielding and elevated resistance to friction and corrosion. These are utilised for shielding


electrical and telecommunications lockers, especially when there is an interlocking attachment system, in the same way that the same non-conductive gaskets are used. EMC gaskets are used in places where


parts need to be disassembled when needed or to avoid RF energy leakage. They are widely available in different shapes and sizes. The material that is used also varies leaving the main question being which gasket to use for which purpose. EMC gaskets are very useful to close gaps that leak RF energy. There are some factors to consider when choosing the right gasket. The following types of gasket can be deployed, depending on how electric contact is established: Clamping; Filling; Covering. n


Advantage Resilience of the material.


Fluid and conductive seal.


Fluid and conductive seal. Good resilience, reusable and available in a wide variety of sizes and shapes.


Fluid and conductive seal. Able to breach corrosion layers if ends are sharp. More points of contact provide better shielding.


Best suited for sliding contacts (clamping).


Most resilient gasket with most points of contact. Available in a wide variety of materials. Available as all-metal gasket and knitted wire over foam.


Teethed or punctured Brass or Beryllium-Copper sheet


Adhesive tape


Best penetration of corrosion layers. Good shielding performance if carefully applied.


Limitation


Foam cracking or position shifting possibility. Generally low shielding effectiveness. Moderate shielding effectiveness.


Contact area might need special treatment due to silver content (to avoid corrosion). Wider gaskets due to higher material requirement.


Environmental issues (Be-Cu), few points of contact if only one strip used, breaks easily.


Risk of metal debris falling into circuitry after cutting (dipping recommended). Generally not available as sheet material. Damaged if over-compressed. Shielding effectiveness generally depends on wire density and compression force.


Generally not reusable. Low resilience.


Conductivity of glue doubtful. Not reusable: leaves residue. Long term stability questionable especially in differing environments.


EMC Testing 2018 Vol 1 No. 1 /// 5


❱ ❱ Enclosure sealing gaskets are available in a wide range of different profiles


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