Stockwell Elastomerics manufactures custom EMI shielding gaskets, EMI/RFI gaskets and other EMI management gaskets of various typesConductive rubber/conductive siliconeEMI shielding materials as per specification.
Stockwell Elastomerics also manufacturescombined silicone sponge - wire meshEMI shielding gaskets.
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EMI Gasket Materials
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Contains small touch-and-feel samples of EMI sealing materials.
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What are EMI Gaskets?
EMI gaskets, made from electrically conductive elastomers such as silicone or fluorosilicone, provide environmental sealing, thermal insulation, and protection from electromagnetic interference (EMI). They support a variety of manufacturing methods, are available in materials that meet the most stringent standards, and can be supplied with conductive adhesive backing for easy installation. There are many types of EMI shielding materials, but electrically conductive silicones offer gasket designers performance and versatility.
In particular, EMI gaskets seal the gap between two contact surfaces. Like other types of environmental seals, they seal or seal the external environment to prevent leakage. EMI gaskets are distinguished in that they also seal against conducted or radiated EMI that can disrupt circuits. When this electromagnetic interference "noise" hits the EMI board, the signals are negated and the resulting electrical current is conducted to ground. Silicone is typically an electrical insulator rather than an electrical conductor, but the addition of metal or metal-coated particles imparts the necessary electrical conductivity.
Manufacturing EMI Gaskets
Stockwell Elastomerics offers manufacturing for all of these types of EMI shielding gaskets:
- EMI water jet cut connection
- molded EMI gasket
- Arame Gasket/EMI Sponge
- EMI gasket with conductive adhesive
More aboutSee how EMI Gaskets are made below..
EMI/RFI Management Requirements
Growing wireless and electronics markets have brought increased management risks for electromagnetic interference (EMI) and radio frequency interference (RFI). This applies to consumer, commercial, industrial and military applications. Management of EMI by electronic equipment manufacturers is required by Title 47 of the Code of Federal Regulation and Mil-DTL-461. These are some of the most important EMI standards and their applications:
- Title 47 CFR Part 15: Radio Frequency (RF) Equipment.
- Title 47 CFR Part 18: Industrial, Scientific and Medical Equipment
- Title 47 CFR Part 68 – Telecommunications
- Mil-STD-461 - EMI Control for Subsystems and Devices
- Mil-DTL-83528: Gasket Material (Related) for EMI/RFI
EMI management with gaskets
Radiated EMI is often emitted by unwanted antennas, meaning cables and internal components can act as emitting antennas. A common practice for dealing with EMI radiation and EMI susceptibility is to completely enclose electronic components in a conductive enclosure.This usually includes a housing, cover and conductive gasket; it is imperative that the cover and housing are in contact all around, i.e. a conductive connection. Stockwell Elastomerics manufactures EMI gaskets for Class A (typically industrial), Class B (typically residential), and military applications. EMI Gaskets manufactured by Stockwell Elastomerics routinely perform EMI mitigationenvironmental fence(rain, dust, laundry, etc.)
Conductive Rubber/Conductive Silicone EMI Shielding Gaskets
Stockwell Elastomerics manufactures custom EMI shielding gaskets from a variety of electrically conductive rubber materials (also called conductive silicone). These silicones with particles or with particlesFluorsiliconEMI/RFI gaskets are typically thinner, 0.010" to 0.062" thick, with full XYZ axis conductivity, and when properly compressed can pass IP67 or NEMA Type 6 immersion tests in addition to EMI shielding.
Commercial EMI Gasket Material: Class A and Class B
Filled with nickel/graphiteSilicone sealing materialsThey are primarily specified for industrial, commercial and residential applications due to their good cushioning, strong sealing properties and low cost. Most commercial EMI gasketing applications can be met with Ni/C products. Larger cases may require thicker, softer EMI gaskets (see Combining Silicone Sponge and Wire Mesh EMI Shielding Gaskets).
Common EMI Materials (Class A and Class B)
- SNE-540: Nickel/Graphite Filled Silicone (Hardness 45)
- EC-2130: Nickel/Graphite Filled Silicone (Hardness 30)
- SNEF-60: Fluorosilicone filled with nickel/graphite (hardness 60)
Military and aerospace EMI materials
Mil-STD-461 is the global EMI-related specification for equipment and subsystems. MIL-DTL-83528 is the specification for EMI-filled gaskets. This requirement is very concise: when a print requires a MIL-DTL-83528 Type X seal, the polymer, filler, cushioning and mechanical properties are specified. Most popular military/aviation EMI gaskets generally require silver-plated aluminum to meet MIL-DTL-83528 specifications. Military or aerospace applications may also use fluorosilicone in place of silicone for its fuel and chemical resistance.
Common filler and polymer MIL-DTL-83528
- Type A = Silver Coated Copper - Silicone (65 Durometer)
- Type B = Silver Coated Aluminum - Silicone (65 Durometer)
- Type C = Silver Plated Copper - Fluorosilicone (75 Durometer)
- Type D = Silver Coated Aluminum - Fluorosilicone (70 Durometer)
- Type M = Silver Coated Lens - Silicone (65 Durometer)
EMI Gaskets for Waterjet and Prototype EMI Gaskets
Innerwaterjet cuttingand stock materials enable Stockwell Elastomerics to quickly deliver prototypes and EMI gaskets for production. 2D EMI gaskets can be prototyped on Stockwell Elastomerics waterjet cutting machines and then inserted into molded or production parts, all using the same EMI compound.
Molded EMI shielding gaskets
Stockwell Elastomerics molds conductive silicone and fluorosilicone rubber compounds in your custom molding line. EMI gasket shapes allow the designer to add gasket ribs and other performance enhancing features to optimize environmental sealing and EMI shielding properties. Stockwell Elastomerics has a wide range of compounds that meet MIL-DTL-83528 ratings for Electrically Conductive EMI Shielding Gaskets.
Combined wire mesh and silicone sponge EMI shielding gasket
Stockwell Elastomerics manufactures EMI Gaskets from a custom blend of expanded silicone or fluorosilicone sponge and has a braided wire mesh attached to the edge (see image at right). Combination gaskets are generally thicker and softer than conductive rubber EMI gaskets. This thicker, softer grade allows for more compression with less clamping pressure and provides a case seal with wider tolerance stacks.
Matching EMI gaskets are often used for large NEMA enclosures or other enclosures with limited clamping forces or sheet metal enclosures. Since sponge or silicone foam is very compliant at low clamping forces, they "suck up" mismatches (flatness tolerances) between the gasket surfaces, creating an outdoor water seal. The woven mesh electrically connects the metal surfaces. Note: Conductive chemical or bare metal layers are required at the network contact point to allow a conductive path.
EMI/RFI combination gaskets are most commonly manufactured in .125" (3.18mm) and .25" (6.4mm), although other thickness options are available upon request. Monel mesh screen is used for its corrosion resistance.
EMI gasket combination with UL listed silicone foam
Classified to UL 50E and UL 94V-0silicone foamsare often used for the water or dust sealing function of the combination joint. While the combined EMI gasket configuration has not been UL tested, the silicone foams have been. This third-party verification increases confidence that a pre-qualified, third-party gasket material is being used.
silicone foamIt has excellent UV and ozone resistance and long term rebound (compressive strength) making it a good choice for external EMI cabinet gaskets. Closed cell silicone foams are used whenwater sealif necessary, open-cell silicone foams are usedsealed against dustto shape
examples
- Closed cell silicone foam combination gasket- For EMI NEMA Type 3 or NEMA Type 4 enclosures where waterproofing and EMI/RFI shielding are required
- Combination seal made of open-cell silicone foam- For EMI vents or EMI filters used in power supply enclosures where dust tightness, UL 94V-0 and EMI shielding are required
EMI gaskets combined with silicone sponge
Closed cell silicone sponge materialsThey are best suited for rugged enclosures or enclosures where the gasket is not protected from air blast (IP66 or NEMA 4). Rubber-based silicone sponge materials are stronger and more closed-cell than liquid-based silicone foams, which is why they are most often specified for EMI-resistant or outdoor combination gaskets.
Silicone Sponge Combo EMI/RFI Gaskets are available in soft, medium and firm grades that are widely used in military enclosures and applications in remote locations where environmental conditions can vary widely from sub-zero to arid desert conditions. Braided monel wire mesh attaches to the opposite side of the perimeter (usually the inside of the window seam), protecting the wire mesh from the elements.
EMI gaskets combined with fluorosilicone sponge
Military and aerospace applications may require chemical resistance in addition to EMI shielding and environmental sealing; For these applications, Stockwell Elastomerics manufactures EMI combination gaskets using R10490closed-cell fluorosilicone sponge. Fluorosilicon shares many of the same properties as silicone, such as B. Resistance to high and low temperatures, but with improved chemical resistance. Fluorosilicone is typically specified only when chemical resistance is required due to its high price.
Adhesive mounts for combined EMI gaskets
- 256 million– General purpose (film coated) two layer acrylic pressure sensitive adhesive (PSA) is widely used. The PET backing layer gives the joint dimensional stability in the X and Y axes.
- 9485– High adhesion and strong adhesion. 3M 9485 offers high temperature resistance and is suitable for low surface energies such as powder-coated paints.
- F9473- High tack acrylic VHB adhesive is Stockwell Elastomerics' preferred adhesive for fluorosilicone compound EMI gaskets due to its superior fluid resistance.
Compression stopper or compression limiter for EMI gaskets
Stockwell Elastomerics offers EMI/RFI combination gaskets with compression stops, sometimes referred to as compression stops, to protect the gasket from torsion pinching. As the sealing materials relax, torques are very difficult to set. The use of compression stops allows assemblers to use torque specifications as the fasteners will seat against the carbide stop.
EMI gasket combination for large NEMA enclosures
Large EMI gaskets for cabinets and electrical enclosures are often treated with a corrosion resistant monel wire mesh attached to aclosed cell silicone sponge. Wire mesh/sponge gasket allows greater tolerances between sealing faces. Sponge and wire mesh provide low, forgiving clamping forces to prevent sheet metal flexing between latches or fasteners.
- closed cell silicone– Common thicknesses are 0.125″ and 0.250″. Closed Cell Silicone Sponge R10470-M and Medium Density Silicone Foam HT-800 are most commonly specified for eco-friendly gaskets. Gaskets are usually supplied with a high strength, pressure sensitive acrylic adhesive.
- Malla Monel– .125" x .125" wide and .250" x .125" wide monel braid is bonded to the inner or outer edge of the gasket to provide a reliable, relatively inexpensive EMI shielding gasket with long-term sealing against the outside. The Monel mesh is made from .0045″ braided wire conforming to QQ-N-281.
- Aluminiumgewebe(AMS 4182) or tinned copper clad steel wire (ASTM B520) are available to special order.
Request a free silicone
EMI Gasket Materials
tactile leaflet
Contains small touch-and-feel samples of EMI sealing materials.
Request brochure
How are EMI Gaskets Made?
EMI Silicone Gaskets can be made by water jet cutting, stamping or compression molding.
- waterjet cuttingIt's a tool-less process that's ideal for low to medium volume production and prototyping. With no tools to wait or pay for, Waterjet supports fast, cost-effective iterations before larger volume production begins. Sheets, continuous rolls and extrusions can be processed into finished part shapes.
- Trocarrequires metal tools or dies and this adds cost and time to projects. However, for mass production, stamping is economical, especially for flat joints processed from sheets or rolls. Like waterjet cutting, stamping helps nest parts to design cutting patterns that minimize material waste.
- compression moldingproduces EMI gaskets from ready-to-inject compounds instead of sheets, rolls or extrusions. Tools are required, but EMI gaskets are molded in one piece. For "bay window" style joints with a blank area in the center, compression molding can maximize material yield because there is no unused center to discard. Complex shapes can be formed to avoid PCB components, create retention features, or provide a form factor for lower clamp force.
EMC gaskets that are not made in one piece can be joined by cold joining or hot splicing.
- Kalte CollageBonds EMI materials with an RTV silicone adhesive or a non-silicone adhesive. Using a non-conductive adhesive increases the risk of EMI leakage, but conductive adhesives are available. With silicone-free adhesives, acrylic adhesives do not have the temperature resistance of silicones.
- hot splicejoins EMI materials by applying heat and pressure. A splicing tool or mold is required, but hot-spliced EMI gaskets always have consistent properties. They also don't have a "hard spot" like a cold-bonded EMI gasket.
Contact Stockwell Elastomerics for EMI gaskets
contact usMore help on EMI Gaskets, EMI/RFI Shielding Gaskets, Military EMI Gaskets, Combination Silicone Sponge and Wire Mesh EMI Shielding Gaskets, Waterjet Cutting and Molded EMI Gaskets.