EMI shielding gaskets for military electronics are used in everything from touchscreens to targeting systems. To prevent electromagnetic interference (EMI) from disrupting electronic equipment, Elasto Proxy custom-fabricates EMI shielding gaskets from particle-filled silicones. These specialized materials combine the materials properties of silicone rubber with the electrical properties of metal. Elasto Proxy uses waterjet cutting to convert shielding silicones, and bonds cut lengths with conductive adhesives.
EMI gaskets from Elasto Proxy meet the requirements of MIL-DTL-83528, a U.S. Defense Logistics Agency (DLA) specification for electrically-conductive elastomeric shielding gaskets. MIL-DTL-83528 establishes minimum shielding effectiveness levels for various material types over a frequency range of 20 MHz to 10 GHz. MIL-DTL-83528 also specifies hardness or durometer (Shore A) measurements for shielding silicones that are categorized as low, medium, or high durometer.
Advantages of Elastomeric Shielding Gaskets
Traditionally, EMI shielding has been made of metal sheets and formed or fabricated into custom shapes. Sheets of copper, aluminum, and steel provide rigidity and strength, but can deform under the mechanical pressure that’s required for sealing. Once deformed, metal EMI shields tend to maintain their deformed shape and may admit electronic interference. Some metals are also susceptible to rust, corrosion, and oxidation.
Today, EMI shielding materials include flexible metal screens, metal wires, and metal foams. Coatings made of metallic inks are sometimes applied to the interiors of electronic enclosures. Each EMI shielding method has its advantages, but military electronics may need to meet different requirements. For military touchscreens, engineers need EMI gaskets that can resist compression, withstand water and sunlight, and survive temperatures ranging from desert heat to arctic cold.
Silicone Shielding Gaskets
Silicones are a family of synthetic rubbers that provide thermal stability over a wide temperature range. They retain their elastic properties after long periods of compressive stress and resist water, ozone, and ultraviolet light. When filled with tiny metal particles, silicone compounds can be used for environmental seals that resist EMI and also provide reliable electrical conductivity. For military applications, these metal particles are usually pure silver, silver-coated metal, or nickel-coated graphite.
Particle-filled elastomers aren’t new, but some engineers remain skeptical that shielding silicones can meet all of their application requirements. That’s because older compounds were harder, higher-durometer materials with poor compressibility and limited tear strength. Today’s newer particle-filled silicones include lower-durometer compounds that resist tearing and support reinforcements. They also offer alternatives to fills made of pure silver, a precious metal that’s subject to sharp price increases.
MIL-DTL-83528 EMI Shielding Gaskets
Elasto Proxy custom-fabricates EMI shielding gaskets from silicones as soft as 30 and 40 durometers and with tensile strengths of 90 psi and 120 psi, respectively. For additional resistance to tearing, SSP’s lower-durometer, particle-filled silicones can be reinforced with an inner layer of conductive fabric or mesh. At our manufacturing center near Montreal, Canada, we use water jet cutting to convert MIL-DTL-83528 materials and can bond cut lengths with electrically-conductive adhesives.
Whereas older, highly-filled silicone compounds had insufficient tear strength, these newer silicone compounds can support ruggedized products and thinner, smaller, lighter EMI shielding. Depending on a project’s specific requirements, these EMI shielding gaskets can be used in military touchscreens and other defense electronics. Elasto Proxy also custom-fabricates EMI shielding gaskets from medium-durometer and higher-durometer silicones that meet MIL-DTL-83528 requirements.
EMI Gaskets for Military Electronics
Would you like to learn more EMI shielding gaskets for military electronics? Then download Elasto Proxy’s new white paper. This in-depth guide compares cost, conductivity, and shielding strength for silicones with various fill materials. The white paper also describes all of the MIL-DTL-83528 EMI shielding materials that Elasto Proxy custom-fabricates, including two Qualified Product List (QPL) materials.
