Roger Ferreira
Sealing Solutions Provider at Elasto Proxy

Particle-filled, electrically-conductive silicones are a group of elastomers that provide EMI shielding and environmental sealing. The causes of electromagnetic interference (EMI) are numerous, but so are your choices when specifying metal-filled silicones for EMI gaskets. By working with a custom fabricator who understands your application, you can source electromagnetic shielding that meets your requirements for both performance and cost.

First, however, it’s important to understand why you need an EMI gasket – and why silicone is the right rubber to choose. After all, your engineering blueprint may simply say “rubber gasket”, and omit other details. Next, you’ll need to determine which type of metallic particles provide the best combination of performance and cost. Finally, it’s worth understanding how the conductive pressure sensitive adhesive (PSA) is applied to the silicone, and why the materials you buy cost what they do.

Metal-Filled Silicones for EMI Shielding

Electromagnetic interference (EMI) interference can disrupt, disable, and even destroy the sensitive components used in military electronics and medical equipment. EMI gaskets cost more than what some buyers might call “a regular rubber gasket,” but they’re worth the price. Just compare the cost of the damaged electronics in a military vehicle or medical monitor to that of EMI shielding. Every rubber has different properties, and an elastomer that’s good for cushioning might not provide EMI protection.

Other conductive elastomers are available, but particle-filled silicones combine the strengths of silicone rubber with specialized characteristics imparted by metal particles. An inert, synthetic rubber, silicone offers thermal stability over a wide temperature range and resists both ozone and ultraviolet (UV) light. Silicone rubber also resists water and many types of chemicals. When you choose a metal-filled silicone for EMI shielding and environmental sealing, you’re selecting a material with many desirable properties.

All Particle-Filled Silicones Aren’t the Same

Like other materials, particle-filled silicones are available in different types or grades. Today, specialty silicones with silver-coated aluminum particles are used widely in EMI shielding. Silver is more expensive than many other materials, however, and that’s reflected in the cost of silicone compounds with silver-coated aluminum particles. Nickel-coated, graphite-filled silicones cost less, but can still achieve the EMI shielding performance of silicones with silver-coated aluminum.

Are you skeptical of this claim? Elasto Proxy can source particle-filled, electrically conductive silicones from a trusted supplier that’s submitted its nickel-coated, graphite-filled silicones for third-party testing. All test results are available upon request, both for the nickel-coated, graphite-filled silicones and the silicones compounds with silver-coated aluminum particles. Please contact us for more information, and we’ll share the supplier’s test results with you.

Conductive PSA and Manufacturing Costs

Now that you understand why EMI gaskets cost more than “regular rubber gaskets”, are you still wondering why even the nickel-coated, graphite-filled silicones cost what they do? There are two ways to add the conductive PSA, and both involve costs. Laminating the PSA onto a silicone sheet or silicone roll is effective, but cutting a pattern from the material often results in some scrap or waste. Molded EMI gaskets are labor-intensive to produce, and tooling costs may apply.

Molding the gasket means pre-forming the silicone in an uncured state. Next, heat and pressure is applied for 15 minutes at a time. This process can take many hours, depending on the volume to produce. Finally, cutting is followed by manual placement. That’s why Elasto Proxy works with a trusted supplier of particle-filled silicones who produces rolls, cuts down the sheets, and applies the PSA. This promotes efficiency, and let us apply our own expertise to custom-fabricating your EMI gaskets.

How Can We Help You?

Do you have questions about EMI gaskets made from metal-filled silicones? For 25 years, Elasto Proxy has been solving sealing and insulation challenges in a variety of industries. By listening to all of your application requirements and analyzing all of your needs, our solutions providers can help.

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