Particle-filled silicones for EMI shielding and environmental sealing

June 01, 2015 //By Dominic Testo, Specialty Silicone Products
Particle-filled silicones for EMI shielding and environmental sealing
Particle-filled silicones are elastomeric compounds that combine the advantages of silicone with the electrical properties of metals. An inert, synthetic rubber, silicone offers thermal stability over a wide temperature range and resists ozone and ultraviolet (UV) light.

Silicone rubber also resists water, and can be formulated to impart electrical conductivity. When filled with tiny metal particles, typically silverplated or nickel-coated, silicone compounds can be used for environmental seals that resist electromagnetic interference (EMI).

EMI shielding isn't new, of course, but some fabricators have concerns about particle-filled silicones. Silicones have desirable material properties, but loading a high percentage of particle filler into the rubber in an effort to increase conductivity can result in negative tradeoffs. Typically, industry professionals worry that particle filled electrically-conductive silicones are:

  1. too hard;
  2. too brittle;
  3. too expensive;
  4. have long lead times;
  5. limited by mold size dimensions;
  6. not thin enough for newer, thinner designs.

Solving sealing and insulation challenges

Today, a variety of industries are using particle-filled conductive silicones for EMI shielding and environmental sealing. Markets such as medical and military electronics and automotive are demanding, but so are the safety requirements for the kiosks in factories and various public venues. Are metal-filled elastomers right for these and other applications? Is it possible to source particle-filled silicones that aren't too hard, too brittle, too expensive, take too long to produce, or are too thick?

For fabricators, die cutters, and molders, it's important to understand that there are next-generation materials that address these concerns. It's also essential to have the technical knowledge to answer questions about these materials. Today, Specialty Silicone Products (SSP) supplies a line of conductive silicone elastomers that are designed specifically to overcome the most common material challenges. Designed to balance cost competitiveness with electrical conductivity, these particle-filled products include uncured moldable compounds, compression molded sheet stock, and continuous rolls all ready to be custom-converted by the individual fabricator.

By understanding the characteristics of these metal-filled silicones, gasket fabricators can suggest reliable, cost-effective compounds for sealing and insulation. Then, using whatever conversion method is most efficient, fabricators can supply EMI/RFI gaskets that meet demanding application requirements. Some industry professionals need convincing, however, so let's examine some common objections to using particle-filled silicones for shielding and sealing. Along the way, we'll look at how next-generation materials overcome these challenges.

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