Use the tables below for an EMI shielding comparison with electrically conductive silicones.
EMI/RFI elastomers are shielding materials that combine the advantages of rubber with the electrical properties of metals. An inert, synthetic elastomer, silicone offers thermal stability over a wide temperature range along with resistance to ozone, water, and sunlight. When filled with tiny metal or metal-coated particles, silicone compounds combine EMI shielding and electrical conductivity with environmental sealing.
EMI Shielding Comparision: Volume Resistivity
The table below shows the relationship between filler type, electrical conductivity, and typical volume resistivity (VR) as measured in ohms per centimeter. Direct methods for measuring shielding effectiveness can be expensive and complex, so VR is a commonly-used method for indicating EMI shielding effectiveness indirectly. Note that typically, the fill material in EMI gaskets is pure silver, or a silver-plated or nickel-coated material.
Filler Type | Electrical | Typical VR (ohms/cm) |
Silver | Extremely Conductive | .0009 |
Silver-Aluminum | Super Conductive | .003 |
Silver-Copper | Super Conductive | .003 |
Silver-Glass | Very Conductive | .006 |
Nickel-Graphite | Conductive | .01 |
Carbon Black | Semi-Conductive | 8.0 |
EMI Shielding Comparison: Costs
Today’s electronic designers can specify alternative particle fills. Choices such as nickel-graphite cost significantly less, as the table below shows. Note the difference between silver, silver-aluminum, and nickel-graphite.
Filler Type | Cost |
Silver | $$$$$ |
Silver-Aluminum | $$$$ |
Silver-Copper | $$$$ |
Silver-Glass | $$$ |
Nickel-Graphite | $$ |
Carbon Black | $ |
EMI/RFI Shielding Materials Guide
When making an EMI shielding comparison, refer to the EMI/RFI Shielding Material Guide below as well. Many of SSP’s materials are part of the M93528 Qualified Product List (QPL) from the Defense Logistics Agency (DLA), part of the U.S. Department of Defense. MIL-DTL-83528 is a U.S. military detail specification for electrically conductive elastomeric gaskets.
