One of the common questions we get at NEDC is what types of materials are available for EMI Gasketing materials. Since apertures can vary from thin to thick, and compression values can vary from extreme pressure to hardly any at all, we thought we’d present on one post all the EMI Elastomeric Gasketing options available. The idea behind all of the below materials is for the elastomer to act as an environmental seal, while either the conductive particles, or the electrically conductive portion of the elastomer takes care of the EMI shielding.
Electrically Conductive Solid Rubber EMI Gaskets
Oriented Wire Solid Rubber
These are oriented wires that are perpendicular to the rubbers direction. This provides good electrical contact by each individual wire. For that reason, more compression force is required to have the wires make good contact across the interface. Some solid rubber examples include fluorosilicone(AMS-R-25988 Type II, Class 1, Grade 40) and silicone rubber(ZZR765, A-A-59588 Class 2B 40, and Class 3A 30). The wire types available are, monel(QQ-N-281), aluminum(alloy 5056) and SnPhBronze(ASTM B105). This product is made by a number of manufacturers.
Expanded Wire with Elastomers
These materials are designed for applications where small apertures exist that require both a high pressure pressure seal but also a EMI shield. They are extremely thin ranging from .030’’ to .020’’ in thickness. These materials are available in thin sheet/roll form. Elastomers to choose from include fluorosilicone(AMS-R-25988 Type II, Class 1 Grade 40), neoprene(AMS-3222), and silicone(AMS-3302, or ZZR765 Class 2B, Grade 50). This product is made by a number of manufacturers.
Fluorosilicone/Silicone/EPDM EMI Gaskets
These are the main types of EMI Gasketing materials seen in industry. These are essentially rubber materials filled with conductive particles to provide good electrical conductivity, and shielding effectiveness. The MIL-DTL-83528 specification is the guide behind many of these type elastomers, and their test methods. Popular types include silicone and fluorosilicone filled with silver/aluminum particles. Other less well known types include EPDM polymers, or nickel-graphite fillers. These options have volume resistivities ranging from .002 ohm-cm to 5 ohm-cm. These products are made by a number of manufacturers.
Cellular Electrically Conductive EMI Gaskets
Condux Plus® PORON® Electrically Conductive Foam by Rogers Corporation
Condux Plus® PORON® Urethane Foam is an electrically conductive urethane foam that is used for EMI Shielding, and grounding pads. It features an extremely low compression set to maintain a good surface connection throughout the lifetime of products. 0.3mm(.013’’) and 0.5mm(.021’’) are the available thicknesses on these materials. Effective shielding of Condux Plus® is 300 MHz to 10 GHz @ 50 dBs. This product is a registered trademark by Rogers Corporation Datasheet is below.
CF Electrically Conductive Foam by Schlegel
These CF foam-based gaskets have great shielding effectiveness at high-frequencies, and low contact resistance. It has a low compression set as well. They are made up of urethane foam with nickel-copper filler. They are usually sandwiched on both sides with a knitted, non-woven conductive fabric. Most thicknesses are UL Fire Rated. See datasheet for more details below.
Fabric Over Foam
These materials are essentially low density foam that has a fabric jacket. The jacket provides conductivity while the foam provides the ease of compressibility. These EMI gasket materials come in a variety of different profiles for different apertures. These materials are often available in either sheet, or strip form. Cores include open cell urethane foam, or thermoplastic elastomers(TPEs).These can include nickel/copper or tin/copper fabrics. This product is made by a number of manufacturers. These require perhaps the lowest amount of compression force out of all options.
Oriented Wire Sponge Rubber
Oriented Wire cured in sponge is essentially a closed cell silicone sponge with oriented wires facing all the same direction. The sponge provides a low compression set, but allows it to be easily compressible with the wires providing electrical contact for EMI shielding. The specifications available for this type material are AMS-3195(Silicone Sponge) with different specifications for the oriented wires, including monel(QQ-N-281), aluminum(Alloy 5056) and SnPhBronze(ASTM B105). These materials allow for much thicker cross sections with availability up to .250’’ in thickness. This product is made by a number of manufacturers.
More Info/Cutting of EMI Gaskets
Naturally, NEDC provides all of these materials in die-cut gasket formats. Many of these materials are cut by our waterjet cutting machine. In addition, most of these options are available with electrically conductive adhesive or non-electrically conductive adhesive backings for ease of assembly. We do not think we left out any major types of EMI Shielding for gasket materials, however if we did please let us know! For more information regarding EMI Shielding materials, please contact firstname.lastname@example.org.