Electromagnetic interference (EMI) occurs when electromagnetic energy from sources external or internal to electrical or electronic equipment effects the equipment adversely. Radio frequency interference (RFI) is the electrical noise that negatively influences the operation of electronic equipment. EMI or RFI may be:
- Emitted by a source
- Coupled between components
- Radiated through openings of any kind
- Conducted through a cable
The use of shielding materials is an effective way to reduce EMI and RFI. EMI/RFI shielding material can be used in five different ways to protect your equipment:
- Shielding for Containment: preventing the escape of interference produced by a device
- Shielding for Exclusion: preventing the intrusion of interference on a certain device
- Shielding plus Pressure Sealing: the shielding structure must also provide pressure containment
- Grounding and Contacting: grounds imperfectly grounded structures
- Absorption: by ferrites and ferrite-filled material
Things to Consider
When selecting an EMI/RFI material, consider these important factors:
- frequency range in question
- shielding effectiveness
- mechanical requirements
- compression-deflection
- compression set
- conductivity/stability
- installation cost
- flame retardant requirements
- galvanic compatibility with mating surfaces
Quick Reference EMI/RFI Shielding Material List
**Note: list is for quick reference only. Contact LGS for specific details.
Metal with Elastomer
- Connector gaskets
- Oriented wire in silicone
- Conductivity loaded elastomers
- Combination strip gaskets
- Mesh strip with elastomer core
- Silicone or neoprene impregnated wire mesh
Metalized Fabric over Foam
Metal Only
- Wire mesh strips or tape
- Seamless knitted wire mesh die-compressed gaskets
- Wire mesh with aluminum strips
- Metal screen and woven wire cloth
Fingerstock
Laminates
Composite Assemblies
Adhesives and Tapes
Cable and Wire Shielding
Conductive Caulks, Coatings and Sealings
