EMI Shielding Products
- Custom Gasket Fabrication
- Connector Gaskets
- Bonded O Ring
- Custom Gaskets
- Conduct-O-Knit Knitted Wire Mesh
- Conduct-O-Seal Combo Gasket
- Conduct-O-Elastomer
- Conduct-O-Seal Oriented Wire in Silicone Gasket Material
- Conduct-O-Mesh Tape
- Conduct-O-Foam
- Conduct-O-Bond
- Optical Filters For Electronic Displays
- Shielded Vent Panels
- ESC Board Level Shielding
- 300 Series
Overview of Material Type Options for EMI Shielding
Electromagnetic Interference (EMI) shielding is a crucial aspect of electronic device design, aimed at either containing emissions from devices or protecting them from external EMI sources. The main material types used for EMI shielding are as follows:
- Metal-based Shielding: Metal-based materials are one of the most effective for EMI shielding due to their high electrical conductivity, which allows them to reflect electromagnetic energy. Common metals used include:
- Copper Beryllium (CuBe): Known for its conductivity and spring properties, it is effective for gaskets that require frequent access.
- Aluminum: Lightweight and cost-effective, used in various forms, including foil and plating for shielding cases.
- Stainless Steel: Offers robustness and corrosion resistance, frequently used in heavy-duty applications.
- Nickel Silver and Other Copper Alloys: These are used in board-level shielding for their excellent conductivity and shielding effectiveness.
- Metal Mesh and Knitted Gaskets: These are made from various metallic wires (like Monel, tin-plated copper-clad steel) and are beneficial due to their resilience and effectiveness across a broad frequency range. They are typically used where a flexible, durable gasket is required.
- Conductive Elastomers: These materials combine the properties of rubber with conductive particles to shield against EMI while providing environmental sealing. Common fillers include:
- Silver-plated Copper (Ag/Cu): Provides excellent conductivity and shielding effectiveness.
- Nickel-coated Carbon (Ni/C): Offers good shielding effectiveness with less expense than silver.
- Silver-plated Aluminum (Ag/Al): Useful in high-frequency applications.
- Conductive Coatings and Paints: Applied to non-conductive surfaces to impart EMI shielding capability, these coatings are typically filled with conductive materials like copper, nickel, or silver. They are used in enclosures where traditional metal shielding cannot be employed.
- Fabric-over-Foam (FoF) Gaskets: These consist of a conductive fabric wrapped over a foam core, creating a gasket that provides EMI shielding and a compressible seal. This type is particularly suitable for enclosures requiring low closure force.
- Board-Level Shielding (BLS): This involves using metal cans or cages soldered directly onto printed circuit boards (PCBs) to isolate specific components or circuit sections. Materials used here include brass, copper, and tin-plated steel.
- Oriented Wire in Silicone: This type includes wires (like Monel or aluminum) embedded in a silicone binder, providing excellent EMI shielding and environmental sealing on irregular surfaces or in challenging environmental conditions.
Reflectivity and Absorption
Reflectivity and absorption are critical characteristics in shielding materials. Reflectivity depends on the material’s conductivity and is crucial for bouncing back incident electromagnetic waves. Absorption involves dissipating the electromagnetic energy within the shield material itself, and the material's permeability and thickness influence it.
Apertures and Gasketing
Apertures or gaps in enclosures can compromise shield effectiveness. Effective gasketing, particularly with materials that match the shielding's electromagnetic and physical properties, is essential to maintaining continuity and effectiveness across joints and openings.
Considerations for Selection
Selecting the right shielding material involves considering factors like:
- Frequency of operation (higher frequencies may require materials with better high-frequency performance).
- Mechanical and environmental stresses.
- Corrosion resistance and material compatibility, especially in mixed-metal scenarios.
The choice of shielding materials is extensive, and their application can vary significantly based on the specific EMI challenges and device requirements. Each material offers unique benefits and is selected based on specific conductivity requirements, magnetic permeability, physical properties, and environmental resilience.