Electromagnetic interference (EMI) is a persistent challenge in modern electronic and communication systems. It can degrade performance, cause data loss, or even damage sensitive equipment. To mitigate this risk, engineers employ EMI shielding—using conductive or magnetic materials to block unwanted electromagnetic waves. Among the most effective materials used for this purpose are metals.
This article explores the most commonly used metals in EMI shielding, highlighting their unique characteristics, advantages, and specific use cases.
Why Use Metals for EMI Shielding?
Metals are ideal for EMI shielding because of their electrical conductivity, magnetic permeability, corrosion resistance, and durability. Depending on the EMI type—whether radiated or conducted—and the frequency range, engineers may choose metals with different properties.
Metals work in two principal ways:
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Reflection: Blocking EMI by reflecting electromagnetic waves due to high conductivity.
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Absorption: Absorbing and dissipating electromagnetic energy, especially at lower frequencies or magnetic fields.
For a deeper technical explanation, visit the IEEE EMC Society’s overview on shielding.
Copper – The Gold Standard for EMI Shielding
Copper is arguably the most widely used metal in EMI shielding applications due to its excellent conductivity and effectiveness across a wide frequency range.
Advantages:
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Outstanding electrical and thermal conductivity
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Excellent shielding effectiveness against both electric and magnetic fields
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Corrosion-resistant when treated or alloyed
Applications:
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PCB enclosures
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Medical equipment
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Telecommunication devices
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Shielded cables
Aluminum – Lightweight and Economical for EMI Shielding
Aluminum offers a balance between cost, weight, and EMI shielding performance.
Advantages:
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Lightweight and easy to fabricate
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Good conductivity and corrosion resistance
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Cost-effective for large enclosures
Applications:
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Aerospace and automotive electronics
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Mobile device enclosures
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Foil tapes and EMI gaskets
While aluminum is less conductive than copper, it performs well when weight is a critical design factor.
Steel – Durable and Structurally Sound
Steel, especially stainless steel, is favored in applications requiring mechanical strength along with EMI shielding.
Advantages:
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Strong and impact-resistant
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Offers magnetic shielding (low-frequency EMI)
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Cost-effective in structural applications
Applications:
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Military enclosures
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Industrial control cabinets
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Medical imaging rooms
Nickel – Corrosion Resistant and Magnetically Active
Nickel is typically used in EMI shielding as an alloy or coating, thanks to its excellent corrosion resistance and magnetic properties.
Advantages:
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Moderate conductivity
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High magnetic permeability
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Effective in layered and composite materials
Applications:
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Conductive paints
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EMI gaskets
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Plating on plastic or polymer components
Nickel alloys like permalloy are valuable for magnetic field attenuation.
Silver – High Performance for Sensitive EMI Shielding
Silver boasts the highest electrical conductivity of all metals, making it ideal for high-frequency or sensitive applications.
Advantages:
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Exceptional shielding at microwave and millimeter-wave frequencies
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Often used as a conductive filler
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Great thermal conductivity
Applications:
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Satellite systems
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Microwave communications
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Medical diagnostic equipment
Due to its cost, silver is often used as a thin coating over less expensive substrates.
Brass – A Cost-Effective Copper Alloy
Brass, made from copper and zinc, combines the conductivity of copper with improved machinability and corrosion resistance.
Advantages:
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Affordable yet effective
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Easier to form than pure copper
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Good EMI shielding properties
Applications:
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Connectors and terminals
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RF shielding boxes
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Architectural shielding in smart buildings
Mu-Metal – Specialized for Magnetic EMI Shielding
Mu-metal is a nickel-iron alloy known for its extremely high magnetic permeability. It is often used in applications where low-frequency magnetic shielding is required.
Advantages:
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Excellent low-frequency magnetic shielding
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High magnetic saturation
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Reduces electromagnetic leakage
Applications:
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MRI rooms
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Audio transformers
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Electromagnetic isolation enclosures
Mu-metal must be carefully handled and annealed after fabrication to retain its properties.
Beryllium Copper – Combining Strength and EMI Shielding
Beryllium copper (BeCu) is used where EMI shielding and mechanical performance must go hand-in-hand.
Advantages:
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High fatigue resistance and elasticity
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Excellent conductivity
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Can maintain contact pressure over time
Applications:
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EMI spring finger gaskets
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Modular panel connectors
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Military communication equipment
Gold – Premium Metal for Niche EMI Shielding Applications
Gold is not commonly used for bulk shielding due to cost, but is favored for optical, transparent, and corrosion-proof applications.
Advantages:
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Doesn’t tarnish or oxidize
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High conductivity and reflectivity
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Excellent for thin-film deposition
Applications:
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Transparent EMI coatings
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Satellite and aerospace windows
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High-end micro-connectors
EMP and HEMP Considerations in EMI Shielding Metals
When it comes to Electromagnetic Pulse (EMP) or High-Altitude EMP (HEMP) protection, material selection becomes more demanding. These phenomena generate rapid, high-energy bursts capable of destroying unshielded electronics.
Material Requirements for EMP Filters:
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Ultra-fast conductivity to respond within nanoseconds
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High magnetic saturation to absorb large energy spikes
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Thermal and mechanical robustness
Metals like copper, beryllium copper, and mu-metal are especially suited to EMP shielding. These materials are often used in:
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Government and military communication networks
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Data centers and financial infrastructure
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Aerospace and aviation electronics
Learn more from this military EMP shielding standards document (MIL-STD-188-125).
For more information, please refer to our article
<AC EMI Filter VS DC EMI Filter>.
