EMI Shielding and Materials

Q: What are EMI materials?

A: EMI (Electromagnetic Interference) materials are materials designed to shield, absorb, or suppress electromagnetic radiation that can disrupt electronic devices or systems.

They help:

  • Prevent noise from escaping a device (emissions)
  • Protect sensitive components from external interference (immunity)

 

Q: What is EMI shielding?

A: EMI shielding is the process of blocking electromagnetic fields using conductive or magnetic materials to reduce interference.

Shielding typically works through:

  • Reflection (conductive materials)
  • Absorption (magnetic or lossy materials)• Multiple internal reflections

 

Q: What types of EMI materials are commonly used?

A:

Category Examples
 Examples
Conductive materials Copper, aluminum, silver High-frequency shielding
Conductive coatings & paints Silver, nickel, graphite-filled Plastic enclosures
EMI gaskets Conductive elastomers, fabric-over-foam Seams, doors, panels
Metal foils & tapes Copper tape, aluminum tape Cables, enclosures
Ferrites & absorbers Ferrite beads, tiles, sheets Noise suppression
Conductive fabrics Metallized textiles Lightweight shielding

 

Q: What is the difference between EMI shielding andEMI absorption?

A:  Shielding generally reflects EMI away from sensitive areas and Absorption typically converts EMI energy into heat.

Best designs often use both, depending on application requirements :

  • Shielding for high frequencies.
  • Absorbers for resonance control and magnetic fields

 

Q: What materials are most effective forhigh-frequency EMI?

A: For high frequencies (MHz–GHz), commonly used materials include: 

  • Copper
  • Aluminum
  • Silver-plated materials
  • Conductive coatings

Effectiveness depends on conductivity, thickness, continuity and overall system design.

 

Q: What materials are best for low-frequency or magneticfields?

A: Low-frequency EMI (e.g., power lines,transformers) requires high-permeability materials, such as:

  • Ferrites
  • High‑permeability alloys (e.g. mu‑metal‑type materials)
  • Nanocrystalline alloys

Conductive metals alone are not effective at low frequencies.

 

Q: What are EMI gaskets used for?

A: EMI gaskets maintain electrical continuity across:

  • Doors
  • Panels
  • Seams
  • Removable covers

They may also provide:

 

Q: How is EMI shielding effectiveness measured?

A: Shielding performance is expressed as Shielding Effectiveness (SE) in decibels (dB)

Illustrative examples under controlled laboratory test conditions may include:

  • 20 dB → 99% reduction
  • 40 dB → 99.99% reduction
  • 60 dB → 99.9999% reduction

*Actual shielding performance varies depending on material, thickness, design, installation, grounding, and test method. These values are not guaranteed performance levels.

Measured using standards such as:

  • IEEE 299
  • MIL‑STD‑285
  • ASTM D4935

 

Q: How do EMI materials affect grounding?

A: EMI materials typically require appropriate grounding as part of the overall system design to:

  • Minimize re-radiation
  • Support stable shielding performance

Inadequate grounding may reduce shielding effectiveness and should be evaluated during system design.

 

Q: Are EMI materials required for regulatory compliance?

A: EMI control measures, including EMI materials, are often used to support compliance with regulations such as:

  • FCC (USA)
  • CE / EMC Directive (EU)
  • CISPR
  • ISO / IEC standards

Regulatory compliance is determined at the finished‑product level based on applicable testing and approval processes. The use of EMI materials alone does not ensure compliance.

 

Q: Can plastics provide EMI shielding?

A: Standard plastics are non-conductive, but they can be modified using:

  • Conductive fillers
  • Metallization
  • Conductive paints or coatings

This allows lightweight and cost-effective enclosure designs.

 

Q: What industries commonly use EMI materials?

For regulated industries such as medical, aerospace, and defense, additional regulatory requirements, certifications, and approvals may apply depending on the application.

 

Q: What factors should be considered when selectingEMI materials?

A: Key considerations:

  • Frequency range
  • Required shielding effectiveness
  • Mechanical durability
  • Environmental conditions
  • Weight and space constraints
  • Cost
  • Compliance requirements

 

Q: Can EMI materials degrade over time?

A: Yes. Performance can degrade due to:

  • Corrosion
  • Oxidation
  • Mechanical wear
  • Compression set (for gaskets)
  • Environmental exposure (temperature, humidity)

Material selection and testing are critical for long-term reliability.

 

Q: What is the difference between EMI and EMC?

A: EMI materials are tools used to achieve EMC compliance.

 

 

Disclaimer :

This document is provided for general informational purposes only. It does not constitute engineering, regulatory, or compliance advice and does not replace application‑specific design, validation, or testing. Performance and regulatory compliance depend on the specific product design, materials selected, installation, and testing conditions.

TE Connectivity makes no representations or warranties, express or implied, regarding the suitability of any material for a specific application. Product selection and validation remain the responsibility of the customer. Specifications are subject to change without notice.