1. Overview

Radio Frequency Interference (RFI) and Electromagnetic Interference (EMI) are disruptive electromagnetic emissions that affect the performance of electronic devices. Shielding and absorbing materials mitigate these effects by blocking or dissipating electromagnetic energy. These materials are critical in RF/Intermediate Frequency (IF) circuits, RFID systems, and high-frequency electronics to ensure signal integrity, regulatory compliance, and operational reliability.

2. Main Types and Functional Classification

Type	Functional Features	Application Examples
Metallic Shielding Foils	High conductivity, flexible, corrosion-resistant coatings	Smartphone enclosures, RFID tags
Conductive Elastomers	Elastomeric base with conductive fillers (e.g., silver, nickel)	Aerospace connectors, medical devices
EMI Absorbing Sheets	Flexible polymer matrices with magnetic particles (e.g., ferrite)	5G base stations, radar systems
Conformal Coatings	Thin-layer conductive paints or sprays	PCB shielding, IoT device casings
Textile-Based Shields	Woven fabrics with conductive yarns (e.g., silver-coated)	Wearable electronics, flexible antennas

3. Structure and Composition

Typical products feature multi-layer architectures:

• Base Substrate: Polymer films (PET, polyimide) or woven fabrics
• Conductive Layer: Metal deposits (aluminum, copper) or conductive inks
• Adhesive Interface: Acrylic or silicone-based adhesives for bonding
• Protective Coating: Anti-oxidation layers (e.g., nickel-gold plating)

Absorbing materials often embed lossy magnetic particles (ferrite, carbonyl iron) in elastomeric matrices to convert EMI energy into heat.

4. Key Technical Specifications

Parameter	Description	Importance
Shielding Effectiveness (SE)	dB attenuation across 30 MHz 40 GHz	Directly impacts signal-to-noise ratio
Surface Resistivity	0.01 100 /sq	Determines DC grounding performance
Relative Permeability	1 1000 (absorbing materials)	Influences magnetic field absorption
Temperature Stability	-55 C to +150 C operational range	Ensures reliability in harsh environments
Thickness	0.05 5.0 mm	Affects weight and flexibility

5. Application Areas

Primary industries include:

• Telecommunications: 5G/6G infrastructure, fiber optic transceivers
• Automotive: V2X communication modules, ADAS sensors
• Healthcare: MRI-compatible devices, wireless patient monitors
• Consumer Electronics: Foldable smartphones, AR/VR headsets
• Defense: Electronic warfare systems, stealth coatings

6. Leading Manufacturers and Products

Manufacturer	Product	Key Features
3M	Scotch 9703LE	Anisotropic conductive film for RF shielding
Laird Performance Materials	HF Absorber 41	8 40 GHz broadband absorption
Saint-Gobain	TYGARD TC 1191	Transparent conductive film for RFID antennas
Parker Chomerics	CHO-SEAL 1335	0.05 mm thick EMI gasket material

7. Selection Guidelines

Key considerations:

• Frequency Matching: Align SE performance with target bands (e.g., 2.4 GHz for Bluetooth)
• Environmental Resistance: Chemical exposure, humidity, and vibration tolerance
• Form Factor: Thin profiles for portable devices vs. rigid panels for infrastructure
• Cost-Performance Balance: Silver-filled materials offer superior conductivity but higher cost

Case Study: Automotive radar systems use ferrite-loaded silicones to suppress 76 81 GHz interference while maintaining thermal stability.

8. Industry Trends

Emerging developments include:

• 2D materials (graphene-enhanced composites) for sub-10 nm shielding layers
• 4D-printed reconfigurable absorbers with tunable frequency response
• RoHS-compliant alternatives to traditional heavy metal-based coatings
• Integration with AI-driven EMI prediction models for optimized design

Market growth is driven by 5G expansion, with projected CAGR of 9.2% (2023 2030) according to Grand View Research.