Generally, the intensity of interference to the outside world and its own ability to resist outside interference when electronic equipment is working, we call it electromagnetic compatibility.
Electromagnetic Compatibility (Electromagnetic Compatibility) abbreviation EMC means that an electronic device neither interferes with other devices, nor is it affected by other devices. Electromagnetic compatibility is one of the most important indicators of product quality, just like the safety we are familiar with. Electromagnetic compatibility involves human body and environmental protection, so the equipment must be electromagnetically shielded to reduce the radiation interference of the environment to the equipment or the equipment to the environment, so that the equipment can adapt to the complex working environment, ensure that the equipment normally realizes the design function, and improve the reliability of the equipment Sex and safety.
Below we list common electromagnetic shielding materials:
1. Conductive rubber
Conductive rubber is to evenly distribute conductive particles such as silver-plated glass, silver-plated aluminum, and silver in silicon rubber, and contact the conductive particles through pressure to achieve good conductivity. Its main function is sealing and electromagnetic shielding. The product can be molded or extruded, and there are sheets or other punching shapes to choose from. The shielding performance is up to 120 dB (10 GHz).
Conductive rubber must be subjected to a certain compression force to conduct good conduction, so the structural design must ensure that the appropriate pressure is not overpressured. The best height compression of the plate is 7-15%; the best height compression of solid circle and D-shape is 12-30%; the best height compression of tubular and P-shape is 20-60%.
2. Conductive cloth
The conductive cloth material is on the polyester fiber. First, chemical deposition or metal physical transfer of metal nickel to the polyester fiber, and then plated with a high-conductivity copper layer on the nickel, and then electroplated on the copper layer with an anti-oxidation machine to prevent corrosion The combination of nickel metal, copper and nickel provides excellent conductivity and good electromagnetic shielding effect, and the shielding range is 100K-3GHz.
Surface resistance: ≤0.05Ω/inch (100g load)
Shielding effect: 60 dB~ 80dB/30MHz~1GHz
Heat resistance temperature: -10℃-110℃
Tensile strength: ≥1.3 (kg/25mm)
Initial adhesion: 1600g/25mm
Maintain adhesion: 1440Min/inch
Flame retardant rating: Pass UL
3. Conductive foam
Conductive foam is a flame-retardant sponge wrapped with conductive cloth. After a series of treatments, it has good surface conductivity and can be easily fixed on the device to be shielded with adhesive tape. Shielding materials with different cross-sectional shapes, installation methods, UL ratings and shielding effectiveness are available.
Average shielding performance: 90dB
Surface resistance: above 0.07Ω/㎡
Operating temperature: -40°C～70°C
Permanent compression set: 8%～20%
Fire protection: UL certification
4. Conductive cloth tape
Conductive cloth tape is a back adhesive with high conductivity. This kind of tape has excellent flexibility, is suitable for various surfaces, and can withstand high temperatures up to 200°C.
Good conductivity and shielding effect
Good anti-friction performance, anti-friction times can reach 5,000,000 times
Good metal bonding and Z-direction conductivity
Good processability, soft texture, cut without burrs, anti-fingerprint and dirt, anti-oxidation treatment
Volume resistance: 0.03～0.06Ω/㎡
Shielding performance: 80dB
Adhesiveness: heat-sensitive conductive pressure-sensitive adhesive
Temperature range: -10°C～120°C
5. Conductive shielding tape
Conductive shielding tape is a kind of metal foil or conductive cloth with highly conductive adhesive. Its conductive adhesive and conductive substrate form a complete conductor. It can be bonded to any metal surface to complete electrical laps and gaps. Closed. Shielding conductive tape is an economical and convenient shielding material.
It is used to seal the joints between EMI shielding rooms, shells and electronic equipment, wind cables for shielding, provide a reliable grounding surface, and provide electrical contact to surfaces that cannot be welded.
6. Conductive paint
Anti-electromagnetic wave interference shielding paint, commonly known as conductive paint. Conductive paint uses composite particles containing copper and silver as conductive particles and is a paint with good conductive properties. The conductive paint is sprayed and brushed to make the completely insulated non-metal or non-conductive surface have the characteristics of absorbing, conducting and attenuating electromagnetic waves like metal, thereby playing the role of shielding electromagnetic interference.
Conductive effect: ≤0.025Ω/cm² (the thickness of the paint film is not less than 20μm)
Application conductivity parameters: 1Ω/20μm film thickness/distance 10cm
Suggested film thickness: 20-25μm
7. Microwave absorbing materials
Microwave absorbing material is a kind of material that can absorb microwave and electromagnetic energy with less reflection and scattering. Also known as radar absorbing material or radar stealth material. The basic principle of microwave absorption is to convert microwave energy into other forms of motion energy through a certain physical mechanism, and convert it into heat energy through the dissipation of the motion. All forms of lossy motion excited by microwaves can be the absorption mechanism. Common mechanisms include electric induction, magnetic induction, electromagnetic induction, and electromagnetic scattering.