Absorbing materials used inside the cavities of electronic devices such as laptops, mobile phones, and communication cabinets

Absorbing materials are materials that can effectively absorb wave energy such as sound waves and electromagnetic waves. According to different application fields and requirements, absorbing materials can be divided into acoustic absorbing materials, electromagnetic absorbing materials, etc. Common acoustic absorbing materials include sponge absorbing materials, cotton sound-absorbing materials, glass fiber sound-absorbing panels, porous metal materials, etc; And electromagnetic absorbing materials includeConductive foam materialFerrite materialsComposite absorbing materialWait. Absorbing materials are widely used in aerospace, automotive, building, electronic equipment and other fields where noise, vibration or electromagnetic radiation needs to be controlled.

1. The absorber used in the microwave anechoic chamber is often made into a wedge shape (golden tower shape), mainly composed of polyurethane foam type, non-woven flame retardant type, silicate plate metal film assembly type, etc. As the frequency decreases (wavelength increases), the length of the absorber also greatly increases. The approximate relationship between a common sharp edged absorber and L/λ ≈ 1 is that at 100MHz, the sharp edged absorber can reach a length of 3000mm, which is not only difficult to achieve in the process, but also greatly reduces the effective available space in the microwave anechoic chamber.

2. Single layer flat plate shape, the earliest absorbent body developed abroad is the single-layer flat plate shape. Later absorbent bodies are directly attached to the metal shielding layer, with thin thickness and light weight, but a narrow operating frequency range.

3. Double or multi-layer flat plate shaped absorbers can operate over a wide frequency range and can be made into any shape. Uniformly dispersing ferrite and metal short fibers in a suitable organic polymer resin to make composite materials can broaden the working frequency band by 40% to 50%. Its disadvantages are large thickness, complex process, and high cost.

4. Coating form, can only be used on the surface of aircraftCoating type absorbent materialTo broaden the frequency band, composite material coatings are generally used. When the thickness of the lithium cadmium ferrite coating is between 2.5mm and 5mm, it can attenuate by 8.5dB in the centimeter wavelength range; When the thickness of spinel ferrite coating is 2.5mm, it can attenuate by 24dB at 9GHz; When the thickness of the ferrite chloroprene rubber coating is between 1.7mm and 2.5mm, the attenuation reaches about 30dB at 5GHz to 10GHz.

5. One direction for the development of absorbing materials is to incorporate absorbing materials into engineering plastics to give them both absorption properties and load-bearing capacity. Nowadays, in order to further improve the performance of absorbing materials, several complex absorbers with shape combinations have been developed abroad.

Application of absorbing materials

1. Can be used inside electronic device cavities such as laptops, mobile phones, and communication cabinets.

2. It can reduce the radiation and noise of various electronic devices.

3. Can reduce coupling, conduction, and radiation interference between low frequencies, as well as minimize low-frequency echo interference

4. Can reduce internal EMI (resonance, crosstalk) within the barrier frame.

5. Applied between chips and heat dissipation modules.

6. Application of EMI/RFI: Three elements of electromagnetic interference: interference source, interference propagation path, and sensitive equipment. Interference sources refer to electronic devices or systems that generate electromagnetic interference, which can propagate through cables, space, etc. Sensitive devices refer to electronic devices or systems that are easily affected by electromagnetic interference.
RF Interference: Radio frequency is a high-frequency alternating current, commonly known as electromagnetic waves. Radio frequency interference is the interference caused by electromagnetic waves. If two electromagnetic waves with similar frequencies are simultaneously received by the receiver, it will cause interference. There will be harmonic interference near the transmitter. Interference with other receiving devices. Electromagnetic waves at the same frequency can interfere with radio stations.
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