As the performance and functionality of electronic devices increase, the amount of heat generated by each device increases, and it is important to efficiently emit, dissipate, and cool the heat. For high-performance mobile products such as 5G smartphones and AR/VR devices, the use of high-performance ICs and highly integrated designs that seek to reduce weight result in limited mounting space for heat dissipation components. Limiting the mounting space inside the case, TIM technology solutions such as highly thermally conductive spacers are utilized to better achieve heat dissipation.
NFC absorber refers to a class of materials that can absorb or significantly attenuate the electromagnetic wave energy received on its surface, thus reducing the interference of electromagnetic waves. In engineering applications, in addition to the requirements of the NFC absorber in a wide band of electromagnetic waves with high absorption rate, but also requires it to have a light weight, temperature, moisture, corrosion resistance and other properties.
With the development of modern science and technology, the impact of electromagnetic radiation on the environment is increasing. In the airport, flights can not take off due to electromagnetic interference and missed; in hospitals, cell phones often interfere with the normal work of a variety of electronic diagnostic and therapeutic instruments. Therefore, the treatment of electromagnetic pollution, looking for a material that can resist and weaken electromagnetic radiation – wave-absorbing materials, has become a major issue in materials science. Electromagnetic radiation causes direct and indirect harm to human body through thermal effect, non-thermal effect and cumulative effect. Research has confirmed that the ferrite wave-absorbing material has the best performance, which is characterized by high absorption band, high absorption rate and thin matching thickness. The application of this material in electronic equipment can absorb the leaked electromagnetic radiation, can achieve the purpose of eliminating electromagnetic interference. According to the law of electromagnetic wave propagation in the medium from low magnetic direction to high magnetic permeability direction, the use of high permeability ferrite to guide the electromagnetic wave, through the resonance, a large number of electromagnetic wave absorption of radiant energy, and then through the coupling of electromagnetic wave energy into thermal energy. Wave-absorbing materials in the design, to consider two issues, 1), electromagnetic waves encountered on the surface of the wave-absorbing material, as far as possible, completely through the surface to reduce reflection; 2), in the electromagnetic wave into the wave-absorbing material, to make the electromagnetic wave energy loss as far as possible.
Electronic products will radiate electromagnetic waves of different frequencies and wavelengths when they are working, which can easily cause interference to the neighboring circuits and equipments, resulting in accidents such as information transmission errors, control failures, and electromagnetic pollution to the environment. Such as causing the airplane can not take off on time, hospital electronic diagnostic and treatment instruments can not work properly. At present, NFC absorber is one of the application materials to solve the electromagnetic pollution, NFC absorber can not only absorb part of the electromagnetic wave, but also has the characteristics of light weight, moisture resistance, high temperature resistance, corrosion resistance and so on.
Two conditions for good absorption of NFC absorber materials
- The ability of an incident electromagnetic wave to fully penetrate into a material without reflecting off the surface, i.e., the matching properties of the material.
- Electromagnetic waves entering the interior of the material can be rapidly attenuated away. Satisfy condition 1) of the method between the free impedance. Is the use of special boundary conditions to achieve the input impedance of the material and the empty part, the inter-wave impedance matching, that is, the reflection coefficient R = 0, the current absorber can. It is difficult to satisfy this condition; while the method to satisfy condition 2) is to make the material has a large electromagnetic loss.
In practice, these two requirements are usually contradictory, and also requires NFC absorber absorption bandwidth, excellent mechanical properties and easy to construct and other characteristics, and therefore in the design of wave-absorbing materials must be optimized for the thickness, electromagnetic parameters and structure. General selection of multi-layer structure, so that the impedance of each layer of the material from the surface to the bottom of the lower layer, so that both the input impedance of the material and the spatial wave impedance matching, to guide the electromagnetic wave into the material inside, but also through the adjustment of the electromagnetic parameters of the material to achieve the absorption of electromagnetic waves.
Incident electromagnetic wave to maximize the entry into the material inside, rather than on its surface on the reflection, that is, to meet the material’s impedance matching; into the material inside the electromagnetic wave can almost all be attenuated, that is, attenuation matching. Attenuation matching can be resistive loss, electromagnetic energy into thermal energy; can also be dielectric loss, through the dielectric polarization of electromagnetic energy into thermal energy; can also be magnetic loss, into hysteresis loss, damping loss and so on. Therefore, a good wave-absorbing material hardly reflects electromagnetic waves, but absorbs them internally and attenuates them all.
Characteristics of NFC absorbers
NFC absorber refers to a class of materials that can absorb electromagnetic wave energy projected onto its surface, through a variety of different loss mechanisms of the material, the incident electromagnetic wave into heat or other forms of energy, and to achieve the purpose of absorbing electromagnetic waves. In engineering applications, in addition to the requirements of wave-absorbing materials in a wider frequency band, the electromagnetic wave has a high absorption rate, but also requires temperature resistance, moisture resistance, light weight, corrosion resistance and other properties. Wave-absorbing materials absorb wave effect is determined by a variety of electromagnetic mechanisms within the medium, such as: the resonance of the dielectric absorption, electron diffusion, micro-vortex and so on.
- Soft and unbreakable, light and thin, easy to process and cut, easy to use, can be installed in small spaces.
- The product needs to be bonded or pressed onto a metal substrate to achieve good wave absorption.
- Products are available in a wide range of sizes and shapes.
- High temperature resistance and good flexibility.
- Halogen-free, lead-free, meets RoHs directive.
- Can be used as a noise countermeasure for flexible cables for mobile devices. (Laptop computers, game consoles, cellular phones, etc.)
- Reduces radiated noise from various electronic devices. (CPU-generated noise, etc.)
- Reduces electromagnetic radiation (SAR) from cell phones to the human body.
- Reduces internal EMI (resonance, crosstalk) within the shielded frame.
- Reduction of coupled conduction radiation interference between low frequencies, reduction of low-frequency echo interference.
NFC absorber applications
- Can be used inside the cavities of electronic devices such as laptops, cell phones, and communication cabinets.
- Can be used to reduce radiation and noise from various electronic devices.
- Reduces interference from low-frequency coupled conduction radiation and low-frequency echo interference.
- Reduces internal EMI (resonance, crosstalk) within the barrier frame.
- Applied between the chip and the heat sink module.
- Application of EMI/RFI: EMI (Electro MagneTIc Interference): Translated as electromagnetic wave interference. Electromagnetic interference three elements: interference source, interference propagation path and sensitive equipment. The source of the interference refers to the generation of electromagnetic interference of electronic equipment or systems, interference propagation pathways, including cables, space, etc., sensitive equipment is susceptible to the impact of electromagnetic interference of electronic equipment or systems. Transmit frequency interference (RF Interference): radio frequency is a high-frequency alternating current, which is usually referred to as electromagnetic waves. RF Interference is the interference caused by electromagnetic waves. For example, two electromagnetic waves of similar frequency will be received by the receiver at the same time causing interference. There will be harmonic interference in the place close to the sending station. Interference with other receiving equipment. Electromagnetic waves at the same frequency can interfere with a radio station.
Difference between NFC absorber and shielding material
Shielding material is capable of isolation of metal between two space regions, magnetic fields, electromagnetic waves, to control the electric field, by one region to another region of induction and radiation of a class of materials. Specifically the materials used to create the shielding body. Shielding body will be meta-components, circuits, assemblies, cables, or the entire system of interference sources surrounded, to prevent interference electromagnetic fields to the outside, with the shielding body will receive the circuit, equipment or system wrapped up, to prevent the impact of external electromagnetic fields. Wave-absorbing materials electromagnetic waves in and out, but electromagnetic shielding materials are not necessarily reflecting electromagnetic waves away, but by either absorbing or reflecting, so that the amount of electromagnetic waves to reach the other side of the shielding material is reduced. It can be said that the NFC absorber is to make the same side of the absorbing material and electromagnetic wave source, as little as possible to receive the electromagnetic wave reflected back, and electromagnetic shielding material is for shielding material and make the electromagnetic wave source on the other side of the electromagnetic wave source, as little as possible to receive the impact of electromagnetic waves. The electronics industry is changing rapidly, which brings a lot of challenges for material programmers. In 5G, automotive electronics, automatic driving, drones, AI, AR/VR and other trends, electronic products will continue to iterate and update, the chip’s arithmetic requirements are higher, facing increased power consumption, radiation, heat dissipation and other issues, which puts forward higher requirements for the development of high-end materials and technology to quickly correspond to the technical support.