The high permeability of shallow of absorbing materials plant absorbing material application
First of all, let's understand what constitutes a high permeability absorbing material: A high permeability absorbing material refers to a kind of absorbing material with a high permeability real part U '(generally ≥50) around 10MHz.
High permeability wave-absorbing materials can be divided into the following two categories according to their application fields:
1. High permeability wave-absorbing materials for EMC/EMI solutions
This kind of absorbing material not only needs high real part of permeability U ', but also hopes to have high imaginary part of permeability U "(commonly known as" high magnetic loss ").
Main principle analysis:
A higher real part of permeability can increase the magnetic flux of the cluster interference source, while a higher imaginary part of permeability can effectively convert the magnetic flux of the cluster into latent heat, thus reducing or eliminating the electromagnetic radiation interference harm of the interference source.
2. It is used to provide RFID/NFC resistance against metal interference at 13.56mhz and below
This kind of absorbing material hopes to have a lower imaginary part of permeability U "(commonly known as" low magnetic loss ") while it needs a higher real part of permeability U ', that is, it hopes to have a higher quality factor (U '/ U ").
Main principle analysis: high magnetic permeability cluster communication antenna real can be more of the signals of magnetic flux, so as to effectively reduce or eliminate the line close to the metal when the phenomenon of metal eddy current, at the same time, low permeability imaginary part u "without too much loss of signal energy, through which guarantee the communication identification response and effective identification of distance.
At present, in the application of RFID/NFC against metal interference, absorbing materials can only provide solutions for RFID/NFC of 13.56MHz and below. The reason is that when the permeability of general absorbing materials is over 10 MHz, the real part of its permeability U 'will decay rapidly, while the imaginary part of its permeability U "will rise rapidly. With high magnetic permeability real u ', low permeability imaginary part u "characteristics of absorbing material under 13.56 MHz and frequency RFID/NFC metal interference provide solutions at the same time, as a result of absorbing material insert changed the line capacitance, antenna impedance and the distance between the antenna and the metal base plate (increase) and dielectric constant, and this could lead to a card reader or tag antenna resonant frequency offset and influence the actual effect of communication, so the company technical personnel must understand their relevant properties of absorbing materials system, to guide the customer right adjust the antenna resonant frequency in order to achieve the best communication effect. It can be seen that the application of absorbing materials in EMC/EMI or RFID/NFC will have more or less other influences on the whole system of application objects. In order to improve the market competitiveness, in addition to the quality of products, relevant application research must be strengthened to provide "close" services for customers.
In addition, in the application of ELECTROMAGNETIC induction wireless charger with Qi standard by WPC (Wireless Charging Alliance), its requirements and principles of absorbing materials are similar to the above mentioned.
At present, there are also two main types of absorbing materials in this application field:
1) Ferrite hard plate absorbing material
Ferrite hard plate absorbing material has relatively higher real part of permeability U '(up to about 200) and smaller virtual part of permeability U ", with superior application performance. At present, only sintering process can be used to prepare the products to achieve superior magnetic permeability. In order to reduce the negative impact of this process on its mechanical properties, the size of the products is limited (generally no more than 125mm×125mm), so there is a large loss in the processing of the products. At the same time, due to its high brittleness, high requirements for processing and preparation equipment, the rejection rate is also high, in addition, in the process of processing, storage and transportation of products or products are easy to produce cracks, causing magnetic leakage, the actual performance is also affected, so the market acceptance is not too high.
2) Soft magnetic alloy flexible absorbing material
The magnetic conductivity of soft magnetic alloy flexible absorbing material is weaker than that of ferrite hard sheet, but its flexible size can meet the low loss of product processing, good product processing performance can reduce the rejection rate and processing costs, so the market demand is not low.
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