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Brief introduction of high permeability absorbing materials

2021-02-07 41
High-permeability absorbing materials refer to a class of absorbing materials with high magnetic permeability real part u'(generally ≥50) around 10MHz. In terms of its magnetic permeability characteristics, high permeability absorbing materials can be roughly divided into two categories due to their application fields, that is, the different problems they solve:

1. The high permeability absorbing materials used to provide EMC/EMI solutions not only require a higher real part u′ of permeability, but also a higher imaginary part u″ (commonly known as “high magnetic permeability”). Analysis principle: the higher the real part of the permeability can increase the magnetic flux of the interference source, and the higher the imaginary part of the permeability can effectively convert the concentrated magnetic flux into latent heat and consume it, thereby reducing or Eliminate the electromagnetic radiation interference hazards of interference sources. According to the data analysis currently available to marketers, the higher the magnetic permeability of the absorbing material that meets this characteristic, the better the relatively low frequency absorption effect, and the more effective the absorption frequency width.


Brief introduction of high permeability absorbing materials


2. High permeability absorbing materials used to provide RFID/NFC anti-metal interference solutions at frequencies of 13.56MHz and below. While a higher real part u'of permeability is required, it is hoped to have a lower permeability The imaginary part u" (commonly known as "low magnetic loss"), that is, hope to have a higher quality factor (u'/u"). Analysis of the principle: the higher the real part of the magnetic permeability can more bundle the magnetic flux of the communication antenna signal, thereby effectively reducing or eliminating the "metal eddy current" phenomenon generated when the antenna is close to the metal, and the lower magnetic permeability The part u" will not excessively lose the energy of the communication signal passing through, ensuring the response of communication identification and the effective identification distance. At present, in the application of RFID/NFC anti-metal interference, the absorbing material can only be 13.56MHz and below Frequency RFID/NFC provides a solution. The reason: when the permeability of general absorbing materials is more than 10 MHz, the real part u′ of the permeability will rapidly decay, while the imaginary part u″ of the permeability will rise rapidly .

Absorbing materials with the characteristics of high permeability real part u'and low permeability imaginary part u” provide solutions for RFID/NFC anti-metal interference at 13.56MHz and below. At the same time, due to the change of the insertion of the absorber material The antenna’s line capacitance, impedance, and the distance (increase) and dielectric constant between the antenna and the metal base plate may cause the resonant frequency of the card reader or tag antenna to shift and affect the actual communication effect. Technicians must understand the relevant characteristics of their own absorbing material system to guide customers to adjust the antenna resonance frequency correctly to achieve the best communication effect. It can be seen that the absorbing material is not in EMC/EMI or RFID/NFC The application of this product will have more or less other impacts on the entire system of the application object. In order to improve market competitiveness, in addition to the quality of the product itself, it is necessary to strengthen related application research and provide customers with "personal" services.

In addition, in the application of WPC (Wireless Power Consortium) adopting Qi standard electromagnetic induction wireless charger, its requirements and principles for absorbing materials are similar to the above.

At present, there are two main types of absorbing materials in this application field: hard ferrite absorbing materials and soft magnetic alloy flexible absorbing materials. From the perspective of market applications, almost half of them are accounted for.

The ferrite hard plate absorbing material has a relatively higher real part of magnetic permeability u'(up to about 200), a smaller imaginary part u” of magnetic permeability, and superior application performance. At present, it can only be prepared by sintering process. To achieve superior permeability performance, and in order to reduce the negative impact of the process on its mechanical properties, the product size is limited (generally no more than 125mm × 125mm), so the loss of processing products is large. At the same time, because of its high brittleness, The equipment required for processing and preparation is high, and the scrap rate is also high. In addition, the products or products are prone to cracks during processing and storage and transportation, causing magnetic flux leakage, and the actual performance is also affected, so the market acceptance is not very high.

The magnetic permeability performance of soft magnetic alloy flexible absorbing material is weaker than ferrite hard piece, but its flexible size can meet the low loss of product processing, and good product processing performance can reduce the scrap rate and processing cost, so the market The demand is not low.
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