First of all, let's understand what is high permeability absorbing material: high permeability absorbing material refers to a kind of absorbing material with high permeability real part u '(generally ≥ 50) at about 10MHz.
High permeability absorbing materials can be divided into two categories according to their application fields
1. High permeability absorbing materials for EMC / EMI solutions
This kind of absorbing materials not only need high permeability real part u ', but also want high permeability imaginary part U "(commonly known as" high magnetic loss ").
Main principle analysis:
The higher permeability real part can increase the magnetic flux of the cluster interference source, and the higher permeability imaginary part can effectively convert the cluster magnetic flux into latent heat consumption, so as to reduce or eliminate the electromagnetic radiation interference harm of the interference source.
2. It is used to provide anti metal interference for RFID / NFC with frequency of 13.56MHz and below
This kind of absorbing material needs high permeability real part u ′ and low permeability imaginary part u ″ (commonly known as "low magnetic loss"), i.e. high quality factor (U ′ / u ″).
Main principle analysis: the higher permeability real part can increase the magnetic flux of the cluster communication antenna signal, so as to effectively reduce or eliminate the "metal eddy current" phenomenon when the antenna is close to the metal. At the same time, the low permeability imaginary part U "will not cause too much loss of the communication signal energy, so as to ensure the response of communication recognition and effective recognition distance.
At present, in the application of anti metal interference of RFID / NFC, absorbing materials can only provide solutions for RFID / NFC with frequencies of 13.56 MHz and below. The reason is that when the permeability of general absorbing materials is more than 10 MHz, the real part u 'of permeability will decay rapidly, while the imaginary part U "of permeability will rise rapidly. The microwave absorbing materials with high permeability real part u ′, low permeability imaginary part u ″ can provide solutions for RFID / NFC with frequency of 13.56 MHz and below. Meanwhile, the insertion of absorbing materials changes the capacitance and impedance between the antenna and the metal substrate (increase) and dielectric constant, which may lead to the resonance of the reader or tag antenna The frequency deviation will affect the actual communication effect, so the company's technical personnel must understand the relevant characteristics of their own absorbing material system, so as to guide customers to adjust the antenna resonance frequency correctly 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 impacts on the whole system of application objects. In order to improve the market competitiveness, in addition to the quality of products, we must strengthen the relevant application research and provide "personal" services for customers.
In addition, in the application of WPC (wireless charging alliance) electromagnetic induction wireless charger adopting Qi standard, the requirements and principles of absorbing materials are similar to those mentioned above.
At present, there are two kinds of absorbing materials in this field
1) Hard ferrite absorbing materials
The hard ferrite absorbing materials have relatively higher permeability real part u '(up to about 200) and smaller imaginary part u ″, so the application performance is superior. At present, only sintering process can be used to achieve superior permeability performance. In order to reduce the negative impact of the process on its mechanical properties, the product size is limited (generally not more than 125mm × 125mm), so the loss is large when processing products. At the same time, due to its high brittleness, high requirements for processing and preparation equipment, and high scrap rate, in addition, the products or products in the process of processing, storage and transportation are easy to produce cracks, resulting in magnetic flux leakage, and the actual performance is also affected, so the market acceptance is not very high.
2) Soft magnetic alloy flexible absorbing material
The permeability 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, and good processing performance can reduce the scrap rate and processing cost, so the market demand is not low.
Absorbing material: www.goodsmaterial.com