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Talk about the application and prospect of nanocrystalline soft magnetic alloy materials in wireless charging

by:Catech      2023-04-14

Compared with cobalt-based amorphous and ferrite, nanocrystalline has high saturation magnetic induction and can reduce the volume of magnetic devices. High magnetic permeability, low loss, and low coercive force can reduce the loss of magnetic devices. Therefore, nanocrystalline alloys are the best soft magnetic materials for high-frequency power electronics applications.

Properties of Nanocrystalline Alloys

The frequency of the current wireless charging Qi standard is between 100-200k. At this frequency, the magnetic permeability of nanocrystals is very close to that of cobalt-based amorphous, which is significantly higher than that of iron-based amorphous and ferrite. The loss is just the opposite, significantly lower than that of iron-based amorphous and ferrite. Nanocrystals also have advantages in temperature application. Nanocrystals not only have a wider application temperature than cobalt-based amorphous and ferrite, but also have significantly better stability than ferrite in the range of -40°C-120°C. body. Nanocrystals also have obvious advantages in the design of magnetic materials. Nanocrystals can directional control magnetic permeability and anti-saturation magnetic field. The magnetic permeability of nanocrystals can be adjusted freely within 1000-30000. The design of magnetic materials requires not to reach magnetic saturation under a specific working current. Once magnetic saturation is reached, it will stop working. The adjustable anti-saturation magnetic field of nanocrystals can reach 30~350A/m, making the application range of wireless charging wider. Width.

Comparison of several iron-based nanocrystals with iron-based amorphous, cobalt-based amorphous, and ferrite: saturation magnetic flux density: iron-based nanocrystals are obviously better than cobalt-based Amorphous and ferrite; nanocrystalline is better than other materials in terms of coercive force, initial permeability, saturation magnetostriction coefficient, Curie temperature, performance change rate, etc. Therefore, nanocrystalline is the best soft magnetic Material.

The development trend of nanocrystal

With the development of electronic products in the direction of high frequency, energy saving, small size and integration, the frequency of application is also increasing, and the strip materials are updated from generation to generation. From the initial traditional tape-making process (current production level in China) with a thickness of 22-30 μm, the strip material has developed to the third and fourth generations, and the advanced tape-making process (international advanced production level) can achieve 14-22 μm. And mastered the thinner belt technology. The development trend of nanocrystalline ribbon is ultra-thin ribbon. Ultra-thin nanocrystalline ribbon characteristics: the thinner the ribbon, the lower the loss. The batch production process of magnetic conductive sheet has changed. Since the batch production of magnetic conductive sheet in 2015, the process has been continuously changed, and the sheet material has gradually transitioned to coiled material, which has greatly improved production efficiency and met the growing demand.

Wireless charging has become popular in mobile phones, and there are many products in the wearable field. In the future, wireless charging will be popularized in homes, offices, public places, travel tools, and transportation, and electric vehicles will also be popularized in the future.

Wireless Power Transfer (WPT): The structure of wireless charging for smartphones and smart wearables (low power) is similar to a transformer, consisting of a transmitter and a receiver. Both the transmitter and receiver are made of coils and magnetic materials. The magnetic materials are different. The choice of ferrite, amorphous, nanocrystalline and so on.

The role of soft magnetic shielding materials in wireless charging

Magnetic isolation shielding: Provide a low impedance path for magnetic flux, reduce the magnetic field lines emitted outward, reduce the impact on surrounding metal objects, and prevent eddy currents and signal interference.

Magnetic conductivity and resistance reduction: increase the coupling coefficient, improve the magnetoelectric conversion efficiency, use fewer turns to achieve higher inductance coils, reduce coil resistance, and reduce the efficiency reduction caused by heat generation (the more turns, the higher the resistance) .


The application of nanocrystals in wireless charging started from S7, a material for all functions, replacing the combination of amorphous and ferrite. It is generally believed that the soft magnetic material used for NFC, ferrite is Zj, and nanocrystalline is not suitable, because at high frequencies, the loss of nanocrystalline is much greater than that of ferrite, but Samsung just made a breakthrough, the success of S7 The application proved that nanocrystals can be used in NFC, and the subsequent S8/N8/A7/J5/J7 and many other models extended the application of nanocrystals from WPC to NFC and MST. Antai Technology, a representative company of China's nanocrystalline production, has also made some attempts at the launch end. It has made several wireless charger products with nanocrystalline magnetic sheets. They have multi-station, multi-functional and other special products. There is no problem in performance. Now the only The problem with y is that the cost of the magnetic sheet is higher than that of the ferrite.

The development trend of magnetic sheet:

Receiver: absorbing material → ferrite → amorphous + ferrite → nanocrystalline

Nanocrystalline magnetic sheet:

Thin—ultra-thin: 0.14→0.12→0.11→0.10

High magnetic permeability, low loss - high Q

Application and popularization:

Low power: mobile phones, smart wearables, etc.

Medium power: computers, kitchen appliances, etc.

High power: electric vehicles, roads and other infrastructure

In the future, there will be a wireless world, changing life and changing the world.

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