The Advantageous   

One of the primary advantages of nanocrystalline soft magnetic shielding materials is their high permeability, which enables effective suppression of electromagnetic interference (EMI) and minimizes energy losses during wireless charging processes. 

Compared with conventional soft magnetic ferrite materials, nanocrystalline soft magnetic shielding materials can achieve the same shielding performance with extremely thin thickness，even the half thickness of ferrite because of their high Bs.  As FIg.1 shows that under the same condition, the thickness of nanocrystalline shielding sheets (0.10mm) is half of that ferrite (0.21mm) to achieve the same efficiency, or even better.

The high saturation flux density and high permeability make it have great advantageous over other soft magnetic shielding materials when applied to various electronic devices with limited space.

Moreover, their excellent frequency response characteristics make them suitable for use in the wide range of frequencies encountered in wireless charging systems. For example, the well-known Qi standard with 110-360kHz established by WPC, and the magnetic resonance standard with 6.78MHz established by Airfuel.

In addition, nanocrystalline soft magnetic shielding materials possess excellent thermal stability and mechanical strength, ensuring long-term reliability under extreme conditions, which is most suitable for EV wireless charging.

   The Mechanism   

Inductive charging (also known as "wireless charging") uses an electromagnetic field to transfer energy between two objects, which can be called transmitter and receiver. Energy is sent through an inductive coupling to an electrical device, which can then use that energy to charge batteries or run the device.

The transmitter and receiver are similar in structure, with coils and shielding components. What is the role of shielding components in wireless charging? Due to one of the challenges faced by wireless charging systems is the interference caused by electromagnetic fields, this interference can affect the charging efficiency and performance of wireless charging devices, leading to slower charging rates or even wreck the device. Shielding materials play a crucial role in mitigating these electromagnetic interferences. It can be summarized from two aspects: on the one hand, from the perspective view of the impact on the surroundings, soft magnetic shielding materials play a role in isolating and shielding magnetic interference, inhibiting the induced magnetic field from emanating outwards, thereby reducing the influence on the surrounding metallic components, and preventing eddy current and signal interference. On the other hand, from the perspective view of the internal effect, the soft magnetic shielding material play the role of improving magnetic conduction and reducing reluctance：that is, improving the coupling coefficient and the magneto-electric conversion efficiency. Because higher inductance can be achieved by using fewer turns of coils to reduce the efficiency loss caused by heat generation (The more turns, the higher the resistance, the greater the heat).

   The Process   

Nanocrystalline soft magnetic shielding materials use as-cast amorphous ribbons or annealed nanocrystalline ribbons as the shielding functional material, and by alternating with ultra-thin double-sided adhesive laminated into a variety of thickness of magnetic shielding tapes or subsequent die cut to any shape of customized sheets. 

Because the nanocrystalline ribbon will produce eddy currents at high frequencies, even if it is very thin, the eddy current losses are still high when it is used for wireless charging, thus increasing the temperature of the component. The effective way to solve this problem is to crack the nanocrystalline ribbon into tiny pieces, thereby substantial reducing the magnetic losses μ” from more than 10,000 to several hundred levels at 100kHz. The typical mass production process of nanocrystalline soft magnetic shielding materials for wireless charging is as Fig.2 shows: 

In some cases, such as pure magnetic shielding applications or seeking better shielding effects, and without consideration of temperature rise, the nanocrystalline ribbon does not need to be broken into tiny pieces, so the cracking process can be omitted. Similarly, if one layer is sufficient, the multilayer laminating process can also be omitted.

   The Application   

One prominent application of nanocrystalline soft magnetic shielding materials in wireless charging is the design and manufacturing of compact and lightweight wireless charging receiving moduls or transmitting modules, which makes them very popular and widely used in consumer electronic devices, such as smart mobile phones, smart bracelets, Bluetooth earphones, VR glasses, tablets, laptops, electric toothbrushes, and other low-power electronic devices. At present, it is expanding to medium and large-power electronic equipment such as floor-cleaning robots, hotel service robots, sorting robots, industrial robots, kitchen equipment, drones, electric vehicles etc.

As high-class smart phone come with wireless charging as standard, the infrastructure for wireless charging has also developed rapidly in recent years. More and more places have the wireless charging transmitter, so we can enjoy convenient wireless charging functions from home or workplace to public places such as cafes, restaurants, cinemas, shopping malls, train stations, and airport terminals. We can also enjoy wireless charging service while traveling, such as in the car, on the high-speed railway, even on the plane. A wireless charging ecosystem where all human activities from home to workplace can be charged wirelessly is being built and gradually formed.

   The Trend   

With people's awareness of wireless charging and gradually adapt to wireless charging, people's requirements for wireless charging speed are getting higher and higher. And the wireless charging power of smart phones has gradually increased, from the initial 5W to 7.5w, 10w, 15w. Subsequently, with the competition between Huawei and Xiaomi in wireless charging technology, wireless charging technology has entered a period of rapid development, and wireless charging has changed from normal charging mode to reverse-charging mode, to fast charging mode, and then to super-fast charging mode. The corresponding power is also escalating to 27w, 30w, 36w, 40w, and 50w in just two years. The next wireless charging power level is 80w, which is the upper limit standard that the Ministry of Industry and Information Technology, PRC has just relaxed in 2023. Perhaps in the near future, the wireless flash charging that can be fully charged with a few minutes will become a reality.  

With the development of wireless charging technology, the matching shielding material has also changed from the initial hard MnZn ferrite to flexible MnZn ferrite, to Fe-based amorphous, and finally to Fe-based nanocrystalline. Fe-based nanocrystalline are the best soft magnetic shielding materials for wireless charging receivers at present. 

In order to make the wireless charging module thinner, more efficient and more anti-interference, the Fe-based nanocrystalline material itself also needs to be continuously improved. The development trend of nanocrystalline ribbon for wireless charging is towards ultra-thin thickness and high Bs. In terms of thickness, nanocrystalline ribbons with a thickness of 18~20μm have been widely used, and nanocrystalline ribbons with a thickness of 12~16μm are very promising candidate materials in the future, because the thinner the thickness, the smaller eddy current losses. At present, the thinnest nanocrystalline ribbon produced by Foresee or AT&M has reached 12 μm, which is the highest level in mass production in the world. In terms of anti-DC bias, the Bs=1.4T nanocrystalline ribbons have been commercialized, partially replacing the Bs=1.2T nanocrystalline ribbons, in which the shielding sheet of 3 layers Fe-based nanocrystalline ribbon can resist DC superimposed up to 4.5A, and will be higher in the future, which is more secure and stable for wireless charging systems.

Another prospecting development trend of wireless charging is magnetic resonance, which can make the charging distance longer, can charge multiple devices at the same time, and there are no strict restrictions on the charging location. If the charging efficiency of magnetic resonance can be further improved and the potential risks to human health can be eliminated, wireless charging will be experienced more exciting and be more popular.

   Outlook   

Nanocrystalline soft magnetic shielding materials have promoted the wide application of wireless charging technology in small and medium-sized power electrical and electronic equipment receivers, making electronic equipment to a more simplified, more convenient, and more intelligent direction. Taking smart phones as an example, future mobile phones will remove any port, at that time, there is no need any annoying cables, you can put your phone into water without any damage. 

The implications of nanocrystalline soft magnetic shielding materials extend to various industries. The integration of these advanced materials into wireless charging infrastructure can enable faster and more convenient charging options, thus making electric vehicle more widespread and promoting energy conservation and environmental protection. 

 One day in the future, with the popularity of wireless charging and the maturity of driverless technology for electric vehicles, urban infrastructure such as wireless charging roads will also undergo profound changes. Considering the successful popularization of cashless payment in China, driverless driving and wireless charging will eventually be fully realized as well. Build a wireless charging ecosystem, enter the wireless era, and enjoy a better and more convenient life. 

For more information about Nanocrystalline soft magnetic shielding materials, please feel free to contact us.

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