Wireless charging receiver magnetic separator | When magnetic lines encounter the "highway" - an invisible upgrade from charging heat to high efficiency and insensitivity

1、 Why does wireless charging on your phone get hot? The problem isn't with the charger, it's with 'magnetic leakage'

Wireless charging relies on electromagnetic induction - the transmitting coil generates an alternating magnetic field, and the receiving coil induces current. The principle sounds simple, but in reality, magnetic fields do not obey. It will spread outwards in a divergent manner, rather than obediently running from one coil to another. Experimental data shows that only 50% -75% of the power in the unshielded design system can be effectively captured by the receiving end.

When this part of the "leakage flux" encounters the metal back panel, battery case, or circuit board of the mobile phone, induced eddy currents will be generated inside the metal. There are two consequences of eddy currents: energy waste - electricity that should have been sent to the battery is lost as heat energy halfway through; Thermal hazard - eddy currents cause metal parts to heat up, which is the fundamental reason why many users complain about "phones overheating during wireless charging".

The significance of the existence of magnetic separators is to point out a "clear path" for magnetic field lines. Attach it between the coil and the metal component, and the magnetic field lines prefer to follow this low magnetic resistance path, closing the loop inside the magnetic separator and no longer penetrating the metal layer behind. There is no longer any movement of cutting magnetic lines in the metal, and eddy current heating is effectively suppressed. Nanocrystalline magnetic separators can effectively reduce energy loss, heat generation, and electromagnetic interference to the surrounding environment during wireless charging.

2、 Nanocrystals vs Ferrites: Why High end Wireless Charging is Changing Materials

The material selection of the magnetic separator directly determines the charging efficiency and temperature control performance. The current industry is undergoing a generational transition from ferrite to nanocrystals.

The traditional ferrite magnetic separator was the earliest solution. But the loss of ferrite increases sharply in the high frequency range above 100kHz, and the operating frequency of mainstream wireless fast charging protocols (such as Qi 1.3 and AirFuel) falls precisely in this range. Ferrite also has a hard flaw - it is hard, brittle, and prone to cracking, making it difficult to achieve ultra-thin properties.

Nanocrystalline materials are technological disruptors. Nanocrystalline alloys represented by Fe-Si-B series can maintain a magnetic permeability of over 80% at a frequency of 1MHz. At the Qi standard frequency (100-200kHz), the magnetic permeability of nanocrystalline separators is significantly higher than that of ferrites, while the loss is exactly the opposite - significantly lower than that of ferrites.

More importantly, the thickness. The thickness of ferrite magnetic sheets is usually above 0.2mm, while the thickness difference of nanocrystalline magnetic separators can be as low as 30 μ m. In the precious space inside a mobile phone, this thickness difference of over 0.1mm may be the key to battery expansion or body thinning. Within the temperature range of -40 ℃ to 120 ℃, the stability of nanocrystalline magnetic separators is significantly better than that of ferrites.

The global market sales of nanocrystalline noise suppression chips have reached $180 million by 2025 and are expected to grow to $329 million by 2032. The global production of nanocrystalline noise suppression films has reached 1.5 million square meters. Nanocrystals are gradually replacing traditional ferrite magnets with their three major advantages of high magnetic permeability, low loss, and thinning, becoming wireless charging modules NFC/RFID、 Important functional materials for power management systems and automotive electronics.

3、 Data Speaking: What can a nanocrystalline magnetic separator change?

The performance of the magnetic separator in wireless charging receivers ultimately needs to be answered with data.

Magnetic permeability determines the ability to guide magnetic field lines. The magnetic permeability of nanocrystalline magnetic separators can reach 500-1000. Laird's nanocrystalline shielding sheet has an initial magnetic permeability of up to 1400 μ i at 128KHz. High magnetic permeability means achieving more efficient magnetic flux guidance at thinner thicknesses.

Thickness is the most intuitive advantage of magnetic separators. The effective thickness of the nanocrystalline magnetic separator can be as thin as 0.06mm ± 10%. The total thickness of ultra-thin nanocrystalline magnetic separators can be controlled within 80 μ m, achieving a charging efficiency of not less than 75% on a 5W charging efficiency testing platform. This thickness is sufficient to fit into the narrow space between the phone back cover and the battery.

Temperature rise control is a direct reflection of user experience. The actual test data of a flagship mobile phone with a wireless charger from a certain brand shows that after being equipped with a nano crystal shielding sheet, the temperature rise of the coil under full load operation is reduced by 12 ℃, and the charging speed is increased by 25% year-on-year.

The coupling efficiency has also significantly improved. Experiments have shown that the coupling coefficient (k value) of coils equipped with nanocrystalline shielding sheets can reach 0.35-0.45, which is more than 40% higher than ordinary designs. When the magnetic permeability of ferrite and nanocrystalline material are both 600 and the thickness is 0.11mm, the efficiency of nanocrystalline material is 2.5% higher than that of ferrite. This number is amplified in scenarios with higher power.

4、 Three major application battlefields: from mobile phones to cars

Smartphones and consumer electronics are the fields with the highest usage of magnetic separators. By 2025, the number of ferrite magnets used for wireless charging of consumer electronics worldwide will reach 1.33 billion. At the wireless charging receiving end of the mobile phone, a magnetic separator is attached between the coil and the metal back cover, which not only prevents eddy current heating, but also gathers magnetic flux to enhance induction strength. With the continuous compression of the internal space of 5G mobile phones, ultra-thin nanocrystalline magnetic separators are becoming a standard configuration for more and more flagship models.

Wearable devices and TWS earphones are the most prominent areas of the "invisible value" of magnetic separators. The internal space of the charging compartment for smartwatches and TWS earphones is more cramped than that of mobile phones - every 0.1mm increase in thickness may affect wearing comfort or battery capacity. The ultra-thin nature of the 30 μ m nanocrystalline magnetic separator makes it an ideal choice for wireless charging solutions in wearable devices. The shielding film for the charging compartment of Bluetooth earphone boxes has widely adopted the nano crystal magnetic isolation scheme.

Car wireless charging represents the fastest-growing application direction. The global market for magnetic shielding sheets for wireless charging in vehicles is estimated to reach 192 million US dollars by 2025 and is expected to grow to 783 million US dollars by 2032. The in car scenario requires higher power (15W-50W), wider temperature range (-40 ℃ to 150 ℃), and higher reliability for magnetic separators. Nanocrystalline materials can maintain stable saturation magnetic induction intensity (Bs ≥ 1.2T) and coercivity (Hc ≤ 5A/m) in extreme environments ranging from -40 ℃ to 150 ℃. After adopting nanocrystalline shielding sheets, a leading car company's 15kW wireless charging system efficiency has jumped from 88% to 93%, while controlling electromagnetic radiation values within 30% of international standards.

5、 Selection points: How to choose the right magnetic separator for your device?

When engineers select wireless charging receivers with magnetic separators, it is recommended to start from the following dimensions:

The working frequency is the first matching term. The Qi standard wireless charging frequency is between 100-200kHz. At this frequency, the permeability and loss performance of nanocrystalline magnetic separators are superior to those of ferrites. When selecting, it is necessary to ensure that the material has stable magnetic permeability and controllable losses at the target operating frequency.

The thickness and installation space determine feasibility. The minimum size of nanocrystalline magnetic separators can reach 30 μ m. Typically, ultra-thin models (0.06-0.1mm) are chosen for the interior of mobile phones; Car wireless charging can choose slightly thicker specifications to meet higher power requirements.

The saturation magnetic induction intensity is related to high-power performance. The saturation magnetic induction intensity (Bs) of nanocrystalline materials can reach over 1.2T, much higher than the 0.4-0.5T of ferrites. For fast charging scenarios above 15W, a high Bs value is the key to preventing magnetic saturation and ensuring charging efficiency.

Temperature control and reliability determine long-term experience. It is necessary to evaluate the working temperature range (-40 ℃ to 120 ℃) and the magnetic stability under long-term thermal cycling.

The global market size of magnetic separators for wireless charging is expected to steadily grow by 2025, and is expected to continue expanding by 2032. The global ferrite shielding film market is expected to reach 1.469 billion US dollars by 2032. The global market for nanocrystalline noise suppression chips is expected to grow to 329 million US dollars by 2032. Driven by the popularization of wireless charging in smartphones, the explosion of wearable devices, and the increasing penetration rate of wireless charging in cars, the magnetic isolation sheet of wireless charging receivers is moving from "professional material selection" to the standard configuration of electromagnetic compatibility design in consumer electronics and automotive electronics.

Advanced Institute (Shenzhen) Technology Co., Ltd. will continue to deepen its cultivation in the field of wireless charging receiver magnetic isolation sheets, providing customers with higher performance and more reliable magnetic flux guidance and eddy current suppression solutions through material innovation and precision technology.