The wireless charging power of smartphones has climbed from 5W and 15W to over 50W, NFC near-field payment has become a flagship standard, 5G antenna Wi-Fi、 Bluetooth and other functions are highly integrated into a few millimeters thick body - with metal frames, batteries, camera modules, and other components located next to these wireless modules.

A physical fact that troubles engineers is that when an alternating magnetic field encounters a metal surface, eddy currents are generated in the metal, which in turn generate a reverse magnetic field that cancels out the original magnetic field of the antenna. The result is a sharp drop in wireless charging efficiency, shortened NFC card reading distance, or even complete failure. Actual test data shows that in a typical 15W smartphone wireless charging module, the eddy current loss of the metal backplate at the receiving end can reduce charging efficiency by 18% to 25% without using a magnetic separator.

2、 Magnetic separator and absorbing material: one for "guidance" and one for "absorption"

In the electromagnetic management inside mobile phones, magnetic separators and absorbing materials play different roles, and understanding this difference is a prerequisite for selecting the right one.

The physical mechanisms, installation locations, and selection parameters of the two are different. Advanced Institute Technology integrates the material systems and process platforms of both, providing integrated solutions according to the stacking requirements of mobile phone structures.

3、 Why do mobile phones need magnetic separators: Three typical scenarios

4、 Material System: Performance Comparison between Ferrite and Nanocrystals

The mainstream material systems for mobile phone magnetic separators include ferrite and nanocrystals, and the performance differences between the two determine their respective applicable scenarios.

Data source: Actual measurement by the Advanced Institute of Science and Technology Laboratory and industry public information

The ferrite magnetic separator technology is mature and cost-effective, suitable for both transmitting and low-power receiving ends. However, its thickness is relatively large (usually above 0.2mm) and it is prone to breakage when bent, which limits its application in ultra-thin mobile phones.

The nanocrystalline magnetic separator is composed of copper foil and multiple layers of organic tape stacked together, containing tiny ferromagnetic nanocrystalline materials inside. Its initial magnetic permeability can reach 20000-80000, much higher than that of ferrite; The saturation magnetic induction intensity is above 1.2T, making it less prone to magnetic saturation in high-power wireless charging scenarios; The thickness of a single piece can be as low as 18-30 μ m, with good flexibility and bendability. The nanocrystalline magnetic separator can simultaneously meet the three functions of WPC wireless charging, MST magnetic secure transmission, and NFC near-field communication without interfering with each other.

Advanced Institute of Technology:A complete technical chain has been constructed around soft magnetic ferrite and amorphous/nanocrystalline alloy systems, from powder design, microstructure control to the formation of absorbing components.

5、 Key Performance: What Engineers Should Pay Attention to

The following indicators are the most critical when evaluating the absorbing materials of mobile phone magnetic separators:

• Real part of magnetic permeability (μ '):The core indicator of guiding magnetic field capability. In the 13.56MHz frequency band, the typical value of the advanced institute technology product's μ 'is 150 ± 10; In the main frequency range of 100kHz-300kHz wireless charging, the μ 'can reach 850-1200. A higher μ 'means stronger magnetic focusing ability and higher coil coupling efficiency.
• Loss factor (tan δ):It determines the efficiency of energy transmission. The loss factor should be controlled within the range of 0.01-0.05 to effectively reduce eddy current loss and hysteresis loss, and avoid the heat generated by the magnetic separator itself.
• ThicknessKey parameters under internal space constraints of mobile phones. Thicker magnetic separators are not necessarily better - increasing thickness can significantly improve the magnetic flux diversion ability in the early stages, but the benefits decrease after exceeding a certain value. Experimental data from the Advanced Institute of Technology Laboratory shows that in 13.56MHz NFC applications, a 0.05mm magnetic separator can increase the reading distance by 32%, 0.10mm by 50%, 0.20mm by 65%, and 0.30mm by 68%. For most HF/NFC applications, 0.10-0.20mm is the optimal balance point between performance and structure. If ultra-thin design is required, a 0.05mm flexible sheet can achieve over 30% performance recovery.
• Surface impedance:Affects eddy current losses and heat generation. The surface impedance of advanced technology products at 13.56MHz is ≥ 1 × 10 ⁶ Ω/sq, which is much higher than the common level in the industry and effectively reduces eddy current losses.
• Working temperature range:The temperature resistance range of advanced institute technology products covers -40 ° C to 125 ° C, and meets the reliability requirements of automotive standards by passing the IEC 60068-2-2 high temperature test standard.
• Saturated magnetic induction intensity (Bs):In high-power wireless charging scenarios, the magnetic separator may become saturated and fail due to excessive magnetic field strength. The advanced technology product Bs reaches 350-550mT, ensuring that it is not easily magnetically saturated during high-power charging.

Data source: Advanced Institute Technology's own laboratory and third-party testing reports

6、 Selection considerations: Engineering decisions from frequency to space

7、 Conclusion

The essence of absorbing materials for mobile phone magnetic separators is to use "guidance" instead of "blocking" to deal with magnetic field problems. It does not use conductive materials to reflect the magnetic field back, but instead uses high permeability materials to build a low magnetic resistance "highway" for magnetic field lines - allowing the magnetic field to propagate along the interior of the magnetic separator, bypass metal obstacles, and concentrate in the effective area of the antenna, while minimizing energy loss with low loss characteristics.

From improving the efficiency of wireless charging to restoring the reading distance of NFC, from sensor protection to 5G antenna isolation - mobile phone magnetic isolation absorbing materials are pushing "magnetic field management" from "passive shielding" to "active guidance". Understanding the synergistic relationship between μ 'and μ' ', the material differences between ferrite and nanocrystals, and the engineering trade-offs between thickness and performance - these are the key to upgrading the magnetic separator from a "single piece of magnetic material" to an "engineering decision".