High permeability and low loss magnetic isolation sheet: Why does the magnetic isolation sheet change from an "auxiliary material" to a "critical component" when the system power density increases

The magnetic component industry is undergoing a structural change. If the keywords discussed in previous years were focused on "recovery", "pressure", and "involution", then by 2025, a clearer change is emerging: the application side is reshaping the power system architecture at an unprecedented speed, and magnetic component products are no longer just passive adaptation basic components, but gradually entering the core position of system level design and technology game.

The role transformation of magnetic separators is a microcosm of this trend. In traditional wireless charging receiver designs, magnetic separators are often considered as "accessories" - attached between the coil and battery to guide magnetic flux and reduce leakage. The focus of selection is often on whether the magnetic permeability is high enough. But when the power consumption of the AI server power supply increases from 800W to 2-3kW, when the wireless charging power of the vehicle is increased to over 50W, and when the device thickness is compressed to less than 1mm, the loss, saturation margin, and temperature stability of the magnetic separator begin to directly affect the efficiency and reliability of the system.

How to change the design constraints of magnetic separators by increasing system power density

The evolution of AI server power architecture provides a clear observation window. The current mainstream AI server power consumption per unit has increased from 800W to 2-3kW, and the overall cabinet power consumption has increased from 10-20kW to 60-100kW. The liquid cooling heat dissipation solution is accelerating its implementation, and the cold plate liquid cooling PUE can be reduced to 1.20-1.25.

After the heat dissipation bottleneck is removed, the efficiency and power density targets of the power supply are refreshed. This means that magnetic components need to handle greater power in a smaller volume, and the requirements for loss control are tightened synchronously. The high-frequency development of magnetic devices has promoted the development of materials, while the application of magnetic integration and new materials has in turn driven the miniaturization and low loss of server power supplies.

The field of in car wireless charging is showing a similar trend. By 2025, the global market for wireless charging ferrite magnets for vehicles is expected to reach 50 million pieces, and the market size is projected to reach 292 million US dollars by 2032, with a compound annual growth rate of 25.4%. New energy vehicles have fully entered the 800V platform stage, and the power level of the on-board charging module continues to improve, which puts higher requirements on the saturation magnetic induction and high-temperature stability of the magnetic separator.

The application boundary of ferrite is narrowing

MnZn ferrite is the most mature material for wireless charging magnetic separators, with naturally high resistivity and a mature engineering foundation in the low-frequency range. But the saturation magnetization Bs of ferrite is only 0.3-0.5 T, and the Curie temperature is about 100-250 ° C. In wireless charging applications above 15W, the working magnetic flux density may be close to its saturation magnetization. Once the material enters the saturation zone, the magnetic permeability sharply decreases, and the magnetic field penetrates the magnetic separator into the metal layer, causing both eddy current temperature rise and deterioration of charging efficiency.

The higher requirements for magnetic components in the era of liquid cooling have further amplified the limitations of ferrites. The liquid cooling heat dissipation scheme involves systematic design challenges such as anti-corrosion, oil resistance, insulation, and optimization of thermal conductivity paths for new materials. The hard and brittle nature of ferrite makes it difficult to adapt to curved coils and complex assembly structures, while the flexibility of nanocrystalline and amorphous materials provides alternative solutions for these scenarios.

But this does not mean that ferrite will exit the market. In low-power scenarios below 5W, the cost advantage and mature sintering process of ferrite still remain competitive. The trend in the industry is the stratification of material systems: ferrites hold onto the low-frequency and low-power basic plate, while nanocrystalline and amorphous materials penetrate into high-frequency and high-power scenarios.

Reconstruction of loss control logic through high-frequency conversion

The increase in frequency has changed the priority of controlling the loss of magnetic separators. In the Qi standard frequency band (110-205 kHz), the weights of hysteresis loss and eddy current loss are relatively balanced. However, at the operating frequency of 6.78 MHz in the AirFuel resonant standard, eddy current losses are directly proportional to the square of the frequency, and their proportion rapidly increases. The refinement of the magnetic fragmentation pattern becomes a key variable for loss control.

The increase in the switching frequency of AI server power further strengthens this trend. Facing the ultimate demand for space and efficiency in AI server power supply and new energy vehicles, magnetic integration technology has become a key path to break through the bottleneck of volume and loss in high-frequency and high current scenarios. At high frequencies exceeding 1 MHz, power inductors need to reduce hysteresis losses while maintaining high magnetic permeability, and the material's frequency response and temperature stability must also meet the requirements.

The advantage of nanocrystalline materials in the high frequency range comes from their microstructure. When the grain size is controlled within the range of 10-20 nm, the magnetic domain wall passes through multiple grains simultaneously during movement, and the magnetic anisotropy of the grains is averaged by the exchange coupling effect. The hysteresis loss does not significantly increase with the increase of magnetic permeability. In terms of eddy current loss control, the fragmented magnetic treatment divides the continuous strip into small, mutually insulating fragments, cutting off the closed path of eddy currents over a large area.

Derive the judgment framework for material selection from system requirements

When the magnetic separator is upgraded from "auxiliary materials" to "key components", the selection logic also needs to shift from "parameter comparison" to "system matching". The following three dimensions of judgment can help engineers establish a more reasonable selection path.