When the third generation semiconductor devices push the power frequency to the MHz level, traditional soft magnetic materials are on the brink of collapse under the heavy pressure of high-frequency losses, noise, and processing costs! Is magnetic integration technology the savior of power electronics, or the last straw that crushes material systems? 

With the rapid development of power electronic devices towards high frequency, miniaturization, and high power density, magnetic integration technology has become the core means to break through the limitations of traditional magnetic components in terms of volume and efficiency. 

This technology significantly reduces system losses and improves power density by integrating magnetic components such as inductors, transformers, and filters into a single magnetic core or composite structure. It has been widely used in fields such as new energy vehicles, 5G communication power supplies, data centers, and consumer electronics. 

However, magnetic integration technology still cannot escape the requirement for upgrading the performance of soft magnetic materials. Traditional soft magnetic materials, such as ferrite and silicon steel, are exposed to significant shortcomings under extreme conditions such as high frequency, high temperature, and strong magnetic fields, which forces the materials science and industry to collaborate and innovate. 

Previously, Professor Chen Wei, honorary chairman of the Magnetic Technology Professional Committee and professor of Fuzhou University, gave the evaluation of "usable" when discussing the current status of soft magnetic materials in China at public occasions such as the 11th Joint Academic Conference on Power Transformers and Magnetic Components. This can be said to be the most appropriate evaluation of the current situation of soft magnetic materials in China. 

However, this article will systematically analyze the key performance requirements of magnetic integration for soft magnetic materials and explore potential paths for future material innovation. 

The synergistic relationship between the core requirements of magnetic integration and material properties 

The essence of magnetic integration technology is to achieve efficient transfer of electromagnetic energy and minimize losses through structural design and material optimization. The synergistic relationship between its core requirements and material properties is shown in the following table:

The relationship between magnetic integration core requirements and material properties 

Compilation of "Magnetic Components and Power Supply" 

It should be emphasized that the requirements for soft magnetic materials in magnetic integration are no longer static mapping relationships that correspond one-to-one in the traditional magnetic component design process, but dynamic balance and iterative optimization between technical requirements and material properties. 

Taking high-frequency technology as an example, it requires materials to have low eddy current losses (otherwise the losses will increase dramatically) and high magnetic permeability (otherwise the energy transfer efficiency will be low). 

To achieve the goals of high frequency, miniaturization, and high reliability in magnetic integration technology, it is necessary to rely on the key performance parameters of soft magnetic materials (such as saturation magnetic flux density Bs, losses, temperature stability, etc.), and the shortcomings of soft magnetic material performance will limit the design boundary of magnetic integration, forming a bidirectional constraint and adaptation relationship between "demand performance". 

At the system level, the implementation of magnetic integration technology requires cross disciplinary collaboration across multiple fields such as power electronics, materials science, and thermal management, rather than single dimensional parameter matching. 

Hailaibuqu, a national senior engineer in electrical engineering, member of the Magnetic Technology Special Committee of the China Power Supply Society, and R&D general manager of Huizhou Magnetic Pole New Energy Technology Co., Ltd. (referred to as "Magnetic Pole New Energy"), stated that currently engineers can only achieve overall optimization through bidirectional adaptation and compromise between design goals and soft magnetic material performance parameters. From this perspective, there is still a lot of room for innovation or improvement in soft magnetic materials in the future. 

High frequency and low loss: the "lifeline" of soft magnetic materials 

In the process of magnetic integration design, increasing losses is currently a challenging issue. Previously, Gao Jun, CTO of Innolux, stated that in the currently popular leakage inductance integration solutions, the primary magnetic field will enter the secondary side in a non coupled manner, generating stray magnetic fields. Additionally, the leakage inductance magnetic field will cut through the wire package, and the magnetic field of the inductor will overlap, resulting in significant high-frequency losses. 

In high-frequency magnetic integration scenarios (such as MHz level switching power supplies), magnetic core losses (including hysteresis losses, eddy current losses, and residual losses) account for more than 30% of the total system losses, becoming a key factor restricting efficiency improvement. 

Associate Professor Ying Yao from the Institute of Magnetic and Electrical Functional Materials at Zhejiang University of Technology mentioned in his introduction of its high-frequency and low loss ferrite soft magnetic materials that the sharp increase in residual losses leads to excessive heating of power devices and a decrease in energy efficiency. Residual losses must be considered, and hysteresis losses, eddy current losses, and residual losses need to be reduced simultaneously. 

It can be said that the sharp increase in losses at high frequencies is the main obstacle to the high-frequency application of manganese zinc ferrite soft magnetic materials, and also limits the popularization of magnetic integration in a wider range of fields. 

If existing materials cannot meet low losses (such as ferrite soft magnetic materials with high eddy current losses at 1MHz), the high-frequency design of magnetic integration will be forced to compromise, such as reducing operating frequency, increasing heat dissipation costs, or adopting other compromise solutions. 

This phenomenon is particularly evident in the design of third-generation semiconductor devices. 

For this reason, universities and industries have also made multiple attempts.

Revised high-frequency loss separation formula for soft magnetic materials by Professor Ying Yao's team 

For example, Professor Ying Yao's team increased the initial magnetic permeability by 28.2% and 13.9% respectively by adding YIG appropriately to manganese zinc ferrite, reducing high-frequency losses. At room temperature of 1 MHz and 3 MHz, the losses were reduced by 56.4% and 36.6% respectively, and low losses were maintained in the temperature range of 25-140 ° C. The grain boundary resistance Rgb was also increased, greatly reducing the eddy current losses of the material. 

Due to the differences in physical properties and microstructure of different materials, soft magnetic material companies need to adopt targeted methods to reduce losses. 

Overall, the reduction of losses for different materials requires a combination of intrinsic material properties and process innovation. Here are the loss reduction strategies mentioned by authoritative experts in the field of different soft magnetic materials that we have sorted out:

Comparison of Loss Reduction Strategies for Three Types of Soft Magnetic Materials 

In the future, if breakthroughs can be made in cross material composite and atomic level structural design, it will be the key to reducing the high-frequency loss limit, which will further promote the popularization and application of magnetic integration technology. 

Low magnetostriction effect: the cornerstone of silence and precision 

The magnetostriction effect (deformation of materials during magnetization) is the main source of high-frequency vibration and noise, which is an intrinsic characteristic of different types of soft magnetic materials and is particularly critical for scenarios such as wireless charging and medical equipment.

Comparison of Material Magnetostriction Coefficient (λ s) 

The magnetostriction coefficients of different materials fundamentally limit their application scenarios. 

Hailaibuqu told "Magnetic Components and Power Supply" that the reason why amorphous alloy magnetic cores have not broken through is because their magnetostriction coefficient is relatively large, and they have severe whistling at high frequencies, including iron-based amorphous materials. 

In addition to the inherent characteristics of the material, magnetic integration can also cause a superposition effect on the original noise source, making it more complex. 

Previously, in an interview with an EMC expert from Geely Jike, "Magnetic Components and Power Supplies" stated: 

Firstly, the phenomenon of mutual interference between components is more severe. Due to the reduction in volume of magnetic integrated products, the distance between various components is tighter, which also leads to greater noise interference between the components. Moreover, magnetic integrated products limit the position of power devices on the board, resulting in the VDS of power devices, i.e. the rapidly changing voltage generated by the D and S poles, becoming an additional source of interference. 

The second reason is that the stray capacitance of the magnetic component itself is larger and more complex. The stray capacitance of independent magnetic components is mainly generated by the distributed capacitance of the primary and secondary sides, with a single source and relatively easy to handle. Magnetic integrated products integrate multiple magnetic components, such as transformers+inductors, inductors+inductors, etc., resulting in larger and more complex stray capacitance, which is also more difficult to handle. 

The magnetostriction effect, as an intrinsic property of materials, directly determines the noise level in high-frequency scenarios, and the introduction of magnetic integration technology has pushed this contradiction to the extreme - the "inherent deficiencies" of materials themselves and the "acquired interference" of system integration form a double pincer. Only by deeply linking material innovation with structural innovation can we break the curse of "high-frequency noise" and further broaden the scope of application of magnetic integration technology.

Comparison and Challenges of Processing Properties of Various Soft Magnetic Materials 

From a manufacturing perspective, ferrite soft magnetic materials have high brittleness and are prone to edge breakage after sintering, especially for flat magnetic core sheets (<1mm) with a processing yield of only 60% -70%. 

Wang Liping, General Manager of Ankeyuan Magnetic Devices Co., Ltd. (hereinafter referred to as "Ankeyuan") in Huizhou, stated in an interview with "Magnetic Components and Power Supply" that metal magnetic powder cores, due to the lack of sintering process, require high density to produce high-quality magnetic core products through strong pressure pressing, and have high pressure requirements for pressing equipment. It is reported that there are currently magnetic core products in the industry with a molding pressure of up to 25 tons/square centimeter. 

This leads to a series of problems in its manufacturing process, including high equipment costs, low manufacturing efficiency, and small volume or size that can be integrally formed. Taking pure circular magnetic cores as an example, the maximum diameter size that can be integrally formed is around 55mm. This series of problems leads to higher manufacturing costs for metal magnetic powder cores. 

Non crystalline nanocrystalline soft magnetic materials have high brittleness and are also prone to cracking during traditional stamping; Nanocrystals require annealing treatment, which has high process complexity and also faces the problem of high material costs. 

Hu Weican, R&D Manager of China New Business Unit of Guangzhou Shengmeida Motor Co., Ltd., mentioned in an interview with "Magnetic Components and Power Supply" that in the early days, the I-shaped ferrite core used for POC inductors was usually combined with magnetic simulation and practical applications to increase the R-angle or add other improvement methods to the ideal design structure. 

After magnetic integration, it usually faces more complex magnetic core structures. 

Hu Weican said that during his previous visit to a magnetic core enterprise, he had seen a type of magnetic core applied to overseas inverter projects. It added edge tying and opened a wind tunnel to solve the heat dissipation problem on the basis of an EE type magnetic core structure. The overall structure was particularly complex, and the magnetic core enterprise also reported that the processing difficulty had increased dramatically. 

Hu Weican gave another case: Recently, there has been a new type of ultra-thin ferrite chip magnetic core with a thickness of less than 0.1mm, which is manufactured using a new process similar to injection molding. During the colloidal injection molding process, iron powder is fixed, which is more suitable for the production and manufacturing of complex magnetic cores. 

This more complex product structure significantly increases the difficulty and cost of processing. Hu Weican told "Magnetic Components and Power Supply" that the magnetic core processing cost of a Shengmeida excitation transformer used in car drives alone exceeds 130 yuan. 

Regardless of the type of soft magnetic material, after magnetic integration, it faces the problems of processing difficulty and increased processing costs, especially the difficulty of integrated magnetic core molding, which greatly increases. The industry needs to explore more advanced manufacturing processes to meet manufacturing needs. 

Otherwise, for power design engineers, they will be forced to compromise between performance and real-world processes, like walking on thin ice to seek a balance point. 

Conclusion: Collaborative Evolution of Materials Devices Systems 

The requirements of magnetic integration technology for soft magnetic materials have shifted from a single performance indicator to a multi-objective collaborative optimization of "high frequency high Bs high temperature easy processing". In the future, soft magnetic material manufacturers need to collaborate deeply with the power supply side to promote a new era of "on-demand customization" of soft magnetic materials through cross scale design (from atomic level doping to macroscopic circuit topology optimization). Only in this way can the ultimate need for efficient energy conversion be met. 

*Disclaimer: All statements and opinions regarding original and reprinted articles are neutral, and the articles are only for readers to learn and communicate. The copyright of articles, images, etc. belongs to the original author. If there is any infringement, please contact us for deletion. This article is reprinted from (Big Bit Electronic Transformers and Inductors)