Composite Soft Magnetic Particle for High-Frequency Eddy Current Reduction
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Solution Overview
Problem
Existing magnetic cores in mobile devices face challenges with increased eddy current losses at higher driving frequencies, and the use of mixed powders can lead to segregation and uneven dispersion issues, limiting the packing ratio and magnetic permeability.
Innovation Solution
A composite particle with a soft magnetic metallic core and a fusion-bonded coating layer of different composition, where the Vickers hardness and thickness relationships optimize the packing ratio and magnetic permeability, allowing the coating layer to penetrate and uniformly distribute during compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the driving frequency of magnetic element is increased to improve performance, then the performance is improved, but the eddy current loss increases
Solution Approach 1:
The magnetic core is divided into numerous fine powder particles instead of using continuous ribbon or block structures. This segmentation interrupts eddy current paths, significantly reducing eddy current loss while maintaining magnetic performance at high frequencies.
Solution Approach 2:
A composite structure is created by coating soft magnetic powder particles with a binder material. This composite particle structure provides both magnetic functionality and mechanical integrity, while the binder also serves as insulation between particles to further reduce eddy currents.
2Strength
If the amount of binder is increased to maintain shape and provide insulation, then the mechanical strength is improved, but the magnetic permeability decreases
Solution Approach 1:
The chemical composition and physical properties of the binder material are optimized to achieve the right balance. The binder is selected to have appropriate viscosity, curing characteristics, and magnetic properties that minimize permeability loss while providing sufficient mechanical strength and insulation.
Solution Approach 2:
The binder is applied in controlled amounts specifically at the interfaces between magnetic particles where it is most needed for insulation and bonding, rather than uniformly distributed throughout the entire core volume, minimizing its negative impact on overall magnetic permeability.
3Reliability
If mixed powder of amorphous and crystalline soft magnetic powder is used to improve packing ratio, then the magnetic permeability is improved, but particle segregation occurs
Solution Approach 1:
Different material properties are assigned to different parts of the composite particle structure. The core particles provide magnetic functionality while the binder provides mechanical integrity and insulation, with each component optimized for its specific function rather than requiring uniform composition throughout.
Solution Approach 2:
Instead of mixing different types of magnetic powders that segregate, a composite particle structure is used where soft magnetic powder particles are coated with binder material. This creates a stable heterogeneous structure that maintains uniform distribution without segregation while achieving high packing ratio and magnetic permeability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composite particle design achieves a high packing ratio and magnetic permeability, reducing eddy current losses and maintaining mechanical properties, resulting in a reliable magnetic element for portable electronic devices.
Implementation Method 1
forming the coating layer by fusion-bonding coating particles having a smaller diameter than the particle to the surface of the particle through mechanical pressure welding
Implementation Method 2
by subjecting a crystalline soft magnetic powder to plastic deformation when performing compression-molding
Implementation Method 3
when an aggregate of the composite particles (a composite particle powder) is compressed and molded
Data Source
AI summary
A composite particle includes: a particle composed of a soft magnetic metallic material, and a coating layer composed of a soft magnetic metallic material having a different composition from that of the particle and fusion-bonded to the particle so as to cover the particle, wherein when the Vickers hardness of the particle is represented by HV1 and the Vickers hardness of the coating layer is represented by HV2, HV1 and HV2 satisfy the following relationship: 100≦HV1−HV2, and when half of the projected area circle equivalent diameter of the particle is represented by r and the average thickness of the coating layer is represented by t, r and t satisfy the following relationship: 0.05≦t/r≦1.