Core-shell magnetic particles for high-frequency inductors
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Solution Overview
Problem
Existing magnetic materials fail to effectively control permeability real part (μ′) and imaginary part (μ″) at high frequencies, particularly above 10 MHz, leading to unsatisfactory performance in inductors and electromagnetic wave absorbers, with issues of cost, yield, and thermal stability.
Innovation Solution
A core-shell type magnetic particle comprising magnetic metal particles with Fe, Co, or Ni, combined with nonmagnetic metals like Al and Si, and elements like carbon and nitrogen, coated with an oxide layer, which enhances magnetic anisotropy and thermal stability, allowing for improved high-frequency magnetic characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ferrite or amorphous alloy is used for inductor in high frequency region (1 MHz to 10 MHz), then excellent magnetic characteristics are obtained with high μ′ and low μ″, but μ′ is lowered in higher frequency region (10 MHz or more)
Solution Approach 1:
The magnetic material is segmented into fine particles (average diameter 0.1 to 10 μm) to reduce eddy current loss and enable high-frequency operation. This particle segmentation allows the material to maintain magnetic properties at frequencies where bulk materials fail.
Solution Approach 2:
The invention uses composite structures including core-shell type particles with magnetic metal cores and oxide coating layers, combining different material properties to achieve both high permeability and low loss at high frequencies.
2Reliability
If thin film technologies (sputtering method) are used to develop inductance elements, then excellent characteristics in high frequency region are confirmed, but large apparatus is needed and precise control of film thickness is needed, resulting in insufficient cost performance and yield
Solution Approach 1:
The invention replaces complex thin film deposition processes with a mechanical particle-based approach using ball milling and classification, eliminating the need for large sputtering apparatus while achieving comparable or superior high-frequency characteristics.
3Reliability
If inductor is produced by thin film technology, then high frequency characteristics are improved, but long-term thermal stability of magnetic characteristics is insufficient in conditions of high temperature and high humidity
Solution Approach 1:
The core-shell structure combines magnetic metal cores with protective oxide coating layers, creating a composite material that maintains magnetic properties at high temperatures while the oxide shell provides thermal and environmental stability.
Solution Approach 2:
The oxide coating layer is formed beforehand on the magnetic metal particles to protect them from oxidation and thermal degradation, providing preemptive protection against high-temperature and high-humidity conditions.
4Reliability
If electromagnetic wave absorber is manufactured by binder forming method mixing ferrite particle, carbonyl iron particle, FeAlSi flakes, FeCrAl flakes etc. with resins, then electromagnetic wave absorption is achieved, but both μ′ and μ″ are extremely low in high frequency region (1 GHz or more)
Solution Approach 1:
The use of fine magnetic particles (0.1 to 10 μm) instead of large flakes or bulk materials reduces eddy current effects and enables the material to maintain magnetic permeability at GHz frequencies, extending the effective frequency range for electromagnetic wave absorption.
Solution Approach 2:
The invention changes the particle size parameter to the micrometer and sub-micrometer range, which fundamentally alters the electromagnetic response of the material, enabling high-frequency operation where conventional flake-based absorbers fail.
5Productivity
If materials are synthesized by mechanical alloying method, then material production is achieved, but long-term thermal stability is insufficient and yield is low
Solution Approach 1:
The oxide coating layer is formed preliminarily on the magnetic metal particles during the ball milling process, providing thermal protection before the particles are subjected to high-temperature conditions, thereby ensuring long-term thermal stability.
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 core-shell type magnetic particles achieve high magnetic permeability with reduced eddy-current loss and extended ferromagnetic resonance frequency, enabling efficient use in high-frequency applications such as inductors and electromagnetic wave absorbers with improved thermal stability and versatility across frequency bands.
Implementation Method 1
eddy-current loss which is a cause of loss at high frequencies
Implementation Method 2
enhances magnetic anisotropy and thermal stability
Data Source
AI summary
A core-shell type magnetic particle comprises magnetic metal particle and an oxide coating layer formed on the surface of the magnetic metal particle. The magnetic metal particle contains a magnetic metal containing at least one selected from the group consisting of Fe, Co and Ni, a nonmagnetic metal and at least one element selected from carbon and nitrogen. The oxide coating layer is constituted of an oxide or a composite oxide containing the nonmagnetic metal which is one of the constituents of the magnetic metal particle.