Insulating Coating of Soft Magnetic Particles With Lower Coercive Force
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Solution Overview
Problem
Existing methods for forming insulating coatings on magnetic powder particles, such as those used in inductors, often introduce strains that increase the coercive force of the particles, and struggle to achieve a balance between low eddy current loss and high packing density.
Innovation Solution
A particle coating method involving a heating step to relax strains in soft magnetic metal particles within a temperature range of 100°C to 500°C for 0.1 to 300 hours, followed by an insulating film formation using atomic layer deposition or mist CVD methods to create a thin, uniform insulating film, thereby reducing coercive force and maintaining low eddy current loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a mechanofusion method is used to form a silicon dispersion layer, then an insulating coating can be formed without heat treatment, but the coercive force increases due to strain introduced during the process
Solution Approach 1:
The patent replaces the mechanofusion method (mechanical energy-based) with a chemical vapor deposition method. The insulating film is formed through chemical reactions of silicon-containing gas with the particle surface, eliminating the mechanical strain that causes increased coercive force while still achieving effective insulation between particles.
Solution Approach 2:
The patent changes the fundamental parameter of film formation from mechanical fusion to chemical deposition. By controlling temperature (100-500°C) and gas composition during the chemical vapor deposition process, the method achieves insulating film formation without introducing the harmful strains associated with mechanical methods.
2Quantity of substance
If the average particle diameter is reduced below 50 μm, then higher packing density can be achieved, but more strains are included in the particles increasing coercive force
Solution Approach 1:
The patent replaces mechanical strain introduction (from pulverization and mechanofusion) with a chemical film formation process. This allows small particles to maintain low coercive force by avoiding mechanical processing that introduces strain, while still achieving the necessary insulating coating for high packing density applications.
Solution Approach 2:
The patent performs strain relaxation through controlled heating (100-500°C) before forming the insulating film. This preliminary thermal treatment reduces the inherent strain in fine particles, preparing them for low-coercive-force operation while maintaining the particle size needed for high packing density.
3Temperature
If mechanical energy is used to form the silicon dispersion layer, then the layer can be formed without heat treatment, but additional strain is applied to the particles further increasing coercive force
Solution Approach 1:
The patent replaces the mechanical mechanofusion process with chemical vapor deposition. Instead of using mechanical energy to fuse silicon particles to the magnetic particle surfaces, the method uses chemical reactions of silicon-containing gases with the particle surfaces, eliminating additional strain while still forming an effective insulating layer.
Solution Approach 2:
The patent utilizes phase transitions of silicon-containing gases during chemical vapor deposition. The silicon precursor gas condenses and reacts on the particle surface to form the insulating film, using phase change and chemical reaction rather than mechanical energy to achieve film formation.
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 method effectively reduces coercive force while maintaining low eddy current loss and achieving high packing density, resulting in magnetic particles with improved magnetic properties for applications like powder magnetic cores.
Implementation Method 1
a heating step of heating soft magnetic metal particles containing an amorphous phase within a temperature range of 100° C. or higher and 500° C. or lower for 0.1 hours or more and 300 hours or less
Implementation Method 2
an insulating film formation step of forming an insulating film at surfaces of the soft magnetic metal particles by a chemical vapor deposition method
Data Source
AI summary
A particle coating method includes a heating step of heating soft magnetic metal particles containing an amorphous phase within a temperature range of 100° C. or higher and 500° C. or lower for 0.1 hours or more and 300 hours or less, and an insulating film formation step of forming an insulating film at surfaces of the soft magnetic metal particles by a chemical vapor deposition method. The soft magnetic metal particles preferably contain the amorphous phase at 50 vol % or more.