Low-Permittivity Fluorine Coating for High-Frequency Soft Magnetic Powder

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Solution Overview

Problem

Existing soft magnetic cores face challenges in reducing eddy current loss in high frequency ranges due to the high permittivity of inorganic insulating films, which also decrease magnetic permeability when thicker films are used to mitigate eddy currents.

Innovation Solution

Coating soft magnetic particles with an insulating film containing a fluorine compound, with a specific average particle diameter and thickness, and a relative permittivity of 5.0 or less, to enhance insulation and maintain magnetic properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the film thickness of the inorganic insulating film is increased to reduce eddy current, then eddy current loss is reduced, but the volume ratio of soft magnetic material decreases and magnetic permeability decreases

Engineering Contradiction:

Improveeddy current lossVSAvoidvolume ratio of soft magnetic material

Core Design Contradiction:

Loss of energyVSQuantity of substance

Solution Approach 1:

The patent changes the permittivity parameter of the insulating film by using a fluorine compound with relative permittivity of 5.0 or less, which is lower than conventional inorganic insulating films. This parameter change allows effective eddy current reduction with thinner film thickness, thereby maintaining higher volume ratio of soft magnetic material and preserving magnetic permeability.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the film thickness of the inorganic insulating film is increased to reduce eddy current, then eddy current loss is reduced, but magnetic permeability decreases

Engineering Contradiction:

Improveeddy current lossVSAvoidmagnetic permeability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent applies parameter change by selecting fluorine compounds with specific permittivity characteristics (relative permittivity of 5.0 or less). This enables achieving the same eddy current suppression effect with reduced film thickness, thereby maintaining magnetic permeability at acceptable levels while reducing energy loss.

Inventive Principle:

Principle #35Parameter changes

3Temperature

If a conventional inorganic insulating film is used, then heat resistance is maintained, but permittivity is relatively high causing insufficient eddy current reduction

Engineering Contradiction:

Improveheat resistanceVSAvoideddy current loss

Core Design Contradiction:

TemperatureVSLoss of energy

Solution Approach 1:

The patent changes the material parameter from conventional inorganic insulating films to fluorine compounds with specifically low permittivity (5.0 or less). This parameter change achieves superior eddy current reduction while the patent also ensures heat resistance is maintained through appropriate selection and treatment of the fluorine compound.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material strategy by using fluorine compounds that combine low permittivity characteristics with adequate heat resistance. The fluorine compound forms a composite insulating structure that integrates multiple desirable properties: low permittivity for eddy current suppression and sufficient thermal stability for high frequency applications.

Inventive Principle:

Principle #40Composite materials

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 insulating film effectively reduces eddy current loss while preserving magnetic permeability and saturation magnetic flux density, allowing for compacted cores with improved performance in high frequency applications.

Implementation Method 1

mechanically attaching the fluorine compound powder to a particle surface of the soft magnetic powder so as to form an insulating film

Methodology Applied

Scientific EffectMechanical attachment:

Implementation Method 2

causing a polymerization reaction of a fluorine-containing gas as a monomer gas to form an insulating film which contains a fluorine compound and with which a particle surface of a soft magnetic powder is coated

Methodology Applied

Scientific EffectPolymerization reaction: Photopolymerisation

Implementation Method 3

polymerizing a fluorine compound precursor containing a fluorine atom by a sol-gel method to form an insulating film which contains a fluorine compound and with which a particle surface of a soft magnetic powder is coated

Methodology Applied

Scientific EffectSol-gel method:

Implementation Method 4

an eddy current is generated due to a change in a magnetic field generated inside the soft magnetic core, which causes an eddy current loss

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Implementation Method 5

one of factors for reducing the eddy current is a permittivity of an insulating film with which surfaces of particles of a soft magnetic powder are coated

Methodology Applied

Scientific EffectPermittivity: Dielectric Permittivity

Data Source

PatentUS12400777B2Insulator-coated soft magnetic powder, method for producing insulator-coated soft magnetic powder, dust core, magnetic element, electronic device, and vehicle

Publication Date: 2025.08.26 SEIKO EPSON CORP

AI summary

An insulator-coated soft magnetic powder contains: a soft magnetic powder; and an insulating film with which a particle surface of the soft magnetic powder is coated and which contains a fluorine compound, in which an average particle diameter of the soft magnetic powder is 1 μm or more and 15 μm or less, an average thickness of the insulating film is 5 nm or more and 50 nm or less, and a relative permittivity of the fluorine compound is 5.0 or less.