Multilayer Coil Structure Using Epoxy-Filled Soft Magnetic Particles

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Solution Overview

Problem

Multilayer coil devices using soft magnetic materials face issues with low insulating properties, leading to short circuits and eddy current losses when the magnetic material and coil conductor are in direct contact.

Innovation Solution

A multilayer coil device is developed with a magnetic element body composed of soft magnetic particles and an epoxy resin, where the epoxy resin has an epoxy value of 150 or less and is filled in gap spaces between the soft magnetic particles, enhancing the insulating properties and strength of the device.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a soft magnetic material is used as the magnetic material, then magnetic characteristics are improved, but insulating property deteriorates causing short circuits

Engineering Contradiction:

Improvemagnetic characteristicsVSAvoidinsulating property

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

An epoxy resin coating is applied as an intermediary layer on the surface of soft magnetic particles. This coating layer has high insulating properties and prevents direct contact between the soft magnetic material and coil conductor, thereby eliminating short circuits while preserving the magnetic characteristics of the soft magnetic material.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The magnetic material is formulated as a composite consisting of soft magnetic particles mixed with epoxy resin. The epoxy resin serves both as a binder and as an insulating matrix, creating a composite material that combines the magnetic properties of soft magnetic particles with the insulating properties of epoxy resin, thus preventing short circuits.

Inventive Principle:

Principle #40Composite materials

2Reliability

If a soft magnetic material with low insulating property is used, then magnetic characteristics are improved, but eddy current losses increase

Engineering Contradiction:

Improvemagnetic characteristicsVSAvoideddy current losses

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The epoxy resin coating acts as an intermediary insulating layer between adjacent soft magnetic particles, disrupting the continuous conductive path that would otherwise allow eddy currents to flow through the soft magnetic material. This reduces eddy current losses while maintaining the magnetic characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

By creating a composite material where soft magnetic particles are dispersed in an epoxy resin matrix, the continuous conductive network is broken into isolated particle regions. The epoxy resin matrix provides electrical insulation between particles, thereby reducing eddy current paths and associated energy losses.

Inventive Principle:

Principle #40Composite materials

3Object-affected harmful factors

If resin is impregnated in voids between magnetic particles, then insulating property is improved, but strength deteriorates

Engineering Contradiction:

Improveinsulating propertyVSAvoidstrength

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The epoxy value of the resin is controlled to be 150 or less, which optimizes the balance between insulating properties and mechanical strength. This parameter control ensures that the resin provides sufficient insulation while maintaining adequate bonding strength with the magnetic particles and coil conductor.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The use of epoxy resin as the impregnation material creates a composite structure where the resin fills voids between particles and bonds with both the magnetic particles and coil conductor. The epoxy resin's adhesive properties and controlled epoxy value ensure that the composite maintains mechanical strength while providing electrical insulation.

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 use of an epoxy resin with a low epoxy value improves the insulating properties and Q value of the multilayer coil device, increasing its strength, reliability, and heat resistance while preventing short circuits and reducing eddy current losses.

Implementation Method 1

the insulating property of the soft magnetic material is a problem. In particular, when the magnetic material and the coil conductor are directly in contact with each other, a short circuit occurs

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Implementation Method 2

the epoxy resin has an epoxy value of 150 or less... the epoxy resin is filled in gap spaces between the soft magnetic particles

Methodology Applied

Scientific EffectCross-linking: Chemical Bonding

Data Source

PatentUS12300409B2Multilayer coil device and method of manufacturing the same

Publication Date: 2025.05.13 TDK CORP

AI summary

A multilayer coil device includes an element formed by laminating a coil conductor and a magnetic element body. The magnetic element body includes soft magnetic particles and an epoxy resin. The soft magnetic particles include soft magnetic metal particles. The epoxy resin has an epoxy value of 150 or less. The epoxy resin is filled in gap spaces between the soft magnetic particles.