Fe-Si Magnetic Particle Oxide Coating for Inductor Insulation
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Solution Overview
Problem
Existing methods for improving insulation properties of metal magnetic particles used in power inductors face challenges such as non-uniform film formation, dielectric breakdown, and insufficient insulation reliability, particularly when forming insulating films like glass or oxide layers, which also limit high-temperature heat treatment.
Innovation Solution
A multi-layer oxide coating is applied to alloy particles containing Fe and Si, comprising first, second, third, and fourth oxide layers with specific thicknesses and crystallinity, formed through a process involving Si alkoxide, alcohol, and heat treatment in an oxidizing atmosphere, enhancing insulation and direct-current superposition characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single insulating film is formed on metal magnetic particles, then insulation properties are improved, but film uniformity deteriorates leading to dielectric breakdown
Solution Approach 1:
The insulating film is divided into multiple layers (first insulating film and second insulating film) with different thicknesses and material compositions. The first insulating film has a smaller thickness and the second insulating film has a larger thickness, creating a segmented structure that improves both insulation reliability and film formation uniformity while preventing dielectric breakdown.
2Reliability
If high temperature heat treatment is performed, then magnetic properties are improved, but oxidation of raw material particles progresses
Solution Approach 1:
The first insulating film is formed on the metal magnetic particles before heat treatment in advance to create a protective barrier. This preliminary action prevents oxidation of the raw material particles during subsequent high-temperature heat treatment while allowing the magnetic properties to be improved.
Solution Approach 2:
The first insulating film acts as an intermediary protective layer between the metal magnetic particles and the oxidizing atmosphere during heat treatment. This intermediary layer allows high-temperature heat treatment to proceed while preventing harmful oxidation of the raw material particles.
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 multi-layer oxide coating significantly improves the insulation resistance and direct-current superposition characteristics of metal magnetic particles, resulting in high withstand voltage and excellent direct-current superposition performance in inductors.
Implementation Method 1
forming a coating film forming particle formed with a coating film containing silicon oxide by hydrolyzing drying the Si alkoxide
Implementation Method 2
forming an oxide layer on the surface of the alloy particle by performing heat treatment on the coating film forming particle in an oxidizing atmosphere
Data Source
AI summary
A metal magnetic particle provided with an oxide layer on a surface of an alloy particle containing Fe and Si. The oxide layer has a first oxide layer, a second oxide layer, a third oxide layer, and a fourth oxide layer. Also, in line analysis of element content by using a scanning transmission electron microscope-energy dispersive X-ray spectroscopy, the first oxide layer is a layer where Fe content takes a local maximum value, the second oxide layer is a layer where Fe content takes a local maximum value, the third oxide layer is a layer where Si content takes a local maximum value, and the fourth oxide layer is a layer where Fe content takes a local maximum value.