Soft Magnetic Flaky Powder Coating for Thin Sheet Formability
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Solution Overview
Problem
Conventional soft magnetic flaky powders face challenges in achieving high electrical resistance and corrosion resistance, particularly when used in thin magnetic sheets for noise suppression in electronic devices, due to issues with sheet formability and permeability at thicknesses of 50 μm or less, leading to reduced performance and increased coercive force.
Innovation Solution
A soft magnetic flaky powder with an Fe-based alloy and a coating layer comprising chromic acid, metal salts, and inorganic acids, having a thickness of 10 nm or more and 200 nm or less, an aspect ratio of 10 to 40, and a specific particle size distribution, which enhances electrical resistance and corrosion resistance while maintaining permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a soft magnetic flaky powder with high aspect ratio and large particle diameter is used to achieve high permeability, then the permeability is improved, but the sheet formability deteriorates when producing thin magnetic sheets (50 μm or less)
Solution Approach 1:
The patent applies parameter changes by controlling the aspect ratio within 10-40 and particle diameter D50 within 20-60 μm, along with specific tap density (0.6-1.5 Mg/m³) and thickness (0.5-5 μm) parameters. These optimized parameters enable the powder to maintain high permeability while achieving good sheet formability for thin magnetic sheets of 50 μm or less, resolving the contradiction between permeability and manufacturability.
2Ease of manufacture
If the powder filling rate is lowered or pressing is performed to improve sheet formability, then the sheet can be molded properly, but the permeability is lowered and performance is reduced
Solution Approach 1:
The patent resolves this contradiction by optimizing multiple parameters simultaneously: aspect ratio (10-40), particle diameter D50 (20-60 μm), tap density (0.6-1.5 Mg/m³), and thickness (0.5-5 μm). These parameter changes enable high powder filling rates to be achieved without compromising sheet formability, thus maintaining high permeability while ensuring proper sheet molding.
3Ease of manufacture
If excessive stress is applied during pressing to improve sheet formability, then the sheet can be molded, but distortion is introduced to the powder and coercive force increases, reducing permeability
Solution Approach 1:
The patent applies parameter changes by optimizing the aspect ratio (10-40) and particle morphology through controlled flattening processes. These parameter changes enable the powder to be densely packed at high filling rates without requiring excessive pressing stress, thus avoiding distortion and maintaining low coercive force and high permeability while achieving good sheet formability.
4Reliability
If a coating layer with thickness of 10 nm or more is formed on the Fe-based alloy flaky particle, then electrical resistance and corrosion resistance are improved, but the aspect ratio and particle size are constrained
Solution Approach 1:
The patent applies parameter changes by forming a coating layer with controlled thickness of 10 nm or more (preferably 20-200 nm) on Fe-based alloy flaky particles. This coating layer improvement enhances electrical resistance and corrosion resistance while the patent simultaneously maintains aspect ratio within 10-40 and particle diameter D50 within 20-60 μm through optimized flattening and classification processes, thus resolving the contradiction between protection and precision control.
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 proposed soft magnetic flaky powder and magnetic sheet exhibit improved electrical resistance, corrosion resistance, and noise suppression performance, particularly at the 1 MHz band, suitable for thin magnetic sheets in electronic devices like smartphones and tablets.
Implementation Method 1
a coating layer which has a thickness of 10 nm or more
Implementation Method 2
a coating layer formed on a surface of the Fe-based alloy flaky particle; the coating layer comprises one or two or more components selected from the group consisting of chromic acid and a hydrate thereof, a metal salt of acetic acid and a hydrate thereof, and a metal salt of an inorganic acid and a hydrate thereof
Implementation Method 3
it is important to use a soft magnetic powder having high permeability for obtaining a magnetic sheet having high permeability, and to use a flaky powder having a high aspect ratio in the magnetization direction for reducing the demagnetizing field
Data Source
AI summary
In order to provide a soft magnetic flaky powder having high electrical resistance and high corrosion resistance, and a magnetic sheet including the same, the present invention provides a soft magnetic flaky powder, including a plurality of soft magnetic flaky particles. Each of the plurality of soft magnetic flaky particles contains an Fe-based alloy flaky particle and a coating layer formed on a surface of the Fe-based alloy flaky particle. The coating layer contains one or two or more components selected from chromic acid and a hydrate thereof, and a metal salt of an inorganic acid and a hydrate thereof. The inorganic acid is selected from sulfuric acid, nitric acid, chromic acid, phosphoric acid, hydrofluoric acid and acetic acid. The metal salt is selected from a Na salt, an Al salt, a Ti salt, a Cr salt, a Ni salt, a Ga salt and a Zr salt. The coating layer has a thickness of 10 nm or more.