Fe-Si-Al Flaky Powder for Thin Magnetic Sheets
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Solution Overview
Problem
The challenge lies in forming thin magnetic sheets with high magnetic permeability using flaky soft magnetic powder, as traditional methods result in poor alignment, sparse and dense portions, reduced magnetic permeability, and increased coercive force due to strain, making it difficult to achieve sheets with thicknesses of 50 μm or less for mobile electronic devices.
Innovation Solution
A flaky soft magnetic powder with specific composition (Fe—Si—Al alloy) and production methods, including atomization, flattening, and heat-treatment under vacuum or inert gas, to achieve optimal average particle size, tap density, and coercive force, ensuring superior sheet formability and high magnetic permeability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If flaky soft magnetic powder with large major-axis length is used to reduce demagnetizing field and improve magnetic permeability, then magnetic permeability is improved, but sheet formability deteriorates due to poor alignment and formation of sparse and dense portions
Solution Approach 1:
The invention changes the particle size parameter by controlling the average particle size D50 to be 7 μm or more but 60 μm or less, and controls the aspect ratio to be 1.05 or more but 5 or less. These parameter optimizations balance the magnetic permeability improvement with sheet formability, preventing both poor alignment and excessive strain during sheet formation.
Solution Approach 2:
The invention applies a moderate aspect ratio (1.05-5) rather than maximizing it excessively. This partial action approach ensures sufficient magnetic permeability improvement while avoiding the excessive strain and alignment problems that would occur with much larger aspect ratios.
2Ease of manufacture
If pressing process is applied to improve sheet formability and reduce surface irregularities, then sheet formability is improved, but coercive force increases due to strain introduction in powder
Solution Approach 1:
The invention optimizes the particle size parameter (D50: 7-60 μm) and aspect ratio (1.05-5) to reduce the strain introduced during pressing. This parameter optimization allows the powder to better withstand the pressing process, maintaining low coercive force while improving sheet formability.
3Ease of manufacture
If low filling ratio of powder is used to improve sheet formability, then sheet formability is improved, but magnetic permeability of sheet is reduced
Solution Approach 1:
The invention optimizes the particle size (D50: 7-60 μm) and aspect ratio (1.05-5) to improve powder flowability and packing efficiency. This allows achieving high filling ratios without compromising sheet formability, thereby maintaining high magnetic permeability while ensuring good sheet 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 resulting powder enhances magnetic permeability, reduces energy loss, and improves communication range in antennas for RFID applications by maintaining a large real part and small imaginary part of magnetic permeability, while maintaining sheet formability and reducing surface irregularities.
Implementation Method 1
the entire disclosure of which is incorporated herein by reference. TECHNICAL FIELD [0002]The present invention relates to a flaky soft magnetic powder for use in an antenna for 10 MHz or thereabouts, such as an antenna for radio frequency identification (RFID). The present invention also relates to a method of producing the flaky soft magnetic powder.
Implementation Method 2
JP2011-22661A (Patent Document 1) discloses an electromagnetic induction-type digitizer including a pen-shaped position indicator and a panel-shaped position detector wherein a high-frequency signal transmitted from a coil embedded in the tip of the position indicator is read by a loop coil embedded in the position detector
Implementation Method 3
A flaky soft magnetic powder with specific composition (Fe—Si—Al alloy) and production methods, including atomization, flattening, and heat-treatment under vacuum or inert gas
Implementation Method 4
the latter process leads to application of a large stress to the powder in the sheet, resulting in introduction of strain into the powder. The introduction of strain increases the coercive force Hc of the powder and reduces the magnetic permeability of the powder
Data Source
AI summary
Provided is a flaky soft magnetic powder composed of an Fe—Si—Al alloy containing Si: 5.5 to 10.5 mass %, Al: 4.5 to 8.0 mass %, and Fe and incidental impurities: balance, wherein the flaky powder exhibits a ratio (D50/TD) of 35 to 92 where D50 represents the average particle size (μm) of the powder and TD represents the tap density (Mg/m3) of the powder, and the flaky powder exhibits a coercive force of 239 to 479 A/m as measured under application of a magnetic field in an in-plane direction of the flaky powder. The flaky soft magnetic powder exhibits superior sheet formability and has high magnetic permeability.