Soft Magnetic Material Uniform Particle Distribution DC Bias
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Solution Overview
Problem
Dust cores exhibit inferior DC bias characteristics compared to magnetic steel sheets due to magnetic saturation, leading to inductance drops with increasing DC current, which is not adequately addressed by existing manufacturing methods that only specify particle size ranges without ensuring uniformity.
Innovation Solution
A soft magnetic material with metal magnetic particles having a coefficient of variation of 0.40 or less and circularity of 0.80 or more, along with the addition of metallic soap or inorganic lubricants, is used to improve particle uniformity and reduce surface distortions, enhancing DC bias characteristics and flowability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dust cores are used as an alternative to magnetic steel sheets, then device complexity is reduced and ease of manufacture is improved, but DC bias characteristics deteriorate due to magnetic saturation causing inductance drops
Solution Approach 1:
The invention changes the particle size parameters of the magnetic powder, specifically controlling the average particle size to 10 μm or more and the coefficient of variation to 0.45 or less. This parameter optimization prevents magnetic saturation by ensuring uniform particle distribution, thereby improving DC bias characteristics while maintaining the manufacturing advantages of dust cores
Solution Approach 2:
The invention emphasizes homogeneity in particle size distribution by requiring a coefficient of variation of 0.45 or less. This homogeneous distribution prevents localized magnetic saturation and ensures uniform magnetic properties throughout the core, resolving the DC bias characteristic deterioration issue
2Manufacturing precision
If only particle size range is specified without uniformity control, then manufacturing precision requirements are relaxed, but DC bias characteristics deteriorate due to non-uniform particle distribution causing magnetic saturation
Solution Approach 1:
The invention introduces a specific parameter control for particle size uniformity by limiting the coefficient of variation to 0.45 or less. This quantitative parameter specification ensures uniform particle distribution without overly complicating the manufacturing process, achieving both manufacturability and improved DC bias characteristics
Solution Approach 2:
The invention replaces complex mechanical mixing processes with controlled particle size distribution as the primary mechanism for achieving uniformity. By substituting process complexity with material specification, the invention achieves homogeneous particle distribution that prevents magnetic saturation
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 solution achieves improved DC bias characteristics by ensuring uniform particle distribution and reduced surface distortions, leading to better magnetization domain wall motion and increased density of the compacted material, effectively reducing inductance drops and eddy current losses.
Implementation Method 1
the uniformity of the inside of a compact made of the soft magnetic material by compacting can be improved. This can facilitate the domain wall motion in a magnetization process and improve DC bias characteristics
Implementation Method 2
an inductance drop with an increase in a DC current is caused by magnetic saturation of soft magnetic materials. Specifically, the magnetic field applied to soft magnetic materials becomes large with increasing DC current. Consequently, magnetic saturation decreases magnet permeability.
Data Source
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Figure 4B~5
AI summary
A soft magnetic material, a dust core, a method for manufacturing the soft magnetic material, and a method for manufacturing the dust core that can improve DC bias characteristics are provided. A soft magnetic material includes a plurality of metal magnetic particles 10 whose coefficient of variation Cv (σ/µ), which is a ratio of a standard deviation (σ) of a particle size of the metal magnetic particles 10 to an average particle size (µ) thereof, is 0.40 or less and whose circularity Sf is 0.80 or more and 1 or less. The metal magnetic particles 10 preferably have an average particle size of 1 µm or more and 70 µm or less. The soft magnetic material preferably further includes an insulating coated film that surrounds a surface of each of the metal magnetic particles 10.