US-12626847-B2 - Magnetic core and magnetic component

US12626847B2US 12626847 B2US12626847 B2US 12626847B2US-12626847-B2

Abstract

A magnetic core, containing metal magnetic powder and resin, in which a content of the metal magnetic powder satisfies 60%≤(A1/A2)≤90%. The metal magnetic powder includes small particles having the Heywood diameter of 1 μm or less in the cross section of the magnetic core and large particles having the Heywood diameter of 5 μm or more and less than 40 μm. An edge-to-edge distance regarding to a distance between the small particles satisfies 5≤((L1av/dav)×100)≤70. An edge-to-edge distance regarding to a distance between the small particles and the large particles satisfies 0.02 μm≤L2av≤0.13 μm and σ≤0.25 μm.

Inventors

Seigo Tokoro
Kazuhiro YOSHIDOME
Akito HASEGAWA
Nobuhiro Okuda

Assignees

TDK CORPORATION

Dates

Publication Date: 20260512
Application Date: 20230215
Priority Date: 20220221

Claims (4)

1 . A magnetic core, comprising: metal magnetic powder; and resin, wherein a content of the metal magnetic powder satisfies 60%≤(A1/A2)≤90%, in which A1 is an area of the metal magnetic powder in a cross section of the magnetic core, and A2 is a total area of the metal magnetic powder and the resin in the cross section of the magnetic core, the metal magnetic powder includes small particles having the Heywood diameter of 1 μm or less in the cross section of the magnetic core and large particles having the Heywood diameter of 5 μm or more and less than 40 μm, a neighborhood region of each small particle is defined as a region within a circle with a radius of 3×r N from a centroid of each small particle as a center of the circle in the cross section of the magnetic core, in which r N is a radius of each of the small particles, L1 is defined as an edge-to-edge distance between the small particle positioned in a center of the neighborhood region of each small particle and the small particle farthest from the center in the neighborhood region of each small particle, a ratio of L1av to day satisfies 5≤((L1av/dav)×100)≤70, in which L1av is an average value of L1 and dav is an average value of the Heywood diameters of the small particles, L2 is defined as an edge-to-edge distance between a randomly selected large particle in the cross section of the magnetic core and a small particle adjacent to the randomly selected large particle, L2av is 0.02 μm or more and 0.13 μm or less, in which L2av is an average value of L2, and σ is 0.25 μm or less, in which σ is a standard deviation of L2.
2 . The magnetic core according to claim 1 , wherein an average roundness of the large particles in the cross section of the magnetic core is 0.8 or more.
3 . The magnetic core according to claim 1 , wherein a ratio of S1 to S2 satisfies 0.2≤(S1/S2)≤0.5, in which S1 is an area of the small particles in the cross section of the magnetic core, and S2 is an area of the large particles in the cross section of the magnetic core.
4 . A magnetic component comprising the magnetic core according to claim 1 .

Description

TECHNICAL FIELD The present disclosure relates to a magnetic core and a magnetic component. BACKGROUND Magnetic components such as inductors, transformers, and choke coils are widely used in power supply circuits of various electronic devices. In recent years, in order to realize a low-carbon society, reduction of energy loss in power supply circuits and improvement of power supply efficiency are considered important, and higher efficiency and energy saving of magnetic components are required. In order to satisfy the above requirements for the magnetic component, it is essential to improve relative magnetic permeability of a magnetic core included in the magnetic component. In order to improve the relative magnetic permeability of the magnetic core, it is necessary to increase a packing rate of magnetic powder contained in the magnetic core. Therefore, in the field of magnetic components, various attempts are made to improve the packing rate of the magnetic powder in the magnetic core. For example, Patent Document 1 discloses that a packing density of the magnetic powder can be increased by adjusting an edge-to-edge distance between large particles and a distance between centroids of coarse particles within predetermined ranges. However, increasing the packing rate of the magnetic powder increases the number of contact points between magnetic particles, which tends to lower a withstand voltage of the magnetic core. The increase in the number of contact points between the magnetic particles causes local magnetic saturation, and degrades DC bias characteristics. In other words, there is a trade-off relation between the packing rate (relative magnetic permeability) and the withstand voltage and the DC bias characteristics, and it is difficult to improve both the withstand voltage characteristics and the DC bias characteristics in a state where the packing rate (relative magnetic permeability) is high. Patent Document 1: JP2021176167 (A) SUMMARY The present disclosure has been achieved in view of the above circumstances, and an object of the present disclosure is to provide a magnetic core having both a high withstand voltage and excellent DC bias characteristics, and a magnetic component including the magnetic core. In order to achieve the above object, a magnetic core according to the present disclosure contains: metal magnetic powder; and resin, in whicha content of the metal magnetic powder satisfies 60%≤(A1/A2)≤90%, in which A1 is an area of the metal magnetic powder in a cross section of the magnetic core, and A2 is a total area of the metal magnetic powder and the resin in the cross section of the magnetic core,the metal magnetic powder includes small particles having the Heywood diameter of 1 μm or less in the cross section of the magnetic core and large particles having the Heywood diameter of 5 μm or more and less than 40 μm,a neighborhood region of each small particle is defined as a region within a circle with a radius of 3×rN from a centroid of each small particle as a center of the circle in the cross section of the magnetic core, in which rN is a radius of each of the small particles,L1 is defined as an edge-to-edge distance between the small particle positioned in a center of the neighborhood region of each small particle and the small particle farthest from the center in the neighborhood region of each small particle,a ratio of L1av to day satisfies 5≤((L1av/dav)×100)≤70, in which L1av is an average value of L1 and dav is an average value of the Heywood diameters of the small particles,L2 is defined as an edge-to-edge distance between a randomly selected large particle in the cross section of the magnetic core and a small particle adjacent to the randomly selected large particle,L2av is 0.02 μm or more and 0.13 μm or less, in which L2av is an average value of L2, andσ is 0.25 μm or less, in which σ is a standard deviation of L2. Since the magnetic core has the above feature, it is possible to improve the withstand voltage and the DC bias characteristics as compared with magnetic cores in the related art while maintaining a high relative magnetic permeability thereof. Preferably, an average roundness of the large particles in the cross section of the magnetic core is 0.8 or more. Preferably, a ratio of S1 to S2 satisfies 0.2≤(S1/S2)≤0.5, in which S1 is an area of the small particles in the cross section of the magnetic core, and S2 is an area of the large particles in the cross section of the magnetic core. The magnetic core of the present disclosure can be applied to various magnetic components such as inductors, transformers, and choke coils. BRIEF DESCRIPTION OF THE DRAWING(S) FIG. 1 is a schematic cross-sectional view showing a magnetic core according to an embodiment of the present disclosure; FIG. 2 is a schematic diagram showing an example of particle size distribution of metal magnetic powder contained in the magnetic core of FIG. 1; FIG. 3A is a schematic diagram showing a cross section