US-12626849-B2 - Coil component

US12626849B2US 12626849 B2US12626849 B2US 12626849B2US-12626849-B2

Abstract

A coil component includes an element assembly including a coil conductor formed by winding a conductor coated with an electrically insulating film and a magnetic portion containing metal magnetic particles and resin, and an outer electrode electrically connected to an exposed surface of an extended part of the coil conductor, exposed on a surface of the element assembly and disposed on the surface of the element assembly. The metal magnetic particles include first and second metal magnetic particles. A particle size distribution of the metal magnetic particles, calculated in accordance with a circle equivalent diameter obtained from a cross-sectional image in a cross section of the magnetic portion, has at least two peaks and at least one bottom. The large magnetic particles are larger than or equal to the bottom having a minimum frequency.

Inventors

Keiichi Ishida

Assignees

MURATA MANUFACTURING CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20230324
Priority Date: 20220329

Claims (20)

1 . A coil component comprising: an element assembly including a coil conductor including a wound conductor, and a magnetic portion containing metal magnetic particles and resin; and an outer electrode electrically connected to an exposed surface of an extended part of the coil conductor, exposed on a surface of the element assembly, and on the surface of the element assembly, wherein the metal magnetic particles include first metal magnetic particles, second metal magnetic particles, and third metal magnetic particles, a particle size distribution of the metal magnetic particles, calculated in accordance with a circle equivalent diameter obtained from a cross-sectional image in a cross section of the magnetic portion, has at least two peaks and at least one bottom, and metal magnetic particles larger than or equal to the bottom having a minimum frequency are defined as large metal magnetic particles, those of the large metal magnetic particles having a recessed portion that satisfies a predetermined condition in the cross section are defined as the second metal magnetic particles, those of the large metal magnetic particles not having the recessed portion are defined as the first metal magnetic particles, those of the metal magnetic particles smaller than the bottom having the minimum frequency are defined as the third metal magnetic particles, and the predetermined condition is L 02 >L 01 , where a minimum distance between distal ends at an opening of the recessed portion is L 01 , and a longest distance of line segments parallel to a line segment that has the minimum distance between the distal ends of the opening in line segments corresponding to chords in the recessed portion of a cross section of each of the second metal magnetic particles is L 02 .
2 . The coil component according to claim 1 , wherein a mean particle size of the first metal magnetic particles is greater than a mean particle size of the second metal magnetic particles.
3 . The coil component according to claim 1 , wherein a mean particle size of the first metal magnetic particles is from 10 μm to 50 μm.
4 . The coil component according to claim 1 , wherein a mean particle size of the third metal magnetic particles is from 0.2 μm to 10 μm.
5 . The coil component according to claim 1 , wherein each of the first metal magnetic particles and each of the second metal magnetic particles have the same composition.
6 . The coil component according to claim 1 , wherein an electrically insulating coating is on an outer surface of each of the second metal magnetic particles, and an electrically insulating coating is absent from at least part of a surface inside the recessed portion of each of the second metal magnetic particles.
7 . The coil component according to claim 1 , wherein in the cross section of the magnetic portion, a content of the resin is from 5% to 25% in area.
8 . The coil component according to claim 1 , wherein where a total content of the first metal magnetic particles, the second metal magnetic particles, and the third metal magnetic particles is 100% in area, a content of the first metal magnetic particles is from 40% to 80%, a content of the second metal magnetic particles is from 2% to 40%, and a content of the third metal magnetic particles is from 10% to 30%.
9 . The coil component according to claim 1 , wherein at least part of at least one of the third metal magnetic particles is inside the recessed portion of at least one of the second metal magnetic particles.
10 . The coil component according to claim 1 , wherein a whole of at least one of the third metal magnetic particles is inside the recessed portion of at least one of the second metal magnetic particles.
11 . The coil component according to claim 1 , wherein when a whole of at least one of the third metal magnetic particles is inside the recessed portion of at least one of the second metal magnetic particles in the cross section of the magnetic portion, a content of the third metal magnetic particles inside the recessed portion is higher than or equal to 40% on average.
12 . The coil component according to claim 1 , wherein in the cross section of the magnetic portion, at least part of at least one of other second metal magnetic particles and at least part of the third metal magnetic particles are inside the recessed portion of at least one of the second metal magnetic particles, and a content of the other second metal magnetic particles and the third metal magnetic particles in the recessed portion of the second metal magnetic particles is higher than or equal to 50% on average.
13 . The coil component according to claim 1 , wherein where a particle size at which a peak having a maximum frequency is located in a particle size distribution of the third metal magnetic particles is d 3 , an average value of the minimum distance L 01 between the distal ends at the opening of the recessed portion of each of the second metal magnetic particles in the cross section of the magnetic portion satisfies L 01 >d 3 .
14 . The coil component according to claim 1 , wherein where an outer perimeter of the second metal magnetic particle having the recessed portion is L 1 and a perimeter of a circle having an equivalent circle area is L 2 in the cross section of the magnetic portion, an average value of L 1 /L 2 is less than or equal to 5.0.
15 . The coil component according to claim 1 , wherein where the minimum distance between the distal ends at the opening of the recessed portion of each of the second metal magnetic particles is L 01 and a perimeter other than an inside of the opening of the recessed portion of each of the second metal magnetic particles is Lc in the cross section of the magnetic portion, an average value of L 01 /(Lc+L 01 ) is from 0.03 to 0.4.
16 . The coil component according to claim 1 , wherein where an area of a region inside the line segment that has the minimum distance between the distal ends at the opening of each of the second metal magnetic particles is S 0 and a cross-sectional area of each of the second metal magnetic particles having the recessed portion is Sc in the cross section of the magnetic portion, an average value of S 0 /(Sc+S 0 ) is from 0.05 to 0.8.
17 . The coil component according to claim 1 , wherein the magnetic portion further contains inorganic oxide particles.
18 . The coil component according to claim 17 , wherein in the cross section of the magnetic portion, at least part of at least one of the third metal magnetic particles and at least part of at least one of the inorganic oxide particles are in the recessed portion of at least one of the second metal magnetic particles.
19 . The coil component according to claim 17 , wherein the inorganic oxide particles are glass.
20 . The coil component according to claim 17 , wherein the inorganic oxide particles are ferrite.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims benefit of priority to Japanese Patent Application No. 2022-054179, filed Mar. 29, 2022, the entire content of which is incorporated herein by reference. BACKGROUND Technical Field The present disclosure relates to a coil component. Background Art As an existing coil component (reactor), a main body portion of the coil component is made up of a magnetic core and a coil. The magnetic core is made of a composite material obtained by mixing metal magnetic particles with resin. The composite material of the magnetic core is manufactured from a soft magnetic composite material. The soft magnetic composite material according to an existing technology has such a drawback that the magnetic permeability is low and, as a result, the inductance of a reactor manufactured from the soft magnetic composite material is low. In the existing technology, a method is configured to mix metal magnetic particles with resin in advance and then to form the mixed material into a designated shape. Therefore, there is a drawback that the amount of resin used to the amount of metal magnetic particles used increases. This leads to a decrease in the magnetic permeability of the obtained soft magnetic composite material, with the result that direct-current superposition characteristics undesirably deteriorate due to a decrease in density. For this reason, there has been suggested a technology for making it possible to increase the density of obtained soft magnetic composite material by adding second particles with a smaller mean particle size to first particles with a high circularity and a large mean particle size to bury gaps between the particles. Thus, the magnetic core formed from the soft magnetic composite material has a high magnetic permeability, and the inductance of the reactor using the magnetic core can be improved, as described, for example, in Japanese Unexamined Patent Application Publication No. 2016-039331. However, the soft magnetic composite material used for the magnetic core of the reactor described in Japanese Unexamined Patent Application Publication No. 2016-039331 uses a particle size having a high circularity, for example, a particle size of 100 μm to 200 μm, so the magnetic permeability increases, while, on the other hand, there are concerns about an issue that a loss increases in a radio-frequency range. SUMMARY Therefore, the present disclosure provides a coil component that provides a high magnetic permeability and that has good radio-frequency characteristics. A coil component according to the disclosure includes an element assembly including a coil conductor formed by winding a conductor and a magnetic portion containing metal magnetic particles and resin, and an outer electrode electrically connected to an exposed surface of an extended part of the coil conductor, exposed on a surface of the element assembly, and disposed on the surface of the element assembly. The metal magnetic particles include first metal magnetic particles, second metal magnetic particles, and third metal magnetic particles. A particle size distribution of the metal magnetic particles, calculated in accordance with a circle equivalent diameter obtained from a cross-sectional image in a cross section of the magnetic portion, has at least two peaks and at least one bottom. The metal magnetic particles larger than or equal to the bottom having a minimum frequency are defined as large metal magnetic particles. Of the large metal magnetic particles, metal magnetic particles each having a recessed portion that satisfies a predetermined condition in the cross section are defined as the second metal magnetic particles. Of the large metal magnetic particles, metal magnetic particles each not having the recessed portion are defined as the first metal magnetic particles. Metal magnetic particles smaller than the bottom having the minimum frequency are defined as the third metal magnetic particles. The predetermined condition is L02>L01 where a minimum distance between distal ends at an opening of the recessed portion is L01 and a longest distance of line segments parallel to a line segment that has the minimum distance between the distal ends at the opening in line segments corresponding to chords in the recessed portion, circular in cross section, of each of the second metal magnetic particles is L02. With the coil component according to the disclosure, the metal magnetic particles contained in the magnetic portion are configured as follows. The particle size distribution of the metal magnetic particles, calculated in accordance with the circle equivalent diameter obtained from the cross-sectional image in the cross section of the magnetic portion, has at least two peaks and at least one bottom. The metal magnetic particles larger than or equal to the bottom having the minimum frequency are defined as large metal magnetic particles. The metal magnetic particles include the followin