Coil component

Abstract

To provide a coil component that suppresses concentration of a magnetic flux near an end part in a height direction of an inner circumferential surface of a coil conductor of a base body.SOLUTION: A coil component 1 includes a base 10 and a coil conductor. The coil conductor includes a winding portion 25a wound around a coil axis Ax inside the base. The base has: a core portion C1 located inside the winding portion in a radial direction centered on the coil axis; a first low permeability portion 12a covering one end face of the winding portion; and a second low permeability portion 12b covering the other end face of the winding portion. The first low permeability portion has a first relative permeability lower than the core center relative permeability of a core center portion C2 located at the center in the axial direction of the core portion. The second low permeability portion has a second relative permeability lower than the core center relative permeability of the core portion.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The technology disclosed in this specification relates to coil components.

Background Art

[0002] Conventionally, a coil component including a substrate made of a magnetic material, an external electrode provided on the surface of the substrate, and a coil conductor extending around a coil axis within the substrate has been known.

[0003] One example of a coil component is an inductor. An inductor is a passive element used in an electronic circuit. The inductor is used, for example, to remove noise in a power line or a signal line.

[0004] Japanese Patent Application Laid-Open No. 2018-121023 describes an inductor in which a magnetic gap layer is provided in a substrate in order to suppress magnetic saturation in the substrate and improve DC superposition characteristics.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] With the miniaturization of electronic devices, further thinning (low-profile) of the coil components mounted on the electronic components is required.

[0007] The inventor has discovered that when the coil component is made low-profile, magnetic flux concentration significantly occurs in a region near the end in the height direction of the inner peripheral surface of the coil conductor in the substrate. When magnetic flux is concentrated in a part of the substrate, there is a problem that magnetic loss increases at the site where the magnetic flux is concentrated.

[0008] One object of the invention disclosed in this specification is to provide a coil component capable of suppressing concentration of magnetic flux in the vicinity of an end portion in the height direction of the inner peripheral surface of a coil conductor in a base body.

[0009] The objects of the invention disclosed in this specification other than those described above will be clarified through the description of the entire specification. The invention described in the claims may solve problems other than those grasped from the "problems to be solved by the invention".

Means for Solving the Problems

[0010] A coil component according to one embodiment includes a base body and a coil conductor. The coil conductor has a circumferential portion wound around a coil axis inside the base body. The base body has a core portion inside the circumferential portion in the radial direction centered on the coil axis, a first low magnetic permeability portion covering one end surface of the circumferential portion, and a second low magnetic permeability portion covering the other end surface of the circumferential portion. The core portion has a core center portion at the center in the axial direction. The first low magnetic permeability portion has a first relative magnetic permeability lower than the core center portion relative magnetic permeability of the core center portion. The second low magnetic permeability portion has a second relative magnetic permeability lower than the core center portion relative magnetic permeability of the core center portion.

Effects of the Invention

[0011] According to the embodiment of the invention disclosed by this specification, it is possible to provide a coil component capable of suppressing concentration of magnetic flux in the vicinity of an end portion in the height direction of the inner peripheral surface of a coil conductor in a base body.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3a

Figure 3b

Figure 3c

Figure 3d

Figure 3e

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0013] Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. The same reference numerals are assigned to the common components in the plurality of drawings. Note that each drawing is not necessarily drawn to an exact scale for the sake of convenience of explanation. The embodiments of the present invention described below do not necessarily limit the invention according to the claims. The elements described in the following embodiments are not necessarily essential for the solution means of the invention.

[0014] 1 First Embodiment 1-1 Basic Structure of Coil Component With reference to FIG. 1, the basic structure of the coil component 1 according to the first embodiment will be described. FIG. 1 is a perspective view of the coil component 1 according to the first embodiment.

[0015] The coil component 1 is a passive element used in an electronic circuit. The coil component 1 is used, for example, to remove noise in a power line or a signal line.

[0016] The coil component 1 shown in FIG. 1 includes a base 10, a coil conductor 25 provided on the base 10, a first external electrode 21 connected to one end of the coil conductor 25, and a second external electrode 22 connected to the other end of the coil conductor 25.

[0017] The coil component 1 can be mounted on a circuit board (not shown). A land portion is provided on the circuit board. The coil component 1 is mounted on the mounting board by joining the first external electrode 21 and the second external electrode 22 to the land portion. The circuit board on which the coil component 1 is mounted can be mounted on various electronic devices. Electronic devices on which the circuit board can be mounted include smartphones, tablets, game consoles, automotive electrical components, servers, and various other electronic devices.

[0018] 1-2 Basic Structure of the Base 10 In one aspect, the base 10 is formed in a rectangular parallelepiped shape from an insulating material. For example, the dimension (length dimension) of the coil component 1 in the L-axis direction is in the range of 0.5 mm to 6.0 mm, the dimension (width dimension) in the W-axis direction is in the range of 0.3 mm to 4.5 mm, and the dimension (height dimension) in the T-axis direction is in the range of 0.3 mm to 3.0 mm. In one aspect, the height dimension of the base 10 is smaller than either the length dimension or the width dimension. The height dimension of the base 10 may be less than 1.0 mm. In this specification, the term "rectangular parallelepiped" or "rectangular parallelepiped shape" does not mean only a "rectangular parallelepiped" in a strictly mathematical sense. As will be described later, the corners and / or sides of the base 10 may be curved. The dimensions and shape of the base 10 are not limited to those explicitly stated in this specification.

[0019] The base body 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f. The first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f are all connected to the first main surface 10a and the second main surface 10b. Further, the first end surface 10c connects the first side surface 10e and the second side surface 10f. The second end surface 10d also connects the first side surface 10e and the second side surface 10f. The first main surface 10a and the second main surface 10b respectively form the surfaces at both ends in the height direction of the base body 10, the first end surface 10c and the second end surface 10d respectively form the surfaces at both ends in the length direction of the base body 10, and the first side surface 10e and the second side surface 10f respectively form the surfaces at both ends in the width direction of the base body 10. As shown in FIG. 1, since the first main surface 10a is on the lower side of the base body 10, the first main surface 10a may be referred to as the "lower surface" or the "bottom surface". Similarly, the second main surface 10b may be referred to as the "upper surface".

[0020] In the illustrated embodiment, a first external electrode 21 and a second external electrode 22 are provided on the first main surface 10a of the base body 10. When mounting the coil component 1 on the mounting substrate, the first main surface 10a is arranged to face the mounting substrate. For this reason, the first main surface 10a of the base body 10 may also be referred to as the "mounting surface". At least one of the first external electrode 21 and the second external electrode 22 may extend to a surface other than the lower surface 10a of the base body 10. For example, the first external electrode 21 may extend so as to be in contact with not only the lower surface 10a but also the first end surface 10c.

[0021] The distance between the lower surface 10a and the upper surface 10b is separated by the height dimension of the base body 10, the distance between the first end surface 10c and the second end surface 10d is separated by the length dimension of the base body 10, and the distance between the first side surface 10e and the second side surface 10f is separated by the width dimension of the base body 10. In this specification, unless otherwise understood in the context, the "length" direction, "width" direction, and "thickness" direction of the coil component 1 are respectively the L-axis direction, W-axis direction, and T-axis direction in FIG. 1.

[0022] The base body 10 is made of an insulating material with excellent insulating properties. The base body 10 may be made of a magnetic material. The base body 10 may contain a plurality of metal magnetic particles. The metal magnetic particles contained in the base body 10 may be (1) metallic Fe or Ni, (2) alloy-based Fe-Si-Cr, Fe-Si-Al or Fe-Ni, (3) amorphous Fe-Si-Cr-B-C or Fe-Si-B-Cr, or (4) particles of a mixed material thereof. As the material of the base body 10, a composite magnetic material in which magnetic particles are dispersed in a resin, a ferrite material, or any other known magnetic material other than these can be used.

[0023] 1-3 Basic structure of the coil conductor 25 The coil conductor 25 has a circumferential portion 25a, a first lead-out portion 25b, a second lead-out portion 25c, a first connection portion 25d connecting one end of the circumferential portion 25a and the first lead-out portion 25b, and a second connection portion 25e connecting the other end of the circumferential portion 25a and the second lead-out portion 25c.

[0024] The circumferential portion 25a extends in the circumferential direction around the coil axis Ax extending along the T axis. In the illustrated embodiment, the coil axis Ax extends along the axial direction parallel to the T axis. The coil axis Ax does not have to be parallel to the T axis. The coil axis Ax intersects the upper surface 10b and the lower surface 10a of the base body 10. In the illustrated embodiment, the coil axis Ax extends in a direction perpendicular to the first main surface 10a through the intersection of the diagonals of the first main surface 10a having a rectangular shape in plan view.

[0025] One end of the first lead-out portion 25b is connected to the first connection portion 25d, and the first lead-out portion 25b extends downward along the T axis from the connection position with the first connection portion 25d. The other end of the first lead-out portion 25b is exposed outside the base body 10 from the lower surface 10a. The first lead-out portion 25b is connected to the first external electrode 21 at the other end exposed from the lower surface 10a.

[0026] One end of the second lead portion 25c is connected to the second connection portion 25e, and the second lead portion 25c extends downward along the T axis from the connection position with the second connection portion 25e. The other end of the second lead portion 25c is exposed outward from the base body 10 from the lower surface 10a. The second lead portion 25c is connected to the second external electrode 22 at the other end exposed from the lower surface 10a.

[0027] The surface of the coil conductor 25 may be covered with an insulating film (not shown) made of an insulating material having excellent insulating properties. The insulating film may be an oxide film formed on the surface of the coil conductor 25 and the surface of the second coil conductor 35 during the heat treatment in the manufacturing process of the coil component 1. The insulating film may be a coating film made of a resin having excellent insulating properties such as polyurethane, polyamideimide, polyimide, polyester, and polyester-imide.

[0028] 1-4 Specific description of the coil component 1 1-4-1 Description of the base body 10 In one aspect, the base body 10 is a laminate in which a plurality of magnetic films are laminated. As will be described later, the base body 10 may be a laminate in which a magnetic film having a conductor pattern forming the circumferential portion 25a formed on the surface and other magnetic films are laminated.

[0029] FIG. 2 is a cross-sectional view schematically showing a cross-section of the coil component 1 cut along the line I-I. The cross-section of FIG. 2 shows a cut surface obtained by cutting the coil component 1 with a plane passing through the coil axis Ax and parallel to the LT plane. As shown in FIG. 2, the magnetic films constituting the base body 10 include magnetic films 11a, 11b, 11c, 11d, and 11e. However, the boundaries of the magnetic films 11a to 11e may not be visible even when observing the cross-section of the base body 10 with an SEM.

[0030] On each upper surface of the magnetic films 11a to 11e, a conductor pattern forming the circumferential portion 25a is formed. In this specification, in the base body 10, the region formed by laminating the magnetic films 11a to 11e is called the main body portion 11. Also, in the main body portion 11, in the radial direction centered on the coil axis Ax, the region inside the inner peripheral surface of the circumferential portion 25a is called the core portion C1. In the illustrated embodiment, the portion of the magnetic films 11a to 11e radially inside the inner peripheral surface of the circumferential portion 25a constitutes the core portion C1. Also, a region that is part of the core portion C1 and includes the center of the core portion C1 in the axial direction along the coil axis Ax is called the core center portion C2. In the illustrated embodiment, the portion of the magnetic film 11c radially inside the inner peripheral surface of the circumferential portion 25a constitutes the core center portion C2. In this specification, the relative permeability of the core center portion C2 is called the core center portion relative permeability.

[0031] In the base body 10, a first low magnetic permeability portion 12a is provided on the lower surface of the main body portion 11. The first low magnetic permeability portion 12a has a first relative permeability lower than the core center portion relative permeability of the core center portion C2. Since one end surface S1 of the circumferential portion 25a is exposed from the lower surface of the main body portion 11, the first low magnetic permeability portion 12a is provided between one end surface S1 of the circumferential portion 25a and the lower surface 10a of the base body 10. The first low magnetic permeability portion 12a is provided so as to cover one end surface S1 of the circumferential portion 25a. One end surface S1 of the circumferential portion 25a is one end surface of the circumferential portion 25a in the axial direction along the coil axis Ax. In the illustrated embodiment, one end surface S1 of the circumferential portion 25a is the lower surface of the circumferential portion 25a. In the illustrated embodiment, the first low magnetic permeability portion 12a extends from the first end surface 10c to the second end surface 10d of the base body 10 and also extends from the first side surface 10e to the second side surface 10f of the base body 10 on the LW surface. That is, the first low magnetic permeability portion 12a defines a part of the first end surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f of the base body.

[0032] In the base body 10, a second low magnetic permeability portion 12b is provided on the upper surface of the main body portion 11. The second low magnetic permeability portion 12b has a second specific magnetic permeability that is lower than the core center specific magnetic permeability of the core center portion C2. Since the other end surface S2 of the circumferential portion 25a is exposed from the upper surface of the main body portion 11, the second low magnetic permeability portion 12b is provided between the other end surface S2 of the circumferential portion 25a and the upper surface 10b of the base body 10. The second low magnetic permeability portion 12b is provided so as to cover the other end surface S2 of the circumferential portion 25a. The other end surface S2 of the circumferential portion 25a is a surface that faces one end surface S1 of the circumferential portion 25a in the axial direction along the coil axis Ax. In the illustrated embodiment, the other end surface S2 of the circumferential portion 25a is the upper surface of the circumferential portion 25a. In the illustrated embodiment, the second low magnetic permeability portion 12b extends from the first end surface 10c to the second end surface 10d of the base body 10 on the LW surface, and also extends from the first side surface 10e to the second side surface 10f of the base body 10. That is, the second low magnetic permeability portion 12b defines a part of the first end surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f of the base body.

[0033] In one aspect, the specific magnetic permeability of the region (the region composed of the magnetic films 11a, 11b, 11d, and 11e) other than the core center portion C2 in the core portion C1 may be equal to the first specific magnetic permeability. In another aspect, the specific magnetic permeability of the region other than the core center portion C2 in the core portion C1 may be equal to the second specific magnetic permeability. In still another aspect, the specific magnetic permeability of the region other than the core center portion C2 in the core portion C1 may be equal to the core center specific magnetic permeability.

[0034] In one aspect, the substrate 10 contains a plurality of metal magnetic particles, and adjacent metal magnetic particles are bonded to each other via an insulating layer or a binder formed on the surface of each particle. In one aspect, a first average particle size indicating the average particle size of the metal magnetic particles contained in the first low magnetic permeability portion 12a and a second average particle size indicating the average particle size of the metal magnetic particles contained in the second low magnetic permeability portion 12b are smaller than a third average particle size indicating the average particle size of the metal magnetic particles contained in the core center portion C2. In one aspect, the first average particle size and the second average particle size are in the range of 1 / 10 to 1 / 2 of the third average particle size. On the other hand, the filling rates of the metal magnetic particles in the first low magnetic permeability portion 12a and the second low magnetic permeability portion 12b are about the same as the filling rate of the metal magnetic particles in the core center portion C2. The filling rates of the metal magnetic particles in the first low magnetic permeability portion 12a and the second low magnetic permeability portion 12b are 0.8 times to 1.2 times the filling rate of the metal magnetic particles in the core center portion C2. By making the first average particle size and the second average particle size smaller than the third average particle size when the filling rates of the metal magnetic particles in the first low magnetic permeability portion 12a and the second low magnetic permeability portion 12b are about the same as the filling rate of the metal magnetic particles in the core center portion C2, the first specific magnetic permeability of the first low magnetic permeability portion 12a and the second specific magnetic permeability of the second low magnetic permeability portion 12b can be made lower than the core center specific magnetic permeability of the core center portion C2.

[0035] The "average particle size" of the metal magnetic particles in this specification is determined by cutting the substrate 10 along its thickness direction (T-axis direction) to expose a cross section, obtaining a particle size distribution based on a photograph taken of the cross section with a scanning electron microscope (SEM) at a magnification of 1000 to 5000 times, and determining it based on the particle size distribution thus obtained. For example, the 50% value (D50) of the particle size distribution obtained based on the SEM photograph can be taken as the average particle size of the metal magnetic particles. When obtaining the average particle size of the metal magnetic particles contained in the first low magnetic permeability portion 12a, a region corresponding to the first low magnetic permeability portion 12a in the cross section of the substrate 10 is observed. When obtaining the average particle size of the metal magnetic particles contained in the second low magnetic permeability portion 12b, a region corresponding to the second low magnetic permeability portion 12b in the cross section of the substrate 10 is observed.

[0036] In one aspect, the first relative magnetic permeability of the first low magnetic permeability portion 12a is approximately the same as the second relative magnetic permeability of the second low magnetic permeability portion 12b. For example, the first relative magnetic permeability is 0.8 to 1.2 times that of the second low magnetic permeability portion 12b. In another aspect, the first relative magnetic permeability may be lower than that of the second low magnetic permeability portion 12b.

[0037] The base body 10 has a first cover portion 13a provided on the side opposite to the core portion C1 with respect to the first low magnetic permeability portion 12a in the axial direction. In the illustrated embodiment, the first cover portion 13a is provided on the lower surface of the first low magnetic permeability portion 12a. The first cover portion 13a has a third relative magnetic permeability higher than the first relative magnetic permeability of the first low magnetic permeability portion 12a. In the illustrated embodiment, the first cover portion 13a defines a part of the first end surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f of the base body 10 and the entire lower surface 10a.

[0038] The base body 10 has a second cover portion 13b provided on the side opposite to the core portion C1 with respect to the second low magnetic permeability portion 12b in the axial direction. In the illustrated embodiment, the second cover portion 13b is provided on the upper surface of the second low magnetic permeability portion 12b. The second cover portion 13b has a fourth relative magnetic permeability higher than the second relative magnetic permeability of the second low magnetic permeability portion 12b. In the illustrated embodiment, the first cover portion 13a defines a part of the first end surface 10b, the second end surface 10d, the first side surface 10e, and the second side surface 10f of the base body 10 and the entire upper surface 10a.

[0039] 1-4-2 Specific description of the coil conductor On the upper surfaces of each of the magnetic films 11a to 11e, conductor patterns that form part of the coil conductor 25 are formed. Also, through holes that penetrate each magnetic film in the T-axis direction are formed at predetermined positions of the magnetic films 11a to 11e, and via conductors are embedded in these through holes. Each of the conductor patterns and via conductors of the coil component 1 is formed by screen-printing a conductive paste made of a metal or alloy with excellent conductivity on a magnetic sheet that is a precursor of the magnetic films 11a to 11e and heating the conductive paste printed on this magnetic sheet. As the material of this conductive paste, Ag, Pd, Cu, Al, or an alloy thereof can be used. The conductor patterns and via conductors of the coil component 1 may be formed of materials other than those described above. The conductor patterns and via conductors of the coil component 1 may be formed, for example, by a sputtering method, an inkjet method, or other known methods.

[0040] Referring to FIGS. 3a to 3e, the conductor patterns formed on the upper surfaces of the respective magnetic films will be further described. FIG. 3a shows a first conductor pattern 25a1 that constitutes part of the circumferential portion 25a and the first connection portion 25d. FIGS. 3b to 3d show a second conductor pattern 25a2, a third conductor pattern 25a3, and a fourth conductor pattern 25a4 that each constitute part of the circumferential portion 25a, respectively. FIG. 3e shows a fifth conductor pattern 25a5 that constitutes part of the circumferential portion 25a and the second connection portion 25e.

[0041] As shown in FIG. 3a, on the upper surface of the magnetic film 11a, a first conductor pattern 25a1 and a first connection portion 25d of the circumferential portion 25a are formed. The first conductor pattern 25a1 extends along an elliptical first orbit O1 around the coil axis Ax. The first connection portion 25d extends linearly along the L-axis direction between the first conductor pattern 25a1 and the first lead-out portion 25b. The first conductor pattern 25a1 extends along the first orbit O1 around the coil axis Ax for a number of turns of one turn or less. The first connection portion 25d extends linearly outside the first orbit O1. The first conductor pattern 25a1 is connected to the first connection portion 25d at one end P1 thereof, and is connected to a via conductor V1 at the other end.

[0042] As shown in FIG. 3b, on the upper surface of the magnetic film 11b, a second conductor pattern 25a2 that constitutes a part of the circumferential portion 25a is formed. The second conductor pattern 25a2 extends along an elliptical second orbit O2 around the coil axis Ax. The second conductor pattern 25a2 extends along the second orbit O2 around the coil axis Ax for a number of turns of one turn or less. One end of the second conductor pattern 25a2 is connected to the via conductor V1, and the other end is connected to the via conductor V2. In a region of the magnetic film 11b that overlaps with the via conductor V1, a through hole penetrating the magnetic film 11b in the T-axis direction is provided, and the via conductor V1 is embedded in this through hole.

[0043] As shown in FIG. 3c, on the upper surface of the magnetic film 11c, a third conductor pattern 25a3 that constitutes a part of the circumferential portion 25a is formed. The third conductor pattern 25a3 extends along an elliptical third orbit O3 around the coil axis Ax. The third conductor pattern 25a3 extends along the third orbit O3 around the coil axis Ax for a number of turns of one turn or less. One end of the third conductor pattern 25a3 is connected to the via conductor V2, and the other end is connected to the via conductor V3. In a region of the magnetic film 11c that overlaps with the via conductor V2, a through hole penetrating the magnetic film 11c in the T-axis direction is provided, and the via conductor V2 is embedded in this through hole.

[0044] As shown in FIG. 3d, on the upper surface of the magnetic film 11d, a fourth conductor pattern 25a4 that forms a part of the circumferential portion 25a is formed. The fourth conductor pattern 25a4 extends along a fourth elliptical orbit O4 around the coil axis Ax. The fourth conductor pattern 25a4 extends along the fourth orbit O4 around the coil axis Ax for a number of turns of one turn or less. One end of the fourth conductor pattern 25a4 is connected to the via conductor V3, and the other end is connected to the via conductor V4. In the region of the magnetic film 11d that overlaps with the via conductor V3, a through hole that penetrates the magnetic film 11d in the T-axis direction is provided, and the via conductor V3 is embedded in this through hole.

[0045] As shown in FIG. 3e, on the upper surface of the magnetic film 11e, a fifth conductor pattern 25a5 that forms a part of the circumferential portion 25a and a second connection portion 25e are formed. The fifth conductor pattern 25a5 extends along a fifth elliptical orbit O5 around the coil axis Ax. The second connection portion 25e extends linearly between the fifth conductor pattern 25a5 and the second lead-out portion 25c. The fifth conductor pattern 25a5 extends along the fifth orbit O5 around the coil axis Ax for a number of turns of one turn or less. One end of the fifth conductor pattern 25a5 is connected to the via conductor V4, and the other end P2 is connected to the second connection portion 25e. In the region of the magnetic film 11e that overlaps with the via conductor V4, a through hole that penetrates the magnetic film 11e in the T-axis direction is provided, and the via conductor V4 is embedded in this through hole.

[0046] In the region of each of the magnetic films 11a to 11e that overlaps with the second lead-out portion 25c, a through hole that penetrates the magnetic films 11a to 11e in the T-axis direction is provided, and the via conductor that constitutes the second lead-out portion 25c is embedded in this through hole.

[0047] In the illustrated embodiment, all of the first orbit O1 to the fifth orbit O5 have an elliptical shape. The shapes of the first orbit O1 to the fifth orbit O5 are not limited to an elliptical shape. For example, the shapes of the first orbit O1 and the second orbit O2 may be an oval, a circle, a rectangle, a polygon, or other shapes in a plan view.

[0048] The inner diameters of both the first conductor pattern 25a1 and the fifth conductor pattern are larger than those of the second conductor pattern 25a2 to the fourth conductor pattern 25a4. For example, the inner diameter d1 indicating the inner diameter of the first conductor pattern 25a1 in the L-axis direction and the inner diameter d5 of the fifth conductor pattern are larger than the respective inner diameters d3 of the second conductor pattern 25a2 to the fourth conductor pattern 25a4.

[0049] Thus, the circumferential portion 25a is composed of the first conductor pattern 25a1 to the fifth conductor pattern 25a5 and the via conductors V1 to V4. The circumferential portion 25a is connected to the first connection portion 25d at one end P1 thereof, and is connected to the second connection portion 25e at the other end P2 thereof.

[0050] As shown in FIG. 3e, in a plan view (from the viewpoint seen in the T-axis direction), a first half line HL1 connecting one end P1 of the circumferential portion 25a and the coil axis Ax, and a second half line HL2 connecting the other end P2 of the circumferential portion 25a and the coil axis Ax form a first angle α. In other words, the second half line HL2 is located at a position where the first half line HL1 is rotated counterclockwise by the first angle α about the coil axis Ax. In the plan view, in the region corresponding to the first angle α between the first half line HL1 and the second half line HL2 of the circumferential portion 25a, five layers of conductor patterns are arranged overlappingly in the T-axis direction, but in other regions (the region corresponding to the major angle (360° - α) defined by the first half line HL1 and the second half line HL2), only four layers of conductor patterns are arranged. Thus, in the multi-layer region corresponding to the first angle α of the circumferential portion 25a, it contains one more layer of conductor patterns than other regions. Since the multi-layer region contains one more layer of conductor patterns than other regions, when the current flowing through the circumferential portion 25a changes, magnetic flux concentrates around the multi-layer region. In one aspect, by making the first angle α less than 180°, the region where magnetic flux concentrates can be reduced. The coil conductor of a conventional coil component is configured such that the number of conductor patterns increases by one layer in the region (the region where the angle corresponding to the first angle α is 180°) that occupies half of the circumferential portion of the coil conductor in the circumferential direction. Therefore, in the coil component 1, by making the first angle α less than 180°, the area of the multi-layer region where magnetic flux concentrates can be reduced, so the magnetic loss in the base 10 can be reduced. In another aspect, the first angle α is made less than 100°. By making the first angle α less than 180°, the magnetic loss in the base 10 can be further reduced.

[0051] 1-4-3 Manufacturing method Next, an example of the manufacturing method of the coil component 1 will be described. The coil component 1 can be manufactured, for example, by a lamination process. Hereinafter, an example of the manufacturing method of the coil component 1 by the sheet lamination method will be described.

[0052] First, a magnetic sheet which is a precursor of each of the magnetic films 11a to 11e, the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b constituting the substrate 10 is produced. The magnetic sheet is produced, for example, by kneading metal magnetic powder with a resin to prepare a slurry, applying this slurry onto the surface of a plastic base film by a doctor blade method or other general methods, drying it, and cutting the dried slurry into a predetermined size. In the magnetic sheet produced in this way, a plurality of metal magnetic particles are dispersed in the resin. When producing the magnetic sheet which is a precursor of the first low magnetic permeability portion 12a and the second low magnetic permeability portion 12b, metal magnetic particles having an average particle size smaller than that of the metal magnetic particles used when producing the magnetic sheet which is a precursor of the magnetic film 11c are used. For this reason, the average particle size of the metal magnetic particles contained in the magnetic sheet which is a precursor of the first low magnetic permeability portion 12a is smaller than the average particle size of the metal magnetic particles in each of the magnetic sheet which is a precursor of the magnetic film 11c, the first cover portion 13a, and the second cover portion 13b. Similarly, the average particle size of the metal magnetic particles contained in the magnetic sheet which is a precursor of the second low magnetic permeability portion 12b is smaller than the average particle size of the metal magnetic particles in each of the magnetic sheet which is a precursor of the magnetic film 11c, the first cover portion 13a, and the second cover portion 13b.

[0053] Next, through-holes penetrating each magnetic sheet, which is a precursor of the magnetic films 11a to 11e, the first low magnetic permeability portion 12a, and the first cover portion 13a, in the T-axis direction are formed at predetermined positions of each magnetic sheet. Next, by printing a conductive paste on the upper surface of each of the magnetic sheets that are precursors of the magnetic films 11a to 11e by the screen printing method, an unfired conductor pattern is formed on the magnetic sheet, and the conductive paste is embedded in the through-holes formed in each magnetic sheet. The unfired conductor patterns formed on the magnetic sheets that are precursors of the magnetic films 11a to 11e respectively become the first conductor pattern 25a1 to the fifth conductor pattern 25a5 after heating. Each conductor pattern can be formed by various known methods other than the screen printing method. Also, the conductive paste is embedded in the through-holes formed in each magnetic sheet that is a precursor of the first low magnetic permeability portion 12a and the first cover portion 13a.

[0054] Each of the magnetic sheets that are precursors of the magnetic films 11a to 11e, the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b may be a single magnetic sheet or a laminated sheet in which a plurality of magnetic sheets are laminated. By adjusting the number of magnetic sheets, the thickness of each of the magnetic films 11a to 11e, the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b can be adjusted.

[0055] Next, the magnetic sheets that are precursors of each of the magnetic films 11a to 11e, the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b are laminated to obtain a laminate. Each laminated magnetic sheet may be thermocompression bonded by a press machine. Next, the main body laminate is diced using a cutting machine such as a dicing machine or a laser processing machine to obtain a chip laminate. For the end portion of the chip laminate, a polishing process such as barrel polishing may be performed as necessary.

[0056] Next, the chip laminate is degreased, and the degreased chip laminate is heat-treated to obtain the base 10. By this heat treatment, an oxide layer is formed on the surface of each of the plurality of metal magnetic particles contained in each magnetic sheet, and adjacent metal magnetic particles are bonded via the oxide layer. The heat treatment of the chip laminate is performed, for example, at a heating temperature of 600°C to 800°C for a heating time of 20 minutes to 120 minutes.

[0057] Next, the first external electrode 21 and the second external electrode 22 are formed by applying a conductive paste to the lower surface 10a of the base 10. The first external electrode 21 and the second external electrode 22 may include a plating layer. This plating layer may be two or more layers. The two-layer plating layer may include a Ni plating layer and a Sn plating layer provided outside the Ni plating layer.

[0058] Thus, the coil component 1 is obtained. The coil component 1 may be manufactured by a compression molding method, a thin film process method, a slurry build-up method, or other known methods.

[0059] Some of the steps included in the above manufacturing method can be appropriately omitted. In the manufacturing method of the coil component 1, steps not explicitly described in this specification can be executed as needed. Some of the steps included in the above manufacturing method of the coil component 1 can be executed with the order swapped at any time as long as it does not deviate from the gist of the present invention. Some of the steps included in the above manufacturing method of the coil component 1 can be executed simultaneously or in parallel if possible.

[0060] Next, with reference to FIG. 4, the operation and effect of the coil component 1 will be described. In FIG. 4, the flow of magnetic flux is schematically shown by arrows. Since magnetic flux tends to follow a path with low magnetic resistance, if the magnetic permeability of the base body 10 is uniform regardless of location, the magnetic flux will attempt to pass through the first magnetic path MP1 that passes very close to the coil conductor 25. When a large amount of magnetic flux passes through the first magnetic path MP1, the magnetic flux tends to concentrate at positions on the first magnetic path MP1 where the direction of the magnetic flux changes. In the illustrated example, the magnetic flux tends to concentrate in the region R1 near the lower end of the inner peripheral surface of the circumferential portion 25a and the region R2 near the upper end. In the coil component 1, since the first low magnetic permeability portion 12a is provided so as to cover the lower surface of the first conductor pattern 25a1 and the second low magnetic permeability portion 12b is provided so as to cover the upper surface of the fifth conductor pattern 25a5, a part of the first magnetic path MP1 is occupied by a low magnetic permeability region. For this reason, more magnetic flux will flow through the second magnetic path MP2 that is outside the first magnetic path MP1. Since the second magnetic path MP2 passes through a position away from the region near the inner peripheral surfaces of the first conductor pattern 25a1 and the fifth conductor pattern 25a5, by providing the first low magnetic permeability portion 12a and the second low magnetic permeability portion 12b in the base body 10, the concentration of magnetic flux in the region near the inner peripheral surfaces of the first conductor pattern 25a1 and the fifth conductor pattern 25a5 can be alleviated, and the magnetic loss in the base body 10 can be further suppressed.

[0061] In the base body 10 of the coil component 1, the core center portion specific magnetic permeability of the core center portion C2 may be higher than the specific magnetic permeability of other regions of the base body 10. In the core center portion C2, since the magnetic flux flows along the coil axis Ax and the direction of the magnetic flux does not change significantly, magnetic flux concentration is unlikely to occur. For this reason, even if the core center portion specific magnetic permeability in the core center portion C2 is increased, magnetic loss due to magnetic flux concentration is unlikely to occur in the core center portion C2. By making the core center portion specific magnetic permeability of the core center portion C2 larger than the specific magnetic permeability of other regions of the base body 10, the inductance of the coil component 1 can be improved without increasing the magnetic loss.

[0062] In one aspect, the first specific magnetic permeability of the first low magnetic permeability portion 12a can be made lower than the second specific magnetic permeability of the second low magnetic permeability portion 12b. In the coil component 1, since both the first lead portion 25b and the second lead portion 25c extend toward the lower surface 10a, in the region R3 near the connection position between the first conductor pattern 25a1 and the first lead portion 25b, the magnetic flux generated from the current flowing through the first conductor pattern 25a1 and the magnetic flux generated from the current flowing through the first lead portion 25b are superposed, so magnetic flux concentration is likely to occur in the region R3. In the coil component 1, by covering the lower surface of the first conductor pattern 25a1 with the first low magnetic permeability portion 12a, the region R3 is occupied by the first low magnetic permeability portion 12a. Thereby, the magnetic flux flowing through the region R3 can be reduced, so the concentration of magnetic flux in the region R3 can be alleviated, and the magnetic loss in the region R3 of the base 10 can be suppressed.

[0063] Subsequently, with reference to FIG. 5, a modified example of the first embodiment will be described. In the aspect shown in FIG. 5, among the conductor patterns constituting the circumferential portion 25a, the inner diameters of the conductor patterns (the first conductor pattern 25a1 at the lower end and the fifth conductor pattern 25a5 at the upper end) at the ends in the direction along the coil axis Ax are larger than the inner diameters of the other conductor patterns (the second conductor pattern 25a2 to the fourth conductor pattern 25a4), so that the circumferential portion 25a is configured. In the aspect shown in FIG. 5, the first inner diameter d1 representing the inner diameter of the first end portion 26 close to one end surface S1 of the circumferential portion 25a and the second inner diameter d2 representing the inner diameter of the second end portion 27 close to the other end surface S2 of the circumferential portion 25a are larger than the third inner diameter d3 representing the inner diameter of the central portion 28 of the circumferential portion 25a between the first end portion 26 and the second end portion 27 in the axial direction. In the aspect shown in FIG. 5, the first end portion 26 close to one end surface S1 of the circumferential portion 25a includes the first conductor pattern 25a1, and the second end portion 27 close to the other end surface S2 of the circumferential portion 25a includes the fifth conductor pattern 25a5. Further, in the illustrated embodiment, the central portion 28 of the circumferential portion 25a between the first end portion 26 and the second end portion 27 in the axial direction includes the second conductor pattern 25a2 to the fourth conductor pattern 25a4.

[0064] FIG. 5 shows the inner diameters d1, d2, and d3 in the cross section obtained by cutting the coil component 1 along the LT plane. However, even in the cross section obtained by cutting the coil component 1 along a plane passing through the coil axis Ax and parallel to the WT plane, the inner diameter of the first end portion 26 and the inner diameter of the second end portion 27 of the circumferential portion 25a are larger than the inner diameter of the central portion 28.

[0065] The operation and effect of the coil component 1 shown in FIG. 5 will be described with reference to FIG. 6. When the current flowing through the coil conductor 25 changes during the use of the coil component 1, a magnetic flux is generated around the coil conductor 25. In FIG. 6, the flow of the magnetic flux is schematically shown by arrows. Similar to the description with reference to FIG. 4, also in the example shown in FIG. 6, the magnetic flux tends to concentrate in the region R1 near the lower end and the region R2 near the upper end of the inner peripheral surface of the circumferential portion 25a. In the coil component 1 shown in FIG. 6, by forming the circumferential portion 25a such that the inner diameter d1 of the first conductor pattern 25a1 at the lower end of the circumferential portion 25a and the inner diameter d2 of the fifth conductor pattern 25a5 at the upper end of the circumferential portion 25a become larger, from the viewpoint of the geometric arrangement of each conductor pattern constituting the circumferential portion 25a, the concentration of the magnetic flux in the regions R1 and R2 is alleviated. That is, in the coil component 1, by forming the circumferential portion 25a such that the inner diameter d1 of the first conductor pattern 25a1 and the inner diameter d2 of the fifth conductor pattern 25a5 become larger, the concentration of the magnetic flux in the region near the inner peripheral surface of the first conductor pattern 25a1 and the fifth conductor pattern 25a5 can be alleviated, and the magnetic loss in the base 10 can be suppressed.

[0066] 2 Second Embodiment Next, with reference to FIGS. 7 and 8, the coil component 101 according to the second embodiment will be described. The coil component 101 is a planar coil. The coil component 101 is different from the coil component 1 in that the coil conductor 125 is provided in the base 10 instead of the coil conductor 25, and the first external electrode 121 and the second external electrode 122 are provided instead of the first external electrode 21 and the second external electrode 22. Among the components of the coil component 101 shown in FIGS. 7 and 8 that are the same as or similar to the components of the coil component 1 shown in FIG. 1, the same reference numerals as those in FIG. 1 are given, and detailed descriptions of these same or similar components are omitted.

[0067] As shown in FIG. 7, the coil component 101 includes a base 10, an insulating plate 150 provided in the base 10, a coil conductor 125 provided on the upper and lower surfaces of the insulating plate 150 within the base 10, a first external electrode 121 provided on the base 10, and an external electrode 122 provided on the base 10 spaced apart from the first external electrode 121. The insulating plate 150 is a member formed in a plate shape from an insulating material.

[0068] As shown in FIG. 8, the base 10 includes a main body portion 11, a first low magnetic permeability portion 12a provided on the lower surface of the main body portion 11, a second low magnetic permeability portion 12b provided on the upper surface of the main body portion 11, a first cover portion 13a provided on the lower surface of the first low magnetic permeability portion 12a, and a second cover portion 13b provided on the upper surface of the second low magnetic permeability portion 12b.

[0069] In the illustrated embodiment, the coil conductor 125 includes a first winding portion 125a formed on the lower surface of the insulating plate 150 and a second winding portion 125b formed on the upper surface of the insulating plate 150. The first winding portion 125a and the second winding portion 125b are connected by vias (not shown). The first winding portion 125a is formed to have a predetermined pattern on the lower surface of the insulating plate 150, and the second winding portion 125b is formed to have a predetermined pattern on the upper surface of the insulating plate 150. An insulating film may be provided on the surfaces of the first winding portion 125a and the second winding portion 125b. The coil conductor 125 can take various shapes.

[0070] A first lead-out portion 125c is connected to the radially outer end of the first winding portion 125a. The first lead-out portion 125c is drawn out to the outside of the base body 10 and is electrically connected to the first external electrode 121. A second lead-out portion 125d is connected to the radially outer end of the second winding portion 125b. The second lead-out portion 125d is drawn out to the outside of the base body 10 and is electrically connected to the second external electrode 122.

[0071] As shown in FIG. 8, one end surface S11 (the lower end surface of the first winding portion 125a) of the coil conductor 125 is covered by the first low magnetic permeability portion 12a. Also, the other end surface S12 (the upper end surface of the second winding portion 125b) of the coil conductor 125 is covered by the second low magnetic permeability portion 12b. The first relative magnetic permeability of the first low magnetic permeability portion 12a and the second relative magnetic permeability of the second low magnetic permeability portion 12b are lower than the core center relative magnetic permeability of the core center portion C2. Therefore, in the coil component 101 of the second embodiment, by the same mechanism as described for the coil component 1 in the first embodiment, the concentration of magnetic flux in the region near the inner peripheral surface at the lower end of the first winding portion 125a and the region near the inner peripheral surface at the upper end of the second winding portion 125b is alleviated, and magnetic loss in the base body 10 can be suppressed.

[0072] Next, an example of a method for manufacturing the coil component 101 will be described. First, an insulating plate formed in a plate shape from a magnetic material is prepared. Next, photoresist is applied to the upper and lower surfaces of the insulating plate, and then conductor patterns are exposed and transferred to each of the upper and lower surfaces of the insulating plate, followed by a development process. As a result, a resist having an opening pattern for forming the coil conductor 125 is formed on each of the upper and lower surfaces of the insulating plate 150.

[0073] Next, each of the opening patterns is filled with a conductive metal by plating. Subsequently, the resist is removed from the insulating plate 150 by etching, so that the first winding portion 125a is formed on the lower surface of the insulating plate 150, and the second winding portion 125b is formed on the upper surface of the insulating plate 150. Also, a via for connecting the first winding portion 125a and the second winding portion 125b is formed by filling a conductive paste into a through hole provided in the insulating plate 150.

[0074] Next, the base body 10 is formed on both sides of the insulating plate 150 on which the coil conductor 125 is formed. To form the base body 10, magnetic sheets that are precursors of the main body portion 11, the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b are produced. Each of the first low magnetic permeability portion 12a, the second low magnetic permeability portion 12b, the first cover portion 13a, and the second cover portion 13b may be composed of a single magnetic sheet or may be composed of a plurality of magnetic sheets. The main body portion 11 is composed of a plurality of magnetic sheets.

[0075] Next, magnetic sheets that are precursors of a part (lower part) of the main body portion 11, the first low magnetic permeability portion 12a, and the first cover portion 13a are laminated to obtain a first laminate. Also, magnetic sheets that are precursors of a part (upper part) of the main body portion 11, the second low magnetic permeability portion 12b, and the second cover portion 13b are laminated to obtain a second laminate. Next, the first laminate is disposed below the coil conductor 125, and the second laminate is disposed above the coil conductor 125, and pressure is applied at 5 to 100 MPa while heating to produce a compression molded body containing the coil conductor inside.

[0076] Next, heat treatment is performed on the above compression molded body, and by this heat treatment, the base body 10 having the coil conductor 125 inside is obtained. By this heat treatment, the resin in the magnetic sheet is cured to become a binder, and the metal magnetic particles are bonded to each other by the binder. The heat treatment in the heat treatment step is performed at a temperature equal to or higher than the curing temperature of the resin in the mixed resin composition. The heat treatment in the heat treatment step is performed, for example, at 100°C to 200°C for 30 minutes to 240 minutes.

[0077] Next, by applying conductive paste to both ends of the base body 10 obtained as described above, the external electrode 121 and the external electrode 122 are formed. The first external electrode 121 is electrically connected to one end of the coil conductor 125 provided in the base body 10, and the second external electrode 122 is provided so as to be electrically connected to the other end of the coil conductor 125 provided in the base body 10. Thus, the coil component 101 is manufactured.

[0078] Subsequently, with reference to FIG. 9, a modified example of the first embodiment will be described. In the aspect shown in FIG. 9, the inner diameter d11 representing the inner diameter of the first end portion 126 close to one end surface S11 (the end surface of the first turn portion 125a) of the coil conductor 125 and the inner diameter d12 representing the inner diameter of the second end portion 127 close to the other end surface S12 (the end surface of the second turn portion 125b) of the coil conductor 125 are larger than the inner diameter d13 representing the inner diameter of the central portion 128 between the first end portion 126 and the second end portion 127 in the axial direction of the coil conductor 125.

[0079] FIG. 9 shows the inner diameter d11, the inner diameter d12, and the inner diameter d13 in the cross section obtained by cutting the coil component 1 along the LT plane. However, also in the cross section obtained by cutting the coil component 1 along a plane passing through the coil axis Ax and parallel to the WT plane, the inner diameter of the first end portion 126 of the turn portion 25a and the inner diameter of the second end portion 127 are larger than the inner diameter of the central portion 128.

[0080] The dimensions, materials, and arrangements of the respective components described in the various embodiments described above are not limited to those explicitly described in each embodiment, and each of these components can be deformed so as to have any dimensions, materials, and arrangements included in the scope of the present invention.

[0081] Components not explicitly described in this specification can also be added to each of the above embodiments, and some of the components described in each embodiment can also be omitted.

[0082] In this specification and the like, notations such as "first", "second", "third", etc. are attached to identify components, and do not necessarily limit the number, order, or content thereof. Also, numbers for identifying components are used for each context, and the numbers used in one context do not necessarily indicate the same configuration in other contexts. Further, it does not prevent a component identified by a certain number from also having the functions of a component identified by another number.

[0083] In this specification, the following technologies are also disclosed. [Appendix 1] A base body (10), A coil conductor (25) having a winding portion (25a) wound around a coil axis (Ax) inside the base body, and comprising, The base body has a core portion (C1) inside the winding portion in the radial direction centered on the coil axis, a first low magnetic permeability portion (12a) covering one end surface (S1) of the winding portion in the axial direction along the coil axis and having a first magnetic permeability lower than the core center portion specific magnetic permeability of the core center portion (11c) at the center of the core portion in the axial direction, and a second low magnetic permeability portion (12b) covering the other end surface (S2) of the winding portion facing the one end surface and having a second magnetic permeability lower than the core center portion specific magnetic permeability. A coil component. [Appendix 2] The base body contains a plurality of metal magnetic particles, A first average particle size indicating the average particle size of first metal magnetic particles contained in the first low magnetic permeability portion among the plurality of metal magnetic particles and a second average particle size indicating the average particle size of second metal magnetic particles contained in the second low magnetic permeability portion among the plurality of metal magnetic particles are smaller than a third average particle size indicating the average particle size of third metal magnetic particles contained in the core portion among the plurality of metal magnetic particles. The coil component according to [Appendix 1]. [Appendix 3] A first dimension of the base body in the axial direction is smaller than a second dimension of the base body in a direction orthogonal to the axial direction. The coil component according to [Appendix 1] or [Appendix 2]. [Appendix 4] The first inner diameter (d1) representing the inner diameter of the first end portion of the circumferential portion close to the one end face and the second inner diameter (d2) representing the inner diameter of the second end portion of the circumferential portion close to the other end face are larger than the third inner diameter (d3) representing the inner diameter of the central portion between the first end portion and the second end portion in the axial direction of the circumferential portion. The coil component according to any one of [Appendix 1] to [Appendix 3]. [Appendix 5] In the perspective view from the axial direction, the first angle (α) formed by the first half line (HL1) connecting the one end of the circumferential portion and the coil axis and the second half line (HL2) connecting the other end of the circumferential portion and the coil axis in the direction from one end to the other end of the circumferential portion is less than 180°. The coil component according to any one of [Appendix 1] to [Appendix 4]. [Appendix 6] The first angle is less than 110°. The coil component according to any one of [Appendix 1] to [Appendix 5]. [Appendix 7] A first lead-out portion (25b) electrically connected to one end of the circumferential portion and extending along the coil axis to the first surface of the base body; A second lead-out portion (25c) electrically connected to the other end of the circumferential portion and extending along the coil axis to the first surface of the base body; further comprising The first low magnetic permeability portion is provided between the first surface of the base body and the one end face of the circumferential portion. The first relative magnetic permeability is lower than the second relative magnetic permeability. The coil component according to any one of [Appendix 1] to [Appendix 6]. [Appendix 8] A first external electrode (21) electrically connected to the first lead-out conductor; A second external electrode (22) electrically connected to the second lead-out conductor; The coil component according to any one of [Appendix 1] to [Appendix 7]. [Appendix 9] The base body is provided on the side opposite to the core part with respect to the first low magnetic permeability part in the axial direction and has a first cover part (13a) having a third relative magnetic permeability higher than the first relative magnetic permeability, and is provided on the side opposite to the core part with respect to the second low magnetic permeability part in the axial direction and has a second cover part (13b) having a fourth relative magnetic permeability higher than the second relative magnetic permeability. The coil component according to any one of [Appendix 1] to [Appendix 8].

Explanation of symbols

[0084] 1, 101 Coil component 10 Base body 12a First low magnetic permeability part 12b Second low magnetic permeability part 13a First cover part 13b Second cover part 21, 22 External electrodes 25, 125 Coil conductors 25a Circumferential part 25b First lead-out part 25c Second lead-out part 125a First circumferential part 125b Second circumferential part C1 Core part C2 Core center part

Claims

1. A base body, A coil conductor having a circumferential portion wound around a coil axis inside the base body, Comprising, The base body includes a core portion inside the circumferential portion in the radial direction centered on the coil axis, a first low magnetic permeability portion covering one end surface of the circumferential portion in the axial direction along the coil axis and having a first magnetic permeability lower than the relative magnetic permeability of the core center portion at the center of the core portion in the axial direction, and a second low magnetic permeability portion covering the other end surface of the circumferential portion facing the one end surface and having a second magnetic permeability lower than the relative magnetic permeability of the core center portion, Coil component.

2. The base body contains a plurality of metal magnetic particles, A first average particle size indicating the average particle size of the first metal magnetic particles contained in the first low magnetic permeability portion among the plurality of metal magnetic particles and a second average particle size indicating the average particle size of the second metal magnetic particles contained in the second low magnetic permeability portion among the plurality of metal magnetic particles are smaller than a third average particle size indicating the average particle size of the third metal magnetic particles contained in the core center portion among the plurality of metal magnetic particles, The coil component according to claim 1.

3. A first dimension of the base body in the axial direction is smaller than a second dimension of the base body in a direction perpendicular to the axial direction, The coil component according to claim 1 or 2.

4. A first inner diameter representing the inner diameter of a first end portion of the circumferential portion close to the one end surface and a second inner diameter representing the inner diameter of a second end portion of the circumferential portion close to the other end surface are larger than a third inner diameter representing the inner diameter of a central portion of the circumferential portion between the first end portion and the second end portion in the axial direction, The coil component according to claim 1 or 2.

5. In a perspective view seen from the axial direction, a first angle formed by a first half-line connecting the one end of the circumferential portion and the coil axis and a second half-line connecting the other end of the circumferential portion and the coil axis in a direction from one end to the other end of the circumferential portion is less than 180°, The coil component according to claim 1 or 2.

6. The first angle is less than 110°, The coil component according to claim 5.

7. A first lead-out portion electrically connected to one end of the circumferential portion and extending along the coil axis to a first surface of the base body, A second lead-out portion electrically connected to the other end of the circumferential portion and extending along the coil axis to the first surface of the base body, Further comprising, The first low magnetic permeability portion is provided between the first surface of the base body and the one end surface of the circumferential portion. The first relative magnetic permeability is lower than the second relative magnetic permeability. The coil component according to claim 1 or 2. **Claim 8** A first external electrode electrically connected to the first lead conductor; A second external electrode electrically connected to the second lead conductor; The coil component according to claim 7, further comprising the above. **Claim 9** The base body has a first cover portion provided on the side opposite to the core portion with respect to the first low magnetic permeability portion in the axial direction and having a third relative magnetic permeability higher than the first relative magnetic permeability, and a second cover portion provided on the side opposite to the core portion with respect to the second low magnetic permeability portion in the axial direction and having a fourth relative magnetic permeability higher than the second relative magnetic permeability. The coil component according to claim 1 or 2.

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