Coil component, circuit board, and electronic device

Abstract

To provide a coil component that is made compact while suppressing deterioration of an inductance.SOLUTION: A coil component comprises: a base body which has a first principal surface and a second principal surface opposed to the first principal surface, a first end face 10c connecting the first and second principal surfaces, a second end face 10d opposed to the first end face, a first side face 10e connecting the first and second end faces, and a second side face 10f opposed to the first side face; and a coil conductor 25 which has a circumferential part 25a extending around a coil axis Ax intersecting the first and second principal surfaces. The circumferential part has a first part 25a1, a second part 25a2, a third part 25a3, and a fourth part 25a4 opposed to the first end face, second end face, first side face, and second side face when viewed from the direction of the coil axis. The first part and second part have smaller radii of curvature than those of the third part and fourth parts, and the distance between the first part and the first end face and the distance between the second part and the second end face are larger than the distance between the third part and the first side face and the distance between the fourth part and the second side face.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The disclosure of this specification relates to coil components, circuit boards, and electronic devices.

Background Art

[0002] Various coil components are used in electronic devices. A conventional coil component typically includes a magnetic substrate formed of a magnetic material, an external electrode provided on the surface of the magnetic substrate, and a coil conductor extending around a coil axis within the magnetic substrate.

[0003] An inductor is an example of a coil component. An inductor is a passive element used in an electronic circuit. For example, an inductor is used to remove noise in a power line or a signal line. A conventional inductor is disclosed in Japanese Patent Application Laid-Open No. 2018-0101732 (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When the current flowing through the coil conductor changes, the magnetic flux generated passes through the region between the circumferential portion and the end face and side face of the substrate. When reducing the outer dimensions of the substrate to make such a conventional coil component more compact, a sufficient area cannot be secured for the magnetic flux to pass between the coil conductor in the substrate and the surface of the substrate, and thus the inductance may deteriorate. Conversely, when uniformly increasing the distance between the coil conductor and the surface of the substrate to improve the inductance, there is a problem that the outer dimensions of the substrate increase.

[0006] One object of the invention disclosed in this specification is to solve or mitigate the problems in the above-described conventional coil component. One more specific object of the invention disclosed in this specification is to provide a compact coil component while suppressing deterioration of inductance. Other objects of the invention disclosed in this specification will become apparent by referring to the entire specification. The invention disclosed in this specification may solve problems grasped from the description in this specification instead of or in addition to the above problems.

Means for Solving the Problems

[0007] A coil component according to one or more aspects of the present invention has a first surface extending in a first direction and a second direction orthogonal to the first direction, wherein a first dimension in the first direction is larger than a second dimension in the second direction, a second surface facing the first surface, a third surface connecting an end of the first surface in the first direction and an end of the second surface in the first direction, a fourth surface facing the third surface, a fifth surface connecting the third surface and the fourth surface, and a sixth surface facing the fifth surface, a base made of a magnetic material, a coil conductor having a circumferential portion extending around a coil axis intersecting the first surface and the second surface, a first external electrode provided on the base and electrically connected to one end of the coil conductor, and a second external electrode provided on the base and electrically connected to the other end of the coil conductor. In one or more aspects, when viewed from the direction of the coil axis, the circumferential portion has a first portion facing the third surface and curving toward the third surface, a second portion facing the fourth surface and curving toward the fourth surface, a third portion connecting the first portion and the second portion and facing the fifth surface, and a fourth portion connecting the first portion and the second portion and facing the sixth surface. In one or more aspects, the radius of curvature of both the first portion and the second portion is smaller than the radius of curvature of the third portion and the fourth portion. In one or more aspects, when viewed from the direction of the coil axis, the distance between the first portion and the third surface and the distance between the second portion and the fourth surface are both larger than the distance between the third portion and the fifth surface and the distance between the fourth portion and the sixth surface.

[0008] In one or more aspects of the present invention, the distances between the first portion and the third surface and between the second portion and the fourth surface are both in the range of 1.5 to 10 times the distances between the third portion and the fifth surface and between the fourth portion and the sixth surface.

[0009] In one or more aspects of the present invention, when viewed from the direction of the coil axis, the distance between the first portion of the circumferential portion and the third surface is substantially equal to the distance between the second portion of the circumferential portion and the fourth surface.

[0010] In one or more aspects of the present invention, when viewed from the direction of the coil axis, the distance between the third portion of the circumferential portion and the fifth surface is substantially equal to the distance between the fourth portion of the circumferential portion and the sixth surface.

[0011] In one or more aspects of the present invention, the circumferential portion has a uniform cross-sectional area.

[0012] In one or more aspects of the present invention, the first external electrode is connected to one end of the circumferential portion by a first lead portion extending along the coil axis.

[0013] In one or more aspects of the present invention, the second external electrode is connected to the other end of the circumferential portion by a second lead portion f extending along the coil axis.

[0014] In one or more aspects of the present invention, the area of the circumferential portion viewed from the direction of the coil axis with respect to the area of the first surface viewed from the direction of the coil axis is 0.3 or more.

[0015] In one embodiment of the present invention, the coil component is used in a DC / DC converter. One embodiment of the present invention relates to a DC / DC converter including the above-described coil component.

[0016] A circuit board according to an embodiment of the present invention includes the above coil component and a mounting board joined to the external electrodes by solder.

[0017] An electronic device according to an embodiment of the present invention includes the above circuit board.

Advantages of the Invention

[0018] According to one or more embodiments of the present invention, it is possible to provide a coil component that is compact while suppressing deterioration of inductance.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0020] Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. Note that the same reference numerals are given to common components in a plurality of drawings. It should be noted that each drawing is not necessarily drawn to an exact scale for convenience of explanation.

[0021] Referring to FIGS. 1 and 2, a coil component 1 according to an embodiment of the present invention will be described. FIG. 1 is a perspective view schematically showing the coil component 1, and FIG. 2 is a schematic plan view of the coil component 1. In FIG. 2, a transmission image of the magnetic substrate 10 and the coil conductor 25 is shown in a plan view (from the viewpoint in the direction of the coil axis Ax described later). In the illustrated embodiment, the coil component 1 is a planar coil having a coil conductor wound in a plurality of turns on a plane. The coil component 1 includes a magnetic substrate 10, a coil conductor 25 provided inside the magnetic substrate 10, an external electrode 21 provided on the surface of the magnetic substrate 10, and an external electrode 22 provided at a position spaced apart from the external electrode 21 on the surface of the substrate 10.

[0022] In this specification, unless otherwise understood from the context, the “length” direction, “width” direction, and “height” direction of the coil component 1 are the “L-axis” direction, “W-axis” direction, and “T-axis” direction in FIG. 1, respectively.

[0023] The coil component 1 is mounted on a mounting substrate. The circuit board in one embodiment of the present invention includes the coil component 1 and a mounting substrate on which the coil component 1 is mounted. In FIG. 1, the illustration of the mounting substrate is omitted. Two land portions are provided on the mounting substrate, and the coil component 1 is mounted on the mounting substrate by joining each of the external electrodes 21 and 22 to the corresponding land portion of the mounting substrate. The circuit board can be mounted on various electronic devices. Electronic devices on which the circuit board 2 can be mounted include smartphones, tablets, game consoles, automotive electrical components, and various other electronic devices.

[0024] The coil component 1 can be applied to inductors, transformers, filters, reactors, and various other coil components. The coil component 1 can also be applied to coupled inductors, choke coils, and various other magnetically coupled coil components. The coil component 1 may be, for example, an inductor used in a DC / DC converter. The use of the coil component 1 is not limited to those explicitly stated in this specification.

[0025] In one embodiment, the substrate 10 is mainly composed of a magnetic material and has a generally rectangular parallelepiped shape. In this specification, when referring to a "rectangular parallelepiped" or "rectangular parallelepiped shape", it does not mean only a "rectangular parallelepiped" in a strictly mathematical sense. The substrate 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 outer surface of the substrate 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b form the surfaces at both ends in the height direction, the first end surface 10c and the second end surface 10d form the surfaces at both ends in the length direction, and the first side surface 10e and the second side surface 10f form the surfaces at both ends in the width direction. The first main surface 10a faces the second main surface 10b, the first end surface 10c faces the second end surface 10d, and the first side surface 10e faces the second side surface 10f. The first end surface 10c connects the end of the first main surface 10a in the positive direction of the L axis and the end of the second main surface 10b in the positive direction of the L axis. The first main surface 10a, the second main surface 10b, the first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f are examples of the first surface, the second surface, the third surface, the fourth surface, the fifth surface, and the sixth surface in the claims, respectively.

[0026] In one embodiment, the first main surface 10a extends in the L-axis direction and the W-axis direction. In one embodiment, the dimension L1 of the first main surface 10a in the L-axis direction is larger than the dimension W1 in the W-axis direction. In one embodiment, the substrate 10 is formed such that the length dimension (dimension in the L-axis direction) L1 is 1.0 mm to 4.5 mm, the width dimension (dimension in the W-axis direction) W1 is 0.5 mm to 3.2 mm, and the height dimension (dimension in the T-axis direction) is 0.5 mm to 5.0 mm. The dimensions of the substrate 10 are not limited to the dimensions specifically described in this specification.

[0027] In one embodiment, the magnetic substrate 10 is made of a composite magnetic material including a plurality of metal magnetic particles and a binder. The metal magnetic particles may be mixed particles including a plurality of types of metal magnetic particles having different average particle diameters. When the metal magnetic particles include large-diameter metal magnetic particles and small-diameter metal magnetic particles, the average particle diameter of the large-diameter metal magnetic particles is, for example, 10 μm, and the average particle diameter of the small-diameter metal magnetic particles is, for example, 1 μm. The binder binds the plurality of metal magnetic particles to each other. The binder is, for example, a thermosetting resin having excellent insulation properties. The magnetic substrate 10 may be a compacted powder in which the metal magnetic particles are bonded to each other without passing through the binder. The metal magnetic particles are made of various soft magnetic materials. The metal magnetic particles are mainly composed of, for example, Fe. Specifically, the metal magnetic particles are (1) metal particles such as Fe and Ni, (2) crystalline alloy particles such as Fe-Si-Cr alloy, Fe-Si-Al alloy, and Fe-Ni alloy, (3) amorphous alloy particles such as Fe-Si-Cr-B-C alloy and Fe-Si-Cr-B alloy, or (4) mixed particles in which these are mixed. The composition of the metal magnetic particles included in the magnetic substrate 10 is not limited to the above. An insulating film made of glass, resin, or other materials having excellent insulation properties may be provided on the surface of each of the metal magnetic particles.

[0028] The coil conductor 25 has a winding portion 25a wound around a coil axis Ax extending along the thickness direction (T-axis direction), a lead-out portion 25b1 connecting one end of the winding portion 25a to the external electrode 21, and a lead-out portion 25b2 connecting the other end of the winding portion 25a to the external electrode 22. In the illustrated embodiment, the coil axis Ax intersects the first main surface 10a and the second main surface 10b, but does not intersect the first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f. In other words, the first end surface 10c, the second end surface 10d, the first side surface 10e, and the second side surface 10f extend along the coil axis Ax. In one embodiment, the coil axis Ax passes through the intersection of the two diagonal lines of the substrate 10 when the substrate 10 is viewed in plan.

[0029] In the illustrated embodiment, the winding portion 25a is wound around the coil axis Ax in a plurality of turns on a plane extending along the LW plane. In the illustrated embodiment, the winding portion 25a generally has an oval shape. The shape of the winding portion 25a is not limited to that shown. The shape of the winding portion 25a may be, for example, elliptical. In one embodiment, the winding portion 25a has a uniform cross-sectional area when cut in a direction perpendicular to the direction in which the current flows.

[0030] In one embodiment, in a plan view (i.e., from the viewpoint seen in the direction of the coil axis Ax), the winding portion 25a has a first portion 25a1 facing the first end face 10c, a second portion 25a2 facing the second end face 10d, a third portion 25a3 facing the first side face 10e, and a fourth portion 25a4 facing the second side face 10f.

[0031] In the illustrated embodiment, the first portion 25a1 of the first turn, counted from the lead-out portion 25b1, extends counterclockwise from one end to the other end, and is connected to the lead-out portion 25b1 at one end thereof. The third portion 25a3 of the first turn extends counterclockwise from one end to the other end, and is connected to the other end of the first portion 25a1 of the first turn at one end thereof. The second portion 25a2 of the first turn extends counterclockwise from one end to the other end, and is connected to the other end of the third portion 25a3 of the first turn at one end thereof. The fourth portion 25a4 of the first turn extends counterclockwise from one end to the other end, and is connected to the other end of the second portion 25a2 of the first turn at one end thereof. The first portion 25a1 of the second turn extends counterclockwise from one end to the other end, and is connected to the fourth portion 25a4 of the first turn at one end thereof. Similarly hereinafter, the winding portion 25a extends until it is connected to the lead-out portion 25b2. The third portion 25a3 and the fourth portion 25a4 each connect the first portion 25a1 and the second portion 25a2.

[0032] In one embodiment, as shown in the figure, the first portion 25a1 has a curved surface 26 that curves convexly toward the first end face 10c and faces the first end face 10c. In one embodiment, as shown in the figure, the second portion 25a2 has a curved surface 27 that curves convexly toward the second end face 10d and faces the second end face 10d. The curved surface 26 of the first portion 25a1 and the curved surface 27 of the second portion 25a2 may have the same or substantially the same radius of curvature. If the difference between the radius of curvature of the curved surface 26 of the first portion 25a1 and the radius of curvature of the curved surface 27 of the second portion 25a2 is 10% or less of the radius of curvature of the curved surface 26 of the first portion 25a1, it can be said that the radii of curvature of both are substantially the same.

[0033] In one embodiment, as shown in the figure, the third portion 25a3 extends parallel to the first side face 10e and has a plane 28 that faces the first side face 10e. The plane 28 may be all or part of the face of the third portion 25a3 that faces the first side face 10e. The face of the third portion 25a3 that faces the first side face 10e may be a composite surface where the plane 28 and the curved surface are connected. In one embodiment, the face of the third portion 25a3 that faces the first side face 10e may be a curved surface that curves convexly toward the first side face 10e.

[0034] In one embodiment, as shown in the figure, the fourth portion 25a4 extends parallel to the second side face 10f and has a plane 29 that faces the second side face 10f. Similar to the third portion 25a3, the plane 29 may be all or part of the face of the fourth portion 25a4 that faces the second side face 10f. The face of the fourth portion 25a4 that faces the second side face 10f may be a composite surface where the plane 29 and the curved surface are connected. In one embodiment, the face of the fourth portion 25a4 that faces the second side face 10f may be a curved surface that curves convexly toward the second side face 10f.

[0035] In one embodiment, the radius of curvature of the first portion 25a1 is smaller than either the radius of curvature of the third portion 25a3 or the radius of curvature of the fourth portion 25a4. In a more specific embodiment, the radius of curvature of the curved surface 27 of the first portion 25a1 is smaller than either the radius of curvature of the surface facing the first side surface 10e of the third portion 25a3 or the radius of curvature of the surface facing the second side surface 10f of the fourth portion 25a4. In one embodiment, the radius of curvature of the second portion 25a2 is smaller than either the radius of curvature of the third portion 25a3 or the radius of curvature of the fourth portion 25a4. In a more specific embodiment, the radius of curvature of the curved surface 27 of the second portion 25a2 is smaller than either the radius of curvature of the surface facing the first side surface 10e of the third portion 25a3 or the radius of curvature of the surface facing the second side surface 10f of the fourth portion 25a4. When the radius of curvature of the first portion 25a1 is not constant, the average of the radii of curvature at each of a plurality of points (for example, three points or five points) evenly distributed around the coil axis Ax in the first portion 25a1 may be used as the radius of curvature of the first portion 25a1, or the maximum value of the radius of curvature in the first portion 25a1 may be used as the radius of curvature of the first portion 25a1. Even when the radii of curvature of the second portion 25a2, the third portion 25a3, and the fourth portion 25a4 are not constant, the radii of curvature of the second portion 25a2, the third portion 25a3, and the fourth portion 25a4 can be determined in the same manner as when the radius of curvature of the first portion 25a1 is not constant.

[0036] In one embodiment, the first portion 25a1 includes the intersection point P1 of the perpendicular line dropped from the coil axis Ax to the first end surface 10c and the outermost turn of the circumferential portion 25a. In one embodiment, the second portion 25a2 includes the intersection point P2 of the perpendicular line dropped from the coil axis Ax to the second end surface 10d and the outermost turn of the circumferential portion 25a. In one embodiment, the third portion 25a3 includes the intersection point P3 of the perpendicular line dropped from the coil axis Ax to the first side surface 10e and the outermost turn of the circumferential portion 25a. In one embodiment, the fourth portion 25a4 includes the intersection point P4 of the perpendicular line dropped from the coil axis Ax to the second side surface 10f and the outermost turn of the circumferential portion 25a.

[0037] The boundaries between adjacent portions of the first portion 25a1, the second portion 25a2, the third portion 25a3, and the fourth portion 25a4 of the circumferential portion 25a can be defined, for example, as follows. When viewed in the direction of the coil axis Ax, virtual lines connecting the coil axis Ax and the four corners of the base 10 are defined, and these four virtual lines can be used as the boundary lines between the adjacent portions of the four portions of the first portion 25a1, the second portion 25a2, the third portion 25a3, and the fourth portion 25a4. For example, the virtual line connecting the upper left corner of the base 10 and the coil axis Ax from the perspective of FIG. 2 can be used as the boundary line between the first portion 25a1 and the fourth portion 25a4. Similarly, each of the virtual lines connecting the upper right corner, the lower right corner, and the lower left corner of the base 10 and the coil axis Ax from the perspective of FIG. 2 can be used as the boundary line between the fourth portion 25a4 and the second portion 25a2, the boundary line between the second portion 25a2 and the third portion 25a3, and the boundary line between the third portion 25a3 and the first portion 25a1.

[0038] In one embodiment, a first end margin E1 indicating the distance between the first portion 25a1 of the circumferential portion 25a and the first end face 10c of the base 10 is greater than either a first side margin S1 indicating the distance between the third portion 25a3 of the circumferential portion 25a and the first side face 10e of the base 10 or a second side margin S2 indicating the distance between the fourth portion 25a4 of the circumferential portion 25a and the second side face 10f of the base 10. In one embodiment, a second end margin E2 indicating the distance between the second portion 25a2 of the circumferential portion 25a and the second end face 10d of the base 10 is greater than either the first side margin S1 or the second side margin S2. In one embodiment, both the end margin E1 and the end margin E2 are in the range of 1.5 times to 10 times the side margin S1 and the side margin S2.

[0039] In one embodiment, the first end margin E1 and the second end margin E2 may be the same or substantially the same. When the difference between the first end margin E1 and the second end margin E2 is 10% or less of the first end margin E1, it can be said that the first end margin E1 and the second end margin E2 are substantially the same.

[0040] In one embodiment, the first side margin S1 and the second side margin S2 may be the same or substantially the same. When the difference between the first side margin S1 and the second side margin S2 is 10% or less of the first side margin S1, it can be said that the first side margin S1 and the second side margin S2 are substantially the same.

[0041] As shown, in one embodiment, the lead-out portion 25b1 extends along the coil axis Ax. In one embodiment, the lead-out portion 25b2 extends along the coil axis Ax. When the area occupied by the lead-out portion in a cross-section perpendicular to the coil axis Ax increases, there is a risk that the inductance of the coil component 1 deteriorates because the lead-out portion inhibits the passage of magnetic flux. According to the illustrated embodiment, since one end of the circumferential portion 25a and the external electrode 21 are connected by the lead-out portion 25b1 extending along the coil axis Ax, it is possible to suppress the deterioration of the inductance due to the lead-out portion connecting one end of the circumferential portion 25a and the external electrode 21. Further, according to the illustrated embodiment, since the other end of the circumferential portion 225a and the external electrode 22 are connected by the lead-out portion 25b2 extending along the coil axis Ax, it is possible to suppress the deterioration of the inductance due to the lead-out portion connecting the other end of the circumferential portion 25a and the external electrode 21.

[0042] In one embodiment, the ratio of the area of the circumferential portion 25a to the area of the first main surface 10a as viewed from the direction of the coil axis Ax is 0.3 or more. When the shape of the first main surface 10a as viewed from the direction of the coil axis Ax is rectangular, and the dimension in the L-axis direction is L1 and the dimension in the W-axis direction is W1, the area S1 of the first main surface 10a as viewed from the direction of the coil axis Ax is S1 = L1 × W1. Let the area of the circumferential portion 25a as viewed from the direction of the coil axis Ax be S2. In one embodiment, S2 / S1 is 0.3 or more. There is a demand for a coil component that can pass a large current while maintaining a compact external dimension. In order to realize such a coil component, the cross-sectional area of the coil conductor tends to increase. When the cross-section of the coil conductor increases, the area S2 of the circumferential portion 25a as viewed from the direction of the coil axis Ax also increases. In particular, when S2 increases so that S2 / S1 is 0.3 or more, if the side margin and the end margin are made the same, there is a risk that the region through which the magnetic flux passes is not sufficiently secured and the inductance deteriorates. Therefore, when S2 / S1 is 0.3 or more, it is effective to optimize the ratio of the side margin to the end margin to ensure a sufficient area for the magnetic flux to pass through. If S2 / S1 is less than 0.3, even if the side margin and the end margin are designed to be the same, the region through which the magnetic flux passes is sufficiently secured, so the inductance does not deteriorate to a level that causes a practical problem.

[0043] Next, an example of a method for manufacturing the coil component 1 according to an embodiment of the present invention will be described. Hereinafter, an example of a method for manufacturing the coil component 1 by a compression molding process will be described. First, metal magnetic particles are prepared. An insulating film may be provided on the surface of the metal magnetic particles as necessary. These metal magnetic particles may be mixed particles obtained by mixing multiple types of particles having different average particle diameters. Next, the prepared metal magnetic particles, a resin material, and a diluting solvent are mixed to create a composite magnetic material. The above composite magnetic material is placed in a molding die in which a coil conductor 25 prepared in advance is installed, and for example, a molding pressure is applied in a temperature range of 50°C to 150°C, and then heated from 150°C to 400°C to cure, thereby obtaining a magnetic substrate 10 containing the coil conductor 25 inside. The coil conductor 25 is configured and arranged such that when viewed from the direction of the coil axis Ax, the first end margin E1 and the second end margin E2 are larger than either the first side margin S1 or the second side margin S2.

[0044] The heat treatment for obtaining the magnetic substrate 10 may be performed in two steps or one step as described above. When the heat treatment is performed in one step, molding and curing are performed during the heat treatment. In the substrate 10, the resin contained in the composite magnetic material is cured to become a binder. The substrate 10 may be molded, for example, in a temperature range around 80°C. The molding pressure is, for example, set to 50 MPa to 200 MPa. The molding pressure can be appropriately adjusted to obtain a desired filling rate. The molding pressure is, for example, set to 100 MPa.

[0045] Next, external electrodes 21 and 22 are formed by applying a conductor paste to the surface of the magnetic substrate 10 obtained as described above. The external electrode 21 is electrically connected to one end of the coil conductor 25 provided inside the magnetic substrate 10, and the external electrode 22 is electrically connected to the other end of the coil conductor 25 provided inside the magnetic substrate 10. Thus, the coil component 1 is obtained.

[0046] The manufactured coil component 1 is mounted on a mounting substrate by a reflow process. In this case, after the mounting substrate on which the coil component 1 is disposed passes through a reflow furnace heated to a peak temperature of, for example, 260°C at high speed, the external electrodes 21 and 22 are soldered to the land portions of the mounting substrate, respectively, whereby the coil component 1 is mounted on the mounting substrate and a circuit board is manufactured.

[0047] Subsequently, the inductor characteristics of the coil component 1 in one embodiment will be described. For the simulation of the inductor characteristics, four evaluation models (evaluation model #1 to evaluation model #4) were constructed. Each of evaluation model #1 to evaluation model #4 models the coil component 1. Each of evaluation model #1 to evaluation model #4 has a rectangular parallelepiped base corresponding to the base 10, a conductor corresponding to the coil conductor 25, and two electrodes corresponding to the external electrodes 21 and 22, respectively. The length dimension (dimension in the L-axis direction) of the base was set to 2.0 mm, the width dimension (dimension in the W-axis direction) was set to 1.2 mm, and the height dimension (dimension in the T-axis direction) was set to 1.2 mm. In each evaluation model, the conductor corresponding to the coil conductor 25 is wound 10.5 turns around the coil axis corresponding to the coil axis Ax. In evaluation model #1, the distance from the conductor to the surface of the base when viewed from the direction of the coil axis was set to 0.25 mm for all. That is, in evaluation model #1, both the end margin and the side margin were set to 0.25 mm. In each evaluation model, when the end margin and the side margin are equal to each other, the end margin (or the side margin) is referred to as the reference margin. In evaluation models #2 to #4, the reference margins were set to 0.2 mm, 0.15 mm, and 0.1 mm, respectively.

[0048] For each of the evaluation models #1 to #4 configured as described above, while maintaining the total of the end margin and the side margin at a constant value (twice the reference margin), the end margin and the side margin were increased and decreased by 0.05 mm each, and the inductance L after changing the end margin and the side margin in this way was calculated by simulation. The results of this simulation are shown in FIG. 3. FIG. 3 is a graph showing the simulation results of the inductance L of the evaluation models #1 to #4. The horizontal axis shows the ratio of the end margin E to the side margin S on a logarithmic scale, and the vertical axis shows the calculated inductance. In FIG. 3, for the evaluation model #1 with a reference margin of 0.25 mm, the simulation result of the inductance when the end margin is equal to the reference margin is plotted at the origin (E / S = 1) of the X-axis. One position to the right of the plot placed at this origin is the simulation result of the inductance when the end margin is increased by 0.05 from the reference margin to 0.30 mm and the side margin is decreased by 0.05 from the reference margin to 0.20 mm, and is plotted at the position X = 1.5 (= 0.3 / 0.2) of the X-axis. Other simulation results were calculated in the same way, and the calculated simulation results are plotted on the graph of FIG. 3. When the end margin or the side margin becomes zero by decreasing 0.05 mm, 0.01 was adopted instead of zero for calculation convenience.

[0049] As shown in the figure, it was found that in any case where the reference margin is 0.10 to 0.25 mm, the inductance is improved by making the dimension corresponding to the end margin larger than the side margin.

[0050] Subsequently, referring to FIGS. 4 and 5, the coil component 101 according to another embodiment of the present invention will be described. The coil component 101 is different from the coil component 1 having the coil conductor 25a wound in a plurality of turns in a plane in that it includes a coil conductor wound in a spiral shape.

[0051] As shown in FIGS. 4 and 5, the coil component 101 includes a coil conductor 125 provided in a magnetic substrate 110, an external electrode 121 provided on the magnetic substrate 110, and an external electrode 122 provided on the magnetic substrate 110 and spaced apart from the external electrode 121. The magnetic substrate 110 is formed of a magnetic material in the same manner as the magnetic substrate 10.

[0052] The coil component 101 may be mounted on a mounting substrate 2a. Two land portions 3 are provided on the mounting substrate 2a. The coil component 1 is mounted on the mounting substrate 2a by joining each of the external electrodes 21 and 22 to the corresponding land portion 3 of the mounting substrate 2a. By mounting the coil component 101 on the mounting substrate 2a, a circuit board 2 is configured. The circuit board 2 includes the coil component 101 and the mounting substrate 2a on which this coil component 1 is mounted. The circuit board 2 can include electronic components other than the coil component 101.

[0053] The magnetic substrate 110 generally has a rectangular parallelepiped shape. The magnetic substrate 110 has a first main surface 110a, a second main surface 110b, a first end surface 110c, a second end surface 110d, a first side surface 110e, and a second side surface 110f. The outer surface of the magnetic substrate 110 is defined by these six surfaces. The first main surface 110a and the second main surface 110b respectively form surfaces at both ends in the height direction, the first end surface 110c and the second end surface 110d respectively form surfaces at both ends in the length direction, and the first side surface 110e and the second side surface 110f respectively form surfaces at both ends in the width direction. The description regarding the magnetic substrate 10 also applies to the magnetic substrate 110 as much as possible.

[0054] The coil conductor 125 has a winding portion 125a wound in a spiral around a coil axis Ax extending along the thickness direction (T direction), a lead-out portion 125b1 connecting one end of the winding portion 125a to the external electrode 121, and a lead-out portion 125b2 connecting the other end of the winding portion 125a to the external electrode 122.

[0055] The circumferential portion 125a, similar to the circumferential portion 25a, has a first portion 125a1 facing the first end face 110c, a second portion 125a2 facing the second end face 110d, a third portion 125a3 facing the first side face 110e, and a fourth portion 125a4 facing the second side face 110f. In the illustrated embodiment, the fourth portion 125a4 of the first turn, counted from the lead-out portion 125b1, extends clockwise from one end to the other end, and is connected to the lead-out portion 125b1 at one end thereof. The second portion 125a2 of the first turn extends clockwise from one end to the other end, and is connected to the other end of the fourth portion 125a4 of the first turn at one end thereof. The third portion 125a3 of the first turn extends clockwise from one end to the other end, and is connected to the other end of the second portion 125a2 of the first turn at one end thereof. The first portion 125a1 of the first turn extends clockwise from one end to the other end, and is connected to the other end of the third portion 125a3 of the first turn at one end thereof. The third portion 125a3 of the second turn extends clockwise from one end to the other end, and is connected to the other end of the first portion 125a1 of the first turn at one end thereof. Similarly hereinafter, the circumferential portion 125a extends until it is connected to the lead-out portion 125b2. As described above, the third portion 125a3 and the fourth portion 125a4 each connect the first portion 125a1 and the second portion 125a2. The boundaries between adjacent portions of the first portion 125a1, the second portion 125a2, the third portion 125a3, and the fourth portion 125a4 can be defined in the same manner as the boundaries of the respective portions of the circumferential portion 25a. For example, when viewed from the direction of the coil axis Ax, virtual lines connecting the coil axis Ax and the four corners of the base 110 are defined, and these four virtual lines can be used as the boundary lines between each of the four portions of the first portion 125a1, the second portion 125a2, the third portion 125a3, and the fourth portion 125a4 and their adjacent portions.

[0056] In one embodiment, as shown in the figure, the first portion 125a1 has a curved surface 126 that curves convexly toward the first end face 110c and faces the first end face 110c. In one embodiment, as shown in the figure, the second portion 125a2 has a curved surface 127 that curves convexly toward the second end face 110d and faces the second end face 110d. In one embodiment, as shown in the figure, the third portion 125a3 has a curved surface 128 that curves convexly toward the first side face 110e and faces the first side face 110e. In one embodiment, as shown in the figure, the fourth portion 125a4 has a curved surface 129 that curves convexly toward the second side face 110f and faces the second side face 110f.

[0057] In one embodiment, the radius of curvature of the first portion 125a1 is smaller than either the radius of curvature of the third portion 125a3 or the fourth portion 125a4. In a more specific embodiment, the radius of curvature of the curved surface 126 of the first portion 125a1 is smaller than either the radius of curvature of the curved surface 128 of the third portion 125a3 or the radius of curvature of the curved surface 129 of the fourth portion 125a4. In one embodiment, the radius of curvature of the second portion 125a2 is smaller than either the radius of curvature of the third portion 125a3 or the fourth portion 125a4. In a more specific embodiment, the radius of curvature of the curved surface 127 of the second portion 125a2 is smaller than either the radius of curvature of the curved surface 128 of the third portion 125a3 or the radius of curvature of the curved surface 129 of the fourth portion 125a4. When the radius of curvature of the first portion 125a1 is not constant, the average of the radii of curvature at a plurality of points (for example, three points or five points) evenly distributed around the coil axis Ax in the first portion 125a1 may be used as the radius of curvature of the first portion 125a1, or the maximum value of the radius of curvature in the first portion 125a1 may be used as the radius of curvature of the first portion 125a1. When the radii of curvature of the second portion 125a2, the third portion 125a3, and the fourth portion 125a4 are not constant, the radii of curvature of the second portion 125a2, the third portion 125a3, and the fourth portion 125a4 can be determined in the same manner as when the radius of curvature of the first portion 125a1 is not constant.

[0058] The arrangement of the circumferential portion 125a with respect to the base 110 in the coil component 101 is the same as the arrangement of the circumferential portion 25a with respect to the base 10 in the coil component 1 described above. For example, in one embodiment, a first end margin E1 indicating the distance between the first portion 125a1 of the circumferential portion 125a and the first end face 110c of the base 110 is greater than either a first side margin S1 indicating the distance between the third portion 125a3 of the circumferential portion 125a and the first side face 110e of the base 110 or a second side margin S2 indicating the distance between the fourth portion 125a4 of the circumferential portion 125a and the second side face 110f of the base 110. Also, in one embodiment, a second end margin E2 indicating the distance between the second portion 125a2 of the circumferential portion 125a and the second end face 110d of the base 110 is greater than either the first side margin S1 or the second side margin S2.

[0059] The coil component 101 can be manufactured by a compression molding process in the same manner as the coil component 1. The manufactured coil component 101 is mounted on the mounting substrate 2 by a reflow process. In this case, after the substrate 2 on which the coil component 1 is arranged passes through a reflow furnace heated to a peak temperature of, for example, 260°C at high speed, the external electrodes 121 and 122 are soldered to the land portions 3 of the substrate 2, respectively, so that the coil component 101 is mounted on the mounting substrate 2a and the circuit board 2 is manufactured.

[0060] Subsequently, with reference to FIGS. 6 to 8, a coil component 201 according to another embodiment of the present invention will be described. The coil component 201 is a multilayer coil. As shown in the figure, the coil component 201 includes a magnetic base 210, a coil conductor 225 provided in the magnetic base 210, an external electrode 221 provided on the magnetic base 210, and an external electrode 222 provided on the magnetic base 210 and spaced apart from the external electrode 221. The magnetic base 210 is made of a magnetic material in the same manner as the magnetic base 10.

[0061] The magnetic substrate 210 is formed in a rectangular parallelepiped shape from a magnetic material. The magnetic substrate 210 includes a magnetic layer 220 in which the coil 225 is embedded, an upper cover layer 218 made of a magnetic material provided on the upper surface of the magnetic layer 220, and a lower cover layer 219 made of a magnetic material provided on the lower surface of the magnetic layer 220. The upper cover layer 218 includes magnetic films 218a to 218d made of a magnetic material, and the lower cover layer 219 includes magnetic films 219a to 219d made of a magnetic material. Depending on the manufacturing method of the magnetic substrate 10, the boundary between the magnetic layer 220 and the upper cover layer 218 and the boundary between the magnetic layer 220 and the lower cover layer 219 may not be clearly confirmed. The magnetic substrate 210 generally has a rectangular parallelepiped shape and has a first main surface 210a, a second main surface 210b, a first end surface 210c, a second end surface 210d, a first side surface 210e, and a second side surface 210f. The outer surface of the magnetic substrate 210 is defined by these six surfaces. The first main surface 210a and the second main surface 210b form the surfaces at both ends in the height direction, the first end surface 210c and the second end surface 210d form the surfaces at both ends in the length direction, and the first side surface 210e and the second side surface 210f form the surfaces at both ends in the width direction. The description regarding the magnetic substrate 10 applies to the magnetic substrate 210 as much as possible.

[0062] The magnetic layer 220 includes magnetic films 211 to 214. In the magnetic layer 220, the magnetic films 211, 212, 213, and 214 are laminated in this order from the positive direction side to the negative direction side in the T-axis direction. Conductor patterns C11 to C14 are formed on the upper surfaces of the magnetic films 211 to 214. The conductor patterns C11 to C14 are formed, for example, by printing a conductive paste made of a metal or alloy having excellent conductivity by a screen printing method. As the material of this conductive paste, Ag, Pd, Cu, Al, or an alloy thereof can be used.

[0063] At predetermined positions of the magnetic films 211 to 213, vias V1 to V3 are respectively formed. The vias V1 to V3 are formed by forming through holes penetrating the magnetic films 211 to 213 in the T-axis direction at the predetermined positions of the magnetic films 211 to 213 and embedding a conductive material in the through holes. Each of the conductor patterns C11 to C14 is electrically connected to an adjacent conductor pattern via the vias V1 to V3. The conductor patterns C11 to C14 connected in this way form a spiral coil conductor 225.

[0064] As shown in FIG. 7, the coil conductor 225 has a winding portion 225a wound in a spiral around a coil axis Ax extending along the thickness direction (T direction), a lead-out portion 225b1 connecting one end of the winding portion 225a to the external electrode 221, and a lead-out portion 225b2 connecting the other end of the winding portion 225a to the external electrode 222.

[0065] Similar to the circumferential portion 25a, the circumferential portion 225a has a first portion 225a1 facing the first end face 210c, a second portion 225a2 facing the second end face 210d, a third portion 225a3 facing the first side face 210e, and a fourth portion 225a4 facing the second side face 210f. In the illustrated embodiment, the first portion 225a1 of the first turn extends clockwise from one end to the other end and is connected to the lead-out portion 225b1 at one end thereof. The fourth portion 225a4 of the first turn extends clockwise from one end to the other end and is connected to the other end of the first portion 225a1 of the first turn at one end thereof. The second portion 225a2 of the first turn extends clockwise from one end to the other end and is connected to the other end of the fourth portion 225a4 of the first turn at one end thereof. The third portion 125a4 of the first turn extends clockwise from one end to the other end and is connected to the other end of the second portion 125a2 at one end thereof. The first portion 225a1 of the second turn extends clockwise from one end to the other end and is connected to the other end of the third portion 125a3 of the first turn at one end thereof. Similarly hereinafter, the circumferential portion 225a extends until it is connected to the lead-out portion 225b2. As described above, the third portion 225a3 and the fourth portion 225a4 connect the first portion 225a1 and the second portion 225a2, respectively. The boundaries between adjacent portions of the first portion 225a1, the second portion 225a2, the third portion 225a3, and the fourth portion 225a4 can be defined in the same manner as the boundaries of the respective portions of the circumferential portion 25a. For example, when viewed in the direction of the coil axis Ax, virtual lines connecting the coil axis Ax and the four corners of the base body 210 are defined, and these four virtual lines can be used as the boundary lines between each of the four portions of the first portion 225a1, the second portion 225a2, the third portion 225a3, and the fourth portion 225a4 and its adjacent portion.

[0066] In one embodiment, as shown, the first portion 225a1 has a curved surface 226 that curves convexly toward the first end face 210c and faces the first end face 210c. In one embodiment, as shown, the second portion 225a2 has a curved surface 227 that curves convexly toward the second end face 210d and faces the second end face 210d. In one embodiment, as shown, the third portion 225a3 has a curved surface 228 that curves convexly toward the first side face 210e and faces the first side face 210e. In one embodiment, as shown, the fourth portion 225a4 has a curved surface 229 that curves convexly toward the second side face 210f and faces the second side face 210f.

[0067] In one embodiment, the radius of curvature of the first portion 225a1 is smaller than either the radius of curvature of the third portion 225a3 or the fourth portion 225a4. In a more specific embodiment, the radius of curvature of the curved surface 226 of the first portion 225a1 is smaller than either the radius of curvature of the curved surface 128 of the third portion 225a3 or the radius of curvature of the curved surface 229 of the fourth portion 225a4. In one embodiment, the radius of curvature of the second portion 225a2 is smaller than either the radius of curvature of the third portion 225a3 or the fourth portion 225a4. In a more specific embodiment, the radius of curvature of the curved surface 227 of the second portion 225a2 is smaller than either the radius of curvature of the curved surface 228 of the third portion 225a3 or the radius of curvature of the curved surface 229 of the fourth portion 225a4. When the radius of curvature of the first portion 225a1 is not constant, the average of the radii of curvature at a plurality of points (for example, 3 points or 5 points) evenly distributed around the coil axis Ax in the first portion 225a1 may be used as the radius of curvature of the first portion 225a1, or the maximum value of the radius of curvature in the first portion 225a1 may be used as the radius of curvature of the first portion 225a1. When the radii of curvature of the second portion 225a2, the third portion 225a3, and the fourth portion 225a4 are not constant, the radii of curvature of the second portion 225a2, the third portion 225a3, and the fourth portion 225a4 can be determined in the same manner as when the radius of curvature of the first portion 225a1 is not constant.

[0068] The arrangement of the circumferential portion 225a with respect to the base 210 in the coil component 201 is the same as the arrangement of the circumferential portion 25a with respect to the base 10 in the coil component 1 described above. For example, in one embodiment, a first end margin E1 indicating the distance between the first portion 225a1 of the circumferential portion 225a and the first end face 210c of the base 210 is greater than either a first side margin S1 indicating the distance between the third portion 225a3 of the circumferential portion 225a and the first side face 210e of the base 210 or a second side margin S2 indicating the distance between the fourth portion 225a4 of the circumferential portion 225a and the second side face 210f of the base 210. Also, in one embodiment, a second end margin E2 indicating the distance between the second portion 225a2 of the circumferential portion 225a and the second end face 210d of the base 210 is greater than either the first side margin S1 or the second side margin S2.

[0069] Next, an example of a method for manufacturing the coil component 201 will be described. The coil component 201 can be manufactured, for example, by a lamination process. Hereinafter, an example of a method for manufacturing the coil component 201 by a lamination process will be described.

[0070] First, magnetic sheets that will become the magnetic films 18a to 18d constituting the upper cover layer 218, the magnetic films 11 to 14 constituting the magnetic body layer 220, and the magnetic films 19a to 19d constituting the lower cover layer 219 are created. These magnetic sheets are formed from a composite magnetic material containing a binder and metal magnetic particles. The magnetic sheet for the coil component 201 can be created in the same manner as the magnetic sheet used in the manufacturing process of the coil component 1.

[0071] Next, a coil conductor is provided on the magnetic sheet. Specifically, through holes penetrating each magnetic sheet in the T-axis direction are formed at predetermined positions of each magnetic sheet that will become the magnetic films 11 to 13. Next, an unfired conductor pattern is formed on the upper surface of each of the magnetic sheets that will become the magnetic films 11 to 14 by printing a conductive paste by a screen printing method. Also, the conductive paste is embedded in each through hole formed in each magnetic sheet.

[0072] Next, magnetic sheets to become magnetic films 11 to 14 are laminated to obtain a coil laminate. Each of the magnetic sheets to become magnetic films 11 to 14 is laminated such that each of the unfired conductor patterns C11 to C14 formed on each of the magnetic sheets is electrically connected to an adjacent conductor pattern via unfired vias V1 to V3.

[0073] Next, a plurality of magnetic sheets are laminated to form an upper laminate that becomes the upper cover layer 18. Also, a plurality of magnetic sheets are laminated to form a lower laminate that becomes the lower cover layer 19.

[0074] Next, the lower laminate, the coil laminate, and the upper laminate are laminated in this order from the negative direction side to the positive direction side of the T-axis direction, and the laminated laminates are thermocompression bonded by a press machine to obtain a main body laminate. The main body laminate may be formed by laminating all the prepared magnetic sheets in order without forming the lower laminate, the coil laminate, and the upper laminate, and then thermocompression bonding the laminated magnetic sheets all at once.

[0075] Next, the main body laminate is diced into individual pieces of a desired size using a cutting machine such as a dicing machine or a laser processing machine to obtain a chip laminate. Next, the chip laminate is degreased, and the degreased chip laminate is heat-treated. A polishing process such as barrel polishing is performed on the ends of the chip laminate as necessary.

[0076] Next, external electrodes 221 and 222 are formed by applying conductor paste to both ends of the chip laminate. Thus, the coil component 201 is obtained.

[0077] Next, the effects of the above-described embodiments will be described. In a conventional coil component, in order to effectively use each region of the base magnetically, the end margin and the side margin are designed to be the same in order to avoid magnetic flux concentration in a specific region of the base. Further, in a conventional coil component, in order to prevent the circumferential portion of the coil conductor from being exposed from the base and to prevent a short circuit between the circumferential portion and an external conductive member, a certain margin is provided between the circumferential portion and the end face and side face of the base. When the coil component is manufactured by a lamination process, the printing of the conductor pattern may be displaced from the initial position, the positions of the magnetic sheet layers may be displaced when a plurality of magnetic sheets are laminated, or the dicing position may be displaced when individual pieces are separated in the manufacturing process. Since such displacement occurs evenly in the length direction (L-axis direction) and the width direction (W-axis direction), the margin provided between the circumferential portion and the surface of the base is set to be the same in the length direction and the width direction in order to avoid problems (e.g., exposure of the circumferential portion) due to such displacement. When the coil component is manufactured by a compression molding process using a mold, a certain distance is required between the wall portion of the mold into which the composite magnetic material is inserted and the circumferential portion of the coil conductor inserted into the mold. The distance required between the wall portion of the mold and the circumferential portion is also the same in the length direction and the width direction. As described above, a conventional coil component is designed such that the end margin and the side margin are the same or substantially the same. On the other hand, the coil conductor may have a shape in which the dimension in one direction perpendicular to the coil conductor is larger than the dimension in the other direction perpendicular to the coil conductor, such as an oval or an ellipse, when viewed from the coil axis direction. For this reason, the circumferential portion of the coil conductor may have a portion having a relatively small radius of curvature and a portion having a relatively large radius of curvature. When the current flowing through the coil conductor changes, magnetic flux is more likely to concentrate around the portion having a relatively small radius of curvature than around the portion having a relatively large radius of curvature. In one or more embodiments of the present invention, the circumferential portions 25a, 125a, 225a have a first portion 25a1, 125a1, 225a1 and a second portion 25a2, 125a2, 225a2 having a relatively small radius of curvature, and a third portion 25a3, 125a3, 225a3 and a fourth portion 25a4, 125a4, 225a4 having a relatively large radius of curvature.Therefore, in the substrates 10, 110, and 210, magnetic flux is likely to concentrate in the regions between the first portions 25a1, 125a1, 225a1 and the first end faces 10c, 110c, 210c, and between the second portions 25a2, 125a2, 225a2 and the second end faces 10d, 110d, 210d.

[0078] In one or more embodiments of the present invention, an end margin E1, which is the distance between the first portions 25a1, 125a1, 225a1 of the circumferential portions 25a, 125a, 225a and the first end faces 10c, 110c, 210c, is greater than a side margin S1, which is the distance between the third portions 25a3, 125a3, 225a3 and the first side faces 10e, 110e, 210e, and a side margin S2, which is the distance between the fourth portions 25a4, 125a4, 225a4. Therefore, concentration of magnetic flux in the regions between the first portions 25a1, 125a1, 225a1, which have relatively small radii of curvature among the circumferential portions 25a, 125a, 225a, and the surfaces of the substrates 10, 110, 210 can be suppressed. Also, in one or more embodiments of the present invention, an end margin E2, which is the distance between the second portions 25a2, 125a2, 225a2 of the circumferential portions 25a, 125a, 225a and the second end faces 10d, 110d, 210d, is greater than the side margin S1 and the side margin S2. Therefore, concentration of magnetic flux in the regions between the second portions 25a2, 125a2, 225a2, which have relatively small radii of curvature among the circumferential portions 25a, 125a, 225a, and the surfaces of the substrates 10, 110, 210 can be suppressed.

[0079] Further, in one or more embodiments of the present invention, since the side margins S1 and S2 are smaller than the end margins E1 and E2, the outer dimensions of the substrate can be reduced as compared with a conventional coil component in which the side margin and the end margin are equal. In other words, by selectively increasing the end margin E1 contributing to the area of the region between the first portions 25a1, 125a1, 225a1 where magnetic flux is likely to concentrate and the first end faces 10c, 110c, 210c and the end margin E2 contributing to the area of the region between the second portions 25a2, 125a2, 225a2 and the second end faces 10d, 110d, 210d, it is possible to suppress the deterioration of inductance without increasing the dimension in the width direction of the substrate 10.

[0080] Thus, according to one or more embodiments of the present invention, by making the end margins E1 and E2 larger than the side margins S1 and S2, the concentration of magnetic flux in the region between the first portions 25a1, 125a1, 225a1 and the first end faces 10c, 110c, 210c and the region between the second portions 25a2, 125a2, 225a2 and the second end faces 10d, 110d, 210d is suppressed, the deterioration of inductance is suppressed, and the outer dimensions of the substrates 10, 110, 210 can be reduced. Therefore, according to one or more embodiments of the present invention, it is possible to provide the coil components 1, 101, 201 which are compact while suppressing the deterioration of inductance.

[0081] The dimensions, materials, and arrangements of the respective components described in the various embodiments above are not limited to those explicitly described in each embodiment, and each of these components can be modified to have any dimensions, materials, and arrangements that can be included in the scope of the present invention. Further, components not explicitly described in this specification can be added to each of the above embodiments, or a part of the components described in each embodiment can be omitted.

Description of Reference Numerals

[0082] 1, 101, 201 Coil component 10, 110, 210 Magnetic substrate 21, 22, 121, 122, 221, 222 External electrodes 25, 125, 225 Coil conductors Ax Coil axis E1, E2 End margins S1, S2 Side margins

Claims

1. A first surface extending in a first direction and a second direction orthogonal to the first direction, wherein a first dimension in the first direction is larger than a second dimension in the second direction; a second surface facing the first surface; a third surface connecting an end of the first surface in the first direction and an end of the second surface in the first direction; a fourth surface facing the third surface; a fifth surface connecting the third surface and the fourth surface; and a sixth surface facing the fifth surface, a substrate made of a magnetic material, A coil conductor having a circumferential portion extending around a coil axis intersecting the first surface and the second surface, and configured not to have a portion bent at an acute angle, A first external electrode provided on the substrate and electrically connected to one end of the coil conductor, A second external electrode provided on the substrate and electrically connected to the other end of the coil conductor, Comprising, When viewed from the direction of the coil axis, the circumferential portion has a first portion facing the third surface and curving toward the third surface, a second portion facing the fourth surface and curving toward the fourth surface, a third portion connecting the first portion and the second portion and facing the fifth surface, and a fourth portion connecting the first portion and the second portion and facing the sixth surface, The radii of curvature of the first portion and the second portion are both smaller than the radii of curvature of the third portion and the fourth portion, When viewed from the direction of the coil axis, the distance between the first portion and the third surface and the distance between the second portion and the fourth surface are both larger than the distance between the third portion and the fifth surface and the distance between the fourth portion and the sixth surface, The distance between the first portion and the third surface and the distance between the second portion and the fourth surface are both in the range of 1.5 times to 10 times the distance between the third portion and the fifth surface and the distance between the fourth portion and the sixth surface, The area of the circumferential portion viewed from the direction of the coil axis with respect to the area of the first surface viewed from the direction of the coil axis is 0.3 or more, A coil component.

2. When viewed from the direction of the coil axis, the distance between the first portion of the circumferential portion and the third surface is substantially equal to the distance between the second portion of the circumferential portion and the fourth surface, The coil component according to Claim 1.

3. When viewed from the direction of the coil axis, the distance between the third portion of the circumferential portion and the fifth surface is substantially equal to the distance between the fourth portion of the circumferential portion and the sixth surface, The coil component according to claim 1 or 2.

4. The circumferential portion has a uniform cross-sectional area, and the coil component according to any one of claims 1 to 3.

5. The first external electrode is connected to one end of the circumferential portion by a first lead portion extending along the coil axis. The coil component according to any one of claims 1 to 4.

6. The second external electrode is connected to the other end of the circumferential portion by a second lead portion extending along the coil axis. The coil component according to any one of claims 1 to 5.

7. A DC / DC converter including the coil component according to any one of claims 1 to 6.

8. The coil component according to any one of claims 1 to 7, and a mounting substrate joined to the first external electrode and the second external electrode by solder. A circuit board comprising the same.

9. An electronic device including the circuit board according to claim 8.

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