Coil components, circuit boards, and electronic devices

Abstract

The present invention provides a coil component, a circuit board, and an electronic device. A coil component according to one embodiment of the present invention includes: a substrate comprising a plurality of metal magnetic particles and a binding material for binding the plurality of metal magnetic particles, and having a first surface extending along a coil axis and a second surface opposite to the first surface; a first external electrode provided on the substrate; a second external electrode provided on the substrate; and a coil conductor electrically connected to the first external electrode and the second external electrode, extending around the coil axis. In one embodiment, the coil conductor has a winding portion formed by alternatingly connecting a plurality of first conductor portions and a smaller number of second conductor portions than the first conductor portions, wherein the distance between the first conductor portion and the first surface is smaller than the distance between the second conductor portion and the second surface.

Description

Technical Field

[0001] The present invention relates to a coil component, a circuit board and an electronic device. Background Art

[0002] Conventionally, there is known a coil component including: a magnetic base formed of a magnetic material; an external electrode provided on a surface of the magnetic base; and a coil conductor extending around a coil axis within the magnetic base.

[0003] An example of a coil component is an inductor. An inductor is a passive component used in electronic circuits. For example, an inductor can be used to remove noise in a power line or a signal line. A conventional inductor has been disclosed in Japanese Patent Application Publication No. 2018-101732 (Patent Document 1). As disclosed in Patent Document 1, a more compact inductor is required. In addition, the coil component is required to have high inductance.

[0004] As a magnetic matrix for electronic components such as inductors, a metal composite type magnetic matrix is ​​known. In a metal composite type magnetic matrix, a large number of metal magnetic particles are bonded using a binding material composed of a resin material. A metal composite type magnetic matrix can be produced, for example, by flowing a sealing material containing a metal magnetic material and a resin into a mold provided with a conductor, and pressurizing the sealing material and the conductor in the mold. A metal composite type magnetic matrix has been disclosed in Japanese Patent Application Publication No. 2016-208002 (Patent Document 2) and Japanese Patent Application Publication No. 2018-041955 (Patent Document 3).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2018-101732

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-208002

[0009] Patent Document 3: Japanese Patent Application Laid-Open No. 2018-041955 Summary of the Invention

[0010] Technical problem to be solved by the invention

[0011] Metal-composite magnetic substrates contain a binder made of a resin material, making them water-absorbent. Consequently, moisture is contained within the magnetic substrate. When a coil component including this metal-composite magnetic substrate is mounted on a substrate through a reflow soldering process, the temperature of the magnetic substrate rises dramatically. Consequently, moisture contained within the magnetic substrate migrates to the surface and evaporates from the surface into the atmosphere. When moisture migrating from the interior of the magnetic substrate to the surface concentrates within a certain path within the magnetic substrate, the pressure in that path increases, making microcracks more likely to form around that path.

[0012] When microcracks are generated in the magnetic base, the inductance of the coil component decreases. When evaporating moisture from the magnetic base, it is desirable that the moisture migrate from the interior of the magnetic base to the surface via a plurality of dispersed pathways.

[0013] One of the purposes of the invention disclosed in this specification is to solve or alleviate the above-mentioned problems in the conventional coil components. One of the more specific purposes of the invention disclosed in this specification is to prevent the moisture from being concentrated in a part of the path when the moisture moves from the inside of the magnetic substrate to the surface. The purposes other than the above-mentioned purposes of the invention disclosed in this specification will become clear by referring to the entire specification. The invention disclosed in this specification may not solve the above-mentioned technical problems but solve the technical problems that can be grasped according to the description of this specification, or solve the technical problems that can be grasped according to the description of this specification in addition to the above-mentioned technical problems.

[0014] Means for solving technical problems

[0015] A coil component according to one embodiment of the present invention includes: a substrate comprising a plurality of metal magnetic particles and a binding material for binding the plurality of metal magnetic particles, and having a first surface extending along a coil axis and a second surface opposite the first surface; a first external electrode disposed on the substrate; a second external electrode disposed on the substrate; and a coil conductor electrically connected to the first external electrode and the second external electrode, extending around the coil axis. In one embodiment, the coil conductor has a winding portion formed by alternating a plurality of first conductor portions and a smaller number of second conductor portions than the first conductor portions, wherein the distance between the first conductor portion and the first surface is smaller than the distance between the second conductor portion and the second surface.

[0016] In one embodiment of the present invention, at least a portion of the first conductor is exposed from the first surface of the base.

[0017] In one embodiment of the present invention, a portion of the first conductor portion that is exposed from the base is covered with an insulating film.

[0018] In one embodiment of the present invention, the coil conductor includes the second conductor portion, the number of which is one less than that of the first conductor portion.

[0019] In one embodiment of the present invention, the coil component is an inductor used in a DC / DC converter.

[0020] One embodiment of the present invention relates to a DC / DC converter including the above-mentioned inductor.

[0021] A circuit board according to one embodiment of the present invention includes: the coil component described above; and a mounting substrate joined to the first external electrode and the second external electrode by solder.

[0022] An electronic device according to one embodiment of the present invention includes the above-mentioned circuit board.

[0023] Effects of the Invention

[0024] According to the embodiment of the present invention, it is possible to prevent the moisture from concentrating on a certain path when the moisture moves from the inside to the surface of the magnetic base. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a perspective view schematically showing a coil component according to one embodiment of the present invention.

[0026] Figure 2 yes Figure 1 Schematic plan view of a coil component.

[0027] Figure 3 It is a perspective view schematically showing a coil component according to another embodiment of the present invention.

[0028] Figure 4 yes Figure 3 Schematic plan view of a coil component.

[0029] Figure 5 It is a perspective view schematically showing a coil component according to another embodiment of the present invention.

[0030] Figure 6 It is schematically represented Figure 5 Exploded perspective view of the coil components.

[0031] Figure 7 yes Figure 5 Schematic plan view of a coil component.

[0032] Figure 8 It is a plan view schematically showing a coil component according to another embodiment of the present invention.

[0033] Description of Reference Numerals

[0034] 1, 101, 201 coil component, 10, 110, 210 magnetic base, 21, 22, 121, 122, 221, 222 external electrodes, 25, 125, 225 coil conductor, 25Aa1-25Aa4, 125Aa1-125Aa4, 225Aa1-225Aa4 first conductor portion, 25Ab1-25Ab3, 125Ab1-125Ab3, 225Ab1-225Ab3 second conductor portion, 40 insulating layer, Ax coil axis. DETAILED DESCRIPTION

[0035] Various embodiments of the present invention will be described below with reference to the accompanying drawings. Identical components in multiple drawings are denoted by the same reference numerals across the multiple drawings. It should be noted that for ease of illustration, the drawings are not necessarily drawn to scale.

[0036] Reference Figure 1 and Figure 2 A coil component 1 according to one embodiment of the present invention will be described. Figure 1 is a perspective view schematically showing the coil component 1, Figure 2 This is a schematic plan view of coil component 1. As shown, coil component 1 includes: a magnetic base 10; a coil conductor 25 disposed within magnetic base 10; an external electrode 21 disposed on the surface of magnetic base 10; and an external electrode 22 disposed on the surface of magnetic base 10 at a distance from external electrode 21.

[0037] In this specification, unless otherwise indicated by the context, the “length” direction, “width” direction, and “thickness” direction of the coil component 1 are respectively Figure 1 The "L-axis", "W-axis" and "T-axis" directions in the image are shown in Figure 2. The "thickness" direction is sometimes also called the "height" direction.

[0038] The coil component 1 is mounted on the mounting substrate 2a. The circuit board 2 includes the coil component 1 and the mounting substrate 2a on which the coil component 1 is mounted. Two pad portions 3 are provided on the mounting substrate 2a. The coil component 1 is mounted on the mounting substrate 2a by bonding the external electrodes 21 and 22 to the corresponding pad portions 3 of the mounting substrate 2a. The circuit board 2 can be mounted in various electronic devices. Electronic devices that can be equipped with the circuit board 2 include smart phones, tablet computers, game consoles, electrical components of automobiles, and various other electronic devices.

[0039] Coil component 1 can be used in inductors, transformers, filters, reactors, and various other coil components. Coil component 1 can also be used in coupled inductors, choke coils, and various other magnetically coupled coil components. For example, coil component 1 can be an inductor used in a DC / DC converter. The uses of coil component 1 are not limited to those described in this specification.

[0040] The magnetic substrate 10 is made of a magnetic material and has a generally rectangular parallelepiped shape. The magnetic substrate 10 of one embodiment of the present invention has a length (dimension in the L-axis direction) of 1.6 mm to 4.5 mm, a width (dimension in the W-axis direction) of 0.8 mm to 3.2 mm, and a height (dimension in the T-axis direction) of 0.8 mm to 5.0 mm. The dimensions of the magnetic substrate 10 are not limited to the dimensions specifically described in this specification. When referring to a "rectangular parallelepiped" or "rectangular parallelepiped shape" in this specification, this does not necessarily mean a "rectangular parallelepiped" in the strict mathematical sense.

[0041] The magnetic substrate 10 has a first principal surface 10a, a second principal 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 magnetic substrate 10 is defined by these six surfaces. The first principal surface 10a and the second principal surface 10b define the two end surfaces in the height direction, the first end surface 10c and the second end surface 10d define the two end surfaces in the length direction, and the first side surface 10e and the second side surface 10f define the two end surfaces in the width direction.

[0042] like Figure 1 As shown in FIG. 1 , the first principal surface 10a is located on the upper side of the magnetic base 10, and therefore, the first principal surface 10a is sometimes referred to as the "upper surface". Similarly, the second principal surface 10b is sometimes referred to as the "lower surface". The coil component 1 is configured such that the second principal surface 10b is opposite to the substrate 2, and therefore, the second principal surface 10b is sometimes referred to as the "mounting surface". When referring to the upper and lower directions of the coil component 1, the first principal surface 10a is referred to as the "upper surface". Figure 1 The up and down directions are used as the reference.

[0043] In one embodiment of the present invention, external electrodes 21 are provided on the mounting surface 10b and end surface 10c of the magnetic substrate 10. External electrodes 22 are provided on the mounting surface 10b and end surface 10d of the magnetic substrate 10. The shape and arrangement of the external electrodes 21 and 22 are not limited to the illustrated example. The external electrodes 21 and 22 are arranged with a gap in the longitudinal direction.

[0044] In one embodiment, the magnetic substrate 10 is composed of a composite magnetic material comprising a plurality of metal magnetic particles and a binding material. The metal magnetic particles may be a mixture of multiple metal magnetic particles having different average particle sizes. When the metal magnetic particles include large-diameter and small-diameter metal magnetic particles, the average particle size of the large-diameter metal magnetic particles is, for example, 10 μm, and the average particle size of the small-diameter metal magnetic particles is, for example, 1 μm. The binding material binds the plurality of metal magnetic particles together.

[0045] The metal magnetic particles are made of various soft magnetic materials. For example, the metal magnetic particles have Fe as the main component. 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-BC alloy and Fe-Si-Cr-B alloy, or (4) mixed particles obtained by mixing them. The composition of the metal magnetic particles contained in the magnetic matrix 10 is not limited to the above-mentioned composition. An insulating film made of glass, resin, or other materials with excellent insulating properties can be provided on the surface of each metal magnetic particle.

[0046] The bonding material is composed of, for example, a thermosetting resin with excellent insulating properties. The resin material used as the bonding material has a lower magnetic permeability than the magnetic material. Examples of the resin material used as the bonding material include epoxy resin, polyimide resin, polystyrene (PS) resin, high-density polyethylene (HDPE) resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinylidene fluoride (PVDF) resin, phenolic resin, polytetrafluoroethylene (PTFE) resin, and polybenzoxazole (PBO) resin.

[0047] The coil conductor 25 includes a winding portion 25A that is spirally wound around a coil axis Ax extending in the thickness direction (T-axis direction), and a lead conductor portion 25B that extends from both ends of the winding portion 25A to connect the two ends to the external electrodes 21 and 22, respectively. The lead conductor portion 25B includes a first lead conductor 25b1 that connects one end of the winding portion 25A to the external electrode 21, and a second lead conductor 25b2 that connects the other end of the winding portion 25A to the external electrode 22. In the illustrated embodiment, the coil axis Ax intersects the first principal surface 10a and the second principal 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.

[0048] In the winding portion 25A, a plurality of first conductor portions and a smaller number of second conductor portions than the plurality of first conductor portions are alternately connected. In the illustrated embodiment, the winding portion 25A has four first conductor portions 25Aa1 to 25Aa4 and three second conductor portions 25Ab1 to 25Ab3. The first conductor portions 25Aa1 to 25Aa4 are examples of first conductor portions included in the winding portion 25A, and the second conductor portions 25Ab1 to 25Ab3 are examples of second conductor portions included in the winding portion 25A. The number of first conductor portions included in the winding portion 25A is not limited to four. In one embodiment, the number of first conductor portions included in the winding portion 25A is in the range of 2 to 5. In one embodiment, the number of second conductor portions included in the winding portion 25A is one less than the number of first conductor portions. The number of second conductor portions included in the winding portion 25A is, for example, in the range of 1 to 4.

[0049] More specifically, the winding portion 25A includes: a first conductor portion 25Aa1 connected to the second lead conductor 25b2 and extending clockwise around the coil axis Ax from a connection point with the second lead conductor 25b2; a second conductor portion 25Ab1 extending clockwise around the coil axis Ax from the other end of the first conductor portion 25Aa1 opposite to the end connected to the second lead conductor 25b2; a first conductor portion 25Aa2 extending clockwise around the coil axis Ax from the other end of the second conductor portion 25Ab1 opposite to the end connected to the first conductor portion 25Aa1; and a second conductor portion 25Ab2 extending clockwise around the coil axis Ax from the other end of the first conductor portion 25Aa2 opposite to the end connected to the second conductor portion 25 The first conductor portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 are connected to the winding portion 25A. The winding portion 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 are connected to the winding portion 25A. The first conductor portions 25Aa1 to 25Aa4 extend generally along the first side surface 10e, and the second conductor portions 25Ab1 to 25Ab3 extend generally along the second side surface 10f. To determine the boundary between the first conductor portions 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3, a virtual plane VS1 passing through the coil axis Ax and extending parallel to the LT plane can be used as the boundary plane dividing the first conductor portions 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3.

[0050] Next, refer to Figure 2 The arrangement of the coil conductor 25 with respect to the magnetic base 10 will be described. Figure 2 This is a schematic plan view of the coil component 1 as viewed from the coil axis Ax direction. Figure 2 In FIG, a transmission image of the magnetic base 10 and the coil conductor 25 is shown from a viewpoint in the direction of the coil axis Ax. Figure 2For ease of explanation, the external electrodes 21 and 22 are omitted from the illustration. As described above, both ends of the substantially elliptical winding portion 25A are connected to the lead conductor portion 25B. Within the winding portion 25A, four first conductor portions 25Aa1 to 25Aa4 and three second conductor portions 25Ab1 to 25Ab3 are alternately connected. The coil conductor 25 is constructed and arranged so that the distance D1 between the first conductor portion and the first side surface 10e is smaller than the distance D2 between the second conductor portion and the second side surface 10f.

[0051] In one embodiment, the ratio of D1 to D2, i.e., D1 / D2, is set to less than 1. This ensures that moisture on the side with more first conductors can easily migrate from the interior to the surface of the magnetic base 10. In other words, by reducing the distance between the first conductors, which act as resistance to moisture migration due to the presence of more conductors, and the surface of the magnetic base 10, the resistance to moisture migration can be reduced.

[0052] In one embodiment, the smaller the number of first conductor sections, the smaller D1 / D2. For example, the number of conductors in the first conductor section may be directly proportional or substantially directly proportional to D1 / D2. More specifically, D1 / D2 may be in the range of 0.5 to 1 (0.5 ≤ D1 / D2 < 1) depending on the number of first conductor sections. In the illustrated embodiment, the number of first conductor sections is 4 and the number of second conductor sections is 3. Therefore, D1 / D2 may be in the range of 0.75 to 1 (0.75 ≤ D1 / D2 < 1). When the number of first conductor sections is 2 and the number of second conductor sections is 1, D1 / D2 may be in the range of 0.5 to 1 (0.5 ≤ D1 / D2 < 1). When the number of first conductor sections is 3 and the number of second conductor sections is 2, D1 / D2 may be in the range of 0.67 to 1 (0.67 ≤ D1 / D2 < 1). When the number of first conductors is 5 and the number of second conductors is 4, D1 / D2 can be set to a value between 0.8 and 1 (0.8 ≤ D1 / D2 < 1). By setting D1 / D2 within the above range in accordance with the number of first and second conductors, moisture can easily migrate from the interior of the magnetic base 10 to the first side surface 10e. This makes the ease of moisture migration from the interior to the surface of the magnetic base 10 uniform. When the magnetic base 10 is mounted using reflow soldering or other methods, the heat applied to the magnetic base 10 causes the volume of moisture remaining in the magnetic base 10 to expand, causing stress to act on the magnetic base 10. By facilitating the migration of moisture from the interior to the surface of the magnetic base 10, the stress acting on the magnetic base 10 can be alleviated. Consequently, the occurrence of microcracks in the magnetic base 10 can be suppressed. Furthermore, by setting D1 / D2 to be greater than 0.8 and less than 1, the inductance and magnetic saturation characteristics can be maintained. For example, when D1 / D2 is 0.8, the rate of change in inductance can be kept within -5% compared to when D1 / D2 is 1. By setting D1 / D2 to less than 1, even if the inductance or magnetic saturation characteristics degrade, the rate of decrease can be suppressed. Furthermore, the generation of microcracks in the magnetic substrate 10 can be suppressed, preventing reliability degradation. This is particularly important in high-reliability applications such as automotive applications.

[0053] When the distances between the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e are equal, the distance between any of the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e can be defined as the distance D1 between the first conductor portion and the first side surface 10e. When the distances between the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e are different, the distance D1 between the first conductor portion and the first side surface 10e can be defined as the shortest distance between the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e, or as the average of the distances between the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e. The distance between each of the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e can be the shortest distance between the two. The distance D2 between the second conductor portion and the second side surface 10f can also be defined similarly to the distance D1. That is, when the distances between the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f are equal, the distance between any of the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f may be defined as the distance D2 between the second conductor portion and the second side surface 10f. When the distances between the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f are different, the distance D2 between the second conductor portion and the second side surface 10f may be defined as the shortest distance between the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f, or the distance D2 between the second conductor portion and the second side surface 10f may be defined as the average of the distances between the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f. The distance between each of the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f may be defined as the shortest distance between the two distances.

[0054] The shape of the winding portion 25A in a plan view may be an ellipse, an oval, a circle, a rectangle, a polygon other than a rectangle, or various shapes other than these.

[0055] Figure 8 Modifications of the coil component 1 are shown. Figure 8 FIG is a plan view of a coil component 1 according to another embodiment of the present invention. Figure 8In the coil component 1 shown, the first conductor portions 25Aa1 to 25Aa4 of the winding portion 25A of the coil conductor 25 are exposed from the first side surface 10e of the magnetic base 10. As shown in the figure, at least a portion of the first conductor portions 25Aa1 to 25Aa4 may be exposed from the first side surface 10e of the magnetic base 10. When at least a portion of the first conductor portions 25Aa1 to 25Aa4 is exposed from the first side surface 10e of the magnetic base 10, the distance D1 between the first conductor portion of the coil conductor and the first side surface 10e can be considered to be zero. In addition, in order to prevent undesired current flow, the exposed portions of the first conductor portions 25Aa1 to 25Aa4 from the magnetic base 10 may be covered with an insulating film 40. The insulating film 40 may be made of resin, glass, or other insulating materials with excellent insulation properties.

[0056] Next, an example of a method for manufacturing a coil component 1 according to an embodiment of the present invention will be described. An example of a method for manufacturing a coil component 1 using a compression molding process will be described below. First, metal magnetic particles are prepared. An insulating film can be provided on the surface of the metal magnetic particles as needed. As described above, the metal magnetic particles can be mixed particles obtained by mixing multiple types of particles having different average particle sizes. Next, the prepared metal magnetic particles, a resin material, and a diluent solvent are mixed to produce a composite magnetic material. The composite magnetic material is placed in a forming mold containing a pre-prepared coil conductor 25, and a forming pressure is applied at a temperature of, for example, 50°C to 150°C, and then heated to 150°C to 400°C for curing, thereby obtaining a magnetic substrate 10 containing the coil conductor 25. The coil conductor 25 is arranged in the forming mold in such a manner that, when viewed from the direction of the coil axis Ax, the distance D1 between the first conductor portion of the coil conductor 25 and the first side surface 10e of the magnetic substrate 10 is less than the distance D2 between the second conductor portion of the coil conductor 25 and the second side surface 10f.

[0057] The heat treatment for obtaining the magnetic base 10 may be performed in two stages as described above, or in one stage. In the case of performing the heat treatment in one stage, forming and curing are performed during the heat treatment. In the magnetic base 10, the resin contained in the composite magnetic material is cured to become a binding material. The magnetic base 10 may be formed at a temperature of, for example, about 80°C. The forming pressure is, for example, 50 MPa to 200 MPa. The forming pressure may be appropriately adjusted to obtain the desired filling rate. The forming pressure is, for example, 100 MPa.

[0058] Next, a conductive paste is applied to the surface of the magnetic substrate 10 obtained as described above to form external electrodes 21 and 22. External electrode 21 is electrically connected to one end of a coil conductor 25 disposed within the magnetic substrate 10, and external electrode 22 is electrically connected to the other end of the coil conductor 25 disposed within the magnetic substrate 10. Through the above steps, coil component 1 is obtained.

[0059] The manufactured coil component 1 can be mounted on the substrate 2 through a reflow process. In this case, the substrate 2 with the coil component 1 is passed through a reflow furnace heated to a peak temperature of, for example, 260°C at high speed. The external electrodes 21 and 22 are then bonded to the pads 3 of the substrate 2 by solder. As a result, the coil component 1 is mounted on the mounting substrate 2a, and the circuit board 2 is manufactured.

[0060] Next, refer to Figure 3 and Figure 4 A coil component 101 according to another embodiment of the present invention will be described. Coil component 101 is a planar coil. As shown in the figure, coil component 101 includes: a magnetic base 110; an insulating plate 150 disposed within magnetic base 110; a coil conductor 125 disposed on the upper and lower surfaces of insulating plate 150 within magnetic base 110; an external electrode 121 disposed on magnetic base 110; and an external electrode 122 disposed on magnetic base 110 at a distance from external electrode 121. Like magnetic base 10, magnetic base 110 is formed of a magnetic material. Insulating plate 150 is a plate-shaped component formed of insulating material.

[0061] The magnetic substrate 110 has a roughly rectangular parallelepiped shape. It has a first principal surface 110a, a second principal 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 principal surface 110a and the second principal surface 110b define the two end surfaces in the height direction, the first end surface 110c and the second end surface 110d define the two end surfaces in the length direction, and the first side surface 110e and the second side surface 110f define the two end surfaces in the width direction. The description of the magnetic substrate 10 also applies to the magnetic substrate 110 to the greatest extent possible.

[0062] The coil conductor 125 includes a winding portion 125A spirally wound around a coil axis Ax extending in the thickness direction (T-axis direction), and lead conductor portions 125B extending from both ends of the winding portion 125A to connect them to the external electrodes 121 and 122, respectively. The lead conductor portion 125B includes a first lead conductor 125b1 connecting one end of the winding portion 125A to the external electrode 121, and a second lead conductor 125b2 connecting the other end of the winding portion 125A to the external electrode 122.

[0063] Similar to the winding portion 25A, the winding portion 125A includes a plurality of first conductor portions and a smaller number of second conductor portions than the plurality of first conductor portions. The description regarding the coil conductor 25 also applies to the coil conductor 125 as much as possible. In the illustrated embodiment, the winding portion 125A includes four first conductor portions 125Aa1 to 125Aa4 and three second conductor portions 125Ab1 to 125Ab3. The first conductor portions 125Aa1 to 125Aa4 are examples of first conductor portions included in the winding portion 125A, and the second conductor portions 125Ab1 to 125Ab3 are examples of second conductor portions included in the winding portion 125A. In one embodiment, the number of first conductor portions included in the winding portion 125A is in the range of 2 to 5. In one embodiment, the number of second conductor portions included in the winding portion 125A is one less than the number of first conductor portions. The number of second conductor portions included in the winding portion 125A is, for example, in the range of 1 to 4.

[0064] More specifically, the winding portion 125A includes: a first conductor portion 125Aa1 connected to the second lead conductor 125b2 and extending clockwise around the coil axis Ax from the connection point with the second lead conductor 125b2; a second conductor portion 125Ab1 extending clockwise around the coil axis Ax from the other end of the first conductor portion 125Aa1 opposite to the end connected to the second lead conductor 125b2; a first conductor portion 125Aa2 extending clockwise around the coil axis Ax from the other end of the second conductor portion 125Ab1 opposite to the end connected to the first conductor portion 125Aa1; and a second conductor portion 125Ab2 extending clockwise around the coil axis Ax from the other end of the first conductor portion 125Aa2 opposite to the end connected to the second conductor portion 125Aa1. The first conductor portion 125Aa4 extends clockwise from the other end of the second conductor portion 125Ab3, opposite to the end connected to the first conductor portion 125Aa3, around the coil axis Ax. The first conductor portion 125Aa4 extends clockwise from the other end of the second conductor portion 125Ab3, opposite to the end connected to the first conductor portion 125Aa3, around the coil axis Ax to a connection point with the first lead conductor 125b1. The first conductor portion 125Aa4 penetrates the insulating plate 150 along the T-axis direction and extends along the back surface (the negative side of the T-axis direction) of the insulating plate 150 to the first lead conductor 125b1. In this manner, in the winding portion 125A, the first conductor portions 125Aa1 to 125Aa4 and the second conductor portions 125Ab1 to 125Ab3 are alternately connected. The first conductor portions 125Aa1 to 125Aa4 extend generally along the first side surface 110e, and the second conductor portions 125Ab1 to 125Ab3 extend generally along the second side surface 110f. To determine the boundary between the first conductor portions 125Aa1 to 125Aa4 and the second conductor portions 125Ab1 to 125Ab3, a virtual plane VS1, which passes through the coil axis Ax and extends parallel to the LT plane, can be used as the boundary plane separating the first conductor portions 125Aa1 to 125Aa4 and the second conductor portions 125Ab1 to 125Ab3.

[0065] Next, refer to Figure 4 The arrangement of the coil conductor 125 with respect to the magnetic base 110 will be described. Figure 4 This is a schematic plan view of the coil component 101 as viewed from the coil axis Ax direction. Figure 4 In FIG, a transmission image of the magnetic base 110 and the coil conductor 125 is shown from a viewpoint in the direction of the coil axis Ax. Figure 4For ease of explanation, the external electrodes 121 and 122 are omitted from the illustration. As described above, both ends of the roughly elliptical winding portion 125A are connected to the lead conductor portion 125B. Within the winding portion 125A, four first conductor portions 125Aa1 to 125Aa4 and three second conductor portions 125Ab1 to 125Ab3 are alternately connected. The coil conductor 125 is constructed and arranged so that the distance D1 between the first conductor portion and the first side surface 110e is smaller than the distance D2 between the second conductor portion and the second side surface 110f. At least a portion of the first conductor portion 125Aa1 of the coil conductor 125 may be exposed from the first side surface 110e of the magnetic substrate 110. The portion of the first conductor portion 125Aa1 exposed from the magnetic substrate 110 may be covered by a magnetic layer. This magnetic layer may be constructed in the same manner as the magnetic layer 40.

[0066] Next, an example of a method for manufacturing coil component 101 is described. First, a plate-shaped insulating plate made of a magnetic material is prepared. Next, a photoresist is applied to the upper and lower surfaces of the insulating plate. Then, a conductor pattern is exposed and transferred to the upper and lower surfaces of the insulating plate, followed by a development process. Consequently, a resist having an opening pattern for forming coil conductor 125 is formed on each of the upper and lower surfaces of the insulating plate 150.

[0067] Next, each of the opening patterns is filled with a conductive metal through plating. The resist is then removed from the insulating plate 150 by etching, forming coil conductors 125 on the upper and lower surfaces of the insulating plate. Furthermore, by filling the through-holes provided in the insulating plate 150 with a conductive metal, through-holes are formed to connect the front and back sides of the insulating plate with the coil conductors 125.

[0068] Next, a magnetic base 110 is formed on both sides of the insulating plate 150 on which the coil conductor 125 is formed. In order to form the magnetic base 110, a magnetic sheet is first produced. In order to produce the magnetic sheet, metal magnetic particles are first prepared. An insulating film can be provided on the surface of the metal magnetic particles as needed. As described above, the metal magnetic particles can be mixed particles obtained by mixing a plurality of particles having different average particle sizes. Next, the prepared metal magnetic particles, resin material and diluent are kneaded to produce a slurry. The metal magnetic particles are dispersed in the slurry. Next, the slurry is applied in the form of a sheet on a substrate such as a PET film, and the applied slurry is dried to evaporate the diluent. Thus, a magnetic sheet in which metal magnetic particles are dispersed in the resin is produced. Two magnetic sheets are prepared, the coil conductor is arranged between the two magnetic sheets, and a laminate is produced while being heated and pressurized. The method for producing the laminate is not limited to this. In another method for producing a laminate, an insulating plate 150 having a coil conductor 125 is placed in a molding die, a slurry obtained by mixing metal magnetic particles and a resin material is placed in the molding die, and the laminate is produced by heating and pressurizing. The laminate can be formed at a temperature of 50°C to 150°C, for example, about 80°C. The molding pressure is, for example, 50MPa to 200MPa. In order to obtain the desired filling rate, the molding pressure can be adjusted appropriately. The molding pressure is, for example, 100MPa. Then, the laminate is heated at the curing temperature of the resin (for example, 150°C to 400°C). Thus, a magnetic substrate 110 having a coil conductor 125 inside is obtained. External electrodes 121 and 122 are provided at specified positions on the outer surface of the magnetic substrate 110 to produce the coil component 101.

[0069] Next, refer to Figures 5 to 7 A coil component 201 according to another embodiment of the present invention will now be described. Coil component 201 is a laminated coil. As shown, coil component 201 includes: a magnetic base 210; a coil conductor 225 disposed within magnetic base 210; an external electrode 221 disposed on magnetic base 210; and an external electrode 222 disposed on magnetic base 210 at a distance from external electrode 221. A set of external electrodes is provided on magnetic base 210. Like magnetic base 10, magnetic base 210 is made of a magnetic material.

[0070] The magnetic base 210 is formed into a rectangular parallelepiped shape from a magnetic material. It includes a magnetic layer 220 in which a coil 225 can be embedded; an upper cover layer 218 made of a magnetic material disposed on the upper surface of the magnetic layer 220; and a lower cover layer 219 made of a magnetic material disposed 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 base 10, the boundaries between the magnetic layer 220 and the upper cover layer 218, as well as the boundaries between the magnetic layer 220 and the lower cover layer 219, may not be clearly identified. The magnetic substrate 210 has a roughly rectangular parallelepiped shape and includes a first principal surface 210a, a second principal 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 principal surface 210a and the second principal surface 210b define the two end surfaces in the height direction, the first end surface 210c and the second end surface 210d define the two end surfaces in the length direction, and the first side surface 210e and the second side surface 210f define the two end surfaces in the width direction. The description of the magnetic substrate 10 also applies to the magnetic substrate 210 to the greatest extent possible.

[0071] The magnetic layer 220 includes magnetic films 211 to 214. Within the magnetic layer 220, the magnetic films 211, 212, 213, and 214 are stacked in this order, from the positive side to the negative side in the T-axis direction. Conductor patterns C11 to C14 are formed on the top surfaces of each of the magnetic films 211 to 214. Conductor patterns C11 to C14 can be formed, for example, by screen printing a conductive paste made of a highly conductive metal or alloy. Materials for this conductive paste include Ag, Pd, Cu, Al, or alloys thereof.

[0072] Through-holes V1 to V3 are formed at predetermined locations on the magnetic films 211 to 213. These through-holes V1 to V3 can be formed by forming through-holes that penetrate the magnetic films 211 to 213 along the T-axis at predetermined locations and embedding a conductive material in these through-holes. Conductor patterns C11 to C14 are electrically connected to adjacent conductor patterns via the through-holes V1 to V3. These connected conductor patterns C11 to C14 form a spiral coil conductor 225.

[0073] like Figure 7As shown, the coil conductor 225 includes a winding portion 225A that is spirally wound around a coil axis Ax extending in the thickness direction (T-axis direction), and lead conductor portions 225B that extend from both ends of the winding portion 225A to connect them to the external electrodes 221 and 222, respectively. The lead conductor portion 225B includes a first lead conductor 225b1 that connects one end of the winding portion 225A to the external electrode 221, and a second lead conductor 225b2 that connects the other end of the winding portion 225A to the external electrode 222.

[0074] Similar to the winding portion 25A, the winding portion 225A includes a plurality of first conductor portions and a smaller number of second conductor portions than the plurality of first conductor portions. The description regarding the coil conductor 25 also applies to the coil conductor 225 as much as possible. In the illustrated embodiment, the winding portion 225A includes four first conductor portions 225Aa1 to 225Aa4 and three second conductor portions 225Ab1 to 225Ab3. The first conductor portions 225Aa1 to 225Aa4 are examples of first conductor portions included in the winding portion 225A, and the second conductor portions 225Ab1 to 225Ab3 are examples of second conductor portions included in the winding portion 225A. In one embodiment, the number of first conductor portions included in the winding portion 225A is in the range of 2 to 5. In one embodiment, the number of second conductor portions included in the winding portion 225A is one less than the number of first conductor portions. The number of second conductor portions included in the winding portion 225A is, for example, in the range of 1 to 4.

[0075] More specifically, the winding portion 225A includes: a first conductor portion 225Aa1 connected to the second lead conductor 225b2 and extending clockwise around the coil axis Ax from the connection point with the second lead conductor 225b2; a second conductor portion 225Ab1 extending clockwise around the coil axis Ax from the other end of the first conductor portion 225Aa1 opposite to the end connected to the second lead conductor 225b2; a first conductor portion 225Aa2 extending clockwise around the coil axis Ax from the other end of the second conductor portion 225Ab1 opposite to the end connected to the first conductor portion 225Aa1; and a second conductor portion 225Ab2 extending clockwise around the coil axis Ax from the other end of the first conductor portion 225Aa2 opposite to the end connected to the second conductor portion 225Aa1. The first conductor portion 225Aa1 to 225Aa4 extends clockwise around the coil axis Ax from the other end opposite to the end connected to the first conductor portion 225Aa2 of the second conductor portion 225Ab2. The second conductor portion 225Ab3 extends clockwise around the coil axis Ax from the other end opposite to the end connected to the second conductor portion 225Ab2 of the first conductor portion 225Aa3. The first conductor portion 225Aa1 to 225Aa4 extends clockwise around the coil axis Ax from the other end opposite to the end connected to the first conductor portion 225Aa3 to the connection point with the first lead conductor 225b1. The first conductor portions 225Aa1 to 225Aa4 extend generally along the first side surface 210e, and the second conductor portions 225Ab1 to 225Ab3 extend generally along the second side surface 210f. When it is necessary to determine the boundary between the first conductor portions 225Aa1 to 225Aa4 and the second conductor portions 225Ab1 to 225Ab3, a virtual plane VS1 passing through the coil axis Ax and extending parallel to the LT plane can be used as the boundary plane dividing the first conductor portions 225Aa1 to 225Aa4 and the second conductor portions 225Ab1 to 225Ab3.

[0076] Next, refer to Figure 7 The arrangement of the coil conductor 225 with respect to the magnetic base 210 will be described. Figure 7 This is a schematic plan view of the coil component 201 as viewed from the coil axis Ax direction. Figure 7 In FIG, a transmission image of the magnetic base 210 and the coil conductor 225 is shown from a viewpoint in the direction of the coil axis Ax. Figure 7For ease of explanation, the external electrodes 221 and 222 are omitted from the illustration. As described above, both ends of the roughly elliptical winding portion 225A are connected to the lead conductor portion 225B. Within the winding portion 225A, four first conductor portions 225Aa1 to 225Aa4 and three second conductor portions 225Ab1 to 225Ab3 are alternately connected. The coil conductor 225 is constructed and arranged so that the distance D1 between the first conductor portion and the first side surface 210e is smaller than the distance D2 between the second conductor portion and the second side surface 210f. At least a portion of the first conductor portions 225Aa1 to 225Aa4 of the coil conductor 225 may be exposed from the first side surface 210e of the magnetic substrate 210. The portions of the first conductor portions 225Aa1 to 225Aa4 exposed from the magnetic substrate 210 may be covered with a magnetic layer. This magnetic layer may be constructed in the same manner as the magnetic layer 40.

[0077] 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. Next, an example of a method for manufacturing the coil component 201 by a lamination process will be described.

[0078] First, magnetic sheets are prepared to form the magnetic films 18a-18d that constitute the upper cover layer 218, the magnetic films 11-14 that constitute the magnetic layer 220, and the magnetic films 19a-19d that constitute the lower cover layer 219. These magnetic sheets are formed from a composite magnetic material containing a binder and metal magnetic particles. The magnetic sheets for coil component 201 can be prepared using the same method as the magnetic sheets used in the manufacturing process of coil component 1.

[0079] Next, coil conductors are placed on the magnetic sheets. Specifically, through-holes are formed at predetermined locations on each of the magnetic sheets, which will become magnetic films 11 through 13, extending along the T-axis. Next, conductive paste is screen-printed on the top surfaces of each of the magnetic sheets, which will become magnetic films 11 through 14, to form an unfired conductor pattern on the magnetic sheets. Furthermore, conductive paste is embedded in each of the through-holes formed in the magnetic sheets.

[0080] Next, the magnetic sheets that will become magnetic films 11 to 14 are stacked to form a coil laminate. Each magnetic sheet that will become magnetic films 11 to 14 is stacked so that the unfired conductor patterns C11 to C14 formed on each magnetic sheet can be electrically connected to adjacent conductor patterns via unfired through-holes V1 to Va3.

[0081] Next, a plurality of magnetic sheets are stacked to form an upper stacked body serving as the upper cover layer 18. Separately, a plurality of magnetic sheets are stacked to form a lower stacked body serving as the lower cover layer 19.

[0082] Next, the lower laminate, coil laminate, and upper laminate are stacked sequentially from the negative side to the positive side in the T-axis direction, and the stacked laminates are heat-pressed using a press to form the main laminate. The main laminate can also be formed by not forming the lower laminate, coil laminate, and upper laminate, but by stacking all the prepared magnetic sheets sequentially and heat-pressing the stacked magnetic sheets together.

[0083] Next, the main body laminate is cut into individual pieces of the desired size using a cutting machine such as a dicing machine or laser processing machine, thereby obtaining a sliced ​​laminate. The sliced ​​laminate is then degreased and heat-treated. If necessary, the ends of the sliced ​​laminate are subjected to a grinding process such as barrel grinding.

[0084] Next, conductive paste is applied to both ends of the sliced ​​laminate to form external electrodes 221 and external electrodes 222. Through the above steps, coil component 201 is obtained.

[0085] Next, the effects achieved by the above-described embodiment will be described. In the coil component 1 according to one embodiment of the present invention, the winding portion 25A of the coil conductor 25 is constructed by alternately connecting first conductor portions 25Aa1 to 25Aa4 and second conductor portions 25Ab1 to 25Ab3. Moisture cannot pass through the coil conductor 25, and therefore, the first conductor portions 25Aa1 to 25Aa4 and the second conductor portions 25Ab1 to 25Ab3 act as resistance or obstacles to the movement of moisture. The number of first conductor portions 25Aa1 to 25Aa4 is greater than the number of second conductor portions 25Ab1 to 25Ab3. Therefore, when moisture escapes from the interior of the winding portion 25A of the coil conductor 25 in the magnetic substrate 10 to the exterior of the magnetic substrate 10, the moisture is less likely to move toward the first side surface 10e facing the first conductor portions 25Aa1 to 25Aa4, but is more likely to move toward the second side surface 10f facing the second conductor portions 25Ab1 to 25Ab3. When moisture migrating from the interior of the magnetic base 10 to the surface is concentrated in a portion of the path within the magnetic base 10, the pressure in that portion of the path tends to increase, resulting in microcracks being more likely to form around that portion of the path in the magnetic base 10. According to the above-described embodiment, the distance D1 between the first conductor portions 25Aa1 to 25Aa4 and the first side surface 10e of the magnetic base 10 is smaller than the distance D2 between the second conductor portions 25Ab1 to 25Ab3 and the second side surface 10f of the magnetic base 10. Therefore, from the perspective of the migration distance, the path from the core portion to the first side surface 10e has less resistance to moisture migration than the path from the inner region of the winding portion (core portion) to the second side surface 10f. On the other hand, as described above, the number of conductors in the first conductor sections 25Aa1-25Aa4 is greater than the number of conductors in the second conductor sections 25Ab1-25Ab3. Therefore, from the perspective of the number or amount of conductors that hinder moisture movement, the path from the core to the first side surface 10e presents greater resistance to moisture movement than the path from the inner region of the winding (core) to the second side surface 10f. With the above-described embodiment, the resistance to moisture movement caused by the distance the moisture travels is balanced by the resistance to moisture movement caused by the number of conductors present along the path. As a result, moisture moving from the core of the magnetic substrate to the surface is not concentrated in either the path from the core to the first surface or the path from the core to the second surface, but is dispersed and moved along both paths. This can thus suppress the formation of microcracks caused by moisture concentrating along a specific path. The above-described effects also apply to coil components 101 and 201.

[0086] In the above embodiment, at least a portion of the coil conductor 25, 125, 225 may be exposed from the magnetic base 10, 110, 210. According to this embodiment, moisture inside the magnetic base 10, 110, 210 more easily moves toward the first side surface 10e, 110e, 210e.

[0087] The dimensions, materials, and configurations of the various components described in the various embodiments are not limited to those explicitly described in the various embodiments, and the various components may be modified to have any dimensions, materials, and configurations within the scope of the present invention. Furthermore, components not explicitly described in this specification may be added to the various embodiments described above, and some of the components described in the various embodiments may be omitted.

Claims

1. A coil component, characterized in that: include: a substrate comprising a plurality of metal magnetic particles and a bonding material bonding the plurality of metal magnetic particles together, and having a first surface extending along the coil axis and a second surface opposite to the first surface; a first external electrode provided on at least a mounting surface of the surface of the substrate; a second external electrode provided on at least the mounting surface of the surface of the base body and provided at a position spaced apart from the first external electrode; and a coil conductor electrically connected to the first external electrode and the second external electrode, extending around the coil axis, The coil conductor includes a winding portion formed by alternately connecting a plurality of first conductor portions and a second conductor portion, the number of which is smaller than that of the first conductor portions. The distance between the first conductor portion and the first surface is smaller than the distance between the second conductor portion and the second surface.

2. The coil component according to claim 1, wherein: At least a portion of the first conductor is exposed from the first surface of the base.

3. The coil component according to claim 2, wherein: A portion of the first conductor portion that is exposed from the base is covered with an insulating film.

4. The coil component according to any one of claims 1 to 3, characterized in that: The coil conductor includes the second conductor portion, the number of which is one less than that of the first conductor portion.

5. A DC / DC converter, characterized in that: The invention comprises the coil component according to any one of claims 1 to 4.

6. A circuit board, characterized in that: include: The coil component according to any one of claims 1 to 4; and A mounting substrate is bonded to the first external electrode and the second external electrode by solder.

7. An electronic device, characterized in that: Including the circuit board according to claim 6.

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