Composite inductor

Abstract

The present invention provides a composite inductor capable of improving insulation between two coils.　A composite inductor 10 according to the present invention comprises: an element body 12 formed by stacking magnetic body layers S composed of first metal magnetic particles; a first coil 20 disposed inside the element body 12 and formed by connecting a plurality of conductors; and a second coil 22 formed by connecting a plurality of conductors and disposed coaxially with the first coil 20 with a gap therebetween. A first magnetic body part 14a composed of second metal magnetic particles is disposed between the first coil 20 and the second coil 22. The average particle diameter of the second metal magnetic particles is smaller than that of the first metal magnetic particles. The resin filling rate of the first magnetic body part 14a is higher than the resin filling rates of the magnetic body layers S.

Description

Composite inductor

[0001] The present invention relates to a composite inductor.

[0002] In a composite inductor, it is necessary to reduce the distance between two coils as much as possible to increase negative correlation, that is, to increase the coupling coefficient to a certain extent. On the other hand, reducing the distance between coils tends to lower insulation between the coils and reduce IR.

[0003] Against this backdrop, where there is demand for designs that achieve both a suitable coupling coefficient and IR, conventional composite inductors have been developed to ensure insulation by reducing the particle size of the magnetic layer between coils. On top of that, impregnating the entire magnetic layer of the element body with epoxy resin is intended to secure element body strength and prevent penetration of moisture and chemical solutions.

[0004] Japanese Patent Application Laid-Open No. 2022-000922, Japanese Patent Application Laid-Open No. 2021-057482

[0005] The composite inductor disclosed in Patent Document 1 is a composite inductor in which two coils are connected vertically with a non-magnetic layer interposed therebetween. The composite inductor disclosed in Patent Document 2 describes an insulating layer made of small-diameter metal magnetic particles, but does not mention the space between the first and second coils or between each conductor. It also describes that the content of epoxy resin in the inner circumference of the coil is low.

[0006] However, for a composite inductor, while it is necessary to reduce the distance between two coils as much as possible to increase negative correlation to a certain extent, that is, to increase the negative coupling coefficient to a certain extent, reducing the distance between coils tends to lower insulation between the coils and reduce IR.

[0007] Therefore, a primary object of the present invention is to provide a composite inductor that can improve insulation between two coils.

[0008] The composite inductor according to this invention includes a base body formed by laminating magnetic layers made of first metallic magnetic particles, a first coil disposed inside the base body and configured by connecting a plurality of conductors, and a second coil configured by connecting a plurality of conductors and arranged coaxially with the first coil at intervals, wherein a first magnetic portion made of second metallic magnetic particles is disposed between the first coil and the second coil, the average particle size of the second metallic magnetic particles is smaller than the average particle size of the first metallic magnetic particles, and the resin filling rate of the first magnetic portion is higher than the resin filling rate of the magnetic layer.

[0009] In the composite inductor according to this invention, the average particle size of the second metallic magnetic particles constituting the first magnetic material portion is small, as is the average particle size of the first metallic magnetic particles constituting the magnetic material layer, and the resin filling rate of the first magnetic material portion is higher than that of the magnetic material layer. As a result, the insulation between the first coil and the second coil can be improved.

[0010] This invention provides a composite inductor that can improve the insulation between two coils.

[0011] The above-mentioned objectives, other objectives, features, and advantages of this invention will become even clearer from the following description of embodiments for carrying out the invention, with reference to the drawings.

[0012] This is a schematic external perspective view showing a composite inductor according to an embodiment of the present invention. This is a transparent perspective view of the composite inductor shown in Figure 1. This is a transparent end view of the composite inductor shown in Figure 1. This is an exploded perspective view of the components comprising the composite inductor according to an embodiment of the present invention. This is a flow diagram of the manufacturing method of the composite inductor according to an embodiment of the present invention.

[0013] The composite inductor of this disclosure will be described below. However, this disclosure is not limited to the configuration described below and may be modified as appropriate without departing from the gist of this disclosure. Furthermore, a combination of several of the individual preferred configurations described below also constitutes this disclosure.

[0014] The composite inductor 10 according to the present invention is used, for example, as a choke coil in a DC-DC converter. The composite inductor 10 according to the present invention is also applicable to applications other than DC-DC converters.

[0015] In this specification, terms indicating relationships between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements mean not only strictly defined aspects but also substantially equivalent ranges, such as ranges with differences of a few percent. In this specification, the direction in which the magnetic layer, magnetic part, and conductive part constituting the base body are stacked is referred to as the "stacking direction."

[0016] The drawings shown below are schematic representations, and their dimensions, aspect ratios, and scales may differ from those of the actual product.

[0017] A. Composite Inductors The composite inductors according to embodiments of the present invention will be described in detail below with reference to the drawings.

[0018] Figure 1 is a schematic external perspective view showing a composite inductor according to an embodiment of the present invention. Figure 2 is a through-view perspective view of the composite inductor shown in Figure 1. Figure 3 is a through-view end view of the composite inductor shown in Figure 1. Figure 4 is an exploded perspective view of the components of the composite inductor according to an embodiment of the present invention.

[0019] The composite inductor 10 shown in Figures 1 and 2 comprises a base body 12, a first coil 20, a second coil 22, an external electrode 30, and a through conductor 40. The external electrode 30 includes a first external electrode 30a, a second external electrode 30b, a third external electrode 30c, and a fourth external electrode 30d. The through conductor 40 includes a first through conductor 40a, a second through conductor 40b, a third through conductor 40c, and a fourth through conductor 40d. Each component will be described in detail below.

[0020] (a) The base body 12 is, for example, a rectangular prism shape having six faces or a roughly rectangular prism shape. The base body 12 may have rounded corners and edges. The corners are the parts where three faces of the base body 12 intersect, and the edges are the parts where two faces of the base body 12 intersect.

[0021] Figures 1 and 2 show the length direction z, width direction y, and height direction x of the composite inductor 10 and the base body 12. The length direction z, width direction y, and height direction x are orthogonal to each other. The mounting surface of the composite inductor 10 is, for example, a surface parallel to the length direction z and width direction y (LW surface).

[0022] The base body 12 shown in Figure 1 has a first main surface 12a and a second main surface 12b that are opposite to the height direction x, a first side surface 12c and a second side surface 12d that are perpendicular to the height direction x and opposite to the width direction y, and a first end surface 12e and a second end surface 12f that are perpendicular to the length direction z and opposite to the height direction x and width direction y. In the example shown in Figure 1, the second main surface 12b of the base body 12 corresponds to the bottom surface of the base body 12.

[0023] The base body 12 includes a magnetic layer S (see Figure 4). Preferably, the base body 12 has a laminated structure. Specifically, it is preferable that the base body 12 includes a plurality of magnetic layers S in the lamination direction (e.g., the height direction x). In this embodiment, as shown in Figure 4, it may be constructed by laminating magnetic layer groups G1 to G9, each containing at least one magnetic layer S. The boundaries between each layer of the laminated structure of the base body 12 may be absent. Furthermore, each magnetic layer group may be constructed by laminating multiple identical patterns.

[0024] The magnetic layer group G1 has a magnetic material layer S formed by stacking multiple identical patterns, and constitutes the first main surface 12a of the base body 12. The number of stacked layers in the magnetic layer group G1 may be one, but as an example, the number of stacked magnetic material layers S may be multiple.

[0025] The magnetic layer group G2 is provided with a first coil conductor portion 20a that constitutes a part of the first coil 20 with its central axis K in the magnetic layer S. Multiple layers of the first coil conductor portions 20a of the magnetic layer group G2 constitute one winding of the first coil 20 (90° × 3; that is, intended to be C-shaped or U-shaped in plan view), and the ends of the first coil conductor portions 20a are spaced apart from each other. One end of the first coil conductor portion 20a is electrically connected to the first through conductor 40a, which will be described later, and the other end of the first coil conductor portion 20a is electrically connected to the first conductor portion 50a (via conductor), which will be described later. In addition, the first coil conductor portion 20a has avoidance portions 20a1 to 20a3 in the parts where the second through conductor 40b, the third through conductor 40c, and the fourth through conductor 40d are located in a plan view from the height direction x.

[0026] Magnetic layer group G3 has a second magnetic portion 14b provided in the magnetic layer S. The second magnetic portion 14b is provided so as to face the first coil conductor portion 20a in the height direction x view, and constitutes a single winding, and its width is wider than each of the conductor patterns of the first coil conductor portion 20a and the first coil conductor portion 20b, so that the axial core portion 16 of magnetic layer group G3 is smaller than the axial core portion 16 of magnetic layer group G2. This ensures insulation between the first coil conductor portion 20a and the first coil conductor portion 20b. The second magnetic portion 14b is also provided with a first conductor portion 50a (via conductor) for connecting the first coil conductor portion 20a of magnetic layer group G2 and the first coil conductor portion 20b of magnetic layer group G4, and a first through conductor 40a for electrically connecting the first coil conductor portion 20a and the first external electrode 30a. The first through conductor 40a is positioned in the corner of the magnetic layer S, corresponding to the arrangement of the first external electrode 30a, which will be described later. In this specification, "corner" refers to the position of a corner in a closed region (for example, the corner of a rectangular region).

[0027] Magnetic layer group G4 is provided with a first coil conductor portion 20b that constitutes a part of the first coil 20 with its central axis K in the magnetic material layer S. Multiple layers of the first coil conductor portions 20b of magnetic layer group G4 constitute the other windings of the first coil 20 (90° × 4; that is, intended to be substantially enclosed in a plan view), and the ends of the first coil conductor portions 20b are spaced apart from each other. One end of the first coil conductor portion 20b is electrically connected to the first conductor portion 50a, and the other end of the first coil conductor portion 20b is directly connected to the second through conductor 40b, which will be described later. The other end of the first coil conductor 20b is positioned in the corner of the magnetic material layer S, corresponding to the arrangement of the second external electrode 30b, which will be described later. Furthermore, the first coil conductor portion 20b has avoidance portions 20b1 to 20b3 in the portion where the first through conductor 40a, the third through conductor 40c, and the fourth through conductor 40d are located when viewed from a plan view from the height direction x.

[0028] In magnetic layer group G5, a first magnetic material portion 14a is provided on the entire surface of the magnetic material layer S except for the axial core portion 16. A first through conductor 40a for electrically connecting the first coil conductor portion 20a and the first external electrode 30a, and a second through conductor 40b for electrically connecting the first coil conductor portion 20b and the second external electrode 30b are provided at the corners. The first magnetic material portion 14a is positioned between the first coil 20 and the second coil 22, and the axial core portion 16 of magnetic layer group G5 is the same size as the axial core portion 16 of magnetic layer group G4. This ensures insulation between the first coil 20 and the second coil 22.

[0029] The magnetic layer group G6 is provided with a second coil conductor portion 22a that constitutes a part of the second coil 22 with its central axis K in the magnetic layer S. Multiple layers of the second coil conductor portions 22a of the magnetic layer group G6 constitute one winding (90° × 4) of the second coil 22, and the ends of the second coil conductor portions 22a are spaced apart from each other. One end of the second coil conductor portion 22a is electrically connected to a third through conductor 40c, which will be described later, and the other end of the second coil conductor portion 22a is electrically connected to a second conductor portion 50b (via conductor), which will be described later. Furthermore, the second coil conductor portion 22a has avoidance portions 22a1 to 22a3 in the parts where the first through conductor 40a, the second through conductor 40b, and the fourth through conductor 40d are located when viewed from a plan view from the height direction x.

[0030] Magnetic layer group G7 has a third magnetic portion 14c provided in the magnetic material layer S. The third magnetic portion 14c is positioned to face the second coil conductor portion 22a in the height direction x view, and forms a single winding, with each width being wider than the respective conductor patterns of the second coil conductor portion 22a and the second coil conductor portion 22b. The axial core portion 16 of magnetic layer group G7 is smaller than the axial core portion 16 of magnetic layer group G6. This ensures insulation between the second coil conductor portion 22a and the second coil conductor portion 22b. Furthermore, the third magnetic material portion 14c is provided with a second conductor portion 50b (via conductor) for connecting the second coil conductor portion 22a of magnetic layer group G6 and the second coil conductor portion 22b of magnetic layer group G8, and a third through conductor 40c for electrically connecting the second coil conductor portion 22a and the third external electrode 30c. Outside the third magnetic material portion 14c, there is a first through conductor 40a for electrical connection with the first external electrode 30a and a second through conductor 40b for electrical connection with the second external electrode 30b. The first through conductor 40a, the second through conductor 40b, and the third through conductor 40c are each located in the corners of the magnetic material layer S, corresponding to the arrangement of the first external electrode 30a, the second external electrode 30b, and the third external electrode 30c. The second conductor portion 50b, which is directly connected to the second coil conductor portion 22a, is positioned adjacent to the third through conductor 40c.

[0031] The magnetic layer group G8 is provided with a second coil conductor portion 22b that forms part of the second coil 22, which has a central axis K, on ​​the magnetic layer S. Multiple layers of the second coil conductor portion 22b of the magnetic layer group G8 constitute other windings of the second coil 22 (larger than 90° × 3 and smaller than 90° × 4), and the ends of the second coil conductor portion 22b are spaced apart from each other. One end of the second coil conductor portion 22b is electrically connected to the second conductor portion 50b, and the other end of the second coil conductor portion 22b is directly connected to the fourth through conductor 40d, which will be described later. The other end of the second coil conductor portion 22b is located in the corner of the magnetic layer S, corresponding to the arrangement of the fourth external electrode 30d, which will be described later. Furthermore, the second coil conductor portion 22b has avoidance portions 22a1 to 22a3 in the area where the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c are located when viewed from a plan view from the height direction x.

[0032] The magnetic layer group G9 is provided with a first through conductor 40a, a second through conductor 40b, a third through conductor 40c, and a fourth through conductor 40d at its corners. Specifically, at the corners of the magnetic layer S, the first through conductor 40a, the second through conductor 30b, the third through conductor 30c, and the fourth through conductor 40d are provided at positions corresponding to the first external electrode 30a, the second external electrode 30b, the third external electrode 30c, and the fourth external electrode 30d.

[0033] The thickness of magnetic layer group G1 and magnetic layer group G9 is preferably 100 μm or more. In particular, by increasing the thickness of magnetic layer group G9, it is possible to secure the DC superimposed current of the composite inductor 10.

[0034] The thickness of magnetic layer groups G2, G4, G6, and G8 is preferably 80 μm or more and 250 μm or less. By ensuring the conductive portions of the first coil 20 and the second coil 22, the DC resistance can be reduced.

[0035] The thickness of the magnetic layer group G5 is preferably 20 μm or more and 60 μm or less. This allows for a larger coupling coefficient while ensuring insulation between the first coil 20 and the second coil 22.

[0036] The thickness of magnetic layer group G3 and magnetic layer group G7 is preferably 10 μm or more and 20 μm or less. This allows for a large inductance value while ensuring insulation between the first coil 20 and the second coil.

[0037] The first magnetic body portion 14a, the second magnetic body portion 14b, the third magnetic body portion 14c, and the magnetic body layer S each contain metallic magnetic particles made of a soft magnetic material and a resin. The magnetic body layer S consists of the first metallic magnetic particles. The first magnetic body portion 14a consists of the second metallic magnetic particles. The second magnetic body portion 14b consists of the third metallic magnetic particles. The third magnetic body portion 14c consists of the fourth metallic magnetic particles. Each metallic magnetic particle may be a particle of a metallic magnetic material such as Fe, Co, Ni, or an alloy containing at least one of these (metallic magnetic particles) or a ferrite particle. The metallic magnetic particles are preferably Fe particles or Fe alloy particles. Examples of Fe alloys include Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, etc. As the resin, thermosetting resins such as epoxy resins, silicon resins, polyimide resins, and phenolic resins, and thermoplastic resins such as polyethylene resins and polyamide resins are used.

[0038] The average particle size of the first metal magnetic particles is preferably 1 μm or more and 30 μm or less, more preferably 1 μm or more and 20 μm or less, and even more preferably 1 μm or more and 10 μm or less. Furthermore, the average particle sizes of the second, third, and fourth metal magnetic particles are preferably smaller than the average particle size of the first metal magnetic particles, and are preferably 0.2 μm or more and 5 μm or less. Note that the average particle sizes of the second, third, and fourth metal magnetic particles may be different from each other. The average particle sizes of the second, third, and fourth metal magnetic particles are preferably 0.2 times or more and 0.5 times or less than that of the first metal magnetic particles.

[0039] The average particle size of each metallic magnetic particle can be measured by the procedure described below. A sample of the composite inductor 10 is cut parallel to the height direction x passing through the center of the main body, and multiple regions (e.g., 5 regions) (e.g., 130 μm × 100 μm) of the resulting cross-section are photographed with a SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the equivalent circular diameter of the metallic magnetic particles. The average value of the obtained equivalent circular diameters is taken as the average particle size of the metallic magnetic particles.

[0040] The surface of the metallic magnetic particles made of the above-mentioned metallic magnetic material is preferably covered with an insulating film. Covering the surface of the metallic magnetic particles with an insulating film improves the insulation between the metallic magnetic particles. Methods for forming the insulating film on the surface of the metallic magnetic particles include the sol-gel method and the mechanochemical method. The material constituting the insulating film is preferably an oxide such as P or Si. Alternatively, the insulating film may be an oxide film formed by the oxidation of the surface of the metallic magnetic particles. The thickness of the insulating film is preferably 1 nm to 50 nm, more preferably 1 nm to 30 nm, and even more preferably 1 nm to 20 nm. For example, a cross-section obtained by polishing a sample of the composite inductor 10 can be photographed with a scanning transmission electron microscope (STEM), and the thickness of the insulating film covering the surface of the metallic magnetic particles can be measured from the obtained STEM image.

[0041] Furthermore, heat treatment is applied when forming the base body 12. In this case, the metallic magnetic particles contained in the base body 12 have an oxide film on their surface. This oxide film originates from the metallic magnetic particles and is formed by the heat treatment. In the base body 12, adjacent metallic magnetic particles may be joined to each other via the oxide film.

[0042] The resin filling rate of the first magnetic material portion 14a is higher than that of the magnetic material layer S. In this case, it is preferable that the resin filling rate of the first magnetic material portion 14a is 70% or more. Also, it is preferable that the resin filling rate of the magnetic material layer S is 30% or more and less than 70%. This makes it possible to improve the insulation between the first coil 20 and the second coil 22 by the first magnetic material portion 14a.

[0043] Furthermore, it is preferable that the resin filling rate of each of the second magnetic body portion 14b and the third magnetic body portion 14c is higher than the resin filling rate of the magnetic layer S. In this case, it is preferable that the resin filling rate of each of the second magnetic body portion 14b and the third magnetic body portion 14c is 70% or higher. This improves the insulation between the first coil conductor portion 20a and the first coil conductor portion 20b of the first coil 20 provided by the second magnetic body portion 14b. Furthermore, this improves the insulation between the second coil conductor portion 22a and the second coil conductor portion 22b of the second coil 22 provided by the third magnetic body portion 14c.

[0044] The resin filling rate can be measured as follows. That is, for example, a cross section along the height direction x and the length direction z at the center of the element body 12 in the width direction y is exposed, the area of the metal magnetic particles and the resin area are binarized into respective areas, and the resin filling rate can be calculated from (area of the resin area) / (area of the cross section).

[0045] The first coil 20 and the second coil 22 are disposed inside the element body 12. A first magnetic body portion 14a is disposed between the first coil 20 and the second coil 22. It is preferable that the first coil 20 and the second coil 22 are magnetically negatively coupled. For example, the coupling coefficient between the first coil 20 and the second coil 22 is 0.1 or more and 0.8 or less. Note that inside the element body 12, two coils including only the first coil 20 and the second coil 22 may be provided, or a plurality of first coils 20 and second coils 22 magnetically coupled to each other may be provided.

[0046] (b) First Coil The first coil 20 is provided at a position farther from the bottom surface (second main surface 12b) of the element body 12 than the second coil 22 is.

[0047] The first coil 20 includes a first coil conductor portion 20a and a first coil conductor portion 20b in the height direction x. Adjacent first coil conductor portions 20a and first coil conductor portions 20b are connected via the first conductor portion 50a (via conductor).

[0048] It is preferable that the first coil conductor portions 20a and 20b have the same thickness and width, respectively, but they may be different.

[0049] As an example of the material thereof, the first coil conductor portions 20a and 20b may be metal conductors such as Ag, Cu and / or Pd. Further, for the material of the first coil conductor portions 20a and 20b, the same type of material as that of the second coil conductor portions 22a and 22b may be used, or different types of materials may be used. The first coil conductor portions 20a and 20b may be formed, for example, by printing a conductor paste.

[0050] As shown in FIG. 4, the first coil conductor portion 20a includes avoiding portions 20a1 to 20a3 respectively arranged inside the second through conductor 40b, the third through conductor 40c, and the fourth through conductor 40d in a plan view from the height direction x.

[0051] As shown in FIG. 4, the first coil conductor portion 20b includes avoiding portions 20b1 to 20b3 respectively arranged inside the first through conductor 40a, the third through conductor 40c, and the fourth through conductor 40d in a plan view from the height direction x. By providing the avoiding portion 20b1, a wiring can be appropriately drawn out from the first coil 20 toward the external electrode 30 so as not to interfere with the first through conductor 40a.

[0052] (c) Second coil The second coil 22 is spaced apart from the first coil 20 on the same central axis K (coaxial). The second coil 22 includes a second coil conductor portion 22a and a second coil conductor portion 22b in the height direction x. The adjacent second coil conductor portion 22a and second coil conductor portion 22b are connected via a second conductor portion 50b (via conductor).

[0053] It is preferable that the second coil conductor portions 22a and 22b have the same thickness and width, respectively, but they may be different.

[0054] As an example of the material thereof, the second coil conductor portions 22a and 22b may be metal conductors such as Ag, Cu and / or Pd. The second coil conductor portions 22a and 22b may be formed, for example, by printing a conductor paste.

[0055] As shown in Figure 4, the second coil conductor portion 22a has avoidance portions 22a1 to 22a3 that are positioned inside the first through conductor 40a, the second through conductor 40b, and the fourth through conductor 40d, respectively, when viewed from a plan view from the height direction x. By providing the avoidance portions 22a1 to 22a3, the wiring of the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c can be appropriately drawn out from the second coil conductor portion 22a toward the external electrode 30 without interfering with the second coil conductor portion 22a.

[0056] The second coil conductor portion 22b has avoidance portions 22b1 to 22b3 that are positioned inside the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c, respectively, when viewed from a plan view from the height direction x. By providing the avoidance portions 22b1 to 22b3, the wiring of the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c can be appropriately drawn out from the second coil conductor portion 22b toward the external electrode 30 so as not to interfere with the second coil conductor portion 22b.

[0057] (d) External electrodes The external electrodes 30 include a first external electrode 30a, a second external electrode 30b, a third external electrode 30c, and a fourth external electrode 30d. The first external electrode 30a and the second external electrode 30b are provided on the bottom surface (second main surface 12b) of the base body 12 and are electrically connected to the first coil 20. The third external electrode 30c and the fourth external electrode 30d are provided on the bottom surface (second main surface 12b) of the base body 12 and are electrically connected to the second coil 22. In the composite inductor 10, the bottom surface (second main surface 12b) of the base body 12 can be used as the mounting surface. That is, mounting of the composite inductor 10 on the bottom surface becomes possible.

[0058] The first external electrode 30a acts as an input electrode to the first coil 20. The first external electrode 30a may be provided only on the second main surface 12b of the base body 12, or it may be provided spanning the second main surface 12b and at least one of the first side surface 12c and the first end surface 12e of the base body 12.

[0059] The second external electrode 30b acts as an output electrode for the first coil 20. The second external electrode 30b may be provided only on the second main surface 12b of the base body 12, or it may be provided spanning the second main surface 12b and at least one of the first side surface 12c and the second end surface 12f of the base body 12.

[0060] The third external electrode 30c acts as an input electrode to the second coil 22. The third external electrode 30c may be provided only on the second main surface 12b of the base body 12, or it may be provided spanning the second main surface 12b and at least one of the second side surface 12d and the second end surface 12f of the base body 12.

[0061] The fourth external electrode 30d acts as an output electrode for the second coil 22. The fourth external electrode 30d may be provided only on the second main surface 12b of the base body 12, or it may be provided spanning the second main surface 12b and at least one of the second side surface 12d and the first end surface 12e of the base body 12.

[0062] The first external electrode 30a, the second external electrode 30b, the third external electrode 30c, and the fourth external electrode 30d may each be composed of a conductive material such as Ag, Cu, and / or Pd as an underlying electrode layer. More preferably, a plating layer of one or more materials selected from the group consisting of Ni, Sn, Cu, and Au may be provided on the surface of these underlying electrode layers. By providing a plating layer of the above materials, the device can be properly mounted on a mounting substrate.

[0063] The thickness of the first external electrode 30a, the second external electrode 30b, the third external electrode 30c, and the fourth external electrode 30d is preferably 5 μm or more and 100 μm or less, and may be, for example, 10 μm or more and 50 μm or less.

[0064] The thickness of the external electrode 30 is determined by polishing the sample and then imaging the external electrode 30 portion with an SEM. In the resulting SEM image, the thickness of the external electrode 30 is measured at one point approximately in the center and defined as the thickness of the external electrode 30.

[0065] (e) Through conductor The through conductor 40 includes a first through conductor 40a, a second through conductor 40b, a third through conductor 40c, and a fourth through conductor 40d. The first through conductor 40a, the second through conductor 40b, the third through conductor 40c, and the fourth through conductor 40d are provided inside the base body 12.

[0066] The first through conductor 40a electrically connects one end of the first coil conductor portion 20a constituting the first coil 20 to the first external electrode 30a. The first through conductor 40a extends along the height direction x. The first through conductor 40a may have a laminated structure.

[0067] The second through conductor 40b electrically connects the other end of the first coil conductor portion 20b, which constitutes the first coil 20, to the second external electrode 30b. The second through conductor 40b extends along the height direction x. The second through conductor 40b may have a laminated structure.

[0068] The third through conductor 40c electrically connects one end of the second coil conductor portion 22a, which constitutes the second coil 22, to the third external electrode 30c. The third through conductor 40c extends along the height direction x. The third through conductor 40c may have a laminated structure.

[0069] The fourth through conductor 40d electrically connects the other end of the second coil conductor portion 22b, which constitutes the second coil 22, to the fourth external electrode 30d. The fourth through conductor 40d extends along the height direction x. The fourth through conductor 40d may have a laminated structure.

[0070] Here, a preferred arrangement of the first through conductor 40a to the fourth through conductor 40d is arranged along one side that constitutes the outer edge of the base body 12.

[0071] Furthermore, the lengths of the through conductors 40 in the stacking direction are such that the length of the first through conductor 40a is longer than the length of the second through conductor 40b, the length of the second through conductor 40b is longer than the length of the third through conductor 40c, and the length of the third through conductor 40c is longer than the length of the fourth through conductor 40d. Because the lengths of each through conductor 40 are in this relationship, the first coil 20, which is located further from the bottom surface (second main surface 12b) of the base body 12 than the second coil 22 in the height direction x, can be appropriately electrically connected to the external electrode 30.

[0072] Furthermore, in a preferred embodiment relating to the through conductor 40, the first through conductor 40a may be directly connected to the lower coil conductor of the first coil conductor portion 20a, the second through conductor 40b may be directly connected to the lower coil conductor of the first coil conductor portion 20b, the third through conductor 40c may be directly connected to the lower coil conductor of the second coil conductor portion 22a, and the fourth through conductor 40d may be directly connected to the lower coil conductor of the second coil conductor portion 22b. By directly connecting the through conductors 40 to each coil in this way, the size of the composite inductor 10 is reduced.

[0073] According to the composite inductor 10 shown in Figure 1, the average particle size of the metallic magnetic particles in the first magnetic material portion 14a is small, as is the average particle size of the metallic magnetic particles in the magnetic material layer S, and the resin filling rate of the first magnetic material portion 14a is higher than that of the magnetic material layer S. Therefore, the insulation between the first coil 20 and the second coil 22 can be improved by such a first magnetic material portion 14a.

[0074] B. Method for Manufacturing a Composite Inductor Next, the method for manufacturing a composite inductor according to the present invention will be described. Figure 5 is a flowchart of the method for manufacturing a composite inductor according to an embodiment of this invention.

[0075] The composite inductor 10 according to the present invention can be obtained by laminating a magnetic paste for forming a magnetic material and a conductive paste for forming a coil and a through conductor, and then heat-treating the laminated material.

[0076] In detail, the composite inductor 10 can be manufactured as follows.

[0077] A magnetic paste containing metallic magnetic particles is prepared as the magnetic paste. The metallic magnetic particles are mixed with a binder such as cellulose or polyvinyl butyral and a mixture of solvents such as terpineol or butyl diglycol acetate, and kneaded to obtain the magnetic paste.

[0078] A first magnetic paste containing first metallic magnetic particles is prepared as the magnetic paste for the magnetic layer S; a second magnetic paste containing second metallic magnetic particles is prepared as the magnetic paste for the first magnetic part 14a; a third magnetic paste containing third metallic magnetic particles is prepared as the magnetic paste for the second magnetic part 14b; and a fourth magnetic paste containing fourth metallic magnetic particles is prepared as the magnetic paste for the third magnetic part 14c.

[0079] For example, prepare a silver paste as a conductive paste. A conductive paste is obtained by mixing conductive powder with a predetermined amount of solvent, resin, dispersant, etc.

[0080] (a) Printing and lamination process (Step 1) Next, a laminate is created using each of the pastes described above.

[0081] A substrate is prepared by stacking a heat-release sheet and a polyethylene terephthalate (PET) film on a metal plate, and a magnetic paste is screen-printed onto it a predetermined number of times to form a first magnetic paste layer. The resulting magnetic paste layer becomes magnetic layer group G1.

[0082] Next, a first magnetic paste layer is formed on the magnetic layer group G1, excluding the area that will become the first coil conductor portion 20a. Furthermore, a conductive paste layer is formed in the area that will become the first coil conductor portion 20a, thereby forming magnetic layer group G2.

[0083] Next, a third magnetic paste layer is formed on the magnetic layer group G2 at the location that will become the second magnetic material portion 14b. Furthermore, a first magnetic paste layer is formed in the region where the third magnetic paste layer is not formed, excluding the locations that will become the first conductor portion 50a (via conductor) and the first through conductor 40a. Then, a conductor paste layer is formed at the locations that will become the first conductor portion 50a (via conductor) and the first through conductor 40a, thereby forming the magnetic layer group G3.

[0084] Next, a first magnetic paste layer is formed on the magnetic layer group G3 in the region excluding the areas that will become the first coil conductor portion 20b and the first through conductor 40a. Furthermore, a conductor paste layer is formed in the areas that will become the first coil conductor portion 20b and the first through conductor 40a, thereby forming magnetic layer group G4.

[0085] Next, a second magnetic paste layer is formed on the magnetic layer group G4 in the region excluding the area that will become the first through conductor 40a, the area that will become the second through conductor 40b, and the area that will become the magnetic material layer S (axis core portion 16). Furthermore, a first magnetic paste layer is formed in the area that will become the magnetic material layer S (axis core portion 16). Then, a conductor paste layer is formed in the area that will become the first through conductor 40a and the area that will become the second through conductor 40b, thereby forming the magnetic layer group G5.

[0086] Next, a first magnetic paste layer is formed on the magnetic layer group G5 in the region excluding the areas that will become the second coil conductor portion 22a, the first through conductor 40a, and the second through conductor 40b. Furthermore, a conductive paste layer is formed in the area that will become the second coil conductor portion 22a. Then, conductive paste layers are formed in the areas that will become the first through conductor 40a and the second through conductor 40b, thereby forming magnetic layer group G6.

[0087] Next, a third magnetic paste layer is formed on the magnetic layer group G6 at the location that will become the third magnetic material portion 14c. Furthermore, in the region where the third magnetic paste layer is not formed, a conductor paste layer is formed at the location that will become the second conductor portion 50b (via conductor), the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c. Then, by forming a conductor paste layer at the location that will become the second conductor portion 50b (via conductor), the first through conductor 40a, the second through conductor 40b, and the third through conductor 40c, the magnetic layer group G7 is formed.

[0088] Next, a third magnetic paste layer is formed on the magnetic layer group G7 in the area excluding the portion that will become the second coil conductor portion 22b, the portion that will become the first through conductor 40a, the portion that will become the second through conductor 40b, and the portion that will become the third through conductor 40c. Furthermore, a conductive paste layer is formed in the portion that will become the second coil conductor portion 22b, the portion that will become the first through conductor 40a, the portion that will become the second through conductor 40b, and the portion that will become the third through conductor 40c, thereby forming the magnetic layer group G8.

[0089] Next, a first magnetic paste layer is formed on the magnetic layer group G8 in the area excluding the areas that will become the first through conductor 40a, the second through conductor 40b, the third through conductor 40c, and the fourth through conductor 40d. Conductor paste layers are then formed in the areas that will become the first through conductor 40a, the second through conductor 40b, the third through conductor 40c, and the fourth through conductor 40d, thereby forming the magnetic layer group G9. This process of forming the magnetic layer group G9 is repeated a predetermined number of times.

[0090] Finally, the PET film is removed from the metal plate to create a laminated block. In the above process, the magnetic layer group G1 was laminated in the order of magnetic layer group G9, but the order may be reversed.

[0091] The resulting laminated block is subjected to a pressurizing treatment, such as a warm hydrostatic press (WIP) treatment.

[0092] (b) Firing process (Step 2) Next, the pressurized laminated block is degreased and placed in a firing furnace for firing. The firing temperature is preferably 600°C to 800°C, more preferably 650°C to 750°C. The firing time is preferably 30 minutes to 90 minutes, more preferably 40 minutes to 80 minutes. The firing is preferably carried out in the atmosphere.

[0093] (c) Resin impregnation (Step 3) The laminated block after firing is impregnated with resin. Preferably, epoxy resin or silicone resin is used as the resin.

[0094] (d) Resin curing (Step 4) After the resin impregnation treatment described above, for example, in the case of epoxy resin, a heat treatment is performed at 100°C to 200°C to cure the resin. At this time, the resin filling rate of each magnetic material layer according to the present invention is controlled, for example, by adjusting the temperature rise and the residence time for each temperature. The softened resin can be moved from the side of the metal magnetic particles with large average particle size and large voids to the side of the metal magnetic particles with small average particle size by adjusting the temperature rise and the residence time for each temperature. That is, the temperature rise rate and the residence time for each temperature are controlled so that the resin filling rate of the first magnetic material part 14a, the second magnetic material part 14b and the third magnetic material part 14c is 70% or more, and the resin filling rate of the magnetic material layer S is less than 70%.

[0095] (e) Dicing (Step 5) Next, the laminated block is cut into individual pieces or arrays using a dicer or the like.

[0096] (f) Formation of external electrodes (Step 6) Next, the base electrode layer that constitutes the external electrode is formed. Then, electroless plating is performed to cover the base electrode layer, forming a plating layer on the base electrode layer.

[0097] The composite inductor 10 is manufactured as described above.

[0098] As described above, embodiments of the present invention are disclosed in the above description, but the present invention is not limited thereto. That is, without departing from the scope of the technical idea and objectives of the present invention, various modifications can be made to the embodiments described above in terms of mechanism, shape, material, quantity, position or arrangement, etc., and these are included in the present invention.

[0099] 10 Composite Inductor 12 Main Body 12a First Main Surface 12b Second Main Surface 12c First Side Surface 12d Second Side Surface 12e First End Surface 12f Second End Surface 14a First Magnetic Material Part 14b Second Magnetic Material Part 14c Third Magnetic Material Part 16 Axis Core Part 20 First Coil 20a, 20b First Coil Conductor Parts 20a1, 20a2, 20a3, 20b1, 20b2, 20b3 Avoidance Parts 22 Second Coil 22a, 22b Second Coil Conductor Parts 22a1, 22a2, 22a3, 22b1, 22b2, 22b3 Avoidance Parts 30 External Electrode 30a First External Electrode 30b Second External Electrode 30c Third External Electrode 30d Fourth external electrode 40 Through conductor 40a First through conductor 40b Second through conductor 40c Third through conductor 40d Fourth through conductor 50a First conductor part 50b Second conductor part S Magnetic layer K Central axis x Height direction y Width direction z Length direction

Claims

1. A composite inductor comprising: a base body formed by laminating magnetic layers made of first metallic magnetic particles; a first coil disposed inside the base body and configured by connecting a plurality of conductors; and a second coil configured by connecting a plurality of conductors and arranged coaxially with the first coil at intervals, wherein a first magnetic portion made of second metallic magnetic particles is disposed between the first coil and the second coil, the average particle size of the second metallic magnetic particles is smaller than that of the first metallic magnetic particles, and the resin filling rate of the first magnetic portion is higher than that of the magnetic layer.

2. The composite inductor according to claim 1, wherein the average particle size of the third metallic magnetic particles of the second magnetic material portion disposed between the conductors constituting the first coil and / or the second coil is smaller than the average particle size of the first metallic magnetic particles of the magnetic material layer, and the resin filling rate of the second magnetic material portion disposed between the conductors constituting the first coil and / or the second coil is higher than the resin filling rate of the magnetic material layer.

3. The composite inductor according to claim 2, wherein the average particle size of the second metallic magnetic particles in the first magnetic material portion and the average particle size of the third metallic magnetic particles in the second magnetic material portion are 0.2 times or more and 0.5 times or less than the first metallic magnetic particles in the magnetic material layer.

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