Method for manufacturing composite inductor, and composite inductor

Abstract

Provided are a method for manufacturing a composite inductor with which inductance characteristics are improved, and a composite inductor. A method for manufacturing a composite inductor 1 according to the present disclosure comprises: a step for laminating a magnetic material and an electroconductive material, and manufacturing, according to a first heat treatment condition, a first coil element 10 and a second coil element 20 provided with a magnetic body, a coil that is provided inside the magnetic body, and an external electrode that is electrically connected to the coil and is exposed from at least one mounting surface of the magnetic body; a step for manufacturing an intervening element according to a second heat treatment condition different from the first heat treatment condition by using a magnetic material having the same constituent material element as the aforementioned magnetic material; and a step for impregnating each of the first coil element 10, the second coil element 20, and the intervening element 30 with resin and then interposing the intervening element 30 between the first coil element 10 and the second coil element 20 to integrate these elements together.

Description

Method for manufacturing a composite inductor and composite inductor

[0001] The present disclosure relates to a method for manufacturing a composite inductor and a composite inductor.

[0002] Patent Document 1 (particularly, paragraphs

[0099] to

[0100] ) discloses a magnetically coupled coil component including a main laminate obtained by stacking a lower second laminate, a lower coil laminate, a lower first laminate, an upper second laminate, an upper coil laminate, and an upper first laminate in this order from the negative side to the positive side in the T-axis direction, and thermocompression-bonding the stacked laminates using a press. Patent Document 1 further discloses that, without forming the lower second laminate, the lower coil laminate, the lower first laminate, the upper second laminate, the upper coil laminate, and the upper first laminate, all of the prepared green sheets may be stacked in order, and the stacked green sheets may be thermocompression-bonded together to obtain a main laminate, which may then be singulated and heat-treated.

[0003] JP 2019-114582 A

[0004] In Patent Document 1, the laminates (upper first laminate, upper second laminate, lower first laminate, and lower second laminate) do not have conductor patterns, while the coil laminates (upper coil laminate and lower coil laminate) have conductor patterns. Therefore, the inventors of the present application have found that the optimal heat treatment conditions are different between a laminate without conductor patterns and a coil laminate with conductor patterns.

[0005] For example, when manufacturing a composite inductor including a first coil element and a second coil element, it is preferable to heat-treat the first coil element and the structure including the first coil element under heat-treating conditions that result in a suitable magnetic permeability. Furthermore, it is preferable to heat-treat the intervening element between the first coil element and the second coil element under heat-treating conditions that improve insulation or that result in a suitable coupling coefficient between the first coil element and the second coil element. Note that the term "composite inductor" as used herein refers to an inductor that includes two or more coil elements.

[0006] In view of the above, an object of the present disclosure is to provide a method for manufacturing a composite inductor with improved inductance characteristics, and a composite inductor.

[0007] The method for manufacturing a composite inductor according to the present disclosure includes the steps of: laminating a magnetic material and a conductive material to manufacture, under first heat treatment conditions, a first coil element and a second coil element, each of which comprises a magnetic body, a coil disposed inside the magnetic body, and an external electrode electrically connected to the coil portion and exposed from at least one mounting surface of the magnetic body; manufacturing an intervening element under second heat treatment conditions different from the first heat treatment conditions, using a magnetic material having the same constituent material elements as the magnetic material; and impregnating each of the first coil element, the second coil element, and the intervening element with resin, and then interposing the intervening element between the first coil element and the second coil element to integrate the elements together.

[0008] The composite inductor according to the present disclosure comprises: a first coil element including a first magnetic body, a first coil provided inside the first magnetic body, and a pair of first external electrodes electrically connected to the first coil and exposed from at least one mounting surface of the first magnetic body; a second coil element including a second magnetic body, a second coil provided inside the second magnetic body, and a second external electrode electrically connected to the second coil and exposed from at least one mounting surface of the second magnetic body; and an intervening element interposed between the first coil element and the second coil element, wherein the magnetic permeability of the first magnetic body and the second magnetic body is higher than the magnetic permeability of the intervening element.

[0009] According to the composite inductor manufacturing method and the composite inductor of the present disclosure, it is possible to improve the inductance characteristics.

[0010] FIG. 1 is a perspective view of a composite inductor according to a first embodiment. FIG. 2 is a perspective view of a modified example of the composite inductor according to the first embodiment. FIG. 3 is a perspective view of a composite inductor according to a second embodiment. FIG. 4A is a schematic cross-sectional view showing one aspect of the vicinity of the interface between a first coil element and an intervening element in a composite inductor according to the present disclosure. FIG. 4B is a schematic cross-sectional view showing another aspect of the vicinity of the interface between the first coil element and an intervening element in a composite inductor according to the present disclosure. FIG. 5 is a flow chart showing a manufacturing flow of the composite inductor according to the present disclosure. FIG. 6 is an exploded perspective view of the first coil element according to the present disclosure. FIG. 7 is a perspective view showing a state in which an intervening element is interposed between the first coil element and the second coil element.

[0011] The composite inductor of the present disclosure will be described below. Note that the present disclosure is not limited to the following configurations and may be modified as appropriate without departing from the spirit of the present disclosure. In addition, a combination of multiple individual preferred configurations described below also constitutes the present disclosure.

[0012] The composite inductor of the present disclosure is used, for example, in a multiphase DC-DC converter, and is particularly suitable for mounting between boards or for being built into a board. The composite inductor of the present disclosure can also be used for purposes other than DC-DC converters.

[0013] In this specification, terms indicating the relationship between elements (e.g., "parallel," "orthogonal," etc.) and terms indicating the shape of elements do not only mean the strict literal form, but also mean a range of substantial equivalence, for example, a range including a difference of about a few percent. Note that in this specification, the direction in which the magnetic layers and coil conductors that make up the element body are stacked is referred to as the "stacking direction."

[0014] The drawings shown below are schematic diagrams, and the dimensions, aspect ratio, scale, etc. may differ from those of the actual product.

[0015] <Description of the Composite Inductor> First, the composite inductor of the present disclosure will be described with reference to Figures 1 to 4B. Note that the shapes and arrangements of the composite inductor and its components are not limited to the examples shown in the drawings.

[0016] The composite inductor 1 shown in FIG. 1 includes a first coil element 10, a second coil element 20, and an intervening element 30.

[0017] 1 , the composite inductor 1 has, for example, a rectangular parallelepiped or approximately rectangular parallelepiped shape having six sides. The corners and ridges of the composite inductor 1 may be rounded. The corners are the portions where three sides of the composite inductor 1 intersect, and the ridges are the portions where two sides of the composite inductor 1 intersect.

[0018] 1, the length direction, width direction, and height direction of the composite inductor 1 are respectively indicated as direction L, direction W, and direction T. The length direction L, width direction W, and height direction T are perpendicular to each other.

[0019] The composite inductor 1 shown in FIG. 1 has a first main surface 1a and a second main surface 1b that face in the height direction T, a first end surface 1c and a second end surface 1d that are orthogonal to the height direction T and face in the length direction L, and a first side surface 1e and a second side surface 1f that face in the width direction W that is orthogonal to the length direction L and the height direction T. In the example shown in FIG. 1 , the first main surface 1a and the second main surface 1b of the composite inductor 1 correspond to mounting surfaces. More specifically, the mounting surface of the first coil element 10 and the mounting surface of the second coil element 20, which will be described later, may be positioned on opposite sides of each other. More specifically, the mounting surface of the first coil element 10 and the mounting surface of the second coil element 20 may be positioned on extensions of the winding axes of the first coil 12 of the first coil element 10 and the second coil 22 of the second coil element 20. The composite inductor 1 of the present disclosure may have two mounting surfaces (a first main surface 1 a and a second main surface 1 b), and each mounting surface may be mounted on a mounting substrate. By providing two mounting surfaces in this manner, it is possible to connect upper and lower substrates, or to connect conductor layers when the inductor is built into a multilayer substrate.

[0020] As shown in FIG. 2 , the external electrodes may extend from the first main surface 1 a (or the second main surface 1 b) to the first side surface 1 e and from the first main surface 1 a (or the second main surface 1 b) to the second side surface 1 f, thereby defining the mounting surfaces as the first side surface 1 e and the second side surface 1 f. Alternatively, as shown in FIG. 3 , the external electrodes may extend from the first main surface 1 a to the first end surface 1 c (or the second end surface 1 d) and from the second main surface 1 b to the first end surface 1 c (or the second end surface 1 d), thereby defining the mounting surfaces as the first end surface 1 c and the second end surface 1 d. In other words, the mounting surfaces of the first coil 12 and the second coil 22 may be located on extensions of imaginary lines perpendicular to the winding axes of the first coil 12 and the second coil 22. In this way, the mounting surfaces of the composite inductor 1 of the present disclosure can be positioned as desired.

[0021] Each of the components constituting the composite inductor 1 of the present disclosure will be described in detail below.

[0022] -First coil element- The first coil element 10 comprises a first magnetic body 11, a first coil 12 provided inside the first magnetic body 11, and a pair of first external electrodes 13 electrically connected to the first coil 12 and exposed from at least one mounting surface of the first magnetic body 11.

[0023] First Magnetic Material The first magnetic material 11 includes first magnetic particles MP1 made of a magnetic material (see FIGS. 4A and 4B). The term "iron powder" as used herein is not limited to powder in a strict sense, but also encompasses powder particles bonded together by heat treatment (sintering), as described below. The first magnetic particles MP1 may contain Fe and / or Si. More specifically, they may be Fe particles or Fe alloy particles. Examples of Fe alloys include Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-B-P-Cu-C alloys, and / or Fe-Si-B-Nb-Cu alloys. The first magnetic particles MP1 may also contain impurities, such as Cr, Mn, Cu, Ni, P, S, and / or Co, that are not intended during manufacturing. The first magnetic particles MP1 may also be contained in a magnetic paste, as will be described in detail in the manufacturing method. Therefore, the iron powder may contain elements (for example, Cr, Al, Li, Zn) that are more easily oxidized than the Fe added when the magnetic paste is prepared.

[0024] The surfaces of the first magnetic particles MP1 described above may be covered with a first insulating coating OL1. Covering the surfaces of the first magnetic particles MP1 with the first insulating coating OL1 can improve the insulation between the first magnetic particles MP1. Methods for forming the insulating coating on the surfaces of the first magnetic particles MP1 include the sol-gel method and the mechanochemical method. The material constituting the first insulating coating OL1 may be an oxide film formed by oxidizing the surfaces of the first magnetic particles MP1. The thickness of the first insulating coating OL1 may be 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 an inductor sample can be photographed with a transmission electron microscope (TEM), and the thickness of the first insulating coating OL1 covering the surfaces of the first magnetic particles MP1 can be measured from the resulting TEM photograph.

[0025] The average particle size of the first magnetic particles MP1 in the first magnetic body 11 may be larger than the average particle size of the second magnetic particles MP2 in the intervening elements 30, which will be described later. Preferably, the average particle size of the first magnetic particles MP1 is 5 μm or more and 30 μm or less, more preferably 5 μm or more and 20 μm or less, and even more preferably 5 μm or more and 10 μm or less. The average particle size of the magnetic particles in the magnetic body can be measured using the procedure described below. A sample of the composite inductor is cut to obtain a cross section of the sample. Specifically, a cross section of the sample is obtained that passes through the center (winding axis) of the coil and is perpendicular to the mounting surface and end surface of the composite inductor. Multiple (e.g., five) regions (e.g., 130 μm × 100 μm) of the obtained cross section are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to determine the circle-equivalent diameter of the magnetic particles. The average of the obtained circle-equivalent diameters is taken as the average particle size of the magnetic particles.

[0026] First Coil The first coil 12 may be configured by winding a metal conductor around the T direction as the winding axis of the coil. As will be described in detail in the "Manufacturing Method of a Composite Inductor," the first coil 12 may be formed by screen printing a conductive paste or the like. While FIG. 1 shows a configuration in which one coil is wound in the T direction, two or more coils may also be wound. The material of the first coil 12 may be a metal conductor such as Ag, Cu, and / or Pd.

[0027] First External Electrodes 13 The pair of first external electrodes 13 may be electrically connected to one end and the other end of the first coil 12, respectively. The pair of first external electrodes 13 may be exposed from the mounting surface of the first magnetic body 11 (the first main surface 1a of the composite inductor 1). Specifically, the first external electrodes 13 may be electrically connected to the first coil 12 via through holes TH extending in the T direction from one end and the other end of the first coil 12, respectively. The first external electrodes 13 may be made of various metal materials, such as Cu, Ni, and / or Sn. The first external electrodes 13 may be formed as a single layer or as a laminated structure of two or more layers. The first external electrodes 13 may be formed by any method. For example, they may be plated electrodes formed by plating (e.g., electrolytic plating) directly on the through holes TH. The through holes TH may be made of a metal conductor, such as Ag, Cu, and / or Pd. The material of the through hole TH may be the same as or different from that of the first coil 12 .

[0028] 1, the first external electrode 13 may be arranged to extend from the first main surface 1a to the first side surface 1e (or from the first main surface 1a to the second side surface 1f) of the composite inductor 1, as shown in Fig. 2. Furthermore, as shown in Fig. 3, the first external electrode 13 may be arranged to extend from the first main surface 1a to the first end surface 1c of the composite inductor 1 (or from the first main surface 1a to the second end surface 1d).

[0029] - Second Coil Element - The second coil element 20 may have substantially the same structure as the first coil element 10. By making the second coil element 20 and the first coil element 10 have substantially the same structure, the manufacturing process of the composite inductor 1 can be simplified, and the composite inductor 1 can be manufactured efficiently. The second coil element 20 may have a structure different from that of the first coil element 10. For example, the magnetic material of the second magnetic body 21 of the second coil element 20 may be different from that of the first magnetic body 11 of the first coil element 10, and / or the number of turns of the second coil 22 of the second coil element 20 may be different from the number of turns of the first coil 12 of the first coil element 10.

[0030] -Intervening element- The intervening element 30 is a structure interposed between the first coil element 10 and the second coil element 20. Specifically, in the embodiment shown in Fig. 1, the surface of the first coil element 10 opposite the mounting surface faces the intervening element 30, and the surface of the second coil element 20 opposite the mounting surface faces the intervening element 30.

[0031] The intermediate element 30 includes second magnetic particles MP2 made of a magnetic material (see FIGS. 4A and 4B). The second magnetic particles MP2 may be made of the same magnetic material as the first magnetic particles MP1. More specifically, the constituent material elements of the intermediate element 30 may be the same as the constituent material elements of the first magnetic body 11 and the second magnetic body 21. By using the same constituent material elements, the manufacturing cost of the composite inductor can be reduced. Note that the second magnetic particles MP2 may be made of a magnetic material different from that of the first magnetic particles MP1.

[0032] The second magnetic particles MP2 have an average particle size smaller than that of the first magnetic particles MP1. As an example, the average particle size of the second magnetic particles MP2 may be 1 μm or more and less than 5 μm, preferably 1 μm or more and 2 μm or less. Because the average particle size of the second magnetic particles MP2 is smaller than that of the first magnetic particles MP1, the magnetic permeability of the first coil element 10 and the second coil element 20 can be made higher than that of the intermediate element 30.

[0033] The surfaces of the second magnetic particles MP2 may be covered with a second insulating coating OL2. The material constituting the second insulating coating OL2 may be an oxide film formed by oxidizing the surfaces of the second magnetic particles MP2. The thickness of the second insulating coating OL2 is different from the thickness of the first insulating coating OL1. This is because, as will be described in detail in the "Method for Manufacturing a Composite Inductor" section below, the first heat treatment conditions for manufacturing the first coil element 10 and the second coil element 20 are different from the second heat treatment conditions for manufacturing the intermediate element 30. The first heat treatment conditions are heat treatment conditions that can suitably heat-treat the first coil element 10 and the second coil element 20, and the second heat treatment conditions are heat treatment conditions that can suitably heat-treat the intermediate element 30. When heat treatment is performed under such heat treatment conditions, the first coil element 10 and the second coil element 20, which include a coil, and the intervening element 30, which does not include a coil, can each be heat treated under suitable heat treatment conditions, thereby optimizing the magnetic permeability of the first coil element 10, the second coil element 20, and the intervening element 30.

[0034] In one embodiment, when the heat treatment temperature under the first heat treatment conditions is higher than that under the second heat treatment conditions, the thickness of the first insulating coating OL1 covering the first magnetic particles MP1 is greater than the thickness of the second insulating coating OL2 covering the second magnetic particles MP2 (see FIG. 4A ). This is because increasing the heat treatment temperature facilitates the formation of an oxide film. In the case of such a composite inductor, the insulation properties of the first coil element 10 and the second coil element 20 can be ensured, and the heat treatment conditions can be optimized for the conductive paste that is the material for the first coil and the second coil. Furthermore, because the second magnetic particles MP2 are not oxidized more than necessary, the decrease in the magnetic permeability of the intermediate element 30 is suppressed, and the intermediate element 30 acts to improve the magnetic performance of the first coil element 10 and the second coil element 20. Note that, since the heat treatment conditions make it difficult to increase the withstand voltage of the intervening element 30, it is preferable to make the thickness of the intervening element 30 relatively thick in order to ensure insulation between the first coil element 10 and the second coil element 20. As an example, it is preferable to make the thickness of the intervening element 30 140 μm or more.

[0035] On the other hand, in another embodiment, when the heat treatment temperature under the first heat treatment condition is lower than the heat treatment temperature under the second heat treatment condition, the thickness of the first insulating coating OL1 covering the first magnetic particles MP1 is thinner than the thickness of the second insulating coating OL2 covering the second magnetic particles MP2 (see FIG. 4B ). In the case of such a composite inductor, oxidation of the second magnetic particles MP2 is promoted, thereby improving the insulating properties of the intervening element 30. This allows the intervening element 30 to act to provide favorable insulation between the first coil element 10 and the second coil element 20, and because the first coil element 10 and the second coil element 20 are not oxidized more than necessary, a decrease in the magnetic permeability of the first coil element 10 and the second coil element 20 is suppressed, thereby suppressing deterioration of the characteristics of the first coil element 10 and the second coil element 20. Note that, since the heat treatment conditions can increase the insulation between the first coil element 10 and the second coil element 20, it is preferable to make the thickness of the intervening element 30 relatively thin in order to ensure the coupling coefficient between the first coil element 10 and the second coil element 20. As an example, it is preferable to make the thickness of the intervening element 30 80 μm or less.

[0036] As described above, according to the composite inductor 1 of the first embodiment, the characteristics of the first coil element 10, the second coil element 20, and the intermediate element 30 can be optimized.

[0037] <Preferred Embodiment of Composite Inductor> In a preferred embodiment of the composite inductor, the thicknesses of the first magnetic body 11 and the second magnetic body 21 may be greater than the thickness of the intervening element 30. Specifically, the thicknesses of the first magnetic body 11 and the second magnetic body 21 may be 150 μm or more and 500 μm or less, and the thickness of the intervening element 30 may be 40 μm or more and 80 μm or less. With such a thickness relationship, the first coil element 10 and the second coil element 20 can be magnetically coupled while being appropriately insulated from each other.

[0038] As described in the "Method for Manufacturing a Composite Inductor," the first magnetic body 11 and the second magnetic body 21 are impregnated with resin, and then the interposing element 30 is interposed between the first coil element 10 and the second coil element 20 to integrate the elements. Therefore, the first magnetic body 11, the second magnetic body 21, and the interposing element 30 may each contain resin. Regarding the resin impregnation rate, the resin impregnation rate of the interposing element 30 may be higher than the resin impregnation rates of the first magnetic body 11 and the second magnetic body 21. The resin impregnation rate depends on the relationship between the surface area of ​​the first magnetic body 11 and the second magnetic body 21 and the surface area of ​​the interposing element 30. Specifically, as described above, the magnetic particles of the first magnetic body 11 and the second magnetic body 21 are smaller than the magnetic particles of the interposing element 30, which is one factor that makes the first magnetic body 11 and the second magnetic body 21 more easily impregnated with resin than the interposing element 30. If the resin impregnation rate of the intervening element 30 is higher than that of the first magnetic body 11 and the second magnetic body 21, the first coil element 10 and the second coil element 20 can be appropriately insulated from each other.

[0039] <Description of Manufacturing Method of Composite Inductor> Next, a manufacturing method of the composite inductor of the present disclosure will be described with reference to Figures 5 to 7. The manufacturing method of the composite inductor of the present disclosure includes a step of manufacturing the first coil element and the second coil element, a step of manufacturing the interposition element, and a step of integrating the elements. In addition, an external electrode forming step may be included as an optional step. The manufacturing steps will be described in detail below.

[0040] --Process for manufacturing the first coil element and the second coil element-- First, magnetic paste for forming the first coil element 10 and the second coil element 20, and conductive paste for forming the first coil 12, the second coil 22, and the through-hole TH are prepared.

[0041] As an example of a method for producing a magnetic paste, first magnetic particles MP1 such as an Fe—Si alloy or Fe—Si—Cr alloy with a cumulative 50% particle diameter (D50) on a volume basis of 5 μm to 30 μm are prepared. These first magnetic particles MP1 are mixed with a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA), and then kneaded to produce a magnetic paste.

[0042] When an Fe—Si alloy is used as the first magnetic particles MP1, the Si content is preferably 2.0 at% or more and 8.0 at% or less. When an Fe—Si—Cr alloy is used as the first magnetic particles MP1, the Si content is preferably 2.0 at% or more and 8.0 at% or less. Furthermore, when an Fe—Si—Cr alloy is used as the first magnetic particles MP1, the Cr content is preferably 0.2 at% or more and 6.0 at% or less.

[0043] An insulating coating may be provided on the surface of the first magnetic particles MP1. The insulating coating is preferably a coating containing a metal oxide, and more preferably an oxide of Si. The sol-gel method is a preferred method for forming the insulating coating. As an example of forming an insulating coating using the sol-gel method, a mixed solution is prepared by mixing a sol-gel coating agent containing Si alkoxide with an organic chain-containing silane coupling agent. This mixed solution is then applied to the surface of the metal magnetic powder, and then subjected to a heat treatment to dehydrate and bond the particles. The insulating coating can then be formed by drying at a predetermined temperature.

[0044] As the conductive paste, for example, a paste containing Ag as a conductive material is prepared.

[0045] After preparing the magnetic paste and the conductor paste, a layer ML1 including the first coil 12 is formed by screen printing or the like (see FIG. 6 ). Then, a layer ML2 including a through-hole TH is sequentially printed on the layer ML1 (see FIG. 6 ). These layers ML1 and ML2 are pressurized by a press process such as warm isostatic pressing (WIP) to form a laminate. After the pressurization process, the laminate is placed in a firing furnace, degreased, and then heat-treated in air under first heat-treatment conditions. By performing the heat-treatment under the first heat-treatment conditions, the first magnetic particles MP1 are oxidized, and a first insulating coating OL1 is formed as an oxide film on the surface of the first magnetic particles MP1. The thickness of the first insulating coating OL1 may be preferably 1 nm or more and 50 nm or less, more preferably 1 nm or more and 30 nm or less, and even more preferably 1 nm or more and 20 nm or less.

[0046] -Process for manufacturing the intermediate element- First, a magnetic paste for forming the intermediate element 30 is prepared. The magnetic paste used is the same as the magnetic paste used to manufacture the first and second coil elements described above, but uses second magnetic particles MP2 such as an Fe-Si alloy or Fe-Si-Cr alloy with a D50 of 1 μm or more and less than 5 μm. In other words, the average particle size of the magnetic paste for the intermediate element 30 is different from the average particle size of the magnetic paste for the first and second coil elements. Furthermore, since no conductive paste is used in the process for manufacturing the intermediate element, no conductive paste is prepared.

[0047] After preparing the magnetic paste, the magnetic layers constituting the interposition element 30 are sequentially printed by screen printing or the like until they reach the desired thickness. Then, a pressure treatment is applied using a press process such as warm isostatic pressing (WIP) to form a laminate. After the pressure treatment, the laminate is placed in a firing furnace, degreased, and then heat treated in air under second heat treatment conditions. By performing heat treatment under the second heat treatment conditions, the second magnetic particles MP2 are oxidized, and a second insulating coating OL2 is formed as an oxide film on the surface of the second magnetic particles MP2. The thickness of the second insulating coating OL2 may be preferably 1 nm to 50 nm, more preferably 1 nm to 30 nm, and even more preferably 1 nm to 20 nm. Note that the second heat treatment conditions are different from the first heat treatment conditions, and therefore the thickness of the second insulating coating OL2 is different from the thickness of the first insulating coating OL1.

[0048] - Step of integrating the elements - After the first coil element 10, the second coil element 20, and the intervening element 30 are each manufactured, they are impregnated with resin. The resin has thermosetting properties and may contain, for example, epoxy resin, silicone resin, or phenol resin. Then, by thermally curing the impregnated resin, the first coil element 10, the second coil element 20, and the intervening element 30 are integrated.

[0049] As one mode of resin impregnation, the first coil element 10, the second coil element 20, and the intervening element 30 may be individually impregnated with resin, and then the intervening element 30 may be interposed between the first coil element 10 and the second coil element 20 to bond them together. With this resin impregnation technique, the resin is appropriately disposed at the interface between the first coil element 10 and the intervening element 30 and the interface between the second coil element 20 and the intervening element 30, so that the elements can be firmly integrated together.

[0050] Furthermore, when each element is individually impregnated with the resin, the resin may be impregnated by degassing each element (e.g., by suction). By degassing each element, the resin can be uniformly distributed throughout the interior of each element.

[0051] As another mode of resin impregnation, the intervening element 30 may be interposed between the first coil element 10 and the second coil element 20, and then the resin may be cured as a unit and then bonded to each other. With this method, the resin is disposed around the first coil element 10, the second coil element 20, and the intervening element 30 by a single resin impregnation, which simplifies the manufacturing process.

[0052] -External Electrode Forming Process- The external electrode forming process is a process for forming a first external electrode 13 electrically connected to the first coil 12 and a second external electrode 23 electrically connected to the second coil 22. The first external electrode 13 and the second external electrode 23 are formed by electrolytic plating at positions where the through-holes TH are exposed on the mounting surface of the first coil element 10 and the mounting surface of the second coil element 20. The plating material may be Cu plating or Ni plating. Other examples include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu, and / or Cu-Ni-Au. In this manner, the composite inductor of this embodiment can be manufactured.

[0053] <Preferred Aspect of the Method for Manufacturing a Composite Inductor> In one aspect of the method for manufacturing a composite inductor, the heat treatment temperature under the second heat treatment conditions may be lower than the heat treatment temperature under the first heat treatment conditions. For example, the heat treatment temperature under the first heat treatment conditions may be 600°C or higher and 1000°C or lower, preferably 600°C or higher and 800°C or lower, and the heat treatment temperature under the second heat treatment conditions may be 400°C or higher and lower than 600°C. Under these first and second heat treatment conditions, as shown in FIG. 4A , the thickness of the second insulating coating OL2 covering the second magnetic particles MP2 can be made thinner than the thickness of the second insulating coating OL2 covering the first magnetic particles MP1. This suppresses a decrease in the magnetic permeability of the intervening element 30, and the intervening element 30 can relatively increase the coupling coefficient between the first coil element 10 and the second coil element 20.

[0054] In this embodiment, the heat treatment time under the first heat treatment condition and the heat treatment time under the second heat treatment condition may be set to, for example, 10 minutes or more and 360 minutes or less. The heat treatment time under the first heat treatment condition and the heat treatment time under the second heat treatment condition may be set to approximately the same. However, the heat treatment conditions are not limited to these. As long as the thickness of the first insulating coating OL1 covering the first magnetic particles MP1 can be made thicker than the thickness of the second insulating coating OL2 covering the second magnetic particles MP2, the heat treatment time under the first heat treatment condition may be longer than the heat treatment time under the second heat treatment condition while maintaining the heat treatment temperatures under the first and second heat treatment conditions at approximately the same levels.

[0055] <Another Preferred Aspect of the Method for Manufacturing a Composite Inductor> In another aspect of the method for manufacturing a composite inductor, the heat treatment temperature under the second heat treatment conditions may be higher than the heat treatment temperature under the first heat treatment conditions. For example, the heat treatment temperature under the second heat treatment conditions may be 600°C or higher and 1000°C or lower, preferably 600°C or higher and 800°C or lower, and the heat treatment temperature under the first heat treatment conditions may be 400°C or higher and lower than 600°C. Under these first and second heat treatment conditions, as shown in FIG. 4B , the thickness of the first insulating coating OL1 covering the first magnetic particles MP1 can be made thinner than the thickness of the second insulating coating OL2 covering the second magnetic particles MP2. This promotes oxidation of the second magnetic particles MP2 and improves the insulating properties of the intervening element 30, thereby enabling the intervening element 30 to provide suitable insulation between the first coil element 10 and the second coil element 20.

[0056] In this embodiment, the heat treatment time for the first heat treatment condition and the heat treatment time for the second heat treatment condition may both be set to 10 minutes or more and 360 minutes or less. The heat treatment time for the first heat treatment condition and the heat treatment time for the second heat treatment condition may be set to approximately the same. However, the heat treatment conditions are not limited to these. As long as the thickness of the first insulating coating OL1 covering the first magnetic particles MP1 can be made thinner than the thickness of the second insulating coating OL2 covering the second magnetic particles MP2, the heat treatment time for the first heat treatment condition may be shorter than the heat treatment time for the second heat treatment condition, while maintaining the heat treatment temperatures for the first and second heat treatment conditions at approximately the same levels.

[0057] The technical scope of the present disclosure is not interpreted solely by the above-described embodiments, but is defined based on the claims. The technical scope of the present disclosure also includes all modifications that are equivalent to the claims and fall within the scope of the claims.

[0058] The method for manufacturing a composite inductor and the composite inductor disclosed herein include the following aspects: <1> A method for manufacturing a composite inductor, comprising: a step of laminating a magnetic material and a conductive material to manufacture, under first heat treatment conditions, a first coil element and a second coil element, each of which includes a magnetic body, a coil disposed inside the magnetic body, and an external electrode electrically connected to the coil and exposed from at least one mounting surface of the magnetic body; a step of manufacturing an intervening element using a magnetic material having the same constituent material elements as the magnetic material, under second heat treatment conditions different from the first heat treatment conditions; and a step of impregnating the first coil element, the second coil element, and the intervening element with resin, and then interposing the intervening element between the first coil element and the second coil element to integrate the elements. <2> The method for manufacturing a composite inductor described in <1>, wherein the heat treatment temperature under the second heat treatment conditions is lower than the firing temperature under the first heat treatment conditions. <3> The method for manufacturing a composite inductor according to <1>, wherein the heat treatment temperature under the second heat treatment conditions is higher than the firing temperature under the first heat treatment conditions. <4> The method for manufacturing a composite inductor according to any one of <1> to <3>, wherein the step of integrating the elements comprises individually curing a resin for the first coil element, the second coil element, and the intervening element, and then bonding them together. <5> The method for manufacturing a composite inductor according to any one of <1> to <3>, wherein the step of integrating the elements comprises interposing the intervening element between the first coil element and the second coil element, and then curing the resin as a whole to bond them together. <6> The method for manufacturing a composite inductor according to any one of <1> to <3>, wherein the resin impregnation is performed by individually immersing the first coil element, the second coil element, and the intervening element in resin, and then suctioning each of the elements.<7> A composite inductor comprising: a first coil element including a first magnetic body, a first coil provided inside the first magnetic body, and a pair of first external electrodes electrically connected to the first coil and exposed from at least one mounting surface of the first magnetic body; a second coil element including a second magnetic body, a second coil provided inside the second magnetic body, and second external electrodes electrically connected to the second coil and exposed from at least one mounting surface of the second magnetic body; and an intermediate element interposed between the first coil element and the second coil element, wherein the magnetic permeabilities of the first magnetic body and the second magnetic body are higher than the magnetic permeability of the intermediate element. <8> A composite inductor according to <7>, wherein the thickness of an insulating coating covering magnetic particles constituting the first magnetic body and the second magnetic body is thicker than the thickness of an insulating coating covering magnetic particles constituting the intermediate element. <9> The composite inductor according to <7>, wherein the thickness of the insulating coating covering the magnetic particles constituting the first magnetic body and the second magnetic body is thinner than the thickness of the insulating coating covering the magnetic particles constituting the intervening element. <10> The composite inductor according to any one of <7> to <9>, wherein the thickness of the first magnetic body and the second magnetic body is thicker than the thickness of the intervening element. <11> The composite inductor according to any one of <7> to <10>, wherein the resin impregnation rate of the first magnetic body and the second magnetic body is higher than the resin impregnation rate of the intervening element. <12> The composite inductor according to any one of <7> to <11>, wherein the particle size of the magnetic particles constituting the first magnetic body and the second magnetic body is larger than the particle size of the magnetic particles constituting the intervening element. <13> The composite inductor according to any one of <7> to <12>, wherein the mounting surface of the first coil element is located opposite the mounting surface of the second coil element. <14> The composite inductor according to <7> to <13>, wherein the mounting surface of the first coil element and the mounting surface of the second coil element are located on an extension line of the winding axes of the first coil and the second coil. <15> The composite inductor according to any one of <7> to <13>, wherein the mounting surface of the first coil element and the mounting surface of the second coil element are located on an extension line of an imaginary line orthogonal to the winding axes of the first coil and the second coil.<16> A composite inductor according to any one of <7> to <15>, wherein the constituent material elements constituting the first magnetic body and the second magnetic body are the same as the constituent material elements constituting the intervening element.

[0059] The composite inductor manufacturing method and the composite inductor of the present disclosure can be suitably used as an electronic component that can improve inductance characteristics.

[0060] REFERENCE SIGNS LIST 1 composite inductor 1a first main surface 1b second main surface 1c first end surface 1d second end surface 1e first side surface 1f second side surface 10 first coil element 11 first magnetic body 12 first coil 13 first external electrode 20 second coil element 21 second magnetic body 22 second coil 23 second external electrode 30 interposed element MP1 first magnetic particle OL1 first insulating coating MP2 second magnetic particle OL2 second insulating coating ML1, ML2 layer

Claims

1. A method for manufacturing a composite inductor, comprising: a step of laminating a magnetic material and a conductive material, and manufacturing, under first heat treatment conditions, a first coil element and a second coil element, each of which comprises a magnetic body, a coil disposed inside the magnetic body, and an external electrode electrically connected to the coil and exposed from at least one mounting surface of the magnetic body; a step of manufacturing an intermediate element under second heat treatment conditions different from the first heat treatment conditions, using a magnetic material whose constituent material elements are the same as those of the magnetic material; and a step of impregnating each of the first coil element, the second coil element, and the intermediate element with resin, and then interposing the intermediate element between the first coil element and the second coil element to integrate the elements together.

2. The method for manufacturing a composite inductor according to claim 1, wherein the heat treatment temperature of the second heat treatment condition is lower than the firing temperature of the first heat treatment condition.

3. The method for manufacturing a composite inductor according to claim 1, wherein the heat treatment temperature of the second heat treatment condition is higher than the firing temperature of the first heat treatment condition.

4. A method for manufacturing a composite inductor according to any one of claims 1 to 3, wherein the step of integrating the elements comprises individually curing the resin of the first coil element, the second coil element, and the intermediate element, and then bonding them together.

5. A method for manufacturing a composite inductor according to any one of claims 1 to 3, wherein the step of integrating the elements together comprises interposing the intervening element between the first coil element and the second coil element, and then bonding them together by curing the resin.

6. A method for manufacturing a composite inductor according to any one of claims 1 to 3, wherein the resin impregnation is carried out by individually immersing each of the first coil element, the second coil element, and the intervening element in resin, and then sucking each of the elements.

7. A composite inductor comprising: a first coil element comprising a first magnetic body, a first coil provided inside the first magnetic body, and a pair of first external electrodes electrically connected to the first coil and exposed from at least one mounting surface of the first magnetic body; a second coil element comprising a second magnetic body, a second coil provided inside the second magnetic body, and second external electrodes electrically connected to the second coil and exposed from at least one mounting surface of the second magnetic body; and an intervening element interposed between the first coil element and the second coil element, wherein the magnetic permeability of the first magnetic body and the second magnetic body is higher than the magnetic permeability of the intervening element.

8. A composite inductor as described in claim 7, wherein the thickness of the insulating coating covering the magnetic particles constituting the first magnetic body and the second magnetic body is thicker than the thickness of the insulating coating covering the magnetic particles constituting the intervening element.

9. A composite inductor as described in claim 7, wherein the thickness of the insulating coating covering the magnetic particles constituting the first magnetic body and the second magnetic body is thinner than the thickness of the insulating coating covering the magnetic particles constituting the intervening element.

10. A composite inductor according to any one of claims 7 to 9, wherein the thickness of the first magnetic body and the second magnetic body is greater than the thickness of the intervening element.

11. A composite inductor according to any one of claims 7 to 10, wherein the resin impregnation rate of the first magnetic body and the second magnetic body is higher than the resin impregnation rate of the interposed element.

12. A composite inductor according to any one of claims 7 to 11, wherein the particle size of the magnetic particles constituting the first magnetic body and the second magnetic body is larger than the particle size of the magnetic particles constituting the intervening element.

13. A composite inductor according to any one of claims 7 to 12, wherein the mounting surface of the first coil element is located opposite the mounting surface of the second coil element.

14. A composite inductor according to any one of claims 7 to 13, wherein the mounting surface of the first coil element and the mounting surface of the second coil element are located on an extension line of the winding axes of the first coil and the second coil.

15. A composite inductor according to any one of claims 7 to 13, wherein the mounting surface of the first coil element and the mounting surface of the second coil element are located on an extension of an imaginary line perpendicular to the winding axes of the first coil and the second coil.

16. A composite inductor according to any one of claims 7 to 15, wherein the constituent material elements constituting the first magnetic body and the second magnetic body are the same as the constituent material elements constituting the intervening element.

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