Coil component, method of manufacturing the same, circuit board, and electronic device

Abstract

The present application provides a coil component and a manufacturing method thereof, a circuit board, and an electronic device. The coil component of one or more embodiments of the present application includes: a base body including a plurality of metal magnetic particles each containing a metal element; a coil conductor having a buried portion disposed inside the base body and a exposed portion exposed outside the base body, the coil conductor having copper as a main component; and an insulating oxide layer covering a surface of the buried portion, the oxide layer containing an oxide of the metal element contained in the plurality of metal magnetic particles and a copper element.

Description

Technical Field

[0001] This invention relates to coil components and their manufacturing methods, circuit boards, and electronic devices. Background Technology

[0002] Traditional coil components consist of a matrix made of magnetic material and a coil conductor disposed within that magnetic matrix. In recent years, with the continuous development of high-current circuits, soft magnetic metal materials that are not prone to magnetic saturation even when large currents flow are increasingly used as the matrix material for coil components.

[0003] Examples of conventional coil components are disclosed in International Publication No. 2018 / 088264 (Patent Document 1). The coil component disclosed in Patent Document 1 includes: a matrix comprising metallic magnetic particles made of a soft magnetic metal material; and a coil conductor embedded in the matrix and coated with polyimide resin.

[0004] Japanese Patent Application Publication No. 2019-153650 (Patent Document 2) discloses another example of a conventional coil component. The coil component disclosed in Patent Document 2 includes: a substrate comprising metallic magnetic particles made of a soft magnetic metal material; and a metal plate embedded in the substrate. The metal plate of Patent Document 2 includes a base material layer made of a conductive metal and a plating layer formed on one side of the base material layer.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2018 / 088264

[0008] Patent Document 2: Japanese Patent Application Publication No. 2019-153650 Summary of the Invention

[0009] The technical problem that the invention aims to solve

[0010] As disclosed in Patent Document 1, by coating the surface of the coil conductor with a resin material such as polyimide, the insulation withstand voltage of the coil component can be improved. That is, by using a resin insulating film disposed on the surface of the coil conductor, the occurrence of short circuits between the coil conductor and the metallic magnetic particles contained in the substrate can be suppressed. However, since the insulating film is made of a non-magnetic resin, the magnetic properties (e.g., inductance) of the coil component deteriorate because the surface of the coil conductor is covered by a resin insulating film. In Patent Document 1, the reduction in magnetic properties is suppressed by thinning the resin insulating film to a degree that does not excessively reduce the insulation withstand voltage; however, the deterioration of magnetic properties cannot be avoided because the resin insulating film is disposed on the surface of the coil conductor.

[0011] If the surface of the coil conductor is not covered by a resin insulating film, there will be no problem with the deterioration of magnetic properties caused by the insulating film. However, without a resin insulating film on the surface of the coil conductor, a short circuit can easily occur between the coil conductor and the metallic magnetic particles. Furthermore, when the space between the coil conductor and the metallic magnetic particles is not filled with a resin insulating film, a gap will inevitably form between them. Therefore, when using the coil component, the following problems exist: due to the oxygen present in the gap between the coil conductor and the metallic magnetic particles, oxidation of the coil conductor occurs, leading to a deterioration of the electrical properties of the coil component. Additionally, the following problem exists: moisture intrudes into the gap between the coil conductor and the metallic magnetic particles, and due to the moisture intruding into this gap, oxidation of the coil conductor occurs.

[0012] The object of this invention is to solve or mitigate at least some of the aforementioned problems. One more specific object of this invention is to provide a coil component capable of suppressing the deterioration of magnetic properties and exhibiting excellent insulation withstand voltage and oxidation resistance.

[0013] Other than those described above, the objectives of this invention will become clear from the overall description of the specification. The technical solutions described in the claims can also solve technical problems beyond those that can be grasped according to the "Technical Problem to be Solved by the Invention" section.

[0014] Means for solving technical problems

[0015] A coil component according to one or more embodiments of the present invention includes: a substrate comprising a plurality of metallic magnetic particles, each of the plurality of metallic magnetic particles containing a metallic element; a coil conductor with copper as the main component having an embedded portion disposed inside the substrate and an exposed portion exposed outside the substrate; and an insulating oxide layer covering the surface of the embedded portion, comprising oxides of the metallic elements contained in the plurality of metallic magnetic particles and copper element.

[0016] In one or more embodiments of the present invention, each of the plurality of metallic magnetic particles contains a metallic element having a greater tendency to ionize than copper.

[0017] In one or more embodiments of the present invention, each of the plurality of metallic magnetic particles has an oxide film on its surface and is bonded to adjacent metallic magnetic particles through the oxide film.

[0018] In one or more embodiments of the present invention, a portion of the plurality of metallic magnetic particles is adjacent to the coil conductor through the oxide layer and the oxide film.

[0019] In one or more embodiments of the present invention, the oxide layer contains zinc.

[0020] In one or more embodiments of the present invention, the zinc content in the oxide layer is higher than the zinc content in the oxide film.

[0021] In one or more embodiments of the present invention, the atomic proportion of zinc in the oxide layer is more than 1.0 at% and less than 25 at%.

[0022] One or more embodiments of the present invention relate to a circuit board that includes any of the coil components described above. One or more embodiments of the present invention relate to an electronic device that includes the circuit board described above.

[0023] A method for manufacturing a coil component according to one or more embodiments of the present invention includes: a preparation step for preparing an intermediate body, the intermediate body including a main body and a conductor portion embedded within the main body, the main body comprising a plurality of metallic magnetic particles, the conductor portion being primarily composed of copper; a first heating step for forming an oxide film comprising copper oxide by heating the intermediate body at a first temperature to cover the surface of the conductor portion; and a second heating step for heating the intermediate body at a second temperature higher than the first temperature after heating at the first temperature to generate an oxide film comprising oxides of the metal elements contained in each of the plurality of metallic magnetic particles, thereby forming a substrate from the main body and forming an insulating oxide layer comprising the oxides and copper elements. In the second heating step, at least a portion of the copper oxide contained in the oxide film is reduced.

[0024] In the second heating step of one or more embodiments of the present invention, an oxide film is formed on each of the plurality of metallic magnetic particles, and the plurality of metallic magnetic particles are bonded to adjacent metallic magnetic particles through the oxide film to form the substrate.

[0025] In one or more embodiments of the present invention, the conductor portion is covered by a thermally decomposable insulating film, which is decomposed during the first heating process.

[0026] In the second heating step of one or more embodiments of the present invention, the intermediate is heated in an atmosphere with a lower oxygen concentration than that of the first heating step.

[0027] In one or more embodiments of the present invention, the preparation process includes the process of applying a suspension containing zinc oxide to the surface of the conductor portion.

[0028] In a second heating step of one or more embodiments of the present invention, the oxide layer is formed in a manner that includes zinc oxide.

[0029] Invention Effects

[0030] Using the invention disclosed in this specification, it is possible to provide coil components that can suppress the deterioration of magnetic properties and have excellent insulation withstand voltage and oxidation resistance. Attached Figure Description

[0031] Figure 1 This is a perspective view of a coil component of one embodiment of the present invention mounted on a mounting substrate.

[0032] Figure 2 yes Figure 1 A cross-sectional view of the coil component along line II.

[0033] Figure 3 It is Figure 2 An enlarged cross-sectional view showing a portion of the cross-section.

[0034] Figure 4 This is a flowchart illustrating the manufacturing process of a coil component according to one embodiment of the present invention.

[0035] Figure 5 This is a perspective view schematically showing an intermediate body produced in the manufacturing process of a coil component according to one or more embodiments of the present invention.

[0036] Figure 6 This is an enlarged cross-sectional view showing a portion of the cross-section of an intermediate body before the heating of the first heating step in the manufacturing process of a coil component according to one embodiment of the present invention.

[0037] Figure 7 This is an enlarged cross-sectional view showing a portion of the cross-section of an intermediate body after the first heating step and before the second heating step in the manufacturing process of a coil component according to one embodiment of the present invention.

[0038] Explanation of reference numerals in the attached figures

[0039] 1. Coil component, 10. Substrate, 25. Coil conductor, 25a. Embedded part, 25b, 25c. Exposed part, 31. First metal magnetic particle, 32. Second metal magnetic particle, 41, 42. Oxide film, 45. Adhesive resin, 50. Copper oxide film, 55. Void, 60. Oxide layer. Detailed Implementation

[0040] Various embodiments of the present invention will now be described with appropriate reference to the accompanying drawings. Identical components in the multiple drawings are labeled with the same reference numerals in those drawings. It should be noted that, for ease of explanation, the drawings are not necessarily drawn to an exact scale. The embodiments of the present invention described below are not intended to limit the technical solutions in the claims. The elements described in the following embodiments are not necessarily essential to the technical solutions of the invention.

[0041] Reference Figures 1-3 A coil component 1 according to one embodiment of the present invention will be described. Figure 1 This is a perspective view of the coil component 1 mounted on the mounting base plate 2a. Figure 2 This is a cross-sectional view obtained by cutting coil component 1 with cutting wire II. Figure 3 It is Figure 2 The enlarged cross-sectional view is obtained by magnifying a portion of the cross-section shown. Figure 1 and Figure 2 The W-axis, L-axis, and Z-axis, which are orthogonal to each other, are shown in the diagram. In this specification, unless the context dictates otherwise, the "length," "width," and "thickness" directions of coil component 1 are respectively... Figure 1 The L-axis, W-axis, and T-axis directions are used as references in this specification. The orientation and arrangement of the components of coil assembly 1 are sometimes described using the L-axis, W-axis, and Z-axis directions as a reference.

[0042] Coil component 1 can be applied to inductors, transformers, filters, reactors, and various other coil components. Coil component 1 can also be applied to coupled inductors, choke coils, and various other magnetically coupled coil components. The applications of coil component 1 are not limited to those specified in this specification.

[0043] like Figure 1 and Figure 3 As shown, the coil component 1 includes: a substrate 10 formed of a magnetic material; a coil conductor 25 disposed in the substrate 10; and an oxide layer 60 disposed between the coil conductor 25 and the substrate 10. The coil conductor 25 has: an embedded portion 25a disposed inside the substrate 10; an exposed portion 25b extending from one end of the embedded portion 25a to the outside of the substrate 10; and an exposed portion 25c extending from the other end of the embedded portion 25a to the outside of the substrate 10.

[0044] The coil component 1 is mounted on the mounting substrate 2a. Pad portions 3a and 3b are provided on the mounting substrate 2a. The coil component 1 is mounted on the mounting substrate 2a by joining the exposed portion 25b of the coil conductor 25 to the pad portion 3a and the exposed portion 25c of the coil conductor 25 to the pad portion 3b. As described above, the circuit board 2 includes the coil component 1 and the mounting substrate 2a for mounting the coil component 1. The circuit board 2 may include the coil component 1 and various electronic components other than the coil component 1.

[0045] Circuit board 2 can be mounted in various electronic devices. Electronic devices that can mount circuit board 2 include smartphones, tablets, game consoles, automotive electrical components, servers, and various other electronic devices. Electronic devices mounting coil component 1 are not limited to those specified in this specification. Coil component 1 can also be a built-in component embedded within circuit board 2.

[0046] In the illustrated embodiment, the substrate 10 has a generally cuboid shape. The substrate 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f, and the outer surface of the substrate 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b are opposite to each other, the first end surface 10c and the second end surface 10d are opposite to each other, and the first side surface 10e and the second side surface 10f are opposite to each other. Figure 1 In this configuration, the first main surface 10a is located on the upper side of the substrate 10; therefore, the first main surface 10a is sometimes referred to as the "upper surface." Similarly, the second main surface 10b is sometimes referred to as the "lower surface." The magnetically coupled coil component 1 is arranged with the second main surface 10b facing the mounting substrate 2a; therefore, the second main surface 10b is sometimes referred to as the "mounting surface." When referring to the vertical direction of the coil component 1, the term "mounting surface" is used. Figure 1 The vertical direction is used as the reference. In this specification, unless otherwise interpreted from the context, the "length," "width," and "thickness" directions of coil component 1 are respectively... Figure 1 The L-axis, W-axis, and T-axis are defined in the diagram. The L-axis, W-axis, and T-axis are orthogonal to each other.

[0047] In one or more embodiments of the present invention, the coil component 1 is formed with a length dimension (dimension in the L-axis direction) of 1.0 to 12.0 mm, a width dimension (dimension in the W-axis direction) of 1.0 to 12.0 mm, and a height dimension (dimension in the T-axis direction) of 1.0 to 6.0 mm. The coil component 1 may also be formed with a length dimension (dimension in the L-axis direction) of 0.2 to 6.0 mm, a width dimension (dimension in the W-axis direction) of 0.1 to 4.5 mm, and a height dimension (dimension in the T-axis direction) of 0.1 to 4.0 mm. These dimensions are merely illustrative; any size may be used for the coil component 1 to which the present invention is applied, provided it does not depart from the spirit of the invention.

[0048] The matrix 10 is made of a magnetic material. In one or more embodiments of the present invention, the matrix 10 comprises a plurality of metallic magnetic particles. The metallic magnetic particles are particles or powders made of soft magnetic metallic materials. The metallic magnetic particles contain metallic elements that have a greater tendency to ionize than copper. The metallic magnetic particles are, for example, powders of Fe-Cr-Si alloys. Fe and Cr have a greater tendency to ionize than copper (Cu). The soft magnetic metallic materials used for the metallic magnetic particles are not limited to Fe-Cr-Si alloys. The soft magnetic metallic materials used for the metallic magnetic particles are, for example, (1) alloy-based Fe-Si-Al or Fe-Ni, (2) amorphous Fe-Si-Cr-BC or Fe-Si-B-Cr, or (3) particles of a mixture of these materials. When the metallic magnetic particles are made of alloy-based materials, the Fe content in the metallic magnetic particles can be 80 wt% or more and less than 97 wt%. When the metallic magnetic particles are made of amorphous materials, the Fe content in the metallic magnetic particles can be 72 wt% or more and less than 85 wt%. The total content of Si and metal elements that are more easily oxidized than copper in the metallic magnetic particles can be 3 wt% or more, or 8 wt% or more, or 10 wt% or more.

[0049] In one or more embodiments of the present invention, the particle size of the metallic magnetic particles contained in the matrix 10 is distributed according to a predetermined particle size distribution. The metallic magnetic particles, for example, have an average particle size of 1 μm to 10 μm. The average particle size of the metallic magnetic particles contained in the matrix 10 can be determined as follows: the matrix 10 is cut along its thickness direction (T-axis direction) to expose a cross-section, and the particle size distribution of the metallic magnetic particles contained in the cross-section is determined based on an SEM image obtained by taking the cross-section at a magnification of 1000x to 5000x using a scanning electron microscope (SEM). For example, 50% of the particle size distribution obtained based on the SEM image can be used as the average particle size of the metallic magnetic particles. The matrix 10 can be composed of one type of metallic magnetic particle, or it can be composed of two or more metallic magnetic particles with different materials and / or average particle sizes. When the matrix 10 is composed of two or more types of metallic magnetic particles, these two or more metallic magnetic particles can be composed of different soft magnetic metal materials. For example, the matrix 10 can be a mixture of metallic magnetic particles composed of Fe-Cr-Si alloys and metallic magnetic particles composed of Fe-Ni alloys. When the matrix 10 is composed of two or more types of metallic magnetic particles, these two or more types of metallic magnetic particles can have different average particle sizes. The fact that the matrix 10 includes a mixture of two or more types of metallic magnetic particles with different average particle sizes can be confirmed when generating a particle size distribution based on SEM images, by observing two or more peaks appearing in the particle size distribution.

[0050] The coil conductor 25 is primarily composed of copper. In this specification, "primary component" refers to the component with the highest content based on a mass ratio. Therefore, in the coil conductor 25, copper has the highest content based on a mass ratio. To reduce resistance, the copper content in the coil conductor 25 can be 90 wt% or more, 95 wt% or more, 99 wt% or more, or even higher. In addition to copper, the coil conductor 25 may also contain Ni, Sn, Zn, and / or other elements. The coil conductor 25 is a conductor made of a metal primarily composed of copper. The coil conductor 25 can be formed, for example, by bending a metal plate or wire. The coil conductor 25 can also be formed, for example, by sintering a paste primarily composed of copper. In the illustrated embodiment, the exposed portion 25b of the coil conductor 25 extends from one end of the embedded portion 25a along the first end face 10c of the substrate 10 and extends from the lower end of the first end face 10c along the mounting surface 10b. The exposed portion 25c of the coil conductor 25 extends from the other end of the embedded portion 25a along the second end face 10d of the substrate 10, and extends from the lower end of the second end face 10d along the mounting surface 10b. Thus, the coil conductor 25 shown in the figure is bent at the respective boundaries of the embedded portion 25a and the exposed portions 25b and 25c, at a position corresponding to the lower end of the first end face 10c, and at a position corresponding to the lower end of the second end face 10d. The exposed portions 25b and 25c applicable to the present invention are not limited to the illustrated arrangement. The exposed portions 25b and 25c can have any shape and can be positioned arbitrarily, as long as they are exposed from the substrate 10. When the exposed portion 25b does not extend to the mounting surface 10b, the coil component 1 may include an external electrode (not shown) connected to the exposed portion 25b. Known external electrodes can be used as this external electrode. For example, the external electrode can be obtained by forming a base electrode by applying a conductive paste to the surface of the substrate 10, and forming one or more plating layers on the surface of the base electrode. Similarly, if the exposed portion 25c does not extend to the mounting surface 10b, the coil component 1 may also include an external electrode (not shown) connected to the exposed portion 25c. Alternatively, the exposed portions 25b and 25c may directly function as external electrodes. In this case, the exposed portions 25b and 25c are directly or indirectly connected to conductive components (e.g., pads 3a, 3b) of the mounting substrate 2.

[0051] The shape of the coil conductor 25 applicable to this invention is not limited to the shape shown in the figure. The embedded portion 25a of the coil conductor 25 can have a spiral shape. The embedded portion 25a with a spiral shape can extend spirally about an axis that passes through the intersection of the diagonals of the first main surface 10a, which has a rectangular shape when viewed from above, and extends along a direction perpendicular to the first main surface 10a (T-axis direction). The shapes of the exposed portions 25b and 25c can also be modified from the shape shown in the figure. In the coil conductor 25 shown in the figure, the embedded portion 25a and the exposed portions 25b and 25c have the same cross-sectional shape. The embedded portion 25a of the coil conductor 25 can have a circular or elliptical cross-section. The coil conductor 25 can be a straight wire with a wire diameter of 1.5 mm. The exposed portions 25b and 25c can be formed by pressing the wire. The exposed portions 25b and 25c can, for example, be formed to have a thickness in the range of 0.1 mm to 0.5 mm.

[0052] When the embedded portion 25a has a spiral shape, the embedded portion 25a extends around the coil axis. The embedded portion 25a with a spiral shape can be wound multiple turns around the coil axis. The coil axis can be a virtual axis extending along any one of the T-axis, L-axis, and W-axis. A portion of the substrate 10 can be provided between adjacent turns of the embedded portion 25a wound multiple turns around the coil axis. An insulating material with copper oxide as its main component can be provided between adjacent turns of the embedded portion 25a wound multiple turns around the coil axis.

[0053] Next, refer to Figure 3 The microstructure near the boundary between the substrate 10 and the embedded portion 25a of the coil conductor 25 will be described. Figure 3 It is Figure 2 The enlarged cross-sectional view shows region A in the cross-section of the coil component 1. Region A is the area spanning the embedded portion 25a of the coil conductor 25 and the substrate 10. Figure 3 In the example shown, the substrate 10 comprises two types of metallic magnetic particles with different average particle sizes. Specifically, it comprises a plurality of first metallic magnetic particles 31 and a plurality of second metallic magnetic particles 32 with an average particle size smaller than the first metallic magnetic particles 31. The first metallic magnetic particles 31 and the second metallic magnetic particles 32 may be formed of the same soft magnetic metal material or of different soft magnetic metal materials.

[0054] On the surface of the metallic magnetic particles contained in the substrate 10, an insulating oxide film comprising oxides of the metallic elements contained in the metallic magnetic particles can be formed. This can be, for example... Figure 3As shown, an oxide film 41 is formed on the surface of the first metallic magnetic particle 31, and an oxide film 42 is formed on the surface of the second metallic magnetic particle 32. The oxide films on the surfaces of the metallic magnetic particles contain oxides of Fe and other constituent elements of the metallic magnetic particles. For example, in the case where the metallic magnetic particles are composed of an Fe-Cr-Si alloy, the oxide film on their surface contains oxides of Fe, Cr, and Si. The first metallic magnetic particle 31 is bonded to adjacent first metallic magnetic particles 31 or second metallic magnetic particles 32 via oxide films 41 and / or oxide films 42.

[0055] An oxide layer 60 is formed between the embedded portion 25a of the coil conductor 25 and the first and second magnetic metal particles 31 and 32, covering the surface of the embedded portion 25a. The oxide layer 60 may be adjacent to the embedded portion 25a. The oxide layer 60 may be formed between the embedded portion 25a and the first and second magnetic metal particles 31 and 32 in a manner that fills the space between them. The oxide layer 60 is adjacent to the first magnetic metal particle 31 through an oxide film 41 and adjacent to the second magnetic metal particle 32 through an oxide film 42. Alternatively, there may be gaps between the oxide layer 60 and the first and / or second magnetic metal particles 31 and 32.

[0056] As shown in the figure, the oxide layer 60 can cover the entire surface area of ​​the embedded portion 25a. For example, when the substrate 10 is cut along the T-axis to expose the cross-section, SEM images of the cross-section are taken at 5000x magnification from each of three (or five or more) points evenly spaced along the L-axis, with the field of view including a portion of the surface of the embedded portion 25a and the substrate 10. If the entire surface of the embedded portion 25a is covered by the oxide layer 60 in the obtained SEM images, it can be determined that the oxide layer 60 covers the entire surface of the embedded portion 25a. In this way, the surface of the embedded portion 25a of the coil conductor 25 is covered by the oxide layer 60, and the space between the embedded portion 25a and the first metallic magnetic particle 31 and the second metallic magnetic particle 32 is filled by the oxide layer 60. Therefore, it is possible to prevent or suppress the atmosphere or moisture in the atmosphere from reaching the embedded portion 25a through the substrate 10 when using the coil component 1.

[0057] In one or more embodiments of the present invention, the oxide layer 60 comprises an oxide of a metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32. For example, when the first metallic magnetic particles 31 and the second metallic magnetic particles 32 are composed of an Fe-Cr-Si alloy, the oxide layer 60 comprises an oxide of at least one of Fe and Cr. Because the oxide layer 60 comprises an oxide of a metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32, the relative permeability of the oxide layer 60 is higher than that of conventional resin-based (e.g., polyimide-based) insulating films. The oxide layer 60 may also comprise an oxide of a constituent element of the first metallic magnetic particles 31 and the second metallic magnetic particles 32 (e.g., Si) other than a metal element. When the substrate 10 is composed of a single type of metallic magnetic particle, the oxide layer 60 comprises at least one of one or more metal elements contained in that metallic magnetic particle. For example, when the substrate 10 comprises a single type of metallic magnetic particle composed of an Fe-Cr-Si alloy, the oxide layer 60 comprises at least one of Fe and Cr. When the substrate 10 is composed of two or more types of metallic magnetic particles, the oxide layer 60 contains at least one of one or more metallic elements contained in any of the two or more types of metallic magnetic particles. For example, when the substrate 10 contains a first type of metallic magnetic particle composed of an Fe-Cr-Si alloy and a second type of metallic magnetic particle composed of an Fe-Ni alloy, the oxide layer 60 contains at least one of Fe, Cr, and Ni elements.

[0058] In one or more embodiments of the present invention, the oxide layer 60 may contain an oxide comprising the metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32, and also contain copper. The copper element may be present in the oxide layer as copper oxide.

[0059] In SEM images obtained by taking cross-sections of the substrate 10 at magnifications of 5000x to 20000x, the boundaries between the oxide layer 60 and the embedded portion 25a of the coil conductor 25, as well as the boundaries between the oxide layer 60 and the first metallic magnetic particles 31 and the second metallic magnetic particles 32, can be identified by differences in brightness. The fact that the oxide layer 60 contains oxides of metal elements contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32 can be confirmed by energy-dispersive X-ray diffraction (EDS) analysis of the cross-section of the substrate 10. Specifically, if EDS analysis of the cross-section of the substrate 10 confirms the presence of both metal elements and oxygen elements contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32 in the oxide layer 60, then it can be confirmed that the oxide layer 60 contains oxides of metal elements contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32. When reconstructing the distribution data of each element obtained from EDS analysis of the cross section through the substrate 10 along a line traversing the oxide layer 60 (e.g., a line extending along the T-axis direction), the count value of the metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32 on this scan line can be larger the further away from the embedment portion 25a (the closer to the first metallic magnetic particles 31 and the second metallic magnetic particles 32). That is, the detection intensity of the metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32 can be stronger the further away from the embedment portion 25a. On the other hand, the detection intensity of copper on the same scan line can be stronger the closer to the embedment portion 25a.

[0060] The oxide layer 60 exhibits excellent insulation properties. The oxide layer 60 contains hematite, silicon dioxide, and / or other insulating oxides, thus exhibiting excellent insulation properties. The oxide layer 60, for example, has 10... 8 The coil conductor 25 has a high resistivity of Ω·cm or higher. Thus, the surface of the embedded portion 25a of the coil conductor 25 is covered by an insulating oxide layer 60, thereby suppressing the occurrence of short circuits between the coil conductor 25 and the first and second metallic magnetic particles 31 and 32. In other words, the coil component 1 has excellent insulation withstand voltage.

[0061] As described above, when the embedded portion 25a has a spiral shape, a portion of the substrate 10 can be provided between adjacent turns of the embedded portion 25a. In this case, an oxide layer 60 can be provided between the region of the substrate 10 provided between adjacent turns of the embedded portion 25a and the surface of the embedded portion 25a. Thus, adjacent turns are separated by the insulating oxide layer 60, thereby suppressing the occurrence of short circuits between different turns constituting the coil conductor 25. Therefore, the coil component 1 has excellent insulation withstand voltage.

[0062] When the embedded portion 25a has a spiral shape, instead of providing a substrate 10, an insulating material with copper oxide as the main component may be provided between adjacent turns of the embedded portion 25a. This insulating material with copper oxide as the main component can be used to suppress the occurrence of short circuits between different turns constituting the coil conductor 25.

[0063] In one or more embodiments of the present invention, the oxide layer 60 contains zinc. Zinc may be contained in the oxide layer 60 as zinc oxide. The oxide layer 60 contains zinc, for example, in a proportion of 1.0 at% to 25 at%. Zinc may be contained in at least one of the oxide film 41 of the first metallic magnetic particle 31 and the oxide film 42 of the second metallic magnetic particle 32. In one or more embodiments, the proportion (atomic ratio) of zinc in the oxide layer 60 is higher than the proportion (atomic ratio) of zinc in the oxide film 41 and the oxide film 42. By containing zinc oxide in the oxide layer 60, the oxide layer 60 can be made denser. This further suppresses the entry of atmospheric oxygen or moisture into the buried portion 25a when using the coil component 1.

[0064] Next, refer to Figures 4-7 An exemplary manufacturing method of a coil component 1 according to one embodiment of the present invention will be described. Figure 4 This is a flowchart illustrating the manufacturing process of a coil component 1 according to one embodiment of the present invention. In the following description, it is assumed that the coil component 1 is manufactured by compression molding. Besides compression molding, the coil component 1 can also be manufactured by any known method. For example, the coil component 1 can be manufactured by sheet lamination, printing lamination, thin film processing, or paste construction.

[0065] First, in process S1, intermediate 100 is produced. As described later, intermediate 100 is subjected to heat treatment in subsequent processes. Figure 5 The intermediate 100 is schematically represented. As shown, the intermediate 100 comprises: a main body 110 made of magnetic material; and a conductor portion, primarily composed of copper, partially embedded within the main body 110. In the illustrated embodiment, the conductor portion 125 is a metal plate primarily composed of copper. A resin insulating film may or may not be provided on the surface of the conductor portion 125. A suspension obtained by dispersing zinc oxide (ZnO) powder in ethanol may be applied to the area of ​​the conductor portion 125 embedded within the main body 110. Copper wire can be used instead of the aforementioned copper plate as the conductor portion 125.

[0066] In the fabrication of intermediate 100, a conductor portion 125 is placed in a molding die, and a metallic magnetic paste containing metallic magnetic particles is added to the molding die containing the conductor portion 125. A predetermined molding pressure (e.g., 500 kN to 5000 kN) is applied to the metallic magnetic paste in the molding die. As a result, the metallic magnetic paste is molded into a main body 110, and a portion of the conductor portion 125 is embedded within the main body 110. In one embodiment, the molding pressure is adjusted so that the apparent density of the main body 110 is 6.0 g / cm³. 3 Magnetic pastes can be obtained by mixing metallic magnetic particles, such as Fe-Cr-Si alloy powder, with a binder resin and a solvent. The metallic magnetic particles can contain a variety of metallic magnetic particles with different particle sizes. The binder resin is, for example, an acrylic resin or a known resin other than acrylic resin.

[0067] As described above, the coil component 1 can be manufactured by various methods other than compression molding. In step S1, an intermediate body 100, in which a conductor portion 125, primarily composed of copper, is embedded within a body 110 containing metallic magnetic particles, can be manufactured using a method other than compression molding. The intermediate body 100 can also be manufactured, for example, by a sheet lamination method. When the intermediate body 100 is manufactured by a sheet lamination method, firstly, a slurry (the adhesive resin being, for example, acrylic resin or a known resin other than acrylic resin) obtained by mixing metallic magnetic particles and a thermally decomposable binder resin is used to form multiple sheet-shaped magnetic body sheets using various sheet forming machines such as a die-casting sheet forming machine. Next, through holes are formed at predetermined positions on the insulating sheet using a laser processing machine or a processing machine other than a laser processing machine. A conductive paste containing copper as a conductive material is applied to the magnetic body sheet with the through holes in a desired pattern, thereby obtaining a magnetic body sheet with a conductor pattern. At this time, the through holes formed on the magnetic body sheet are filled with conductive paste. The conductive paste can be applied, for example, by screen printing. Next, magnetic sheets with conductor patterns are stacked in a prescribed order and, for example, heated and pressed at 80°C with 300 kN to obtain intermediate 100.

[0068] Figure 6 This is a magnified view of a portion of the cross-section obtained by cutting the intermediate body 100 produced in process S1 along the T-axis. Figure 6 The area shown is equivalent to Figure 2 Region A. Figure 6As shown, the main body 110 includes: a plurality of first magnetic metal particles 31; and second magnetic metal particles 32 having an average particle size smaller than the first magnetic metal particles 31. An adhesive resin 45 is filled in the gaps between adjacent magnetic metal particles and between the conductor portion 125 and the magnetic metal particles. In the illustrated embodiment, the conductor portion 125 does not have a resin-based insulating film; therefore, the conductor portion 125 is directly adjacent to the first magnetic metal particles 31 and the second magnetic metal particles 32, or adjacent to them through the adhesive resin 45. As described above, the surface of the conductor portion 125 can be covered by an insulating film made of a thermally decomposable resin. In this case, the conductor portion 125 is adjacent to the first magnetic metal particles 31 and the second magnetic metal particles 32 through the resin-based insulating film, or adjacent to them through both the resin-based insulating film and the adhesive resin 45.

[0069] Next, in step S2, the intermediate 100 produced in step S1 undergoes a first heat treatment. Specifically, the intermediate 100 is placed in a heating furnace and heated in an atmospheric atmosphere at, for example, 250–350°C for 30–120 minutes. Through this first heat treatment, the adhesive resin 45 is decomposed, and a copper oxide film 50 containing copper oxide is formed on the surface of the portion of the conductor 125 where it is embedded in the main body 110. When the surface of the conductor 125 is covered by an insulating film made of a thermally decomposable resin, in the first heat treatment, the intermediate 100 is heated to a temperature above the thermal decomposition temperature of the resin constituting the insulating film on the surface of the conductor 125. Therefore, the insulating film on the surface of the conductor 125 is thermally decomposed in the first heat treatment, and a copper oxide film 50 containing copper oxide is formed on the surface of the portion of the conductor 125 where it is embedded in the main body 110. Thus, when the conductor portion 125 is covered by a resin insulating film, the area around the conductor portion 125 where the resin insulating film existed before the first heat treatment will not become a void but will be filled by the copper oxide film 50. The first heat treatment is performed in an oxygen atmosphere, therefore, the oxidation of copper contained in the conductor portion 125 is promoted during the first heat treatment, and a copper oxide film 50 is formed on the surface of the conductor portion 125 in a manner that fills the voids created by the decomposition of the resin insulating film and the adhesive resin 45.

[0070] The portion of the conductor 125 embedded within the main body 110 can have a spiral shape. When the portion of the conductor 125 embedded within the main body 110, having an insulating film on its surface, has a spiral shape, the insulating film undergoes thermal decomposition during the first heat treatment. The space occupied by the insulating film before thermal decomposition is filled with copper oxide generated from the oxidation of copper contained in the conductor 125. In other words, when the conductor 125 with an insulating film is embedded within the main body 110, a copper oxide film 50 is also provided between adjacent turns of the spiral-shaped conductor 125. This copper oxide film 50 provided between adjacent turns can suppress the occurrence of short circuits between adjacent turns of the conductor 125.

[0071] The main component of the copper oxide film 50 can be copper oxide (CuO). Thus, through the first heat treatment, the main body 110 is degreased, and the surface of the conductor portion 125 is oxidized. The heating conditions in the first heat treatment can be appropriately changed so that the thickness of the copper oxide film 50 is 0.1 μm or more. The heating conditions in the first heat treatment are set such that the metallic magnetic particles contained in the main body 110 do not oxidize and form an oxide film on their surface. When the heating temperature in the first heat treatment is 250–350°C, the first metallic magnetic particles 31 and the second metallic magnetic particles 32 are made of a material from which an oxide film will not form on the surface at the heating temperature in the first heat treatment.

[0072] When a suspension of zinc oxide (ZnO) is applied to the surface of the conductor portion 125 in process S1, and a copper oxide film 50 is formed on the surface of the conductor portion 125, the zinc oxide present on the surface of the conductor portion 125 is taken into the copper oxide film 50.

[0073] Figure 7 This is an enlarged view of a portion of the cross-section obtained by cutting the intermediate body 100 along the T-axis after the first heat treatment in process S2. As shown, since the adhesive resin is decomposed during the first heat treatment, the gaps between adjacent magnetic metal particles in the area filled with adhesive resin 45 before the first heat treatment become voids 55. On the other hand, the adhesive resin 45 filling the space between the conductor portion 125 and the magnetic metal particles is also decomposed, but the gaps between the conductor portion 125 and the magnetic metal particles do not become voids but are filled by a copper oxide film 50. The first heat treatment is performed in an oxygen atmosphere, therefore, the oxidation of copper contained in the conductor portion 125 is promoted during the first heat treatment, and a copper oxide film 50 is formed on the surface of the conductor portion 125 in such a way as to fill the voids formed by the decomposition of the adhesive resin 45. The copper oxide film 50 can be formed to cover the entire area of ​​the surface of the conductor portion 125 adjacent to the main body 110.

[0074] Next, in step S3, the intermediate 100 that underwent the first heat treatment is subjected to a second heat treatment. The second heat treatment is performed in a low-oxygen atmosphere (lower oxygen concentration than the first heat treatment) at a higher temperature than the first heat treatment. Through the second heat treatment, the first metallic magnetic particles 31 and the second metallic magnetic particles 32 contained in the main body 110 are each oxidized, forming an oxide film 41 on the surface of the first metallic magnetic particles 31 and an oxide film 42 on the surface of the second metallic magnetic particles 32. The first metallic magnetic particles 31 and the second metallic magnetic particles 32 contain metal elements with a greater ionization tendency than copper. Therefore, when oxides of metal elements with a greater ionization tendency than copper are generated in the first metallic magnetic particles 31 or the second metallic magnetic particles 32 disposed near the copper oxide film 50, part or all of the copper oxide contained in the copper oxide film 50 is reduced. Since the second heat treatment is performed in a low-oxygen atmosphere, the metal elements contained in the first metallic magnetic particles 31 and the second metallic magnetic particles 32 located near the copper oxide film 50 inside the main body 110 abstract oxygen from the copper oxide to become oxides. Thus, in the second heat treatment, the copper oxide contained in the copper oxide film 50 is reduced, thereby transforming the copper oxide film 50 into an oxide layer 60. The oxide layer 60 differs from the copper oxide film 50 in that it is not primarily composed of copper oxide. In cases where only a portion of the copper oxide contained in the copper oxide film 50 is reduced through the second heat treatment, the oxide layer 60 contains the copper oxide contained in the copper oxide film 50. The oxide layer 60 contains oxides of the metal elements contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32. The oxide layer 60 may contain copper elements that were present as copper oxide prior to the second heat treatment.

[0075] As described above, when the portion of the conductor portion 125 with an insulating film on its surface embedded in the main body 110 has a spiral shape, a copper oxide film 50 exists between adjacent turns of the spiral-shaped conductor portion 125. The copper oxide contained in the copper oxide film 50 between adjacent turns of the spiral-shaped conductor portion 125 is far from the first metallic magnetic particle 31 or the second metallic magnetic particle 32, and therefore is not easily reduced by the metallic elements contained in the first metallic magnetic particle 31 or the second metallic magnetic particle 32 that have a greater tendency to ionize than copper. Therefore, in the copper oxide film 50, the region between adjacent turns of the spiral-shaped conductor portion 125 has more residual copper oxide compared to other regions adjacent to the first metallic magnetic particle 31 or the second metallic magnetic particle 32. When a metal element (e.g., Fe, Cr) containing a greater tendency to ionize than copper, present in the first metallic magnetic particle 31 or the second metallic magnetic particle 32, moves to the adjacent turns of the spiral-shaped conductor portion 125 via thermal diffusion, the copper oxide present in the adjacent turns of the spiral-shaped conductor portion 125 is also reduced by this metal element with a greater tendency to ionize than copper. That is, the copper oxide film 50 present in the adjacent turns of the spiral-shaped conductor portion 125 can be partially transformed into an oxide layer 60 by a second heat treatment.

[0076] When a suspension of zinc oxide (ZnO) is applied to the surface of the conductor portion 125 in process S1, the oxide layer 60 is formed in such a manner that it contains zinc oxide in addition to an oxide containing the metal element contained in at least one of the first metallic magnetic particles 31 and the second metallic magnetic particles 32. Using this zinc oxide, the oxide layer 60 generated in the second heat treatment can be made dense.

[0077] The second heat treatment is performed, for example, at a mixed atmosphere of nitrogen and oxygen at approximately 600–900°C for 30–120 minutes. The oxygen concentration of the mixed atmosphere is 100–2000 ppm. According to the inventors' research, if the distance between the copper oxide film 50 in the intermediate 100 and the surface of the main body 110 is 2 mm or more, then by heating the intermediate at a temperature of approximately 800°C for 60 minutes in a mixed atmosphere of nitrogen and oxygen with an oxygen concentration of 2000 ppm, all the copper oxide contained in the 0.5 μm copper oxide film 50 can be reduced.

[0078] In the case where the copper oxide film 50 contains zinc oxide, at least a portion of the zinc oxide is reduced during the second heat treatment. Since the melting point of zinc is lower than the heating temperature in the second heat treatment, the reduced zinc melts during this process. If there are voids between the copper oxide film 50 and the metallic magnetic particles 31 and / or 32, the molten zinc can move into these voids and fill at least a portion of them. Therefore, after the second heat treatment, the voids between the oxide layer 60 and the first and / or second metallic magnetic particles 31 and 32 can be reduced, thereby further suppressing the entry of atmosphere or atmospheric moisture into the embedded portion 25a when using the coil component 1.

[0079] Next, the coil conductor 25 is formed by bending the portion of the conductor 125 that protrudes from the substrate 10 along the surface of the substrate 10. The coil conductor 25 can be formed by bending the conductor portion 125. The bent portions of the conductor portion 125 are called exposed portions 25b and 25c. When using copper wire instead of the conductor portion 125, the exposed portions 25b and 25c can be formed by pressing the portion of the wire that protrudes from the substrate 10 into a plate shape and bending the plate-shaped portion. In another embodiment of the present invention, the exposed portions 25b and 25c can protrude from the mounting surface 10b to the outside of the substrate 10. In this case, even without bending the conductor portion 125, the exposed surfaces 25b and 25c can be connected to the pads 3a and 3b, respectively. That is, even without bending the conductor portion 125, the exposed surfaces 25b and 25c of the coil conductor 25 can function as external electrodes.

[0080] The coil component 1 is manufactured as described above. The manufacturing method of the coil component 1 may also include processes other than S1 to S3. For example, the substrate 10, manufactured by the heat treatment process, may be subjected to grinding treatments such as tumbling as needed. Furthermore, a portion of the processes S1 to S3 may be performed in parallel or in a different order. For example, the bending of the conductor portion 125 may be performed before the first heat treatment in process S2, or between process S2 and process S3. Additionally, the manufacturing method of the coil component 1 may include processes other than S1 to S3. For example, an external electrode may be provided on the substrate 10 using a known method. The external electrode is electrically connected to the portion of the coil conductor 25 exposed from the substrate 10.

[0081] Next, the effects of the above-described embodiments will be explained. According to one or more embodiments of the present invention, the surface of the embedded portion 25a of the coil conductor 25 is covered by an insulating oxide layer 60. Therefore, a short circuit will not occur between the coil conductor 25 and the metallic magnetic particles (e.g., first metallic magnetic particles 31 and second metallic magnetic particles 32) contained in the substrate 10. Furthermore, since the surface of the embedded portion 25a of the coil conductor 25 is covered by the oxide layer 60, the gap between the coil conductor 25 and the metallic magnetic particles constituting the substrate 10 is filled by this oxide layer 60. Therefore, it is possible to suppress the passage of air or moisture from the atmosphere through the substrate 10 to the coil conductor 25. In addition, this oxide layer 60 contains oxides of the metallic elements contained in the metallic magnetic particles; therefore, the relative permeability of the oxide layer 60 is higher than that of conventional resin-based insulating films. Therefore, in the coil component 1, the oxide layer 60 provides excellent insulation withstand voltage and oxidation resistance, and the deterioration of magnetic properties is also suppressed.

[0082] According to one or more embodiments of the present invention, by containing zinc oxide in the oxide layer 60, the oxide layer 60 can be made dense. This further suppresses the reach of the atmosphere or moisture in the atmosphere to the coil conductor 25.

[0083] The dimensions, materials, and configurations of the various components described in this specification are not limited to those explicitly described in the embodiments. These components can be modified in any size, material, and configuration that falls within the scope of this invention. Furthermore, components not explicitly described in this specification may be added to the described embodiments, or a portion of the components described in the embodiments may be omitted.

[0084] The terms "first," "second," and "third" used in this specification are added for the purpose of identifying constituent elements and do not necessarily limit their quantity, order, or content. Furthermore, the numbers used to identify constituent elements are used in each context, and a number used in one context may not represent the same constituent element in another. Moreover, this does not preclude a constituent element identified by one number from also having the function of a constituent element identified by another number.

Claims

1. A coil component, characterized in that, include: A matrix comprising multiple metallic magnetic particles, each of which contains a metallic element and each of which has an oxide film on its surface; A coil conductor with copper as its main component has an embedded portion disposed inside the substrate and an exposed portion exposed outside the substrate; and An insulating oxide layer covering the surface of the embedded portion is formed between the embedded portion and the oxide film on the surface of the metal magnetic particles adjacent to the embedded portion, and includes oxides of the metal elements contained in the plurality of metal magnetic particles and copper elements.

2. The coil component according to claim 1, characterized in that: Each of the plurality of metallic magnetic particles contains a metallic element with a greater tendency to ionize than copper.

3. The coil component according to claim 1 or 2, characterized in that: Each of the plurality of metallic magnetic particles is bonded to an adjacent metallic magnetic particle through the oxide film.

4. The coil component according to claim 1 or 2, characterized in that: A portion of the plurality of metallic magnetic particles is adjacent to the coil conductor, separated by the oxide layer and the oxide film.

5. The coil component according to claim 1 or 2, characterized in that: The oxide layer contains zinc.

6. The coil component according to claim 5, characterized in that: The zinc content in the oxide layer is higher than that in the oxide film.

7. The coil component according to claim 5, characterized in that: The atomic percentage of zinc in the oxide layer is more than 1.0 at% and less than 25 at%.

8. A circuit board, characterized in that: It includes the coil component as described in any one of claims 1 to 7.

9. An electronic device, characterized in that: Includes the circuit board as described in claim 8.

10. A method for manufacturing a coil component, characterized in that, include: The preparation process of an intermediate includes a main body and a conductor portion embedded in the main body. The main body contains a plurality of metallic magnetic particles, and the conductor portion is mainly composed of copper. In the first heating step, an oxide film containing copper oxide is formed by heating the intermediate at a first temperature to cover the surface of the conductor portion. and In the second heating step, after heating at the first temperature, the intermediate is heated at a second temperature higher than the first temperature to generate an oxide film containing oxides of the metal elements contained in each of the plurality of metallic magnetic particles, thereby forming a substrate from the main body and forming an insulating oxide layer containing the oxides and copper elements. The oxide layer is formed between the surface of the conductor portion and the oxide film formed on the surface of the metal magnetic particles adjacent to the conductor portion among the plurality of metal magnetic particles.

11. The method for manufacturing a coil component according to claim 10, characterized in that: In the second heating process, at least a portion of the copper oxide contained in the oxide film is reduced.

12. The method for manufacturing a coil component according to claim 10 or 11, characterized in that: In the second heating process, an oxide film is formed on each of the plurality of magnetic metal particles, and the plurality of magnetic metal particles are bonded to adjacent magnetic metal particles through the oxide film to form the substrate.

13. The method for manufacturing a coil component according to claim 10 or 11, characterized in that: In the second heating step, the intermediate is heated in an atmosphere with a lower oxygen concentration than in the first heating step.

14. The method for manufacturing a coil component according to claim 10 or 11, characterized in that: The conductor portion is covered by a thermally decomposable insulating film, which is decomposed during the first heating process.

15. The method for manufacturing a coil component according to claim 10 or 11, characterized in that: The preparation process includes applying a suspension containing zinc oxide to the surface of the conductor portion.

16. The method for manufacturing a coil component according to claim 15, characterized in that: In the second heating process, the oxide layer is formed in a manner that includes zinc oxide.

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