Manufacturing method of coil parts

Abstract

To provide an efficient manufacturing method of a coil component capable of removing residual stress while suppressing oxidation of a conductor formed by bending and embedded in a magnetic substrate.SOLUTION: A manufacturing method of a coil component includes a step S1 of preparing an intermediate including a conductor portion formed by bending a base material whose main component is a metal having a lower ionization tendency than iron, and an element body having a plurality of metal magnetic particles containing iron as a main component and surrounding at least a portion of the conductor portion, a first heating step S2 of heating the intermediate at first temperature to form an oxide film containing a metal oxide so as to cover the surface of the conductor portion, and a second heating step S3 of generating an oxide film containing iron oxide on the surface of each of the plurality of metal magnetic particles to form a magnetic substrate from the element body by heating the intermediate at second temperature higher than the first temperature after heating at the first temperature, and forming an insulating oxide layer containing iron oxide and metal from the oxide film to anneal the conductor portion.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a coil component. [Background technology]

[0002] JP 2019-153650 A (Patent Document 1) describes a coil component including a magnetic base and a conductor portion formed by bending a flat metal base material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP2019-153650A Summary of the Invention [Problem to be solved by the invention]

[0004] Residual stress occurs in the portion of the conductor formed by bending a flat metal substrate that has been plastically deformed by the bending process, and therefore the mechanical strength of the coil component having the conductor formed by the bending process is easily reduced.

[0005] Coil parts are sometimes used in environments where they are subjected to continuous vibration. For example, coil parts used in electrical equipment of automobiles are subjected to repeated vibration while the automobile is running. When coil parts are subjected to repeated vibration, fatigue cracks are likely to occur in the conductor parts of the coil parts that have been plastically deformed by bending.

[0006] It has been known for some time that residual stress can be removed by annealing processed products obtained by bending metal materials. The conductors used in coil components are mainly composed of metals such as copper and silver, so they need to be heated at high temperatures of 500°C or higher to remove the residual stress generated in the conductors by annealing. When heated at such high temperatures, the conductors oxidize, which can result in high electrical resistance.

[0007] In addition, depending on the material of the magnetic base in which the conductor is embedded, it may not be possible to perform annealing at high temperatures after embedding the conductor in the magnetic base. For example, the magnetic base of the coil component in the cited document 1 contains a resin binder that bonds the metal magnetic particles together. If the magnetic base is heated to a high temperature that can remove the residual stress in the conductor, the binder is thermally decomposed, and the bonds between the metal magnetic particles become weak. Thus, depending on the material that constitutes the magnetic base, it may be difficult to remove the residual stress in the conductor by annealing during the manufacturing process.

[0008] It is conceivable to manufacture coil components by preparing a metal plate from which residual stress has been removed by bending and annealing a base material made of a metal material, and then embedding the metal plate from which residual stress has been removed in a magnetic substrate. However, this requires an additional and independent heating process to remove the residual stress in the metal plate, which causes a problem of inefficiency in the manufacturing process.

[0009] It is an object of the present invention to solve or alleviate at least some of the problems described above. A more specific object of the present invention is to provide an efficient method for manufacturing a coil component that can remove residual stress while suppressing oxidation of a conductor portion formed by bending and embedded in a magnetic base.

[0010] The object of the present invention other than the above will become clear throughout the entire description of the specification. The invention described in the claims may solve problems other than those grasped from the "Problem to be solved by the invention." [Means for solving the problem]

[0011] A manufacturing method for a coil component according to one embodiment of the present invention includes a step of preparing an intermediate body including a conductor portion formed by bending a base material whose main component is a metal having a smaller ionization tendency than iron, and an element body having a plurality of metal magnetic particles whose main component is iron and surrounding at least a portion of the conductor portion; a first heating step of heating the intermediate body at a first temperature to form an oxide film containing an oxide of the metal so as to cover a surface of the conductor portion; and a second heating step of heating the intermediate body at a second temperature that is higher than the first temperature after heating at the first temperature to generate an oxide film containing iron oxide on the surface of each of the plurality of metal magnetic particles to form a magnetic base from the element body, forming an insulating oxide layer containing iron oxide and the metal from the oxide film, and annealing the conductor portion.

[0012] A manufacturing method for a coil component according to one embodiment of the present invention includes the steps of: preparing an intermediate body including a base material whose main component is a metal having a smaller ionization tendency than iron; and an element body having a plurality of metal magnetic particles whose main component is iron and surrounding at least a portion of the element body; a first heating step of heating the intermediate body at a first temperature to form an oxide film containing an oxide of the metal so as to cover a surface of the base material; a step of bending the base material after the first heating step to form a conductor portion; and a second heating step of heating the intermediate body after the bending process at a second temperature that is higher than the first temperature to generate an oxide film containing iron oxide on the surface of each of the plurality of metal magnetic particles to form a magnetic base from the element body, forming an insulating oxide layer containing iron oxide and the metal from the oxide film, and annealing the conductor portion.

[0013] In the second heating step according to one embodiment of the present invention, at least a portion of the metal oxide contained in the oxide film is reduced.

[0014] In the second heating step according to one embodiment of the present invention, each of the plurality of metal magnetic particles is bonded to adjacent metal magnetic particles via the oxide film to form the base.

[0015] In the second heating step according to one embodiment of the present invention, the intermediate body is heated in an atmosphere having a lower oxygen concentration than that in the first heating step.

[0016] In one embodiment of the present invention, the substrate is covered with a thermally decomposable insulating coating, and the insulating coating is decomposed in the first heating step.

[0017] In one embodiment of the present invention, the preparation step includes a step of applying a suspension containing zinc oxide to the surface of the substrate.

[0018] In one embodiment of the present invention, in the second heating step, the oxide layer is formed so as to contain zinc oxide.

[0019] In one embodiment of the present invention, the first temperature is in the range of 100 to 350°C.

[0020] In one embodiment of the present invention, the second temperature is in the range of 600 to 900°C.

[0021] In one embodiment of the present invention, the second heating step is carried out in an atmosphere having an oxygen concentration of 100 to 2000 ppm. Effect of the Invention

[0022] According to the invention disclosed in this specification, it is possible to provide a manufacturing method for a coil component that can remove residual stress while suppressing oxidation of a conductor portion formed by bending and embedded in a magnetic base. [Brief description of the drawings]

[0023] [Figure 1] 1 is a perspective view of a coil component according to an embodiment of the present invention mounted on a mounting board. [Diagram 2] 2 is a cross-sectional view of the coil component shown in FIG. 1 taken along line II. [Diagram 3] 3 is an enlarged cross-sectional view showing a part of the cross section of FIG. 2 in an enlarged manner. [Figure 4] FIG. 4 is a flow diagram showing a manufacturing process of the coil component according to the embodiment of the present invention. [Diagram 5] FIG. 2 is a flow diagram showing a process for preparing an intermediate in one embodiment of the present invention. [Figure 6] 1 is a perspective view showing a schematic diagram of an intermediate product produced in a manufacturing process of a coil component according to an embodiment of the present invention; [Figure 7] 1 is a perspective view showing a schematic diagram of an intermediate product produced in a manufacturing process of a coil component according to an embodiment of the present invention; [Figure 8] 4 is an enlarged cross-sectional view showing a part of a cross section of an intermediate body before heating in a first heating step in a manufacturing process of a coil component according to an embodiment of the present invention. FIG. [Figure 9] 1 is an enlarged cross-sectional view showing a portion of a cross section of an intermediate body after being heated in a first heating step and before being heated in a second heating step in a manufacturing process of a coil component according to an embodiment of the present invention. FIG. [Figure 10] FIG. 2 is a flow diagram showing a process for preparing an intermediate in one embodiment of the present invention. [Figure 11] FIG. 4 is a flow chart showing a manufacturing process of the coil component according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Various embodiments of the present invention will be described below with reference to the drawings as appropriate. Note that components common to multiple drawings are given the same reference numerals throughout the multiple drawings. Please note that the drawings are not necessarily drawn to scale for the sake of convenience. The embodiments of the present invention described below do not limit the invention according to the claims. Elements described in the following embodiments are not necessarily essential to the solution of the invention.

[0025] A coil component 1 according to an embodiment of the present invention will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view of the coil component 1 mounted on a mounting substrate 2a, Fig. 2 is a cross-sectional view of the coil component 1 cut along line II, and Fig. 3 is an enlarged cross-sectional view of a part of the cross-section shown in Fig. 2. Each of Figs. 1 and 2 shows a W-axis, an L-axis, and a Z-axis that are orthogonal to each other. In this specification, unless otherwise understood in the context, the "length" direction, the "width" direction, and the "thickness" direction of the coil component 1 are respectively the "L-axis" direction, the "W-axis" direction, and the "T-axis" direction in Fig. 1. In this specification, the orientation and arrangement of the components of the coil component 1 may be described based on the L-axis, W-axis, and Z-axis directions.

[0026] The coil component 1 can be applied to inductors, transformers, filters, reactors, and various other coil components. The coil component 1 can also be applied to coupled inductors, choke coils, and various other magnetically coupled coil components. Applications of the coil component 1 are not limited to those explicitly described in this specification.

[0027] As shown in Figures 1 and 3, the coil component 1 includes a magnetic base 10 formed from a magnetic material, a conductor portion 25 provided on the magnetic base 10, and an oxide layer 60 provided between the conductor portion 25 and the magnetic base 10.

[0028] The coil component 1 is mounted on a mounting board 2a. The mounting board 2a is provided with land portions 3a and 3b. The coil component 1 is mounted on the mounting board 2a by joining the exposed portion 25b of the conductor portion 25 to the land portion 3a and by joining the exposed portion 25c of the conductor portion 25 to the land portion 3b. In this manner, the circuit board 2 includes the coil component 1 and the mounting board 2a on which the coil component 1 is mounted. The circuit board 2 can include the coil component 1 and various electronic components other than the coil component 1.

[0029] The circuit board 2 can be mounted on various electronic devices. Examples of electronic devices in which the circuit board 2 can be mounted include smartphones, tablets, game consoles, automotive electrical components, servers, and various other electronic devices. The electronic devices in which the coil component 1 is mounted are not limited to those explicitly stated in this specification. The coil component 1 may be an internal component embedded inside the circuit board 2.

[0030] In the illustrated embodiment, the magnetic base 10 has a generally rectangular parallelepiped shape. The magnetic base 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 is defined by these six surfaces. The first main surface 10a and the second main surface 10b face each other, the first end surface 10c and the second end surface 10d face each other, and the first side surface 10e and the second side surface 10f face each other. In FIG. 1, the first main surface 10a is located on the upper side of the main body 10, so the first main surface 10a may be referred to as the "upper surface". Similarly, the second main surface 10b may be referred to as the "lower surface". The magnetically coupled coil component 1 is disposed so that the second main surface 10b faces the mounting board 2a, so the second main surface 10b may be referred to as the "mounting surface". The up-down direction of the coil component 1 is referred to based on the up-down direction in Fig. 1. In this specification, unless otherwise understood in the context, the "length" direction, "width" direction, and "thickness" direction of the coil component 1 are respectively the "L-axis" direction, "W-axis" direction, and "T-axis" direction in Fig. 1. The L-axis, W-axis, and T-axis are perpendicular to each other.

[0031] In one or more embodiments of the present invention, the coil component 1 is formed so that the length dimension (dimension in the L axis direction) of the magnetic base 10 is 1.0 to 12.0 mm, the width dimension (dimension in the W axis direction) is 1.0 to 12.0 mm, and the height dimension (dimension in the T axis direction) is 1.0 to 6.0 mm. The coil component 1 may be formed so that the length dimension (dimension in the L axis direction) is 0.2 to 6.0 mm, the width dimension (dimension in the W axis direction) is 0.1 to 4.5 mm, and the height dimension (dimension in the T axis direction) is 0.1 to 4.0 mm. These dimensions are merely examples, and the coil component 1 to which the present invention can be applied may have any dimensions as long as they are not contrary to the spirit of the present invention.

[0032] The magnetic substrate 10 is made of a magnetic material. In one or more embodiments of the present invention, the magnetic substrate 10 includes a plurality of metal magnetic particles. The metal magnetic particles are particles or powders made of a soft magnetic metal material. The metal magnetic particles include a metal element having a greater ionization tendency than copper. The metal magnetic particles are, for example, powders of an Fe-Cr-Si alloy. Fe and Cr have a greater ionization tendency than copper (Cu). The soft magnetic metal material for the metal magnetic particles is not limited to an Fe-Cr-Si alloy. The soft magnetic metal material for the metal magnetic particles is, for example, (1) alloy Fe-Si-Al or Fe-Ni, (2) amorphous Fe-Si-Cr-BC or Fe-Si-B-Cr, or (3) particles of a mixed material thereof. When the metal magnetic particles are made of an alloy material, the Fe content in the metal magnetic particles may be 80 wt% or more and less than 97 wt%. When the metal magnetic particles are made of an amorphous material, the Fe content in the metal magnetic particles may be 72 wt% or more and less than 85 wt%. The total content of metal elements that are more easily oxidized than Si and copper in the metal magnetic particles may be 3 wt% or more, 8 wt% or more, or 10 wt% or more.

[0033] In one or more embodiments of the present invention, the particle size of the metal magnetic particles contained in the magnetic base 10 is distributed according to a predetermined particle size distribution. The metal magnetic particles have an average particle size of, for example, 1 μm or more and 10 μm or less. The average particle size of the metal magnetic particles contained in the magnetic base 10 is determined based on the particle size distribution obtained by cutting the magnetic base 10 along its thickness direction (T-axis direction) to expose a cross section, and taking an SEM photograph of the cross section at a magnification of 1000 times to 5000 times with a scanning electron microscope (SEM). For example, the 50% value of the particle size distribution obtained based on the SEM photograph can be set as the average particle size of the metal magnetic particles. The magnetic base 10 may be composed of one type of metal magnetic particles, or may be composed of two or more types of metal magnetic particles that are different from each other in terms of material and / or average particle size. When the magnetic base 10 is composed of two or more types of metal magnetic particles, the two or more types of metal magnetic particles may be composed of different soft magnetic metal materials. For example, the magnetic base 10 may be a mixed particle of a metal magnetic particle made of an Fe-Cr-Si alloy and a metal magnetic particle made of an Fe-Ni alloy. When the magnetic base 10 is composed of two or more kinds of metal magnetic particles, the two or more kinds of metal magnetic particles may have different average particle sizes. The fact that the magnetic base 10 contains mixed particles of two or more kinds of metal magnetic particles having different average particle sizes can be confirmed by two or more peaks appearing in the particle size distribution when the particle size distribution is created based on an SEM photograph.

[0034] The conductor portion 25 includes an embedded portion 25a disposed inside the magnetic base 10, an exposed portion 25b connected to one end of the embedded portion 25a and extending along the first end face 10c of the magnetic base 10, an exposed portion 25c connected to the other end of the embedded portion 25a and extending along the second end face 10d of the magnetic base 10, a connection portion 25d connected to the exposed portion 25b and extending along the lower face 10b of the magnetic base 10, and a connection portion 25e connected to the exposed portion 25c and extending along the lower face 10b of the magnetic base 10. The connection portions 25d and 25e extend along the lower face 10b of the magnetic base 10, and are connected to the lands 3a and 3b, respectively, when the coil component 1 is mounted on the mounting board 2a.

[0035] Conductor 25 is formed, for example, by bending a metal flat or linear base material. Conductor 25 has curved portions 25f at the boundary between embedded portion 25a and exposed portion 25b, the boundary between embedded portion 25a and exposed portion 25c, the boundary between exposed portion 25b and connecting portion 25d, and the boundary between exposed portion 25c and connecting portion 25e. Curved portions 25f may be formed by bending the base material.

[0036] The conductor portion 25 applicable to the present invention is not limited to the illustrated embodiment. The exposed portions 25b and 25c can have any shape as long as they are exposed from the magnetic base 10, and can be disposed at any position relative to the magnetic base 10. The conductor portion 25 does not need to include the connecting portions 25d and 25e. When the exposed portions 25b and 25c do not extend to the mounting surface 10b or when the conductor portion 25 does not include the connecting portions 25d and 25e, the coil component 1 may include two external electrodes connected to the exposed portions 25b and 25c, respectively. As the external electrodes, known external electrodes may be applied. The external electrodes are obtained, for example, by applying a conductive paste to the surface of the magnetic base 10 to form a base electrode, and forming one or more plating layers on the surface of the base electrode. When the conductor portion 25 does not include the connecting portions 25d and 25e, the exposed portions 25b and 25c may be directly or indirectly connected to the lands 3a and 3b of the mounting board 2a, respectively.

[0037] The conductor part 25 is a conductive structure mainly composed of a metal having a smaller ionization tendency than iron. In this specification, the main component refers to the component having the largest content ratio on a mass basis. In this specification, the metal that is the main component of the metal material constituting the conductor part 25 is referred to as the "main component metal of the conductor part 25" or simply as the "main component metal". Examples of the main component metal of the conductor part 25 are copper and silver. Therefore, when the main component of the conductor part 25 is copper, the content ratio of copper on a mass basis is the highest. In order to reduce the electrical resistance, the content ratio of copper or silver in the conductor part 25 may be 90 wt% or more, 95 wt% or more, 99 wt% or more, or a higher content ratio than that. The conductor part 25 may contain Ni, Sn, Zn, and / or other elements in addition to the main component metal.

[0038] The shape of the conductor 25 applicable to the present invention is not limited to the shape shown in the figure. The embedded portion 25a of the conductor 25 may have a spiral shape. The embedded portion 25a having a spiral shape may extend in a spiral shape around an axis line that passes through the intersection of the diagonals of the first main surface 10a having a rectangular shape in a plan view and extends in a direction perpendicular to the first main surface 10a (T-axis direction). The shapes of the exposed portions 25b, 25c and / or the connecting portions 25d, 25e can also be modified from the shapes shown in the figures. In the illustrated conductor 25, the embedded portion 25a and the exposed portions 25b, 25c have the same cross-sectional shape. In the conductor 25, the embedded portion 25a may have a circular or elliptical cross-section. The conductor 25 may be a straight wire rod with a wire diameter of 1.5 mm. The exposed portions 25b, 25c may be formed by pressing such a wire rod. The exposed portions 25b and 25c may be formed to have a thickness in the range of, for example, 0.1 mm to 0.5 mm.

[0039] When the embedded portion 25a has a helical shape, the embedded portion 25a extends around the coil axis. The embedded portion 25a having a helical shape may be wound around the coil axis for a plurality of turns. The coil axis may be a virtual axis line extending along any one of the T-axis, the L-axis, or the W-axis. A part of the magnetic base 10 may be interposed between adjacent turns of the embedded portion 25a wound around the coil axis for a plurality of turns. An insulating material mainly composed of an oxide of a metal that is the main component of the conductor portion 25 may be interposed between adjacent turns of the embedded portion 25a wound around the coil axis for a plurality of turns.

[0040] Next, the microscopic structure near the boundary between the magnetic base 10 and the embedded portion 25a of the conductor 25 will be described with reference to FIG. 3. FIG. 3 is an enlarged cross-sectional view of a region A in the cross section of the coil component 1 shown in FIG. 2. Region A is a region that straddles the embedded portion 25a of the conductor 25 and the magnetic base 10. In the example shown in FIG. 3, the magnetic base 10 contains two types of metal magnetic particles having different average particle sizes, specifically, a plurality of first metal magnetic particles 31 and a plurality of second metal magnetic particles 32 having an average particle size smaller than that of the first metal magnetic particles 31. The first metal magnetic particles 31 and the second metal magnetic particles 32 are formed of a soft magnetic metal material mainly composed of iron. The first metal magnetic particles 31 and the second metal magnetic particles 32 may be, for example, (1) alloy-based Fe-Si-Cr, Fe-Si-Al or Fe-Ni particles, (2) amorphous Fe-Si-Cr-BC or Fe-Si-B-Cr particles, or (3) particles of a mixed material of these.

[0041] The surfaces of the metal magnetic particles contained in the magnetic substrate 10 are provided with insulating oxide films containing oxides of the metal elements contained in the metal magnetic particles. As shown in FIG. 3, the surfaces of the first metal magnetic particles 31 are provided with oxide films 41, and the surfaces of the second metal magnetic particles 32 are provided with oxide films 42. The oxide films 41 and 42 contain oxides of Fe. The oxide films 41 and 42 may contain oxides of elements constituting the metal magnetic particles other than Fe. For example, when the metal magnetic particles are made of an Fe-Cr-Si alloy, the oxide films on the surfaces contain oxides of Fe, Cr, and Si. The first metal magnetic particles 31 are bonded to the adjacent first metal magnetic particles 31 or second metal magnetic particles 32 via the oxide films 41 and / or oxide films 42.

[0042] Between the embedded portion 25a of the conductor portion 25 and the first and second metal magnetic particles 31 and 32, an oxide layer 60 is disposed, covering the surface of the embedded portion 25a. The oxide layer 60 may be in contact with the embedded portion 25a. The oxide layer 60 is provided between the embedded portion 25a and the first and second metal magnetic particles 31 and 32 so as to close the space between the embedded portion 25a and the first and second metal magnetic particles 31 and 32. The oxide layer 60 is in contact with the first metal magnetic particle 31 via the oxide film 41, and is in contact with the second metal magnetic particle 32 via the oxide film 42. A gap may be present between the oxide layer 60 and the first metal magnetic particle 31 and / or the second metal magnetic particle 32.

[0043] As shown in the figure, the oxide layer 60 may cover the entire surface area of ​​the embedded portion 25a. For example, the magnetic base 10 is cut along the T axis to expose a cross section, and SEM photographs of the cross section are taken at a magnification of 5000 times so that a part of the surface of the embedded portion 25a and the magnetic base 10 are included in the field of view at each of three points (which may be five or more points) arranged at equal intervals in the L axis direction. When the entire surface of the embedded portion 25a is covered with the oxide layer 60 in each of the taken SEM photographs, 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 conductor portion 25 is covered with the oxide layer 60, and the oxide layer 60 blocks the space between the embedded portion 25a and the first metal magnetic particles 31 and the second metal magnetic particles 32, so that the atmosphere in the usage environment and moisture in the atmosphere can be prevented or suppressed from reaching the embedded portion 25a through the magnetic base 10 during use of the coil component 1.

[0044] In one or more embodiments of the present invention, the oxide layer 60 can contain iron oxide and an oxide of a metal element other than iron contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32. For example, when the first metal magnetic particles 31 and the second metal magnetic particles 32 are made of an Fe-Cr-Si alloy, the oxide layer 60 can contain oxides of Fe and Cr. Since the oxide layer 60 contains an oxide of a metal element contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32, the relative magnetic permeability of the oxide layer 60 becomes higher than the relative magnetic permeability of a conventional insulating coating made of resin (e.g., made of polyimide).

[0045] In one or more embodiments of the present invention, the oxide layer 60 may contain an element of a main component metal of the conductor portion 25, such as an element of copper or element of silver, in addition to iron oxide and an oxide of a metal element other than Fe contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32. The elemental copper may be present in the oxide layer 60 as copper oxide, and the elemental silver may be present in the oxide layer 60 as silver oxide.

[0046] In an SEM photograph of the cross section of the magnetic substrate 10 taken at a magnification of 5000 to 20000 times, the boundary between the oxide layer 60 and the embedded portion 25a of the conductor portion 25, and the boundary between the oxide layer 60 and the first metal magnetic particle 31 and the second metal magnetic particle 32 can be identified by the difference in brightness. It can be confirmed that the oxide layer 60 contains an oxide of a metal element contained in at least one of the first metal magnetic particle 31 and the second metal magnetic particle 32 by performing energy dispersive X-ray analysis (EDS) on the cross section of the magnetic substrate 10. Specifically, if it can be confirmed by EDS analysis of the cross section of the magnetic substrate 10 that the oxide layer 60 contains a metal element and an oxygen element contained in at least one of the first metal magnetic particle 31 and the second metal magnetic particle 32, it can be confirmed that the oxide layer 60 contains an oxide of a metal element contained in at least one of the first metal magnetic particle 31 and the second metal magnetic particle 32. When mapping data of each element obtained by EDS analysis of the cross section of the magnetic substrate 10 is reconstructed along a line (for example, a line extending along the T-axis direction) that crosses the oxide layer 60, the count number of the metal element contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32 in this scanning line may increase with distance from the embedded portion 25a (closer to the first metal magnetic particles 31 and the second metal magnetic particles 32). In other words, the detection intensity of the metal element contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32 may increase with distance from the embedded portion 25a. On the other hand, the detection intensity of the main component metal of the conductor portion 25 in the same scanning line may increase with distance from the embedded portion 25a.

[0047] The oxide layer 60 has excellent insulating properties. The oxide layer 60 exhibits excellent insulating properties because it contains hematite, silicon dioxide, and / or other insulating oxides. The oxide layer 60 is, for example, 10 8 It has a high resistivity of Ω·cm or more. Since the surface of embedded portion 25a of conductor portion 25 is covered with insulating oxide layer 60 in this manner, it is possible to suppress the occurrence of short circuits between conductor portion 25 and first metal magnetic particles 31 and second metal magnetic particles 32. In other words, coil device 1 has excellent dielectric strength.

[0048] As described above, when the embedded portion 25a has a spiral shape, a part of the magnetic base 10 may be interposed between adjacent turns of the embedded portion 25a. In this case, an oxide layer 60 is provided between the area of ​​the magnetic base 10 interposed between the adjacent turns of the embedded portion 25a and the surface of the embedded portion 25a. Since the adjacent turns are thus separated by the insulating oxide layer 60, it is possible to suppress the occurrence of a short circuit between the portions constituting the different turns of the conductor portion 25. Therefore, the coil component 1 has an excellent dielectric strength.

[0049] When the embedded portion 25a has a spiral shape, an insulating material mainly composed of the main component metal of the conductor portion 25 may be interposed between adjacent turns of the embedded portion 25a, instead of the magnetic base 10. This insulating material mainly composed of the main component metal of the conductor portion 25 can suppress the occurrence of a short circuit between the portions constituting the different turns of the conductor portion 25.

[0050] In one or more embodiments of the present invention, the oxide layer 60 contains elemental zinc. The elemental zinc may be contained in the oxide layer 60 as zinc oxide. The oxide layer 60 contains elemental zinc at a ratio of, for example, 1.0 at% to 25 at%. The elemental zinc may also be contained in at least one of the oxide film 41 of the first metal magnetic particle 31 and the oxide film 42 of the second metal magnetic particle 32. In one or more embodiments, the content ratio (atomic ratio) of elemental zinc in the oxide layer 60 is higher than the content ratio (atomic ratio) of elemental zinc in the oxide film 41 and the content ratio (atomic ratio) of elemental zinc in the oxide film 42. By containing zinc oxide in the oxide layer 60, the oxide layer 60 can be made dense. This can further prevent oxygen and moisture in the air from reaching the embedded portion 25a during use of the coil component 1.

[0051] Next, an exemplary manufacturing method of the coil component 1 according to one embodiment of the present invention will be described with reference to Fig. 4 to Fig. 9. Fig. 4 is a flow diagram showing a manufacturing process of the 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 a compression molding method. The coil component 1 may be manufactured by a method other than the compression molding method.

[0052] First, in step S1, the intermediate body 100 is prepared. The process flow for preparing the intermediate body 100 is shown in FIG. 5, and a schematic diagram of the intermediate body 100 is shown in FIG. 6. As shown in FIG. 6, the intermediate body 100 has an element body 110 made of a magnetic material and a metal base material 125 partially embedded in the element body 110. The base material 125 is made of a metal material mainly composed of a metal having a smaller ionization tendency than iron. In this specification, the metal that is the main component of the metal material constituting the base material 125 is referred to as the "main component metal of the base material 125". As will be described later, the conductor portion 25 is formed by bending the base material 125, so the main component metal of the base material 125 may be the same as the main component metal of the conductor portion 25. In the illustrated embodiment, the base material 125 is a metal flat plate. A resin insulating coating may or may not be provided on the surface of the base material 125. A suspension of zinc oxide (ZnO) powder dispersed in alcohol may be applied to the surface of the base material 125 in the area to be embedded in the element body 110. The shape of the base material 125 is not limited to a flat plate. The base material 125 may be configured in a linear shape.

[0053] 5, in order to produce the intermediate body 100, first, in step S11, a metal base material 125 is prepared. Next, in step S12, the base material 125 is embedded in the element body 110. For example, the base material 125 is placed in a molding die, a metal magnetic paste containing metal magnetic particles is placed in the molding die in which the base material 125 is placed, and a predetermined molding pressure (for example, 500 kN to 5000 kN) is applied to the metal magnetic paste in the molding die, whereby the metal magnetic paste is molded into the element body 110, and a part of the base material 125 is embedded in the element body 110. In one embodiment, the apparent density of the element body 110 is 6.0 g / cm3 The molding pressure is adjusted so that the metal magnetic paste is obtained by kneading metal magnetic particles such as Fe-Cr-Si alloy powder with a binder resin and a solvent. The metal magnetic particles may contain multiple types of metal magnetic particles having different particle sizes. The binder resin is, for example, an acrylic resin or other known resin.

[0054] Next, in step S13, the portion of the substrate 125 exposed from the element body 110 is bent along the surface of the magnetic base 10 to form the conductor 25 having the curved portion 25f as shown in Fig. 7. The conductor 25 is bent at the curved portion 25f. When a linear wire material is used as the substrate 125 instead of a flat plate material, the portion of the wire material exposed from the element body 110 may be pressed into a plate shape, and the plate-shaped portion may be bent to form the conductor 25. In this manner, the intermediate body 100 is produced.

[0055] FIG. 8 shows an enlarged view of a part of a cross section of the intermediate body 100 produced in step S1 cut along the T axis. The area shown in FIG. 8 corresponds to area A in FIG. 2. As shown in FIG. 8, the element body 110 includes a plurality of first metal magnetic particles 31 and second metal magnetic particles 32 having an average particle size smaller than that of the first metal magnetic particles 31. A binder resin 45 is filled in the gaps between adjacent metal magnetic particles and between the conductor portion 25 and the metal magnetic particles. In the illustrated embodiment, the conductor portion 25 does not have a resin insulating coating, and is therefore in contact with the first metal magnetic particles 31 and the second metal magnetic particles 32 directly or via the binder resin 45. As described above, the surface of the conductor portion 25 may be covered with an insulating coating made of a thermally decomposable resin. In this case, the conductor portion 25 is in contact with the first metal magnetic particles 31 and the second metal magnetic particles 32 via a resin insulating coating, or via a resin insulating coating and the binder resin 45.

[0056] Next, in step S2, a first heating process is performed on the intermediate 100 produced in step S1. Specifically, the intermediate 100 is placed in a heating furnace and heated in the furnace in an air atmosphere or an oxygen atmosphere at, for example, 100 to 350° C. for 30 to 120 minutes. This first heating process decomposes the binder resin 45, and a metal oxide film 50 containing an oxide of the main component metal of the conductor 25 (e.g., copper oxide or silver oxide) is formed on the surface of the portion of the conductor 25 that is embedded in the element body 110. If the surface of the conductor 25 is covered with an insulating coating made of a thermally decomposable resin, in the first heating process, the intermediate 100 is heated to a temperature equal to or higher than the thermal decomposition temperature of the resin that constitutes the insulating coating on the surface of the conductor 25. Therefore, the insulating coating on the surface of the conductor 25 is thermally decomposed in the first heating process, and a metal oxide film 50 containing the main component metal of the conductor 25 is formed on the surface of the portion of the conductor 25 that is embedded in the element body 110. In this way, when the conductor 25 is covered with a resin insulating coating, the area around the conductor 25 where the resin insulating coating existed before the first heat treatment does not become a void, but is blocked by the metal oxide film 50. Since the first heat treatment is performed in an oxygen atmosphere, the oxidation of the main component metal contained in the conductor 25 is promoted in the first heat treatment, and the metal oxide film 50 is formed on the surface of the conductor 25 so as to block the void created by the decomposition of the resin insulating coating and the binder resin 45.

[0057] As described above, the portion of the conductor 25 embedded in the element body 110 may have a spiral shape. When the portion of the conductor 25 having an insulating coating on its surface embedded in the element body 110 has a spiral shape, the insulating coating is thermally decomposed by the first heat treatment, and the space occupied by the insulating coating before the thermal decomposition is filled with an oxide (e.g., copper oxide or silver oxide) generated by oxidation of the oxide of the main component metal of the conductor 25. In other words, when the conductor 25 having an insulating coating is embedded in the element body 110, the metal oxide film 50 is also provided between adjacent turns of the conductor 25 having a spiral shape. The metal oxide film 50 interposed between the adjacent turns suppresses the occurrence of a short circuit between the adjacent turns of the conductor 25.

[0058] In this way, the first heating treatment degreases (debinders) element body 110, and oxidizes the surfaces of conductor parts 25. The heating conditions in the first heating treatment may be appropriately adjusted so that metal oxide film 50 has a thickness of 0.1 μm or more. The heating conditions in the first heating treatment are set so that the metal magnetic particles contained in element body 110 are not oxidized to form an oxide film on their surfaces. When the heating temperature in the first heating treatment is set to 100 to 350° C., first metal magnetic particles 31 and second metal magnetic particles 32 are made of a material that does not form an oxide film on its surface at a heating temperature of 100 to 350° C.

[0059] When a zinc oxide (ZnO) suspension is applied to the surface of the conductor portion 25 in step S1, when a metal oxide film 50 is formed on the surface of the conductor portion 25, the zinc oxide that was present on the surface of the conductor portion 25 is incorporated into the metal oxide film 50.

[0060] FIG. 9 shows an enlarged view of a part of a cross section of the intermediate body 100 after the first heat treatment in step S2, cut along the T-axis. As shown in the figure, the binder resin is decomposed in the first heat treatment, and the gaps between adjacent metal magnetic particles in the region filled with the binder resin 45 before the first heat treatment become voids 55. On the other hand, the binder resin 45 filled between the conductor portion 25 and the metal magnetic particles is also decomposed, but the gaps between the conductor portion 25 and the metal magnetic particles do not become voids and are blocked by a metal oxide film 50. Since the first heat treatment is performed in the air or in an oxygen atmosphere, the oxidation of the main component metal contained in the conductor portion 25 is promoted in the first heat treatment, and a metal oxide film 50 is formed on the surface of the conductor portion 25 so as to block the voids formed by the decomposition of the binder resin 45. The metal oxide film 50 may be formed so as to cover the entire region of the surface of the conductor portion 25 that is in contact with the element body 110.

[0061] Next, in step S3, a second heat treatment is performed on the intermediate body 100 that has been subjected to the first heat treatment. The second heat treatment is performed in a low-oxygen concentration atmosphere with a lower oxygen concentration than the first heat treatment, at a higher temperature than the first heat treatment. The second heat treatment oxidizes each of the first metal magnetic particles 31 and the second metal magnetic particles 32 contained in the element body 110, forming oxide coatings 41 on the surfaces of the first metal magnetic particles 31 and oxide coatings 42 on the surfaces of the second metal magnetic particles 32.

[0062] Since the first metal magnetic particles 31 and the second metal magnetic particles 32 contain metal elements having a higher ionization tendency than the main metal of the conductor 25, when oxides of Fe or oxides of metal elements other than Fe having a higher ionization tendency than the main metal of the conductor 25 are generated in the first metal magnetic particles 31 or the second metal magnetic particles 32 arranged in the vicinity of the metal oxide film 50, part or all of the oxide of the main metal of the conductor 25 contained in the metal oxide film 50 is reduced. Since the second heat treatment is performed in a low oxygen concentration atmosphere, the metal elements contained in the first metal magnetic particles 31 and the second metal magnetic particles 32 in the vicinity of the metal oxide film 50 inside the element 110 take oxygen from the oxide of the main metal of the conductor 25 to become oxides. In other words, at least a part of the oxygen required for oxidation is supplied from the metal oxide film 50, not from the atmosphere, to the first metal magnetic particles 31 and the second metal magnetic particles 32 that are in the vicinity of the conductor 25. In this way, in the second heat treatment, the oxide of the main component metal of the conductor 25 contained in the metal oxide film 50 is reduced, and the oxide layer 60 is formed from the metal oxide film 50. Since the oxide layer 60 is formed by reducing the oxide contained in the metal oxide film 50, it is not necessary that the main component is the oxide of the main component metal of the conductor 25. When only a part of the oxide of the main component metal of the conductor 25 contained in the metal oxide film 50 is reduced by the second heat treatment, the oxide layer 60 contains the oxide of the main component metal of the conductor 25 contained in the metal oxide film 50. The oxide layer 60 may contain an oxide of Fe and a metal element other than Fe contained in at least one of the first metal magnetic particles 31 and the second metal magnetic particles 32. The oxide layer 60 may contain an element of the main component metal of the conductor 25 that existed as an oxide before the second heat treatment.

[0063] As described above, the portion of the conductor 25 having an insulating coating on its surface that is embedded in the element 110 may be formed in a spiral shape. In this case, in the intermediate body 100 before the second heat treatment, the metal oxide film 50 is interposed between adjacent turns of the conductor 25 having this spiral shape. The main component metal of the conductor 25 contained in the metal oxide film 50 interposed between adjacent turns of the conductor 25 having this spiral shape is not easily reduced by Fe or metal elements other than Fe contained in the first metal magnetic particle 31 or the second metal magnetic particle 32 because of the large distance between the metal oxide film 50 and the first metal magnetic particle 31 or the second metal magnetic particle 32. Therefore, in the region of the metal oxide film 50 interposed between adjacent turns of the conductor 25 having a spiral shape, a relatively large amount of oxide of the main component metal of the conductor 25 remains compared to other regions adjacent to the first metal magnetic particle 31 or the second metal magnetic particle 32. When a metal element (e.g., Fe or Cr) having a greater ionization tendency than the main component metal of conductor 25 contained in first metal magnetic particle 31 or second metal magnetic particle 32 moves to between adjacent turns of helical conductor 25 by thermal diffusion, the main component metal of conductor 25 present between adjacent turns of helical conductor 25 can also be reduced by the metal element having a greater ionization tendency than the main component metal of conductor 25. For this reason, metal oxide film 50 interposed between adjacent turns of helical conductor 25 may be partially turned into oxide layer 60 by the second heat treatment.

[0064] When a suspension of zinc oxide (ZnO) is applied to the surface of conductor portion 25 in step S1, oxide layer 60 is formed so as to contain zinc oxide in addition to an oxide of a metal element contained in at least one of first metal magnetic particles 31 and second metal magnetic particles 32. This zinc oxide can densify oxide layer 60 generated in the second heat treatment.

[0065] The second heat treatment is performed, for example, for 30 to 120 minutes in a mixed atmosphere of nitrogen and oxygen at about 600 to 900°C. The oxygen concentration of the mixed atmosphere is 100 to 2000 ppm. As described in the specification of the applicant's Japanese Patent Application No. 2020-216302 (filed on December 25, 2020), it has been found that if the distance between the metal oxide film 50 and the surface of the element body 110 in the intermediate body 100 is 2 mm or more, the main component metal of the conductor portion 25 contained in the 0.5 μm metal oxide film 50 is all reduced by heating the intermediate body 100 at a temperature of about 800°C for 60 minutes in a mixed atmosphere of nitrogen and oxygen with an oxygen concentration of 2000 ppm.

[0066] By setting the heating temperature in the second heat treatment to the range of 600 to 900°C, the conductor 25 can be annealed. Before the second heat treatment, residual stress occurs in the curved portion 25f of the conductor 25 due to the bending process when the conductor 25 is formed from the base material 125. The conductor 25 is annealed by the second heat treatment, and the residual stress caused by the bending process is removed. In this manner, in the second heat treatment, not only are the oxide films 41, 42 formed on the surfaces of the metal magnetic particles 31, 32 to form the magnetic base 10 from the element body 110, and the oxide layer 60 is formed from the metal oxide film 50, but the residual stress is also removed from the conductor 25. In other words, the residual stress can be removed from the conductor 25 by the heat treatment for oxidizing the metal magnetic particles contained in the element body 110 to form the magnetic base 10.

[0067] When zinc oxide is contained in the metal oxide film 50, at least a part of the zinc oxide is reduced in 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 in the second heat treatment. When there are gaps between the metal oxide film 50 and the metal magnetic particles 31 and / or the metal magnetic particles 32, the molten zinc can move to the gaps and fill at least a part of the gaps. This can reduce the gaps between the oxide layer 60 and the first metal magnetic particles 31 and / or the second metal magnetic particles 32 after the second heat treatment, so that the air or moisture in the air can be further prevented from reaching the embedded portion 25a when the coil component 1 is used.

[0068] In this manner, the coil component 1 is manufactured. The manufacturing method of the coil component 1 may include additional steps other than steps S1 to S3. For example, the magnetic base 10 manufactured by the heat treatment step is subjected to a polishing process such as barrel polishing as necessary.

[0069] The manufacturing method of the coil component 1 described with reference to Figs. 4 and 5 can be modified in various ways. For example, in the manufacturing method of the coil component 1, the process for preparing the intermediate body 100 in step S1 can be modified as appropriate. Fig. 10 shows a modified example of the process for preparing the intermediate body 100 in step S1. As shown in Fig. 10, the intermediate body 100 may be produced by bending the base material 125 prepared in step S11a in step S12a to form the conductor portion 25, and then embedding the conductor portion 25 in the element body 110 in step S13a. In this way, the bending process on the base material 125 may be performed before embedding the base material 125 in the base material 110.

[0070] In addition, the order of the bending process and other processes on the base material 125 can be changed as appropriate. The bending process on the base material 125 may be performed at any time before the second heat treatment. FIG. 11 shows the flow of a manufacturing method according to another embodiment of the present invention in which the timing of the bending process is changed. In the manufacturing method shown in FIG. 11, the bending process on the base material 125 is performed after the first heat treatment on the intermediate body 100. FIG. 11 shows a manufacturing method of the coil component 1 in another embodiment of the present invention. In FIG. 11, the bending process on the base material 125 is performed after the first heat treatment. Specifically, first, in step S101, an intermediate body 100 having an element body 110 made of a magnetic material and a metal base material 125 partially embedded in the element body 110 is prepared. The process of step S101 is performed in the same manner as the process of step S1, by placing the base material 125 in a molding die, putting a metal magnetic paste containing metal magnetic particles into the molding die in which the base material 125 is placed, and applying a predetermined molding pressure to the metal magnetic paste in the molding die. In step S101, as shown in FIG. 6, an intermediate body 100 is produced, which includes an element body 110 and a metal substrate 125 partially embedded in the element body 110.

[0071] Next, in step S102, a first heating process is performed on the intermediate 100 produced in step S101. The first heating process in step S102 may be performed under the same conditions as the first heating process in step S2. Specifically, the intermediate 100 produced in step S101 is placed in a heating furnace and heated in the heating furnace, for example, at 100 to 350° C. in an air atmosphere or an oxygen atmosphere for 30 to 120 minutes. By the first heating process in step S102, the binder resin 45 is decomposed, and a metal oxide film 50 containing an oxide of a metal (copper oxide or silver oxide) that is a main component of the metal material constituting the substrate 125 is formed on the surface of the portion of the substrate 125 that is embedded in the element body 110.

[0072] Next, in step S103, the base material 125 included in the intermediate body 100 that has been subjected to the first heat treatment is bent to produce the conductor 25. Through this bending process, the base material 125 becomes the conductor 25 having the curved portion 25f, as shown in FIG.

[0073] Next, in step S103, a second heat treatment is performed on the intermediate 100 having the conductor 25 formed by bending. The second heat treatment in step S103 may be performed under the same conditions as the second heat treatment in step S3. Specifically, the intermediate 100, in which the substrate 125 has been bent in step S102, is heat treated at a higher temperature (e.g., about 600 to 900° C.) than that in the first heat treatment in a low-oxygen concentration atmosphere having a lower oxygen concentration (e.g., an oxygen concentration of 100 to 2000 ppm) than that in the first heat treatment. The second heat treatment oxidizes each of the first metal magnetic particles 31 and the second metal magnetic particles 32 contained in the element 110, forming an oxide film 41 on the surface of the first metal magnetic particle 31 and an oxide film 42 on the surface of the second metal magnetic particle 32, thereby producing the magnetic base 10. In the second heat treatment, the oxide of the main component metal of the conductor portion 25 contained in the metal oxide film 50 is reduced, so that the oxide layer 60 is formed from the metal oxide film 50.

[0074] In step S104, the conductor 25 can be annealed in parallel with the generation of the magnetic base 10 and the oxide layer 60. Before the second heat treatment, residual stress is generated in the curved portion 25f of the conductor 25 due to the bending process performed when forming the conductor 25 from the base material 125. Since the conductor 25 can be annealed by the second heat treatment in step S104, the residual stress can be removed from the conductor 25.

[0075] Next, the effects of the above embodiment will be described. According to the embodiment of the present invention, the conductor 25 formed by bending can be annealed by the second heating step at the second temperature, and this can remove residual stress from the conductor 25. This can increase the mechanical strength of the coil component 1.

[0076] According to an embodiment of the present invention, in the second heating step, the annealing treatment of the conductor 25 and the treatment of forming the magnetic base 10 from the element body 110 by oxidizing the first metal magnetic particles 31 and the second metal magnetic particles 32 also proceed in parallel. If the annealing treatment of the conductor 25 is performed separately from the heating step of forming the magnetic base 10 from the element body 110, an independent heating step for the annealing treatment is added, so that the manufacturing process of the coil component 1 becomes complicated and more energy is required for manufacturing the coil component 1. Furthermore, if heating is performed to anneal the conductor 25 in addition to the heating treatment to oxidize the first metal magnetic particles 31 and the second metal magnetic particles 32, the oxidation of the first metal magnetic particles 31 and the second metal magnetic particles 32 may proceed too much, and the magnetic properties of the magnetic base 10 may deteriorate. According to an embodiment of the present invention, the annealing treatment of the conductor 25 and the treatment of forming the magnetic base 10 from the element body 110 proceed in parallel in the second heating step, so that the above problem can be solved or alleviated.

[0077] In addition, since the first metal magnetic particles 31 and the second metal magnetic particles 32 contain a metal (e.g., Fe or Cr) having a higher ionization tendency than the main component metal of the conductor portion 25, in the second heating step, the first metal magnetic particles 31 and the second metal magnetic particles 32 surrounding the conductor portion 25 are oxidized by taking oxygen from the metal oxide film 50 formed on the surface of the conductor portion 25, and most of the oxygen supplied from the atmosphere is consumed by the first metal magnetic particles 31 and the second metal magnetic particles 32 before reaching the conductor portion 25 embedded in the element body 110, so that the oxidation of the conductor portion 25 is suppressed. In addition, since the second heating step is performed in a low oxygen concentration atmosphere having an oxygen concentration of 100 to 2000 ppm, the supply of oxygen to the conductor portion 25 can be limited. In this way, according to the embodiment of the present invention, an increase in electrical resistance due to oxidation of the conductor portion 25 can be suppressed.

[0078] According to an embodiment of the present invention, the surface of the embedded portion 25a of the conductor portion 25 is covered with an insulating oxide layer 60, thereby making it possible to suppress short circuits between the conductor portion 25 and the metal magnetic particles (e.g., the first metal magnetic particles 31 and the second metal magnetic particles 32) contained in the magnetic base 10.

[0079] According to the embodiment of the present invention, the surface of the embedded portion 25a of the conductor portion 25 is covered with the oxide layer 60, and the gap between the conductor portion 25 and the metal magnetic particles constituting the magnetic base 10 is filled with this oxide layer 60, so that it is possible to prevent the atmosphere and moisture in the atmosphere from passing through the magnetic base 10 and reaching the conductor portion 25. Furthermore, since the oxide layer 60 contains an oxide of a metal element contained in the metal magnetic particles, the relative permeability of the oxide layer 60 is higher than that of a conventional resin insulating coating. Therefore, in the coil component 1, the oxide layer 60 provides excellent dielectric strength and oxidation resistance, and also prevents deterioration of the magnetic properties.

[0080] According to one or more embodiments of the present invention, the oxide layer 60 contains zinc oxide, thereby making the oxide layer 60 dense. This can further prevent the air and moisture in the air from reaching the conductor portion 25.

[0081] The dimensions, materials, and arrangement of each component described in this specification are not limited to those explicitly described in the embodiments, and each component can be modified to have any dimensions, materials, and arrangement that can be included in the scope of the present invention. In addition, components not explicitly described in this specification can be added to the described embodiments, and some of the components described in each embodiment can be omitted.

[0082] The designations "first," "second," "third," and the like in this specification are given to identify components, and do not necessarily limit the number, order, or content. Furthermore, numbers for identifying components are used in different contexts, and a number used in one context does not necessarily indicate the same configuration in another context. Furthermore, a component identified by a certain number does not prevent the component from also having the function of a component identified by another number. [Explanation of symbols]

[0083] 1 Coil parts 10 Magnetic substrate 25 Conductor 25a Buried part 25b, 25c exposed part 25d, 25e connection 25f Curved section 31 First metal magnetic particles 32 Second metal magnetic particles 41, 42 Oxide film 45 Binder Resin 50 Metal oxide film 55 void 60 Oxide layer 121 Base material

Claims

1. A step of preparing an intermediate body including a conductor portion formed by bending a base material mainly composed of a metal having a smaller ionization tendency than iron, and an element body having a plurality of metal magnetic particles mainly composed of iron and surrounding at least a portion of the conductor portion; a first heating step of heating the intermediate body at a first temperature to form an oxide film containing an oxide of the metal so as to cover a surface of the conductor portion; a second heating step of heating the intermediate body at a second temperature higher than the first temperature after heating at the first temperature to form an oxide film containing iron oxide on the surface of each of the plurality of metal magnetic particles to form a magnetic base from the element body, forming an insulating oxide layer containing iron oxide and the metal from the oxide film, and annealing the conductor portion; A method for manufacturing a coil component comprising the steps of:

2. A step of preparing an intermediate body including a base material mainly composed of a metal having a smaller ionization tendency than iron, and an element having a plurality of iron-based metal magnetic particles and surrounding at least a portion of the base material; a first heating step of heating the intermediate body at a first temperature to form an oxide film containing an oxide of the metal so as to cover a surface of the base material; a step of forming a conductor portion by bending the base material after the first heating step; a second heating step of heating the intermediate body after the bending process at a second temperature higher than the first temperature to form an oxide film containing iron oxide on the surface of each of the plurality of metal magnetic particles to form a magnetic base from the element body, forming an insulating oxide layer containing iron oxide and the metal from the oxide film, and annealing the conductor portion; A method for manufacturing a coil component comprising the steps of:

3. In the second heating step, at least a part of the metal oxide contained in the oxide film is reduced. The method for manufacturing the coil component according to claim 1 or 2.

4. In the second heating step, each of the plurality of metal magnetic particles is bonded to an adjacent metal magnetic particle via the oxide coating to form the base. The method for manufacturing the coil component according to claim 1 .

5. In the second heating step, the intermediate body is heated in an atmosphere having an oxygen concentration lower than that in the first heating step. The method for manufacturing the coil component according to claim 1 .

6. the substrate is covered with a thermally decomposable insulating coating; The insulating coating is decomposed in the first heating step. The method for manufacturing the coil component according to claim 1 .

7. The preparation step includes a step of applying a suspension containing zinc oxide to a surface of the base material. The method for manufacturing the coil component according to claim 1 .

8. In the second heating step, the oxide layer is formed so as to contain zinc oxide. The method for manufacturing the coil component according to claim 7 .

9. The first temperature is in the range of 100 to 350° C. The method for manufacturing the coil component according to claim 1 .

10. The second temperature is in the range of 600 to 900° C. The method for manufacturing the coil component according to claim 1 .

11. The second heating step is carried out in an atmosphere having an oxygen concentration of 100 to 2000 ppm. The method for manufacturing the coil component according to claim 1 .

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