Coil component and manufacturing method thereof

Abstract

To improve insulation between conductor patterns without reducing effective magnetic permeability.SOLUTION: A magnetic substrate according to an embodiment includes a magnetic substrate, a coil conductor disposed within the magnetic substrate so as to extend around a coil axis, a first external electrode electrically connected to one end of the coil conductor, and a second external electrode electrically connected to the other end of the coil conductor. The coil conductor has a first conductor pattern and a second conductor pattern facing the coil conductor in a first direction along the coil axis. The magnetic substrate has a first region containing a plurality of metal magnetic particles and a second region containing composite oxide particles containing Fe, Ni, and Zn. The second region is disposed so as to be interposed between the first conductor pattern and the second conductor pattern. The second region is magnetic and insulating.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The disclosure herein relates primarily to coil components and methods for manufacturing coil components. [Background technology]

[0002] The coil component includes a magnetic substrate, a coil conductor provided on the magnetic substrate, a first external electrode attached to one end of the coil conductor, and a second external electrode attached to the other end of the coil conductor. One type of magnetic substrate contains a plurality of metal magnetic particles bonded to each other. A magnetic substrate made of metal magnetic particles is less susceptible to magnetic saturation than a magnetic substrate made of a ferrite material. For this reason, coil components including a magnetic substrate made of metal magnetic particles are suitable for use in circuits through which large currents flow (e.g., power supply circuits and DC / DC converter circuits).

[0003] A conventional coil component having a magnetic substrate made of metal magnetic particles is described in Japanese Patent Laid-Open Publication No. 2016-051752 (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-051752 Summary of the Invention [Problem to be solved by the invention]

[0005] As pointed out in Patent Document 1, in a coil component using a magnetic substrate made of metal magnetic particles, when the spacing between the conductor patterns making up the coil conductor becomes small, dielectric breakdown is more likely to occur between the conductor patterns. In Patent Document 1, dielectric breakdown is suppressed by providing a highly insulating non-magnetic portion made of a mixture of glass and alumina between adjacent conductor patterns.

[0006] If a non-magnetic region exists in a part of a magnetic base, the effective permeability of a coil component including the magnetic base decreases. In a coil component, it is desirable that the magnetic base not only have high insulating properties but also have high effective permeability.

[0007] The present invention aims to solve or alleviate at least some of the above-mentioned problems, and more specifically, to improve the insulation between conductor patterns without reducing the effective magnetic permeability in a coil component having a magnetic substrate made of metal magnetic particles.

[0008] Objects of the present invention other than those mentioned above will become clear throughout the entire description of the specification. The inventions described in the claims may solve problems other than those grasped from the "problem to be solved by the invention." The various inventions disclosed in this specification may be collectively referred to as "the present invention." [Means for solving the problem]

[0009] The magnetic substrate in one embodiment includes a magnetic substrate, a coil conductor disposed within the magnetic substrate so as to extend around a coil axis, a first external electrode electrically connected to one end of the coil conductor, and a second external electrode electrically connected to the other end of the coil conductor. The coil conductor has a first conductor pattern and a second conductor pattern facing the coil conductor in a first direction along the coil axis. The magnetic substrate includes a first region containing a plurality of metal magnetic particles and a second region containing composite oxide particles containing Fe, Ni, and Zn. The second region is disposed so as to be interposed between the first conductor pattern and the second conductor pattern. The second region is magnetic and insulating. [Effects of the Invention]

[0010] According to the embodiments of the invention disclosed in this specification, in a coil component having a magnetic substrate made of metal magnetic particles, it is possible to improve the insulation between conductor patterns without reducing the effective magnetic permeability. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view schematically showing a coil component 1 according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view of the coil device 1 of FIG. [Figure 3] FIG. 2 is a perspective view schematically showing a magnetic film 11 provided in the coil component 1. [Figure 4] 2 is a cross-sectional view schematically showing a cross section along the LT plane of the coil device 1 of FIG. 1. FIG. [Figure 5] 2 is a cross-sectional view for schematically showing magnetic flux generated in the coil device 1 of FIG. 1. FIG. [Figure 6] FIG. 10 is a cross-sectional view schematically showing a cross section along the LT plane of a coil device 101 according to another embodiment of the present invention. [Figure 7] FIG. 10 is a cross-sectional view schematically showing a cross section along the LT plane of a coil device 201 according to yet another embodiment of the present invention. [Figure 8] FIG. 2 is a perspective view schematically showing a magnetic film 11 provided in a coil component 301. [Figure 9] FIG. 10 is a cross-sectional view schematically showing a cross section along the LT plane of a coil device 401 according to yet another embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a cross section along the LT plane of a coil device 401 according to yet another embodiment of the present invention. [Figure 11] FIG. 3 is a flow chart showing a manufacturing process of a coil component according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Various embodiments of the present invention will be described below with appropriate reference to the drawings. Components common to multiple drawings are designated by the same reference numerals. 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 necessarily limit the invention according to the claims. Elements described in the following embodiments are not necessarily essential to the solution of the invention.

[0013] First, a coil component 1 according to one embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a perspective view that schematically shows the coil component 1, and Fig. 2 is an exploded perspective view of the coil component 1. Fig. 3 is a perspective view that schematically shows a magnetic film provided in the coil component 1. Fig. 4 is a schematic cross-sectional view of the coil component 1 taken along line II in Fig. 1. For ease of explanation, external electrodes are omitted from Fig. 2.

[0014] 1 to 4 show a laminated inductor and its constituent members as an example of a coil component 1. The illustrated laminated inductor is an example of a coil component 1 to which the present invention can be applied, and the present invention can be applied to various types of coil components other than laminated inductors. For example, the coil component 1 can also be applied to a wire-wound coil component or a planar coil.

[0015] 1, the coil component 1 includes a magnetic base 10, a first external electrode 21 provided on the surface of the magnetic base 10, and a second external electrode 22 provided on the surface of the magnetic base 10 at a position spaced apart from the first external electrode 21. Although not shown in FIG. 1, a coil conductor 25 is provided inside the magnetic base 10. The first external electrode 21 is electrically connected to one end of the coil conductor 25, and the second external electrode 22 is electrically connected to the other end of the coil conductor 25. The coil conductor 25 will be described later.

[0016] The coil component 1 can be mounted on a mounting board 2a. In the illustrated embodiment, 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 first external electrode 21 to the land portion 3a and connecting the second external electrode 22 to the land portion 3b. A circuit board 2 according to one embodiment of the present invention includes the coil component 1 and a mounting board 2a on which the coil component 1 is mounted. The circuit board 2 can be mounted in various electronic devices. Electronic devices on which the circuit board 2 can be mounted include smartphones, tablets, game consoles, automotive electrical components, servers, and various other electronic devices. The coil component 1 can also be built into the board.

[0017] The coil component 1 may be an inductor, a transformer, a filter, a reactor, an inductor array, or any of various other coil components. The coil component 1 may be a coupled inductor, a choke coil, or any of various other magnetically coupled coil components. The uses of the coil component 1 are not limited to those explicitly described in this specification.

[0018] In one embodiment, the magnetic substrate 10 is configured so that its dimension in the L-axis direction (length dimension) is greater than its dimension in the W-axis direction (width dimension) and its dimension in the T-axis direction (height dimension). For example, the length dimension is in the range of 1.0 mm to 6.0 mm, the width dimension is in the range of 0.5 mm to 4.5 mm, and the height dimension is in the range of 0.5 mm to 4.5 mm. The dimensions of the magnetic substrate 10 are not limited to those specifically described in this specification. In this specification, the terms "rectangular parallelepiped" or "rectangular parallelepiped shape" do not necessarily mean "rectangular parallelepiped" in the strict mathematical sense. The dimensions and shape of the magnetic substrate 10 are not limited to those explicitly described in this specification.

[0019] The magnetic 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. The outer surface of the magnetic substrate 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b form the two ends of the magnetic substrate 10 in the height direction, the first end surface 10c and the second end surface 10d form the two ends of the magnetic substrate 10 in the length direction, and the first side surface 10e and the second side surface 10f form the two ends of the magnetic substrate 10 in the width direction. As shown in FIG. 1 , the first main surface 10a, which is located on the upper side of the magnetic substrate 10, may be referred to as the "top surface" in this specification. Similarly, the second main surface 10b may be referred to as the "lower surface" or "bottom surface." The coil component 1 is disposed so that the second main surface 10b faces the mounting substrate 2a, and therefore the second main surface 10b is sometimes called the "mounting surface." The top surface 10a and the bottom surface 10b are spaced apart by the height of the magnetic base 10, the first end surface 10c and the second end surface 10d are spaced apart by the length of the magnetic base 10, and the first side surface 10e and the second side surface 10f are spaced apart by the width of the magnetic base 10.

[0020] 2, the magnetic substrate 10 has a body layer 20, a lower cover layer 19 provided on the lower surface of the body layer 20, and an upper cover layer 18 provided on the upper surface of the body layer 20. The upper cover layer 18, the lower cover layer 19, and the body layer 20 are components of the magnetic substrate 10.

[0021] The main layer 20 includes magnetic films 11 to 17 made of a magnetic material. In the main layer 20, magnetic film 17, magnetic film 16, magnetic film 15, magnetic film 14, magnetic film 13, magnetic film 12, and magnetic film 11 are stacked in this order from the negative side to the positive side in the T-axis direction.

[0022] Each of the magnetic films 11-16 is a laminated sheet made up of a first magnetic sheet containing a plurality of metal magnetic particles and a second magnetic sheet formed on the upper surface of the first magnetic sheet and containing a plurality of composite oxide particles containing Fe, Ni, and Zn. The laminated sheet will be further described with reference to the schematic diagram of the magnetic film 11 shown in FIG. 4. As shown in FIG. 4, the magnetic film 11 is a laminated sheet made up of a first magnetic sheet 31 containing a plurality of metal magnetic particles and a second magnetic sheet 41 formed on the upper surface of the first magnetic sheet 31. Although not shown in the figure, each of the magnetic films 12-16 is also made up of a laminated sheet like the magnetic film 11.

[0023] Conductive patterns C11 to C17 are formed on the upper surfaces of the magnetic films 11 to 17, respectively. Each of the conductive patterns C11 to C17 extends around the coil axis Ax1 (see FIG. 4) in a plane (LW plane) perpendicular to the coil axis Ax1. The conductive patterns C11 to C17 are formed, for example, by printing a conductive paste made of a metal or alloy with excellent conductivity using a screen printing method. The conductive paste is produced by kneading a conductive powder made of a conductive material with excellent conductivity, such as Ag, Pd, Cu, Al, or an alloy thereof, with a binder resin and a solvent. The binder resin may be a PVB resin, a phenolic resin, or a resin known as a binder resin other than the above, or a mixture thereof. When Cu powder is used as the conductive powder, a thermally decomposable resin such as an acrylic resin may be used as the binder resin to suppress excessive oxidation of the Cu powder during degreasing. The conductive paste may contain an adjuster for adjusting thixotropy. The conductive patterns C11 to C17 may be formed using other materials and methods, for example, sputtering, inkjet printing, or other known methods.

[0024] Vias V1 to V6 are formed at predetermined positions of the magnetic films 11 to 16, respectively. The vias V1 to V6 are formed by forming through holes that penetrate the magnetic films 11 to 16 in the T-axis direction at predetermined positions of the magnetic films 11 to 16 and filling the through holes with a conductive material. Each of the conductor patterns C11 to C17 is electrically connected to an adjacent conductor pattern in the direction along the T-axis via the vias V1 to V6.

[0025] The end of the conductor pattern C11 opposite to the end connected to the via V1 is connected to the second external electrode 22. The end of the conductor pattern C17 opposite to the end connected to the via V6 is connected to the first external electrode 21.

[0026] The upper cover layer 18 includes magnetic films 18a-18d made of a magnetic material, and the lower cover layer 19 includes magnetic films 19a-19d made of a magnetic material. In this specification, the magnetic films 18a-18d and the magnetic films 19a-19d are sometimes collectively referred to as "cover layer magnetic films." Furthermore, the components of the magnetic substrate 10 do not necessarily have a laminated structure in which multiple magnetic films are stacked. For example, the upper cover layer 18 may be a compact molded from a magnetic material, rather than a laminate in which multiple magnetic films 18a-18d are stacked.

[0027] 4, the coil conductor 25 has a winding portion 25a wound around a coil axis Ax1 extending along the thickness direction (T-axis direction), a lead-out portion 25b1 extending from one end of the winding portion 25a to the first end face 10c of the magnetic base 10, and a lead-out portion 25b2 extending from the other end of the winding portion 25a to the second end face 10d of the magnetic base 10. Conductor patterns C11 to C17 and vias V1 to V6 form the spiral winding portion 25a. That is, the winding portion 25a has the conductor patterns C11 to C17 and the vias V1 to V6.

[0028] The magnetic substrate 10 is partitioned into multiple regions. The multiple regions constituting the magnetic substrate 10 include a first region 30 and a second region 40. The first region 30 and the second region 40 are both insulating and magnetic, but are made of different magnetic materials. Because the magnetic materials are different, the first region 30 and the second region 40 have different volume resistivities and magnetic permeabilities. Specifically, when comparing a first resistivity indicating the volume resistivity of the first region 30 with a second resistivity indicating the volume resistivity of the second region 40, the second resistivity is greater. When comparing a first permeability indicating the magnetic permeability of the first region 30 with a second permeability indicating the magnetic permeability of the second region 40, the second permeability is greater.

[0029] In one embodiment, the magnetic permeability of the first region 30 is in the range of 20 to 60, and the magnetic permeability of the second region 40 is in the range of 30 to 100. The magnetic permeability of the first region 30 and the second region 40 can be measured using a commercially available analyzer. For example, the magnetic permeability of the first region 30 and the second region 40 is measured using an impedance material analyzer E4991A manufactured by Agilent. The magnetic permeability of the first region 30 and the second region 40 can be measured at a frequency of 100 kHz.

[0030] In one embodiment, the volume resistivity of the first region 30 is 10 5 ~10 8 The volume resistivity of the second region 40 is in the range of 10 7 The volume resistivity of the second region 40 is in the range of Ω·cm or more. However, as described above, the volume resistivity of the second region 40 is greater than the volume resistivity of the first region 30. The volume resistivities of the first region 30 and the second region 40 can be measured in accordance with JIS-K6911.

[0031] The second region 40 is disposed so as to be interposed between adjacent ones of the multiple conductor patterns constituting the coil conductor 25. For example, in the embodiment shown in FIG. 4, a second magnetic material sheet 41 constituting part of the second region 40 is provided between the conductor patterns C11 and C12. Second magnetic material sheets 42, 43, 44, 45, and 46 are also provided between the other adjacent conductor patterns. These second magnetic material sheets 41 to 46 constitute the second region 40. All of the second magnetic material sheets 41 to 46 are provided between adjacent conductor patterns. In other words, adjacent conductor patterns are disposed so as to sandwich one of the second magnetic material sheets 41 to 46 therebetween.

[0032] 4, the second magnetic material sheets 41 to 46 are arranged so as to be in contact with the corresponding conductive patterns C11 to C16, respectively. For example, the second magnetic material sheet 41 is in contact with the conductive pattern C11.

[0033] In the embodiment shown in FIG. 2, each of the second magnetic material sheets 41-46 extends from one end to the other end of the L axis of the base 10. Therefore, the second magnetic material sheets 41-46 are exposed from the first end surface 10c and the second end surface 10d of the base 10. Each of the second magnetic material sheets 41-46 may extend from one end to the other end of the W axis of the base 10. In this case, the base 10 is also exposed from the first side surface 10e and the second side surface 10f of the base 10. The second magnetic material sheets 41-46 are provided so as to contact the lower surface of the corresponding one of the conductor patterns C11-C17. For example, the second magnetic material sheet 41 is provided so as to contact the lower surface of the conductor pattern C11. To ensure insulation between adjacent conductor patterns, it is desirable that each of the second magnetic material sheets 41-46 is configured and arranged so as to cover the entire lower surface of the corresponding conductor pattern.

[0034] In the coil component 1, the second regions 40, which have higher magnetic permeability and volume resistivity than the first regions 30, are disposed between adjacent conductor patterns in the T-axis direction. This second region 40 improves the insulation between adjacent conductor patterns without reducing the effective permeability of the coil component 1. Furthermore, in the coil component 1, the improved insulation between the conductor patterns allows the distance between the conductor patterns to be reduced without causing dielectric breakdown. This allows the dimensions of the coil component 1 in the T-axis direction to be compact.

[0035] In one embodiment of the present invention, the thickness dimension (dimension in the T-axis direction) of each of the second magnetic sheets 41-46 is preferably 3 μm or less. In the coil component 1, the second region 40, which has a high volume resistivity, is interposed between adjacent conductor patterns, allowing the spacing between the adjacent conductor patterns to be small. This allows the thickness dimension of the second region 40 in the T-axis direction to be small. By setting the dimension of the second magnetic sheets 41-46 in the T-axis direction to 3 μm or less, the spacing between the conductor patterns is reduced, allowing the magnetic resistance in the region between the conductor patterns to be increased. As the magnetic resistance between the conductor patterns increases, as shown in FIG. 5, more magnetic flux can pass through the main magnetic path MP1, and the magnetic flux passing through the magnetic path MP2 between the conductor patterns can be reduced. This allows the effective magnetic permeability of the coil component 1 to be further improved.

[0036] The first region 30 refers to a part or all of the region of the magnetic substrate 10 other than the second region 40. The magnetic substrate 10 may be composed of only the first region 30 and the second region 40, or may have regions other than the first region 30 and the second region 40.

[0037] The first region 30 includes a plurality of metal magnetic particles. The metal magnetic particles are composed of a soft magnetic material mainly composed of Fe. The metal magnetic particles contain Si as an additive element in addition to Fe. The metal magnetic particles may contain at least one of Cr and Al in addition to Fe and Si. The metal magnetic particles can contain additive elements other than those mentioned above. The Fe content in the metal magnetic particles can be 94 wt% or more. The Si content in the metal magnetic particles can be 3 wt% or more. The Cr content in the metal magnetic particles can be 1 wt% or more and less than 3 wt%. The Al content in the metal magnetic particles can be 1 wt% or more and less than 3 wt%.

[0038] The average particle size of the plurality of metal magnetic particles contained in the first region 30 is, for example, in the range of 1 to 20 μm. The average particle size of the metal magnetic particles contained in the magnetic base 10 may be 1 to 10 μm, or may be 2 to 8 μm.

[0039] The surface of each of the metal magnetic particles contained in the first region 30 is coated with an insulating film that has excellent insulating properties. Therefore, the metal magnetic particles contained in the magnetic substrate 10 are electrically insulated from each other. In the first region 30, each metal magnetic particle is bonded to an adjacent metal magnetic particle via the insulating film provided on each surface. In other words, the insulating films provided on the surfaces of adjacent metal magnetic particles are bonded to each other, and this bonding between the insulating films bonds the metal magnetic particles covered with the insulating film to each other.

[0040] The metal magnetic particles contained in the first region 30 of the magnetic substrate 10 are obtained, for example, by heating a magnetic powder made of a soft magnetic material. The insulating film provided on the surface of the metal magnetic particles may be an oxide film formed when the magnetic powder, which is the raw material powder, is heated, or may be a coating film applied to the surface of the raw material powder. The coating film may be a thin film whose main component is silica or glass.

[0041] Each of the second magnetic sheets 41 to 46 constituting the second region 40 contains composite oxide particles containing Fe, Ni, and Zn. The second region 40 may contain an additive element in an amount less than any of Fe, Ni, and Zn on a mass basis. The second region 40 may contain at least one element selected from the group consisting of Cu, Mn, Bi, Si, and Sn as an additive element.

[0042] The second region 40 is formed, for example, by the following method. First, a mixed powder obtained by mixing powders of Fe2O3, NiO, and ZnO is calcined at approximately 850°C. Next, the calcined mixed powder is crushed using a wet crusher to obtain a mixed oxide powder with an average particle size of 0.05 to 3 μm. Next, this mixed oxide powder is mixed with water to prepare a magnetic material paste, and this slurry is formed into a sheet to prepare a sheet compact. This sheet compact is heated, for example, within a temperature range (e.g., 800 to 1000°C) at which the ferrite reaction occurs in the mixed oxide powder, thereby forming the second magnetic material sheets 41 to 46. The second magnetic material sheets 41 to 46 thus formed contain composite oxide particles containing Fe, Ni, and Zn. As will be described in more detail later, a laminate may be formed by stacking a sheet compact containing mixed oxide powder on top of a sheet compact containing raw material powder of metal magnetic particles, and then subjecting this laminate to a heat treatment, thereby simultaneously forming the first region 30 and the second region 40 (second magnetic sheets 41 to 46).

[0043] The raw material powders of the complex oxide particles contained in the second region 40, Fe2O3, NiO, and ZnO, as well as the complex oxide containing Fe, Ni, and Zn, all have high insulating properties. Therefore, the second region 40 has high insulating properties. Furthermore, since a ferrite reaction occurs when the complex oxide particles are produced from the raw material powder, the complex oxide particles become magnetic. Therefore, all of the second magnetic sheets 41 to 46 containing such complex oxide particles are magnetic and have high insulating properties.

[0044] When the first region 30 and the second region 40 are formed by heat treatment, the Cr contained in the magnetic powder and the Zn contained in the mixed oxide powder are both oxidized at the contact points between the magnetic powder (the raw material for the first region 30) and the mixed oxide powder (the raw material for the second region 40), forming ZnCr2O4. Therefore, in the substrate 10, ZnCr2O4 is contained at the interface between the first region 30 and the second region 40. Because the magnetic substrate 10 contains ZnCr2O4 at the interface between the first region 30 and the second region 40, the metal magnetic particles contained in the first region 30 and the composite oxide contained in the second region 40 are bonded by ZnCr2O4. This allows the first region 30 and the second region 40 to be strongly bonded. When the magnetic powder contains Al, ZnAl2O4 is generated at the interface between the first region 30 and the second region 40. ZnAl2O4 also strengthens the bond between the first region 30 and the second region 40.

[0045] The mixed oxide powder used to form the second region 40 desirably has an average particle size of 1 μm or less. For example, the average particle size of the mixed oxide powder can be 50 to 300 nm. By reducing the average particle size of the mixed oxide powder, the number of contact points between the raw material powder of the metal magnetic particles and the mixed oxide powder can be increased, thereby promoting the formation of ZnCr2O4 and ZnAl2O4 at the interface between the first region 30 and the second region 40.

[0046] The average particle size of the composite oxide particles contained in the second region 40 is the same as that of the mixed oxide powder, which is the raw material powder. For example, the average particle size of the composite oxide particles contained in the second region 40 can be 0.05 to 3 μm. As described above, the composite oxide particles contained in the second region 40 are produced by heating the mixed oxide powder, which is the raw material powder, at 800 to 1000°C, which is lower than the 1100 to 1400°C that is the general sintering temperature for Ni-Zn ferrite. At a heating temperature of 800 to 1000°C, a ferrite reaction occurs to produce composite oxide particles containing Fe, Ni, and Zn, but there is almost no grain growth of the composite oxide particles. Therefore, the average particle size of the composite oxide particles is the same as that of the mixed oxide powder, which is the raw material powder. The average particle size of the composite oxide particles can be determined to be the same as that of the mixed oxide powder when the difference between the average particle size of the composite oxide particles and that of the mixed oxide powder is within 20% of the average particle size of the mixed oxide powder. The average particle size of the mixed oxide powder and the average particle size of the complex oxide contained in the second region 40 can both be measured using a scanning electron microscope (SEM). The average particle size of the mixed oxide powder is measured by placing the prepared mixed oxide powder on an SEM sample stage and photographing the mixed oxide powder on the sample stage at a magnification of approximately 10,000 to 50,000 times. To measure the average particle size of the complex oxide, first, the substrate 10 is cut or polished along its thickness direction (T-axis direction) to expose a cross section, and an SEM image of the area of ​​the cross section corresponding to the second region 40 is photographed with an SEM at a magnification of approximately 10,000 to 50,000 times. Next, the SEM image of the mixed oxide powder and the SEM image of the cross section of the substrate 10 are analyzed by image analysis to determine the circle-equivalent diameter (Heywood diameter) of each powder and each complex oxide particle constituting the mixed oxide powder. The average circle-equivalent diameter of the mixed oxide powder in the SEM image can be determined as the mixed oxide powder, and the average circle-equivalent diameter of each complex oxide particle can be determined as the average particle size of the complex oxide particles.

[0047] In a cross section of the coil device 1 taken along a cutting plane extending in a direction along the T-axis (for example, a cross section taken along the LT plane as shown in FIG. 4), the area occupied by the second region 40 is 1% to 10% of the total area of ​​the cross section. The second region 40 contains composite oxide particles containing Fe, Ni, and Zn, and is therefore more susceptible to magnetic saturation than the first region 30, which contains metal magnetic particles. Therefore, if the proportion of the second region 40 in the magnetic substrate 10 increases, the magnetic saturation characteristics of the magnetic substrate 10 may deteriorate. In one embodiment of the present invention, by setting the area occupied by the second region 40 to 10% or less, the insulation between the conductor patterns can be improved without reducing the effective permeability due to the second region 40, and deterioration of the magnetic saturation characteristics of the magnetic substrate 10 can be suppressed. The upper limit of the area of ​​the second region 40 may be 5% of the cross-sectional area of ​​the substrate 10.

[0048] The shape and arrangement of the second region 40 shown in Fig. 4 are merely examples, and the shape and arrangement of the second region 40 are not limited to those shown in Fig. 4. The second region 40 may have any shape and arrangement that can be interposed between adjacent conductor patterns to improve the insulation between the conductor patterns. Modified examples of the second region 40 will be described below with reference to Figs. 5 to 8.

[0049] First, a coil device 101 according to another embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 shows a cross-sectional view of the coil device 101 cut along the LT plane. The coil device 101 differs from the coil device 1 in that the second region 40 includes second magnetic sheets 141-146 instead of the second magnetic sheets 41-46.

[0050] Each of the second magnetic material sheets 141-146 extends across the entire area between adjacent conductor patterns in the T-axis direction. In other words, each of the second magnetic material sheets 141-146 is disposed so as to be in contact with both of the adjacent conductor patterns in the T-axis direction. For example, the second magnetic material sheet 141 is in contact with both the adjacent conductor patterns C11 and C12, and extends from the conductor pattern C11 to the conductor pattern C12 along the T-axis direction.

[0051] In the coil component 101, the entire region between adjacent conductor patterns is occupied by the second region 40, which has higher insulating properties than the first region 30, and therefore the insulation between adjacent conductor patterns can be further improved.

[0052] Next, a coil device 201 according to yet another embodiment of the present invention will be described with reference to Fig. 7 and Fig. 8. Fig. 7 shows a cross-sectional view of the coil device 201 cut along the LT plane, and Fig. 8 shows a perspective view of the magnetic film 11 provided in the coil device 201. The coil device 201 differs from the coil device 101 in that the second region 40 includes second magnetic sheets 241-246 instead of the second magnetic sheets 141-146.

[0053] Each of the second magnetic material sheets 241-246 has a ring-like shape extending around the coil axis Ax1 in a plane (LW plane) perpendicular to the coil axis Ax1. Each of the second magnetic material sheets 241-246 is disposed at a position overlapping the corresponding conductor patterns C11-C16 in a plan view. Each of the second magnetic material sheets 241-246 has the same width as the corresponding conductor patterns C11-C16 in a plan view. For example, as shown in FIG. 8, the magnetic film 11 constituting the magnetic substrate 10 is a laminated sheet composed of a first magnetic material sheet 31 and a ring-shaped second magnetic material sheet 241 formed on the upper surface of the first magnetic material sheet 31. The first magnetic material sheet 31 has a rectangular shape. The second magnetic material sheet 241 is formed in the same ring shape as the conductor pattern C11 in a plan view. The second magnetic material sheet 241 may be formed around the coil axis Ax1 for one turn, as shown in Fig. 8, or may be formed only in a range that overlaps with the conductor pattern C11 in the circumferential direction around the coil axis Ax1. Since the conductor pattern C11 has a partial circumferential area cut out as shown in Fig. 2, the second magnetic material sheet 241 may also have a cutout in the same position as the cutout in the conductor pattern C11. The above description of the second magnetic material sheet 241 also applies to the other second magnetic material sheets (second magnetic material sheets 242 to 246).

[0054] According to the coil device 201, the proportion of the area occupied by the second region 40 in the cross section of the magnetic base 10 can be made smaller than in the coil devices 1 and 101. Therefore, the coil device 201 has better magnetic saturation characteristics than the coil devices 1 and 101.

[0055] In the embodiment shown in FIG. 7, the second magnetic sheets 241 to 246 are in contact with only one of the adjacent conductive patterns, but the second magnetic sheets 241 to 246 may be in contact with both of the adjacent conductive patterns.

[0056] Next, a coil device 301 according to yet another embodiment of the present invention will be described with reference to Fig. 9. Fig. 9 shows a cross-sectional view of the coil device 301 cut along the LT plane. The coil device 301 differs from the coil device 201 in that the second region 40 includes second magnetic sheets 341-346 instead of the second magnetic sheets 241-246.

[0057] 9, the second magnetic material sheets 341-346 are configured to have a width greater than that of the corresponding conductor pattern in a plan view (when viewed from the T-axis direction). Therefore, the area of ​​each of the second magnetic material sheets 341-346 in a plan view is greater than that of the corresponding conductor pattern. For example, the area of ​​the second magnetic material sheet 341 in a plan view is greater than the area of ​​the conductor pattern C11 in a plan view.

[0058] According to the coil device 301, the second magnetic sheets 341 to 346 have a larger area than the corresponding conductor patterns, and therefore, the insulation between adjacent conductors can be further improved.

[0059] Next, a coil device 401 according to yet another embodiment of the present invention will be described with reference to Fig. 10. Fig. 10 shows a cross-sectional view of the coil device 401 taken along the LT plane. The coil device 401 differs from the coil device 1 in that the second region 40 additionally includes second magnetic sheets 441 and 442.

[0060] 10, the second magnetic material sheet 441 is provided between the conductor pattern C11 and a portion of the first external electrode 21 that is in contact with the upper surface 10a of the magnetic base 10, and between the conductor pattern C11 and a portion of the second external electrode 22 that is in contact with the upper surface 10a of the magnetic base 10. The second magnetic material sheet 442 is provided between the conductor pattern C17 and a portion of the first external electrode 21 that is in contact with the lower surface 10b of the magnetic base 10, and between the conductor pattern C11 and a portion of the second external electrode 22 that is in contact with the lower surface 10b of the magnetic base 10.

[0061] According to the coil device 401, the second magnetic sheets 441 and 442 can prevent dielectric breakdown from occurring in the magnetic base 10 in the regions between the conductor patterns and the first external electrode 21 and second external electrode 22.

[0062] Next, an example of a method for manufacturing the coil component 1 will be described with reference to FIG. 11 . In the following description, it is assumed that the coil component 1 is manufactured by a sheet lamination method. The coil component 1 may also be manufactured by a known method other than the sheet lamination method. For example, the coil component 1 may be manufactured by a lamination method such as a print lamination method, a thin film process method, or a slurry build method.

[0063] First, in step S1, a green laminate sheet is produced as a precursor of the magnetic films (each of the magnetic films 11 to 17). The green laminate sheet is formed by laminating two layers of sheets. Specifically, the green laminate sheet is made of a first green magnetic sheet as a precursor of the first magnetic sheet, and a second green magnetic sheet as a precursor of the second magnetic sheet.

[0064] The precursor of the first magnetic sheet is produced from a first magnetic material paste obtained by kneading magnetic powder (raw material powder) that is the raw material for metal magnetic particles with a binder resin and a solvent. This raw material magnetic powder is made of a soft magnetic metal material. The magnetic powder contains Fe and Si. The magnetic powder may contain at least one of Cr and Al in addition to Fe and Si. In the following description of the manufacturing method, for ease of understanding, it is assumed that the raw material magnetic powder contains Fe, Si, and Cr. This magnetic material paste is applied to the surface of a plastic base film by a doctor blade method or other common method. A sheet-shaped compact is obtained by drying the magnetic material paste applied to the surface of this base film. This sheet-shaped compact is pressure-molded in a mold at a molding pressure of about 10 to 100 MPa to produce a plurality of green first magnetic sheets.

[0065] The second green magnetic sheet is produced from a second magnetic material paste obtained by kneading a mixed oxide powder, which is a raw material powder of composite oxide particles, with water. The mixed oxide powder is produced by calcining Fe2O3, NiO, and ZnO powders at approximately 850°C and crushing the calcined mixed powders in a wet crusher. The mixed oxide powder is crushed to an average particle size of 0.05 to 3 μm. Next, the mixed oxide powder is mixed with water to produce a slurry, which is then formed into a sheet to obtain the second green magnetic sheet.

[0066] Next, the first green magnetic sheet and the second green magnetic sheet prepared as described above are laminated together to obtain a green laminated sheet.

[0067] Next, in step S2, a conductive paste is applied to the plurality of green laminate sheets prepared in step S1. The conductive paste is applied to the upper surface of the second green magnetic sheet so as to cover at least a portion of the second green magnetic sheet of the green laminate sheet. The conductive paste is produced by kneading a conductive powder made of a conductive material with excellent conductivity, such as Ag, Pd, Cu, Al, or an alloy thereof, with a binder resin and a solvent. By applying the conductive paste to the green laminate sheet, an unfired conductive pattern is formed on the green laminate sheet, which will become the conductive patterns C11 to C16 after firing. The conductive paste is also applied to the first green magnetic sheet that is not laminated with the second green magnetic sheet. The conductive paste applied to this first green magnetic sheet will become the conductive pattern C17 after firing.

[0068] Each green laminate sheet has a through hole formed therein that penetrates the sheet in the stacking direction. A conductive paste is also filled into these through holes. In this way, unfired vias that will become vias V1 to V5 after firing are formed in the through holes of the magnetic sheets. The conductive paste is applied to the green laminate sheets and the first green magnetic sheet by, for example, a screen printing method.

[0069] Next, in step S3, the green laminate sheets coated with the conductive paste and the first green magnetic sheets are laminated to form an intermediate laminate that will become the main layer 20 after firing. Furthermore, by laminating the first green magnetic sheets, an upper laminate that will become the upper cover layer 18 after firing and a lower laminate that will become the lower cover layer 19 after firing are fabricated. The first green magnetic sheets that form the upper laminate become the magnetic films 18a-18d in the finished coil component 1, and the first green magnetic sheets that form the lower laminate become the magnetic films 19a-19d in the finished coil component 1. The six green laminate sheets and one green first magnetic sheet that form the intermediate laminate become the magnetic films 11-17 in the finished coil component 1. The intermediate laminate fabricated as described above is sandwiched between the upper laminate and the lower laminate, and the upper laminate and the lower laminate are thermocompression bonded to the intermediate laminate to obtain the main laminate. Next, the main body laminate is divided into individual pieces using a cutting machine such as a dicing machine or a laser processing machine to obtain a chip laminate. The chip laminate is an example of a molded body including an element that will become magnetic base 10 after heat treatment and an unsintered conductor pattern that will become coil conductor 25 after heat treatment. The element that will become magnetic base 10 after heat treatment and the molded body including an unsintered conductor pattern that will become coil conductor 25 after heat treatment may be produced by a method other than the sheet lamination method.

[0070] Next, in step S4, the green body produced in step S3 is degreased. The degreasing of the green body can be performed in a non-oxygen atmosphere such as a nitrogen atmosphere. By performing the degreasing in a non-oxygen atmosphere, it is possible to prevent the Fe contained in the raw material powder from being oxidized during the degreasing. The degreasing is performed, for example, at 300 to 500°C for 30 to 60 minutes. The degreasing decomposes the thermally decomposable resin contained in the green body, so that no thermally decomposable resin remains in the green body after the degreasing is completed. By using the same thermally decomposable resin for the conductive paste as for the magnetic material paste, the binder resin contained in the unsintered conductor pattern is also thermally decomposed during the degreasing of step S4. Thus, in step S4, all of the first green magnetic sheet, the second green magnetic sheet, and the unsintered conductor pattern that constitute the green body are degreased.

[0071] This degreased compact is then subjected to a heat treatment in step S5. The heat treatment is carried out in the atmosphere at 800 to 1000°C for 1 to 6 hours. The heat treatment in step S5 may be carried out in a low-oxygen concentration atmosphere containing oxygen in the range of 5 to 10000 ppm.

[0072] During this heat treatment, an insulating oxide film is formed on the surface of the magnetic powder contained in the first green magnetic material sheet by oxidizing the elements contained in the magnetic powder, thereby forming a first region 30 from the first green magnetic material sheet, which has a plurality of metal magnetic particles bonded together via the insulating film.

[0073] Furthermore, in the heat treatment of step S5, a ferrite reaction occurs in the mixed oxide powder contained in the second green magnetic sheet, thereby forming the second region 40 (second magnetic sheets 41 to 46) containing composite oxide particles containing Fe, Ni, and Zn from the second green magnetic sheet.

[0074] Furthermore, in the heat treatment of step S5, ZnCr2O4 is formed at the interface between the first green magnetic sheet and the second green magnetic sheet, which firmly bonds the first region 30 formed from the first green magnetic sheet and the second region 40 formed from the second green magnetic sheet.

[0075] The above reaction occurs in the compact due to the heat treatment in step S5. As a result of this heat treatment, the magnetic substrate 10 is obtained from the compact.

[0076] Furthermore, the heat treatment in step S5 also sinters the conductor powder in the unsintered conductor pattern. The sintering of the conductor powder in the unsintered conductor pattern results in the coil conductor 25. When copper powder is used as the conductor powder, the copper crystals are densely sintered to form the coil conductor 25. The heat treatment is carried out at a temperature lower than the melting point of the metal (Cu or Ag) used as the material for the conductor powder. When Ag is used as the conductor powder, the heating temperature in step S5 is set to 800 to 950°C.

[0077] Next, in step S6, a first external electrode 21 and a second external electrode 22 are formed on the surface of the magnetic base 10 obtained in step S5. The first external electrode 21 is connected to one end of the coil conductor 25, and the second external electrode 22 is connected to the other end of the coil conductor 25. Before forming the first external electrode 21 and the second external electrode 22, the molded body after the second heat treatment may be impregnated with a resin. The molded body is impregnated with a thermosetting resin such as an epoxy resin. This allows the resin to penetrate into the gaps between the metal magnetic particles in the magnetic base 10. Then, by curing the resin impregnated in the magnetic base 10, the mechanical strength of the magnetic base 10 can be improved.

[0078] Through the above steps, the coil component 1 is produced.

[0079] The dimensions, materials, and arrangements of each component described in the various embodiments above are not limited to those explicitly described in each embodiment, and each component can be modified to have any dimensions, materials, and arrangements that may fall within the scope of the present invention.

[0080] Components not explicitly described in this specification may be added to each of the above-described embodiments, and some of the components described in each embodiment may be omitted.

[0081] The designations "first," "second," "third," etc. in this specification are used to identify components and do not necessarily limit the number, order, or content thereof. Furthermore, numbers used to identify components are used in different contexts, and numbers used in one context do not necessarily indicate the same configuration in another context. Furthermore, this does not prevent a component identified by a certain number from also serving the function of a component identified by another number.

[0082] This specification also discloses the following techniques. [Appendix 1] A magnetic substrate (10); a coil conductor (25) provided within the magnetic base so as to extend around a coil axis (Ax1); a first external electrode (21) electrically connected to one end of the coil conductor; a second external electrode (22) electrically connected to the other end of the coil conductor; Equipped with the coil conductor has a first conductor pattern (C13) and a second conductor pattern (C14) facing the first conductor pattern in a first direction along the coil axis, The magnetic substrate includes a first region (30) containing a plurality of metal magnetic particles, and a magnetic insulating second region (40) containing composite oxide particles containing Fe, Ni, and Zn, and disposed so as to be interposed between the first conductive pattern and the second conductive pattern. Coil parts. [Appendix 2] a second resistivity indicating the volume resistivity of the second region is greater than a first resistivity indicating the volume resistivity of the first region; The coil component described in [Appendix 1]. [Appendix 3] a second magnetic permeability indicating the magnetic permeability of the second region is greater than a first magnetic permeability indicating the magnetic permeability of the first region; A coil component described in [Appendix 1] or [Appendix 2]. [Appendix 4] The dimension of the second region in the first direction is 3 μm or less. A coil component according to any one of [Appendix 1] to [Appendix 3]. [Appendix 5] a lower surface of the first conductor pattern facing an upper surface of the second conductor pattern; the second region covers the entire lower surface of the first conductor pattern. A coil component according to any one of [Appendix 1] to [Appendix 4]. [Appendix 6] an end of the second region is exposed from the magnetic substrate; A coil component according to any one of [Appendix 1] to [Appendix 5]. [Appendix 7] the second region is in contact with at least the first conductor pattern; A coil component according to any one of [Appendix 1] to [Appendix 6]. [Appendix 8] the second region is in contact with both the first conductor pattern and the second conductor pattern; The coil component described in [Appendix 7]. [Appendix 9] When viewed from the direction of the coil axis, the area of ​​the second region is larger than both the area of ​​the first conductor pattern and the area of ​​the second conductor pattern. A coil component according to any one of [Appendix 1] to [Appendix 8]. [Appendix 10] the metal magnetic particles contain Cr, the magnetic substrate contains ZnCr2O4 at the interface between the first region and the second region; A coil component according to any one of [Appendix 1] to [Appendix 9]. [Appendix 11] In a cross section of the magnetic base taken along a cutting plane passing through the coil axis, the area occupied by the second region is 1% to 10% of the area of ​​the cross section. A coil component according to any one of [Appendix 1] to [Appendix 10]. [Appendix 12] the second region is also disposed between the second conductor pattern and the first external electrode and between the second conductor pattern and the second external electrode; A coil component according to any one of [Appendix 1] to [Appendix 11]. [Appendix 13] forming a plurality of laminated sheets including a first green magnetic sheet containing a magnetic powder and a second green magnetic sheet covering at least a portion of the top surface of the first green magnetic sheet and containing Fe2O3 powder, ZnO powder, and NiO powder; forming a conductive pattern on the upper surface of each of the plurality of laminated sheets so as to cover at least a portion of the green second magnetic sheet; stacking the plurality of laminate sheets to form a laminate; a heating step of heating the laminate to form a magnetic substrate; providing an external electrode on the magnetic substrate; A method for manufacturing a coil component comprising: [Appendix 14] The laminate is heated at 800 to 1000°C. A method for manufacturing the coil component described in [Appendix 13]. [Appendix 15] In the heating step, ZnCr2O4 is generated at the interface between the first green magnetic sheet and the second green magnetic sheet. A method for manufacturing a coil component according to [Appendix 13] or [Appendix 14]. [Explanation of symbols]

[0083] 1 Coil parts 10 Magnetic substrate 21 1st external electrode 22 Second external electrode 30 First Area 40 Second Domain

Claims

1. a magnetic substrate; a coil conductor provided within the magnetic substrate so as to extend around a coil axis; a first external electrode electrically connected to one end of the coil conductor; a second external electrode electrically connected to the other end of the coil conductor; Equipped with the coil conductor has a first conductor pattern and a second conductor pattern facing the first conductor pattern in a first direction along the coil axis, the magnetic substrate includes a first region containing a plurality of metal magnetic particles, and a second region that is magnetic and insulating and contains composite oxide particles containing Fe, Ni, and Zn, and is disposed so as to be interposed between the first conductive pattern and the second conductive pattern; Coil parts.

2. a second resistivity indicating a volume resistivity of the second region is greater than a first resistivity indicating a volume resistivity of the first region; The coil component according to claim 1 .

3. a second magnetic permeability indicating the magnetic permeability of the second region is greater than a first magnetic permeability indicating the magnetic permeability of the first region; The coil component according to claim 1 .

4. The dimension of the second region in the first direction is 3 μm or less. The coil component according to claim 1 or 2.

5. a lower surface of the first conductor pattern faces an upper surface of the second conductor pattern, the second region covers the entire lower surface of the first conductor pattern; The coil component according to claim 1 or 2.

6. an end of the second region is exposed from the magnetic substrate; The coil component according to claim 1 or 2.

7. the second region is in contact with at least the first conductor pattern; The coil component according to claim 1 or 2.

8. the second region is in contact with both the first conductor pattern and the second conductor pattern; The coil component according to claim 7 .

9. When viewed from the coil axis direction, the area of ​​the second region is larger than both the area of ​​the first conductor pattern and the area of ​​the second conductor pattern. The coil component according to claim 1 or 2.

10. the metal magnetic particles contain Cr, The magnetic substrate has a ZnCr layer at the interface between the first region and the second region. 2 O 4 containing The coil component according to claim 1 or 2.

11. In a cross section of the magnetic base taken along a cutting plane passing through the coil axis, the area occupied by the second region is 1% to 10% of the area of ​​the cross section. The coil component according to claim 1 or 2.

12. the second region is also disposed between the second conductor pattern and the first external electrode and between the second conductor pattern and the second external electrode; The coil component according to claim 1 or 2.

13. a green first magnetic sheet containing magnetic powder; and a magnetic material covering at least a portion of the upper surface of the green first magnetic sheet, the magnetic material being Fe. 2 O 3 forming a plurality of laminated sheets including a green second magnetic sheet containing a powder, ZnO powder, and NiO powder; forming a conductive pattern on the upper surface of each of the plurality of laminated sheets so as to cover at least a portion of the green second magnetic sheet; stacking the plurality of laminate sheets to form a laminate; a heating step of heating the laminate to form a magnetic substrate; providing an external electrode on the magnetic substrate; A method for manufacturing a coil component comprising:

14. The laminate is heated at 800 to 1000°C. The method for manufacturing a coil component according to claim 13 .

15. In the heating step, ZnCr is added to the interface between the first green magnetic sheet and the second green magnetic sheet. 2 O 4 is generated, The method for manufacturing a coil component according to claim 13 or 14.

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