Coil component

Abstract

To improve the adhesion between a substrate and an external electrode in a coil component equipped with a composite substrate.SOLUTION: A coil component includes substrate containing metal magnetic particles and a resin, a coil conductor provided inside a substrate, an external electrode provided on the surface of the substrate so as to be electrically connected to the coil conductor, and ceramic particles provided between the substrate and the external electrode.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a coil component. [Background technology]

[0002] Coil components are components mounted in various electronic devices, and are used, for example, in power supply circuits of DC / DC converters, etc. The coil component includes a base, a coil conductor provided inside the base, and an external electrode provided on the surface of the base.

[0003] A known substrate for a coil component is a metal composite substrate, which includes a large number of metal magnetic particles and a resin binder that binds the metal magnetic particles together. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-202325 Summary of the Invention [Problem to be solved by the invention]

[0005] In a configuration including a composite substrate, it has been pointed out that the presence of a resin component in the substrate tends to result in poor adhesion between the substrate and the external electrodes disposed on the surface of the substrate. Therefore, there is a need to improve the adhesion between the substrate and the external electrodes in coil components including a composite substrate.

[0006] An object of the present disclosure is to improve the adhesion between a substrate and an external electrode in a coil component having a composite substrate. [Means for solving the problem]

[0007] One aspect of the present disclosure is a coil component having a base containing metal magnetic particles and a resin, a coil conductor provided inside the base, an external electrode provided on a surface of the base so as to be electrically connected to the coil conductor, and ceramic particles provided between the base and the external electrode. [Effects of the Invention]

[0008] According to the present disclosure, in a coil component including a composite substrate, the adhesion of external electrodes can be improved. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating a coil component according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line II in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line II-II in FIG. 2. [Figure 4] FIG. 3 is an enlarged view of a portion III in FIG. 2. [Figure 5] FIG. 5 is a diagram showing a configuration according to the prior art, corresponding to FIG. 4. [Figure 6] FIG. 5 is a diagram showing a modified example corresponding to FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0010] Embodiments of the present disclosure will be described in detail below, but the present disclosure is not limited thereto. In this specification and drawings, components having substantially the same functional configurations may be designated by the same reference numerals to avoid redundant description. The drawings are schematic diagrams shown to facilitate understanding of the present disclosure and are not necessarily drawn to scale. The drawings also appropriately show mutually orthogonal L-axis, W-axis, and H-axis as axes defining a fixed coordinate system fixed to the coil component.

[0011] <Basic structure of coil components> First, the basic structure of a coil device 1 according to an embodiment of the present disclosure will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view of the coil device 1 according to an embodiment of the present disclosure. FIG. 2 is a cross-sectional view taken along line II in FIG. 1, and FIG. 3 is a cross-sectional view taken along line II-II in FIG. 2. The coil device 1 shown in FIGS. 1 to 3 is an inductor and can be used as a power inductor incorporated in a power line or various other inductors. Note that the drawings appropriately show an L-axis, a W-axis, and an H-axis, which are orthogonal to each other. The L-axis, W-axis, and H-axis define a fixed coordinate system fixed with respect to the coil device 1.

[0012] 1 to 3, the coil component 1 has a base 10 and external electrodes 20 provided on the surface of the base 10. The external electrodes 20 include a first external electrode 20a and a second external electrode 20b that are spaced apart from each other. Furthermore, the coil component 1 has a coil conductor 30 provided inside the base 10, as shown in FIGS.

[0013] 1, the coil component 1 is configured to be mounted on a mounting substrate 2a. The mounting substrate 2a is provided with land portions 3a and 3b at two locations. The coil component 1 is mounted on the mounting substrate 2a by joining an external electrode 20a to the land portion 3a and an external electrode 20b to the land portion 3b.

[0014] The circuit board 2 includes the coil component 1 and a mounting board 2a on which the coil component 1 is mounted. The circuit board 2 may include various electronic components other than the coil component 1. The circuit board 2 can be mounted in various electronic devices. Examples of such electronic devices include smartphones, tablets, game consoles, servers, and automotive electrical components.

[0015] As shown in FIG. 1, the base 10 has a generally rectangular parallelepiped shape. The 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. The outer surface of the base 10 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. The outer edge of the first main surface 10a is defined by four sides. In the embodiment shown in FIGS. 1 to 3, the outer edge of the first main surface 10a is defined by a pair of short sides and a pair of long sides. Similar to the first main surface 10a, the outer edge of the second main surface 10b is also defined by a pair of short sides and a pair of long sides. The first end face 10c connects the short side of the first main surface 10a to the short side of the second main surface 10b, and the first side face 10e connects the long side of the first main surface 10a to the long side of the second main surface 10b.

[0016] In FIG. 1, the first main surface 10a is located on the upper side of the base 10, and therefore the first main surface 10a is sometimes referred to as the "upper surface." Similarly, the second main surface 10b is sometimes referred to as the "lower surface." The coil component 1 is disposed so that the second main surface 10b faces the mounting board 2a, and therefore the second main surface 10b is sometimes referred to as the "mounting surface." The up-down direction of the base 10 is also referred to as the height direction, and is defined as the H-axis direction in the drawings. The longitudinal direction of the base 10 is also referred to as the length direction, and is defined as the L-axis direction in the drawings. Furthermore, the direction perpendicular to both the height direction (H-axis direction) and the length direction (L-axis direction) is called the width direction, and is defined as the W-axis direction in the drawings.

[0017] 1 to 3, each of the faces 10a to 10f of the base 10 is illustrated as a flat surface, but each of the faces 10a to 10f may be a curved surface. Furthermore, each of the faces 10a to 10f is illustrated as being perpendicular to the adjacent faces, but each of the faces 10a to 10f does not have to be perpendicular to the adjacent faces. Each of the vertices of the base 10 may be rounded, and the ridge lines of the base 10 (lines indicating the boundaries between adjacent faces among the faces 10a to 10f) may not be straight, but may be curved depending on the shape and arrangement of each of the faces 10a to 10f.

[0018] The coil component 1 can be a small coil component. The coil component 1 can be formed, for example, so that the length dimension (dimension in the L-axis direction) is 0.2 mm to 4.0 mm, the width dimension (dimension in the W-axis direction) is 0.1 mm to 4.0 mm, and the height dimension (dimension in the H-axis direction) is 0.1 mm to 4.0 mm. In this way, the coil component 1 may be configured so that the length dimension is greater than the width dimension.

[0019] When the length dimension of the coil component 1 is greater than the width dimension, the L-axis direction may be referred to as the long-side direction of the coil component 1, and the W-axis direction may be referred to as the short-side direction of the coil component 1. The dimension of the coil component 1 in the short-side direction may be 3.0 mm or less. Furthermore, at least one of the length dimension, width dimension, and height dimension of the coil component 1 may be 4.0 mm or less, 20 mm or less, 1.0 mm or less, or 0.65 mm or less. The coil component 1 may be thin, and specifically, the length dimension of the coil component 1 may be greater than the height dimension. The length dimension of the coil component 1 may be two or more times the height dimension, or even three or more times the height dimension. The height dimension of the coil component 1 may be 1 mm or less. These dimensions of the coil component 1 are merely examples, and the coil component 1 according to this embodiment may have any dimensions.

[0020] <Coil conductor 30> The coil conductor 30 has a winding portion 31 extending in the circumferential direction around the axis Ax, which is the central axis of the coil component 1, and a lead portion 32 drawn out from the winding portion 31 and connected to the external electrode 20. The lead portion 32 includes a lead portion 32a drawn out from one end of the winding portion 31 and connected to the first external electrode 20a, and a lead portion 32b drawn out from the other end of the winding portion 31 and connected to the second external electrode 20b.

[0021] In the embodiment shown in FIGS. 1 to 3, the coil conductor 30 is provided inside the base 10. In other words, a winding portion 31, which is a part of the coil conductor 30, is embedded in the base 10. The lead portions 32a and 32b are connected to the coil conductor 30, and their tips are respectively led out to the outside of the base 10 from the second main surface 10b, the first end face 10c, or the second end face 10d. In FIGS. 2 and 3, as an example, the lead portions 32a and 32b are exposed to the outside of the base 10 from the first end face 10c and the second end face 10d. The lead portion 32a is connected to the external electrode 20a at the end face exposed from the base 10, and the lead portion 32b is connected to the external electrode 20b at the end face exposed from the base 10.

[0022] The axis Ax of the coil device 1 is a virtual axis extending in a direction intersecting the first main surface (upper surface) 10a and the second main surface (lower surface) 10b, and is an axis extending in the height direction (H-axis direction) in the drawings. The axis Ax may be, for example, an axis extending along a straight line passing through the geometric center of gravity when the coil device 1 is viewed from the first main surface (upper surface) 10a in the H-axis direction, and the geometric center of gravity when the coil device 1 is viewed from the second main surface (lower surface) 10b in the H-axis direction.

[0023] 1 to 3, the winding portion 31 has a so-called horizontal winding structure in which it winds around the first main surface (upper surface) 10a or the second main surface (lower surface) 10b of the coil device 1. However, the winding portion 31 may have a so-called vertical winding structure in which it winds around the first end surface 10c or the second end surface 10d, or the first side surface 10e or the second side surface 10f of the coil device 1. The winding portion 31 may have a single-phase structure consisting of one winding portion, or may have a multi-layer structure in which multiple winding portions are stacked, as in the embodiment shown in FIGS. 1 to 3.

[0024] The number of turns in the winding portion 31 of the coil conductor 30 is not particularly limited and may be one or more. When the lead-out portions 32 are provided at opposing positions around the periphery of the winding portion 31, the number of turns may be less than one, such as 1.5 turns or 2.5 turns.

[0025] The coil conductor 30 can be made of a material with excellent conductivity, such as copper (Cu), silver (Ag), or gold (Au). The surface of the coil conductor 30 may be covered with an insulating coating. The insulating coating that covers the coil conductor 30 may contain, for example, a thermosetting resin with excellent insulating properties. Examples of resins that can be used for this insulating coating include polyurethane, polyamide-imide, polyimide, polyester, and polyester-imide.

[0026] <Base> The substrate 10 may be a metal composite substrate formed from a composite magnetic material. The metal composite substrate 10 can be obtained, for example, by pressure molding a slurry, granules, or pellets obtained by kneading a composite magnetic material containing metal magnetic particles and a resin as a binder. Therefore, the substrate 10 in this embodiment contains metal magnetic particles and a resin binder. In other words, the substrate 10 is formed by connecting multiple metal magnetic particles with resin, and the metal magnetic particles are bonded by the resin.

[0027] The metal magnetic particles contained in the substrate 10 may be a mixture of one type or multiple types of metal magnetic particles. Examples of metal magnetic particles contained in the substrate 10 include metal particles such as iron (Fe) and nickel (Ni); crystalline alloy particles such as Fe-Si-Cr alloy, Fe-Si-Al alloy, and Fe-Ni alloy; and amorphous alloy particles such as Fe-Si-Cr-BC alloy and Fe-Si-Cr-B alloy. Further examples of metal magnetic particles contained in the substrate 10 include Co-Nb-Zr alloy, Fe-Zr-Cu-B alloy, Fe-Si-B alloy, Fe-Co-Zr-Cu-B alloy, Ni-Si-B alloy, and Fe-Al-Cr alloy. Furthermore, the metal magnetic particles contained in the substrate 10 may contain P. These metal magnetic particles can be used alone or in combination to form mixed particles.

[0028] When the metal magnetic particles contained in the substrate 10 are Fe-based metal magnetic particles, the metal magnetic particles may contain 80 wt% or more of Fe. An insulating film may be formed on the surface of each metal magnetic particle. This insulating film may be an oxide film formed by oxidizing the metal element contained in the metal magnetic particle. The insulating film provided on the surface of each metal magnetic particle may be a silicon oxide film. The silicon oxide film can be formed by coating the surface of the metal magnetic particle using, for example, a sol-gel method.

[0029] The average particle size of the metal magnetic particles contained in the substrate 10 may preferably be 1 μm or more and 60 μm or less. The metal magnetic particles may have a certain degree of particle size distribution.

[0030] The particle size distribution and average particle size of the particles contained in the coil component 1 can be measured and calculated by image analysis. For example, a cross section of a portion containing particles is exposed and photographed using a scanning electron microscope (SEM). Based on the obtained SEM image, for example, the area-based particle size distribution of the maximum particle size is determined, and the average particle size, such as the median diameter (D50), is calculated based on this particle size distribution. The maximum particle size is the longest length of the observed particles, and may be the major axis diameter. Therefore, in the case of metal magnetic particles, for example, the median diameter (D50) calculated from the particle size distribution of the metal magnetic particles determined based on the SEM image can be used as the average particle size of the metal magnetic particles. Note that the particles contained in the coil component 1 are particles that are components of the coil component 1, and include metal magnetic particles in the base 10, particles other than the metal magnetic particles contained in the base 10, and ceramic particles (described below) disposed between the base 10 and the external electrode 20.

[0031] The content of metal magnetic particles in base 10 may be 85 vol% or more, or may be 87 vol% or more. When base 10 contains multiple types of metal magnetic particles, the content of metal magnetic particles means the total content of the multiple types of metal magnetic particles.

[0032] The resin contained in the base 10 may include, for example, a thermosetting resin with excellent insulating properties. Examples of resins contained in the base 10 include epoxy resin, polyimide resin, polystyrene (PS) resin, high-density polyethylene (HDPE) resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinylidene fluoride (PVDF) resin, phenol resin, polytetrafluoroethylene (PTFE) resin, and polybenzoxazole (PBO) resin. These resins can be used alone or in combination of two or more.

[0033] The substrate 10 may further contain inorganic particles other than the above-described metal magnetic particles. Such inorganic particles contained in the substrate 10 may be SiO2 particles (silica particles), Al2O3 particles, glass-based particles, particles made of other inorganic materials, or a mixture of two or more of these particles. When the substrate 10 contains inorganic particles, the inorganic particles can enter the gaps between the metal magnetic particles and stabilize the arrangement of the metal magnetic particles. Therefore, when the substrate 10 contains inorganic particles, the mechanical strength of the substrate 10 can be improved. Such inorganic particles are embedded in the substrate 10 and are not substantially exposed on the surface of the substrate 10. The average particle size of the inorganic particles may be, for example, 0.01 μm or more and 1 μm or less.

[0034] <External electrode> The external electrode 20 is electrically connected to the coil conductor 30. More specifically, the first external electrode 20a is electrically connected to the winding portion 31 of the coil conductor 30 via the lead-out portion 32a, and the second external electrode 20b is electrically connected to the winding portion 31 of the coil conductor 30 via the lead-out portion 32b. Therefore, the external electrode 20 is disposed on the surface from which the lead-out portion 32 of the coil conductor 30 is extended. In the embodiment shown in FIGS. 1 to 3, the lead-out portions 32a and 32b of the coil conductor 30 are extended to the first end face 10c and the second end face 10d, respectively. Therefore, the first external electrode 20a is disposed at least on the first end face 10c so as to include the exposed position of the lead-out portion 32a on the surface of the base 10. Furthermore, the second external electrode 20b is disposed at least on the second end face 10d so as to include the exposed position of the lead-out portion 32b on the surface of the base 10. It should be noted that no ceramic particles 50 exist between the external electrode 20 and the lead-out portion 32 of the coil conductor 30 .

[0035] 1, the first external electrode 20a is arranged not only on the first end face 10c from which the lead portion 32a of the coil conductor 30 is led out, but also on the second main face (lower face) 10b, the first side face 10e, and the second side face 10f. Similarly, the second external electrode 20b is arranged not only on the first end face 10d from which the lead portion 32b of the coil conductor 30 is led out, but also on the second main face (lower face) 10b, the first side face 10e, and the second side face 10f. In this way, the external electrode 20 has a shape that extends continuously across two adjacent faces of the base 10, or across a ridge line formed by the contact of two faces, or further across all four faces so as to include two adjacent vertices of the rectangular parallelepiped shape of the base 10, thereby making it difficult for the external electrode 20 to come off the surface of the base 10.

[0036] However, the arrangement of the external electrode 20 on the surface of the base 10 is not limited to the configuration shown in FIGS. 1 to 3. For example, the external electrode 20 may be arranged so as to contact only the first end surface 10c of the base 10 and not contact the other surfaces of the base 10. That is, the external electrode 20 may be arranged on only one surface of the base 10, rather than extending continuously across multiple surfaces of the base 10. Arranging the external electrode 20 on only one surface of the base 10, or across multiple adjacent surfaces of the base 10, is preferable because it contributes to miniaturization of the coil component 1 since the external electrode 20 does not have a thickness, allowing for smaller dimensions; it simplifies the process of forming the external electrode 20 in manufacturing the coil component 1; and in addition to miniaturization, the absence of electrodes on the side surfaces eliminates the risk of short circuits with adjacent components, facilitating high-density mounting.

[0037] The external electrode 20 may include a metal layer (metal foil) formed by applying a conductive paste to the surface of the base 10 by screen printing or the like and then heating the applied conductive paste. The thickness of such a metal layer is not particularly limited, but may be, for example, 1 μm or more and 5 μm or less. The conductive paste may contain a conductive material with excellent conductivity, such as silver (Ag), palladium (Pd), copper (Cu), aluminum (Al), nickel (Ni), or an alloy thereof. The metal content of the metal layer may be, for example, 90 to 99 vol%. The external electrode 20 may include a plating layer. The plating layer may be a plurality of layers, such as two or more layers. When the plating layer is composed of two layers, the composition of each layer is not particularly limited, but may include, for example, a Cu plating layer, an Ag plating layer, a Ni plating layer, and a Sn plating layer disposed on the outer side (farther from the metal layer). The thickness of the plating layer may be, for example, 2 μm or more and 5 μm or less. When the external electrode 20 includes a metal layer and a plating layer, the thickness of the external electrode 20 may be, for example, not less than 3 μm and not more than 10 μm.

[0038] Furthermore, a conductive resin layer may be used in the external electrode 20 instead of or in addition to the metal layer described above. The conductive resin layer is made of a composite material in which conductive particles such as metal particles are dispersed in a resin material. If the external electrode 20 includes a conductive resin layer, this is preferable because the inclusion of a resin material improves adhesion regardless of the unevenness of the surface of the base 10, absorbs external impacts, and reduces stress generated in the external electrode 20.

[0039] The conductive particles contained in the conductive resin layer may be made of highly conductive metals such as silver (Ag), palladium (Pd), copper (Cu), aluminum (Al), nickel (Ni), and alloys thereof, with Ag and Cu being preferred. These metals may be used singly or in combination. The conductive particles contained in the conductive resin layer may be spherical, elongated, flat, rod-shaped, or the like, with a combination of rod-shaped, spherical, and flat shapes being preferred. The conductive particles may have an average maximum particle size of 0.1 μm or more and 10 μm or less, and an average minimum particle size of 0.05 μm or more and 1 μm or less.

[0040] The conductive resin layer may contain conductive particles in an amount of 30% to 70% by volume, with the remainder being resin. Specific examples of the resin material contained in the conductive resin layer include epoxy resin, phenolic resin, and acrylic resin.

[0041] <Adhesion between the substrate and external electrodes> As shown in Figs. 1 to 3, the external electrode 20 is provided on the surface IF of the base 10. Fig. 4 shows an enlarged view of a portion III in Fig. 2. Fig. 5 shows a configuration according to the prior art corresponding to Fig. 4. Figs. 4 and 5 are microscopic views of a cross section spanning the base 10 and the external electrode 20, and are cross sections along the LW plane of the coil device 1, but any cross section in a direction perpendicular to the surface IF of the base 10 may be used. In the present embodiment, observation may also be based on a cross section along the LH plane.

[0042] As shown in Figure 5, in the prior art, the external electrode 20 is disposed in direct contact with the surface IF of the base 10 without any intervening layer. As described above, in the prior art, the two members, the base 10 and the external electrode 20, are simply joined together, so sufficient adhesion between the base 10 and the external electrode 20 may not be obtained, and the external electrode 20 may peel off from the surface of the base 10 due to an impact or the like. In particular, when the external electrode 20 includes a metal layer, the resin binder contained in the base 10 is joined to the metal layer, which may further reduce adhesion between the two.

[0043] In contrast, in the embodiment of the present disclosure, as shown in FIG. 4 , ceramic particles 50 are provided between the base 10 and the external electrode 20 so that the ceramic particles and the external electrode 20 are in contact with the surface IF of the base 10. More specifically, the coil device 1 has a first portion P1 where the base 10 and the external electrode 20 are in contact with each other and a second portion P2 where the ceramic particles 50 are interposed between the base 10 and the external electrode 20, and a plurality of the first portions P1 are scattered. That is, the ceramic particles 50 are dispersed along the surface IF of the base 10, and the portions of the ceramic particles outside the surface IF that are not in contact with the surface IF of the base 10 are covered by the external electrode 20. In this embodiment, the presence of such ceramic particles 50 enhances adhesion between the ceramic particles 50 and the external electrode 20, making it difficult for the external electrode 20 to come off the base 10. One reason for this effect is thought to be that the ceramic particles 50 bite into at least the external electrode 20, thereby providing an anchoring effect, as shown in FIG. 5 . Furthermore, when an external force is applied to the external electrode 20, it is usually more likely to be applied in a direction along the surface of the external electrode 20, that is, in a direction along the surface of the external electrode 20 or in a direction along the surface of the base 10, rather than in the thickness direction of the external electrode 20. In this embodiment, since the ceramic particles 50 are scattered along the surface IF, the adhesion strength is particularly high against a force applied in a direction along the surface, for example, in the shear direction, and the external electrode 20 is less likely to come off the base 10.

[0044] In this specification, the term "scattered" ceramic particles 50 refers to the ceramic particles 50 being present at intervals in the planar direction. In this case, primary particles of the ceramic particles do not necessarily need to be present at intervals; it is sufficient that primary particles or aggregates of primary particles are present at intervals. Furthermore, the term "dispersed along the surface IF" refers to the ceramic particles being aligned along the surface IF but not aligned in the direction intersecting the surface IF. Thus, each ceramic particle 50 between the substrate 10 and the external electrode 20 is in contact with both the substrate 10 and the external electrode 20. Furthermore, in the first portion P1 (FIG. 4) where no ceramic particles 50 are present, the material of the substrate 10 and / or the external electrode 20 may fill the spaces between the ceramic particles 50. In other words, the ceramic particles 50 may be surrounded by the material of the substrate 10 and / or the external electrode 20. Furthermore, it is preferable that the ceramic particles 50 are substantially absent from the substrate 10 and / or the external electrode 20.

[0045] To improve the adhesion between the base and the external electrodes, it is possible to bond the base and the external electrodes by interposing an adhesive layer between them. However, when manufacturing small coil components, it is difficult to accurately form an adhesive layer in a predetermined area on the surface of the base. Furthermore, many adhesives are prone to deterioration due to environmental changes. As a result, the adhesive may not be able to withstand the temperature of the firing process during the coil component manufacturing process, or may lose its function or adversely affect the function of the coil component due to changes in the usage environment. Such problems do not occur in the present embodiment, in which the base 10 and the external electrodes 20 are directly bonded.

[0046] The material of the ceramic particles 50 present between the substrate 10 and the external electrode 20 is not particularly limited, but may be one or more selected from metal oxides, nitrides, oxynitrides, and carbides. Of these, metal oxides are preferred. This is thought to be because metal oxides can expose oxygen atoms on the surface of the ceramic particles 50, forming chemical bonds with the resin contained in the substrate 10 and, optionally, the resin material contained in the external electrode 20. The chemical bond may be, more specifically, an intermolecular bond, more specifically, van der Waals forces and / or hydrogen bonds. The ceramic particles 50 may be one or more selected from aluminum oxide, silicon oxide, titanium oxide, and zirconium oxide. Of these, aluminum oxide and silicon oxide are preferred, as they have a small central atomic radius of the metal and are thought to have a high proportion of exposed oxygen atoms on the surface of the ceramic particles 50. In this embodiment, the presence of such ceramic particles 50 enhances adhesion between the substrate 10 and the ceramic particles 50 due to the bond between the resin contained in the substrate 10 and the ceramic particles 50, making it less likely for the external electrode 20 to come off the substrate 10. According to this embodiment, even if the base 10 has a surface on which a large amount of resin 11 is present, adhesion to the external electrode 20 can be obtained. For example, the effect can be obtained even if the surface area of ​​the base 10 is taken as 100% and the area ratio of the exposed metal magnetic particles 15 on this surface is 20% or less. In other words, a coil component produced in this manner can have a large amount of resin 11 present on the surface of the base 10, and the insulation resistance of the base 10 is high.

[0047] As described above, the external electrode 20 may include a metal layer or a conductive resin layer, and therefore, when the external electrode 20 contains a resin material as described above, this refers to when the external electrode 20 includes a conductive resin layer.

[0048] The average particle size of the ceramic particles 50 may be preferably 0.1 μm or more and 10 μm or less, more preferably 0.5 μm or more and 5 μm or less. When the average particle size of the ceramic particles 50 is 0.1 μm or more, the above-mentioned anchoring effect can be fully exerted. Furthermore, when the average particle size of the ceramic particles 50 is 10 μm or less, the specific surface area is increased, which increases the number of contact points with the resin contained in the base 10 and, in some cases, the resin material contained in the external electrode 20, thereby facilitating the formation of the above-mentioned chemical bond. Furthermore, the ceramic particles 50 do not hinder the external electrode 20 from being thinned.

[0049] Furthermore, it is preferable that the particle size distribution based on the area of ​​the particle major axis diameter is determined by the image analysis method described above, and that the maximum diameter of the ceramic particles 50 is 10 μm or less. This prevents the ceramic particles 50 from affecting the thickness of the external electrode 20, making it impossible to make the external electrode 20 thinner.

[0050] Furthermore, it is preferable that the average particle size of the ceramic particles 50 is smaller than the average particle size of the metal magnetic particles 15 contained in the base 10. This allows the ceramic particles 50 to adhere to or penetrate into areas of the base 10 where the resin 11 is reliably present on the surface. Furthermore, during the step of providing the ceramic particles 50 in the manufacturing process of the coil component 1, the ceramic particles 50 are prevented from colliding with the base 10 and causing the metal magnetic particles 15 to detach from the base 10.

[0051] The ratio (dc / dm) of the average particle size dc of ceramic particles 50 to the average particle size dm of metal magnetic particles 15 may preferably be 0.1 or more and 0.5 or less, and more preferably 0.2 or more and 0.4 or less.

[0052] The shape of the ceramic particles 50 is not particularly limited, but a non-spherical shape is preferred. Furthermore, the shape of the ceramic particles 50 preferably has corners or sharp portions, as shown in FIG. 4, for example, and more preferably has acute angles. In this specification, whether the shape of the ceramic particles 50 "has corners" can be determined by image analysis of the ceramic particles 50. For example, an image of a cross section taken along a direction perpendicular to the interface between the substrate 10 and the external electrode 20, such as an SEM image, is taken, the shape of the ceramic particles 50 in the cross section is extracted, and the contour of the ceramic particles 50 is observed. If there is a location where the slope of the tangent to the contour is discontinuous, it can be determined that a corner exists. Furthermore, if the angle of the corner of the contour of the ceramic particles 50 is less than 90°, the shape of the ceramic particles 50 can be determined to "have acute angles."

[0053] The corners in the shape of the ceramic particles 50 increase the specific surface area of ​​the ceramic particles 50, thereby increasing the number of chemical bonding points with the resin contained in the base 10 and, in some cases, with the resin material contained in the external electrode 20. Furthermore, the corners are more likely to penetrate into the external electrode 20 in the thickness direction of the external electrode 20 and also into the base 10 (described later with reference to FIG. 6), thereby improving the anchor effect described above. Furthermore, as the ceramic particles 50 penetrate into either the base 10 or the external electrode 20, gaps are less likely to form between the base 10 and the external electrode 20 around the ceramic particles 50. This further improves the adhesion between the base 10 and the external electrode 20.

[0054] The ceramic particles 50 preferably have a shape with flat surfaces, such as a polyhedron, in which case ridges are formed on the surfaces of the shape, forming corners that make it easier for the particles to bite into the external electrode 20 and / or the base 10, making it easier to achieve the anchoring effect described above.

[0055] The ceramic particles 50 are preferably crushed particles, i.e., particles produced by crushing, grinding, or cutting. The crushed particles usually have angular or sharp corners, which improves the adhesion between the substrate 10 and the external electrode 20, as described above.

[0056] Furthermore, the area ratio of the ceramic particles 50 in a cross section taken along the surface IF of the substrate 10, i.e., the ratio of the total area occupied by the ceramic particles 50 to the area of ​​the observed plane, may be preferably 10% to 50%, more preferably 20% to 35%. This area ratio can also be considered as the ratio of the area of ​​the portion where the ceramic particles 50 are present in a plan view, with the area of ​​the surface of the substrate 10 on which the external electrode 20 is provided being 100%. Having this area ratio of 10% or more ensures a sufficient anchoring effect. Having an area ratio of 50% or less prevents excessive crowding of the ceramic particles 50, ensures a good distribution of the ceramic particles 50, and allows the entire periphery of the ceramic particles 50 to adhere to the materials of the substrate 10 and the external electrode 20, thereby improving adhesion between the substrate 10 and the external electrode 20.

[0057] The occupied area ratio can be determined, for example, in the same manner as described for measuring and calculating the average particle diameter, by taking an image of a cross section, such as an SEM image, of the substrate 10 on which the external electrode 20 is provided, along a direction perpendicular to the surface IF, and calculating the total length of the ceramic particles 50 in the direction along the surface IF at the position of the surface IF in an observation area of ​​the cross section, and then calculating the ratio to the length of the observation area. In other words, the ratio (%) of the total length of the ceramic particles 50 along the surface IF can be determined when the length of the observation area is taken as 100%.

[0058] When the external electrode 20 is a conductive resin layer, i.e., a layer of a composite material in which conductive particles such as metal particles are dispersed in a resin, the conductive particles and resin material are as described above. Here, the resin material contained in the conductive resin is preferably a resin material having a hydroxyl group or a group capable of generating a hydroxyl group in its molecule, from the viewpoint of easily forming chemical bonds with the ceramic particles 50 and improving adhesion to the substrate 10. Specific examples of resin materials contained in the conductive resin include epoxy resin, phenolic resin, and acrylic resin, but epoxy resin is preferred. Furthermore, from the viewpoint of ensuring heat resistance of the coil component 1, for example, heat resistance above 100°C, a material having heat resistance of 150°C or higher is preferred.

[0059] Therefore, from the viewpoint of improving the adhesion between the base 10 and the external electrode 20, it is preferable that the ceramic particles 50 contain at least one of aluminum oxide and silicon oxide particles, and that the resin material contained in the conductive resin is an epoxy resin. Furthermore, since this increases the adhesion between the base 10 and the external electrode 20, it is also preferable that the resin binder contained in the base 10 is an epoxy resin.

[0060] FIG. 6 shows a modified example of FIG. 4 . In the configuration shown in FIG. 6 , the ceramic particles 50 penetrate into the resin 11 of the substrate 10. As a result, the ceramic particles 50 are arranged between the substrate 10 and the external electrode 20 in the thickness direction of the external electrode 20, straddling the position of the surface IF. This allows the ceramic particles 50 to exert an anchoring effect not only on the external electrode 20 side but also on the substrate 10 side, further improving the adhesion strength between the substrate 10 and the external electrode 20, which is preferable. This configuration in which the substrate 10 is recessed from the surface IF can be obtained by using a sandblasting device or the like to impart kinetic energy to the ceramic particles 50 and cause them to collide with the surface of the substrate 10 in the step of adhering the ceramic particles 50 (described later, S20). In this case, spraying may be performed on each individual substrate 10, or multiple substrates 10 may be arranged so that the surfaces to which the ceramic particles 50 are to be attached are exposed, and the ceramic particles 50 may be sprayed toward those surfaces.

[0061] <Manufacturing method for coil components> Further, a description will be given below of a method for manufacturing the above-mentioned coil component 1. The method for manufacturing a coil component according to one embodiment may include a base formation step (S10) of forming a base 10 containing metal magnetic particles 15 and resin 11 and having a coil conductor 30 provided therein, as described above, a ceramic particle attachment step (S20) of attaching ceramic particles 50 to the surface of the base 10, and an external electrode formation step (S30) of forming external electrodes 20 on top of the ceramic particles 50.

[0062] In the base formation step (S10), for example, a portion of the base 10, i.e., a first base portion 16 (FIG. 3), is formed (S11). The portion of the base 10 can be formed by compression molding. More specifically, a slurry, granules, or pellets obtained by kneading a composite magnetic material containing a plurality of metal magnetic particles and a resin to form the base 10 are poured into a first molding die, and molding pressure is applied to the composite magnetic material in the first molding die at a temperature equal to or higher than the thermosetting temperature of the resin. The slurry to form the base 10 may contain inorganic particles. A first base portion 16 of the base containing metal magnetic particles and a resin is obtained.

[0063] Next, the coil conductor 30 prepared in advance is placed on the first base portion 16 (S12). The coil conductor 30 may be produced by winding a metal strip around a core bar using a known winding machine such as a spindle-type winding machine.

[0064] Next, the first base portion 16 with the coil conductor 30 disposed thereon is placed in a second molding die to form a second base portion 17 (FIG. 3) of the base 10 (S13). More specifically, a composite magnetic material containing metal magnetic particles and resin that will become the second base portion 17 is poured into the second molding die, and molding pressure is applied to the second molding die. This produces a structure that includes the first base portion 16 and a green body in which the coil conductor 30 is embedded inside the second base portion 17. The composite magnetic material used to form the second base portion 17 may be the same as or different from the composite magnetic material used to form the first base portion 16.

[0065] The obtained molded body is hardened into a resin by heat treatment, and the surface of the hardened molded body is polished so that the first lead portion 32a and the second lead portion 32b of the coil conductor 30 are exposed (S14), thereby forming the base body 10.

[0066] At least one of the steps of forming the first substrate portion 16 (S11) and the second substrate portion 17 (S13) may be formed by warm molding or sheet molding instead of compression molding.

[0067] The specific method for the ceramic particle attachment step (S20) is not particularly limited, but can be performed, for example, by barrel processing. Barrel processing is a processing method performed by loading the substrate 10 and ceramic particles into a barrel device and rotating or shaking the barrel, or stirring the contents of the barrel device. The ceramic particle attachment step (S20) can also be performed by spraying ceramic particles onto the substrate 10 using a sandblasting device or the like, causing them to collide. In this way, by applying kinetic energy to the ceramic particles to attach them to the substrate 10, the surface of the resin contained in the substrate 10 is recessed, allowing the ceramic particles to penetrate into the resin of the substrate 10. This makes it possible to obtain the configuration described with reference to FIG. 6, thereby improving the adhesion strength between the substrate 10 and the external electrode 20.

[0068] The conditions of the ceramic particle adhering step (S20) can be adjusted so that the amount of ceramic particles 50 adhering to the surface of the base 10 is such that the area ratio of the ceramic particles 50 on the surface IF of the base 10 in the coil component 1 is 10% or more and 50% or less.

[0069] After the ceramic particle attachment step (S20), in the external electrode formation step (S30), a first external electrode 20a and a second external electrode 20b are formed on the ceramic particles attached to the surface of the base 10. The first external electrode 20a can be formed so as to be electrically connected to the first lead portion 32a of the coil conductor 30, and the second external electrode 20b can be formed so as to be electrically connected to the end of the second lead portion 32b of the coil conductor 30. As described above, the external electrodes 20 may include a metal layer or a conductive resin layer.

[0070] Although specific embodiments have been described above in detail, the present disclosure is not limited to the above embodiments. Furthermore, the above embodiments can be subject to various changes, modifications, substitutions, additions, deletions, and combinations within the scope of the claims.

[0071] Aspects of the present disclosure are, for example, as follows.

[0072] <1> a base body containing metal magnetic particles and a resin; a coil conductor provided inside the base body; and an external electrode provided on a surface of the base body so as to be electrically connected to the coil conductor; ceramic particles provided between the substrate and the external electrode; A coil component having:

[0073] <2> The ceramic particles have an average maximum particle size of 0.1 μm or more and 10 μm or less. <1> The coil component according to claim 1.

[0074] <3> the ceramic particles have an average particle size smaller than the average particle size of the metal magnetic particles; <1> or <2> The coil component according to claim 1.

[0075] <4> The ceramic particles have an abundance ratio of 10% to 50% when the area of ​​the surface of the base on which the external electrodes are provided is taken as 100%. <1> from <3> The coil component according to any one of the above items.

[0076] <5> the external electrodes include at least one of a metal layer and a conductive resin; <1> from <4> The coil component according to any one of the preceding claims.

[0077] <6> The ceramic particles have corners as their outer shapes. <1> from <5> The coil component according to any one of the preceding claims.

[0078] <7> the external electrode has a recess on a surface facing the base body, the recess extending along the ceramic particles; <1> from <6> The coil component according to any one of the preceding claims. [Explanation of symbols]

[0079] 1 Coil parts 2 Circuit Boards 2a Mounting board 3a, 3b Land section 10 Base 10a 1st main surface (top surface) 10b 2nd principal surface (bottom surface) 10c 1st end face 10d 2nd end face 10e First Side 10f 2nd side 11 Resin 15 Metal magnetic particles 16 1st base part 17 Second base part 20 External electrode 20a 1st external electrode 20b 2nd external electrode 30 Coil conductor 31 Orbital Club 32 Drawer section 32a 1st drawer 32b 2nd drawer 50 ceramic particles IF substrate surface

Claims

1. a substrate containing metal magnetic particles and a resin; a coil conductor provided inside the base; an external electrode provided on the surface of the base body so as to be electrically connected to the coil conductor; ceramic particles provided between the substrate and the external electrode; A coil component having:

2. 2. The coil component according to claim 1, wherein the ceramic particles have an average maximum particle size of 0.1 μm or more and 10 μm or less.

3. 3. The coil component according to claim 1, wherein the ceramic particles have an average particle size smaller than that of the metal magnetic particles.

4. 3. The coil component according to claim 1, wherein the ceramic particles account for 10% to 50% of the area of ​​the surface of the base on which the external electrodes are provided, assuming that the area is 100%.

5. The coil component according to claim 1 , wherein the external electrodes include at least one of a metal layer and a conductive resin layer.

6. The coil component according to claim 1 or 2, wherein the ceramic particles have corners as their outer shapes.

7. 3. The coil component according to claim 1, wherein the external electrodes have recesses on the surfaces facing the base body, the recesses extending along the ceramic particles.

Images