Composite magnetic particles containing metal magnetic particles

Abstract

The present invention provides composite magnetic particles containing metal magnetic particles. The composite magnetic particles of one embodiment of the present invention include: a first metal magnetic particle coated with a first resin portion composed of a first resin material; and a second metal magnetic particle bonded to the first metal magnetic particle via a second resin portion, wherein the particle size of the second metal magnetic particle is smaller than that of the first metal magnetic particle, and the second resin portion is composed of a second resin material with a molecular weight greater than that of the first resin material.

Description

Technical Field

[0001] The present invention relates to composite magnetic particles containing metal magnetic particles, electronic components containing a magnetic matrix formed of the composite magnetic particles, and methods for producing the same. Background Art

[0002] Various magnetic materials have been used in electronic components such as inductors. An inductor typically includes a magnetic base made of a magnetic material, a coil conductor embedded in the magnetic base, and an external electrode connected to an end of the coil conductor.

[0003] As a material for the magnetic matrix of the electronic component, composite magnetic particles having a resin insulating film formed on the surface of metal magnetic particles are used. Such a magnetic matrix can be produced, for example, by injecting a slurry obtained by kneading the composite magnetic particles and a binding material into a mold and pressurizing the slurry in the mold.

[0004] The magnetic matrix used in electronic components such as inductors is required to have a high magnetic permeability, and schemes for improving the magnetic permeability of the magnetic matrix have been proposed. For example, Japanese Patent Publication No. 2018-041955 (Patent Document 1) discloses a composite magnetic particle having: a magnetic core powder formed of a magnetic material; and a resin layer coating the surface of the magnetic core powder. The resin layer is a single layer composed of a polymer material, and therefore can provide an insulating function, an adhesive function, and a curing agent function. According to Patent Document 1, the resin layer is arranged in direct contact with the magnetic core powder, so there is no restriction on the magnetic material that can be used as the magnetic core powder, and thus an inductor with high magnetic permeability can be provided.

[0005] Patent document 1 also discloses that the filling rate (filling density) of magnetic particles in a magnetic matrix is ​​increased by using magnetic particles having two or more average particle sizes in a magnetic matrix, thereby increasing the magnetic permeability of the magnetic matrix. Japanese Patent Publication No. 2010-034102 (Patent Document 2) also discloses that the filling rate (filling density) of magnetic particles in a magnetic matrix is ​​increased by mixing two or more metal magnetic particles having different average particle sizes.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-041955

[0009] Patent Document 2: Japanese Patent Application Publication No. 2010-034102 Summary of the invention

[0010] Technical problem to be solved by the invention

[0011] Composite magnetic particles comprising metal magnetic particles and a resin film formed on the surface of the metal magnetic particles can be produced by using the mixing function of various mills such as a bead mill or a ball mill. Specifically, by using the mixing function of the mill to mix the metal magnetic particles and the resin composition, metal magnetic particles having a resin film formed on the surface can be obtained. However, when two or more metal magnetic particles with different particle sizes are mixed with the resin composition, there is a problem that the metal magnetic particles with a small particle size are easily condensed because the resin composition acts as a primer.

[0012] When a magnetic matrix is ​​made of composite magnetic particles in which metal magnetic particles with small particle sizes are agglomerated, the distribution of the metal magnetic particles in the magnetic matrix will be biased (biased to one side). Specifically, the metal magnetic particles with small particle sizes will be biased to exist in a certain part of the magnetic matrix. As a result, the presence ratio of metal magnetic particles with large particle sizes increases in other parts of the magnetic matrix.

[0013] The magnetic flux generated when current is applied to the coil preferentially passes through the path where the metal magnetic particles with large particle sizes have a high abundance ratio. Therefore, when the metal magnetic particles with small particle sizes aggregate in the magnetic matrix, the magnetic flux distribution in the magnetic matrix becomes uneven. Therefore, when the DC current flowing in the coil conductor in the coil component increases, magnetic saturation occurs sequentially from the magnetic path where the metal magnetic particles with large average particle sizes have a high abundance ratio among the multiple magnetic paths of the magnetic flux passing through the magnetic matrix.

[0014] Thus, when a magnetic matrix formed of composite magnetic particles in which metal magnetic particles with small particle sizes are agglomerated is used for a coil component, local magnetic saturation occurs due to the uneven distribution of magnetic flux in the magnetic matrix, and therefore, when the DC current applied to the coil is increased, the inductance gradually decreases. Therefore, in a coil component including a magnetic matrix formed of composite magnetic particles in which metal magnetic particles with small particle sizes are agglomerated, it is difficult to increase the allowable current.

[0015] Moreover, when the metal magnetic particles are condensed, the adjacent metal magnetic particles become easily in electrical contact with each other. When multiple adjacent metal magnetic particles are in electrical contact with each other, the multiple metal magnetic particles will electromagnetically become one particle with a large particle size. The larger the particle size of the metal particles in the changing magnetic field, the easier it is to generate large eddy currents. Therefore, when a magnetic matrix formed by composite magnetic particles in which metal magnetic particles with a small particle size are condensed is used for a coil component, there is a problem of increased eddy current loss.

[0016] The object of the present invention is to solve or alleviate at least part of the above-mentioned problems. One of the more specific objects of the present invention is to provide a composite magnetic particle capable of suppressing the agglomeration of metal magnetic particles. Another object of the present invention is to provide an electronic component comprising a magnetic matrix formed by composite magnetic particles capable of suppressing the agglomeration of metal magnetic particles. Yet another object of the present invention is to provide a method for manufacturing the above-mentioned composite magnetic particles and electronic components. Other objects of the present invention will become clear from the description of the entire specification.

[0017] Means for solving technical problems

[0018] A composite magnetic particle of one embodiment of the present invention includes: a first metal magnetic particle, which is coated with a first resin portion composed of a first resin material; and a second metal magnetic particle, which is bonded to the first metal magnetic particle via the second resin portion, wherein the particle size of the second metal magnetic particle is smaller than that of the first metal magnetic particle, and the second resin portion is composed of a second resin material with a molecular weight larger than that of the first resin material.

[0019] The entire surface of the first metal magnetic particle may be covered with the first resin portion.

[0020] A magnetic substrate according to one embodiment of the present invention includes the above-mentioned composite magnetic particles.

[0021] A magnetic matrix according to one embodiment of the present invention comprises: a plurality of first metal magnetic particles coated with a first resin portion formed of a first resin material; and a plurality of second metal magnetic particles having a second average particle size smaller than the first average particle size, wherein the first average particle size is the average particle size of the plurality of first metal magnetic particles, and each of the second metal magnetic particles is coated with a second resin portion formed of a second resin material, and is bonded to at least one of the plurality of first metal magnetic particles via at least one of the first resin portion and the second resin portion, and when a cross section of the magnetic matrix is ​​measured at a magnification of 2000 times using a scanning electron microscope (SEM), when observing adjacent groups of the first metal magnetic particles, a proportion of groups of the second metal magnetic particles that do not exist between adjacent first metal magnetic particles is less than 15%.

[0022] An electronic component according to one embodiment of the present invention includes a magnetic matrix formed of the composite magnetic particles described above. The electronic component may include a coil provided on the magnetic matrix. The electronic component is, for example, an inductor.

[0023] A method for manufacturing composite magnetic particles according to one embodiment of the present invention includes: a coating step of forming a first resin portion composed of a first resin material on the surface of a first metal magnetic particle; and a bonding step of bonding a second metal magnetic particle to the first metal magnetic particle via the second resin portion, wherein the particle size of the second metal magnetic particle is smaller than that of the first metal magnetic particle, and the second resin portion is composed of a second resin material having a molecular weight greater than that of the first resin material.

[0024] The bonding step may include: forming the second resin portion on a surface of the first resin portion; and mixing the first metal magnetic particles having the second resin portion formed thereon with the second metal magnetic particles.

[0025] The bonding step may include: a step of mixing the first metal magnetic particles having the first resin portion formed thereon with the second metal magnetic particles to obtain mixed particles; and a step of mixing the mixed particles with a resin composition composed of the second resin material.

[0026] The molecular weight of the second resin material may be at least twice the molecular weight of the first resin material.

[0027] The content of the first resin part may be 0.01 wt % to 0.1 wt % relative to 100 wt % of the second resin part.

[0028] Effects of the Invention

[0029] According to the present invention, it is possible to provide composite magnetic particles capable of suppressing aggregation of metal magnetic particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a diagram schematically showing a composite magnetic particle according to one embodiment of the present invention.

[0031] Figure 2A This is a diagram schematically showing a part of the production process of the composite magnetic particles according to one embodiment of the present invention.

[0032] Figure 2B This is a diagram schematically showing a part of the production process of the composite magnetic particles according to one embodiment of the present invention.

[0033] Figure 2C This is a diagram schematically showing a part of the production process of the composite magnetic particles according to one embodiment of the present invention.

[0034] Figure 2D This is a diagram schematically showing a part of the production process of the composite magnetic particles according to one embodiment of the present invention.

[0035] Figure 3 This is a perspective view of a coil component according to one embodiment of the present invention.

[0036] Figure 4 It is a schematic representation of the use of II line to Figure 3 FIG. 5 is a diagram of a cross section obtained by cutting a coil component.

[0037] Figure 5 It is a schematic representation of the shooting Figure 4 Schematic diagram of an image obtained by taking a portion of a cross section.

[0038] Figure 6 This is a perspective view of a coil component according to another embodiment of the present invention.

[0039] Figure 7 It is a schematic representation of the II-II line. Figure 6 FIG. 5 is a diagram of a cross section obtained by cutting a coil component.

[0040] Figure 8 This is a perspective view of a coil component according to another embodiment of the present invention.

[0041] Description of Reference Numerals

[0042] 1 Composite magnetic particles

[0043] 2a First metal magnetic particle

[0044] 2b Second metal magnetic particle

[0045] 3. The first resin part

[0046] 4 Second resin part

[0047] 10, 220, 310 magnetic substrate

[0048] 25, 225 Coil conductor

[0049] 101, 210, 301 coil parts DETAILED DESCRIPTION

[0050] Reference Figure 1 A composite magnetic particle 1 according to an embodiment of the present invention is described. The composite magnetic particle 1 can be used as a material of a magnetic matrix of an electronic component described later. The composite magnetic particle 1 according to an embodiment of the present invention includes: a first metal magnetic particle 2a coated with a first resin portion 3; and a plurality of second metal magnetic particles 2b bonded to the first metal magnetic particle 2a via a second resin portion 4.

[0051] In one embodiment, the first metal magnetic particles 2a and the second metal magnetic particles 2b are formed of a crystalline or amorphous metal or alloy containing at least one element of iron (Fe), nickel (Ni) and cobalt (Co). The metal magnetic particles may also contain at least one element of silicon (Si), chromium (Cr) and aluminum (Al). The metal magnetic particles may be pure iron particles composed of Fe and inevitable impurities, or they may be Fe-based amorphous alloys containing iron (Fe). The Fe-based amorphous alloys include, for example, Fe-Si alloys, Fe-Si-Al alloys, Fe-Si-Cr-B alloys, Fe-Si-BC alloys and Fe-Si-PBC alloys. On the surface of the first metal magnetic particles 2a and the second metal magnetic particles 2b, an oxide film obtained by oxidation of the alloy or metal may be attached. In the case where an oxide film is attached to the surface of the first metal magnetic particles 2a and the second metal magnetic particles 2b, the unoxidized area on the inner side of the oxide film exhibits magnetism.

[0052] The first metal magnetic particles 2a have a larger particle size than the second metal magnetic particles 2b. In one embodiment, the particle size of the first metal magnetic particles 2a is 5 to 100 μm, and the specific surface area ratio (BET value) is 3 m 2 In one embodiment, the particle size of the second metal magnetic particles 2b is 0.05 to 50 μm, and the specific surface area ratio (BET value) is 15 m 2 / g or less. The shape of the first metal magnetic particle 2a and the second metal magnetic particle 2b is, for example, spherical. The shape of the first metal magnetic particle 2a and the second metal magnetic particle 2b is not limited to a spherical shape, and may be, for example, a flat shape. In the illustrated embodiment, the composite magnetic particle 1 includes a plurality of second metal magnetic particles 2b. The plurality of second metal magnetic particles 2b are bonded to the first metal magnetic particles 2a having the first resin portion 3 formed therein via the second resin portion 4, and therefore, aggregation of the plurality of second metal magnetic particles 2b is not likely to occur. Adjacent particles among the plurality of second metal magnetic particles 2b are preferably spaced apart from each other. In the case where the second resin portion 4 exists between adjacent second metal magnetic particles 2b, it can be determined that the adjacent second metal magnetic particles 2b are spaced apart from each other. Alternatively, a portion of the second metal magnetic particles 2b contained in the composite magnetic particle 1 may be in direct contact (not via the second resin portion 4) with adjacent second metal magnetic particles 2b.

[0053] In one embodiment, the thickness of the first resin portion 3 is 100 nm or less. The thickness of the first resin portion 3 can be determined in accordance with the particle size of the first metal magnetic particle 2a. In one embodiment, the first resin portion 3 formed on the surface of the first metal magnetic particle 2a is composed of a first resin material. The first resin material is a resin having a molecular weight smaller than that of the second resin material of the second resin portion 4, and has at least one of a hydrolyzable silyl group, a vinyl group, an epoxy group, an amino group, and a methacryloyl group. The first resin material may contain Si in the molecular skeleton. The first resin portion 3 is preferably arranged in a manner covering the entire surface of the first metal magnetic particle 2a. As the first resin material, a resin material with a small molecular weight having a fluidity to the extent that it can cover the entire surface of the first metal magnetic particle 2a is preferably used. The molecular weight of the first resin material and the molecular weight of the second resin material can be compared with each other by their respective average molecular weights. When comparing the molecular weight of the first resin material and the molecular weight of the second resin material, the respective number average molecular weights can be compared with each other. In this case, the number average molecular weight of the first resin material is smaller than the number average molecular weight of the second resin material. When comparing the molecular weight of the first resin material and the molecular weight of the second resin material, the respective weight average molecular weights can also be compared with each other. In this case, the weight average molecular weight of the first resin material is smaller than the weight average molecular weight of the second resin material. The number average molecular weight and the weight average molecular weight can be measured using HLC-8220GPC manufactured by Tosoh Corporation. As an analytical column, GMH XL and G3000H XL The analytical column can be selected to have the most suitable filler diameter for size exclusion chromatography (SEC) according to the type and molecular weight of the first resin and the second resin. The number average molecular weight and the weight average molecular weight can be expressed as polystyrene (PS) conversion values ​​measured by gel permeation chromatography (GPC).

[0054] The second resin portion 4 is formed on the outer surface of the first metal magnetic particle 2a formed with the first resin portion 3. The second resin portion 4 is provided in contact with the first resin portion 3. The second resin portion 4 is provided to cover a part or all of the second metal magnetic particle 2b. The entire surface of the second metal magnetic particle 2b may be covered by the second resin portion 4. Alternatively, a part of the surface of the second metal magnetic particle 2b may be covered by the second resin portion 4. The second metal magnetic particle 2b is bonded to the first metal magnetic particle 2a via the second resin portion 4.

[0055] In one embodiment, the second resin portion 4 is composed of a second resin material having a molecular weight greater than that of the first resin material. The second resin material is, for example, a mixed resin material obtained by mixing a phenolic resin in a cresol novolac type epoxy resin. The epoxy equivalent of the cresol novolac type epoxy resin is 200 to 250, the softening point is 50 to 100 degrees, the specific gravity is 1.15 to 1.30, and the OH equivalent of the phenolic resin is 100 to 120, and the softening point is 60 to 110 degrees. The mixing ratio of the cresol novolac type epoxy resin to the phenolic resin is, for example, 1:1. As the second resin material, it is not limited to a mixed resin material obtained by mixing a phenolic resin in a cresol novolac type epoxy resin. As the second resin material, any resin material having a molecular weight greater than that of the first resin material can be used. The molecular weight of the second resin material can be more than twice the molecular weight of the first resin material. The softening point of the second resin material can be a temperature that is 50°C or higher than the softening point of the first resin material.

[0056] In the composite magnetic particle 1 , the content of the first resin portion is 0.01 wt % to 10 wt % relative to 100 wt % of the second resin portion 4 .

[0057] It may be that, when the particle sizes of the first metal magnetic particle 2a and the second metal magnetic particle 2b are D1 and D2 respectively, the relationship between the particle size D1 of the first metal magnetic particle 2a and the particle size D2 of the second metal magnetic particle 2b satisfies D1 / D2≥3.

[0058] Next, refer to Figure 2A to Figure 2C A method for producing the composite magnetic particle 1 according to one embodiment of the present invention will be described.

[0059] First, a plurality of first metal magnetic particles 2a are prepared. Next, a coating process is performed. In the coating process, a first resin portion 3 composed of a first resin material is formed on the surface of each of the plurality of first metal magnetic particles. More specifically, a plurality of first metal magnetic particles 2a and a first resin solution containing a first resin material are placed in a mixing container and stirred to generate a mixture of the first metal magnetic particles 2a and the first resin material, and the mixture is taken out of the mixing container and dried. Thus, as Figure 2A As shown, the first metal magnetic particles 2a having the first resin portion 3 are obtained. In the coating process, for example, 0.01 wt% to 5 wt% of the first resin material is added to 100 wt% of the first metal magnetic particles 2a. A diluent such as 2-butanone may be added to the first resin solution as needed.

[0060] Next, a bonding process is performed. In this bonding process, the second metal magnetic particles 2b are bonded to the first metal magnetic particles 2a having the first resin portion 3 formed thereon via the second resin portion 4, wherein the second resin portion 4 is made of a second resin material. More specifically, the first metal magnetic particles 2a having the first resin portion 3 formed thereon and the second resin solution containing the second resin material are stirred in a mixing container, as shown in FIG. Figure 2B As shown, a second resin portion 4 made of a second resin material is formed on the surface of the first resin portion 3. In this bonding process, for example, 1 wt% to 20 wt% of the second resin material is added to 100 wt% of the first metal magnetic particles 2a. A diluent such as 2-butanone may be added to the second resin solution as needed.

[0061] Then, if Figure 2C As shown, the second metal magnetic particles 2b are further added to the mixing container, and the first metal magnetic particles 2a and the second metal magnetic particles 2b formed with the second resin portion 4 are stirred, so that, as shown in FIG. Figure 2D As shown, the second metal magnetic particle 2b is bonded to the first metal magnetic particle 2a via the second resin portion 4. In addition, by this stirring treatment, the second resin portion 4 is also formed on the surface of the second metal magnetic particle 2b. As described above, the second resin portion 4 may be formed on the entire surface of the second metal magnetic particle 2b, or may be formed on a portion of the surface of the second metal magnetic particle 2b. By taking out the mixture obtained in this way from the mixing container and drying it, a composite magnetic particle 1 can be obtained. The composite magnetic particle 1 obtained as described above includes: the first metal magnetic particle 2a coated with the first resin portion 3; and the second metal magnetic particle 2b bonded to the first metal magnetic particle 2a via the second resin portion 4. The composite magnetic particle 1 is sieved to become a granular form. The granular composite magnetic particle 1 can be used as a magnetic material for a magnetic substrate of an electronic component as described later.

[0062] Alternatively, in the bonding step, before the second resin solution is added, the first metal magnetic particles 2a and the second metal magnetic particles 2b having the first resin portion 3 are mixed in a mixing container to generate mixed particles, and the second resin solution is mixed in the mixed particles. The thus obtained mixture is taken out of the mixing container and dried to obtain the composite magnetic particles 1.

[0063] According to the above-mentioned manufacturing method, in the process of preparing the composite magnetic particle 1 including the first metal magnetic particle 2a and the second metal magnetic particle 2b, after the low molecular weight first resin portion 3 that easily functions as a primer is formed on the surface of the first metal magnetic particle 2a, the first metal magnetic particle 2a with the first resin portion 3 formed thereon is mixed with the second metal magnetic particle 2b. Thus, the aggregation of the second metal magnetic particles 2b caused by the primer function of the low molecular weight first resin material can be suppressed.

[0064] Furthermore, since the second metal magnetic particles 2 b are actively bonded to the first metal magnetic particles 2 a by the second resin portion 4 composed of the second resin material having a large molecular weight, aggregation of the second metal magnetic particles 2 b can be suppressed.

[0065] Next, refer to Figure 3 to Figure 5 An electronic component including a magnetic matrix formed of composite magnetic particles 1 will be described. In these figures, an inductor 101 is shown as an example of an electronic component including a magnetic matrix formed of composite magnetic particles 1. Figure 3 is a perspective view of an inductor 101 according to an embodiment of the present invention. Figure 4 It is a schematic representation of the use of II line to Figure 3 A cross-sectional view of the inductor 101 cut away, Figure 5 It means shooting Figure 4 Schematic diagram of an image obtained by viewing area A of the cross section.

[0066] In this specification, unless otherwise understood according to the context, the “length” direction, “width” direction, and “thickness” direction of the inductor 101 are respectively Figure 3 The "L", "W" and "T" directions.

[0067] Inductor 101 is an example of a coil component to which the present invention can be applied. In addition to being applicable to inductors, the present invention can also be applied to transformers, filters, reactors, and various other coil components. The present invention can more significantly exert its effect by being applied to coil components to which large currents are applied and electronic components other than these. The inductor used in a DC-DC converter is an example of a coil component to which large currents are applied. In addition to being applicable to inductors for DC-DC converters, the present invention can also be applied to coupled inductors, choke coils, and various other magnetically coupled coil components. As described later, the magnetic base 10 has high magnetic permeability and high insulation, and therefore, the inductor 101 has particularly excellent properties as a power supply type inductor. The use of the inductor 101 is not limited to the uses clearly described in this specification.

[0068] As shown in the figure, the inductor 101 includes: a magnetic matrix 10 formed by composite magnetic particles 1; a coil conductor 25 arranged in the magnetic matrix 10; an external electrode 21 electrically connected to one end of the coil conductor 25; and an external electrode 22 electrically connected to the other end of the coil conductor 25.

[0069] The magnetic substrate 10 is formed into a rectangular parallelepiped shape by a magnetic material. In one embodiment of the present invention, the magnetic substrate 10 is formed to have a length dimension (dimension in the L direction) of 1.0 mm to 2.6 mm, a width dimension (dimension in the W direction) of 0.5 mm to 2.1 mm, and a height dimension (dimension in the H direction) of 0.5 mm to 1.0 mm. The dimension in the length direction may also be 0.3 mm to 1.6 mm. The upper and lower surfaces of the magnetic substrate 10 may also be covered by a covering layer.

[0070] The illustrated inductor 101 is mounted on a circuit board 102. A pad portion 103 may be provided on the circuit board 102. When the inductor 101 includes two external electrodes 21 and 22, two pad portions 103 may be provided on the circuit board 102 corresponding thereto. The inductor 101 may also be mounted on the circuit board 102 by bonding the external electrodes 21 and 22 to the corresponding pad portions 103 on the circuit board 102, respectively. The circuit board 102 may be mounted in various electronic devices. Electronic devices in which the circuit board 102 may be mounted include smartphones, tablet computers, game consoles, and various other electronic devices. Therefore, the inductor 101 can be suitably used for the circuit board 102 in which components are mounted at a high density. The inductor 101 may also be a built-in component embedded inside the circuit board 102.

[0071] 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 are opposite to each other, the first end surface 10c and the second end surface 10d are opposite to each other, and the first side surface 10e and the second side surface 10f are opposite to each other.

[0072] exist Figure 3 In the embodiment, the first main surface 10a is located on the upper side of the magnetic substrate 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 inductor 101 is arranged so that the second main surface 10b faces the circuit board 102, and therefore, the second main surface 10b is sometimes referred to as the "mounting surface". When referring to the up and down directions of the inductor 101, the upper and lower directions are referred to as the "lower surface". Figure 3 The up and down direction is used as the reference.

[0073] The external electrode 21 is provided on the first end surface 10c of the magnetic base 10. The external electrode 22 is provided on the second end surface 10d of the magnetic base 10. Each external electrode may also extend to the lower surface of the magnetic base 10 as shown in the figure. The shape and configuration of each external electrode are not limited to the example shown in the figure. For example, both the external electrodes 21 and 22 may be provided on the lower surface 10b of the magnetic base 10. In this case, the coil conductor 25 may be connected to the external electrodes 21 and 22 provided on the lower surface 10b of the magnetic base 10 via a through-hole conductor. The external electrode 21 and the external electrode 22 are arranged at intervals from each other in the length direction.

[0074] Next, an example of a method for manufacturing the inductor 101 according to an embodiment of the present invention is described. Next, a method for manufacturing the inductor 101 using a compression molding process is described. When the inductor 101 is manufactured using a compression molding process, the method for manufacturing the inductor 101 includes: a molding process of compressing the composite magnetic particles 1 to form a molded body; and a heat treatment process of heating the molded body obtained by the above molding process. In the molding process, an adhesive may be added as needed. The adhesive may include a binding material for bonding the particles to each other, a lubricant for making the particles flow well, and a release agent for separating the mold from the molded body well.

[0075] In the molding process, composite magnetic particles 1 are prepared. Next, a pre-prepared coil conductor is set in the molding die, and the composite magnetic particles 1 are placed in the molding die provided with the coil conductor, and a molding body containing the coil conductor is obtained by applying molding pressure. The molding process can be performed by warm molding or cold molding. In the case of warm molding, molding is performed at a temperature that is lower than the thermal decomposition temperature of the first resin material, the second resin material, and the adhesive and does not affect the crystallization of the metal magnetic particles. For example, in warm molding, molding is performed at a temperature of 150°C to 400°C. The molding pressure is, for example, 40MPa to 120MPa. In order to obtain the desired filling rate, the molding pressure can be appropriately adjusted.

[0076] After the molded body is obtained in the molding process, the manufacturing method enters the heat treatment process. In the heat treatment process, the molded body obtained by the molding process is heat treated, and a magnetic matrix is ​​obtained by the heat treatment. By the heat treatment, an oxide film is formed on the surface of the composite magnetic particles 1, and adjacent composite magnetic particles 1 are bonded via the oxide film. In the case where the first resin material and the second resin material are thermosetting resins, the heat treatment is performed at the curing temperature of the resin, for example, 150°C to 200°C, for 30 minutes to 4 hours. In the case where the first resin material and the second resin material are thermally decomposable resins, the heat treatment process includes: a process of degreasing the molded body obtained by the molding process; and a process of heating the molded body subjected to the degreasing process in an oxidizing atmosphere. In the case where the first resin material is a thermally decomposable resin, the first resin material can be removed by the degreasing process. Similarly, in the case where the second resin material is a thermally decomposable resin, the second resin material can be removed by the degreasing process. In addition, in the case where a binder is added, the binder can also be removed by the degreasing process. The degreasing process can be performed independently of the heating process. The heating time in the heat treatment step is, for example, 20 minutes to 120 minutes, and the heating temperature is, for example, 600°C to 900°C.

[0077] Next, by applying a conductor paste to both ends of the magnetic substrate 10 obtained as described above, an external electrode 21 and an external electrode 22 are formed. The external electrode 21 and the external electrode 22 are arranged to be electrically connected to one end of the coil conductor arranged in the magnetic substrate, respectively. The external electrode may include a plating layer. The plating layer may be more than two layers. The two-layer plating layer may include a Ni plating layer and a Sn plating layer arranged outside the Ni plating layer. Through the above process, an inductor 101 is obtained.

[0078] A schematic diagram of a cross section of the magnetic substrate 10 is shown in Figure 5 middle. Figure 5 The figure schematically shows a SEM photograph of a cross-section region A of the magnetic substrate 10 taken with a scanning electron microscope (SEM) at a magnification of 2000 times. As the scanning electron microscope, JSM-6700F manufactured by JEOL Ltd. can be used. The region A is an arbitrary region in the magnetic substrate 10 .

[0079] As shown in the figure, the magnetic matrix 10 includes a plurality of first magnetic metal particles 2a and a plurality of second metal magnetic particles 2b. The average particle size of the plurality of second metal magnetic particles 2b is smaller than the average particle size of the plurality of first magnetic metal particles 2a. The average particle size of the metal magnetic particles (e.g., the first metal magnetic particles 2a and the second metal magnetic particles 2b) contained in the composite magnetic particles 1 contained in the magnetic matrix 10 can be determined based on the particle size distribution obtained by obtaining the particle size distribution based on a SEM photograph, wherein the SEM photograph is a photograph obtained by cutting the magnetic matrix along its thickness direction (T direction) to expose the cross section and photographing the cross section at a magnification of 1000 to 3000 times using a scanning electron microscope (SEM). For example, the 50% value of the particle size distribution obtained based on the SEM photograph can be used as the average particle size of the metal magnetic particles. The average particle size of the first metal magnetic particles 2a in the magnetic matrix 10 is 10 to 30 μm, and the average particle size of the second metal magnetic particles 2b is 0.05 to 10 μm. The second metal magnetic particle 2b may have two or more peaks when the particle size distribution is prepared based on the SEM photograph. That is, the second metal magnetic particle 2b may be a mixed particle obtained by mixing two metal magnetic particles with different average particle sizes. The particle size of the metal magnetic particle with the smaller average particle size in the mixed particle is, for example, 0.05 to 5 μm, and its specific surface area ratio (BET value) is 50 m 2 In composite magnetic material 1, first resin portion 3 and second resin portion 4 can be distinguished from first metal magnetic particles 2a and second metal magnetic particles 2b based on the difference in brightness in a scanning electron microscope (SEM) photograph at about 10,000 to 40,000 times.

[0080] Each of the first magnetic metal particles 2a is coated with a first resin portion 3. Each of the second magnetic metal particles 2b is coated with a second resin portion 4. Each of the second magnetic metal particles 2b is bonded to the first magnetic metal particle 2a via at least one of the first resin portion 3 and the second resin portion 4. At least one of the first resin portion 3 and the second resin portion 4 exists between the first magnetic metal particle 2a and the plurality of second magnetic metal particles 2b located around it. Figure 5 In the embodiment, there are both the first resin portion 3 and the second resin portion 4 between the first metal magnetic particle 2a and the plurality of second metal magnetic particles 2b located around it. However, since the first resin portion 3 and the second resin portion 4 flow when manufacturing the magnetic matrix 10 (especially in the compression molding process), sometimes only one of the first resin portion 3 and the second resin portion 4 exists between the first metal magnetic particle 2a and the plurality of second metal magnetic particles 2b located around it. Figure 5In the SEM image, the boundary between the first resin portion 3 and the second resin portion 4 is clearly shown. However, in an actual SEM image, a part of the boundary between the first resin portion 3 and the second resin portion 4 may not be clearly seen.

[0081] Preferably, as shown in the figure, at least one second metal magnetic particle 2b exists between adjacent first metal magnetic particles 2a. When the first metal magnetic particles 2a and the second metal magnetic particles 2b flow during the compression molding process, sometimes in a part of the groups of adjacent first metal magnetic particles 2a, there are no second metal magnetic particles 2b between the adjacent first metal magnetic particles 2a. In one embodiment of the present invention, when observing 50 adjacent groups of first metal magnetic particles 2a, the proportion of groups in which there are no second metal magnetic particles 2b between adjacent first metal magnetic particles 2a is 15% or less. In cross-sectional observation using an SEM photograph, when there are no second metal magnetic particles 2b on the straight line connecting the geometric centers of gravity of adjacent first metal magnetic particles 2a, it can be judged that there are no second metal magnetic particles 2b between adjacent first metal magnetic particles 2a. Figure 5 In FIG. 1 , an imaginary line connecting the center of gravity of the first metal magnetic particle 2a disposed substantially in the center of the field of view and the center of gravity of each of the six first metal magnetic particles 2a adjacent to the first metal magnetic particle 2a is indicated by a dotted line. Since the second metal magnetic particle 2b is disposed on each of the six imaginary lines, it is determined that the second metal magnetic particle 2b exists between each of the six groups of the adjacent first metal magnetic particles 2a.

[0082] When the first resin material is a thermally decomposable resin, the first resin material may be removed during the manufacturing process. In this case, the first resin portion 3 is not included in the magnetic base 10. Similarly, when the second resin material is a thermally decomposable resin, the second resin material may be removed during the manufacturing process. In this case, the second resin portion 4 is not included in the magnetic base 10. Therefore, the first resin portion 3 and the second resin portion 4 may not be included in the SEM photograph of the magnetic base 10.

[0083] The scanning electron microscope magnification suitable for observing the distribution of the first metal magnetic particles 2a and the second metal magnetic particles 2b in the cross section of the magnetic substrate 10 is between 1000 times and 3000 times. When observing the cross section of the magnetic substrate 10, the scanning electron microscope magnification can be appropriately adjusted between 1000 times and 3000 times.

[0084] In region A, in addition to the first metal magnetic particles 2a, the second metal magnetic particles 2b, the first resin portion 3, and the second resin portion 4, a void may also be included. The void may also be filled with a resin other than the first resin portion 3 and the second resin portion 4. The resin filled in the void is, for example, a thermosetting resin having excellent insulating properties. As the thermosetting resin for the magnetic matrix 10, benzocyclobutene (BCB), epoxy resin, phenolic resin, unsaturated polyester resin, vinyl ester resin, polyimide resin (PI), polyphenylene ether resin (PPO), bismaleimide triazine cyanate resin, fumarate resin, polybutadiene resin, or polyvinyl benzyl ether resin may be used.

[0085] Next, refer to Figure 6 and Figure 7 Another embodiment of the coil component of the present invention is described below. As shown in the figure, the coil component 210 of one embodiment of the present invention includes: a magnetic substrate 220; a coil conductor 225 disposed in the magnetic substrate 220; an insulating plate 250 disposed in the magnetic substrate 220; and four external electrodes 221 to 224.

[0086] In one embodiment of the present invention, the magnetic matrix 220 includes the composite magnetic particle 1. The magnetic matrix 220 has a first main surface 220a, a second main surface 220b, a first end surface 220c, a second end surface 220d, a first side surface 220e, and a second side surface 220f. The outer surface of the magnetic matrix 220 is defined by these six surfaces.

[0087] The insulating plate 250 is a plate-shaped component formed of an insulating material. The insulating material used for the insulating plate 250 may be a magnetic material. The magnetic material used for the insulating plate 250 is, for example, a composite magnetic material containing a binding material and magnetic particles. In one embodiment of the present invention, the insulating plate 250 is configured to have a greater resistance value than the magnetic substrate 220. Thus, even if the insulating plate 250 is made thinner, electrical insulation between the coil conductor 225a and the coil conductor 225b can be ensured.

[0088] In the illustrated embodiment, the coil conductor 225 includes: a coil conductor 225a formed on the upper surface of the insulating plate 250; and a coil conductor 225b formed on the lower surface of the insulating plate 250. The coil conductor 225a is formed on the upper surface of the insulating plate 250 in a manner having a prescribed pattern, and the coil conductor 225b is formed on the lower surface of the insulating plate 250 in a manner having a prescribed pattern. An insulating film may also be provided on the surface of the coil conductor 225a and the coil conductor 225b. In the illustrated coil component 210, the coil conductor 225a and the coil conductor 225b are magnetically coupled. In the coil component 210, the coil conductor 225b may be omitted. In this case, the coil component 210 includes a coil conductor 225a provided on the upper surface of the insulating plate 250, but no coil conductor is provided on the lower surface of the insulating plate 250. The coil conductor 225 may take various shapes. For example, the coil conductor 225 has a spiral shape, a zigzag shape, a straight line shape, or a shape combined from these shapes when viewed from above.

[0089] A lead conductor 226a is provided at one end of the coil conductor 225a, and a lead conductor 227a is provided at the other end of the coil conductor 225a. The coil conductor 225a is electrically connected to the external electrode 221 via the lead conductor 226a, and is electrically connected to the external electrode 222 via the lead conductor 227a. Similarly, a lead conductor 226b is provided at one end of the coil conductor 225b, and a lead conductor 227b is provided at the other end of the coil conductor 225b. The internal conductor 228b of the coil conductor 225b is electrically connected to the external electrode 223 via the lead conductor 226b, and is electrically connected to the external electrode 224 via the lead conductor 227b.

[0090] In the illustrated embodiment, the external electrode 221 is electrically connected to one end of the coil conductor 225a, and the external electrode 222 is electrically connected to the other end of the coil conductor 225a. The external electrode 223 is electrically connected to one end of the coil conductor 225b, and the external electrode 224 is electrically connected to the other end of the coil conductor 225b. The external electrode 221 and the external electrode 223 are arranged on the first end surface 220c of the magnetic substrate 220. The external electrode 222 and the external electrode 224 are arranged on the second end surface 220d of the magnetic substrate 220. Each external electrode may also extend to the upper surface 220a and the lower surface 220c of the magnetic substrate 220 as shown in the figure. The shape and location of the external electrodes 221 to 224 may be appropriately changed.

[0091] Next, an example of a method for manufacturing the inductor 201 is described. First, an insulating plate formed into a plate shape by a magnetic material is prepared. Next, a photoresist is applied to the upper surface and the lower surface of the insulating plate, and then a conductor pattern is exposed and transferred to the upper surface and the lower surface of the insulating plate, respectively, and a development process is performed. Thus, a resist having an opening pattern for forming a coil conductor is formed on the upper surface and the lower surface of the insulating plate, respectively. The conductor pattern formed on the upper surface of the insulating plate is, for example, a conductor pattern corresponding to the above-mentioned coil conductor 225a, and the conductor pattern formed on the lower surface of the insulating plate is, for example, a conductor pattern corresponding to the above-mentioned coil conductor 225b. The coil conductor 225a and the coil conductor 225b can be produced by electrically connecting two or more coil patterns formed on two or more layers, for example, using through-hole conductors.

[0092] Next, each of the opening patterns is filled with a conductive metal by plating. Next, the resist is removed from the insulating plate by etching, thereby forming coil conductors on the upper and lower surfaces of the insulating plate.

[0093] Next, a magnetic matrix is ​​formed on both sides of the insulating plate on which the coil conductor is formed. The magnetic matrix corresponds to the magnetic matrix 220 described above. In order to form the magnetic matrix, a magnetic sheet is first made. The magnetic sheet can be made by kneading a particle group of composite magnetic particles 1 and a binder while heating to make a mixed resin composition, and placing the mixed resin composition in a sheet-shaped molding die to cool it. As a binder, for example, a resin having an average molecular weight smaller than that of the second resin material can be used. The addition of a binder can also be omitted. In the absence of a binder, the second resin material acts as a binder. By using a resin having a molecular weight smaller than that of the second resin material as a binder, the fluidity of the mixed resin composition is improved, and it is easy to fill the mixed resin composition into the molding die. Next, a laminate is made by arranging the coil conductor described above between a group of magnetic sheets thus made and applying pressure while heating. Next, the laminate is heat-treated at a curing temperature of the resin, for example, 150°C to 200°C for 30 minutes to 4 hours. Thus, a magnetic matrix having a coil conductor inside is obtained. The inductor 201 is manufactured by providing external electrodes at predetermined positions on the outer surface of the magnetic base.

[0094] Next, refer to Figure 8The coil component 301 of another embodiment of the present invention is described. The inductor 301 of one embodiment of the present invention is a winding type inductor. As shown in the figure, the coil component 301 includes a drum core 310, a winding 320, a first external electrode 331a and a second external electrode 332a. The drum core 310 has: a winding core 311; a rectangular parallelepiped flange 312a provided at one end of the winding core 311; and a rectangular parallelepiped flange 312b provided at the other end of the winding core 311. The winding 320 is wound on the winding core 311. The winding 320 is formed by covering the surrounding of a conductive wire made of a metal material with excellent conductivity with an insulating film. The first external electrode 331a is provided along the lower surface of the flange 312a, and the second external electrode 332a is provided along the lower surface of the flange 312b.

[0095] The drum core 310 is made of a magnetic material containing the above-mentioned composite magnetic particles 1. For example, the drum core 310 can be made by mixing the above-mentioned composite magnetic particles 1 with a lubricant, filling the mixed material into a mold cavity of a molding die for compression molding to make a powder compact, and sintering the powder compact. The drum core 310 can also be made by mixing the powder of the above-mentioned magnetic material or non-magnetic material with a resin, glass or insulating oxide (for example, Ni-Zn ferrite or silicon dioxide), molding the mixed material and curing or sintering it. The inductor 301 can be made by winding a winding 320 on the drum core 310, connecting one end of the winding 320 to the first external electrode 331a, and connecting the other end of the winding 320 to the second external electrode 332a.

[0096] Next, the effects of the above-mentioned embodiment are described. In one of the above-mentioned embodiments, in the process of producing the composite magnetic particle 1 including the first metal magnetic particle 2a and the second metal magnetic particle 2b, the second metal magnetic particle 2b is bonded to the first metal magnetic particle 2a, wherein a first resin portion 3 composed of a low molecular weight first resin material that easily functions as a primer is formed on the first metal magnetic particle 2a. Thus, the aggregation of the second metal magnetic particles 2b caused by the primer function of the low molecular weight first resin material can be suppressed. Moreover, the second metal magnetic particles 2b are actively bonded to the first metal magnetic particles 2a by the second resin portion 4 composed of the second resin material with a large molecular weight, thereby suppressing the aggregation of the second metal magnetic particles 2b.

[0097] In the above-mentioned embodiment, after the first metal magnetic particles 2a having the first resin portion 3 formed therein and the second resin solution containing the second resin material are stirred in a mixing container, the second metal magnetic particles 2b are added to the mixing container, so that the second metal magnetic particles 2b are mixed in the resin solution containing the second resin material having a high molecular weight. Thus, the second metal magnetic particles 2b can be prevented from agglomerating with each other.

[0098] In the above-mentioned embodiment, the first metal magnetic particles 2a and the second metal magnetic particles 2b formed with the first resin portion 3 are mixed in a mixing container to generate mixed particles, and the mixed particles are mixed with the second resin solution. In the process of generating the mixed particles, the adhesion of the second metal magnetic particles 2b to the first metal magnetic particles 2a can be promoted. Therefore, the aggregation of the second metal magnetic particles 2b can be suppressed.

[0099] In one embodiment described above, by allowing the second metal magnetic particles 2b to exist around the first metal magnetic particles 2a, the filling rate of the metal magnetic particles in the magnetic matrix can be increased. Moreover, by allowing the second metal magnetic particles 2b to exist around the first metal magnetic particles 2a, the biased existence (uneven distribution) of the first metal magnetic particles 2a in the magnetic matrix 10 can be suppressed. That is, the first metal magnetic particles 2a can be uniformly dispersed in the magnetic matrix 10. When the direct current flowing in the coil conductor 25 increases, magnetic saturation occurs sequentially from the magnetic circuits in which the existence ratio of the first metal magnetic particles 2a with a large particle size is high among the multiple magnetic circuits of the magnetic flux passing through the magnetic matrix. By suppressing the biased existence of the first metal magnetic particles 2a, the occurrence of local magnetic saturation can be suppressed.

[0100] The inductor 101 in the above embodiment can increase the filling rate of the metal magnetic particles in the magnetic base 10, thereby reducing the voids in the magnetic base 10. In particular, the water absorption rate of the magnetic base 10 in the above embodiment can be less than 2.0%, and can also be less than 1.0%.

[0101] The size, material and configuration of each component described in this specification are not limited to the contents clearly described in the embodiment, and each component can be deformed to have any size, material and configuration that can be included in the scope of the present invention. In addition, components that are not clearly described in this specification can be added to the described embodiments, and part of the described components can be omitted in each embodiment.

Claims

1. A composite magnetic particle, characterized in that: Include: first metal magnetic particles covered with a first resin portion composed of a first resin material; and The second metal magnetic particles are bonded to the first metal magnetic particles via a second resin portion, wherein the second metal magnetic particles have a smaller particle size than the first metal magnetic particles, and the second resin portion is composed of a second resin material with a molecular weight greater than that of the first resin material.

2. The composite magnetic particle according to claim 1, characterized in that: The molecular weight of the second resin material is at least twice the molecular weight of the first resin material.

3. The composite magnetic particle according to claim 1 or 2, characterized in that: The entire surface of the first metal magnetic particle is covered with the first resin portion.

4. A magnetic substrate, characterized in that: The composite magnetic particle comprises the composite magnetic particle according to any one of claims 1 to 3.

5. A magnetic substrate, characterized in that: Include: a plurality of first metal magnetic particles covered with a first resin portion composed of a first resin material; and a plurality of second metal magnetic particles having a second average particle size smaller than the first average particle size, wherein the first average particle size is the average particle size of the plurality of first metal magnetic particles, Each of the second metal magnetic particles is coated with a second resin portion made of a second resin material, and is bonded to at least one of the plurality of first metal magnetic particles via at least one of the first resin portion and the second resin portion. When a cross section of the magnetic matrix is ​​measured at 2000 times magnification using a scanning electron microscope, when adjacent groups of the first metal magnetic particles are observed, the proportion of groups of the second metal magnetic particles not existing between adjacent first metal magnetic particles is 15% or less.

6. An electronic component, characterized in that: Comprising the magnetic substrate as claimed in claim 4 or 5.

7. The electronic component according to claim 6, characterized in that: The invention comprises a coil arranged on the magnetic substrate.

8. A method for producing composite magnetic particles, characterized in that: include: A coating step of forming a first resin portion made of a first resin material on a surface of the first metal magnetic particle; and The bonding step bonds the second metal magnetic particles to the first metal magnetic particles via a second resin portion, wherein the second metal magnetic particles have a smaller particle size than the first metal magnetic particles, and the second resin portion is composed of a second resin material having a molecular weight greater than that of the first resin material.

9. The manufacturing method according to claim 8, characterized in that: The bonding process comprises: forming the second resin portion on the surface of the first resin portion; and and mixing the first metal magnetic particles having the second resin portion formed thereon with the second metal magnetic particles.

10. The manufacturing method according to claim 8, characterized in that: The bonding process comprises: a step of mixing the first metal magnetic particles having the first resin portion formed thereon with the second metal magnetic particles to obtain mixed particles; and A step of mixing the mixed particles with a resin composition composed of the second resin material.

11. The manufacturing method according to any one of claims 8 to 10, characterized in that: The molecular weight of the second resin material is at least twice the molecular weight of the first resin material.

12. The manufacturing method according to any one of claims 8 to 10, characterized in that: The content of the first resin part is 0.01 wt % to 0.1 wt % relative to 100 wt % of the second resin part.

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