Composite magnetic material

Abstract

The present invention provides a magnetic powder that is formed from magnetic particles (5). The magnetic particles (5) comprise a metal magnetic particle (1), a non-magnetic resin layer (3) that covers the surface of the metal magnetic particle (1), and an inorganic insulating material layer (2) that covers the non-magnetic resin layer (3).

Description

Technical Field

[0001] The present disclosure relates to magnetic powder and a composite magnetic material containing the magnetic powder.

Background Art

[0002] Conventionally, magnetic powder has been used as a magnetic material for cores of inductors and transformers. As cores using these magnetic materials, for example, there is a composite magnetic material obtained by compression molding a magnetic material. The composite magnetic material has a high saturation magnetic flux density and is an advantageous core for miniaturizing components such as inductors and transformers. In addition, since the composite magnetic material can be molded using a mold, the degree of freedom in the shape of the core is high, and even a complex shape can be manufactured with high precision in a simple process, so its usefulness has attracted attention.

[0003] For example, Patent Document 1 discloses a composite magnetic material using an iron-based soft magnetic powder composed of magnetic particles whose surfaces are treated with an inorganic insulating film.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In composite magnetic materials, it is required to improve the breakdown voltage in order to miniaturize inductors, transformers, etc. Improving the breakdown voltage means increasing the maximum value of the voltage that can be applied to the composite magnetic material without causing dielectric breakdown. To improve the breakdown voltage, it is important to enhance the insulation between the magnetic particles of the magnetic powder. For example, by forming an insulating film on the particle surface of the magnetic powder, the insulation between the particles of the magnetic powder can be enhanced. However, as in Patent Document 1, when an inorganic material is used for the insulating film, cracks may occur in the insulating film due to compression during the molding of the composite magnetic material. When cracks occur, dielectric breakdown is likely to occur, resulting in a decrease in the breakdown voltage. In addition, simply providing an insulating film containing such an inorganic material may not be sufficient to improve the breakdown voltage.

[0006] In view of the above problems, an object of the present disclosure is to improve the breakdown voltage of a composite magnetic material.

Means for Solving the Problems

[0007] The magnetic powder according to one aspect of the present disclosure is magnetic powder composed of magnetic particles, and the magnetic particles include metal magnetic particles, a non-magnetic resin layer covering the surface of the metal magnetic particles, and an inorganic insulating material layer covering the non-magnetic resin layer.

[0008] The composite magnetic material according to one aspect of the present disclosure includes the above magnetic powder and a non-magnetic resin member that binds between the magnetic particles of the magnetic powder.

Effects of the Invention

[0009] According to the present disclosure, the breakdown voltage of the composite magnetic material can be improved.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Figure 17

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0012] Note that each of the embodiments described below shows a specific example of the present disclosure. The numerical values, shapes, materials, components, arrangement positions of the components, connection forms, steps (processes), and the order of steps (processes), etc. shown in the following embodiments are merely examples and are not intended to limit the present disclosure. Among the components in the following embodiments, the components not described in the independent claims are described as optional components.

[0013] Also, each figure is a schematic diagram and is not necessarily drawn precisely. Therefore, for example, the scales in each figure do not necessarily match. In each figure, substantially the same configurations are denoted by the same reference numerals, and overlapping descriptions are omitted or simplified.

[0014] Also, in this specification, terms indicating the relationship between elements such as parallel or orthogonal, terms indicating the shape of elements such as rectangular or cuboid, and numerical ranges are not expressions representing only a strict meaning, but are expressions meaning substantially equivalent ranges, for example, including a difference of about several percent.

[0015] (Embodiment) Hereinafter, a magnetic powder according to an embodiment, a composite magnetic body including the magnetic powder, and a coil component including the composite magnetic body will be described.

[0016] [1-1. Configuration of Coil Component] FIG. 1 is a schematic perspective view showing the configuration of a coil component 10 according to the present embodiment. FIG. 2 is a cross-sectional view showing the configuration of the coil component 10 according to the present embodiment. FIG. 2 shows a cross-section taken along line II-II in FIG. 1.

[0017] As shown in FIGS. 1 and 2, the coil component 10 includes a composite magnetic body 12 and a coil member 23. Specifically, the coil component 10 is composed of a composite magnetic body 12 which is a magnetic core formed of a magnetic material containing magnetic powder, and a coil member 23 disposed inside the composite magnetic body 12. The coil component 10 is, for example, an inductor.

[0018] The composite magnetic body 12 has a columnar core portion 12a near the center in a plan view. A coil member 23 is disposed around the columnar core portion 12a of the composite magnetic body 12.

[0019] The coil member 23 has a winding portion 23a around which a conductor is wound a plurality of times, and a wiring portion 23b formed outside the composite magnetic body 12. The core portion 12a of the composite magnetic body 12 is disposed as the winding axis of the wound conductor of the winding portion 23a. The conductor is composed of, for example, copper. The conductor is composed of a material that is not destroyed by the heat applied during the formation of the coil component 10.

[0020] The winding portion 23a of the coil member 23 is buried inside the composite magnetic body 12, and the wiring portion 23b is disposed outside the composite magnetic body 12. The coil member 23 is, for example, integrally formed with the composite magnetic body 12. The coil member 23 may be formed separately from the composite magnetic body 12, and the composite magnetic body 12 and the coil member 23 may be assembled.

[0021] Here, the internal structure of the composite magnetic body 12 will be described. FIG. 3 is a cross-sectional view showing the internal structure of the composite magnetic body 12. In FIG. 3, a range including two magnetic particles 5 is schematically shown in the internal cross-section of the composite magnetic body 12.

[0022] As shown in FIG. 3, the composite magnetic body 12 includes magnetic powder composed of magnetic particles 5 and a non-magnetic resin member 4 that binds the magnetic particles 5 of the magnetic powder to each other. The composite magnetic body 12 may further contain a coupling agent for improving the dispersibility of the magnetic powder and surface modification of the magnetic powder, and an organometallic soap as a lubricant. Examples of the coupling agent include silane coupling agents, titanium-based coupling agents, titanium alkoxides, and titanium chelates. Examples of the metal soap include zinc stearate, calcium stearate, magnesium stearate, and barium stearate.

[0023] The non-magnetic resin member 4 binds between the magnetic particles 5 of the magnetic powder. The shape of the composite magnetic body 12 is maintained by the non-magnetic resin member 4. The non-magnetic resin member 4 is composed of an insulating resin material. The resin material constituting the non-magnetic resin member 4 is, for example, a thermosetting resin. The resin material constituting the non-magnetic resin member 4 may be a thermoplastic resin. Examples of the thermosetting resin include epoxy resins, phenolic resins, silicone resins, and polyimides. Examples of the thermoplastic resin include acrylic resins, polyethylene, polypropylene, and polystyrene.

[0024] The relative permittivity of the non-magnetic resin member 4 is, for example, 1.5 or more and 10 or less.

[0025] The weight of the non-magnetic resin member 4 is, for example, 1% or more and 10% or less with respect to the weight of the magnetic powder.

[0026] The magnetic powder is a powder containing a large number of magnetic particles 5 and is dispersed in the composite magnetic body 12. The surface of each magnetic particle 5 is covered with the non-magnetic resin member 4. The non-magnetic resin members 4 covering the surfaces of adjacent magnetic particles 5 are bound to each other. That is, the non-magnetic resin member 4 is disposed between the magnetic particles 5, and the magnetic particles 5 are insulated from each other.

[0027] The median diameter D50 of the magnetic particles 5 constituting the magnetic powder is, for example, 5 μm or more and 35 μm or less. To mitigate the electric field concentration between particles, insulation can be ensured by configuring the median diameter D50 of the magnetic powder to be small. Also, by setting the median diameter D50 as described above, a high filling rate and handleability can be ensured. Further, by setting the median diameter D50 of the magnetic powder to 35 μm or less, core loss can be reduced in the high-frequency region, and particularly, eddy current loss can be reduced. Note that the median diameter D50 of the magnetic powder is the particle diameter when counting from the smaller particle sizes with a particle size distribution meter measured by the laser diffraction scattering method, and the cumulative value reaches 50% of the whole.

[0028] The magnetic particles 5 include a metal magnetic particle 1, a non-magnetic resin layer 3 covering the surface of the metal magnetic particle 1, and an inorganic insulating material layer 2 covering the non-magnetic resin layer 3. The magnetic particles 5 are arranged in the order of the metal magnetic particle 1, the non-magnetic resin layer 3, and the inorganic insulating material layer 2 from the center toward the outside, and the outermost surface of the magnetic particles 5 is the inorganic insulating material layer 2.

[0029] The metal magnetic particle 1 is, for example, a metal soft magnetic particle containing iron. Examples of the material of the metal magnetic particle 1 include pure iron, Fe-Si-Al alloys, Fe-Si alloys, Fe-Si-Cr alloys, Fe-Ni alloys, Fe-Co alloys, amorphous alloys, and nanocrystalline alloys.

[0030] The method for producing the metal magnetic particle 1 according to the present embodiment is not particularly limited, and various atomization methods, various chemical methods, or various pulverization methods can be used.

[0031] The non-magnetic resin layer 3 covers, for example, the entire surface of the metal magnetic particle 1 and is in contact with the metal magnetic particle 1. The non-magnetic resin layer 3 is disposed between the metal magnetic particle 1 and the inorganic insulating material layer 2. The thickness of the non-magnetic resin layer 3 is, for example, 1 nm or more and 30 nm or less.

[0032] The non-magnetic resin layer 3 is composed of an insulating resin material. The resin material constituting the non-magnetic resin layer 3 is, for example, a thermosetting resin or a thermoplastic resin. Examples of the thermosetting resin include epoxy resin, phenolic resin, silicone resin, and polyimide. Examples of the thermoplastic resin include acrylic resin, polyethylene, polypropylene, and polystyrene.

[0033] The relative permittivity of the non-magnetic resin layer 3 is, for example, 1.5 or more and 10 or less.

[0034] The inorganic insulating material layer 2 covers, for example, the entire outer surface of the non-magnetic resin layer 3 and is in contact with the non-magnetic resin layer 3. The inorganic insulating material layer 2 is located between the non-magnetic resin layer 3 and the non-magnetic resin member 4. The outer surface of the inorganic insulating material layer 2 is in contact with the non-magnetic resin member 4. The thickness of the inorganic insulating material layer 2 is, for example, 1 nm or more and 30 nm or less.

[0035] The inorganic insulating material layer 2 is composed of an insulating inorganic material. Examples of the resin material constituting the inorganic insulating material layer 2 include metal oxides such as silicon oxide.

[0036] The relative permittivity of the inorganic insulating material layer 2 is, for example, 3 or more and 12 or less.

[0037] Here, the relationship between the thicknesses and relative permittivities of the non-magnetic resin layer 3 and the non-magnetic resin member 4 will be described. Hereinafter, the relative permittivity of the non-magnetic resin layer 3 is denoted as ε3, and the relative permittivity of the non-magnetic resin member 4 is denoted as ε4. Also, as shown in FIG. 3, the thickness of the non-magnetic resin layer 3 is denoted as t3, and the thickness of the thinnest portion of the non-magnetic resin member 4 located between adjacent magnetic particles 5 is denoted as t4. It can also be said that t4 is the shortest distance between adjacent magnetic particles 5. When there are distributions in t3 and t4 within the composite magnetic body 12, t3 and t4 are the average values of the thicknesses at a plurality of locations measured using a cross-sectional photograph of a predetermined area or the like.

[0038] For example, the relationship between the thicknesses of the non-magnetic resin layer 3 and the non-magnetic resin member 4 satisfies t3 ≧ 0.76 × t4.

[0039] Further, for example, the relationship between the thickness and relative permittivity of the non-magnetic resin layer 3 and the non-magnetic resin member 4 satisfies t3 ≧ 0.45 × t4 and ε3 ≧ ε4.

[0040] Further, for example, the relationship between the relative permittivities of the non-magnetic resin layer 3 and the non-magnetic resin member 4 satisfies ε3 ≧ ε4.

[0041] In the composite magnetic body 12, by satisfying any of the above relationships, when a voltage is applied to the composite magnetic body 12, the maximum electric field applied to the composite magnetic body 12 can be reduced. Therefore, the breakdown voltage of the composite magnetic body 12 can be improved. Details of this effect will be described later.

[0042] [1-2. Existence form of magnetic particles in the composite magnetic body] Next, the existence form of the magnetic particles 5 in the composite magnetic body will be described. Since the inorganic insulating material layer 2 of the magnetic particles 5 is made of an inorganic material that is more likely to crack than a resin material, cracks may be formed in the inorganic insulating material layer 2 due to compression or the like during the formation of the composite magnetic body 12. FIGS. 4 to 6 are cross-sectional views showing the cracks formed in the magnetic particles 5 according to the present embodiment.

[0043] As shown in FIG. 4, for example, cracks 2a are formed in the inorganic insulating material layer 2 of the magnetic particles 5. The cracks 2a shown in FIG. 4 are voids and are filled with, for example, air. When the metal magnetic particles 1 come into contact through the cracks 2a when the cracks 2a occur, the breakdown voltage of the composite magnetic body 12 decreases. In the present embodiment, the presence of the non-magnetic resin layer 3 between the metal magnetic particles 1 and the inorganic insulating material layer 2 can prevent the metal magnetic particles 1 from coming into contact with each other even when cracks 2a occur in the inorganic insulating material layer 2, and can improve the breakdown voltage of the composite magnetic body 12. Further, although the electric field tends to concentrate in the cracks 2a that are voids when a voltage is applied to the composite magnetic body 12, the presence of the non-magnetic resin layer 3 between the metal magnetic particles 1 and the inorganic insulating material layer 2 can mitigate the electric field concentration in the cracks 2a.

[0044] Further, in the present embodiment, since the magnetic particles 5 include the nonmagnetic resin layer 3 inside the inorganic insulating material layer 2, as shown in FIG. 5, the crack 2a can be filled with the resin material constituting the nonmagnetic resin layer 3. Thereby, the electric field concentration in the crack 2a can be further alleviated. As shown in FIG. 6, the crack 2a may be filled with the resin material constituting the nonmagnetic resin member 4. Further, the crack 2a may be filled with both the resin material constituting the nonmagnetic resin layer 3 and the resin material constituting the nonmagnetic resin member 4. Further, voids may be provided in a part of the crack 2a filled with the resin material.

[0045] Whether or not the crack 2a is formed, and which state of FIGS. 4 to 6 the formed crack 2a is in, depend on the characteristics of the material constituting the composite magnetic body 12 and the compression molding pressure when forming the composite magnetic body 12, etc. Therefore, the magnetic powder in the composite magnetic body 12 may be composed only of the magnetic particles 5 in which the crack 2a as shown in FIG. 3 is not formed, or may include at least any one of the magnetic particles 5 in which the crack 2a shown in FIGS. 4 to 6 is formed. When the magnetic powder in the composite magnetic body 12 includes at least any one of the magnetic particles 5 in which the crack 2a shown in FIGS. 4 to 6 is formed, in the magnetic powder, the magnetic particles 5 in which the crack 2a shown in FIG. 3 is not formed and one or more of the magnetic particles 5 in which the crack 2a shown in FIGS. 4 to 6 is formed may be mixed. Further, the magnetic powder may be composed only of one or more of the magnetic particles 5 in which the crack 2a shown in FIGS. 4 to 6 is formed. Further, a plurality of cracks 2a may be formed in one magnetic particle 5.

[0046] As described above, the magnetic powder according to the present embodiment is a magnetic powder composed of the magnetic particles 5. The magnetic particles 5 include the metal magnetic particles 1, the nonmagnetic resin layer 3 covering the surface of the metal magnetic particles 1, and the inorganic insulating material layer 2 covering the nonmagnetic resin layer 3. Further, the composite magnetic body 12 according to the present embodiment includes the magnetic powder and the nonmagnetic resin member 4 that binds between the magnetic particles 5 of the magnetic powder.

[0047] With such a configuration, the inorganic insulating material layer 2 and the non-magnetic resin layer 3 can enhance the insulation between the magnetic particles 5. Further, even when a crack 2a is formed in the inorganic insulating material layer 2 due to a molding pressure or the like when forming the composite magnetic body 12, since the inorganic insulating material layer 2 is formed so as to cover the non-magnetic resin layer 3, it is possible to suppress the metal magnetic particles 1 from coming into contact with each other and the insulation between the magnetic particles 5 from deteriorating. Therefore, the withstand voltage of the composite magnetic body 12 can be improved.

[0048] [1-3. Manufacturing Method of Magnetic Powder, Magnetic Material, and Coil Component] Hereinafter, the manufacturing method of the magnetic powder, magnetic material, and coil component according to the present embodiment will be described. FIG. 7 is a flowchart showing the manufacturing process of the coil component 10 according to the present embodiment.

[0049] As shown in FIG. 7, the manufacturing process of the coil component 10 according to the present embodiment includes, for example, a coating process (step S10), a granulated powder manufacturing process (step S20), and a core manufacturing and coil assembly process (step S30). In the coating process, magnetic powder composed of magnetic particles 5 is generated. In the granulated powder manufacturing process, a magnetic material constituting the composite magnetic body 12 is generated. In the core manufacturing process, a composite magnetic body 12 obtained by molding a magnetic material and a coil member 23 are formed, and the coil component 10 is completed by assembling the composite magnetic body 12 and the coil member 23. Hereinafter, the case where a thermosetting resin is used as the material of the non-magnetic resin member 4 will be described.

[0050] FIG. 8 is a flowchart showing the film-forming process according to the present embodiment. As shown in FIG. 8, in the film-forming process, first, a non-magnetic resin layer 3 is formed on the surface of the metal magnetic particles 1 (step S11). Specifically, for example, a resin solution film is formed on the surface of the metal magnetic particles 1 by mixing a metal powder composed of the metal magnetic particles 1, a resin material serving as a raw material of the non-magnetic resin layer 3, and an organic solvent. Then, the organic solvent is removed by heat treatment, thereby forming the non-magnetic resin layer 3 that coats the surface of the metal magnetic particles 1. The higher the mixing ratio of the resin material to the metal powder, the larger the thickness t3 of the non-magnetic resin layer 3 can be. The thickness t3 can be adjusted by adjusting the mixing ratio of the metal powder and the resin material. Further, the thickness t3 of the non-magnetic resin layer 3 may be increased by repeating the above operation of forming the non-magnetic resin layer 3. Also, the relative permittivity ε3 of the non-magnetic resin layer 3 can be adjusted according to the type of the resin material serving as a raw material of the non-magnetic resin layer 3.

[0051] After forming the non-magnetic resin layer 3 on the surface of the metal magnetic particles 1, an inorganic insulating material layer 2 that coats the non-magnetic resin layer 3 is formed (step S12). Specifically, for example, a powder composed of the metal magnetic particles 1 on which the non-magnetic resin layer 3 generated in step S12 is formed, a metal alkoxide such as tetraethoxysilane (TEOS), and water are reacted in an organic solvent in which the non-magnetic resin layer 3 is insoluble in the presence of a base catalyst such as aqueous ammonia. As a result, the hydrolyzed TEOS polymerizes, and a silicon oxide film is formed as the inorganic insulating material layer 2 on the non-magnetic resin layer 3. In the above reaction, an acid catalyst such as hydrochloric acid or acetic acid may be used instead of the base catalyst. Also, the inorganic insulating material layer 2 may be formed using a thin film deposition process or the like.

[0052] Through the above steps, a magnetic powder composed of the magnetic particles 5 is obtained.

[0053] FIG. 9 is a flowchart showing the granulated powder manufacturing process according to the present embodiment. As shown in FIG. 9, in the granulated powder manufacturing process, first, the magnetic powder generated in the coating process, the resin material that is the raw material of the non-magnetic resin member 4, and an organic solvent are kneaded and dispersed (step S21). Thereby, a mixture containing the organic solvent, the magnetic powder, and the resin material is generated. Further, in step S21, other materials such as an organic metal soap and a coupling agent may be further added and kneaded and dispersed as necessary. As the organic solvent, for example, toluene, xylene, ethanol, methyl ethyl ketone, etc. are used.

[0054] The kneading and dispersion are performed by putting materials such as the weighed magnetic powder, resin material, and organic solvent into a container and mixing and dispersing them with a rotary ball mill. The higher the mixing ratio of the resin material to the magnetic powder, the larger the above-mentioned thickness t4 can be made, and the thickness t4 can be adjusted by adjusting the mixing ratio of the magnetic powder and the resin material. Further, the relative permittivity ε4 of the non-magnetic resin member 4 can be adjusted according to the type of the resin material that is the raw material of the non-magnetic resin member 4.

[0055] The above kneading and dispersion are performed, for example, at room temperature. The kneading and dispersion are not limited to the kneading and dispersion using a rotary ball mill, and other kneading and dispersion methods may be used.

[0056] After kneading and dispersing the magnetic powder, resin material, and organic solvent, granulation and drying are performed (step S22). Specifically, the mixture generated in step S21 is heat-treated at a predetermined temperature. By this heat treatment, the organic solvent is removed from the mixture, and granulated powder composed of the magnetic powder and the resin material is obtained.

[0057] The predetermined temperature is set to a temperature at which the organic solvent can be removed, for example, according to the boiling point of the organic solvent. Further, when the resin material constituting the non-magnetic resin layer 3 is a thermosetting resin, the predetermined temperature is set to be, for example, less than the curing temperature of the thermosetting resin. That is, the subsequent steps are performed while the resin material constituting the non-magnetic resin layer 3 is in an uncured state. The predetermined temperature is, for example, 65°C or higher and 150°C or lower. Note that the thermosetting resin constituting the non-magnetic resin layer 3 may be cured in step S22.

[0058] Next, the granulated powder granulated in step S22 is further pulverized to form a powder, and the powdered granulated powder is classified by a predetermined particle size (step S23). Thereby, a magnetic material made of the granulated powder is obtained.

[0059] FIG. 10 is a flowchart showing the core manufacturing and coil assembling steps according to the present embodiment. As shown in FIG. 10, first, a coil member 23 is formed (step S31). The coil member 23 is formed by winding a conductor made of a metal such as copper a predetermined number of times to form a winding portion 23a. Note that instead of step S31, a previously formed coil member 23 may be prepared.

[0060] Next, the composite magnetic body 12 is molded (step S32). As the material of the composite magnetic body 12, the magnetic material manufactured in the granulated powder manufacturing step is used. First, the magnetic material classified in the granulated powder manufacturing step is put into a molding die. At this time, for example, the coil member 23 and the magnetic material are put into the molding die so that the portion other than the end of the winding portion 23a of the conductor of the coil member 23 is covered with the magnetic material.

[0061] Subsequently, for example, uniaxial molding is performed at a molding pressure of 0.1 ton / cm 2 or more and 15 ton / cm 2 or less to produce a molded body. The molding pressure is 4.5 ton / cm 2 or more and 15 ton / cm 2The following may be applicable. The higher the molding pressure, the smaller the above-mentioned thickness t4 can be, and the thickness t4 can be adjusted by the molding pressure. Further, the above-mentioned thickness t4 can also be adjusted by the addition amount of the resin material that is the raw material of the non-magnetic resin member 4.

[0062] The shape of the molded body is, for example, the shape of the composite magnetic body 12 shown in FIGS. 1 and 2. Note that the shape of the molded body is not limited to this, and other shapes may be used. Further, a molded body made of a magnetic material that becomes the shape of the composite magnetic body 12 by assembling without putting the coil member 23 into the molding die may be formed, and the molded body and the coil member 23 may be assembled.

[0063] Furthermore, the molded body is thermally cured (step S33). The thermal curing of the molded body is performed, for example, in a range of a temperature of 100°C or higher and 300°C or lower at a predetermined oxygen partial pressure. Thereby, for example, the thermosetting resin constituting the non-magnetic resin layer 3 and the non-magnetic resin member 4 is cured. For the thermal curing of the molded body, for example, an atmosphere-controlled electric furnace is used. Note that other methods may be used for the thermal curing of the molded body.

[0064] Furthermore, after the thermal curing of the molded body, a wiring portion 23b disposed outside the composite magnetic body 12 may be connected to the end portion of the winding portion 23a of the coil member 23.

[0065] Through the above steps, the coil component 10 including the composite magnetic body 12 and the coil member 23 is completed.

[0066] [2. Electric field analysis of composite magnetic body] Next, the electric field analysis results of the composite magnetic body including the magnetic powder composed of the magnetic particles 5 according to the embodiment will be described.

[0067] In the electric field analysis, an analysis model of a composite magnetic material including magnetic powder composed of the magnetic particles 5 according to the embodiment and an analysis model of a composite magnetic material including magnetic powder composed of the magnetic particles 5X according to the comparative example were used. Also, electric field analysis was performed under various conditions in which the relationship between the thickness t3 of the non-magnetic resin layer 3 and the thickness t4 of the non-magnetic resin member 4, and the relationship between the relative permittivity ε3 of the non-magnetic resin layer 3 and the relative permittivity ε4 of the non-magnetic resin member 4 were changed. Further, based on the electric field analysis, the relationship between the thickness t3 of the non-magnetic resin layer 3 and the thickness t4 of the non-magnetic resin member 4, and the relationship between the relative permittivity ε3 of the non-magnetic resin layer 3 and the relative permittivity ε4 of the non-magnetic resin member 4 that can effectively improve the withstand voltage of the composite magnetic material were determined.

[0068] [2-1. Analysis Model] First, the analysis model used in the electric field analysis will be described. FIG. 11 is a diagram showing an analysis model including the magnetic particles 5X according to the comparative example. FIG. 12 is a diagram showing another analysis model including the magnetic particles 5X according to the comparative example. FIG. 13 is a diagram showing an analysis model including the magnetic particles 5 according to the embodiment. FIG. 14 is a diagram showing another analysis model including the magnetic particles 5 according to the embodiment. FIG. 15 is a diagram showing still another analysis model including the magnetic particles 5 according to the embodiment.

[0069] As shown in FIGS. 11 to 15, in the electric field analysis, five types of two-dimensional analysis models, namely model A1, model A2, model B1, model B2, and model B3, were used. In each analysis model, two magnetic particles 5 or 5X are arranged between two electrodes 8 along the direction in which the electrodes 8 are arranged. Also, in each analysis model, the magnetic particles 5 or 5X are covered with the non-magnetic resin member 4. Further, in each analysis model, the non-magnetic resin member 4 is disposed between the electrode 8 and the magnetic particles 5 or 5X, and between the two magnetic particles 5 or 5X. The magnetic particles 5X according to the comparative example are magnetic particles not provided with the non-magnetic resin layer 3, and are composed of the metal magnetic particles 1 and the inorganic insulating material layer 2 that directly covers the surface of the metal magnetic particles 1.

[0070] As shown in Fig. 11, Model A1 is a model including magnetic particles 5X according to the comparative example. In Model A1, no crack 2a is formed in the inorganic insulating material layer 2 of the magnetic particles 5X.

[0071] As shown in Fig. 12, Model A2 is a model including magnetic particles 5X according to the comparative example. In Model A2, a crack 2a with a void inside is formed in the inorganic insulating material layer 2 of the magnetic particles 5X.

[0072] As shown in Fig. 13, Model B1 is a model including magnetic particles 5 according to the embodiment. In Model B1, no crack 2a is formed in the inorganic insulating material layer 2 of the magnetic particles 5.

[0073] As shown in Fig. 14, Model B2 is a model including magnetic particles 5 according to the embodiment. In Model B2, a crack 2a with a void inside is formed in the inorganic insulating material layer 2 of the magnetic particles 5.

[0074] As shown in Fig. 15, Model B3 is a model including magnetic particles 5 according to the embodiment. In Model B3, a crack 2a filled with the resin material of the non-magnetic resin layer 3 is formed in the inorganic insulating material layer 2 of the magnetic particles 5.

[0075] [2-2. Electric Field Analysis Method] In the electric field analysis, values other than the thickness t3 and relative permittivity ε3 of the non-magnetic resin layer 3 were fixed, and the values of the thickness t3 and relative permittivity ε3 of the non-magnetic resin layer 3 were changed to compare the electric field distributions in each analysis model. The fixed values are as shown in Table 1. Note that the analysis was performed assuming that the metal magnetic particles 1 and the electrodes 8 are perfect conductors.

[0076]

Table 1

[0077] The electric field analysis was performed using Femtet (registered trademark) manufactured by Murata Software Co., Ltd. The voltage was set so that the electric field applied between the two electrodes 8 would be 20 V / mm, and the simulation results of the electric field distribution of each analysis model were output.

[0078] Figures 16 and 17 are diagrams showing an example of the electric field analysis results. Figures 16 and 17 show the electric field analysis results in the vicinity between two magnetic particles 5 or 5X under the condition E2 (t3 = t4, ε3 = ε4) described later. In Figures 16 and 17, the lighter the color, the larger the electric field.

[0079] As shown in Figure 16, when comparing Model A1 and Model B1, the overall electric field of Model B1 with the non-magnetic resin layer 3 is smaller. That is, the maximum electric field of Model B1 is smaller than the maximum electric field of Model A1. Also, as shown in Figure 17, in Model A2 where a crack 2a is formed in the inorganic insulating material layer 2, the electric field in the inorganic insulating material layer 2 is equivalent to that of Model A1 shown in Figure 16, but the electric field in the void part inside the crack 2a is larger than other parts. Similar to Model A2, in Model B2 with the non-magnetic resin layer 3, the electric field in the void part inside the crack 2a is also larger than other parts, but the electric field in the void part inside the crack 2a is smaller than that of Model A2. Also, in Model B3 where the resin material of the non-magnetic resin layer 3 fills the crack 2a, the electric field inside the crack 2a is even lower than that of Model B2. Thus, the maximum electric fields in each analysis model shown in Figure 17 are in the order of Model A2, Model B2, and Model B3, becoming smaller. Since the occurrence of dielectric breakdown becomes less likely as the maximum electric field becomes smaller, the withstand voltage of the composite magnetic body is improved.

[0080] In the following description of the electric field analysis results, in order to quantify the electric field distributions as shown in FIGS. 16 and 17, in the analysis results of each analysis model, the maximum electric field ratio of the analysis models (models B1, B2, B3) including the magnetic particles 5 according to the embodiments with respect to the analysis models (models A1, A2) including the magnetic particles 5X according to the comparative example was calculated. Therefore, if the maximum electric field ratio is less than 1, it can be said that the maximum electric field of the analysis model according to the embodiment is smaller than that of the analysis model according to the comparative example, and the breakdown voltage of the composite magnetic material can be improved.

[0081] Specifically, as the two analysis models for calculating the maximum electric field ratio, four combinations of (1) model A1 and model B1 (B1 / A1), (2) model A2 and model B1 (B1 / A2), (3) model A2 and model B2 (B2 / A2), and (4) model A2 and model B3 (B3 / A2) were selected. In the combination of (1), the magnetic particles 5X without the crack 2a formed therein and the magnetic particles 5 are compared respectively. From (2) to (4), the magnetic particles 5X with the crack 2a formed therein are compared with the magnetic particles 5 without the crack 2a formed therein, the magnetic particles 5 with the crack 2a formed in the void, and the magnetic particles 5 in which the resin material of the non-magnetic resin layer 3 is filled in the formed crack 2a, respectively.

[0082] In addition, the calculation of the maximum electric field ratio was performed at three comparison locations: the non-magnetic resin member 4, the inorganic insulating material layer 2, and all the components. For example, when the comparison location is the non-magnetic resin member 4 or the inorganic insulating material layer 2, the maximum electric field ratio was calculated based on the maximum electric field only in the non-magnetic resin member 4 or the inorganic insulating material layer 2. When the comparison location is all the components, the maximum electric field ratio was calculated based on the maximum electric field over the entire analysis model.

[0083] In addition, as an evaluation of whether the breakdown voltage of the composite magnetic material using the magnetic particles 5 according to the embodiment can be improved, the following criteria were used. ◎: The maximum electric field ratio is less than 1 at all comparison locations of the non-magnetic resin member 4, the inorganic insulating material layer 2, and all the components 〇: The maximum electric field ratio is less than 1 in the comparison of all the components ×: In the comparison of all components, the maximum electric field ratio is 1 or more

[0084] [2-3. Electric field analysis results] First, Table 2 shows the results of electric field analysis with the thickness t3 and relative permittivity ε3 of the non-magnetic resin layer 3 changed from condition C1 to condition F3.

[0085] [Table 2]

[0086] As shown in Table 2, when t3 is 7.6 nm or more in the thickness item, that is, when t3 ≥ 0.76 × t4, the withstand voltage evaluation is "◎", indicating that the withstand voltage of the composite magnetic body using the magnetic particles 5 according to the embodiment is improved.

[0087] Next, Table 3 shows the results of electric field analysis with the thickness t3 and relative permittivity ε3 of the non-magnetic resin layer 3 changed from condition E1 to condition H3. Note that in Table 3, the results from condition E1 to condition F3 are the same as those shown in Table 2.

[0088] [Table 3]

[0089] As shown in Table 3, in the relative permittivity item, when ε3 is 4 or more, that is, when ε3 ≥ ε4, the withstand voltage evaluation is "○" or "◎", indicating that the withstand voltage of the composite magnetic body using the magnetic particles 5 according to the embodiment is improved. Furthermore, when ε3 ≥ ε4 and t3 is 4.5 nm or more, that is, when t3 ≥ 0.45 × t4, the withstand voltage evaluation is "◎", indicating that the withstand voltage of the composite magnetic body using the magnetic particles 5 according to the embodiment is further improved.

[0090] From the above results, it was found that the breakdown voltage of the composite magnetic material can be improved by satisfying any one of (i) t3 ≥ 0.76 × t4, (ii) t3 ≥ 0.45 × t4, and ε3 ≥ ε4, and (iii) ε3 ≥ ε4. In particular, it was found that the breakdown voltage of the composite magnetic material can be further improved by satisfying any one of (i) t3 ≥ 0.76 × t4 and (ii) t3 ≥ 0.45 × t4, and ε3 ≥ ε4.

[0091] Note that the above analysis results are just an example and do not limit the scope of the present disclosure. For example, even in an analysis model where the maximum electric field ratio is 1 or more in the electric field analysis result, actually, due to the presence of the non-magnetic resin layer 3, the contact between the metal magnetic particles 1 is suppressed, and by using the magnetic particles 5, the breakdown voltage of the composite magnetic material can be improved compared to the case where the magnetic particles 5X according to the comparative example are used.

[0092] (Other embodiments, etc.) As described above, the magnetic powder and composite magnetic material according to the embodiments of the present disclosure have been described, but the present disclosure is not limited to this embodiment.

[0093] For example, the electrical components using the above-described composite magnetic material are also included in the present disclosure. Examples of the electrical components include inductance components such as reactors, inductors, and transformers for high frequencies. Also, a power supply device provided with the above-described electrical components is included in the present disclosure.

[0094] Further, the present disclosure is not limited to the above embodiment. As long as it does not deviate from the gist of the present disclosure, various modifications conceived by those skilled in the art applied to this embodiment or forms constructed by combining components in different embodiments may also be included within the scope of one or more aspects.

Explanation of reference numerals

[0095] 1 Metal magnetic particles 2 Inorganic insulating material layer 2a Crack 3 Non-magnetic resin layer 4 Non-magnetic resin member 5 Magnetic particles 8 Electrode 10 Coil component 12 Composite magnetic material 12a Core part 23 Coil member 23a Winding part 23b Wiring part

Claims

1. a magnetic powder composed of magnetic particles; and a non-magnetic resin member that binds between the magnetic particles of the magnetic powder, wherein the magnetic particles are metal magnetic particles, are provided with a non-magnetic resin layer covering the surface of the metal magnetic particles, and are provided with an inorganic insulating material layer covering the non-magnetic resin layer, when the thickness of the non-magnetic resin layer is t3 and the thickness of the thinnest part of the non-magnetic resin member located between adjacent magnetic particles among the magnetic powder is t4, t3 ≥ 0.76 × t4 is satisfied, a composite magnetic material.

2. A magnetic powder composed of magnetic particles; and a non-magnetic resin member that binds between the magnetic particles of the magnetic powder, wherein the magnetic particles are metal magnetic particles, are provided with a non-magnetic resin layer covering the surface of the metal magnetic particles, and are provided with an inorganic insulating material layer covering the non-magnetic resin layer, when the thickness of the non-magnetic resin layer is t3, the thickness of the thinnest part of the non-magnetic resin member located between two adjacent magnetic particles among the magnetic powder is t4, the relative permittivity of the non-magnetic resin layer is ε3, and the relative permittivity of the non-magnetic resin member is ε4, t3 ≥ 0.45 × t4 and ε3 ≥ ε4 is satisfied, a composite magnetic material.

3. cracks are formed in the inorganic insulating material layer, and at least a part of the cracks is filled with a resin material constituting the non-magnetic resin layer, the composite magnetic material according to claim 1 or 2.

Images