Magnetic material, method for manufacturing magnetic material, and inductor

Abstract

It achieves high mechanical strength after compression molding. [Solution] The magnetic material comprises a magnetic powder containing first magnetic particles and second magnetic particles having a smaller particle diameter than the first magnetic particles, and a resin, wherein a binder layer containing a silane coupling agent is formed on at least a portion of the outer surface of the first magnetic particles.

Description

Technical Field

[0001] The present invention relates to a magnetic material, a method for manufacturing a magnetic material, and an inductor.

Background Art

[0002] An inductor (coil component) using a metallic magnetic material is widely used in various electric devices such as smartphones, for example, as a chip inductor capable of surface mounting. As a metallic magnetic material used for such an inductor, it is known to use a magnetic material in which a resin is added to soft magnetic powder composed of particles of a soft magnetic metal and compression-molded to use a compacted magnetic core or a green body (hereinafter referred to as a green body).

[0003] Patent Document 1 discloses that, for a magnetic material, by including a silane coupling agent, the mechanical strength of a cured product (molded product) of the magnetic material can be improved.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in a green body formed by compression molding a magnetic material, if high pressure is generated inside the green body due to, for example, the moisture absorbed evaporating suddenly during reflow, sufficient mechanical strength cannot be maintained and cracks may occur inside the green body. When such cracks occur inside the green body of the inductor, it will cause a decrease in inductance.

[0006] An object of the present invention is to provide a magnetic material capable of achieving high mechanical strength after compression molding.

Means for Solving the Problems

[0007] A magnetic material according to one aspect of the present disclosure comprises a magnetic powder containing first magnetic particles and second magnetic particles having a smaller particle size than the first magnetic particles, and a resin, wherein a binder layer containing a silane coupling agent is formed on at least a portion of the outer surface of the first magnetic particles. [Effects of the Invention]

[0008] According to the magnetic material of the present invention, high mechanical strength can be achieved after compression molding. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram showing the state of the magnetic material according to the embodiment. [Figure 2] This is an explanatory diagram illustrating an example of the composition of the first soft magnetic particle. [Figure 3] This is an explanatory diagram illustrating an example of the composition of the second soft magnetic particle. [Figure 4] This is an explanatory diagram illustrating the outline of the manufacturing process for the magnetic material according to the embodiment. [Figure 5] This is a magnified image of a portion of the destroyed fragments. [Figure 6] This is a schematic perspective view showing the configuration of an inductor. [Figure 7] This is a schematic perspective view showing the configuration of an inductor. [Figure 8] This is a perspective view showing the internal structure of an inductor. [Figure 9] This is a cross-sectional view showing a cross-section perpendicular to the length direction of the wire used in the coil. [Figure 10] This is an explanatory diagram illustrating the general manufacturing process of inductors. [Figure 11] This is an explanatory diagram illustrating one method of forming a basic body. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings. Note that some drawings may be schematic. Also, dimensions and proportions in schematic drawings may differ from actual values.

[0011] [Magnetic material] Figure 1 is a schematic diagram showing the state of the magnetic material according to the embodiment. As shown in Figure 1, the magnetic material 1 used for forming the inductor body and the like includes magnetic powder 2 and resin 7.

[0012] The magnetic powder 2 is composed of particles of a soft magnetic metal. The magnetic powder 2 includes, for example, first soft magnetic particles 3 and second soft magnetic particles 5 having a smaller average particle size than the first soft magnetic particles 3. In this specification, "average particle size" means the median diameter based on volume.

[0013] The average particle sizes of the first soft magnetic particles 3 and the second soft magnetic particles 5 can be measured separately using a particle size analyzer before mixing them together. Alternatively, when measuring the particle size in the form of a molded body obtained by compression molding of the magnetic material 1, the particle size can be measured by analyzing the cross-sections of the first soft magnetic particles 3 and the second soft magnetic particles 5 from electron microscope images of the cross-section of the body obtained by polishing the body. For example, the equivalent circular diameter of the particle cross-sections of the first soft magnetic particles 3 and the second soft magnetic particles 5 can be determined from the electron microscope images. Then, assuming that the first soft magnetic particles 3 and the second soft magnetic particles 5 are spheres having the above-mentioned equivalent circular diameter, the volume of each sphere can be determined, and the average particle size can be calculated from the median of the volume distribution.

[0014] The average particle diameter of the first soft magnetic particles 3 is 20 μm or more and 28 μm or less, preferably 21.4 μm or more and 27.4 μm or less. The average particle diameter of the second soft magnetic particles 5 is 1 μm or more and 6 μm or less, preferably 1.5 μm or more and 1.8 μm or less. By thus constituting the magnetic powder 2 with the first soft magnetic particles 3 and the second soft magnetic particles 5 having different average particle diameters, the saturation magnetic flux density as a base body can be increased by the first soft magnetic particles 3 having a large average particle diameter to improve the DC superposition characteristics, and the second soft magnetic particles 5 having a small average particle diameter can enter the gaps between the first soft magnetic particles 3 to increase the filling rate of the magnetic powder 2 in the base body and improve the relative permeability.

[0015] Also, the amount of the second soft magnetic particles 5 contained in the magnetic powder 2 is 15% by weight or more and 30% by weight or less, preferably 20% by weight or more and 30% by weight or less, based on the total weight of the magnetic powder 2. When the content of the second soft magnetic particles 5 in the magnetic powder 2 is within the above range, the filling rate of the magnetic powder 2 in the base body which is a molded body of the magnetic material 1 can be made higher.

[0016] The composition of the soft magnetic metal constituting the second soft magnetic particles 5 may be the same as the composition of the soft magnetic metal constituting the first soft magnetic particles 3, but preferably has different compositions from each other and has substantially the same hardness as each other. The hardness of the first soft magnetic particles 3 and the second soft magnetic particles 5 can be measured using the nanoindentation method. For example, the hardness of the first soft magnetic particles 3 is 600 HV (kgf / mm2) or more and 1200 HV or less, desirably 800 HV or more and 1000 HV or less. Also, the hardness of the second soft magnetic particles 5 is 900 HV (kgf / mm2) or more and 1400 HV or less, desirably 900 HV or more and 1100 HV or less.

[0017] Also, the ratio of the hardness of the second soft magnetic particles 5 to the hardness of the first soft magnetic particles 3 is desirably 0.7 or more and 1.2 or less. Thereby, when the magnetic material 1 containing these soft magnetic particles is compression-molded to form a base body, it is possible to prevent the soft magnetic particles with the lower hardness of the first soft magnetic particles 3 or the second soft magnetic particles 5 from being deformed, and to prevent the insulation resistance as the base body from decreasing.

[0018] [First soft magnetic particles] FIG. 2 is an explanatory diagram for explaining a configuration example of the first soft magnetic particles 3. As shown in FIG. 2, the first soft magnetic particles 3 have a particle core 3A made of a soft magnetic metal and an insulating film 3C formed on the surface of the particle core 3A. Further, a binding layer 3D is formed at least partially on the surface of the insulating film 3C in the first soft magnetic particles 3, that is, on the outer peripheral surface of the first soft magnetic particles 3.

[0019] The particle core 3A has an oxide film 3B formed by oxidizing the soft magnetic metal constituting the particle core 3A on the surface of the particle core 3A.

[0020] More specifically, the particle core 3A is an amorphous or crystalline metal magnetic material of an Fe—Si—Cr alloy or an Fe—Si alloy. The above Fe—Si—Cr alloy or Fe—Si alloy, for example, contains 87% by weight or more of Fe and 3% by weight or more of Si, and may contain B (boron).

[0021] The particle core 3A of the first soft magnetic particles 3 is not limited to the above Fe—Si—Cr alloy or Fe—Si alloy, and may be formed using an iron-based metal magnetic material. Such an iron-based metal magnetic material can be, for example, an amorphous or crystalline alloy of Fe—Si—Cr—Al or Fe—Si—Al.

[0022] Further, when a Cr-free alloy is used as the particle core 3A of the first soft magnetic particles 3, the weight ratio of Fe in the particle core 3A can be increased. Therefore, the saturation magnetic flux density of the element body produced using this particle core 3A can be further increased, and better DC superposition characteristics can be obtained as an inductor.

[0023] The oxide film 3B can be formed during the manufacturing process of the particle nucleus 3A by oxidizing the soft magnetic metal on the surface of the particle nucleus 3A. For example, the oxide film 3B can be formed during the manufacturing process of the particle nucleus 3A by exposing the particle nucleus 3A to a water or oxygen atmosphere, and / or by providing an active oxidation step such as exposing the particle nucleus 3A to a high-temperature oxygen atmosphere.

[0024] As the oxidation of the soft magnetic metal progresses on the surface of the particle nucleus 3A, the thickness of the oxide film 3B increases, and the surface roughness also increases, leading to increased adhesion strength between the insulating film 3C formed on the surface and the oxide film 3B. On the other hand, as the oxidation of the soft magnetic metal progresses and the thickness of the oxide film 3B increases, the amount of soft magnetic metal contained in the particle nucleus 3A decreases, and the effective filling ratio of the substrate when the substrate is formed using the particle nucleus 3A decreases. From the viewpoint of ensuring the adhesion strength of the insulating film 3C and suppressing the effective reduction of soft magnetic metal within a certain range, it is desirable that the oxygen content of the particle nucleus 3A be between 900 ppm and 2800 ppm.

[0025] The insulating film 3C formed on the oxide film 3B is, for example, an inorganic glass film formed by a mechanochemical method. The inorganic glass film is, for example, a low-melting-point glass such as zinc phosphate, calcium phosphate, or manganese phosphate. Alternatively, the insulating film 3C may be composed of an organic polymer film, an organic-inorganic hybrid film, or an inorganic insulating film. These insulating films 3C can be formed by mechanochemical methods or sol-gel reactions of metal alkoxides, depending on their material.

[0026] The thickness of the insulating film 3C is between 10 nm and 50 nm. By making the thickness of the insulating film 3C 10 nm or more, the resistivity of the first soft magnetic particles 3 can be increased. Furthermore, by making the thickness of the insulating film 3C 50 nm or less, the proportion of metal in the first soft magnetic particles 3 can be increased, and good magnetic properties can be obtained in the substrate using this.

[0027] The first soft magnetic particle 3 with the above configuration can ensure the adhesion strength of the insulating film 3C formed on the oxide film 3B of the particle nucleus 3A, thereby stably achieving high dielectric strength in the base material while maintaining a high relative permeability of the base material.

[0028] The mechanism by which cracks occur in a compressed magnetic material substrate due to pressure generated when absorbed moisture rapidly evaporates during reflow soldering is not bound by any specific theory, but is presumed to be as follows: Inside the substrate, absorbed moisture rapidly evaporates during reflow soldering, generating high pressure. This pressure causes cracks to form at the interface between the first soft magnetic particle 3 and the resin 7 (the outer surface of the first soft magnetic particle 3). Due to these cracks, the inductance (L value) of the inductor using the substrate decreases.

[0029] Therefore, the inventors have found that instead of simply including the silane coupling agent in the magnetic material 1, forming a binding layer 3D containing the silane coupling agent on at least a portion of the outer surface of the first soft magnetic particles 3 can strengthen the bond between the resin 7 and the outer surface of the first soft magnetic particles 3. As a result, in a compressed body of the magnetic material 1, the bond between the resin 7 and the outer surface of the first soft magnetic particles 3 can be strengthened even at high temperatures after moisture absorption (for example, during reflow), thereby suppressing the occurrence of cracks and the like. In this way, the magnetic material 1 can achieve high mechanical strength after compression molding.

[0030] The bonding layer 3D is formed on the surface of the insulating film 3C on the first soft magnetic particle 3, i.e., on at least a portion of the outer surface of the first soft magnetic particle 3, by spraying a silane coupling agent onto the first soft magnetic particle 3 on which the insulating film 3C has been formed. In the following description, the first soft magnetic particle 4 will be referred to as the first soft magnetic particle 4 to distinguish it from the first soft magnetic particle 3 after the bonding layer 3D has been formed.

[0031] With respect to the silane coupling agent contained in the binding layer 3D of the first soft magnetic particles 3, it is preferable that the mass ratio of the silane coupling agent to the first soft magnetic particles 3, with the mass of the first soft magnetic particles 3 being 100, is 0.02 or more and 0.06 or less. Specifically, in the examples described later, the strength of the sample formed by compression of the magnetic material 1 was maximized when the above mass ratio was 0.04, and a decrease in strength was observed when the ratio was between 0.02 and 0.04, and between 0.04 and 0.02.

[0032] [Second soft magnetic particles] Figure 3 is an explanatory diagram illustrating an example of the configuration of the second soft magnetic particle 5. As shown in Figure 3, the second soft magnetic particle 5 is composed of a particle nucleus 5A made of a soft magnetic metal and an insulating film 5B formed on the surface of the particle nucleus 5A.

[0033] The soft magnetic metal constituting the particle nucleus 5A is, for example, crystalline or amorphous iron (Fe). Specifically, the granular body of the second soft magnetic particle 5 is, for example, carbonyl iron powder with an onion skin structure, and the Fe content is 95% by weight or more and 99.8% by weight or less, or 97% by weight or more and 99.8% by weight or less. This carbonyl iron powder may contain carbon C, oxygen O, nitrogen N, and sulfur S as impurities. Furthermore, the carbonyl iron powder that forms the particle nucleus 5A may have an Fe oxide film on its surface.

[0034] The soft magnetic metal constituting the particle nucleus 5A of the second soft magnetic particle 5 can be an iron-based metallic magnetic material containing other metals in addition to Fe, similar to the first soft magnetic particle 81 described above.

[0035] The insulating film 5B of the second soft magnetic particle 5 may be composed of, for example, a sol-gel reaction product with silica as a component, and may contain hydrocarbon groups having a linear portion with 8 or more carbon atoms. Specifically, the hydrocarbon group having a linear portion with 8 or more carbon atoms is, for example, an alkyl group which is a chain-like saturated hydrocarbon group. The hydrocarbon group having a linear portion with 8 or more carbon atoms may be one or more hydrocarbon groups selected from the group consisting of octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl groups. Furthermore, the alkyl group may be a primary alkyl group, a secondary alkyl group, or a tertiary alkyl group.

[0036] The hydrocarbon group having a long chain can be formed, for example, as a product of a sol-gel reaction using a mixture of tetraethoxysilane (TEOS) and a silane coupling agent having the hydrocarbon group.

[0037] In this case, by adding a hydrocarbon group having a linear portion with 8 or more carbon atoms to the insulating film 5B of the second soft magnetic particle 5, the packing rate of these magnetic powders 2 in the base body can be improved when the magnetic material 1 containing the first soft magnetic particle 3 and the second soft magnetic particle 5 is compression molded to form the base body.

[0038] The mechanism by which the packing efficiency of the magnetic powder 2 is improved is not bound by any particular theory, but is presumed to be as follows. As mentioned above, the base material is formed by compression molding a magnetic material 1 containing first soft magnetic particles 3, second soft magnetic particles 5, and resin 7. In this case, if one of the soft magnetic particles, for example the second soft magnetic particles 5, has a hydrocarbon group with a linear portion having 8 or more carbon atoms on its surface, the hydrogen bonding and / or dipole interaction between the second soft magnetic particles 5 and the polar groups (epoxy groups and / or hydroxyl groups, etc.) of the resin 7 can be reduced, thereby improving the fluidity (slipperiness) of the second soft magnetic particles 5 during compression molding.

[0039] As a result, the highly slippery second soft magnetic particles 5 can enter the gaps between the first soft magnetic particles 3. This mechanism is thought to improve the packing density of soft magnetic particles in the substrate compared to cases where the soft magnetic particles do not have long-chain hydrocarbon groups. By improving the packing density of soft magnetic particles, the density of soft magnetic powder in the substrate can be increased, and as a result, the relative permeability of the substrate can be increased.

[0040] [resin] Resin 7 may be any epoxy resin. The epoxy resin in this invention is not particularly limited, and various known epoxy resins can be used, but those having rigid structures such as multiple aromatic rings are preferred from the viewpoint of mechanical strength. For example, bisphenol A novolac type epoxy resin, bisphenol F novolac type epoxy resin, triazine skeleton-containing epoxy resin, fluorene skeleton-containing epoxy resin, triphenylmethane type epoxy resin, biphenyl type epoxy resin, xylylene type epoxy resin, phenol aralkyl type epoxy resin, biphenyl aralkyl type epoxy resin, naphthalene type epoxy resin, anthracene type epoxy resin, and dicyclopentadiene type epoxy resin are preferred from this viewpoint. These may be used individually or in combination of two or more types. Furthermore, the epoxy resin curing agent is not particularly limited as long as it cures the epoxy resin, but from the viewpoint of workability, one that is solid at room temperature is preferred. Examples include phenol novolac resins, cresol novolac resins, bisphenol A type novolac resins, triazine skeleton-containing phenolic resins, triphenylmethane type phenolic resins, phenol aralkyl resins, biphenyl aralkyl resins, dicyclopentadiene type phenol novolac resins, and imidazoles. These epoxy resin curing agents may be used individually or in combination of two or more types.

[0041] The weight percentage (wt%) of resin 7 relative to the total weight of magnetic material 1 is preferably 2.7 wt% to 4.0 wt%. Specifically, in the examples described later, it was found that the magnetic permeability (μ) of the sample formed by compression of magnetic material 1 was maximized when the above weight percentage was 3.5 wt%. Furthermore, a decrease in the magnetic permeability (μ) of the sample was observed when the above weight percentage was between 2.7 wt% and 3.5 wt% and between 3.5 wt% and 4.0 wt%. In addition, it was found that no sample could be formed when the above weight percentage was 2 wt% or 4 wt%.

[0042] [Method for manufacturing magnetic materials] Figure 4 is an explanatory diagram illustrating the outline of the manufacturing process of the magnetic material 1 according to the embodiment. As shown in Figure 4, the manufacturing process of the magnetic material 1 includes a preparation step (S1), a pretreatment step (S2), and a mixing step (S3).

[0043] First, in the preparation step (S1), the first soft magnetic particles 4, the second soft magnetic particles 5, the silane coupling agent 6, the resin 7, and the lubricant 8 are prepared before the formation of the 3D binder layer.

[0044] The particle nuclei 3A of the first soft magnetic particles 4 are obtained, for example, by the gas atomization method. That is, each metal that will become the particle nuclei 3A is heated and melted in an electric induction furnace to form molten metal, and the resulting molten metal is ejected from an ejection hole together with a jet of inert gas, argon gas, to obtain metal nanoparticles. Subsequently, the obtained nanoparticles are cooled in water and dried to form the particle nuclei 3A of the first soft magnetic particles 4. The average particle size of the particle nuclei 3A can be adjusted, for example, by adjusting the velocity of the argon gas jet used to eject the molten metal in the gas atomization method and / or the diameter of the ejection hole.

[0045] When forming particle nuclei 3A as amorphous metal, for example, with an average particle size of 20 μm or more, the SWAP (Spinning Water Atomization Process) can be used, in which the metal nanoparticles formed from the molten metal are rapidly cooled by a high-speed rotating water flow.

[0046] During the cooling in water and subsequent drying process described above, the particle nuclei 3A are exposed to a water and / or oxygen atmosphere, thereby forming an oxide film 3B on the surface of the particle nuclei 3A. The thickness of the oxide film 3B can be set to a desired thickness by controlling the exposure time to the water or oxygen atmosphere and / or by controlling the oxygen concentration in the manufacturing environment of the particle nuclei 3A. In addition, the oxide film 3B can be made even thicker on the surface of the particle nuclei 3A by exposing the dried particle nuclei 3A to a high-temperature oxygen atmosphere. It can be assumed that the average particle size of the particle nuclei 3A does not substantially change before and after the formation of the oxide film 3B and the formation of the insulating film 3C described later.

[0047] Furthermore, the oxide film 3B formed on the surface of the particle nucleus 3A does not necessarily require that the metal oxides be uniformly distributed within the film. For example, if one or more metals constituting the particle nucleus 3A can form multiple types of oxides, then different types of oxides may be unevenly distributed within the oxide film 3B, or the oxide film 3B may be composed of multiple layers made of different types of oxides.

[0048] Next, an insulating film 3C is formed on the oxide film 3B formed on the particle nucleus 3A. The insulating film 3C is, for example, a phosphate glass film formed by a mechanochemical method.

[0049] Metal nanoparticles that will become the particle nuclei 5A of the second soft magnetic particles 5 are prepared in the same manner as the first soft magnetic particles 3. Details such as the average particle size of the second soft magnetic particles 5 and the composition of the particle nuclei 5A are as described above. It can be assumed that the average particle size of the particle nuclei 5A does not substantially change before and after the surface treatment described later.

[0050] Next, an insulating film 5B is formed on the surface of the particle nucleus 5A. This insulating film 5B may be formed by a sol-gel reaction, for example, with silica as a component, and as described above, it may include hydrocarbon groups having a linear portion with 8 or more carbon atoms. For example, a sol-gel reaction of a surface treatment agent containing tetraethoxysilane, which is an alkoxide, and a silane coupling agent having the hydrocarbon group described above can be applied to form the insulating film 5B. This allows the insulating film 5B, as a sol-gel reaction product, to be formed on the particle nucleus 5A.

[0051] The above alkoxide is not limited to tetraethoxysilane and can be represented by the chemical formula M-(OR)n. In the formula, the metal species M of the metal alkoxide is preferably one or more selected from the group consisting of Li, Na, Mg, Al, Si, K, Ca, Ti, Cu, Sr, Y, Zr, Ba, Ce, Ta, and Bi. The alkoxy group OR of the metal alkoxide can be any alkoxy group such as a methoxy group, an ethoxy group, and / or a propoxy group.

[0052] The silane coupling agent 6 can be represented by the chemical formula R′-Si(OR)3. In the formula, R′ is a hydrocarbon group having a linear portion with 8 or more carbon atoms, and may be one or more hydrocarbon groups selected from the group consisting of amino groups, epoxy groups, imidazole groups, and mercapto groups. In the formula, OR is an alkoxy group, preferably a methoxy group or an ethoxy group.

[0053] For example, silane coupling agents 6 can include 3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-[2-hydroxy-3-(1H-imidazole-1-yl)propoxy]propyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0054] The resin 7 may be any epoxy resin. The epoxy resin in this invention is not particularly limited, and various known epoxy resins can be used, but those having rigid structures such as multiple aromatic rings are preferred from the viewpoint of mechanical strength.

[0055] Lubricant 8 is an additive used to reduce friction between magnetic powder particles 2 and to facilitate release from the mold during molding. Lubricant 8 can be, for example, metal soaps such as barium sulfate, zinc stearate, calcium stearate, and lithium stearate, long-chain hydrocarbons such as waxes, and silicone oil. As an example, lubricant 8 may contain 0.2 wt% or less of nanosilica and 0.2 wt% or less of lithium stearate based on the total weight of the magnetic material 1.

[0056] Following the preparation step (S1), a pretreatment step (S2) is performed in which a bonding layer 3D is formed on the outer surface of the first soft magnetic particle 4.

[0057] In the pretreatment step (S2), a silane coupling agent is sprayed onto the first soft magnetic particles 4 to form a bonding layer 3D on at least a portion of the surface of the insulating film 3C on the first soft magnetic particles 4, i.e., on the outer circumferential surface of the first soft magnetic particles 4. The method for forming the bonding layer 3D is not limited to spraying the silane coupling agent onto the first soft magnetic particles 4. For example, immersion in the silane coupling agent may also be used. However, the bonding layer 3D formed on the outer circumferential surface of the first soft magnetic particles 3 does not need to extend over the entire outer circumferential surface, as long as it can maintain a predetermined bonding strength with the resin 7. Furthermore, a thinner bonding layer 3D formed on the outer circumferential surface of the first soft magnetic particles 3 is preferable from the viewpoint of maintaining a high relative permeability of the base material after formation.

[0058] Following the pretreatment step (S2), a mixing step (S3) is performed in which the first soft magnetic particles 3 and the second soft magnetic particles 5 are mixed, resin 7 is added and kneaded, and then lubricant 8 is added to produce the magnetic material 1.

[0059] Specifically, in the mixing step (S3), the first soft magnetic particles 3 and the second soft magnetic particles 5 are placed in a powder mixer and mixed to form magnetic powder 2 (S3a). In the mixing step (S3), resin 7 is added to this magnetic powder 2 and the mixture is refined (S3b). Then, in the mixing step (S3), a lubricant is added to the refined material to produce magnetic material 1 (S3c).

[0060] [Examples] In Examples 1 through 8, magnetic material 1 was produced by changing the conditions of the silane coupling agent 6, and sample 1A was prepared by heating and compression molding the produced magnetic material 1. Sample 1A was stored for a predetermined time under a predetermined temperature and humidity environment, and strength tests and MSL tests were performed. After the tests, sample 1A was fractured to observe the fracture surface, and the fracture surface of the fractured fragment 1B was analyzed.

[0061] Furthermore, as comparative examples to the examples, we conducted experiments in two cases: one in which the silane coupling agent 6 was not used when producing magnetic material 1 (Comparative Example 1), and another in which the silane coupling agent 6 was mixed with the resin 7 when producing magnetic material 1 (Comparative Example 2). For both (Comparative Example 1) and (Comparative Example 2), sample 1A was produced and tested and analyzed in the same manner as in (Examples 1) to (Examples 8).

[0062] Examples 1 through 8, Comparative Example 1, and Comparative Example 2 are as shown in the following table.

[0063] [Table 1]

[0064] In Examples 1 to 8, the silane coupling agent 6 was added in the pretreatment step (S2) of the manufacturing process of the magnetic material 1 described above. In Comparative Example 1, the silane coupling agent 6 was not added during the production of the magnetic material 1. In Comparative Example 2, the silane coupling agent 6 (3-aminopropyltrimethoxysilane) was added (blended) to the resin 7 during the production of the magnetic material 1. In Comparative Example 2, the amount of silane coupling agent 6 added was such that the mass ratio (parts by mass) to the first soft magnetic particles 3, with the mass of the first soft magnetic particles 3 being 100, was 0.04. In Examples 1 to 8, Comparative Example 1, and Comparative Example 2, the weight percentage (wt%) of the resin 7 relative to the total weight of the magnetic material 1 was all set to 3.5 wt%. For the resin 7, a biphenyl aralkyl type epoxy resin was used as the epoxy resin, and a biphenyl aralkyl type resin was used as the resin curing agent.

[0065] In Examples 1 to 5, an amine-based silane coupling agent 6 containing an amine group was added in the pretreatment step (S2). Specifically, in Examples 1 to 3, 3-aminopropyltrimethoxysilane was added as the silane coupling agent 6. In Example 4, 3-aminopropyltriethoxysilane (right side) was added as the silane coupling agent 6. In Example 5, 3-(2-aminoethylamino)propyltrimethoxysilane was added as the silane coupling agent 6.

[0066] Furthermore, in Example 1, the amount of 3-aminopropyltrimethoxysilane added was such that the mass ratio (parts by mass) to the first soft magnetic particle 3, with the mass of the first soft magnetic particle 3 being 100, was 0.02. In Example 2, the amount of 3-aminopropyltrimethoxysilane added was such that the above mass ratio (parts by mass) was 0.04. In Example 3, the amount of 3-aminopropyltrimethoxysilane added was such that the above mass ratio (parts by mass) was 0.06. Thus, in Examples 1 to 3, the amount of the same silane coupling agent 6 (3-aminopropyltrimethoxysilane) added was varied to 0.02, 0.04, and 0.06. In Examples 4 and 5, the amount of silane coupling agent 6 added was such that the above mass ratio (parts by mass) was 0.04.

[0067] In Example 6, an epoxy-based silane coupling agent 6 containing an epoxy group was added in the pretreatment step (S2). Specifically, in Example 6, 3-glycidoxypropyltrimethoxysilane was added as the silane coupling agent 6. The amount of silane coupling agent 6 added in Example 6 was such that the mass ratio (parts by mass) was 0.04.

[0068] In Example 7, an imidazole-based silane coupling agent 6 containing an imidazole group was added in the pretreatment step (S2). Specifically, in Example 7, 3-[2-hydroxy-3-(1H-imidazole-1-yl)propoxy]propyltrimethoxysilane was added as the silane coupling agent 6. The amount of silane coupling agent 6 added in Example 7 was such that the mass ratio (parts by mass) was 0.04.

[0069] In Example 8, a mercapto-based silane coupling agent 6 containing a mercapto group was added in the pretreatment step (S2). Specifically, in Example 8, 3-mercaptopropyltrimethoxysilane was added as the silane coupling agent 6. The amount of silane coupling agent 6 added in Example 8 was such that the mass ratio (parts by mass) was 0.04.

[0070] [Sample preparation and testing] Using the magnetic materials produced in (Examples 1) to (Examples 8), (Comparative Example 1), and (Comparative Example 2), a toroidal ring for compression ring strength testing was formed as Sample 1A. The toroidal ring was formed according to the following procedure. (Step 1): Preliminary molding (Place granulated powder in the mold and press) (Step 2): Curing (Preheat the mold, place the pre-formed ring into the mold and preheat, heat and press the ring, remove and further cure in the oven)

[0071] In the preliminary molding (Step 1), 2g of magnetic material was used as the fill material. An air press was used for molding. The mold used for molding had an inner diameter of 8.4mm and an outer diameter of 12.6mm. The molding pressure was 60 MPa and the molding time was 5 seconds.

[0072] In (Procedure 2), a 2g temporary ring (inner diameter 8.4mm, outer diameter 12.6mm) was used as the preparation amount. The equipment used for preheating was a hot plate ND-1A, manufactured by AS ONE Corporation. An air press was used for molding. The equipment used for additional curing was a constant temperature dryer OF-450V, manufactured by AS ONE Corporation. The molding conditions were: molding temperature: 195℃, molding time: 200s, pressure: 20MPa. The additional curing conditions were: oven curing temperature: 200℃, oven curing time: 1hr.

[0073] Furthermore, the electrical resistance (hereinafter referred to as powder resistance) of the first magnetic particles after the pre-processing step (S2) was measured in the powder state before heating and thermal compression. The method for measuring powder resistance was as follows: The measuring device was a Hi-Resta-UX MCP-HT800 (manufactured by Nitto Seikou Analytech Co., Ltd.). In the measuring device, 10g of the sample was pressurized with 20kN, and the measurement was taken with an applied voltage of 10V and an electrode radius of 10mm for the counter electrode (probe). The measurement results of the powder resistance, rounded up, are shown in Table 1. As is clear from Table 1, the powder resistance of Examples 1 to 8 was 10⁹ Ω·cm or higher. Also, since the powder resistance of the comparative example was about 10⁷ Ω·cm, it was shown that the granulated powder in Examples 1 to 8 had a higher dielectric strength than the comparative example.

[0074] A high-temperature pressure ring strength test was performed on sample 1A (toroidal ring) prepared using the procedure described above. This test was carried out according to the following procedure. (Procedure 1): Moisture absorption of sample 1A (toroidal ring) (Procedure 2): High-temperature pressure ring strength test of sample 1A (toroidal ring) after moisture absorption.

[0075] The moisture absorption in (Procedure 1) was carried out in accordance with the JIS moisture absorption treatment in MSL testing, and the conditions (environmental conditions, moisture absorption time) were in accordance with MSL 1. Specifically, in (Procedure 1), 2g of sample 1A (toroidal ring: inner diameter 8mm, outer diameter 13mm) was used as the input quantity. The equipment used was a small environmental testing machine SH-222, manufactured by ESPEC Corporation. The moisture absorption conditions were: environment: 85℃ 85%RH, time: 168hr.

[0076] In (Procedure 2), a test was performed on sample 1A (toroidal ring) after moisture absorption, in accordance with JIS Z2507 (Sintered bearings - Compression ring strength test method). Specifically, in (Procedure 2), the test was performed using sample 1A (toroidal ring: inner diameter 8 mm, outer diameter 13 mm, 2 g) after moisture absorption. The equipment used for the test was model: Autograph AG-20kNXDPlus, manufactured by Shimadzu Corporation. The test method involved placing sample 1A (toroidal ring) between the plates of the equipment so that its axis was parallel to the horizontal plane of the plates. Then, in the test method, sample 1A (toroidal ring) was heated while the plates were pressed down to compress it, and the maximum strength [N / mm^2] at which sample 1A (toroidal ring) was broken was measured. The set temperature during compression was 250°C, and the test speed was 0.1 mm / s.

[0077] The measured intensities for (Examples 1) to (Examples 8), (Comparative Example 1), and (Comparative Example 2) are shown in the table above. Specifically, the maximum intensity was 14 [N / mm^2] in (Example 2), which is shaded in the table. For example, even when the amount (parts by mass) of the same silane coupling agent 6 (3-aminopropyltrimethoxysilane) was changed, the intensity was highest when the amount was 0.04. Also, even when the type of silane coupling agent 6 was changed, the intensity was highest when the silane coupling agent 6 was (3-aminopropyltrimethoxysilane).

[0078] Furthermore, the fractured fragment 1B was subjected to an MSL test evaluation and elemental analysis of the surface of the first soft magnetic particle 3 on the fracture surface. The MSL test evaluation was in accordance with JIS standards for MSL testing. If no deterioration of mechanical properties (cracks, etc.) was observed as a result of the visual inspection of fractured fragment 1B, it was judged as pass (G), and if deterioration was observed, it was judged as fail (NG).

[0079] The MSL test results for (Examples 1) to (Examples 8), (Comparative Example 1), and (Comparative Example 2) are as shown in the table above. Specifically, in (Examples 1) to (Examples 8), in which the silane coupling agent 6 was added in the pretreatment step (S2) of the manufacturing process of the magnetic material 1 described above, the result was a pass (G). In (Comparative Example 1) and (Comparative Example 2), the result was a fail (NG). From this, an improvement in the strength of sample 1A due to the pretreatment step (S2) was observed.

[0080] In elemental analysis of the surface of the first soft magnetic particle 3 on the fracture surface of fracture fragment 1B, Si was detected on the surface by AES (Auger electron spectroscopy). Specifically, qualitative and semi-quantitative analysis was performed using a PHI680 from ULVAC-PHIE.

[0081] Figure 5 is a magnified image of a portion of fracture fragment 1B. As shown in Figure 5, the surface of the first soft magnetic particle 3 exposed on the fracture surface of fracture fragment 1B was analyzed by AES and Si was detected.

[0082] For (Examples 1) to (Examples 8), (Comparative Example 1), and (Comparative Example 2), the detection results of Si by AES (atomic composition percentage: atm%) are as shown in the table above. Specifically, in (Examples 1) to (Examples 8), Si was observed on the surface of the first soft magnetic particles 3. This Si is thought to originate from the silane coupling agent 6 contained in the binding layer 3D on the outer surface of the first soft magnetic particles 3. In contrast, in (Comparative Example 1) and (Comparative Example 2), no Si was observed on the surface of the first soft magnetic particles 3. That is, it was confirmed that by adding the silane coupling agent 6 in the pretreatment step (S2) in the manufacturing process of the magnetic material 1, a binding layer 3D containing the silane coupling agent 6 is formed on the outer surface of the first soft magnetic particles 3. Furthermore, it is thought that the formation of such a binding layer 3D leads to bonding with the resin 7 by the silane coupling agent 6 contained in the binding layer 3D in (Examples 1) to (Examples 8), resulting in higher interfacial strength than in (Comparative Example 1) and (Comparative Example 2).

[0083] Next, for Example 2, which had the highest strength among Examples 1 to 8, Examples 2-1 to 2-5 were performed by changing the weight percentage (wt%) of resin 7 relative to the total weight of magnetic material 1. Then, the magnetic permeability of magnetic material 1 was measured for Examples 2-1 to 2-5. The results for Examples 2-1 to 2-5 are shown in the following table.

[0084] [Table 2]

[0085] Specifically, in (Example 2-1), the weight percentage of resin 7 was 3.5 wt%. In (Example 2-2), the weight percentage of resin 7 was 2.7 wt%. In (Example 2-3), the weight percentage of resin 7 was 4 wt%. In (Example 2-4), the weight percentage of resin 7 was 2 wt%. In (Example 2-5), the weight percentage of resin 7 was 4.5 wt%.

[0086] The equipment used for measuring magnetic permeability was an impedance analyzer E4990A, manufactured by Keysight Technologies. The measurement conditions were: environment: room temperature, measurement frequency: 0.1 to 100 MHz, and analysis: real part permeability μ' (in 1 MHz units).

[0087] As shown in the table above, the magnetic permeability μ was highest at 26 when the weight percentage of resin 7 was 3.5 wt% (shaded). Furthermore, a decrease in magnetic permeability μ was observed when the weight percentage of resin 7 was changed from 3.5 wt% to 2.7 wt% and from 3.5 wt% to 4 wt%. From this, it was found that a weight percentage of resin 7 of 3.5 wt% is more preferable.

[0088] Furthermore, when the weight percentage of resin 7 was 2 wt% (low amount of resin 7), the resin 7 was insufficient, preventing thermal fluidity, and the magnetic powder 2 could not be adequately filled, making it impossible to mold sample 1A. Conversely, when the weight percentage of resin 7 was 4.5 wt% (high amount of resin 7), the excess resin 7 caused the magnetic powder 2 to solidify, making it impossible to mold sample 1A. From this, it was found that setting the resin 7 within a predetermined range (2.7 wt% to 4.0 wt%) is preferable for molding sample 1A.

[0089] [Inductor] This section describes an inductor that uses a base body made by compression molding of magnetic material 1. Figures 6 and 7 are schematic perspective views showing the configuration of the inductor. Specifically, Figure 6 is a perspective view of the top surface 14 of the inductor 100, and Figure 7 is a perspective view of the mounting surface 12 of the inductor 100.

[0090] As shown in Figures 6 and 7, the inductor 100 is configured as a surface-mount type electronic component and comprises a substantially rectangular parallelepiped body 10 formed by compression molding of a magnetic material 1, and a pair of external electrodes 20 provided on the surface of the body 10. In the inductor 100, one side of the body 10 is configured as a mounting surface 12 that is mounted on the surface of a circuit board (not shown). The body 10 is covered with a body protective film 50, except for the external electrodes 20.

[0091] Hereinafter, in the base body 10, the surface opposite the mounting surface 12 will be referred to as the top surface 14, and of the four side surfaces other than the mounting surface 12 and the top surface 14, the pair of surfaces on which the lead-out portion 34 of the coil 30 (described later) is located will be referred to as the first side surface 16, and the remaining pair of surfaces will be referred to as the second side surface 18. These first side surface 16 and second side surface 18 are also surfaces of the base body 10 located in the radial direction of the winding portion 32 of the coil 30 (described later). Hereinafter, the opposing mounting surface 12 and top surface 14 will also be referred to as the pair of main surfaces.

[0092] The length from the mounting surface 12 to the top surface 14 is defined as the thickness T of the element 10. The length of the short side of the top surface 14 is defined as the width W of the element 10. The length of the long side of the first soft magnetic particle 4 is defined as the length L of the element 10.

[0093] Figure 8 is a perspective view showing the internal structure of the inductor 100. As shown in Figure 8, the base body 10 comprises a coil 30 and a core 40 in which the coil 30 is embedded, and is configured as a coil-enclosed magnetic component in which the coil 30 is sealed within the core 40. The coil 30 is an air-core coil component in which a conductor 31 is wound. The core 40 is a molded body that is compressed into a roughly rectangular parallelepiped shape by compacting a mixture of soft magnetic powder and resin with the coil 30 enclosed inside.

[0094] The coil 30 comprises a winding section 32 around which a conductor 31 is wound, and a pair of lead-out sections 34 drawn out from the winding section 32. The winding section 32 is formed by winding the conductor 31 in a spiral shape so that both ends of the conductor 31 are located on the outer circumference and connected to each other on the inner circumference. Inside the base body 10, the coil 30 is embedded in the core 40 in a position where the central axis K of the winding section 32 is aligned with the direction of the thickness T of the base body 10. The lead-out sections 34 are drawn out from the winding section 32 to each of the pair of first side surfaces 16.

[0095] Figure 9 is a cross-sectional view showing a cross-section perpendicular to the longitudinal direction of the conductor wire 31 used in the coil 30. The conductor wire 31 used to form the coil 30 is composed of a copper wire 36 and an insulating coating material 60 covering the copper wire 36. The insulating coating material 60 has an electrically insulating insulating coating layer 61 and a fusion layer 62 formed on the insulating coating layer 61. In the coil formation process, the fusion layer 62 melts when the conductor wire 31 is wound while being heated, causing the conductor wires 31 in the wound section 32 to stick together, and preventing deformation of the wound section 32 after coil formation. In addition, the insulating coating layer 61 reliably insulates the coil 30 from the core 40.

[0096] The pair of external electrodes 20 are L-shaped members extending from each of the first side surfaces 16 of the base body 10 to the mounting surface 12. Each external electrode 20 is connected to the lead-out portion 34 of the coil 30 on the first side surface 16. The portion 20A extending to the mounting surface 12 is electrically connected to the wiring of the circuit board by appropriate mounting means such as soldering.

[0097] An inductor 100 with such a configuration is, for example, a power inductor and is used as a choke coil in DC-DC converter circuits and power supply circuits where large currents flow, in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, and medical and industrial machinery. However, the applications of the inductor 100 are not limited to these, and it can also be used in filter circuits, rectifier and smoothing circuits, for example.

[0098] [Overview of the Inductor Manufacturing Process] Figure 10 is an explanatory diagram illustrating the outline of the manufacturing process of the inductor 100. As shown in Figure 10, the manufacturing process of the inductor 100 includes a granulation process (S11), a coil formation process (S12), a base material molding and hardening process (S13), a base material grinding process (S14), a base material protective film formation process (S15), a base material protective film removal process (S16), and an external electrode formation process (S17).

[0099] The granulation process (S11) is a process for granulating the magnetic material 1 contained in the core 40. Specifically, the granulation process (S11) corresponds to the manufacturing process of the magnetic material 1 described above.

[0100] The coil formation process (S12) is a process of forming a coil 30 from a conductor 31 covered with an insulating coating material 60. In this process, the coil 30 is formed in a shape having the aforementioned winding portion 32 and a pair of lead portions 34 by winding the conductor 31 in a winding method called "alpha winding". Alpha winding refers to a state in which the conductor 31, which functions as a conductor, is wound in a spiral shape in two stages such that the lead portions 34 at the beginning and end of the winding are located on the outer circumference. The number of turns of the coil 30 is not particularly limited, but for example it is 6.5 turns.

[0101] The base body molding and hardening process (S13) is a process for molding a molded body that will form the base body 10. The magnetic material 1 obtained in the granulation process is used as the molding material for the molded body.

[0102] In the base molding and hardening process (S13), the magnetic material 1 is pre-molded to create tablets (solid objects of a predetermined shape), and these tablets and the coil 30 are placed in the cavity of the molding die. Next, the cavity is heated and pressurized using a punch to compress and mold the molded body containing the coil 30. After that, in the base molding and hardening process (S13), the hardened molded body is removed from the cavity and polished. Barrel polishing is used for this polishing, which allows for rounding of the corners of the molded body.

[0103] Figure 11 is an explanatory diagram illustrating one aspect of the base body formation. As shown in Figure 11, the pre-molded tablets use two types of tablets: a first tablet 70 with an appropriate shape (e.g., an E-shaped cross-section) having a groove 71 into which the coil 30 fits, and a second tablet 72 with an appropriate shape (e.g., an I-shaped cross-section or a plate-like shape) covering the groove 71 of the first tablet 70. During compression molding, the first tablet 70 with the coil 30 fitted into the groove 71 and the second tablet 72 are placed on top of each other in the cavity 75 of the molding die 74. Then, while applying heat to the first tablet 70 and the second tablet 72, pressure is applied using a punch 76 from the side of the first tablet 70 and / or the second tablet 72 (the side of the second tablet 72 in the example of Figure 6) in the direction of overlapping, thereby integrating the first tablet 70, the coil 30, and the second tablet 72. Alternatively, instead of pre-molded tablets, the magnetic material 1 obtained in the granulation process may be directly placed into the cavity and compressed.

[0104] The pressure applied during compression molding is preferably such that the first soft magnetic particles 3 and 4 constituting the magnetic powder 2 maintain their pre-molding shape without being crushed after the molding of the base body 10. This pressure suppresses damage to the insulating films 3C and 5B on the surface of the first soft magnetic particles 3 and 4, thereby suppressing a decrease in insulation performance (i.e., a decrease in withstand voltage performance).

[0105] The base body grinding process (S14) is a process in which abrasive grains are applied to the second side surface 18 of the molded body obtained in the base body molding and hardening process (S13) to grind away the second side surface 18 until the width W becomes a predetermined width. This process yields a base body 10 with the width W of the molded body downsized to a predetermined width. This downsizing reduces the distance (also called the side gap) between the coil 30 and the second side surface 18 within the base body 10, thereby increasing the occupancy rate of the coil 30 in the radial direction of the winding portion 32 of the coil 30. Furthermore, since the base body 10 is obtained by grinding the molded body obtained by compression molding to a predetermined size, dimensional variations of the base body 10 can be reduced compared to the case where the base body 10 is controlled to a predetermined size by compression molding alone. Note that in the base body grinding process (S14), polishing (for example, barrel polishing) may be performed to chamfer the corners created by grinding the second side surface 18. Furthermore, if downsizing of the base body 10 is not required, the base body grinding process (S14) may be omitted, and the process may proceed to the base body protective film formation process (S15).

[0106] The base body protective film formation step (S15) is a step in which a base body protective film 50 is formed on the entire surface of the base body 10 that has been ground to a predetermined size in the base body grinding step (S14).

[0107] The material used for the protective film 50 of the substrate may be a thermosetting resin such as epoxy resin, polyimide resin, or phenolic resin, or a thermoplastic resin such as polyethylene resin or polyamide resin. These resins may further contain fillers such as silicon dioxide or titanium dioxide.

[0108] In the substrate protective film formation step (S15), the material for the substrate protective film 50 is applied to the entire surface of the substrate 10 by appropriate means such as coating or dipping, and the substrate protective film 50 is formed by curing it.

[0109] The base body protective film removal step (S16) is a step in which a laser is irradiated onto the base body 10, whose entire surface is covered with the base body protective film 50, to remove the base body protective film 50 from the electrode formation area (for example, a predetermined area within the first side surface 16) where the external electrode 20 is formed, and the insulating coating material 60 of the lead-out portion 34 of the coil 30 that is exposed at the electrode formation area. In addition, in the base body protective film removal step (S16), after the removal of the insulating coating material 60 by laser, etching may be performed to clean the surface of the electrode formation area.

[0110] The external electrode formation step (S17) is a step in which an external electrode 20 is formed by plating at the electrode formation location where the protective film 50 of the base material was removed in the base material protective film removal step (S16). Note that the external electrode formation step (S17) may be performed before the protective film formation step (S16).

[0111] In the external electrode formation process (S17), the external electrode 20 is formed by plating the magnetic material 1 exposed on the surface of the base body 10 and the lead portion 34 of the coil 30. In this plating process, the external electrode 20 is formed by forming a layer made of copper (Cu) by plating growth. Alternatively, a layer made of nickel (Ni) and a layer made of tin (Sn) may be laminated on top of the copper (Cu) layer by plating growth in that order. In addition, layers of aluminum (Al), silver (Ag), gold (Au), or palladium (Pd) may be used instead of the copper (Cu) layer.

[0112] Furthermore, the external electrode 20 may be formed using sputtering, conductive resin, copper plate, or the like. Also, the external electrode 20 is not limited to the L-shape shown in the illustration, but may be a so-called five-sided electrode structure, or a bottom electrode.

[0113] As described above, the inductor 100 manufactured using magnetic material 1 can maintain the mechanical strength of the core 40. Specifically, the inductor 100 can maintain sufficient mechanical strength to withstand high pressure inside the base body 10, even when absorbed moisture rapidly evaporates during reflow soldering. Therefore, the inductor 100 can prevent cracks from forming inside the base body 10 and reduce the inductance.

[0114] All embodiments and modifications described above illustrate one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, any elements of the embodiments described above can be combined to form new embodiments.

[0115] Furthermore, unless otherwise specified, the directions such as horizontal, orthogonal, and vertical, as well as various numerical values, shapes, and materials in the embodiments described above, include a range that produces the same effects as those directions, numerical values, shapes, and materials (the so-called equivalence range).

[0116] [Configurations supported by the above embodiment] The embodiments described above support the following configurations.

[0117] (Configuration 1) A magnetic material comprising a magnetic powder containing first magnetic particles and second magnetic particles having a smaller particle diameter than the first magnetic particles, and a resin, wherein a binding layer containing a silane coupling agent is formed on at least a portion of the outer surface of the first magnetic particles. According to the magnetic material described in Configuration 1, high mechanical strength can be achieved after compression molding.

[0118] (Configuration 2) The magnetic material according to Configuration 1, wherein elemental analysis of the surface of the first magnetic particle on which the binding layer is formed detects 10 atm% or more of Si. According to the magnetic material described in Configuration 2, Si originating from the silane coupling agent contained in the binding layer formed on at least a portion of the outer surface of the first magnetic particle can be detected. Therefore, it can be confirmed that high mechanical strength is achieved at the outer surface (interface) of the first magnetic particle by the silane coupling agent.

[0119] (Configuration 3) The magnetic material according to Configuration 2, wherein the elemental analysis is performed on the fracture surface after the magnetic material has been compressed and then stored for a predetermined time under a predetermined temperature and humidity environment. According to the magnetic material described in configuration 3, when the magnetic material after compression formation is stored for a predetermined time under a predetermined temperature and humidity environment, Si originating from the silane coupling agent contained in the binding layer formed on at least a portion of the outer surface of the first magnetic particles can be detected.

[0120] (Configuration 4) The magnetic material according to any one of Configurations 1 to 3, wherein an insulating film containing low-melting-point glass is formed on the surface of the particle nucleus of the first magnetic particle. According to the magnetic material described in configuration 4, a low melting point can be achieved when forming an insulating film on the surface of the particle nucleus of the first magnetic particle, and the insulating film can be easily formed.

[0121] (Configuration 5) The magnetic material according to any one of Configurations 1 to 4, wherein the particle nucleus of the first magnetic particle is either an Fe-Si alloy or an Fe-Si-Cr amorphous alloy. According to the magnetic material described in Configuration 5, high magnetic permeability can be achieved by using either an Fe-Si alloy or an Fe-Si-Cr amorphous alloy as the particle nucleus of the first magnetic particle.

[0122] (Configuration 6) The magnetic material according to Configuration 4, wherein the low-melting-point glass is zinc phosphate. According to the magnetic material described in configuration 6, zinc phosphate can be used as the low-melting-point glass.

[0123] (Configuration 7) A magnetic material according to any one of Configurations 1 to 6, wherein an insulating film containing silica is formed on the surface of the particle nucleus of the second magnetic particle. According to the magnetic material described in configuration 7, an insulating film can be easily formed on the surface of the particle nucleus of the second magnetic particle.

[0124] (Configuration 8) The magnetic material according to any one of Configurations 1 to 7, wherein the particle nucleus of the second magnetic particle is an Fe-based crystalline alloy. According to the magnetic material described in Configuration 8, high magnetic permeability can be achieved by using an Fe-based crystalline alloy as the particle nucleus for the second magnetic particle.

[0125] (Configuration 9) The magnetic material according to any one of Configurations 1 to 8, wherein the silane coupling agent comprises an amino group, an epoxy group, an imidazole group, and a mercapto group. According to the magnetic material described in configuration 9, high mechanical strength can be achieved at the interface of the first magnetic particle through chemical bonding with the resin at the outer surface (interface) of the first magnetic particle.

[0126] (Configuration 10) A magnetic material according to any one of Configurations 1 to 9, wherein the mass ratio of the silane coupling agent to the first magnetic particles, when the mass of the first magnetic particles is set to 100, is 0.02 or more and 0.06 or less. According to the magnetic material described in configuration 10, the mechanical strength at the interface of the first magnetic particles can be further increased by the silane coupling agent.

[0127] (Configuration 11) The magnetic material according to any one of Configurations 1 to 10, wherein the resin is an epoxy resin. The magnetic material described in configuration 11 can enhance the thermosetting properties of the magnetic material. Furthermore, it can improve fluidity (slipperiness) during compression forming.

[0128] (Configuration 12) The weight percentage of the resin relative to the total weight of the magnetic material is 2.7 or more and 4.0 or less. A magnetic material as described in any one of configurations 1 to 11. According to the magnetic material described in configuration 12, the inductor base body can be properly formed by compression molding.

[0129] (Configuration 13) The magnetic material according to any one of Configurations 1 to 12, wherein the insulation resistance of the first magnetic particle is 10⁹ Ω·cm or more. According to the magnetic material described in configuration 13, the dielectric strength of a body formed by compression molding can be increased.

[0130] (Configuration 14) A method for manufacturing a magnetic material, comprising the steps of: forming a binding layer containing a silane coupling agent on at least a portion of the outer surface of a first magnetic particle; and mixing the first magnetic particle on which the binding layer is formed, a second magnetic particle having a smaller particle diameter than the first magnetic particle, and a resin. According to the method for manufacturing a magnetic material described in configuration 14, it is possible to provide a magnetic material that can achieve high mechanical strength after compression molding.

[0131] (Configuration 15) An inductor comprising a metallic magnetic body made using any one of the magnetic materials described in Configurations 1 to 13, and a coil embedded in the metallic magnetic body. The inductor described in configuration 15 can increase the mechanical strength of a metallic magnetic material. For example, it can prevent cracks from forming in the metallic magnetic material during reflow soldering and prevent a decrease in inductance. [Explanation of Symbols]

[0132] 1...Magnetic material 1A…Sample 1B... Destroyed Fragment 2...Magnetic powder 3, 4...first soft magnetic particle 3A, 5A…Particle nucleus 3B…Oxide film 3C, 5B… Insulating film 5...Second soft magnetic particle 6…Silane coupling agent 7… Resin 8… Lubricant 10... Base body 12…Implementation aspects 14…Top surface 16...1st side 18…Second side 20...External electrode 20A…part 30... Coil 31...Conductor 32... Volume 32 34…Drawer part 36...Copper wire 40...cores 50…Protective film for the base body 60…Insulating coating material 61…Insulating coating layer 62...fusion layer 70...First tablet 71...Groove 72...Second tablet 74…Molding die 75... Cavity 76... Punch K…Center axis L...Length T...thickness W…width 100...Inductor

Claims

1. A magnetic powder comprising a first magnetic particle and a second magnetic particle having a smaller particle size than the first magnetic particle, It has resin, A binding layer containing a silane coupling agent is formed on at least a portion of the outer surface of the first magnetic particle. magnetic material.

2. In elemental analysis of the surface of the first magnetic particle on which the binding layer is formed, 10 atm% or more of Si is detected. The magnetic material according to claim 1.

3. The elemental analysis is performed on the fracture surface of the magnetic material after compression formation, after it has been stored for a predetermined time under a predetermined temperature and humidity environment. The magnetic material according to claim 2.

4. An insulating film containing low-melting-point glass is formed on the surface of the particle nucleus of the first magnetic particle. The magnetic material according to claim 1.

5. The particle nucleus of the first magnetic particle is either an Fe-Si alloy or an Fe-Si-Cr amorphous alloy. The magnetic material according to claim 4.

6. The low-melting-point glass is zinc phosphate. The magnetic material according to claim 4.

7. An insulating film containing silica is formed on the surface of the particle nucleus of the second magnetic particle. The magnetic material according to claim 1.

8. The particle nucleus of the second magnetic particle is an Fe-based crystalline alloy. The magnetic material according to claim 7.

9. The silane coupling agent comprises one of an amino group, an epoxy group, an imidazole group, and a mercapto group. The magnetic material according to claim 1.

10. The mass ratio of the silane coupling agent to the first magnetic particle, with the mass of the first magnetic particle being 100, is 0.02 or more and 0.06 or less. The magnetic material according to claim 1.

11. The aforementioned resin is an epoxy resin. The magnetic material according to claim 1.

12. The weight percentage of the resin, based on the total weight of the magnetic material, is 2.7 or more and 4.0 or less. The magnetic material according to claim 1.

13. The insulation resistance of the first magnetic particle is 10⁹ Ω·cm or more. The magnetic material according to claim 1.

14. A step of forming a binder layer containing a silane coupling agent on at least a portion of the outer surface of the first magnetic particle, The process includes a step of mixing first magnetic particles on which the binding layer is formed, second magnetic particles having a smaller particle size than the first magnetic particles, and a resin. A method for manufacturing magnetic materials.

15. A metallic magnetic material composed using the magnetic material described in any one of claims 1 to 13, The metal magnetic material has a coil embedded in it, Inductor.

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