Magnetic material, magnetic core, and inductor

Abstract

The present disclosure provides a magnetic material that can achieve an improvement in the gap-filling properties of a product made from the magnetic material, an improvement in the magnetic permeability of the product, and an improvement in the withstand voltage of the product. The magnetic material comprises a first magnetic powder and a second magnetic powder. The 50% particle size based on the volume-based particle size distribution of the first magnetic powder is greater than the 50% particle size based on the volume-based particle size distribution of the second magnetic powder. The 50% particle size based on the volume-based particle size distribution of the first magnetic powder is 5.5-16.5 μm. The 90% particle size based on the volume-based particle size distribution of the first magnetic powder is not more than 31 μm.

Description

Magnetic materials, magnetic cores and inductors

[0001] The present disclosure relates to magnetic materials, magnetic cores and inductors, and more particularly to magnetic materials, magnetic cores made from magnetic materials and inductors comprising magnetic cores.

[0002] Patent Document 1 discloses a ceramic material that is composed of Fe as a main component, Si with a content of 2.5 mass % or more and 6.5 mass % or less, Cr with a content of 1.0 mass % or more and 10.0 mass % or less, S with a content of 0.0020 mass % or more and 0.0070 mass % or less, and impurities, and the oxygen content in mass ratio is A [ppm], and the specific surface area is B [m ２ / g], the soft magnetic powder is disclosed in which the ratio A / B is 3000 or more and 8000 or less, and the soft magnetic powder is disclosed in which the average particle size is 1.0 μm or more and 20.0 μm or less.

[0003] JP 2024-55483 A

[0004] Magnetic powders are used to produce products such as magnetic cores (powder magnetic cores). However, when miniaturizing devices such as inductors that incorporate products made from magnetic powder, the magnetic core's permeability and withstand voltage must be improved to maintain good performance. Furthermore, when miniaturizing products made from magnetic powder, gap filling during molding is also required to prevent molding defects. It is difficult to fully satisfy all of these performance requirements.

[0005] The object of the present disclosure is to provide a magnetic material, a magnetic core made from the magnetic material, and an inductor including the magnetic core, which can achieve improved gap filling properties, improved magnetic permeability, and improved voltage resistance of products made from the magnetic material.

[0006] A magnetic material according to one embodiment of the present disclosure includes a first magnetic powder and a second magnetic powder. The 50% particle size based on a volume-based particle size distribution of the first magnetic powder is larger than the 50% particle size based on a volume-based particle size distribution of the second magnetic powder. The 50% particle size based on a volume-based particle size distribution of the first magnetic powder is 5.5 μm or more and 16.5 μm or less. The 90% particle size based on a volume-based particle size distribution of the first magnetic powder is 31 μm or less.

[0007] A magnetic core according to one aspect of the present disclosure is made from the magnetic material.

[0008] An inductor according to one aspect of the present disclosure includes a coil and the magnetic core.

[0009] FIG. 1 is a perspective view of an inductor according to an embodiment. FIG. 2 is a cross-sectional view of the inductor of FIG. 1 taken along line X-X. FIG. 3 is a schematic diagram of a cross section of a product made from a magnetic material in which the magnetic powder in the magnetic material does not contain a first magnetic powder and a second magnetic powder. FIG. 4 is a schematic diagram of a cross section of a product made from a magnetic material in which the magnetic material contains a first magnetic powder and a second magnetic powder. FIG. 5 is a schematic diagram of a cross section of a product made from a magnetic material in which the magnetic material contains a first magnetic powder and a second magnetic powder and also contains a surfactant. FIG. 6 is a graph showing the evaluation results of the initial permeability and superimposed permeability for Comparative Example 4 and Examples 9, 10, 11, 2, 12, and 13. FIG. 7 is a graph showing the evaluation results of the superimposed permeability for Examples 2 to 8 and 14 and Comparative Examples 1, 5, 6, 2, 3, and 7. Fig. 8 is a graph showing the measurement results of the initial permeability and superposed permeability for Examples 15, 2, 16, 3, 17, 4, and 18. Fig. 9 is a graph showing the measurement results of the initial permeability and superposed permeability for Examples 6, 19, 20, 21, 7, 22, 23, 8, and 24. Fig. 10 is a graph showing the measurement results of the superposed permeability for Examples 6, 19 to 21, which used a dispersant, and Examples 29 to 31, which used a coupling agent.

[0010] 1. Overview One embodiment of the present disclosure will be described below. Note that the following embodiment is merely one of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design as long as the object of the present disclosure can be achieved. The drawings referred to below are all schematic, and the shapes and dimensions of elements shown in the drawings do not necessarily accurately represent the shapes and dimensions of actual elements.

[0011] The magnetic material of the embodiment contains a first magnetic powder and a second magnetic powder. The 50% particle size (D50) based on a volume-based particle size distribution of the first magnetic powder is larger than the 50% particle size (D50) based on a volume-based particle size distribution of the second magnetic powder. The 50% particle size (D50) based on a volume-based particle size distribution of the first magnetic powder is 5.5 μm or more and 16.5 μm or less. The 90% particle size (D90) based on a volume-based particle size distribution of the first magnetic powder is 31 μm or less.

[0012] In the embodiment, as described above, the first magnetic powder and the second magnetic powder in the magnetic material have a larger D50 value, that is, the first magnetic powder has a D50 of 5.5 μm or more and 16.5 μm or less, and the first magnetic powder has a D90 of 31 μm or less. Therefore, when the magnetic material is molded to produce product 1 (see FIGS. 1 and 2 ), the magnetic material can have good fluidity. Therefore, when the magnetic material is molded, the magnetic material can easily flow into narrow gaps. In other words, the gap-filling ability of product 1 made from the magnetic material can be improved.

[0013] Furthermore, in the magnetic material and in the product 1 made from the resin material, the particles 22 in the second magnetic powder can be arranged in the gaps between the particles 21 in the first magnetic powder. Therefore, the first magnetic powder and the second magnetic powder can be densely packed in the product 1. This can improve the magnetic permeability of the product 1.

[0014] Furthermore, the withstand voltage of the product 1 can be improved. The reason for this is presumed to be as follows.

[0015] Figures 3, 4, and 5 show schematic views of a portion of a cross section of a product 1 in which the magnetic material contains a binder in addition to magnetic powder. Therefore, Figures 3, 4, and 5 show a binder phase 3 formed from the binder. When the magnetic material contains magnetic powder with only one type of particle size distribution, as shown in Figure 3, particles 2 of the magnetic powder may come into contact with each other in the product 1, causing current to flow between the particles 2, which can result in leakage current. However, when the magnetic material contains a first magnetic powder and a second magnetic powder, as shown in Figures 4 and 5, particles 22 of the second magnetic powder can be positioned in the gaps between particles 21 of the first magnetic powder, which tends to create gaps between the particles 21 of the first magnetic powder. As a result, even when the product 1 is placed in an electric field, current is less likely to flow between the particles 21 in the product 1, making leakage current less likely to occur in the product 1. This can improve the voltage resistance of the product 1.

[0016] The product 1 made from the magnetic material is, for example, a magnetic core 10 (powder magnetic core), a yoke, or a magnetic shield. However, the uses of the magnetic material are not limited to these.

[0017] In particular, when manufacturing an inductor 110 including a magnetic core 10 and a coil 20 made from a magnetic material, if the volume-based D50 of the first magnetic powder is larger than the D50 of the second magnetic powder, and if the D50 of the first magnetic powder is 5.5 μm or more and 16.5 μm or less, and the D90 is 31 μm or less, the coil 20 is less likely to be damaged even when the magnetic material is compression-molded to form the magnetic core 10 around the coil 20. In particular, if the coil 20 is coated with an insulating material, damage to the insulating material can be suppressed. Therefore, a decrease in the withstand voltage of the inductor 110 due to damage to the insulating material can be suppressed.

[0018] 2. Magnetic Material The magnetic material of the embodiment will now be described in more detail.

[0019] The first magnetic powder and the second magnetic powder contained in the magnetic material will be described.

[0020] The magnetic material includes magnetic powder, and the magnetic powder includes a first magnetic powder and a second magnetic powder.

[0021] The magnetic powder is a powder of a magnetic material. The magnetic powder is preferably a powder of a soft magnetic material. The magnetic powder is, for example, an iron-based soft magnetic alloy powder. The iron-based soft magnetic alloy powder is a powder containing at least one selected from the group consisting of, for example, soft magnetic iron-silicon (Fe—Si) alloys, soft magnetic iron-aluminum (Fe—Al) alloys, soft magnetic iron-aluminum-silicon (Fe—Al—Si) alloys, soft magnetic iron-silicon-chromium (Fe—Si—Cr) alloys, soft magnetic iron-chromium (Fe—Cr) alloys, soft magnetic iron-nickel (Fe—Ni) alloys, soft magnetic iron-silicon-boron (Fe—Si—B) alloys, soft magnetic iron-nitrogen (Fe—N) alloys, soft magnetic iron-carbon (Fe—C) alloys, soft magnetic iron-boron (Fe—B) alloys, soft magnetic iron-phosphorus (Fe—P) alloys, permendur (Fe—Co), soft magnetic iron-cobalt-vanadium (Fe—Co—V) alloys, Fe-based amorphous alloys, and Fe-based nanocrystalline alloys. The first magnetic powder and the second magnetic powder may contain the same type of material, or may contain different types of materials.

[0022] The 50% particle size (D50) based on the volume-based particle size distribution of the first magnetic powder is larger than the 50% particle size (D50) based on the volume-based particle size distribution of the second magnetic powder. In the embodiment, the volume-based particle size distribution is measured by a laser diffraction / scattering method.

[0023] As described above, the D50 of the first magnetic powder is 5.5 μm or more and 16.5 μm or less. This increases the fluidity of the magnetic material during molding, and can improve the gap-filling ability of the product 1. The D50 of the first magnetic powder is preferably 7.5 μm or more, and even more preferably 9.5 μm or more. The D50 of the first magnetic powder is preferably 15.5 μm or less, and even more preferably 14.5 μm or less.

[0024] Furthermore, the 90% particle size (D90) based on the volume-based particle size distribution of the first magnetic powder is 31 μm or less, thereby reducing the number of relatively coarse particles in the first magnetic powder. This improves the fluidity of the magnetic material during molding, potentially improving the gap-filling ability of the product 1. It is more preferable for the D90 of the first magnetic powder to be 28 μm or less, and even more preferable for it to be 26 μm or less. Furthermore, it is preferable for the D90 of the first magnetic powder to be 11 μm or more. In this case, even if the particle size distribution of the second magnetic powder is the same, there is the advantage that the magnetic permeability of the product 1 can be further improved. It is more preferable for the D90 to be 14 μm or more, and even more preferable for it to be 17 μm or more.

[0025] The ratio of the D50 of the first magnetic powder to the D50 of the second magnetic powder [(D50 of the first magnetic powder) / (D50 of the second magnetic powder)] is preferably 5 or more and 17 or less. That is, the D50 of the second magnetic powder is preferably a value such that the ratio is 5 or more and 17 or less. In this case, the magnetic permeability of the product 1 and the withstand voltage of the product 1 can be more significantly improved. This is presumably because a good balance can be achieved between the improved packing of the magnetic powder due to the second magnetic powder particles 22 being interposed between the first magnetic powder particles 21 and the maintenance of gaps between the first magnetic powder particles. A ratio of 6 or more is more preferable, and a ratio of 12 or more is even more preferable.

[0026] It is preferable that the proportion of the first magnetic powder relative to the total of the first and second magnetic powders be 70% by mass or more and 90% by mass or less. In this case, the magnetic permeability of the product 1 and the voltage resistance of the product 1 can be more significantly improved. This is presumably because a good balance can be achieved between improving the packing of the magnetic powder by having the second magnetic powder particles 22 interposed between the first magnetic powder particles 21 and maintaining the gaps between the first magnetic powder particles. This proportion is more preferably 73% by mass or more, and even more preferably 75% by mass or more. Furthermore, this proportion is more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0027] The magnetic powder in the magnetic material preferably contains only the first magnetic powder and the second magnetic powder. That is, the magnetic powder preferably does not contain a magnetic powder (hereinafter also referred to as a third magnetic powder) having a particle size distribution different from either the first magnetic powder or the second magnetic powder. When the magnetic material contains the third magnetic powder, the amount of the third magnetic powder is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of the total of the first magnetic powder and the second magnetic powder.

[0028] The magnetic material preferably further contains a binder, which can further improve the withstand voltage of the magnetic material and can also improve moldability when molding the magnetic material to produce the product 1.

[0029] The binder is, for example, a thermosetting resin or a thermoplastic resin. When the binder is a thermosetting resin, the product 1 can be produced by molding the magnetic material into an appropriate shape and then curing it. The thermosetting resin may be, for example, liquid or solid. The binder contains at least one selected from the group consisting of, for example, epoxy resin, phenol resin, phenoxy resin, silicone, polyimide, etc.

[0030] When the binder contains a thermosetting resin, the binder may further contain a curing agent as necessary. The curing agent is not particularly limited as long as it is a component that can cure the thermosetting resin. In the present disclosure, the curing agent may include a curing accelerator, a curing catalyst, and a curing aid. The curing agent may contain, for example, at least one selected from the group consisting of a phenol-based curing agent, an acid anhydride-based curing agent, an aliphatic amine-based curing agent, an aromatic amine-based curing agent, an imidazole-based curing accelerator, a tertiary amine, and a phosphorus compound.

[0031] When the magnetic material contains a binder, the total ratio of the first magnetic powder and the second magnetic powder to the magnetic material is preferably 74% by volume or more and 82% by volume or less. If this ratio is 74% by volume or more, the product 1 made from the magnetic material can have particularly high magnetic permeability. If this ratio is 82% by volume or less, particularly when the product 1 is the magnetic core 10 of an inductor 110 including a magnetic core 10 and a coil 20, damage to the insulating material covering the coil 20 can be further suppressed. This is presumably because, when the ratio is 82% by volume or less, the fluidity of the magnetic material is maintained well, thereby reducing the frequency with which the magnetic powder attacks the insulating material. A ratio of 76% by volume or more is more preferable, and a ratio of 78% by volume or more is even more preferable. A ratio of 81% by volume or less is more preferable, and a ratio of 80% by volume or less is even more preferable.

[0032] When the magnetic material contains a binder, it is preferable that the magnetic material contains at least one selected from the group consisting of a dispersant and a coupling agent. In this case, the affinity between the binder and each of the first and second magnetic powders is increased, which can improve the dispersibility of the first and second magnetic powders in the magnetic material and the flowability of the magnetic material.

[0033] Furthermore, by suppressing the aggregation of the second magnetic powder, the first magnetic powder and the second magnetic powder can be packed more densely in the product 1, which can increase the withstand voltage of the product 1. The reason for this is presumably as follows: The particles 22 of the second magnetic powder are more likely to penetrate into the gaps between the particles 21 of the first magnetic powder. This is shown schematically in Figures 4 and 5. If the particles 22 of the second magnetic powder are more likely to aggregate, the particles 22 of the second magnetic powder are less likely to penetrate into the gaps between the particles 21 of the first magnetic powder, as shown in Figure 4. This increases the frequency with which the particles 21 of the first magnetic powder come into contact, which can cause localized current flow between the particles 21. On the other hand, if the particles 22 of the second magnetic powder are less likely to aggregate, the particles 22 of the second magnetic powder are more likely to penetrate into the gaps between the particles 21 of the first magnetic powder, as shown in Figure 5. This increases the frequency with which gaps open up between the particles 21 of the first magnetic powder, making it more difficult for current to flow between the particles 21.

[0034] The surfactant contains, for example, at least one selected from the group consisting of a dispersant and a coupling agent.

[0035] The dispersant contains at least one selected from the group consisting of, for example, polymeric dispersants, surfactant dispersants, and inorganic dispersants. The dispersant is preferably a so-called wetting dispersant, having a compatible chain that bonds with the resin and an adsorptive group that bonds with the magnetic powder. The compatible chain is at least one selected from the group consisting of, for example, fatty acids, polyaminos, polyethers, polyesters, polyurethanes, and polyacrylates. The adsorptive group is at least one selected from the group consisting of, for example, amines, carboxylic acids, phosphoric acids, carboxylates, and phosphates.

[0036] The coupling agent contains at least one selected from the group consisting of, for example, silane coupling agents, titanate coupling agents, aluminate coupling agents, zirconate coupling agents, aluminum chelates, titanium chelates, and zirconium chelates.

[0037] It is particularly preferred if the magnetic material contains a dispersant, which can significantly improve the magnetic permeability, especially the superposed magnetic permeability, of the product 1 and also significantly improve the voltage resistance.

[0038] The amount of dispersant is preferably 0.1 to 10 parts by weight per 100 parts by weight of the total of the first and second magnetic powders, more preferably 0.2 parts by weight or more, and even more preferably 0.4 parts by weight or more, and more preferably 5 parts by weight or less, and even more preferably 3 parts by weight or less.

[0039] The magnetic material preferably does not contain any filler other than the magnetic powder, however, the magnetic material may contain fillers other than the magnetic powder within a range that does not excessively impair the effects of the embodiment.

[0040] When the magnetic material contains a filler other than magnetic powder, the filler other than magnetic powder contains, for example, a powder containing an inorganic material. More specifically, the filler other than magnetic powder contains, for example, a powder containing at least one selected from the group consisting of talc (hydrated magnesium silicate), silica (silicon oxide), alumina (aluminum oxide), boron nitride, magnesium oxide, titanium oxide, zirconium oxide, and mica.

[0041] When the magnetic material contains a filler other than magnetic powder, the amount of filler other than magnetic powder per 100 parts by mass of the total of the first magnetic powder and the second magnetic powder is preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and even more preferably 1 part by mass or less.

[0042] The magnetic material may contain components other than those described above, as long as the effects of the embodiment are not excessively impaired. For example, the magnetic material may contain modifiers, lubricants, etc.

[0043] The magnetic material is manufactured, for example, as follows: However, this manufacturing method of the magnetic material is only an example, and the magnetic material may be manufactured by a method other than the following method.

[0044] The components of the magnetic material are mixed to prepare a mixture. If the components of the magnetic material contain a surfactant, the surfactant and components other than the surfactant may be mixed at once, or the surfactant may be attached to the surfaces of the first magnetic powder and the second magnetic powder in advance, and then the first magnetic powder and the second magnetic powder to which the surfactant has been attached may be mixed with the other components. After kneading the mixture, a solvent is added to the mixture and the mixture is granulated using a granulator or the like. The mixture is then dried to remove the solvent from the mixture. The mixture is then pulverized and, if necessary, further classified to obtain a powdered magnetic material. Note that the magnetic material is not limited to a powder.

[0045] 3. Products, Magnetic Cores, and Inductors As described above, the product 1 made from a magnetic material is, for example, a magnetic core 10 (powder magnetic core 10), a yoke, or a magnetic shield. The product 1 is obtained by molding the magnetic material. There are no restrictions on the specific molding method for molding the magnetic material, but when the magnetic material contains a binder including a thermosetting resin, compression molding, for example, can be applied.

[0046] There is no limit to the pressure (molding pressure) that can be applied to the magnetic material when compressing and molding the magnetic material, but in this embodiment, the fluidity of the magnetic material is good, so that the product 1 can have good gap-filling properties even if the pressure is relatively low. Note that a relatively low molding pressure means, for example, a molding pressure of 0.01 ton / cm ２ 4ton / cm or more ２ This means a pressure of 0.98 MPa or more and 392.27 MPa or less. Therefore, for example, when manufacturing an inductor 110 including a magnetic core 10 made of a magnetic material and a coil 20, even if the magnetic material is compression-molded to form the magnetic core 10 around the coil 20, the coil 20 is unlikely to be damaged. Therefore, for example, when the coil 20 is coated with an insulating material, a decrease in the withstand voltage of the inductor 110 due to damage to the insulating material can be suppressed. Furthermore, even when manufacturing a small inductor 110 equipped with a particularly small coil, the magnetic core 10 can have good gap-filling properties.

[0047] The heating conditions when compression molding the magnetic material can be set appropriately depending on the type of thermosetting resin, etc. For example, the heating temperature is 100° C. or higher and 200° C. or lower, and the heating time is 10 seconds or higher and 30 minutes or lower.

[0048] A specific example of a magnetic core 10 made from a magnetic material and an inductor 110 including this magnetic core 10 will be described with reference to FIGS.

[0049] The inductor 110 comprises a coil 20, a first connection terminal 31 and a second connection terminal 32 connected to one end (first end 211) and the end opposite the first end 211 (second end 212), respectively, of the coil 20, and a magnetic core 10.

[0050] The coil 20, the first connection terminal 31, and the second connection terminal 32 are each made of a conductor such as copper. The coil 20 is, for example, an edgewise coil formed by winding a rectangular wire. However, the coil 20 may also be a wound coil formed by winding a round wire. The surface of the coil 20 is preferably covered with an insulating material.

[0051] The magnetic core 10 contains a coil. It can also be said that the coil is embedded in the magnetic core 10. The magnetic core 10 can be produced by molding a magnetic material around the coil. The first connection terminal 31 and the second connection terminal 32 are each disposed along the outer surface of the magnetic core 10.

[0052] The magnetic core 10 made from the magnetic material of the embodiment can have high magnetic permeability and high withstand voltage, which allows the inductor 110 to have high performance, and by miniaturizing the inductor 110, the performance of the inductor 110 can be maintained at a good level even when the magnetic core 10 is miniaturized.

[0053] Furthermore, when the magnetic material is molded to produce the magnetic core 10, the magnetic material easily flows into narrow gaps. That is, the gap-filling ability of the magnetic core 10 manufactured from the magnetic material can be improved. This can suppress molding defects such as insufficient filling of the magnetic core 10. In particular, when the magnetic core 10 is miniaturized due to the miniaturization of the inductor 110, molding defects due to insufficient filling of the magnetic core 10 become a problem. However, in the embodiment, the occurrence of molding defects due to the miniaturization of the magnetic core 10 can be suppressed.

[0054] For this reason, the magnetic material of the embodiment is particularly suitable for producing the magnetic core 10 in the small inductor 110. For example, when the minimum dimension of one side of the magnetic core 10 is 0.5 mm or more and 5 mm or less, or when the volume of the magnetic core 10 is 0.5 mm or less, ３ More than 50 mm ３ Even if the magnetic core 10 is less than this, it is possible for the magnetic core 10 to have high magnetic permeability, high withstand voltage, and good gap-filling properties, and the inductor 110 including this magnetic core 10 can have good performance.

[0055] More specific examples of this embodiment will be described below. Note that the following examples do not limit the aspects of this embodiment.

[0056] 1. Preparation of Magnetic Material A magnetic material was prepared by the following method.

[0057] Using the components shown in the table, the first magnetic powder, the second magnetic powder, and the dispersant were first kneaded in a mortar with a small amount of methyl ethyl ketone to obtain a mixture. Next, a binder and a small amount of methyl ethyl ketone were further added to this mixture, and the mixture was further kneaded in the mortar. The mixture was then dried at 50°C for 30 minutes, pulverized, and further classified so that the maximum particle size was 500 μm or less. This resulted in a powdered magnetic material.

[0058] The details of the components shown in the table are as follows: - First magnetic powder: FeSiCr alloy powder. - Second magnetic powder: FeSiCr alloy powder. - Binder: Epoxy resin. - Dispersant: Phosphate ester-based dispersant. Manufactured by BYK-Chemie. Product name: BYK-9076. - Coupling agent A: Silane coupling agent. Manufactured by Shin-Etsu Chemical Co., Ltd. Product name: KBM-403. - Coupling agent B: Silane coupling agent. Manufactured by Shin-Etsu Chemical Co., Ltd. Product name: KBM-573. - Coupling agent C: Al-based coupling agent. Manufactured by Ajinomoto Fine-Techno Co., Ltd. Product name: AL-M.

[0059] (1) Viscosity of the magnetic material The viscosity of the magnetic material was measured using a flow tester (CFT-500EX, manufactured by Shimadzu Corporation) to measure the flow rate at 175°C, and the viscosity was calculated from the results. The lower this viscosity, the better the flowability of the magnetic material can be determined.

[0060] (2) Sample Production Samples were produced by compression molding the magnetic material. The heating conditions during compression molding were a heating temperature of 175°C and a heating time of 2 minutes. The molding pressure was as shown in the table. The shape of the sample was a toroidal shape with an outer diameter of 14.4 mm, an inner diameter of 10.3 mm, and a thickness of approximately 2 mm for the tests "(3) Initial Permeability and Superposed Permeability" and "(4) Magnetic Loss, Hysteresis Loss, and Eddy Current Loss" below, and a disk shape with a diameter of 12 mm and a thickness of approximately 1 mm for the test "(5) Withstand Voltage" below.

[0061] (3) Initial Permeability and Superposed Permeability Regarding the permeability and DC superposition characteristics of the sample, a 30-turn winding was applied to the prepared toroidal-shaped sample, and a DC Bias Current Test System (LM-2102: manufactured by Kokuyo Electric Industrial Co., Ltd.) and an LCR meter (KC-601: manufactured by Kokuyo Electric Industrial Co., Ltd.) were used to apply a predetermined DC current and measure the L value, and the permeability and applied magnetic field were calculated.

[0062] If the initial permeability is 30 or more, it can be evaluated that the relative dielectric constant of the product is particularly improved. If the superposed permeability is 22 or more, it can also be evaluated that the relative dielectric constant of the product is particularly improved.

[0063] (4) Magnetic Loss, Hysteresis Loss, and Eddy Current Loss The magnetic loss, hysteresis loss, and eddy current loss of the sample were measured as follows: The toroidal sample was wound with 20 turns of primary winding and 20 turns of secondary winding, and the magnetic loss was measured at Bm = 25 mT / f = 1 MHz using a BH analyzer (SY-8258, manufactured by Iwatsu Measurement Co., Ltd.).

[0064] Magnetic loss is 850kW / m ３ If the eddy current loss is 400 kW / m or less, it can be evaluated that the performance as a magnetic core is particularly improved. ３ Even when the following conditions are met, it can be evaluated that the performance of the magnetic core is particularly improved.

[0065] (5) Withstand Voltage The withstand voltage of the sample was measured as follows: Using an ultra-high resistance / low current measuring instrument (R8340A, manufactured by ADVANTEST), a disk-shaped sample was sandwiched between probes from above and below, and voltage was applied in 10 V increments. The measured voltage immediately preceding the voltage at which the current value increased significantly (10 mA or more) was divided by the sample thickness, and the resulting value was taken as the withstand voltage (V / mm).

[0066] If the withstand voltage is 60 V / mm or more, it can be evaluated that the withstand voltage of the product is particularly improved.

[0067] (6) Coil Damage Resistance: Coil damage evaluation during molding of the magnetic material was performed using the following method. Approximately 1 g of magnetic material was spread in a mold with inner dimensions of 14 mm x 11 mm, and a wound coil coated with a coating material was placed on top of that. Another approximately 1 g of magnetic material was then placed on top of that. The magnetic material was then compressed at the molding pressure shown in the table, and the wound coil alone was removed from the mold. This simulated a load on the wound coil similar to that applied during molding of the magnetic material. Next, an underwater pressure test was performed on the wound coil to confirm the applied voltage immediately before dielectric breakdown occurred in the insulating material coating the wound coil. This applied voltage was defined as the coil withstand voltage. As a result, a coil withstand voltage of 30 V or more was evaluated as "good," a coil withstand voltage of 20 V or more but less than 30 V was evaluated as "fair," and a coil withstand voltage of less than 20 V was evaluated as "poor."

[0068] (7) Gap-filling property The gap-filling property of the sample was evaluated by the following method. To index the gap-filling property, molding dies were prepared with five different gaps: 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm. Approximately 1 g of magnetic material was taken and molded at a temperature of 175°C and a molding pressure of 1 ton / cm. ２ The mixture was subjected to heat compression molding under conditions of a pressure of 98.14 MPa and a pressure time of 2 minutes. The presence or absence of unfilled magnetic material in each of the five types of gaps was confirmed. The gap filling ability was evaluated based on the value of the narrowest gap where no unfilled magnetic material was present.

[0069] If this result is 40 μm or less, it can be evaluated that the gap filling ability is particularly improved.

[0070] 3. Evaluation Results The results of the above evaluation tests are shown in the table.

[0071] (1) Overall Evaluation As shown in the results summarized in Tables 1 and 2 below, it was confirmed that in the examples in which the D50 of the first magnetic powder was 5.5 μm or more and 16.5 μm or less and the D90 of the first magnetic powder was 31 μm or less, the evaluations of magnetic permeability, magnetic loss, voltage resistance, coil damage resistance, and gap filling ability tended to be better than those of the comparative examples.

[0072]

[0073]

[0074] (2) Evaluation of the mixing ratio of the first magnetic powder to the second magnetic powder As shown in the results summarized in Table 3 below, when the proportion of the first magnetic powder was 70% by mass or more and 90% by mass or less, an excellent evaluation was obtained, and the magnetic permeability in particular tended to improve.

[0075] 6 shows the evaluation results of the initial permeability and superimposed permeability for Comparative Example 4 and Examples 9, 10, 11, 2, 12, and 13. As shown in this figure, it can be confirmed that the initial permeability and superimposed permeability are particularly high when the proportion of the first magnetic powder is 70% by mass or more and 90% by mass or less.

[0076]

[0077] (3) Evaluation of particle size ratio between first magnetic powder and second magnetic powder 1 As shown in the results summarized in Tables 4 and 5 below, when the ratio of the D50 of the first magnetic powder to the D50 of the second magnetic powder was 5 or more and 17 or less, an excellent evaluation was obtained, and there was a tendency for the superposition permeability in particular to improve.

[0078] 7 shows the evaluation results of the superposed magnetic permeability for Examples 2 to 8 and 14 and Comparative Examples 1, 5, 6, 2, 3 and 7 shown in Tables 4 and 5. As shown in this figure, it can be confirmed that the superposed magnetic permeability is particularly high when the ratio of D50 of the first magnetic powder to D50 of the second magnetic powder is 5 or more and 17 or less.

[0079]

[0080]

[0081] (4) Evaluation 2 of particle size ratio between first magnetic powder and second magnetic powder As shown in the results summarized in Tables 6, 7 and 8 below, when the ratio of D50 of the first magnetic powder to D50 of the second magnetic powder was particularly 12 or more and 17 or less, a particularly excellent evaluation was obtained, and there was a tendency for the magnetic permeability to be maintained well, especially even when the molding pressure during sample manufacturing was low.

[0082] 8 shows the results of measuring the initial permeability and superimposed permeability for Examples 15, 2, 16, 3, 17, 4, and 18, in which the D50 of the first magnetic powder was 11.76 μm. The values ​​0.95 μm, 1.79 μm, and 2.01 μm in the figure represent the D50 of the second magnetic powder. As shown in this figure, in Examples 15, 2, and 16, in which the particle size ratio was 12 to 17 (i.e., the D50 of the second magnetic powder was 0.95 μm), it was confirmed that the initial permeability and superimposed permeability were less likely to decrease than in the other Examples, even when the molding pressure was lower.

[0083] 9 shows the results of measuring the initial permeability and superimposed permeability for Examples 6, 19, 20, 21, 7, 22, 23, 8, and 24, in which the D50 of the first magnetic powder was 16.11 μm. The values ​​0.95 μm, 2.01 μm, and 3.16 μm in the figure represent the D50 of the second magnetic powder. As shown in this figure, in Examples 6, 19, 20, and 21, in which the particle size ratio was 12 to 17 (i.e., the D50 of the second magnetic powder was 0.95 μm), the initial permeability and superimposed permeability were less likely to decrease than in the other Examples, even when the molding pressure was lower.

[0084]

[0085]

[0086]

[0087] (5) Surfactant Evaluation As shown in the results summarized in Tables 9 and 10 below, when a dispersant was used as the surfactant, a particularly superior evaluation was obtained, and there was a tendency for the magnetic permeability to be particularly improved, compared to when a coupling agent was used. Figure 10 shows the results of measuring the superposed magnetic permeability of Examples 6 and 19 to 21, in which a dispersant was used and Examples 29 to 31, in which a coupling agent was used, when the D50 of the first magnetic powder was 16.11 μm and the D50 of the second magnetic powder was 0.95 μm.

[0088]

[0089]

[0090] (6) Evaluation of magnetic powder ratio As shown in the results summarized in Table 11 below, in particular in Examples 33 to 35, 5 and 36, in which the total ratio of the first magnetic powder and the second magnetic powder to the magnetic material is 74% by volume or more and 82% by volume or less, it can be evaluated that the fluidity during molding is excellent while maintaining high magnetic permeability.

[0091]

[0092] [Aspects] As made clear by the above embodiments and examples, the present disclosure includes the following aspects.

[0093] The magnetic material of the first embodiment contains a first magnetic powder and a second magnetic powder. The 50% particle size based on the volume-based particle size distribution of the first magnetic powder is larger than the 50% particle size based on the volume-based particle size distribution of the second magnetic powder. The 50% particle size based on the volume-based particle size distribution of the first magnetic powder is 5.5 μm or more and 16.5 μm or less. The 90% particle size based on the volume-based particle size distribution of the first magnetic powder is 31 μm or less.

[0094] In this embodiment, the magnetic permeability, withstand voltage, and gap-filling ability of a product produced by molding the magnetic material can be improved.

[0095] In a second aspect, in the first aspect, the proportion of the first magnetic powder with respect to the total of the first magnetic powder and the second magnetic powder is 70% by mass or more and 90% by mass or less.

[0096] In this embodiment, the magnetic permeability, withstand voltage, and gap-filling ability of the product produced by molding the magnetic material can be further improved.

[0097] In a third aspect, in the first or second aspect, the ratio of the 50% particle size based on the volume-based particle size distribution of the first magnetic powder to the 50% particle size based on the volume-based particle size distribution of the second magnetic powder is 5 or more and 17 or less.

[0098] In this embodiment, the magnetic permeability, withstand voltage, and gap-filling ability of the product produced by molding the magnetic material can be further improved.

[0099] In a fourth aspect, in any one of the first to third aspects, the magnetic material further contains a binder.

[0100] In this embodiment, the moldability of the magnetic material can be improved.

[0101] In a fifth aspect, the magnetic material according to the fourth aspect further contains a dispersant.

[0102] In this embodiment, the magnetic permeability, withstand voltage, and gap-filling ability of the product produced by molding the magnetic material can be further improved.

[0103] In a sixth aspect, in the fourth or fifth aspect, the total ratio of the first magnetic powder and the second magnetic powder to the magnetic material is 74% by volume or more and 82% by volume or less.

[0104] In this embodiment, the flowability of the product produced by molding the magnetic material during molding can be further improved.

[0105] The magnetic core of the seventh aspect is made from the magnetic material of any one of the first to sixth aspects.

[0106] In this embodiment, the magnetic permeability, withstand voltage, and gap-filling properties of the magnetic core can be improved.

[0107] An inductor according to an eighth aspect includes a coil and the magnetic core according to the seventh aspect.

[0108] 1 Product 10 Magnetic core 20 Coil 110 Inductor

Claims

1. A magnetic material comprising a first magnetic powder and a second magnetic powder, wherein the 50% particle size based on the volumetric particle size distribution of the first magnetic powder is larger than the 50% particle size based on the volumetric particle size distribution of the second magnetic powder, the 50% particle size based on the volumetric particle size distribution of the first magnetic powder is 5.5 μm or more and 16.5 μm or less, and the 90% particle size based on the volumetric particle size distribution of the first magnetic powder is 31 μm or less.

2. The magnetic material according to claim 1, wherein the proportion of the first magnetic powder relative to the total of the first magnetic powder and the second magnetic powder is 70% by mass or more and 90% by mass or less.

3. The magnetic material according to claim 1, wherein the ratio of the 50% particle size based on the volumetric particle size distribution of the first magnetic powder to the 50% particle size based on the volumetric particle size distribution of the second magnetic powder is 5 or more and 17 or less.

4. The magnetic material according to claim 1, further comprising a binder.

5. The magnetic material according to claim 4, further comprising a dispersant.

6. The magnetic material according to claim 4 or 5, wherein the total ratio of the first magnetic powder and the second magnetic powder to the magnetic material is 74% by volume or more and 82% by volume or less.

7. A magnetic core made from the magnetic material according to claim 1.

8. An inductor comprising a coil and the magnetic core according to claim 7.

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