Insulator-coated soft magnetic powder, method for producing insulator-coated soft magnetic powder, dust core, magnetic element, electronic device, and mobile body

Abstract

To provide an insulator coated soft magnetic powder capable of manufacturing a magnetic element in which an eddy current loss in a high frequency domain is sufficiently suppressed, a manufacturing method thereof, a powder magnetic core including the insulator coated soft magnetic powder, the magnetic element comprising the powder magnetic core, an electronic apparatus comprising the magnetic element, and a mobile.SOLUTION: The present invention relates to an insulator coated soft magnetic powder comprising an Fe-based alloy soft magnetic powder and an insulation coating with which a particle surface of the Fe-based alloy soft magnetic powder is coated. When a particle size in which an accumulation of frequencies in a granularity distribution in a volume reference of the Fe-based alloy soft magnetic powder is 50% is defined as D50, D50 is equal to or more than 0.1 μm and equal to or less than 3.0 μm. When a particle size in which the accumulation of frequencies in the granularity distribution in the volume reference of the Fe-based alloy soft magnetic particle is 90% is defined as D90, a ratio of D90 / D50 is equal to or less than 2.00.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an insulator-coated soft magnetic powder, a method for producing an insulator-coated soft magnetic powder, a dust core, a magnetic element, an electronic device, and a mobile object. [Background technology]

[0002] Patent Document 1 discloses an amorphous alloy powder having a D90 / D10 ratio of 3.3 to 6.5 and a D50 of 5 μm to 20 μm. D90 is the particle size at 90% cumulative from the smallest diameter side in a volume-based particle size distribution, D10 is the particle size at 10% cumulative, and D50 is the particle size at 50% cumulative. Such amorphous alloy powders have excellent filling properties during powder compaction, making it possible to manufacture powder cores with high mechanical strength, saturation magnetic flux density, and magnetic permeability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-15357 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, efforts have been made to improve communication speeds in various communication devices. For this reason, magnetic elements are increasingly being used in the high-frequency range of 1 MHz or higher. However, the powder magnetic core using the amorphous alloy powder described in Patent Document 1 is unable to sufficiently reduce core loss in the high-frequency range. Therefore, there is a demand for soft magnetic powder that can reduce core loss in the high-frequency range of 1 MHz or higher, preferably 10 MHz or higher. [Means for solving the problem]

[0005] The insulator-coated soft magnetic powder according to the application example of the present invention is Atomized powderFe-based alloy soft magnetic powder and particles of said Fe-based alloy soft magnetic powder an insulating coating covering the terminal surface; The cumulative frequency of the particle size distribution of the Fe-based alloy soft magnetic powder on a volume basis is 50%. When the particle diameter is D50, D50 is 0.1 μm or more and 1.5 μm or less, The cumulative frequency of the particle size distribution of the Fe-based alloy soft magnetic powder on a volume basis is 90%. When the particle size is D90, the ratio of D90 / D50 is 2.00 or less. .

[0006] A method for producing an insulator-coated soft magnetic powder according to an application example of the present invention includes the steps of: The Fe-based alloy raw material powder was classified in a liquid, and the cumulative frequency of the particle size distribution on a volume basis was 50 % particle diameter is defined as D50, and D50 is 0.1 μm or more 1.5μm or less And In addition, when the particle size at which the cumulative frequency is 90% in the particle size distribution on a volume basis is defined as D90, A liquid classification process for extracting Fe-based alloy soft magnetic powder having a D90 / D50 ratio of 2.00 or less. The degree, The Fe-based alloy soft magnetic powder is coated with an insulating coating to form an insulating coating on the particle surface. a synthesis process; The present invention is characterized by having the following.

[0007] A powder magnetic core according to an application example of the present invention includes: The present invention is characterized by including an insulating-material-coated soft magnetic powder according to an application example of the present invention.

[0008] The magnetic element according to the application example of the present invention includes: The present invention is characterized by including a powder magnetic core according to an application example of the present invention.

[0009] The electronic device according to the application example of the present invention includes: The magnetic element according to the application example of the present invention is included.

[0010] A moving body according to an application example of the present invention includes: The magnetic element according to the application example of the present invention is included. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view schematically showing one particle of an insulator-coated soft magnetic powder according to an embodiment. FIG. [Figure 2] 1 is a process diagram illustrating a method for producing an insulator-coated soft magnetic powder according to an embodiment. [Figure 3] FIG. 1 is a plan view schematically showing a toroidal type coil component. [Figure 4] FIG. 1 is a transparent perspective view schematically showing a closed magnetic circuit type coil component. [Figure 5] FIG. 1 is a perspective view showing a mobile personal computer, which is an electronic device including a magnetic element according to an embodiment. [Figure 6] FIG. 1 is a plan view showing a smartphone as an electronic device including a magnetic element according to an embodiment. [Figure 7] FIG. 1 is a perspective view showing a digital still camera, which is an electronic device including a magnetic element according to an embodiment. [Figure 8] FIG. 1 is a perspective view showing an automobile, which is a mobile body equipped with a magnetic element according to an embodiment. [Figure 9] 1 is a graph comparing particle size distributions obtained in the Fe-based alloy soft magnetic powders of Examples 1 and 2 and Comparative Examples 1 and 2. [Figure 10] 1 is an observation image of the Fe-based alloy soft magnetic powder of Example 1 obtained by a scanning electron microscope. [Figure 11] 1 is an observation image of the Fe-based alloy soft magnetic powder of Comparative Example 2 obtained by a scanning electron microscope. DETAILED DESCRIPTION OF THE INVENTION

[0012] The insulator-coated soft magnetic powder, the method for producing the insulator-coated soft magnetic powder, the dust core, the magnetic element, the electronic device, and the mobile object of the present invention will be described in detail below with reference to the accompanying drawings.

[0013] 1.Insulator coated soft magnetic powder First, the insulator-coated soft magnetic powder according to the embodiment will be described. Fig. 1 is a cross-sectional view schematically showing one particle of the insulator-coated soft magnetic powder 1 according to the embodiment. In the following description, one particle of the insulator-coated soft magnetic powder 1 will also be referred to as an "insulator-coated soft magnetic particle 4."

[0014] The insulator-coated soft magnetic particles 4 shown in FIG. 1 have Fe-based alloy soft magnetic particles 2 and an insulating coating 3 provided on the surfaces of the Fe-based alloy soft magnetic particles 2. Of these, the Fe-based alloy soft magnetic particles 2 contain a soft magnetic material described below. The insulating coating 3 is provided so as to coat the surfaces of the Fe-based alloy soft magnetic particles 2 and has insulating properties. In this specification, the term "coated" refers to a state in which the entire surface of the Fe-based alloy soft magnetic particles 2 is covered, as well as a state in which part of the surface is covered. In the following description, the aggregate of the Fe-based alloy soft magnetic particles 2 will also be referred to as "Fe-based alloy soft magnetic powder."

[0015] When a plurality of such insulator-coated soft magnetic particles 4 are gathered together to form a powder magnetic core, the insulation between particles is improved. This reduces eddy current loss in a magnetic element including the powder magnetic core. As a result, the insulator-coated soft magnetic particles 4 contribute to the realization of a magnetic element with low loss (core loss) in the high frequency range.

[0016] 1.1.Fe-based alloy soft magnetic particles As described above, the Fe-based alloy soft magnetic particles 2 contain a soft magnetic material. The soft magnetic material is an Fe-based alloy material whose main component is Fe, i.e., an Fe-based alloy material containing 50% or more Fe in atomic ratio. The soft magnetic material may contain an element that exhibits ferromagnetism by itself, such as Ni or Co, as well as at least one element selected from the group consisting of Cr, Nb, Cu, Al, Mn, Mo, Si, Sn, B, C, P, Ti, and Zr, depending on the desired properties. The soft magnetic material may also contain unavoidable impurities as long as the effects of the embodiment are not impaired.

[0017] Inevitable impurities are impurities that are unintentionally mixed into raw materials or during manufacturing. Examples of inevitable impurities include O, N, S, Na, Mg, and K.

[0018] Specific examples of soft magnetic materials include Fe-Si alloys such as silicon steel, Fe-Si-Al alloys such as sendust, as well as various alloys such as Fe-Ni, Fe-Co, Fe-Ni-Co, Fe-Si-B, Fe-Si-BC, Fe-Si-B-Cr-C, Fe-Si-Cr, Fe-B, Fe-PC, Fe-Co-Si-B, Fe-Si-B-Nb, Fe-Si-B-Nb-Cu, Fe-Zr-B, Fe-Cr, and Fe-Cr-Al alloys.

[0019] By using a soft magnetic material with such a composition, it is possible to obtain insulator-coated soft magnetic particles 4 that have high magnetic permeability, high magnetic flux density, and low coercive force.

[0020] The Fe content in the soft magnetic material is preferably 70% or more, more preferably 80% or more, in terms of atomic ratio, which can particularly improve the magnetic properties of the insulator-coated soft magnetic particles 4, such as magnetic permeability and magnetic flux density.

[0021] The structure constituting the soft magnetic material is not particularly limited and may be any of a crystalline structure, an amorphous structure, or a microcrystalline (nanocrystalline) structure. Of these, it is preferable that the soft magnetic material contains an amorphous or microcrystalline structure. By including these, the coercive force is reduced, which contributes to reducing the hysteresis loss of the magnetic element. Note that the soft magnetic material may contain a mixture of structures with different crystallinity.

[0022] The composition of the soft magnetic material is determined by the following analytical method. Examples of analytical methods include iron and steel - atomic absorption spectrometry specified in JIS G 1257:2000, iron and steel - inductively coupled plasma (ICP) atomic emission spectrometry specified in JIS G 1258:2007, iron and steel - spark discharge atomic emission spectrometry specified in JIS G 1253:2002, iron and steel - X-ray fluorescence analysis specified in JIS G 1256:1997, and gravimetric / titration / absorptiometry specified in JIS G 1211 to G 1237.

[0023] Specific examples include a solid-state optical emission spectrometer manufactured by SPECTRO, in particular a spark discharge optical emission spectrometer, model: SPECTROLAB, type: LAVMB08A, and an ICP device, model CIROS120 manufactured by Rigaku Corporation.

[0024] In particular, when identifying carbon (C) and sulfur (S), the oxygen flow combustion (high-frequency induction heating furnace combustion)-infrared absorption method specified in JIS G 1211:2011 is also used. Specifically, the LECO CS-200 carbon / sulfur analyzer can be used.

[0025] In particular, when specifying N (nitrogen) and O (oxygen), the nitrogen determination method for iron and steel specified in JIS G 1228:1997 and the oxygen determination method for metallic materials specified in JIS Z 2613:2006 are also used. Specific examples include the LECO oxygen and nitrogen analyzer TC-300 / EF-300.

[0026] In the particle size distribution of the Fe-based alloy soft magnetic powder on a volume basis, when the particle diameter at which the cumulative frequency is 50% is defined as D50, D50 is set to 0.1 μm or more and 3.0 μm or less, preferably 0.3 μm or more and 1.5 μm or less, and more preferably 0.5 μm or more and 1.2 μm or less. When the D50 of the Fe-based alloy soft magnetic powder is within this range, the path of eddy currents within the particles of the Fe-based alloy soft magnetic particles 2 is shortened, thereby sufficiently reducing eddy current loss in the magnetic element in the high frequency range. Furthermore, when the D50 of the Fe-based alloy soft magnetic powder is within this range, the packing property during compaction is improved, thereby improving the magnetic properties of the magnetic element, such as the saturation magnetic flux density.

[0027] If the particle diameter D50 of the Fe-based alloy soft magnetic powder is below the lower limit, aggregation is likely to occur, making it difficult to form the insulating coating 3 and reducing the packing ability during compaction. This generates secondary particles and increases eddy current loss due to eddy currents between particles. On the other hand, if the particle diameter D50 of the Fe-based alloy soft magnetic powder is above the upper limit, the path of the eddy currents within the particles becomes longer, increasing eddy current loss due to eddy currents within the particles.

[0028] In the volumetric particle size distribution of Fe-based alloy soft magnetic powder, when the particle diameter at which the cumulative frequency is 90% is defined as D90, the ratio of D90 / D50 is 2.00 or less, preferably 1.75 or less, and more preferably 1.50 or less. When the D90 / D50 ratio is within the above range, the content of coarse particles is low, and the particle size distribution is sufficiently narrow. Therefore, such Fe-based alloy soft magnetic powder can suppress the generation of intraparticle eddy currents caused by coarse particles, thereby suppressing the increase in eddy current loss in magnetic elements in the high frequency range. Furthermore, the decrease in packing ability during compaction caused by coarse particles can be suppressed.

[0029] If the D90 / D50 ratio exceeds the upper limit, the content of coarse particles is high, and the eddy currents within the particles increase due to the coarse particles. Therefore, when a magnetic element is obtained using an Fe-based alloy soft magnetic powder with a D90 / D50 ratio exceeding the upper limit, the eddy current loss of the magnetic element increases in the high frequency range. Furthermore, the coarse particles reduce the packing ability of the insulator-coated soft magnetic powder 1, resulting in a decrease in the magnetic properties of the magnetic element, such as the saturation magnetic flux density.

[0030] Although the lower limit of the D90 / D50 ratio is not particularly set, it is preferable to set it to 1.2 or more, taking into consideration the balance between manufacturing costs and characteristics.

[0031] The particle size distribution on a volume basis of the Fe-based alloy soft magnetic powder can be obtained, for example, by a laser diffraction / dispersion method.

[0032] The cross-sectional shape of the Fe-based alloy soft magnetic particles 2 is not particularly limited and may be, for example, circular, elliptical, polygonal, etc., but is preferably circular.

[0033] Specifically, the Fe-based alloy soft magnetic powder preferably has a ratio of Fe-based alloy soft magnetic particles 2 with a circularity of 0.60 or less of 2.0% or less, and more preferably 1.5% or less. With such Fe-based alloy soft magnetic powder, the specific surface area can be made sufficiently small, and the area to be covered with the insulating coating 3 can also be made sufficiently small. This allows the volume ratio of the Fe-based alloy soft magnetic powder in the powder magnetic core to be increased, resulting in a magnetic element with excellent magnetic properties. Furthermore, the improved packing property reduces the likelihood of voids occurring in the powder magnetic core, making it possible to realize a magnetic element with excellent magnetic properties.

[0034] Furthermore, if the ratio of the Fe-based alloy soft magnetic particles 2 having a circularity of 0.60 or less exceeds the upper limit, the influence of shape magnetic anisotropy may reduce the uniformity of the density of the magnetic lines of force formed by the Fe-based alloy soft magnetic particles 2, which may result in a deterioration of the magnetic properties.

[0035] The circularity CI of the Fe-based alloy soft magnetic powder is defined by the following formula (1). CI=4πS / L 2 ···(1) In the above formula (1), S represents the projected area of ​​the soft magnetic particle 2 of an Fe-based alloy, and L represents the circumferential length of the soft magnetic particle 2 of an Fe-based alloy.

[0036] The circularity of the Fe-based alloy soft magnetic powder is measured by subjecting an image of the Fe-based alloy soft magnetic powder to the following image processing.

[0037] First, an image of a plurality of Fe-based alloy soft magnetic particles 2 taken with a scanning electron microscope (SEM), optical microscope, or the like is subjected to image processing to detect contours. This identifies the particle image. Next, the area and perimeter of the particle image are measured. Then, the circularity CI is calculated based on the above formula (1). Next, the circularity CI is determined for each of the plurality of Fe-based alloy soft magnetic particles 2. Then, the ratio of Fe-based alloy soft magnetic particles 2 having a circularity CI of 0.60 or less in one image is calculated.

[0038] Image processing for identifying particle images from an image can be performed using, for example, the image processing system ImageJ developed by the National Institutes of Health.

[0039] The coercive force of the Fe-based alloy soft magnetic powder is preferably 800 A / m (10.05 Oe) or less, and more preferably 400 A / m (5.03 Oe) or less. By using such an Fe-based alloy soft magnetic powder with low coercive force, a magnetic element can be obtained that can sufficiently suppress hysteresis loss even when used in a high frequency range.

[0040] The coercive force of the Fe-based alloy soft magnetic powder can be measured, for example, by a magnetization measuring device, TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd.

[0041] The saturation magnetization of the Fe-based alloy soft magnetic powder is preferably 1.1 T or more, and more preferably 1.2 T or more. By using such an Fe-based alloy soft magnetic powder with high saturation magnetization, a magnetic element with excellent magnetic properties such as saturation magnetic flux density can be obtained. The upper limit of the saturation magnetization of the Fe-based alloy soft magnetic powder is not particularly limited, but is preferably 2.2 T or less from the viewpoints of cost and freedom of material selection.

[0042] The saturation magnetization of the Fe-based alloy soft magnetic powder can be measured, for example, by a magnetization measuring device, TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd.

[0043] The Fe-based alloy soft magnetic powder may be powder produced by any method. Examples of the production method include, for example, various atomization methods such as water atomization method, gas atomization method, rotating water flow atomization method, etc., and in addition, reduction method, carbonyl method, pulverization method, etc. Among these, the atomization method is preferably used. That is, the Fe-based alloy soft magnetic powder is preferably atomized powder. Atomized powder is minute, has a high sphericity, and also has high production efficiency. In particular, water atomized powder or rotating water flow atomized powder is produced by the contact between molten metal and water, so it has a thin oxide film on the surface. Since this oxide film serves as the base of the insulating film 3, an insulating coated soft magnetic particle 4 having excellent adhesion between the Fe-based alloy soft magnetic particle 2 and the insulating film 3 and high insulation between particles can be obtained.

[0044] 1.2. Insulating film The insulating film 3 covers the surface of the Fe-based alloy soft magnetic particle 2.

[0045] The insulating film 3 contains silicon oxide or a composite oxide of silicon and at least one selected from the group consisting of Al, Ti, V, Nb, Cr, Mn, and Zr. The silicon oxide is SiO x (0 < x ≦ 2), and specifically, SiO2 is preferable. The silicon oxide is chemically stable and has high insulation. Therefore, the insulating film 3 containing silicon oxide can reduce the eddy current between particles even if the film thickness is thin. In addition, Al, Ti, V, Nb, Cr, Mn, and Zr form a composite oxide with silicon to realize an insulating film 3 having chemical stability and insulation equivalent to or higher than that of silicon oxide. Therefore, such an insulating film 3 contributes to the realization of an insulating coated soft magnetic particle 4 capable of reducing eddy current loss and having excellent magnetic properties.

[0046] Also, the insulating film 3 may include a plurality of layers composed of oxides of different types from each other.

[0047] Furthermore, the insulating coating 3 may contain unavoidable impurities within a range that does not impair the above-mentioned effects. Examples of the unavoidable impurities include C, N, P, and the like.

[0048] The average thickness of the insulating coating 3 is preferably 1 nm or more and 100 nm or less, and more preferably 3 nm or more and 50 nm or less. This allows the filling rate of the Fe-based alloy in the powder magnetic core to be increased to a certain level while ensuring sufficient insulation and heat resistance of the insulating coating 3. If the average thickness of the insulating coating 3 is below the lower limit, the insulating properties and heat resistance of the insulating coating 3 may be insufficient, depending on the material of the insulating coating 3. On the other hand, if the thickness of the insulating coating 3 is above the upper limit, the insulating coating 3 may be prone to peeling, or the filling rate of the Fe-based alloy in the powder magnetic core may be reduced, depending on the material of the insulating coating 3.

[0049] The average thickness of the insulating coating 3 is measured, for example, by magnifying and observing the cross section of the insulator-coated soft magnetic particle 4. Specifically, the insulator-coated soft magnetic particle 4 is cut with a focused ion beam to prepare a cross-sectional thin section sample. The obtained cross-sectional thin section sample is then observed with a scanning transmission electron microscope, and the thickness of the insulating coating 3 is measured at five or more locations per particle. The measured values ​​are then averaged, and the calculated result is defined as the average thickness of the insulating coating 3.

[0050] The structure of the insulating coating 3 can be confirmed by, for example, EDX analysis (energy dispersive X-ray analysis), Auger electron spectroscopy measurement, or the like.

[0051] As described above, the insulator-coated soft magnetic powder 1 according to this embodiment comprises an Fe-based alloy soft magnetic powder and an insulating coating 3 that coats the surfaces of the Fe-based alloy soft magnetic powder particles (Fe-based alloy soft magnetic particles 2). When D50 is the particle diameter at which the cumulative frequency is 50% in the volumetric particle size distribution of the Fe-based alloy soft magnetic powder, in this embodiment, D50 is 0.1 μm or more and 3.0 μm or less. When D90 is the particle diameter at which the cumulative frequency is 90% in the volumetric particle size distribution of the Fe-based alloy soft magnetic powder, in this embodiment, the ratio of D90 / D50 is 2.00 or less.

[0052] With this configuration, the path of the eddy current within the Fe-based alloy soft magnetic particles 2 can be shortened, and the particle size distribution of the Fe-based alloy soft magnetic powder can be sufficiently narrowed, resulting in an insulator-coated soft magnetic powder 1 that can be used to manufacture magnetic elements with sufficiently reduced eddy current loss in the high-frequency range.

[0053] 2. Manufacturing method of insulator-coated soft magnetic powder Next, a method for producing an insulator-coated soft magnetic powder according to an embodiment will be described. Fig. 2 is a process chart for explaining a method for producing an insulator-coated soft magnetic powder according to an embodiment.

[0054] The method for producing an insulator-coated soft magnetic powder shown in FIG. 2 includes an Fe-based alloy raw powder preparation step S102, a submerged classification step S104, and an insulating coating formation step S106.

[0055] 2.1.Fe-based alloy raw powder preparation process In the Fe-based alloy raw material powder preparation step S102, first, the Fe-based alloy raw material powder is prepared by the atomization method or the like described above.

[0056] Atomization methods are divided into water atomization, rotary water jet atomization, gas atomization, etc., depending on the type of coolant and the configuration of the equipment. Atomization is a method of producing metal powder by pulverizing and cooling molten metal by colliding it with a liquid or gas jetted at high speed.

[0057] Of these, in the water atomization method, molten metal is split in the air by a large negative pressure, forming fine droplets. These droplets are then rapidly cooled and solidified by a high-speed water jet, resulting in a nearly spherical metal powder. For this reason, the water atomization method is particularly suitable as a method for producing Fe-based alloy raw material powder. In addition, the fast cooling rate makes it possible to produce Fe-based alloy raw material powder containing amorphous and microcrystalline structures.

[0058] When commercially available Fe-based alloy raw material powder is procured, this step can be omitted.

[0059] 2.2. Submerged classification process In the submerged classification step S104, the Fe-based alloy raw material powder is classified in liquid. This extracts an Fe-based alloy soft magnetic powder having a D50 of 0.1 μm or more and 3.0 μm or less and a D90 / D50 ratio of 2.00 or less. Classification in liquid is also called wet classification. In contrast, classification in air is also called dry classification. While dry classification classifies particles in air by utilizing differences in mechanical behavior, wet classification in liquid classifies particles by utilizing centrifugal force, gravity, etc. in liquid. Therefore, wet classification in liquid can classify particles with higher accuracy even at submicron sizes, and can also suppress particle aggregation during classification more effectively than dry classification.

[0060] Specifically, the submerged classification step preferably includes a classification operation using centrifugal force or gravity. High classification accuracy can be achieved in either a centrifugal field or a gravitational field. From the viewpoint of more precise classification, it is more preferable to include a classification operation using gravity.

[0061] Gravity classification is a classification operation that utilizes the fact that the settling speed in a liquid varies depending on the particle size (particle diameter), and can be performed using, for example, an upright cylindrical wet classifier. Also, by determining the settling speed for each particle size (particle diameter) in advance and collecting particles from the classifier according to the settling time, metal powder with the desired particle diameter can be obtained.

[0062] Furthermore, when the Fe-based alloy raw material powder is classified in a liquid, the liquid preferably contains a dispersant. By adding a dispersant, aggregation of particles in the liquid can be suppressed. Examples of dispersants include carboxylate-based dispersants and sulfonate-based dispersants.

[0063] The amount of dispersant added is not particularly limited, but is preferably 0.1 to 5.0 parts by mass, more preferably 0.2 to 3.0 parts by mass, per 100 parts by mass of the Fe-based alloy raw material powder.

[0064] 2.3. Insulating film formation process In the insulating coating forming step S106, the insulating coating 3 is formed on the particle surface of the Fe-based alloy soft magnetic powder extracted in the submerged classification step S104, thereby obtaining an insulator-coated soft magnetic powder.

[0065] The method for forming the insulating coating 3 is not particularly limited, and examples thereof include wet formation methods such as the sol-gel method and electrolytic reduction method, and dry formation methods such as ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), and ion plating. Of these, the sol-gel method is preferably used, and the Stöber method, which is a type of sol-gel method, is particularly preferably used.

[0066] The Stober method is a technique for forming monodisperse particles by hydrolysis of metal alkoxide. For example, when forming the insulating coating 3 using silicon oxide, the hydrolysis reaction of silicon alkoxide using the Stober method can be used. The method using silicon alkoxide will be described below.

[0067] Specifically, first, the Fe-based alloy soft magnetic powder is dispersed in an alcohol solution containing silicon alkoxide. Examples of the alcohol solution include lower alcohols such as ethanol and methanol. Then, for example, 10 to 50 parts by mass of alcohol may be mixed with 1 part by mass of tetraethoxysilane. Furthermore, from the viewpoint of forming a uniform coating on the particle surface, 0.01 to 0.1 parts by mass of silicon alkoxide may be mixed with 1 part by mass of the Fe-based alloy soft magnetic powder. Note that, for example, TEOS (tetraethoxysilane, Si(OC2H5)4) is preferably used as the silicon alkoxide.

[0068] Next, ammonia water is added as a catalyst to promote the reaction, causing hydrolysis. This causes a dehydration condensation reaction between the hydrolyzates and between the hydrolyzates and silicon alkoxide, forming -Si-O-Si- bonds on the particle surface. This results in a silicon oxide film.

[0069] Before or after mixing with the ammonia water, the Fe-based alloy soft magnetic powder and the alcohol solution may be stirred using an ultrasonic wave application device or the like. Such stirring promotes uniform dispersion of the particles and allows a more uniform silicon oxide film to be formed on the particle surfaces. Stirring is preferably carried out for a time sufficient to allow the hydrolysis reaction of the silicon alkoxide to proceed sufficiently.

[0070] In the above description, the Fe-based alloy soft magnetic powder is dispersed in an alcohol solution containing silicon alkoxide, and then ammonia water is mixed in. However, the order of mixing the ammonia water is not limited to this. For example, the alcohol solution in which the Fe-based alloy soft magnetic powder is dispersed may be mixed with ammonia water, and then the alcohol solution containing silicon alkoxide may be mixed in. In such a case, the alcohol solution containing silicon alkoxide may be added in several portions. When adding in several portions, the above-mentioned stirring may be performed after each addition, or the alcohol solution may be added while stirring.

[0071] The thickness of the insulating coating 3 can be adjusted by the concentration of silicon alkoxide in the solution. For example, increasing the concentration of silicon alkoxide in the solution increases the thickness of the insulating coating 3, but increasing the concentration too much may result in excessive silicon oxide being precipitated alone. For this reason, it is preferable to adjust the concentration of silicon alkoxide in the solution within the above range.

[0072] After the insulating coating 3 is formed, the resulting insulating-material-coated soft magnetic powder may be subjected to a heat treatment, if necessary. The heat treatment conditions are, for example, a temperature of 60°C or higher and 120°C or lower, and a time of 10 minutes or higher and 300 minutes or lower. This can remove hydrates remaining in the insulating coating 3 and improve the adhesion of the insulating coating 3.

[0073] In the method for manufacturing magnetic beads according to this embodiment, a separate classification step may be performed between the Fe-based alloy raw material powder preparation step S102 and the submerged classification step S104. In this classification step, coarse particles contained in the Fe-based alloy raw material powder are removed in advance. This increases the classification accuracy in the submerged classification step.

[0074] In the above description, the insulating coating forming step S106 is performed after the submerged classification step S104, but this order may be reversed.

[0075] As described above, the method for producing an insulator-coated soft magnetic powder according to this embodiment includes a submerged classification step S104 and an insulating coating formation step S106. In the submerged classification step S104, the Fe-based alloy raw material powder is classified in liquid, and Fe-based alloy soft magnetic powder is extracted, where D50 is the particle diameter at which the cumulative frequency is 50% in the volumetric particle size distribution, and D50 is 0.1 μm or more and 3.0 μm or less, and D90 is the particle diameter at which the cumulative frequency is 90% in the volumetric particle size distribution, and the ratio of D90 / D50 is 2.00 or less. In the insulating coating formation step S106, an insulating coating 3 is formed on the Fe-based alloy soft magnetic powder, covering the surfaces of the particles (Fe-based alloy soft magnetic particles 2).

[0076] With this configuration, classification in liquid allows for highly accurate extraction of Fe-based alloy soft magnetic powder with optimized D50 and D90 / D50 ratios. The insulator-coated soft magnetic powder, which includes Fe-based alloy soft magnetic powder with a highly precisely controlled particle size distribution, has sufficiently short eddy current paths within the Fe-based alloy soft magnetic particles 2 and a sufficiently narrow particle size distribution. Therefore, this manufacturing method allows for the production of insulator-coated soft magnetic powder that can realize magnetic elements with sufficiently reduced eddy current loss in the high-frequency range.

[0077] 3. Powder cores and magnetic elements Next, the powder magnetic core and the magnetic element according to the embodiment will be described.

[0078] The magnetic element according to the embodiment can be applied to various magnetic elements having a magnetic core, such as a choke coil, an inductor, a noise filter, a reactor, a transformer, a motor, an actuator, a solenoid valve, a generator, etc. Furthermore, the powder magnetic core according to the embodiment can be applied to the magnetic cores provided in these magnetic elements.

[0079] Two types of coil components will be described below as representative examples of magnetic elements. 3.1.Toroidal type First, a toroidal type coil component will be described as an example of a magnetic element according to the embodiment. FIG. 3 is a plan view schematically showing a toroidal type coil component.

[0080] 3 has a ring-shaped powder magnetic core 11 and a conductive wire 12 wound around this powder magnetic core 11. Such a coil component 10 is generally called a toroidal coil.

[0081] The powder magnetic core 11 is obtained by mixing the insulator-coated soft magnetic powder according to the embodiment with a binder, feeding the resulting mixture into a molding die, and then applying pressure and molding. That is, the powder magnetic core 11 is a compact containing the insulator-coated soft magnetic powder according to the embodiment. Such a powder magnetic core 11 allows for good filling of the insulator-coated soft magnetic powder and realizes a magnetic element with low eddy current loss when used in the high frequency range. Therefore, a coil component 10 including the powder magnetic core 11 has low eddy current loss and high magnetic properties such as magnetic permeability and magnetic flux density. As a result, when the coil component 10 is installed in an electronic device, the power consumption of the electronic device can be reduced and the performance and size of the electronic device can be improved.

[0082] Examples of materials constituting the binder used to fabricate the powder magnetic core 11 include organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins, and inorganic materials such as phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates such as sodium silicate. Thermosetting polyimide or epoxy resins are particularly preferred. These resin materials cure easily when heated and have excellent heat resistance. This improves the ease of manufacturing and heat resistance of the powder magnetic core 11. The binder may be added as needed or may be omitted.

[0083] The ratio of binder to insulator-coated soft magnetic powder varies slightly depending on the desired magnetic and mechanical properties, allowable eddy current loss, etc. of the powder core 11 to be produced, but is preferably about 0.5% by mass to 5.0% by mass, and more preferably about 1.0% by mass to 3.0% by mass. This allows the particles of the insulator-coated soft magnetic powder to be sufficiently bound together, and allows the coil component 10 to have excellent magnetic properties. If necessary, various additives may be added to the mixture for any purpose.

[0084] The conductive wire 12 may be made of a highly conductive material, such as a metal material containing Cu, Al, Ag, Au, Ni, etc. If necessary, an insulating film may be provided on the surface of the conductive wire 12.

[0085] The shape of the powder magnetic core 11 is not limited to the ring shape shown in FIG. 3, but may be, for example, a shape in which a part of the ring is missing, a shape in which the longitudinal direction is linear, a sheet shape, a film shape, or the like.

[0086] Furthermore, the powder magnetic core 11 may contain soft magnetic powder other than the insulator-coated soft magnetic powder according to the embodiment described above, or non-magnetic powder, as needed.

[0087] For example, the powder magnetic core 11 may further contain large-diameter soft magnetic powder having a larger average particle size than the Fe-based alloy soft magnetic powder. This can further improve the packing ability of the powder magnetic core 11. In other words, the particles of the Fe-based alloy soft magnetic powder are arranged so as to fill the gaps between the particles of the large-diameter soft magnetic powder, which tends to improve the packing ability compared to when the powder magnetic core 11 is made solely of insulator-coated soft magnetic powder. On the other hand, by adjusting the amount of large-diameter soft magnetic powder added, it is possible to minimize the increase in eddy current loss in the coil component 10 (magnetic element). As a result, a coil component 10 can be obtained that achieves both improved magnetic properties and suppressed eddy current loss to a higher degree.

[0088] The large-diameter soft magnetic powder refers to a powder with a larger average particle size than the Fe-based alloy soft magnetic powder. Specifically, the particle size D50 of the large-diameter soft magnetic powder is preferably 3.0 μm to 30.0 μm, and more preferably 5.0 μm to 20.0 μm, larger than the particle size D50 of the Fe-based alloy soft magnetic powder. This minimizes the increase in eddy current loss in the magnetic element while improving packing properties.

[0089] The large-diameter soft magnetic powder may be made of the same or different material as the Fe-based alloy soft magnetic powder.

[0090] Furthermore, the structure of the large-diameter soft magnetic powder may be the same as or different from the structure of the Fe-based alloy soft magnetic powder, such as when the Fe-based alloy soft magnetic powder contains an amorphous structure and the large-diameter soft magnetic powder contains a crystalline structure or a microcrystalline structure.

[0091] The mixing ratio of the insulator-coated soft magnetic powder to the large-diameter soft magnetic powder is not particularly limited, but is preferably 0.5:9.5 or more and 9.5:0.5 or less by mass, more preferably 1.0:9.0 or more and 5.0:5.0 or less, and even more preferably 1.0:9.0 or more and 4.0:6.0 or less. This optimizes the quantitative balance between the insulator-coated soft magnetic powder and the large-diameter soft magnetic powder. As a result, a coil component 10 is obtained that achieves both improved magnetic properties and suppressed eddy current loss to a higher degree.

[0092] As described above, the coil component 10, which is a magnetic element, includes the dust core 11 containing the insulator-coated soft magnetic powder described above. This makes it possible to realize the coil component 10 with low eddy current loss and excellent magnetic properties.

[0093] 3.2.Closed magnetic circuit type Next, a closed magnetic circuit type coil component, which is an example of a magnetic element according to the embodiment, will be described. FIG. 4 is a see-through perspective view that schematically shows a closed magnetic circuit type coil component.

[0094] The closed magnetic circuit type coil component will be described below, but the following description will focus on the differences from the toroidal type coil component, and a description of similar points will be omitted.

[0095] As shown in Fig. 4, the coil component 20 according to this embodiment is formed by embedding a conductor wire 22 formed into a coil shape inside a powder magnetic core 21. That is, the coil component 20, which is a magnetic element, includes a powder magnetic core 21 containing the insulator-coated soft magnetic powder described above, and is formed by molding the conductor wire 22 within the powder magnetic core 21. This powder magnetic core 21 has a configuration similar to that of the powder magnetic core 11 described above. This makes it possible to realize a coil component 20 with low eddy current loss and excellent magnetic properties.

[0096] The coil component 20 having such a configuration can be easily obtained in a relatively small size. Furthermore, the coil component 20 has high magnetic properties and low eddy current loss. Therefore, when the coil component 20 is installed in an electronic device or the like, it is possible to reduce the power consumption of the electronic device or the like, and to achieve high performance and miniaturization.

[0097] Furthermore, because the conductive wire 22 is embedded inside the powder core 21, gaps are unlikely to occur between the conductive wire 22 and the powder core 21. This makes it possible to suppress vibrations caused by magnetostriction of the powder core 21, and also to suppress the generation of noise associated with this vibration.

[0098] The shape of the powder magnetic core 21 is not limited to the shape shown in FIG. 4, but may be a sheet, a film, or the like.

[0099] Furthermore, the powder magnetic core 21 may contain soft magnetic powder other than the insulator-coated soft magnetic powder according to the embodiment described above, or non-magnetic powder, as needed.

[0100] 4.Electronic equipment Next, an electronic device including the magnetic element according to the embodiment will be described with reference to FIGS.

[0101] Fig. 5 is a perspective view showing a mobile personal computer, which is an electronic device including a magnetic element according to the embodiment. The personal computer 1100 shown in Fig. 5 includes a main body 1104 including a keyboard 1102, and a display unit 1106 including a display unit 100. The display unit 1106 is rotatably supported on the main body 1104 via a hinge structure. Such a personal computer 1100 includes a magnetic element 1000, such as a choke coil or inductor for a switching power supply, or a motor.

[0102] Fig. 6 is a plan view showing a smartphone, which is an electronic device including the magnetic element according to the embodiment. The smartphone 1200 shown in Fig. 6 includes a plurality of operation buttons 1202, an earpiece 1204, and a mouthpiece 1206. A display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 includes a magnetic element 1000, such as an inductor, a noise filter, or a motor, built in.

[0103] 7 is a perspective view showing a digital still camera, which is an electronic device equipped with the magnetic element according to the embodiment. The digital still camera 1300 photoelectrically converts an optical image of a subject using an imaging element such as a CCD (Charge Coupled Device) to generate an imaging signal.

[0104] 7 includes a display unit 100 provided on the back of a case 1302. The display unit 100 functions as a viewfinder that displays an object as an electronic image. A light receiving unit 1304 including an optical lens, a CCD, etc. is provided on the front side of the case 1302, i.e., on the back side in the figure.

[0105] When the photographer checks the subject image displayed on the display unit 100 and presses the shutter button 1306, the image signal from the CCD at that time is transferred to and stored in memory 1308. This digital still camera 1300 also incorporates magnetic elements 1000 such as inductors and noise filters.

[0106] Examples of electronic devices according to the embodiments include the personal computer of FIG. 5, the smartphone of FIG. 6, and the digital still camera of FIG. 7, as well as mobile phones, tablet terminals, watches, inkjet ejection devices such as inkjet printers, laptop personal computers, televisions, video cameras, video tape recorders, car navigation devices, pagers, electronic organizers, electronic dictionaries, calculators, electronic game devices, word processors, workstations, videophones, security television monitors, electronic binoculars, POS terminals, medical devices such as electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasound diagnostic devices, and electronic endoscopes, fish finders, various measuring devices, instruments for vehicles, aircraft, and ships, mobile object control devices such as automobile control devices, aircraft control devices, railway vehicle control devices, and ship control devices, and flight simulators.

[0107] As described above, such electronic devices include the magnetic element according to the embodiment, which provides the effect of the magnetic element, namely, low eddy current loss in the high frequency range, thereby enabling the electronic devices to be made more compact and with higher performance.

[0108] 5. Mobile Next, a moving body including the magnetic element according to this embodiment will be described with reference to FIG. FIG. 8 is a perspective view showing an automobile, which is a moving body equipped with the magnetic element according to the embodiment.

[0109] The magnetic element 1000 is built into the automobile 1500. Specifically, the magnetic element 1000 is built into various automobile parts, such as a car navigation system, an antilock braking system (ABS), an engine control unit, a battery control unit for a hybrid automobile or an electric automobile, a vehicle attitude control system, an electronic control unit (ECU) for an automatic driving system, a drive motor, a generator, an air conditioning unit, and the like.

[0110] As described above, such a moving body includes the magnetic element according to the embodiment, which allows the magnetic element to enjoy the effect of low eddy current loss in the high frequency range, and allows for the improvement of performance and miniaturization of equipment mounted on the moving body.

[0111] Note that the moving body according to this embodiment may be, for example, a motorcycle, a bicycle, an airplane, a helicopter, a drone, a ship, a submarine, a train, a rocket, a spaceship, or the like, in addition to the automobile shown in FIG.

[0112] The insulator-coated soft magnetic powder, the method for manufacturing the insulator-coated soft magnetic powder, the dust core, the magnetic element, the electronic device, and the mobile body of the present invention have been described above based on preferred embodiments, but the present invention is not limited thereto.

[0113] For example, in the above embodiment, a powder compact such as a powder core has been described as an example of an application of the insulator-coated soft magnetic powder of the present invention, but the application is not limited to this and may be, for example, a magnetic device such as a magnetic fluid, a magnetic head, a magnetic shielding sheet, etc. Furthermore, the shapes of the powder core and the magnetic element are not limited to those shown in the drawings and may be any shape.

[0114] Furthermore, the method for producing an insulator-coated soft magnetic powder of the present invention may be one in which any step for any purpose is added to the above-described embodiment. [Example]

[0115] Next, specific examples of the present invention will be described. 6. Preparation of insulator-coated soft magnetic powder Example 1 First, a Fe-based alloy raw material powder having the composition and crystal structure shown in Table 1 was prepared by water atomization. Next, the obtained Fe-based alloy raw material powder was classified in liquid using gravity. The classification method is described in detail below.

[0116] In the gravity-based classification method, 30 g of Fe-based alloy raw powder with a particle size D50 of approximately 3 μm was placed in 400 mL of pure water and dispersed ultrasonically to create a raw powder dispersion. This raw powder dispersion was then slowly poured into 1600 mL of pure water to form a slurry, which was then allowed to stand for 330 minutes before classification. 600 mL of slurry was then collected from the liquid surface using a siphon. The collected slurry was then heated and dried at 85°C for 120 minutes to evaporate the water, yielding an Fe-based alloy soft magnetic powder.

[0117] Here, the volumetric particle size distribution of the classified Fe-based alloy soft magnetic powder was obtained using a laser diffraction / scattering particle size distribution analyzer. Then, based on the obtained particle size distribution, the particle diameter D50 and particle diameter D90 were determined. The ratio of D90 / D50 was also calculated. The calculation results are shown in Table 1.

[0118] Furthermore, the circularity CI of the classified Fe-based alloy soft magnetic powder was measured from images observed with a scanning electron microscope. The ratio of Fe-based alloy soft magnetic particles having a circularity CI of 0.60 or less was then calculated. The calculation results are shown in Table 1.

[0119] Furthermore, the coercive force and saturation magnetization of the classified Fe-based alloy soft magnetic powder were measured using a magnetization measuring device, VSM System TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd. The measurement results are shown in Table 1.

[0120] Next, an insulating coating of silicon oxide (SiO2) having an average thickness of 20 nm was formed on the particle surfaces of the classified Fe-based alloy soft magnetic powder by the following method, to obtain an insulator-coated soft magnetic powder.

[0121] To form the insulating coating, 100 g of the Fe-based alloy soft magnetic powder was first dispersed in 950 mL of ethanol and mixed to prepare a mixed solution. This mixture was then subjected to ultrasonic irradiation and stirred for 20 minutes. After stirring, a mixed solution of 30 mL of pure water and 180 mL of ammonia water was added and stirred for an additional 10 minutes. A mixed solution of 3.3 mL of tetraethoxysilane and 100 mL of ethanol was then added and stirred for 120 minutes, forming a silicon oxide film on the surface of the Fe-based alloy soft magnetic particles.

[0122] The Fe-based alloy soft magnetic particles with the silicon oxide film formed thereon were washed with ethanol and acetone, respectively. After washing, they were dried at 65°C for 30 minutes and then heated at 200°C for 90 minutes. This resulted in an insulator-coated soft magnetic powder.

[0123] Example 2 First, a Fe-based alloy raw material powder having the composition and crystal structure shown in Table 1 was prepared by water atomization. Next, the obtained Fe-based alloy raw material powder was classified in liquid using centrifugal force. The classification method is described in detail below.

[0124] In the classification method using centrifugal force in liquid, first, Fe-based alloy raw material powder with a particle size D50 of approximately 3 μm was placed in pure water and dispersed at a content of 7 mass% to prepare a raw material powder dispersion. Next, this raw material powder dispersion was classified using a wet rotary classifier. The resulting classified Fe-based alloy raw material powder was heated and dried at 85°C for 120 minutes to volatilize the water, yielding an Fe-based alloy soft magnetic powder. Next, an insulating coating was formed in the same manner as in Example 1, to obtain an insulator-coated soft magnetic powder.

[0125] 6.3. Examples 3 to 6 First, an Fe-based alloy raw material powder having the composition and crystal structure shown in Table 1 was prepared by the manufacturing method shown in Table 1. Next, the obtained Fe-based alloy raw material powder was classified by the method shown in Table 1 to obtain an Fe-based alloy soft magnetic powder.

[0126] 6.4. Comparative Example 1 First, a Fe-based alloy raw material powder having the composition and crystal structure shown in Table 1 was produced by water atomization. Next, the obtained Fe-based alloy raw material powder was classified in air. Specifically, the Fe-based alloy raw material powder with a particle size D50 of approximately 10 μm was classified using a cyclone classifier, and the classification point was adjusted.

[0127] Thereafter, an insulating coating was formed on the particle surfaces of the classified Fe-based alloy raw material powder in the same manner as in Example 1, to obtain an insulator-coated soft magnetic powder.

[0128] 6.5. Comparative Examples 2 to 6 First, an Fe-based alloy raw material powder having the composition and crystal structure shown in Table 1 was prepared by the manufacturing method shown in Table 1. Next, the obtained Fe-based alloy raw material powder was classified by the method shown in Table 1 to obtain an Fe-based alloy soft magnetic powder.

[0129] [Table 1]

[0130] As shown in Table 1, in each example, both the particle diameter D50 and the ratio of D90 / D50 were within the specified range. In each example and comparative example, the average thickness of the insulating coating was within the range of 20 to 50 nm.

[0131] Fig. 9 is a graph comparing the particle size distributions obtained for the Fe-based alloy soft magnetic powders of Examples 1 and 2 and Comparative Examples 1 and 2. As shown in Fig. 9, the Fe-based alloy soft magnetic powders of Examples 1 and 2 have a smaller peak position corresponding to the particle size D50 and a narrower spread of the peak corresponding to the ratio of D90 / D50 compared to the Fe-based alloy soft magnetic powders of Comparative Examples 1 and 2.

[0132] FIG. 10 is an observation image obtained by a scanning electron microscope of the Fe-based alloy soft magnetic powder of Example 1. FIG. 11 is an observation image obtained by a scanning electron microscope of the Fe-based alloy soft magnetic powder of Comparative Example 2. In FIG. 10, most of the particle images are perfectly round, and the particle diameters are relatively uniform. In contrast, in FIG. 11, coarse particles are observed as indicated by the arrows. Coarse particles generally have irregular shapes such as needles or scales. For this reason, the circularity CI of the Fe-based alloy soft magnetic powder tends to decrease when coarse particles are mixed in.

[0133] 7. Evaluation of insulator-coated soft magnetic powder 7.1.Saturation magnetic flux density The saturation magnetic flux density of the insulator-coated soft magnetic powders of each example and comparative example was measured using a magnetization measuring device, VSM System TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd. The measurement results are shown in Table 2.

[0134] 7.2. Magnetic loss (core loss) of powder magnetic cores For the insulator-coated soft magnetic powders of each Example and Comparative Example, the magnetic loss (core loss) was measured by the following method.

[0135] First, the insulator-coated soft magnetic powder was mixed with a toluene solution of epoxy resin, which served as a binder, and then dried to form a mass. The amount of epoxy resin added was 2 parts by mass per 100 parts by mass of the insulator-coated soft magnetic powder. The resulting mass was pulverized and then passed through a 400 μm sieve. The pulverized material that passed through the sieve was dried at 50°C for 1 hour.

[0136] Next, the dried product was press-molded at a molding pressure of 98 MPa into a ring shape with an outer diameter of φ28 mm, an inner diameter of φ14 mm, and a thickness of 5 mm.The resulting molded body was then heated at 150°C for 0.75 hours in an air atmosphere to form a toroidal core.

[0137] Next, the core loss Pcv of the obtained toroidal core was measured using an impedance analyzer. The measurement conditions were: the number of turns of the primary coil and the secondary coil were each 7 turns, the wire diameter of the winding was 0.8 mm, and the measurement frequencies were 1 MHz and 5 MHz. The measurement results are shown in Table 2.

[0138] 7.3.Mechanical strength of powder magnetic cores The radial crushing strength of the toroidal cores (dust cores) obtained from the insulator-coated soft magnetic powders of each Example and Comparative Example was measured using the radial crushing strength test method specified in JIS Z 2507:2000. The measurement results are shown in Table 2. Note that measurement was omitted for some toroidal cores.

[0139] [Table 2]

[0140] As shown in Table 2, the insulator-coated soft magnetic powders of each Example had lower core loss in the high frequency range than the insulator-coated soft magnetic powders of each Comparative Example. Given that there was no difference in coercivity, it is presumed that this difference in core loss is due to a difference in eddy current loss. Therefore, it was confirmed that the insulator-coated soft magnetic powder according to the present invention can realize a magnetic element in which eddy current loss in the high frequency range is sufficiently suppressed.

[0141] 8. Mixing insulator-coated soft magnetic powder (small diameter powder) and large diameter soft magnetic powder (large diameter powder) Example 7 First, the insulator-coated soft magnetic powder of Example 1 was designated as the "small diameter side powder," and a separately prepared large diameter insulator-coated soft magnetic powder was designated as the "large diameter side powder," and these were mixed to obtain a mixed powder. The large diameter insulator-coated soft magnetic powder was a powder comprising large diameter soft magnetic powder with a particle diameter D50 of 30 μm and an insulating coating coating the particle surface. The method of forming the insulating coating, its thickness, etc. were the same as those of the insulator-coated soft magnetic powder of Example 1. The mixing ratio of the small diameter side powder to the large diameter side powder was 2:8 by mass.

[0142] 8.2. Examples 8 and 9 A mixed powder was obtained in the same manner as in Example 7, except that the smaller diameter powder, the larger diameter powder, and the mixing ratio were changed as shown in Table 3.

[0143] 8.3. Comparative Examples 7 to 9 A mixed powder was obtained in the same manner as in Example 7, except that the smaller diameter powder, the larger diameter powder, and the mixing ratio were changed as shown in Table 3.

[0144] [Table 3]

[0145] 9. Evaluation of mixed powders 9.1. Saturation magnetic flux density The saturation magnetic flux density of the mixed powders of each example and comparative example was measured using a magnetization measuring device, VSM System TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd. The measurement results are shown in Table 4.

[0146] 9.2. Magnetic loss (core loss) of powder magnetic cores The magnetic loss (core loss) of the mixed powders of each example and each comparative example was measured in the same manner as in 7.2 above. The measurement results are shown in Table 4.

[0147] [Table 4]

[0148] As shown in Table 4, the mixed powders of the examples had lower core loss in the high frequency range than the mixed powders of the comparative examples. Therefore, it was confirmed that the insulator-coated soft magnetic powder according to the present invention, even when used as a mixed powder, can realize a magnetic element in which eddy current loss in the high frequency range is sufficiently suppressed. [Explanation of symbols]

[0149] 1...insulating material coated soft magnetic powder, 2...Fe-based alloy soft magnetic particle, 3...insulating coating, 4...insulating material coated soft magnetic particle, 10...coil component, 11...powder magnetic core, 12...conductor, 20...coil component, 21...powder magnetic core, 22...conductor, 100...display unit, 1000...magnetic element, 1100...personal computer, 1102...keyboard, 1104...main body, 1106...display unit, 1200...smartphone, 1202...operation button, 1204...earpiece, 1206...mouthpiece, 1300...digital still camera, 1302...case, 1304...light receiving unit, 1306...shutter button, 1308...memory, 1500...automobile, S102...Fe-based alloy raw powder production process, S104...liquid classification process, S106...insulating coating formation process

Claims

1. An atomized Fe-based alloy soft magnetic powder, and particles of the Fe-based alloy soft magnetic powder. an insulating coating covering the terminal surface; The cumulative frequency in the particle size distribution on a volume basis of the Fe-based alloy soft magnetic powder is 50%. When the particle diameter is D50, D50 is 0.1 μm or more and 1.5 μm or less, The cumulative frequency in the particle size distribution on a volume basis of the Fe-based alloy soft magnetic powder is 90%. When the particle diameter is D90, the ratio of D90 / D50 is 2.00 or less. Insulator-coated soft magnetic powder.

2. The Fe-based alloy soft magnetic powder has a coercive force of 800 A / m or less and a saturation magnetization of 1 2. The insulator-coated soft magnetic powder according to claim 1, having a magnetic hardness of 0.1 T or more.

3. The insulating coating is made of silicon oxide or silicon and Al, Ti, V, Nb, Cr, and at least one selected from the group consisting of Mn and Zr. Item 3. The insulator-coated soft magnetic powder according to Item 1 or 2.

4. 4. The method according to claim 1, wherein the average thickness of the insulating coating is 1 nm or more and 100 nm or less.

1. The insulator-coated soft magnetic powder according to claim 1.

5. The Fe-based alloy soft magnetic powder has a ratio of particles having a circularity of 0.60 or less of 2.0% or less.

5. The insulator-coated soft magnetic powder according to claim 1, wherein

6. The Fe-based alloy raw material powder was classified in a liquid, and the cumulative frequency of the particle size distribution on a volume basis was 50. %, the particle diameter is defined as D50, and D50 is 0.1 μm or more and 1.5 μm or less, When the particle size at which the cumulative frequency is 90% in the particle size distribution on a volume basis is defined as D90, a liquid classification process for extracting an Fe-based alloy soft magnetic powder having a D90 / D50 ratio of 2.00 or less; The degree, An insulating coating type in which an insulating coating is formed on the surface of the Fe-based alloy soft magnetic powder. a synthesis process; 1. A method for producing an insulator-coated soft magnetic powder, comprising:

7. The method according to claim 6, wherein the submerged classification step includes a classification operation using centrifugal force or gravity. Method for manufacturing soft magnetic powder coated with an insulator.

8. 8. The method according to claim 7, wherein the liquid used for classifying the Fe-based alloy raw material powder contains a dispersant.

8. A method for producing an insulator-coated soft magnetic powder according to claim 7.

9. A magnetic material comprising the insulator-coated soft magnetic powder according to any one of claims 1 to 5. Powder magnetic core.

10. The magnetic material according to claim 1, further comprising a large-diameter soft magnetic powder having an average particle size larger than that of the Fe-based alloy soft magnetic powder.

10. The powder magnetic core according to claim 9.

11. A magnetic element comprising the powder magnetic core according to claim 9 or 10.

12. An electronic device comprising the magnetic element according to claim 11.

13. A moving body comprising the magnetic element according to claim 11.

Images