Method for producing insulating coated soft magnetic powder, insulating coated soft magnetic powder, compacted magnetic core, magnetic element, electronic equipment and mobile body

Abstract

To provide insulator-coated soft magnetic powder capable of producing a magnetic element having an insulation film derived from ceramic powder, satisfactory in insulation properties and high in magnetic properties, and a dust core, a magnetic element, an electronic apparatus and a movable body each comprising the insulator-coated soft magnetic powder.SOLUTION: An insulator-coated soft magnetic powder production method has: a mixing step in which soft magnetic powder and ceramic powder are mixed to obtain a mixture; a first pressure bonding step in which mechanical energy is applied to the mixture to pulverize the ceramic powder; and a second pressure bonding step in which, after the first pressure bonding step, mechanical energy bigger than that in the first pressure bonding step is applied to the mixture to fuse the pulverized ceramic powder to the grain surfaces of the soft magnetic powder and to obtain insulator-coated soft magnetic powder.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for producing insulating coated soft magnetic powder, insulating coated soft magnetic powder, compacted magnetic core, magnetic element, electronic device, and mobile body. [Background technology]

[0002] Patent Document 1 discloses silica-coated metal nitride particles formed by forming a silica film on the surface of metal nitride particles. These silica-coated metal nitride particles comprise metal nitride particles and silica particles whose volume-average particle size is smaller than that of the metal nitride particles and is between 5 nm and 200 nm. The silica particles are sintered onto the surface of the metal nitride particles, providing a seamless coating. Through this sintering operation, the silica particles are bonded to the surface of the metal nitride particles. Furthermore, this sintering operation is carried out under conditions in which the silica particles and metal nitride particles do not melt, that is, under conditions in which the original particle shape can be largely maintained.

[0003] Thus, by using a technique to coat particles containing metal elements with insulating particles such as silica particles, it is possible to manufacture, for example, an insulating coated soft magnetic powder that insulates the spaces between particles of soft magnetic powder. Since silica particles have good insulating properties on their own, the insulating coated soft magnetic powder can suppress eddy currents that travel through the spaces between particles. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2015-101510 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the silica-coated metal nitride particles described in Patent Document 1, the silica particles retain their original particle shape. As a result, the strength of the silica coating is insufficient, making it prone to peeling and cracking. Consequently, when the manufacturing technology for silica-coated metal nitride particles is applied to insulating soft magnetic powder, there is a problem in that sufficient insulation between particles cannot be ensured if peeling or cracking occurs in the silica coating. Furthermore, such silica coatings have a large specific surface area. Therefore, insulating soft magnetic powders with such silica coatings require a large amount of binder during the manufacturing of compacted magnetic cores. This can lead to a decrease in the magnetic properties of the magnetic element. [Means for solving the problem]

[0006] The method for producing insulating coated soft magnetic powder according to an application example of the present invention is as follows: A mixing step of mixing soft magnetic powder and ceramic powder to obtain a mixture, A first compression step involves crushing the ceramic powder by applying mechanical energy to the mixture, A second crimping step is performed after the first crimping step, in which a greater mechanical energy than that used in the first crimping step is applied to the mixture to fuse the pulverized ceramic powder to the particle surface of the soft magnetic powder, thereby obtaining an insulating coated soft magnetic powder. to have death, The ceramic powder includes secondary particles formed by the aggregation of multiple primary particles. It is characterized by the following:

[0007] The insulating coated soft magnetic powder according to an application example of the present invention is Soft magnetic powder and The particle surface of the soft magnetic powder is coated with an insulating film containing a ceramic material, It has, Let d be the average particle size of the soft magnetic powder, ρ be the true specific gravity of the soft magnetic powder, let s = 6 / (ρ·d) be the theoretical specific surface area s, and let S be the measured specific surface area. The measured specific surface area S is characterized in that it is 1.5 times or more and 4.0 times or less the theoretical specific surface area s.

[0008] The compacted powder core according to the application example of the present invention is characterized by including an insulating-coated soft magnetic powder according to the application example of the present invention.

[0009] The magnetic element according to the application example of the present invention is characterized by including a compacted powder core according to the application example of the present invention.

[0010] The electronic device according to the application example of the present invention is characterized by including a magnetic element according to the application example of the present invention.

[0011] The moving body according to the application example of the present invention is characterized by including a magnetic element according to the application example of the present invention.

Brief Description of the Drawings

[0012] [Figure 1] It is a cross-sectional view schematically showing one particle of the insulating-coated soft magnetic powder according to the embodiment. [Figure 2] It is a process diagram for explaining a method of manufacturing the insulating-coated soft magnetic powder according to the embodiment. [Figure 3] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 4] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 5] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 6] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 7] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 8] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 9] It is a schematic diagram for explaining the method of manufacturing the insulating-coated soft magnetic powder shown in FIG. 2. [Figure 10]Figure 2 is a schematic diagram illustrating the method for manufacturing the insulating soft magnetic powder shown. [Figure 11] This is a schematic plan view showing a toroidal coil component. [Figure 12] This is a schematic, transmissive perspective view showing a closed-magnetic-circuit type coil component. [Figure 13] This is a perspective view showing a mobile personal computer, which is an electronic device equipped with a magnetic element according to the embodiment. [Figure 14] This is a plan view showing a smartphone, which is an electronic device equipped with a magnetic element according to the embodiment. [Figure 15] This is a perspective view showing a digital still camera, which is an electronic device equipped with a magnetic element according to an embodiment. [Figure 16] This is a perspective view showing an automobile, which is a mobile body equipped with a magnetic element according to the embodiment. [Modes for carrying out the invention]

[0013] The method for producing the insulating coated soft magnetic powder of the present invention, the insulating coated soft magnetic powder, the compacted magnetic core, the magnetic element, the electronic device, and the mobile body will be described in detail below based on the attached drawings.

[0014] 1.Insulator coated soft magnetic powder First, the insulating soft magnetic powder according to the embodiment will be described. Figure 1 is a schematic cross-sectional view showing one particle of the insulating soft magnetic powder 1 according to the embodiment. In the following description, one particle of the insulating soft magnetic powder 1 will also be referred to as "insulating soft magnetic particle 4".

[0015] The insulating coated soft magnetic particles 4 shown in Figure 1 comprises soft magnetic particles 2 and an insulating coating 3 provided on the surface of the soft magnetic particles 2. Of these, the soft magnetic particles 2 are composed of a soft magnetic material described later. The insulating coating 3 is provided to cover the surface of the soft magnetic particles 2 and has insulating properties. In this specification, "coating" is a concept that includes not only covering the entire surface of the soft magnetic particles 2 but also covering a part of the surface. Furthermore, in the following description, the aggregate of soft magnetic particles 2 is also referred to as "soft magnetic powder".

[0016] As described later, the compacted magnetic core, which is made by compacting the insulating soft magnetic powder 1, has high inter-particle insulation. As a result, eddy current losses can be reduced in magnetic elements equipped with a compacted magnetic core.

[0017] 1.1. Soft magnetic particles Examples of soft magnetic materials constituting the soft magnetic particles 2 include materials mainly composed of at least one of Fe, Ni, and Co, that is, materials containing 50% or more of these elements in atomic ratio. In addition to these main component elements, the soft magnetic material may also contain 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. Furthermore, the soft magnetic material may contain unavoidable impurities to the extent that they do not impair the effects of this embodiment. Unavoidable impurities are impurities that are unintentionally mixed in during the raw material or manufacturing process. Unavoidable impurities include all elements other than those mentioned above, but examples include O, N, S, Na, Mg, K, etc.

[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 other 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, Fe-Cr-Al, Ni-Si alloys such as Ni-Si-B and Ni-PB, and Co-Si alloys such as Co-Si-B.

[0019] By using a soft magnetic material with such a composition, insulating coated soft magnetic particles 4 can be obtained that have high permeability and magnetic flux density, as well as low coercivity.

[0020] In soft magnetic materials, the content of the aforementioned main components is preferably 50% or more in terms of atomic number ratio, and more preferably 70% or more. This makes it possible to particularly enhance the magnetic properties such as permeability and magnetic flux density of the insulating soft magnetic particles 4.

[0021] The microstructure constituting the soft magnetic material is not particularly limited and may be crystalline, amorphous, or microcrystalline (nanocrystalline). Of these, it is preferable that the soft magnetic material contains amorphous or microcrystalline material. Including these reduces the coercivity and contributes to reducing the hysteresis loss of the magnetic element. In addition, the soft magnetic material may contain a mixture of microstructures with different crystalline properties.

[0022] Examples of amorphous and microcrystalline materials include Fe-based alloys such as 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, and Fe-Zr-B; Ni-based alloys such as Ni-Si-B and Ni-PB; and Co-based alloys such as Co-Si-B.

[0023] The composition of soft magnetic materials is determined by the following analytical methods. Examples of analytical methods include atomic absorption spectrometry for iron and steel as specified in JIS G 1257:2000, ICP emission spectrometry for iron and steel as specified in JIS G 1258:2007, spark discharge emission spectrometry for iron and steel as specified in JIS G 1253:2002, X-ray fluorescence spectrometry for iron and steel as specified in JIS G 1256:1997, and gravimetric titration-absorbance spectrophotometric methods as specified in JIS G 1211 to G 1237.

[0024] Specifically, examples include solid-state emission spectrometers manufactured by SPECTRO, particularly spark discharge emission spectrometers, model: SPECTROLAB, type: LAVMB08A, and the ICP instrument CIROS120 manufactured by Rigaku Corporation.

[0025] Furthermore, in particular, when identifying C (carbon) and S (sulfur), 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 is an example.

[0026] Furthermore, when specifically identifying nitrogen (N) and oxygen (O), the methods for determining nitrogen in iron and steel specified in JIS G 1228:1997 and the general rules for determining oxygen in metallic materials specified in JIS Z 2613:2006 are also used. Specifically, the LECO TC-300 / EF-300 oxygen and nitrogen analyzer is an example.

[0027] Furthermore, soft magnetic materials with a Vickers hardness of 200 to 500 are preferably used. This allows for an optimized balance of hardness with the ceramic material described later. As a result, when manufacturing the insulating coated soft magnetic powder 1 using a mechanochemical apparatus, for example, it becomes possible to form a thinner insulating coating 3 with a more uniform thickness.

[0028] Here, the average particle size of the soft magnetic powder is d [μm], and the true specific gravity of the soft magnetic powder is ρ [g / cm³].3 Let ] be the theoretical specific surface area s[m 2 The specific surface area S[m²] of the measured insulating coated soft magnetic powder 1 is defined as [ / g]. 2 Let [ / g]. In this case, the measured specific surface area S is between 1.5 and 4.0 times the theoretical specific surface area s.

[0029] In this type of insulating coated soft magnetic powder 1, the measured specific surface area S is suppressed from being significantly larger than the theoretical specific surface area s calculated from the average particle size d and true specific gravity ρ of the soft magnetic powder. In other words, the insulating coated soft magnetic powder 1 has a measured specific surface area S that is relatively close to the theoretical specific surface area s that would occur if the soft magnetic powder particles were assumed to be perfectly spherical. Therefore, since the insulating coated soft magnetic powder 1 requires less area to be covered by the insulating coating 3, the amount of binder used to bind the insulating coated soft magnetic particles 4 together when manufacturing a compacted magnetic core can be reduced. This makes it possible to realize a magnetic element with excellent magnetic properties such as permeability and saturation magnetic flux density. Furthermore, because the shape of the insulating coated soft magnetic powder 1 is close to that of a perfect sphere, the packing efficiency during compaction is high. From this perspective as well, it is possible to realize a magnetic element with excellent magnetic properties.

[0030] The average particle size d of the soft magnetic powder is preferably 1 μm to 50 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm. This shortens the path of the eddy currents within the insulating soft magnetic particles 4, thereby enabling the realization of a magnetic element with low eddy current loss in the high-frequency range. Furthermore, when the average particle size d of the soft magnetic powder is within the above range, the packing efficiency during compaction is improved, thereby enhancing the magnetic properties of the magnetic element.

[0031] The average particle size d is determined for soft magnetic powder by measuring the particle size distribution on a volume basis, for example, using laser diffraction, and obtaining the resulting layered distribution curve. Specifically, in the integrated distribution curve, the particle size at which the cumulative value from the smallest diameter side reaches 50% is defined as the average particle size d. An example of a measuring device is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0032] Furthermore, if the average particle size d of the soft magnetic powder falls below the lower limit, aggregation is more likely to occur, which may reduce the packing efficiency during compaction and potentially degrade the magnetic properties of the magnetic element. On the other hand, if the average particle size d of the soft magnetic powder exceeds the upper limit, the path of eddy currents within the particles becomes longer, which may increase eddy current losses originating from eddy currents within the particles. This may also reduce the packing efficiency during compaction and potentially degrade the magnetic properties of the magnetic element.

[0033] The measured specific surface area S is preferably 2.0 times or more and 3.8 times or less the theoretical specific surface area s, and more preferably 2.5 times or more and 3.6 times or less the theoretical specific surface area s.

[0034] The measured specific surface area S is obtained by the so-called BET method. For example, the BET-type specific surface area measuring device HM1201-010 manufactured by Mountec Co., Ltd. is used, with a sample volume of 5g.

[0035] The measured specific surface area S of the insulating soft magnetic powder 1 is 0.15 m². 2 / g or more 0.29m 2 It is preferable that the density is less than or equal to / g. Furthermore, the true specific gravity ρ of the soft magnetic powder is 7.3 g / cm³. 3 More than 8.3g / cm 3 The following is preferable:

[0036] 1.2. Insulating Coating The insulating film 3 covers the surface of the soft magnetic particles 2. The insulating film 3 contains a ceramic material. The volume ratio of the ceramic material in the insulating film 3 is preferably 60% or more, and more preferably 80% or more. Since the ceramic material has particularly high insulating properties compared to, for example, glass material or resin material, it contributes to improving the insulating properties between the insulating soft magnetic particles 4.

[0037] The insulating coating 3 is preferably a coating formed by solidifying a ceramic material on the surface of the soft magnetic particles 2 after it has melted, i.e., a coating in which the ceramic material has fused. In this case, the insulating coating 3 is formed to follow the irregularities present on the surface of the soft magnetic particles 2 and has good adhesion. Therefore, when the insulating coated soft magnetic powder 1 is compacted, the occurrence of peeling or cracking of the insulating coating 3 can be suppressed. As a result, a magnetic element can be realized in which eddy current loss originating from interparticle eddy currents is suppressed.

[0038] Whether or not the ceramic material is melted can be determined by observing a cross-section of the insulating film 3 under magnification using an electron microscope or the like, and checking whether or not it has a homogeneous structure, specifically whether or not there are many traces of the ceramic particles used to form the insulating film 3. If there are almost no traces of ceramic particles, it is considered to have a homogeneous structure. In addition, EDX (Energy Dispersive X-ray Spectroscopy) analysis may be used as needed.

[0039] Examples of ceramic materials include oxide-based ceramics such as aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, iron oxide, potassium oxide, sodium oxide, calcium oxide, chromium oxide, and niobium oxide; nitride-based ceramics such as boron nitride and silicon nitride; and silicon carbide. One or more of these materials are used in mixtures of two or more.

[0040] Of these, aluminum oxide, titanium oxide, zirconium oxide, or silicon oxide are preferably used as the ceramic material, with aluminum oxide being more preferably used. Because these have particularly high insulating and weather-resistant properties, they can particularly enhance the insulating properties between the insulating material-coated soft magnetic particles 4 and more effectively suppress deterioration of the soft magnetic particles 2 due to oxidation, corrosion, etc.

[0041] Furthermore, the ceramic material is preferably one with a Vickers hardness of 1000 to 3300, and more preferably one with a Vickers hardness of 1500 to 3000. By using such a ceramic material, an insulating coating 3 that is difficult to break even when compacted can be obtained. Therefore, compaction molding at high pressure becomes possible, and a magnetic element with excellent magnetic properties can be realized.

[0042] The average thickness of the insulating film 3 is preferably 5 nm to 300 nm, more preferably 10 nm to 250 nm, and even more preferably 20 nm to 200 nm. This further improves the insulating properties of the insulating film 3 and the packing properties of the soft magnetic particles 2 during compaction. If the average thickness of the insulating film 3 falls below the lower limit, the insulating properties and heat resistance of the insulating film 3 may become insufficient. On the other hand, if the thickness of the insulating film 3 exceeds the upper limit, the insulating film 3 may become more prone to peeling, or the packing properties of the soft magnetic particles 2 during compaction may decrease.

[0043] The average thickness of the insulating film 3 is the average of the thickness of the insulating film 3 measured at 10 or more locations by magnifying and observing the cross-section of the insulating film 3. For magnified observation, for example, a scanning transmission electron microscope is used.

[0044] Furthermore, the insulating coating 3 may contain insulating materials other than ceramic materials as needed. Examples of such materials include Bi2O3, B2O3, ZnO, SnO, P2O5, PbO, Li2O, Na2O, K2O, SrO, BaO, Gd2O3, Y2O3, La2O3, Yb2O3, etc., and one or more of these may be used.

[0045] 1.3. Characteristics of Insulation-Coated Soft Magnetic Powder The withstand voltage and insulation resistance value of the test piece obtained using the insulation-coated soft magnetic powder 1 are measured as follows.

[0046] First, the insulation-coated soft magnetic powder 1, an epoxy resin as a binder, and toluene as a solvent are mixed to obtain a mixture. The addition amount of the epoxy resin is 2% by mass of the addition amount of the insulation-coated soft magnetic powder 1. Next, after stirring the obtained mixture, it is dried to obtain a块状 dried body. Next, this dried body is crushed through a sieve with a mesh size of 400 μm to obtain granulated powder. The obtained granulated powder is dried at 50 °C for 1 hour. Next, the dried granulated powder is pressed at 294 MPa (3 t / cm 2 ) to obtain a test piece.

[0047] Next, after placing the obtained test piece in an alumina cylinder with an inner diameter of 8 mm, copper electrodes are arranged at both ends of the cylinder. Then, using a digital force gauge, while applying a pressure of 40 kgf / cm between the electrodes at both ends of the cylinder 2 , a voltage of 50 V is applied between the electrodes for 2 seconds at 25 °C. At this time, the electrical resistance value between the electrodes is measured with a digital multimeter to confirm the occurrence of dielectric breakdown.

[0048] Next, the voltage applied between the electrodes is increased to 100 V and held for 2 seconds. Then, the electrical resistance value between the electrodes at this time is measured to confirm the occurrence of dielectric breakdown.

[0049] Next, while increasing the voltage applied between the electrodes by 50 V each time from 150 V, the electrical resistance value between the electrodes is measured each time to confirm the presence or absence of dielectric breakdown. Then, until dielectric breakdown occurs, the voltage increase by 50 V each time and the measurement of the electrical resistance value are repeated, and the maximum voltage at which dielectric breakdown did not occur is taken as the withstand voltage of the test piece. If dielectric breakdown does not occur even when the voltage is increased to 1000 V, the measurement is terminated at 1000 V.

[0050] The dielectric strength of the test specimen measured by the above method is preferably 500V or higher, and more preferably 700V or higher. Furthermore, the insulation resistance of the test specimen when 100V is applied is preferably 1000MΩ or higher, and more preferably 10000MΩ or higher. By using an insulating coated soft magnetic powder 1 that satisfies these characteristics, a magnetic element can be realized in which eddy current losses originating from interparticle eddy currents are suppressed.

[0051] Furthermore, the magnetic permeability of the test specimen obtained using the insulating soft magnetic powder 1 is measured as follows.

[0052] First, the insulating soft magnetic powder 1, the epoxy resin binder, and the toluene solvent are mixed to obtain a mixture. The amount of epoxy resin added is 2% by mass of the amount of insulating soft magnetic powder 1 added. Next, the obtained mixture is stirred and dried to obtain a lump of dried material. Next, this dried material is pulverized by passing it through a sieve with a mesh size of 400 μm to obtain granulated powder. The obtained granulated powder is dried at 50°C for 1 hour. Next, the dried granulated powder is filled into a mold and molded according to the molding conditions below to obtain a test specimen.

[0053] • Forming method: Press forming • Shape of the molded body: ring-shaped • Dimensions of the molded body: Outer diameter 14mm, inner diameter 8mm, thickness 3mm ·Molding pressure: 3t / cm 2 (294 MPa)

[0054] Next, the effective permeability of the obtained test specimen is measured from the self-inductance of the closed-circuit magnetic core coil, and this is taken as the permeability of the test specimen. For measuring the permeability, an impedance analyzer such as the Agilent Technologies 4194A is used, and the measurement frequency is 1 MHz. The excitation coil has 7 turns, and the wire diameter of the winding is 0.6 mm.

[0055] The magnetic permeability of the test specimen measured by the above method is preferably 31 or higher when an Fe-Si-Cr-based soft magnetic material is used as the constituent material of the soft magnetic powder. This makes it possible to realize a magnetic element with high magnetic properties.

[0056] 1.4. Effects of the insulating coated soft magnetic powder according to the embodiment As described above, the insulating coated soft magnetic powder 1 according to this embodiment comprises soft magnetic powder and an insulating coating 3 containing a ceramic material that coats the particle surface of the soft magnetic powder. The average particle size of the soft magnetic powder is denoted as d, the true specific gravity of the soft magnetic powder as ρ, the specific surface area calculated as s = 6 / (ρ·d) is defined as the theoretical specific surface area s, and the measured specific surface area is defined as the measured specific surface area S. In this case, the measured specific surface area S is between 1.5 and 4.0 times the theoretical specific surface area s.

[0057] With this configuration, an insulating coated soft magnetic powder 1 is obtained in which the measured specific surface area S is controlled so as not to be significantly larger than the theoretical specific surface area s. In such an insulating coated soft magnetic powder 1, the insulating film 3 is formed with a thin and uniform thickness. Therefore, each insulating coated soft magnetic particle 4 has good insulating properties derived from the ceramic material. Furthermore, because such an insulating coated soft magnetic powder 1 has a small measured specific surface area S, the amount of binder used to bind the insulating coated soft magnetic particles 4 together can be reduced when it is used in the manufacture of compacted magnetic cores. This makes it possible to realize a magnetic element with high magnetic properties such as permeability and saturation magnetic flux density. Moreover, because the shape of the insulating coated soft magnetic powder 1 described above is close to a perfect sphere, the packing efficiency during compaction is high. From this viewpoint as well, a magnetic element with high magnetic properties can be realized.

[0058] Furthermore, it is mixed with 2% by mass of epoxy resin per 1 part insulating coated soft magnetic powder, and 294 MPa (3 t / cm²). 2 When a test specimen (test specimen for voltage withstand measurement) is obtained by applying pressure with ) , it is preferable that the voltage withstand of this test specimen is 500V or higher. Furthermore, it is preferable that the insulation resistance value of the test specimen when 100V is applied is 1000MΩ or higher.

[0059] Such an insulating soft magnetic powder 1 exhibits particularly high insulation between insulating soft magnetic particles 4. Therefore, it is possible to realize a magnetic element in which eddy current losses originating from interparticle eddy currents are sufficiently suppressed.

[0060] Furthermore, if the constituent material of the soft magnetic powder is an Fe-Si-Cr-based soft magnetic material, it is mixed with 2% by mass of epoxy resin per 1 part insulating soft magnetic powder, and the pressure is 294 MPa (3 t / cm²). 2 When a test specimen (a test specimen for measuring magnetic permeability) is obtained by pressurizing it, it is preferable that the magnetic permeability of this test specimen is 31 or higher.

[0061] Such an insulating coated soft magnetic powder 1, containing soft magnetic powder, contributes to the realization of magnetic elements with excellent magnetic properties.

[0062] 2. Method for producing insulating soft magnetic powder Next, a method for producing insulating coated soft magnetic powder according to an embodiment will be described.

[0063] Figure 2 is a process diagram illustrating the method for manufacturing insulating coated soft magnetic powder according to the embodiment. Figures 3 to 10 are schematic diagrams illustrating the method for manufacturing insulating coated soft magnetic powder shown in Figure 2.

[0064] The method for manufacturing the insulating soft magnetic powder shown in Figure 2 comprises a mixing step S102, a first crimping step S104, a second crimping step S106, and a heat treatment step S108. In the mixing step S102, as shown in Figure 3, soft magnetic powder 5 and ceramic powder 6 are mixed to obtain a mixture 7. In the first crimping step S104, the ceramic powder 6 is pulverized by applying mechanical energy to the mixture 7. In the second crimping step S106, the pulverized ceramic powder 6 is fused to the particle surface of the soft magnetic powder 5 by applying a greater amount of mechanical energy to the mixture 7 than in the first crimping step S104. This obtains the insulating soft magnetic powder 1. In the heat treatment step S108, the insulating soft magnetic powder 1 is heat-treated to remove or reduce any residual strain in the insulating soft magnetic powder 1.

[0065] 2.1.Mixing process In mixing step S102, the soft magnetic powder 5 and the ceramic powder 6 are mixed to obtain a mixture 7. Specifically, for example, as shown in Figure 3, the mixture 7 is obtained by placing the soft magnetic powder 5 and the ceramic powder 6 into a container 8. The soft magnetic powder 5 is composed of the soft magnetic material described above.

[0066] The soft magnetic powder 5 may be powder produced by any method. Examples of production methods include various atomization methods such as water atomization, gas atomization, and rotary water flow atomization, as well as reduction, carbonylation, and pulverization methods. Of these, atomization is preferred. In other words, it is preferable that the soft magnetic powder 5 is atomized powder. Atomized powder is fine, highly spherical, and has high production efficiency. In particular, water atomized powder or rotary water flow atomized powder has a thin oxide film on its surface because it is produced by contact between molten metal and water. This oxide film can serve as a base for the insulating film 3. This can improve the adhesion between the soft magnetic particles 2 and the insulating film 3.

[0067] The average particle size of the soft magnetic powder 5 is preferably 1 μm to 50 μm, more preferably 2 μm to 15 μm, and even more preferably 3 μm to 10 μm. This shortens the path of the eddy currents within the insulating soft magnetic particles 4, thereby enabling the realization of a magnetic element with low eddy current loss in the high-frequency range. Furthermore, when the average particle size of the soft magnetic powder 5 is within the above range, the packing efficiency during compaction is improved, thereby enhancing the magnetic properties of the magnetic element.

[0068] The average particle size of the soft magnetic powder 5 is determined by measuring the particle size distribution on a volume basis for the soft magnetic powder 5, for example, by laser diffraction, and obtaining the resulting layered distribution curve. Specifically, in the integrated distribution curve, the particle size at which the cumulative value from the smallest diameter side reaches 50% is defined as the average particle size. An example of a measuring device is the Microtrac HRA9320-X100 manufactured by Nikkiso Co., Ltd.

[0069] The ceramic powder 6 is composed of the aforementioned ceramic material. The average particle size of the ceramic powder 6 may be larger than the average particle size of the soft magnetic powder 5, but it is preferable that it be smaller. This makes it easier for the ceramic powder 6 to be distributed around the particles of the soft magnetic powder 5 in the mixture 7. As a result, in the first crimping step S104 described later, the ceramic powder 6 is more easily sandwiched between the particles of the soft magnetic powder 5 and the container, and between the particles of the soft magnetic powder 5 themselves, making it easier to crush the ceramic powder 6.

[0070] The average particle size of the ceramic powder 6 is preferably 0.005% to 1.0% of the average particle size of the soft magnetic powder 5, more preferably 0.01% to 0.5%, and even more preferably 0.03% to 0.1%. By setting the average particle size of the ceramic powder 6 within the above range, even if there are irregularities on the particle surface of the soft magnetic powder 5, an appropriate impact is more easily applied to the ceramic powder 6 in the first pressing step S104. As a result, the ceramic powder 6 is more easily pulverized, and ultimately, an insulating film 3 with a uniform thickness is more easily formed.

[0071] 2.2. First Crimping Process In the first bonding step S104, the ceramic powder 6 is pulverized by applying mechanical energy to the mixture 7. The pulverized ceramic powder 6 is then temporarily bonded to the particle surface of the soft magnetic powder 5. Temporary bonding means that the ceramic powder 6 or its pulverized form adheres to the surface of the soft magnetic powder 5 with almost no melting. Therefore, when the particle cross-section of the soft magnetic powder 5 is observed under magnification after the ceramic powder 6 has been temporarily bonded, the area ratio of the molten ceramic material is less than 50%, preferably 30% or less.

[0072] In this process, for example, a mechanochemical apparatus is used. This apparatus can add mechanical energy, so it can perform a so-called mechanochemical treatment on the mixture 7. Mechanochemical apparatuses can be broadly classified into two main types based on the principle of adding mechanical energy: material impact type apparatuses and material compression type apparatuses. Examples of material impact type apparatuses include ball mills, planetary mills, planetary ball mills, jet mills, Jacobson mills, vibratory mills, vibro mills, and acoustic resonance mixers. Examples of material compression type apparatuses include Ongmill (registered trademark), Mixmorar (registered trademark), Mechanofusion (registered trademark), Hybridization (registered trademark), Novirta (registered trademark), and Novirta (registered trademark) Belcom. Note that this process may also be a process that adds mechanical energy through an operation that does not involve a mechanochemical treatment, such as an explosion.

[0073] Among these, a containment impact type apparatus is preferably used in this process. In a containment impact type apparatus, appropriate mechanical energy can be applied to the mixture 7 by the movement of the contained object. In this case, if a medium such as a rod or ball is not used, the mechanical energy applied to the mixture 7 can be reduced, and the melting of the ceramic powder 6 can be suppressed.

[0074] Figure 3 schematically shows how mechanical energy is applied to the mixture 7 by a containment impact device. As indicated by arrow A1 in Figure 3, the container 8 vibrates back and forth, causing the mixture 7 contained in the container 8 to vibrate as shown by arrow A2, colliding with the container 8 or with other mixture 7 particles. In other words, the containment impact device shown in Figure 3 is a device that applies acceleration to the mixture 7 and applies an impact due to inertial force. By using such a device, cracks can be created in the ceramic powder 6, as shown in Figure 4. Figure 4 shows the ceramic powder 6 colliding with the inner wall of the container 8 and creating cracks. If further impact is applied in this state, the ceramic powder 6 is pulverized and made finer, as shown in Figure 5. The formed pulverized material 60 is then temporarily pressed onto the particle surface of the soft magnetic powder 5.

[0075] When the container impaction device involves vibration of the container, the vibration frequency is preferably between 10 Hz and 100 Hz, and more preferably between 20 Hz and 80 Hz. This allows for efficient application of mechanical energy to the mixture 7, thereby shortening the time required for this process.

[0076] Furthermore, the magnitude of the acceleration applied to the mixture 7 due to the vibration is 30 m / s². 2 (3G) or more 200m / s 2 (20G) or less is preferable, and 50 m / s 2 (5G) over 150m / s 2 It is more preferable that the pressure is 15G or less. This allows for the application of appropriate mechanical energy to the mixture 7, thereby preventing the ceramic powder 6 from melting or failing to pulverize.

[0077] Alternatively, a containment compression type apparatus may be used in this process. In a containment compression type apparatus, mechanical energy can be applied to the mixture 7 by applying a load that compresses the contents using a compressor. In this case, the load applied to the mixture 7 is preferably between 30 N and 100 N.

[0078] Furthermore, this process may be carried out wet, but it is preferable to carry it out dry. This makes it less likely for moisture and other substances to adhere to the mixture 7, thereby suppressing oxidation and corrosion of the soft magnetic powder 5. Moreover, it can be carried out in an inert gas atmosphere, which can more reliably suppress oxidation of the soft magnetic powder 5.

[0079] The ceramic powder 6 may be subjected to a surface treatment as a pretreatment if necessary. For example, a hydrophobic treatment can be used as a surface treatment. By applying a hydrophobic treatment, the adsorption of moisture onto the ceramic powder 6 is suppressed. This suppresses oxidation and corrosion of the soft magnetic powder 5. Furthermore, the hydrophobic treatment can suppress the aggregation of the ceramic powder 6.

[0080] Examples of hydrophobic treatments include trimethylsilylation and arylation such as phenylation. For trimethylsilylation, a trimethylsilylating agent such as trimethylchlorosilane is used. For arylation, an arylating agent such as aryl halides is used.

[0081] 2.3. Second Crimping Process In the second crimping step S106, a greater amount of mechanical energy is applied to the mixture 7 than in the first crimping step S104.

[0082] In this process, for example, the mechanochemical apparatus described above is used. Of these, a containment compression type apparatus is particularly preferred in this process. However, this process may also involve operations that do not include mechanochemical processing, such as operations that apply mechanical energy, such as explosion.

[0083] Figure 6 is a schematic diagram showing how mechanical energy is applied to the mixture 7 by a containment compression device. The containment compression device shown in Figure 6 comprises a container 91 and a head 92 housed inside the container 91. With the mixture 7 that has undergone the first compression process S104 placed in the container 91, when the container 91 is rotated in the direction of arrow A3, the mixture 7 is squeezed between the inner wall surface of the container 91 and the head 92 and subjected to a shear force. In other words, the containment compression device shown in Figure 6 can perform an operation to apply a shear force to the mixture 7. As a result, as shown in Figure 7, the pulverized material 60 is further pulverized. The pulverized material 60 then melts further, and as shown in Figure 8, a molten material 63 is formed that covers the particle surface of the soft magnetic powder 5, and the molten material 63 is compressed. As a result, the insulating film 3 shown in Figure 1 is obtained. Compression refers to the melting of the ceramic powder 6 or its pulverized material 60 and its adhesion to the surface of the soft magnetic powder 5. Therefore, when the particle cross-section of the soft magnetic powder 5 after the ceramic powder 6 has been pressed onto it is observed under magnification, the area ratio of the molten ceramic material is 50% or more, preferably 70% or more. In this way, the insulating coated soft magnetic powder 1 shown in Figure 1 is obtained.

[0084] Since the molten material 63 has undergone the melting of ceramic material, its surface tends to become smooth. Therefore, according to the above method, an insulating coated soft magnetic powder 1 with a small specific surface area can be manufactured.

[0085] In this process, mechanical energy is applied to the pulverized material 60 in a pre-compressed state to form a molten material 63. By dividing the process of applying mechanical energy into two parts in this way, the molten material 63 can be formed with a thin and uniform thickness. For example, if the molten material 63 is formed without pre-compression, the thickness of the molten material 63 tends to be uneven. Also, if there are irregularities on the particle surface of the soft magnetic powder 5, the depressions cannot be sufficiently filled with the molten material 63. In that case, the specific surface area of ​​the insulating coated soft magnetic powder 1 becomes large. On the other hand, even if only pre-compression is performed, the molten material 63 will not be formed.

[0086] In contrast, by going through the first crimping process S104 and the second crimping process S106, a molten material 63 with a uniform thickness can be formed. Furthermore, even if there are irregularities on the particle surface of the soft magnetic powder 5, the depressions are easily filled with the molten material 63. As a result, an insulating coated soft magnetic powder 1 with a small specific surface area can be efficiently manufactured.

[0087] When a containment compression type device is used in this process, the load applied to the mixture 7 is preferably between 100N and 800N.

[0088] On the other hand, a containment collision type device may be used in this process, in which case the magnitude of the acceleration applied to the mixture 7 due to vibration is 150 m / s². 2 (15G) or more 1000m / s 2 It is preferable that the value is 100G or less.

[0089] The mechanical energy added to the mixture 7 in this process is not particularly limited, as long as it is sufficient to melt the pulverized material 60, but one example is 1 × 10 2 [J / g] or more 1×10 4 It is preferable that the value be less than or equal to [J / g].

[0090] Furthermore, the mechanical energy added to the mixture 7 in this process is preferably 1.1 or greater, and more preferably 5.0 or greater, compared to the mechanical energy added to the mixture 7 in the first pressing process S104, which is set to 1. This balances the added energy, suppressing the melting of the ceramic material in the first pressing process S104 and facilitating the melting of the ceramic material in the second pressing process S106. The mechanical energy can be compared by calculating the amount of heat generated in the mixture 7 based on acceleration, compressive load, etc. Also, considering the balance of mechanical energy added to the mixture 7, it is preferable to use a containment impact type device in the first pressing process S104 and a containment compression type device in this process.

[0091] Furthermore, this process may be carried out wet, but it is preferable to carry it out dry. This makes it less likely for moisture and other substances to adhere to the mixture 7, thereby suppressing oxidation and corrosion of the soft magnetic powder 5. Moreover, it can be carried out in an inert gas atmosphere, which can more reliably suppress oxidation of the soft magnetic powder 5.

[0092] Furthermore, the ceramic powder 6 used in this manufacturing method may also contain secondary particles formed by the aggregation of multiple primary particles. When secondary particles are included, the molten material 63 is more likely to fill in the depressions on the particle surface of the soft magnetic powder 5.

[0093] Figures 9 and 10 are schematic diagrams illustrating how the molten material 63 fills the depressions 52 on the particle surface of the soft magnetic powder 5. Figure 9 is a schematic diagram of the case where the ceramic powder 6 does not contain secondary particles 62, while Figure 10 is a schematic diagram of the case where secondary particles 62 are included.

[0094] If the ceramic powder 6 does not contain secondary particles 62, the ceramic powder 6 consists only of primary particles 61, as shown in Figure 9. In this case, during the first crimping step S104, there is a high probability that the primary particles 61 will be completely contained in the recesses 52, as shown in the left diagram of Figure 9. As a result, the primary particles 61 contained in the recesses 52 are less likely to be crushed even when they collide with the container 8 shown in Figure 9. Furthermore, during the second crimping step S106, no mechanical energy is applied to the primary particles 61 contained in the recesses 52, as shown in the center diagram of Figure 9. Consequently, even after going through the second crimping step S106, there is a high probability that primary particles 61 will remain, as shown in the right diagram of Figure 9. In this case, the insulating properties of the insulating coated soft magnetic powder 1 may decrease.

[0095] On the other hand, when the secondary particles 62 are included in the ceramic powder 6, as shown in the left figure of Fig. 10, even if the secondary particles 62 are accommodated in the recess 52, the probability of complete accommodation becomes low. Then, the secondary particles 62 accommodated in the recess 52 are likely to collide with the container 8 shown in Fig. 10 and be pulverized, and the probability that the recess 52 is filled with the pulverized matter 60 becomes high. Further, in the second crimping step S106, as shown in the central part of Fig. 10, mechanical energy is likely to be applied to the pulverized matter 60 that fills the recess 52. As a result, through the second crimping step S106, as shown in the right figure of Fig. 10, a melt 63 with a smooth surface is formed so as to fill the recess 52.

[0096] The average particle size of the secondary particles 62 in the ceramic powder 6 is preferably 16 or more and 10,000 or less, more preferably 500 or more and 2,000 or less, when the average particle size of the primary particles 61 is taken as 1. Thereby, the above effects can be obtained more reliably.

[0097] Note that the specific surface area of the soft magnetic powder 5 before being subjected to the first crimping step S104 is S1, the specific surface area of the soft magnetic powder 5 after passing through the first crimping step S104 is S2, and the specific surface area of the insulated soft magnetic powder 1 manufactured by this manufacturing method is S3. At this time, it is preferable that the relationship of S3 < S1 < S2 holds. This relationship indicates that sufficient pulverized matter 60 is formed by passing through the first crimping step S104, and sufficient melt 63 is formed by passing through the second crimping step S106.

[0098] At this time, the specific surface area S3 is preferably 50% or more and 95% or less of the specific surface area S1, more preferably 60% or more and 90% or less. By satisfying this relationship, the ceramic material is sufficiently melted, and an insulated soft magnetic powder 1 that coats the particle surface of the soft magnetic powder 5 with a high coverage rate can be obtained. Such an insulated soft magnetic powder 1 has particularly high insulation properties.

[0099] 2.4. Heat treatment step In the heat treatment step S108, if necessary, the insulating-coated soft magnetic powder 1 is subjected to a heat treatment (annealing treatment). By this heat treatment, the strain remaining in the insulating-coated soft magnetic powder 1 is removed or reduced. Thereby, the coercive force of the insulating-coated soft magnetic powder 1 is reduced.

[0100] Also, for the heat treatment, it is possible to expect an effect of enhancing the adhesion between the insulating film 3 and the soft magnetic particles 2 and further smoothing the surface of the insulating film 3. When the specific surface area of the insulating-coated soft magnetic powder 1 after passing through the heat treatment step S108 is S4, it is preferable that the relationship S4 < S3 holds. This relationship enables the production of the insulating-coated soft magnetic powder 1 having a particularly small specific surface area by passing through the heat treatment step S108.

[0101] The heating temperature in the heat treatment is not particularly limited, but is preferably 600°C or higher and 1200°C or lower, more preferably 900°C or higher and 1100°C or lower. The time for performing the heat treatment, that is, the holding time of the heating temperature, is not particularly limited, but is preferably 10 minutes or longer and 10 hours or shorter, more preferably 20 minutes or longer and 6 hours or shorter. By setting the heat treatment conditions within the above range, the strain can be sufficiently removed or reduced as compared with the case where the heat treatment conditions are outside the above range.

[0102] The atmosphere for the heat treatment is not particularly limited, and examples include an oxidizing gas atmosphere containing oxygen gas, air, etc., a reducing gas atmosphere containing hydrogen gas, ammonia decomposition gas, etc., an inert gas atmosphere containing nitrogen gas, argon gas, etc., a reduced pressure atmosphere in which an arbitrary gas is depressurized, and the like. Among these, a reducing gas atmosphere or an inert gas atmosphere is preferably used, and a reduced pressure atmosphere is more preferably used. According to these atmospheres, the oxidation of the soft magnetic particles 2 can be suppressed while removing or reducing the strain.

[0103] The apparatus used for the heat treatment is not particularly limited as long as the above treatment conditions can be set, and a known electric furnace or the like can be adopted.

[0104] 2.5. Effects of the method for manufacturing an insulating-coated soft magnetic powder according to the embodiment As described above, the method for producing insulating coated soft magnetic powder according to this embodiment includes a mixing step S102, a first crimping step S104, and a second crimping step S106. In the mixing step S102, the soft magnetic powder 5 and the ceramic powder 6 are mixed to obtain a mixture 7. In the first crimping step S104, the ceramic powder 6 is pulverized by applying mechanical energy to the mixture 7. In the second crimping step S106, after the first crimping step S104, the pulverized ceramic powder 6 is fused to the particle surface of the soft magnetic powder 5 by applying a greater amount of mechanical energy to the mixture 7 than in the first crimping step S104. This obtains insulating coated soft magnetic powder 1.

[0105] Thus, in the above manufacturing method, the process of applying mechanical energy is divided into two parts. As a result, the molten ceramic powder 63 becomes thin and uniform in thickness, and its surface can be made smooth. Consequently, an insulating coated soft magnetic powder 1 with good insulating properties derived from the ceramic material can be manufactured. Furthermore, even if there are irregularities on the particle surface of the soft magnetic powder 5, the depressions can be filled with the molten material 63. As a result, insulating coated soft magnetic powder 1 with a small specific surface area can be manufactured efficiently. This reduces the amount of binder used to bind the insulating coated soft magnetic particles 4 together, and enables the realization of a magnetic element with high magnetic properties such as magnetic permeability and saturation magnetic flux density.

[0106] Furthermore, it is preferable that the average particle size of the ceramic powder 6 is smaller than the average particle size of the soft magnetic powder 5. This makes it easier for the ceramic powder 6 to be distributed around the particles of the soft magnetic powder 5 in the mixture 7. As a result, it becomes easier to crush the ceramic powder 6 in the first crimping step S104.

[0107] Furthermore, it is preferable that the average particle size of the soft magnetic powder 5 is between 1 μm and 50 μm, and the average particle size of the ceramic powder 6 is between 0.005% and 1.0% of the average particle size of the soft magnetic powder 5. This makes it easier for the ceramic powder 6 to receive an appropriate impact in the first pressing step S104, even if there are irregularities on the particle surface of the soft magnetic powder 5. As a result, the ceramic powder 6 becomes easier to crush, and ultimately a molten material 63 with a uniform film thickness is more easily formed.

[0108] Furthermore, it is preferable that the ceramic powder 6 contains secondary particles 62 formed by the aggregation of multiple primary particles 61. This makes it easier for the secondary particles 62 to fill in the depressions 52, even if the particle surface of the soft magnetic powder 5 has irregularities. As a result, the molten material 63 is formed to fill the depressions 52, and ultimately an insulating coating 3 with a smooth surface and a small specific surface area can be obtained.

[0109] Furthermore, it is preferable that the first crimping step S104 and the second crimping step S106 each include a mechanochemical treatment. Such a treatment allows for appropriate mechanical interaction between the soft magnetic powder 5 and the ceramic powder 6. This makes it possible to form the insulating film 3 without applying excessive strain to the soft magnetic powder 5.

[0110] Furthermore, the first crimping step S104 includes an operation to apply acceleration to the mixture 7 as a mechanochemical treatment. In addition, the second crimping step S106 includes an operation to apply shear force to the mixture 7 as a mechanochemical treatment.

[0111] By performing this operation, it is possible to form an insulating coating 3 that has a particularly small specific surface area, is thin, and has a uniform thickness.

[0112] Furthermore, it is preferable that the specific surface area S3 of the insulating coated soft magnetic powder 1 is 50% to 95% of the specific surface area S1 of the soft magnetic powder 5. As a result, the insulating film 3 of the insulating coated soft magnetic powder 1 is made of sufficiently melted ceramic material and coats the particle surface of the soft magnetic powder 5 with a high coverage rate. Such an insulating coated soft magnetic powder 1 has particularly high insulating properties.

[0113] 3. Compacted magnetic cores and magnetic elements Next, the powdered magnetic core and magnetic element according to the embodiment will be described.

[0114] The magnetic element according to this embodiment is applicable to various magnetic elements equipped with a magnetic core, such as choke coils, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the compacted magnetic core according to this embodiment is applicable to the magnetic cores provided in these magnetic elements.

[0115] Below, we will describe two types of coil components as representative examples of magnetic elements. 3.1. Toroidal type First, we will describe a toroidal coil component, which is an example of a magnetic element according to the embodiment. Figure 11 is a schematic plan view showing a toroidal coil component.

[0116] The coil component 10 shown in Figure 11 has a ring-shaped powdered magnetic core 11 and a conductor 12 wound around this powdered magnetic core 11. Such a coil component 10 is generally called a toroidal coil.

[0117] The compacted magnetic core 11 is obtained by mixing the insulating coated soft magnetic powder and a binder according to the above embodiment, supplying the resulting mixture to a mold, and then pressurizing and molding it. In other words, the compacted magnetic core 11 is a compacted powder containing the insulating coated soft magnetic powder according to the above embodiment. Such a compacted magnetic core 11 has a small specific surface area of ​​the insulating coated soft magnetic powder, good packing properties, and enables the realization of a magnetic element with low eddy current loss. Therefore, the coil component 10 equipped with the compacted magnetic core 11 has low eddy current loss and high magnetic properties such as permeability and magnetic flux density. As a result, when the coil component 10 is mounted on electronic equipment, it is possible to reduce the power consumption of the electronic equipment, improve performance, and miniaturize it.

[0118] Examples of binder materials used in the production of the compacted 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 like magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates like sodium silicate. Thermosetting polyimide or epoxy resins are particularly preferred. These resin materials harden easily when heated and have excellent heat resistance. Therefore, the ease of manufacturing and heat resistance of the compacted magnetic core 11 can be improved. The binder may be added as needed and may be omitted.

[0119] Furthermore, the ratio of binder to insulating soft magnetic powder varies slightly depending on the desired magnetic and mechanical properties of the compacted magnetic core 11 to be manufactured, the allowable eddy current loss, etc., but is preferably around 0.5% by mass to 5.0% by mass, and more preferably around 1.0% by mass to 3.0% by mass. This allows for sufficient bonding of the individual particles of the insulating soft magnetic powder while obtaining a coil component 10 with excellent magnetic properties.

[0120] Various additives may be added to the mixture as needed, for any purpose.

[0121] The materials used to construct the conductor 12 include highly conductive materials, such as metallic materials containing Cu, Al, Ag, Au, Ni, etc. An insulating film may be provided on the surface of the conductor 12 as needed.

[0122] The shape of the compacted magnetic core 11 is not limited to the ring shape shown in Figure 11. For example, it may be a shape in which a part of the ring is missing, a shape in which the longitudinal direction is straight, or a sheet shape, film shape, etc.

[0123] Furthermore, the compacted magnetic core 11 may, if necessary, contain soft magnetic powders other than the insulating coated soft magnetic powder according to the embodiment described above, or non-magnetic powders.

[0124] 3.2. Closed Magnetic Circuit Type Next, we will describe a closed-circuit type coil component, which is an example of a magnetic element according to the embodiment. Figure 12 is a schematic transmission perspective view showing a closed magnetic circuit type coil component.

[0125] The following describes closed-circuit type coil components, focusing on the differences from toroidal type coil components, and omitting explanations of similar aspects.

[0126] As shown in Figure 12, the coil component 20 according to this embodiment is formed by embedding a coil-shaped conductor 22 inside a compacted magnetic core 21. That is, the coil component 20, which is a magnetic element, comprises a compacted magnetic core 21 containing the aforementioned insulating coated soft magnetic powder, and the conductor 22 is molded with the compacted magnetic core 21. This compacted magnetic core 21 has the same configuration as the compacted magnetic core 11 described above. This makes it possible to realize a coil component 20 with low eddy current loss and excellent magnetic properties.

[0127] Coil components 20 of this form can be easily obtained in a relatively small size. Therefore, when coil components 20 are mounted on electronic devices, it is possible to reduce the power consumption of the electronic devices, improve their performance, and make them smaller.

[0128] Furthermore, since the conductor 22 is embedded inside the compacted magnetic core 21, gaps are less likely to form between the conductor 22 and the compacted magnetic core 21. This suppresses vibrations caused by magnetostriction of the compacted magnetic core 21, and thus suppresses the generation of noise associated with these vibrations.

[0129] The shape of the compacted magnetic core 21 is not limited to the shape shown in Figure 12, and may be in the form of a sheet, film, or the like.

[0130] Furthermore, the compacted magnetic core 21 may, if necessary, contain soft magnetic powders other than the insulating coated soft magnetic powder according to the embodiment described above, or non-magnetic powders.

[0131] 4.Electronic equipment Next, an electronic device equipped with a magnetic element according to the embodiment will be described with reference to Figures 13 to 15.

[0132] Figure 13 is a perspective view showing a mobile personal computer, which is an electronic device equipped with magnetic elements according to an embodiment. The personal computer 1100 shown in Figure 13 comprises a main body 1104 equipped with a keyboard 1102 and a display unit 1106 equipped with a display unit 100. The display unit 1106 is rotatably supported by the main body 1104 via a hinge structure. Such a personal computer 1100 incorporates magnetic elements 1000, such as a choke coil or inductor for a switching power supply, or a motor.

[0133] Figure 14 is a plan view showing a smartphone, which is an electronic device equipped with magnetic elements according to an embodiment. The smartphone 1200 shown in Figure 14 is equipped with a plurality of operation buttons 1202, an earpiece 1204, and a microphone 1206. A display unit 100 is also positioned between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 incorporates magnetic elements 1000, such as inductors, noise filters, and motors.

[0134] Figure 15 is a perspective view showing a digital still camera, which is an electronic device equipped with a magnetic element according to the embodiment. The digital still camera 1300 generates an imaging signal by photoelectric conversion of the light image of the subject using an image sensor such as a CCD (Charge Coupled Device).

[0135] The digital still camera 1300 shown in Figure 15 includes a display unit 100 located on the back of the case 1302. The display unit 100 functions as a viewfinder, displaying the subject as an electronic image. A light-receiving unit 1304, including an optical lens and a CCD, is provided on the front side of the case 1302, i.e., the back side in the figure.

[0136] When the photographer confirms the subject image displayed on the display unit 100 and presses the shutter button 1306, the imaging signal from the CCD at that moment is transferred and stored in the memory 1308. Such a digital still camera 1300 also incorporates magnetic elements 1000, such as an inductor and a noise filter.

[0137] Examples of electronic devices according to this embodiment include, in addition to the personal computer in Figure 13, the smartphone in Figure 14, and the digital still camera in Figure 15, mobile phones, tablet terminals, watches, inkjet printers and other inkjet ejection devices, laptop personal computers, televisions, video cameras, video tape recorders, car navigation systems, pagers, electronic organizers, electronic dictionaries, calculators, electronic game devices, word processors, workstations, video phones, security television monitors, electronic binoculars, POS terminals, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasound diagnostic devices, medical devices such as electronic endoscopes, fish finders, various measuring instruments, instruments for vehicles, aircraft, and ships, mobile control devices such as automobile control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, and flight simulators.

[0138] As described above, such electronic devices are equipped with magnetic elements according to the embodiment. This allows the effects of magnetic elements, which have low eddy current losses and high magnetic permeability, to be enjoyed, thereby improving the performance and miniaturization of electronic devices.

[0139] 5. Mobile Next, a mobile body equipped with a magnetic element according to this embodiment will be described with reference to Figure 16. Figure 16 is a perspective view showing an automobile, which is a mobile body equipped with a magnetic element according to the embodiment.

[0140] Automobile 1500 incorporates magnetic elements 1000. Specifically, magnetic elements 1000 are incorporated into various automotive components such as car navigation systems, anti-lock braking systems (ABS), engine control units, battery control units for hybrid and electric vehicles, vehicle attitude control systems, autonomous driving systems, and other electronic control units (ECUs), as well as drive motors, generators, and air conditioning units.

[0141] As described above, such a mobile body is equipped with a magnetic element according to the embodiment. This allows the benefits of a magnetic element with low eddy current loss and high permeability to be enjoyed, and the performance and miniaturization of the equipment mounted on the mobile body can be improved.

[0142] In addition to the automobile shown in Figure 16, the mobile body according to this embodiment may also be, for example, a motorcycle, bicycle, aircraft, helicopter, drone, ship, submarine, train, rocket, spacecraft, etc.

[0143] The method for producing insulating coated soft magnetic powder, insulating coated soft magnetic powder, compacted magnetic core, magnetic element, electronic device, and mobile body of the present invention have been described above based on preferred embodiments, but the present invention is not limited thereto.

[0144] For example, in the above embodiment, compacted bodies such as compacted magnetic cores were described as examples of applications for the insulating coated soft magnetic powder of the present invention, but the examples of applications are not limited to this, and may also be magnetic devices such as magnetic fluids, magnetic heads, and magnetic shielding sheets. Furthermore, the shape of the compacted magnetic core and magnetic element is not limited to those shown in the figures, and may be any shape.

[0145] Furthermore, the method for producing the insulating coated soft magnetic powder of the present invention may be modified by adding any desired steps to the above embodiment. [Examples]

[0146] Next, specific embodiments of the present invention will be described. 6. Preparation of insulating soft magnetic powder 6.1. Example 1 First, a metal powder of an Fe-Si-Cr alloy, manufactured by the water atomization method, was prepared as a soft magnetic powder. This metal powder is an Fe-based alloy powder with Fe as the main component, containing 4.5% by mass of Cr and 3.5% by mass of Si. The conditions for the soft magnetic powder are shown in Table 1.

[0147] On the other hand, aluminum oxide powder was prepared as the ceramic powder. The conditions for the ceramic powder are shown in Table 1. In addition, the ceramic powder contained secondary particles, and the particle size ratio of secondary particles to primary particles was 1200.

[0148] Next, the metal powder and aluminum oxide powder were mixed (mixing step). The amount of aluminum oxide powder added to the metal powder was 1 volume%. The resulting mixture was placed in a containment impact type apparatus and mechanical energy was applied (first crimping step). The conditions for the first crimping step are shown in Table 1.

[0149] Next, the mixture processed in the containment impact type apparatus was then fed into the containment compression type apparatus and mechanical energy was applied (second compression step). This yielded insulating coated soft magnetic powder. The conditions for the second compression step are shown in Table 1. The energy ratio is the ratio of the mechanical energy applied in the second compression step to the mechanical energy applied in the first compression step, with the mechanical energy applied in the first compression step being set to 1. The specific surface area ratio is the ratio of the specific surface area of ​​the soft magnetic powder after the completion of the second compression step to the specific surface area of ​​the soft magnetic powder.

[0150] Next, the insulating coated soft magnetic powder was subjected to heat treatment (heat treatment process). An electric furnace was used for the heat treatment, and the treatment conditions were as follows: under an argon gas atmosphere, the heating rate was 5°C / min, the heating temperature was 900°C, and the heating time was 1 hour. After the heat treatment was completed, it was cooled to 25°C.

[0151] 6.2. Examples 2-7 Insulator-coated soft magnetic powder was obtained in the same manner as in Example 1, except that the manufacturing conditions were changed as shown in Table 1. In addition, except for some examples, the ceramic powder contained secondary particles, but the particle size ratio of secondary particles to primary particles was 700 to 1800.

[0152] 6.3. Example 8 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that silicon oxide powder shown in Table 1 was used as the ceramic powder, and the other conditions were as shown in Table 1.

[0153] 6.4. Example 9 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that zirconium oxide powder shown in Table 2 was used as the ceramic powder, and the other conditions were as shown in Table 2.

[0154] 6.5. Example 10 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that titanium oxide powder shown in Table 2 was used as the ceramic powder, and the other conditions were as shown in Table 2.

[0155] 6.6. Example 11 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that the ratio of the mechanical energy applied in the second crimping step to the mechanical energy applied in the first crimping step (energy ratio) was changed to the value shown in Table 2, and other conditions were set as shown in Table 2.

[0156] 6.7. Example 12 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that the acceleration in the first crimping step was changed to the value shown in Table 2, and the other conditions were as shown in Table 2.

[0157] 6.8. Example 13 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that the heat treatment step was omitted.

[0158] 6.9. Comparative Example 1 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that the second crimping step was omitted.

[0159] 6.10. Comparative Example 2 An insulating coated soft magnetic powder was obtained in the same manner as in Example 1, except that the first crimping step was omitted.

[0160] 6.11. Comparative Example 3 Without forming an insulating film, the soft magnetic powder was used as the powder in Comparative Example 3.

[0161] 7. Evaluation of insulating soft magnetic powder 7.1. Specific surface area of ​​insulating coating The specific surface area was measured for the powders of each example and comparative example. Specifically, the specific surface area was measured for the powder before the start of the first crimping process (soft magnetic powder), the powder after the completion of the first crimping process, the powder after the completion of the second crimping process, and the powder after the completion of the heat treatment process. The measurement results are shown in Tables 1 and 2.

[0162] Furthermore, the specific surface area of ​​the powder after the second crimping process was defined as the "measured specific surface area." The ratio of the measured specific surface area to the "theoretical specific surface area," which was calculated from the average particle size and true specific gravity of the soft magnetic powder, was then calculated as the "ratio of measured value to theoretical value." The calculation results are shown in Tables 1 and 2.

[0163] 7.2. Average thickness of the insulating coating First, the cross-section of the insulating coated soft magnetic powder was observed using a scanning transmission electron microscope. Then, the average thickness of the insulating coating was measured from the observed images. The measurement results are shown in Tables 1 and 2.

[0164] 7.3. Coercivity For each example and comparative example, the coercivity of the powders was measured using a Tamagawa Seisakusho VSM system TM-VSM1230-MHHL as the magnetization measuring device. The measured coercivity was then evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2.

[0165] A: The coercivity is less than 5.0 [Oe]. B: Coercivity is 5.0 [Oe] or more and less than 8.0 [Oe] C: Coercivity is 8.0 [Oe] or more and less than 10.0 [Oe]. D: Coercivity of 10.0 [Oe] or higher

[0166] 7.4. Dielectric Strength and Insulation Resistance Test specimens were prepared using the powders of each example and comparative example, and the withstand voltage and insulation resistance values ​​at 100V were measured for the obtained specimens. The measurement results are shown in Tables 1 and 2.

[0167] 7.5.Fillability The packing properties of the powders in each example and comparative example were evaluated by the following method.

[0168] First, the apparent density of the powders in each example and comparative example was measured. Specifically, the measurements were performed in accordance with the method for measuring the apparent density of metal powders specified in JIS Z 2504:2012.

[0169] Next, the true density of the powders in each example and comparative example was measured using the constant volume expansion method. The packing efficiency [%] was calculated by dividing the apparent density by the true density, and each packing efficiency was evaluated according to the following criteria. The evaluation results are shown in Tables 1 and 2.

[0170] A: The filling rate is 40% or more. B: The filling rate is 35% or more but less than 40%. C: The filling rate is 30% or more but less than 35%. D: The filling rate is less than 30%.

[0171] 7.6.Magnetic permeability Test specimens were prepared using the powders of each example and comparative example, and the magnetic permeability of the obtained specimens was measured. The measurement results were then evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1 and 2.

[0172] A: The magnetic permeability is 31 or higher. B: The magnetic permeability is 30 or higher but less than 31. C: Permeability is 29 or higher and less than 30. D: The magnetic permeability is less than 29.

[0173] [Table 1]

[0174] [Table 2]

[0175] As is clear from Tables 1 and 2, the powders of each example were found to produce test specimens with higher dielectric strength and insulation resistance compared to the powders of each comparative example. In particular, it was found that performing both the first and second crimping steps was effective in improving insulation performance.

[0176] Furthermore, in each example, the ratio of the measured specific surface area to the theoretical specific surface area was significantly reduced compared to the powders of each comparative example. It was also found that having this value within a predetermined range improved packing performance. From these findings, it is recognized that the amount of binder used during compaction molding can be reduced with the powders of each example, and as a result, magnetic elements with high magnetic properties can be manufactured. Furthermore, it was found that a powder with low coercivity can be obtained by going through a heat treatment process. [Explanation of symbols]

[0177] 1...Insulating coated soft magnetic powder, 2...Soft magnetic particles, 3...Insulating coating, 4...Insulating coated soft magnetic particles, 5...Soft magnetic powder, 6...Ceramic powder, 7...Mixture, 8...Container, 10...Coil component, 11...Flattened magnetic core, 12...Conducting wire, 20...Coil component, 21...Flattened magnetic core, 22...Conducting wire, 52...Recess, 60...Powdered material, 61...Primary particles, 62...Secondary particles, 63...Molten material, 91...Container, 92...Head, 100...Display unit, 1000...Magnetic element, 1100...Personal computer, 110 2…Keyboard, 1104…Main unit, 1106…Display unit, 1200…Smartphone, 1202…Operation buttons, 1204…Earpiece, 1206…Earpiece, 1300…Digital still camera, 1302…Case, 1304…Light receiving unit, 1306…Shutter button, 1308…Memory, 1500…Automobile, A1…Arrow, A2…Arrow, A3…Arrow, S102…Mixing process, S104…First crimping process, S106…Second crimping process, S108…Heat treatment process

Claims

1. A mixing step of mixing soft magnetic powder and ceramic powder to obtain a mixture, A first compression step involves crushing the ceramic powder by applying mechanical energy to the mixture, A second crimping step is performed after the first crimping step, in which a greater mechanical energy than that used in the first crimping step is applied to the mixture to fuse the pulverized ceramic powder to the particle surface of the soft magnetic powder, thereby obtaining an insulating coated soft magnetic powder. It has, A method for producing an insulating coated soft magnetic powder, characterized in that the ceramic powder contains secondary particles formed by the aggregation of a plurality of primary particles.

2. The method for producing an insulating coated soft magnetic powder according to claim 1, wherein the average particle size of the ceramic powder is smaller than the average particle size of the soft magnetic powder.

3. The method for producing an insulating coated soft magnetic powder according to claim 2, wherein the average particle size of the soft magnetic powder is 1 μm or more and 50 μm or less, and the average particle size of the ceramic powder is 0.005% or more and 1.0% of the average particle size of the soft magnetic powder.

4. A method for producing insulating coated soft magnetic powder according to any one of claims 1 to 3, wherein the first crimping step and the second crimping step each include treatment by a mechanochemical method.

5. The first crimping step includes, as a process, an operation of applying acceleration to the mixture, The method for producing insulating coated soft magnetic powder according to claim 4, wherein the second crimping step includes an operation to apply a shear force to the mixture as the treatment.

6. A method for producing an insulating coated soft magnetic powder according to any one of claims 1 to 5, wherein the specific surface area of ​​the insulating coated soft magnetic powder is 50% or more and 95% or less of the specific surface area of ​​the soft magnetic powder.

7. Soft magnetic powder and The particle surface of the soft magnetic powder is coated with an insulating film containing a ceramic material, It has, Let d be the average particle size of the soft magnetic powder, ρ be the true specific gravity of the soft magnetic powder, let s = 6 / (ρ・d) be the theoretical specific surface area s, and let S be the measured specific surface area. An insulating coated soft magnetic powder characterized in that the measured specific surface area S is 2.3 times or more and 4.0 times or less the theoretical specific surface area s.

8. When a test specimen for dielectric strength measurement is obtained by mixing with 2% by mass of epoxy resin and pressurizing it at 294 MPa (3 t / cm²), The withstand voltage of the aforementioned test specimen for withstand voltage measurement is 500V or higher. The insulating coated soft magnetic powder according to claim 7, wherein the insulation resistance value of the test specimen for voltage withstand measurement when 100V is applied is 1000 MΩ or more.

9. The constituent material of the soft magnetic powder is an Fe-Si-Cr soft magnetic material. When a test specimen for magnetic permeability measurement is obtained by mixing with 2% by mass of epoxy resin and pressurizing it at 294 MPa (3 t / cm²), The insulating coated soft magnetic powder according to claim 7 or 8, wherein the permeability of the test specimen for measuring magnetic permeability is 31 or greater.

10. A compacted magnetic core characterized by containing the insulating coated soft magnetic powder described in any one of claims 7 to 9.

11. A magnetic element characterized by comprising a compacted magnetic core as described in claim 10.

12. An electronic device characterized by comprising the magnetic element described in claim 11.

13. A mobile body characterized by comprising the magnetic element described in claim 11.

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