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 suppressing eddy current loss in a high-frequency range and a manufacturing a magnetic element with high magnetic permeability, a method for manufacturing the same, a dust core containing the insulator-coated soft magnetic powder, a magnetic element including the dust core, and an electronic device and a mobile object including the magnetic element.SOLUTION: An insulator-coated soft magnetic powder includes a soft magnetic powder and an insulating coating that covers the surface of the soft magnetic powder and contains a fluorine compound, and the soft magnetic powder has an average particle size of 1 μm or more and 15 μm or less, and the insulating coating has an average thickness of 5 nm or more and 50 nm or less, and the fluorine compound has a relative dielectric constant of 5.0 or less.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 a magnetic material comprising an iron-based soft magnetic powder having an inorganic insulating coating on its surface and a fluororesin coating formed on the surface of the inorganic insulating coating. The fluororesin coating is a composite fluororesin coating consisting of a modified fluorine coating film formed on the surface of the inorganic insulating coating and a perfluororesin coating formed on the modified fluorine coating film.

[0003] Such a fluororesin coating has excellent heat resistance, making the magnetic material described in Patent Document 1 suitable for producing soft magnetic cores to be attached to the heating coil of an induction hardening device, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-188680 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, soft magnetic cores have been increasingly used in the high frequency range. In the high frequency range, changes in the magnetic field generated inside the soft magnetic core generate eddy currents, which cause eddy current loss. One factor in suppressing eddy currents is the dielectric constant of the insulating film that coats the particle surface of the soft magnetic powder. Eddy currents can be suppressed by lowering the dielectric constant.

[0006] In the magnetic material described in Patent Document 1, an inorganic insulating coating is formed on the surface of iron-based soft magnetic powder, and a fluororesin coating is formed on the surface of this coating. The inorganic insulating coating has a relatively high dielectric constant, so it has the problem of not being able to sufficiently suppress eddy currents that occur between particles in the high frequency range.

[0007] On the other hand, while it is possible to suppress eddy currents between particles by increasing the thickness of the insulating coating, this reduces the volume ratio of the soft magnetic material in the soft magnetic core, which reduces the magnetic permeability of the soft magnetic core and makes it difficult to miniaturize the soft magnetic core. [Means for solving the problem]

[0008] The insulator-coated soft magnetic powder according to the application example of the present invention is soft magnetic powder; coating the particle surfaces of the soft magnetic powder; Consists of PTFE or PFA fluorine compounds R An insulating coating; Equipped with The average particle size of the soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The fluorine compound has a relative dielectric constant of 5.0 or less.

[0009] A method for producing an insulator-coated soft magnetic powder according to an application example of the present invention includes: a step of mixing a soft magnetic powder with a fluorine compound powder composed of a fluorine compound, and mechanically adhering the fluorine compound powder to the particle surfaces of the soft magnetic powder to form an insulating coating that coats the particle surfaces of the soft magnetic powder, thereby producing an insulator-coated soft magnetic powder; The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The fluorine compound has a relative dielectric constant of 5.0 or less.

[0010] A method for producing an insulator-coated soft magnetic powder according to an application example of the present invention includes: a step of forming an insulating coating containing a fluorine compound and coating the particle surface of the soft magnetic powder by causing a polymerization reaction of a fluorine-containing gas with a monomer gas, thereby producing an insulator-coated soft magnetic powder; The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The fluorine compound has a relative dielectric constant of 5.0 or less.

[0011] A method for producing an insulator-coated soft magnetic powder according to an application example of the present invention includes: a step of polymerizing a fluorine compound precursor containing fluorine atoms by a sol-gel method to form an insulating coating containing a fluorine compound and coating the particle surfaces of the soft magnetic powder, thereby producing an insulator-coated soft magnetic powder; The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The fluorine compound has a relative dielectric constant of 5.0 or less.

[0012] A powder magnetic core according to an application example of the present invention is The magnetic material is characterized by containing an insulator-coated soft magnetic powder according to an application example of the present invention.

[0013] 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.

[0014] 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.

[0015] 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]

[0016] [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. DETAILED DESCRIPTION OF THE INVENTION

[0017] 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.

[0018] 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."

[0019] The insulator-coated soft magnetic particles 4 shown in FIG. 1 have 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 contain a soft magnetic material described below. The insulating coating 3 is provided so as to cover the surface of the soft magnetic particles 2, and has insulating properties. Note that the term "coated" in this specification is a concept that includes not only a state in which the entire surface of the soft magnetic particles 2 is covered, but also a state in which part of the surface is covered. In the following description, the aggregate of the soft magnetic particles 2 will also be referred to as "soft magnetic powder."

[0020] As will be described later, a powder magnetic core obtained by compacting the insulator-coated soft magnetic powder 1 has high interparticle insulation. This allows for reduced eddy current loss in a magnetic element including the powder magnetic core. As a result, the insulator-coated soft magnetic powder 1 contributes to the realization of a magnetic element with low loss (core loss) in the high frequency range.

[0021] 1.1. Soft magnetic particles As described above, the soft magnetic particles 2 contain a soft magnetic material. Examples of soft magnetic materials include materials containing at least one of Fe, Ni, and Co as a main component, i.e., materials containing at least 50% of these elements in terms of atomic ratio. In addition to these main components, 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 characteristics. The soft magnetic material may also contain unavoidable impurities, provided that the effects of this embodiment are not impaired. Inevitable impurities are impurities unintentionally mixed into raw materials or during manufacturing. Inevitable impurities include all elements other than those listed above, including, for example, O, N, S, Na, Mg, and K.

[0022] 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 alloys, Fe-Co alloys, Fe-Ni-Co alloys, Fe-Si-B alloys, Fe-Si-BC alloys, Fe-Si-B-Cr-C alloys, Fe-Si-Cr alloys, Fe-B alloys, Fe-PC alloys, Fe-Co-Si-B alloys, Fe-Si-B-Nb alloys, Fe-Si-B-Nb-Cu alloys, Fe-Zr-B alloys, Fe-Cr alloys, and Fe-Cr-Al alloys, Ni alloys such as Ni-Si-B alloys and Ni-PB alloys, and Co alloys such as Co-Si-B alloys.

[0023] 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.

[0024] The content of the main component in the soft magnetic material is preferably 50% or more, more preferably 70% 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.

[0025] 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.

[0026] Examples of amorphous materials 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 alloys; Ni-based alloys such as Ni-Si-B and Ni-PB alloys; and Co-based alloys such as Co-Si-B alloys.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] In the particle size distribution of the soft magnetic powder on a volume basis, when the particle diameter at which the cumulative frequency is 50% is defined as the average particle diameter, the average particle diameter of the soft magnetic powder is 1 μm or more and 15 μm or less. When the average particle diameter of the soft magnetic powder is within this range, the path of eddy currents within the soft magnetic particles 2 is shortened, thereby sufficiently reducing eddy current loss in the magnetic element in the high frequency range. Furthermore, when the average particle diameter of the 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 magnetic permeability and saturation magnetic flux density.

[0032] If the average particle size of the 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, increasing eddy current loss due to eddy currents between particles. On the other hand, if the average particle size of the soft magnetic powder is above the upper limit, the path of eddy currents within particles becomes longer, increasing eddy current loss due to eddy currents within particles.

[0033] The average particle size of the soft magnetic powder is more preferably 2 μm or more and 12 μm or less, and even more preferably 3 μm or more and 9 μm or less. The particle size distribution of the soft magnetic powder on a volume basis can be obtained by, for example, a laser diffraction method.

[0034] 1.2.Insulating Coating The insulating coating 3 covers the surface of the soft magnetic particles 2. The insulating coating 3 contains a fluorine compound. Fluorine compounds are characterized by a low relative dielectric constant. In a powder core obtained by compacting the insulator-coated soft magnetic powder 1, the value of capacitive reactance can be increased by lowering the relative dielectric constant of the insulating coating 3. The capacitive reactance R is expressed by the following formula (1).

[0035] R=1 / (2πfC) … (1) In the above formula (1), f is the frequency at which the insulator-coated soft magnetic powder 1 is used, and C is the electrostatic capacitance of the system via the insulating coating 3. Furthermore, C is expressed by the following formula (2).

[0036] C=Sk / d … (2) In the above formula (2), S is the surface area of ​​the soft magnetic particle 2, k is the dielectric constant of the insulating coating 3, and d is the film thickness of the insulating coating 3.

[0037] If the capacitive reactance R can be increased, it is possible to suppress eddy currents that flow between the insulator-coated soft magnetic powder particles 1 when a current is passed through a magnetic element having a powder magnetic core. This makes it possible to suppress eddy current loss, thereby improving the performance of the magnetic element.

[0038] According to the above formulas (1) and (2), if the dielectric constant k of the insulating coating 3 can be reduced, the capacitance C can be reduced without changing the surface area S of the soft magnetic particles 2 or the film thickness d of the insulating coating 3. This allows the capacitive reactance R to be increased.

[0039] It is possible to reduce the capacitance C by reducing the surface area S or increasing the film thickness d. However, to reduce the surface area S, the particle size of the soft magnetic particles 2 must be further reduced. This would likely reduce the packing density of the soft magnetic particles 2 in the powder magnetic core, potentially resulting in a decrease in magnetic properties such as magnetic permeability and saturation magnetic flux density. Furthermore, increasing the film thickness d would also result in a relative decrease in the occupancy rate of the soft magnetic particles 2 in the powder magnetic core, potentially resulting in a decrease in magnetic properties. Therefore, by reducing the dielectric constant k of the insulating coating 3, eddy current loss can be suppressed without degrading the magnetic properties of the powder magnetic core.

[0040] By including a fluorine compound in insulating coating 3, the dielectric constant can be reduced without reducing the insulating properties of insulating coating 3. This makes it possible to suppress eddy current loss without reducing the DC dielectric strength voltage of the powder magnetic core.

[0041] As mentioned above, fluorine compounds have a low relative dielectric constant, and this relative dielectric constant is preferably 5.0 or less, more preferably 3.0 or less, and even more preferably 2.5 or less. This allows the dielectric constant k of the insulating coating 3 to be sufficiently low. The relative dielectric constant of fluorine compounds is determined by the method specified in JIS K 6935-2:1999. The measurement frequency is 1 MHz.

[0042] Furthermore, fluorine compounds have low surface tension and therefore excellent hydrophobicity, so the insulator-coated soft magnetic powder 1 has excellent moisture resistance and can suppress rusting of the soft magnetic particles 2 due to moisture absorption.

[0043] The fluorine compound is not particularly limited as long as it is a compound containing a fluorine atom. Examples of the fluorine compound include fully fluorinated resins such as PTFE (polytetrafluoroethylene resin), partially fluorinated resins such as PVF (polyvinylidene fluoride) and PCTFE (polychlorotrifluoroethylene), and various fluorine resins such as copolymers such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether resin), FEP (fluorinated ethylene propylene resin), PFEP (hexafluoroethylene propylene resin), and E / TFE (ethylene / tetrafluoroethylene copolymer), and one or a mixture of two or more of these can be used.

[0044] The fluorine compound may be a coupling agent containing a fluorine atom, a compound derived from a metal alkoxide containing a fluorine atom, or a polymer of a monomer gas containing a fluorine atom. Examples of the coupling agent containing a fluorine atom include fluoroalkylsilane and fluoroarylsilane. The metal alkoxide and the monomer gas are as described below.

[0045] Furthermore, fluorine compounds have the advantage of being easy to increase the coverage rate on the surface of the soft magnetic particles 2 due to their low Young's modulus. Therefore, the insulating coating 3 containing a fluorine compound has excellent insulating properties even when thin, and its low dielectric constant contributes to the realization of magnetic elements with particularly low eddy current loss. Furthermore, the low Young's modulus promotes optimization of the positions of the insulator-coated soft magnetic particles 4 when the insulator-coated soft magnetic powder 1 is compressed, contributing to an increase in the packing rate. Therefore, a magnetic element with excellent magnetic properties can be obtained.

[0046] The Young's modulus of the fluorine compound is preferably 3.0 GPa or less, more preferably 0.05 GPa to 2.0 GPa, and even more preferably 0.1 GPa to 1.0 GPa. Using a fluorine compound with such a Young's modulus can particularly increase the coverage of the insulating coating 3 on the surface of the soft magnetic particles 2, and facilitate more uniform thickness of the insulating coating 3. This can further increase the packing rate of the soft magnetic powder in the powder core. If the Young's modulus exceeds the upper limit, the rigidity of the insulating coating 3 increases, which may cause the insulating coating 3 to peel off easily. On the other hand, the Young's modulus may be below the lower limit, but the rigidity of the insulating coating 3 may be too low, which may result in the insulating coating 3 being torn off during compaction depending on the thickness of the insulating coating 3 and the shape of the soft magnetic particles 2.

[0047] The insulating coating 3 may contain components other than fluorine compounds. Examples of components other than fluorine compounds include organic materials other than fluorine compounds, glass materials, and inorganic materials such as ceramic materials. The content of components other than fluorine compounds in the insulating coating 3 is preferably 30% by mass or less, and more preferably 10% by mass or less.

[0048] Insulating coating 3 may be composed of multiple layers as long as it contains a layer containing a fluorine compound. However, from the viewpoints of ease of peeling between layers and difficulty in thinning the film thickness, it is preferable that insulating coating 3 be a single layer.

[0049] The average thickness of the insulating coating 3 is preferably 5 nm or more and 50 nm or less, more preferably 10 nm or more and 40 nm or less, and even more preferably 15 nm or more and 30 nm or less. This allows the packing rate of the soft magnetic powder in the powder core to be increased while ensuring sufficient insulation of the insulating coating 3. If the average thickness of the insulating coating 3 is below the lower limit, the insulating properties of the insulating coating 3 may be insufficient, depending on the material of the insulating coating 3. On the other hand, if the average thickness of the insulating coating 3 is above the upper limit, the insulating coating 3 may be prone to peeling, or the packing rate of the soft magnetic powder in the powder core may be reduced, depending on the material of the insulating coating 3.

[0050] 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 this calculation result is used as the average thickness of the insulating coating 3. The extent of the insulating coating 3 can be confirmed, for example, by EDX analysis (energy dispersive X-ray analysis), Auger electron spectroscopy, or the like.

[0051] Furthermore, it is preferable that the surface of the insulating coating 3 is subjected to a hydrophilization treatment. By subjecting the insulating coating 3 to a hydrophilization treatment, the dispersibility of the insulator-coated soft magnetic powder 1 in the organic binder is improved. This makes it possible to increase the packing density of the insulator-coated soft magnetic powder 1 when the insulator-coated soft magnetic powder 1 is compressed together with an organic binder to obtain a powder core. As a result, a magnetic element with excellent magnetic properties can be realized.

[0052] It is believed that hydroxyl groups are introduced into the surface of the insulating coating 3 that has been subjected to hydrophilic treatment, replacing the fluorine atoms contained in the fluorine compound. These hydroxyl groups are then believed to produce hydrophilicity. Examples of hydrophilic treatments include plasma treatment, ozone treatment, corona treatment, and ultraviolet irradiation treatment. In particular, plasma treatment or ozone treatment is preferably used, as this allows for efficient and high-density hydrophilic treatment. Examples of processing gases for plasma treatment include water vapor, oxygen, argon, and nitrogen.

[0053] The insulating coating 3 preferably has a coverage of 40% or more on the surface of the soft magnetic particles 2, and more preferably 60% to 95%. This sufficiently increases the probability that the insulating coating 3 will insulate the soft magnetic particles 2 from each other when the insulator-coated soft magnetic powder 1 is compacted. Therefore, setting the coverage within the above range contributes to the realization of a magnetic element with particularly low eddy current loss. Note that the coverage may exceed the above upper limit, but is preferably equal to or less than the above upper limit, from the viewpoint of ensuring sufficient insulation between particles and easily producing an insulator-coated soft magnetic powder 1 with a stable coverage.

[0054] The coverage of the insulating coating 3 can be determined by a surface-sensitive elemental analysis method, such as elemental analysis by X-ray photoelectron spectroscopy (XPS). Specifically, the ratio of elements specific to the soft magnetic particles 2 is measured by elemental analysis by XPS on the surface of the insulator-coated soft magnetic particles 4. Next, the insulating coating 3 is removed by a removal process. Examples of this process include liquid-phase treatment using a liquid that dissolves the insulating coating 3 and gas-phase treatment that decomposes and removes the insulating coating 3. Removal of the insulating coating 3 exposes the surface of the soft magnetic particles 2. Next, elemental analysis by XPS is performed on the surface again to calculate the ratio of elements specific to the soft magnetic particles 2. Here, as an example, the Si ratio is measured from the peak area ratio of the Si 2p peak obtained by elemental analysis by XPS. Then, when the Si ratio after the process is set to 100, the relative value X of the Si ratio before the process is calculated. The value 100-X corresponds to the amount of Si in the soft magnetic particles 2 that is covered by the insulating coating 3. As a result, the coverage of the insulating coating 3 can be set to 100-X.

[0055] 1.3. Advantages of this embodiment As described above, the insulator-coated soft magnetic powder 1 according to this embodiment comprises a soft magnetic powder and an insulating coating 3 containing a fluorine compound and coating the particle surfaces of the soft magnetic powder (surfaces of the soft magnetic particles 2). The soft magnetic powder has an average particle size of 1 μm or more and 15 μm or less, and the insulating coating 3 has an average thickness of 5 nm or more and 50 nm or less. The fluorine compound has a relative dielectric constant of 5.0 or less.

[0056] With this configuration, the soft magnetic powder has a sufficiently small diameter, which shortens the path of eddy currents within the soft magnetic particles 2. Furthermore, the insulating properties of the insulating coating 3 can be sufficiently ensured without increasing the thickness of the insulating coating 3. This allows the filling rate of the soft magnetic powder in the powder core to be increased while suppressing eddy currents between particles. As a result, eddy current loss in the high frequency range of the magnetic element can be suppressed, and magnetic properties such as magnetic permeability can be improved. In other words, an insulator-coated soft magnetic powder 1 that can be used to manufacture such magnetic elements can be obtained.

[0057] Furthermore, the fluorine compound is preferably PTFE or PFA. These fluorine compounds have a particularly low relative dielectric constant and a low Young's modulus. By using a fluorine compound with a low Young's modulus, it becomes easier to increase the coverage of the fluorine compound on the surface of the soft magnetic particles 2. Therefore, the insulating coating 3 containing these fluorine compounds has excellent insulating properties even when thin and a low dielectric constant, contributing to the realization of a magnetic element with particularly low eddy current loss.

[0058] As mentioned above, the Young's modulus of the fluorine compound is preferably 3.0 GPa or less. This makes it possible to particularly increase the coverage of the insulating coating 3 on the surface of the soft magnetic particles 2, and also makes it easier to make the thickness of the insulating coating 3 more uniform. This makes it possible to further increase the filling rate of the soft magnetic powder in the dust core.

[0059] Furthermore, it is preferable that the surface of the insulating coating 3 is subjected to a hydrophilization treatment. This improves the dispersibility of the insulator-coated soft magnetic powder 1 in the organic binder. As a result, when the insulator-coated soft magnetic powder 1 is compressed together with the organic binder to obtain a powder core, the packing density of the insulator-coated soft magnetic powder 1 can be increased.

[0060] As mentioned above, the coverage of the insulating coating 3 is preferably 40% or more. This sufficiently increases the probability that the soft magnetic particles 2 will be insulated from each other by the insulating coating 3 when the insulator-coated soft magnetic powder 1 is compacted.

[0061] 2. Manufacturing method of insulator-coated soft magnetic powder Next, a method for producing the insulator-coated soft magnetic powder according to the embodiment will be described.

[0062] FIG. 2 is a process diagram illustrating the method for producing the insulator-coated soft magnetic powder according to the embodiment.

[0063] The method for producing an insulator-coated soft magnetic powder shown in FIG. 2 includes a preparation step S102 and an insulating coating forming step S104.

[0064] 2.1. Preparation process In the preparation step S102, soft magnetic powder is prepared. The soft magnetic powder may be produced by any method. Examples of production methods include various atomization methods such as water atomization, gas atomization, and rotary water atomization, as well as reduction, carbonyl, and pulverization. Of these, atomization is preferred. That is, the soft magnetic powder is preferably an atomized powder. Atomized powders are fine, have high sphericity, and are highly efficient to produce. In particular, water-atomized powders and rotary water atomized powders have a thin oxide film on their surface because they are produced by contacting molten metal with water. This oxide film can serve as a base for the insulating coating 3. This results in excellent adhesion between the soft magnetic particles 2 and the insulating coating 3, ultimately resulting in insulator-coated soft magnetic particles 4 with particularly high interparticle insulation. In addition, the fast cooling rate makes it possible to produce soft magnetic powders containing amorphous or microcrystalline structures.

[0065] When commercially available soft magnetic powder is procured, this step can be omitted.

[0066] 2.2. Insulating film formation process In the insulating coating forming step S104, an insulating coating 3 is formed to cover the surface of the soft magnetic particles 2. In this way, an insulator-coated soft magnetic powder 1 is obtained.

[0067] The method for forming the insulating coating 3 is not particularly limited, but examples thereof include dry forming methods such as a mechanochemical method, a plasma polymerization method, an ALD (Atomic Layer Deposition) method, a CVD (Chemical Vapor Deposition) method, and an ion plating method, and wet forming methods such as a sol-gel method and an electrolytic reduction method.

[0068] The mechanochemical method, plasma polymerization method, and sol-gel method will be described below as representative methods in this order.

[0069] 2.2.1. Mechanochemical method The mechanochemical method applies mechanical stress to particles to change their physicochemical properties. For example, a mechanochemical reactor having a high-speed rotating cylindrical chamber equipped with a compression tool and blades inside can be used to generate a mechanical interaction (mechanochemical reaction) between soft magnetic particles 2 and the raw material for the insulating coating 3, thereby forming an insulating coating 3 on the surface of the soft magnetic particles 2. Therefore, the mechanochemical method is used as a coating film formation method. Specifically, first, the soft magnetic particles 2 and the raw material for the insulating coating 3 are placed in the chamber. Examples of the raw material for the insulating coating 3 include fluorine compound powder and other additives. When the chamber is rotated, these materials collide with each other and are pressed against the inner wall of the chamber. As a result, the raw material for the insulating coating 3 is pressed against the surface of the soft magnetic particles 2, forming a coating. In this way, insulator-coated soft magnetic particles 4 are obtained. Furthermore, by using such a mechanical coating formation method, the insulating coating 3 can be adhered well even when contaminants are attached to the surface of the soft magnetic particles 2, when adhesion is low, or when the surface roughness is small. Furthermore, because the process of forming the insulating coating 3 does not involve high temperatures, thermal denaturation of the soft magnetic particles 2, such as unintended crystal coarsening, can be suppressed. This makes it possible to suppress a decrease in the soft magnetic properties of the soft magnetic particles 2.

[0070] Furthermore, as mentioned above, fluorine compounds have a lower Young's modulus than other resin materials or inorganic materials, so by using the mechanochemical method, it is possible to efficiently form a thin insulating coating 3 with a high coverage.

[0071] Examples of mechanochemical reaction devices include the "Nobilta" (registered trademark) pulverizer and the "Mechanofusion" (registered trademark) pulverizer manufactured by Hosokawa Micron Corporation, and the "Hybridizer" (registered trademark) pulverizer manufactured by Nara Machinery Works, Ltd.

[0072] The average particle size of the fluorine compound powder is not particularly limited, but is preferably 0.2 to 5.0 times the average particle size of the soft magnetic powder, more preferably 0.5 to 2.0 times, and even more preferably 0.7 to 1.5 times, which allows the soft magnetic powder and the fluorine compound powder to be mixed more uniformly, thereby making it possible to achieve a uniform thickness for the insulating coating 3.

[0073] The average particle size of the fluorine compound powder is preferably 0.1 μm or more and 100 μm or less, more preferably 3 μm or more and 50 μm or less, and even more preferably 5 μm or more and 10 μm or less.

[0074] The average particle size of the fluorine compound powder is the particle size at which the cumulative frequency from the small diameter side is 50% in the particle size distribution on a volume basis obtained by laser diffraction.

[0075] The amount of raw material for the insulating coating 3 added is adjusted appropriately depending on the film thickness of the insulating coating 3 to be formed. As an example, the amount of raw material for the insulating coating 3 added is preferably 0.1% by mass or more of the soft magnetic powder, and more preferably 0.4% by mass or more. Note that even if the amount of raw material for the insulating coating 3 is large, the amount of raw material that adheres to the surfaces of the soft magnetic particles 2 is limited, so no upper limit need be set. However, when taking into consideration the reliable transmission of mixing energy to the surfaces of the soft magnetic particles 2, the amount of raw material for the insulating coating 3 added is preferably 3.0% by mass or less of the soft magnetic powder, and more preferably 1.0% by mass or less.

[0076] As described above, the method for producing an insulator-coated soft magnetic powder according to this embodiment includes an insulating coating formation step S104 that utilizes a mechanochemical reaction. In the insulating coating formation step S104 of this embodiment, the soft magnetic powder is mixed with a fluorine compound powder composed of a fluorine compound, and the fluorine compound powder is mechanically adhered to the particle surfaces of the soft magnetic powder (surfaces of the soft magnetic particles 2). This forms an insulating coating 3 that coats the particle surfaces of the soft magnetic powder, producing an insulator-coated soft magnetic powder 1. The average particle size of the insulator-coated soft magnetic powder 1 is 1 μm or more and 15 μm or less, the average thickness of the insulating coating 3 is 5 nm or more and 50 nm or less, and the relative dielectric constant of the fluorine compound is 5.0 or less.

[0077] This production method utilizes a mechanochemical reaction, and therefore the insulating coating 3 can be adhered well even when contaminants are attached to the surface of the soft magnetic particles 2, when adhesion is low, or when the surface roughness is small. Furthermore, because the process of forming the insulating coating 3 does not involve high temperatures, thermal denaturation of the soft magnetic particles 2, such as unintended crystal coarsening, can be suppressed. Therefore, this production method can efficiently produce an insulator-coated soft magnetic powder 1 that can suppress eddy current loss in the high-frequency range of a magnetic element and improve magnetic properties such as magnetic permeability.

[0078] 2.2.2. Plasma polymerization method The plasma polymerization method is a method in which a plasma discharge is generated in a state where a monomer gas is introduced, and a polymer is deposited on the surface of the object to be treated, thereby forming a coating.

[0079] The monomer gas is a fluorine-containing gas, such as CHF3 gas, C4F8 gas, or C4F 10 Gas, Fluorinert (registered trademark), etc. Fluorinert, for example, 12 , C6F 14 , C7F 16 In addition, when Fluorinert is in liquid form, it is used after being gasified.

[0080] An additive gas (crosslinking gas) that acts as a crosslinking agent may also be used. The crosslinking gas bridges between monomers during the plasma polymerization process. Therefore, the crosslinking gas is preferably added when the molecular weight of the monomer gas is high. By adding the crosslinking gas, even when the movement of the monomer gas is slow and the probability of reaction occurring at the active site is low, this can be compensated for and plasma polymerization can be promoted. Examples of the crosslinking gas include fluoroalkane gases with three or less carbon atoms. Specific examples include CF4 gas, C2F5 gas, and C3F8 gas.

[0081] When a gas having a double bond in the molecule, such as C4F8 gas, is used as the monomer gas, or when the activity of the monomer gas is high, the addition of the cross-linking gas may be omitted. Furthermore, examples of the discharge gas include rare gases such as He and Ar, and nitrogen gas.

[0082] Examples of additive gases used in the polymerization reaction include hydrocarbon gases such as methane, ethane, propane, and butane, as well as halogens, oxygen, hydrogen, NF3, SF6, and CF4.

[0083] Components other than the monomer gas may be added as needed, or may be omitted.

[0084] These gases are introduced into the chamber of a plasma polymerization device, and plasma discharge is generated, causing the monomer gas to reach the surface of the soft magnetic particles 2, which are the object to be treated. Then, active species contained in the plasma cause a polymerization reaction in the monomer gas, and an insulating coating 3 is formed.

[0085] The driving force for causing the polymerization reaction of the monomer gas is not limited to plasma discharge and may be, for example, ultraviolet radiation, but plasma discharge is preferable from the viewpoint of being able to form a dense insulating coating 3. The dense insulating coating 3 is hard and therefore difficult to break even if it is thin, which further improves the insulating properties of the insulating coating 3.

[0086] As described above, the method for producing an insulator-coated soft magnetic powder according to this embodiment includes an insulating coating formation step S104 using plasma polymerization. In the insulating coating formation step S104 of this embodiment, a fluorine-containing gas is polymerized with a monomer gas to form an insulating coating 3 containing a fluorine compound that coats the particle surfaces of the soft magnetic powder (surfaces of the soft magnetic particles 2), thereby producing an insulator-coated soft magnetic powder 1. The average particle size of the insulator-coated soft magnetic powder 1 is 1 μm or more and 15 μm or less, the average thickness of the insulating coating 3 is 5 nm or more and 50 nm or less, and the relative dielectric constant of the fluorine compound is 5.0 or less.

[0087] This manufacturing method, which utilizes plasma polymerization, can form a denser and harder insulating coating 3. This allows for a thin insulating coating 3 with excellent insulating properties. Furthermore, since the film can be formed directly on the surface of the soft magnetic particles 2 from a monomer gas, this method is relatively efficient among vapor-phase film-forming methods. Therefore, this manufacturing method can efficiently produce an insulator-coated soft magnetic powder 1 that can suppress eddy current loss in the high-frequency range of a magnetic element and improve magnetic properties such as magnetic permeability.

[0088] 2.2.3. Sol-gel method The sol-gel method is a liquid phase film formation method in which a coating is formed by polymerizing a fluorine compound precursor in a liquid.

[0089] Examples of the fluorine compound precursor include a coupling agent containing a fluorine atom and a metal alkoxide containing a fluorine atom. The metal alkoxide includes silicon alkoxide. Among these, a coupling agent containing a fluorine atom is preferably used because it allows a stable reaction.

[0090] The fluorine atom-containing coupling agent is a compound having a fluorine-containing group and 1 to 3 hydrolyzable groups.

[0091] Examples of the fluorine-containing group include a fluoroalkyl group, a perfluoroalkyl group, a fluoroaryl group, a perfluoroaryl group, etc. Specific examples include the organic groups listed below.

[0092] F(CF2) u - (CF3)2CF(CF2) v - CF3(CF2)2O(CF(CF3)CF2O) w CF(CF3)- F(CF2) u-1 O(CF2)2- CF3(CF2)2O(CF(CF3)CF2) w+1 O(CF2)2-

[0093] In the organic group, u is 1 to 21, v is 0 to 18, and w is 1 to 5. In the organic group, fluorine atoms may be partially substituted with hydrogen atoms or chlorine atoms.

[0094] In addition, linear perfluoroalkyl groups (F(CF2) u In the case of -), u is preferably 4 to 12, more preferably 6 to 10. This can enhance the chemical stability of the coupling agent.

[0095] Examples of the hydrolyzable group include an alkoxy group, an acyloxy group, an aryloxy group, an aminoxy group, an amide group, a ketoxime group, an isocyanate group, a halogen atom, etc. Among these, an alkoxy group is preferably used.

[0096] Examples of the coupling agent include silane coupling agents, titanium coupling agents, aluminum coupling agents, and zirconium coupling agents, with silane coupling agents being particularly preferred.

[0097] Examples of metal alkoxides containing fluorine atoms include trifluoropropyltrimethoxysilane, nonafluorohexyltrimethoxysilane, and heptadecafluorodecatrimethoxysilane.

[0098] The metal alkoxide is preferably monofunctional, difunctional, or trifunctional, and more preferably difunctional or trifunctional, where, for example, bifunctional means that the number of alkoxide groups is 2 moles per mole of the metal alkoxide.

[0099] The fluorine compound precursor and soft magnetic powder are dispersed in a dispersion medium to prepare a dispersion liquid. Examples of the dispersion medium include lower alcohols such as ethanol and methanol, and fluorine-based liquids such as Fluorinert (registered trademark). To achieve uniform dispersion of the fluorine compound precursor, fluorine-based liquids are preferably used. The amount of dispersion medium used per part by mass of the fluorine compound precursor is, for example, about 10 parts by mass or more and 50 parts by mass or less. The amount of the fluorine compound precursor added per part by mass of the soft magnetic powder is, for example, about 0.01 parts by mass or more and 0.1 parts by mass or less.

[0100] Instead of the method of preparing the dispersion, a method of bringing a mixture of a fluorine compound precursor and a dispersion medium into contact with soft magnetic powder may be used.

[0101] Next, the pH of the dispersion is adjusted and then stirred. The pH is adjusted to, for example, about 9 to 13. An alkaline solution such as aqueous ammonia or aqueous sodium hydroxide solution can be used as the pH adjuster. Stirring causes hydrolysis of the hydrolyzable groups of the fluorine compound precursor, converting them into, for example, silanols. The converted silanols react with each other to undergo dehydration condensation, thereby forming the insulating coating 3.

[0102] Ultrasonic waves may be applied before or after mixing the alkaline solution. Such ultrasonic irradiation promotes uniform dispersion of the soft magnetic powder and allows the insulating coating 3 to be formed more uniformly on the particle surfaces. The order in which the alkaline solutions are added is not limited to the above order, and the timing may be different.

[0103] Furthermore, after the insulating coating 3 is formed, the obtained 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.

[0104] As described above, the method for producing an insulator-coated soft magnetic powder according to this embodiment includes an insulating coating formation step S104 using a sol-gel method. In the insulating coating formation step S104 of this embodiment, a fluorine compound precursor containing fluorine atoms is polymerized by the sol-gel method to form an insulating coating 3 containing a fluorine compound that coats the particle surfaces of the soft magnetic powder (surfaces of the soft magnetic particles 2), thereby producing an insulator-coated soft magnetic powder 1. The average particle size of the insulator-coated soft magnetic powder 1 is 1 μm or more and 15 μm or less, the average thickness of the insulating coating 3 is 5 nm or more and 50 nm or less, and the relative dielectric constant of the fluorine compound is 5.0 or less.

[0105] This production method, which utilizes a sol-gel process, can form a high-density insulating coating 3 with a high coverage rate through self-organization of the fluorine compound precursor. This allows for the production of a thin insulating coating 3 with excellent insulating properties. Therefore, this production method can efficiently produce an insulator-coated soft magnetic powder 1 that can suppress eddy current loss in the high-frequency range of a magnetic element and improve magnetic properties such as magnetic permeability.

[0106] 3. Powder cores and magnetic elements Next, the powder magnetic core and the magnetic element according to the embodiment will be described.

[0107] 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.

[0108] 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.

[0109] FIG. 3 is a plan view schematically showing a toroidal type coil component. 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.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] FIG. 4 is a see-through perspective view that schematically shows a closed magnetic circuit type coil component. 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 4.Electronic equipment Next, an electronic device including the magnetic element according to the embodiment will be described with reference to FIGS.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] As described above, such electronic devices include the magnetic element according to the embodiment, which provides the benefits of the magnetic element, which has low eddy current loss in the high frequency range and high magnetic permeability, thereby enabling the electronic devices to be made more compact and with higher performance.

[0131] 5. Mobile Next, a moving body including the magnetic element according to this embodiment will be described with reference to FIG.

[0132] FIG. 8 is a perspective view showing an automobile, which is a moving body equipped with the magnetic element according to the embodiment. 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.

[0133] As described above, such a moving body includes the magnetic element according to the embodiment, which provides the effects of the magnetic element, which has low eddy current loss in the high frequency range and high magnetic permeability, and allows for the improvement of the performance and miniaturization of equipment mounted on the moving body.

[0134] 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.

[0135] 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.

[0136] 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.

[0137] 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]

[0138] Next, specific examples of the present invention will be described. 6. Preparation of insulator-coated soft magnetic powder Example 1 First, the atomic ratio of the composition formula Fe was obtained by water atomization. 73.0 Cr 2.2 Si 11.1 B 10.8 C 2.9 An amorphous alloy soft magnetic powder having the composition represented by the formula was prepared. The obtained soft magnetic powder was then subjected to ozone treatment. Next, the volumetric particle size distribution of the ozone-treated soft magnetic powder was obtained using a laser diffraction / scattering particle size distribution analyzer. The average particle size was then calculated based on the obtained particle size distribution. The calculation results are shown in Table 1.

[0139] Next, an insulating coating of a fluorine compound having an average thickness of 20 nm was formed on the particle surfaces of the soft magnetic powder by the following method, thereby obtaining an insulator-coated soft magnetic powder.

[0140] In the method for forming the insulating coating, first, 300 g of soft magnetic powder and a fluorine compound powder were placed in the chamber of a mechanochemical reactor. The fluorine compound powder used was PTFE Powder L-5 manufactured by Daikin Industries, Ltd. The fluorine compound powder was added at a ratio of 0.76 mass% of the soft magnetic powder. Then, a mechanochemical reaction was induced between the soft magnetic powder and the fluorine compound powder in the mechanochemical reactor. This resulted in the production of an insulator-coated soft magnetic powder. The reaction conditions for the mechanochemical reaction were a rotation speed of 2000 rpm and a reaction time of 5 minutes.

[0141] 6.2. Examples 2 to 8 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 1, except that the production conditions for the insulator-coated soft magnetic powder were changed as shown in Table 1.

[0142] 6.3. Comparative Example 1 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 1, except that glass powder was used instead of the fluorine compound powder.

[0143] 6.4. Comparative Examples 2 to 4 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 1, except that the production conditions for the insulator-coated soft magnetic powder were changed as shown in Table 1.

[0144] Example 9 First, the atomic ratio of the composition formula Fe was obtained by water atomization. 73.0 Cr 2.2 Si 11.1 B 10.8 C 2.9 An amorphous alloy soft magnetic powder having the composition shown in the following was prepared. The volumetric particle size distribution of the obtained soft magnetic powder was obtained using a laser diffraction / scattering particle size distribution analyzer. The average particle size was then calculated based on the obtained particle size distribution. The calculation results are shown in Table 2. Next, the obtained soft magnetic powder was subjected to an ozone treatment.

[0145] Next, 50 mg of trifluoropropyltrimethoxysilane, a fluorine compound precursor, was diluted 10 times by mass with Fluorinert (registered trademark) to prepare a treatment liquid. The resulting treatment liquid was then sprayed onto 50 g of soft magnetic powder to bring it into contact with the powder.

[0146] Next, the soft magnetic powder onto which the treatment liquid had been sprayed was stirred while being heated to 100°C, dried, and then slowly cooled to room temperature by natural cooling. As a result, an insulating coating was formed on the particle surfaces of the soft magnetic powder by the sol-gel method, and an insulator-coated soft magnetic powder was obtained.

[0147] 6.6. Examples 10 and 11 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 9, except that the production conditions for the insulator-coated soft magnetic powder were changed as shown in Table 2.

[0148] The symbols for the fluorine compound precursors shown in Table 2 correspond to the following substance names: A-1: Trifluoropropyltrimethoxysilane A-2: Nonafluorohexyltrimethoxysilane A-3: Heptadecafluorodecatrimethoxysilane

[0149] Example 12 Except for forming an insulating coating on the particle surface of the soft magnetic powder by plasma polymerization, an insulator-coated soft magnetic powder was obtained in the same manner as in Example 1. The raw material monomer gases used were those shown in Table 2. Argon gas was used as the discharge gas.

[0150] 6.8. Comparative Example 5 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 9, except that the amounts of raw materials used were reduced.

[0151] 6.9. Comparative Example 6 An insulator-coated soft magnetic powder was obtained in the same manner as in Example 12, except that the film-forming time by plasma polymerization was reduced.

[0152] 7. Evaluation of insulator-coated soft magnetic powder 7.1. Average thickness of insulating coating The cross section of the particles of the insulator-coated soft magnetic powder of each example and comparative example was observed under an electron microscope. The average thickness of the insulating coating was calculated from the observation results. The calculation results are shown in Tables 1 and 2.

[0153] 7.2. DC insulation voltage The DC dielectric strength voltage of the insulator-coated soft magnetic powders of each Example and Comparative Example was measured at room temperature of 25° C. and relative humidity of 45% by the following method.

[0154] First, 0.15 g of insulator-coated soft magnetic powder was filled into an alumina cylinder with an inner diameter of 8 mm, and brass electrodes were placed on both ends of the cylinder. Next, using a digital force gauge, a force of 20 kgf was applied to the insulator-coated soft magnetic powder with the electrodes on both ends of the cylinder, while a DC voltage of 50 V was applied between the electrodes for 2 seconds, and the electrical resistance between the electrodes was measured with a digital multimeter.

[0155] Next, the DC voltage applied between the electrodes was increased in increments of 50 V, while measuring the electrical resistance between the electrodes each time and checking for the presence or absence of dielectric breakdown. The voltage increase and electrical resistance measurement were repeated until dielectric breakdown occurred. The lowest DC voltage value at which dielectric breakdown occurred was determined. Dielectric breakdown was considered to have occurred when the electrical resistance value reached 1 MΩ or less. This measurement was performed three times, and the average of the measured values ​​was taken as the DC dielectric strength voltage. The obtained DC dielectric strength voltages are shown in Tables 1 and 2. Tables 1 and 2 also show the electrical resistance values ​​when 100 V was applied.

[0156] 7.3. Coverage The insulation coating coverage of each of the insulator-coated soft magnetic powders of the examples and comparative examples was calculated using the method described above. The calculation results are shown in Tables 1 and 2.

[0157] 7.4. Physical properties of insulating coating Tables 1 and 2 show the physical properties (dielectric constant and Young's modulus) of the constituent materials of the insulating coating used in the production of the insulator-coated soft magnetic powder of each Example and Comparative Example.

[0158] [Table 1]

[0159] [Table 2]

[0160] As shown in Tables 1 and 2, the insulator-coated soft magnetic powders of each example and the insulator-coated soft magnetic powders of the comparative examples were found to have similar DC dielectric strength voltages when the thickness and coverage of the insulating coating were similar. In other words, it was found that the insulating coating formed using a fluorine compound had the same level of insulation properties as insulating coatings formed using conventional glass materials.

[0161] On the other hand, fluorine compounds have a relative dielectric constant of approximately 1 / 3 or less that of glass materials. Therefore, it can be said that the insulator-coated soft magnetic powders of each example are particularly able to suppress the generation of interparticle eddy currents in the high frequency range compared to the insulator-coated soft magnetic powders of the comparative examples.

[0162] Furthermore, the Young's modulus of fluorine compounds is approximately 1 / 100 or less of that of glass materials. Therefore, the insulator-coated soft magnetic powders of each example can be said to be more likely to increase the packing density of soft magnetic particles during compaction and to improve the magnetic properties of magnetic elements than the insulator-coated soft magnetic powders of the comparative examples.

[0163] Therefore, it has become clear that the present invention can provide an insulator-coated soft magnetic powder that suppresses eddy current loss in the high frequency range and allows for the production of magnetic elements with high magnetic permeability. [Explanation of symbols]

[0164] 1...insulating material coated soft magnetic powder, 2...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...preparation step, S104...insulating coating formation step

Claims

1. soft magnetic powder; The particle surfaces of the soft magnetic powder are coated with a fluorine compound such as PTFE or PFA. an insulating coating; Equipped with The soft magnetic powder has an average particle size of 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The insulator-coated soft magnetic powder is characterized in that the relative dielectric constant of the fluorine compound is 5.0 or less. End.

2. 2. The insulating-coated soft magnetic material according to claim 1, wherein the surface of the insulating coating is subjected to a hydrophilic treatment. powder.

3. 3. The insulating material according to claim 1, wherein the fluorine compound has a Young's modulus of 3.0 GPa or less. Edge coated soft magnetic powder.

4. 4. The insulating film according to claim 1, wherein the insulating film has a coverage of 40% or more. Edge coated soft magnetic powder.

5. A soft magnetic powder is mixed with a fluorine compound powder composed of a fluorine compound, and the soft magnetic powder is The fluorine compound powder is mechanically attached to the surface of the powder particles, thereby forming the soft magnetic powder. and forming an insulating coating on the surface of the powder particles to produce an insulator-coated soft magnetic powder. 、 The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The insulator-coated soft magnetic powder is characterized in that the relative dielectric constant of the fluorine compound is 5.0 or less. The manufacturing method of the end.

6. By causing a polymerization reaction between fluorine-containing gas and monomer gas, a fluorine-containing compound is produced. and forming an insulating coating that covers the particle surface of the soft magnetic powder to produce an insulator-coated soft magnetic powder. The method includes the steps of: The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The insulator-coated soft magnetic powder is characterized in that the relative dielectric constant of the fluorine compound is 5.0 or less. The manufacturing method of the end.

7. Fluorine-containing fluorine compound precursors are polymerized by the sol-gel method to form fluorine-containing The soft magnetic powder contains an insulating coating containing an elemental compound, and the insulating coating coats the surface of the soft magnetic powder particles. producing a powder, The average particle size of the insulator-coated soft magnetic powder is 1 μm or more and 15 μm or less, The average thickness of the insulating coating is 5 nm or more and 50 nm or less, The insulator-coated soft magnetic powder is characterized in that the relative dielectric constant of the fluorine compound is 5.0 or less. The manufacturing method of the end.

8. A magnetic material comprising the insulator-coated soft magnetic powder according to any one of claims 1 to 4. Powder magnetic core.

9. A magnetic element comprising the powder magnetic core according to claim 8.

10. An electronic device comprising the magnetic element according to claim 9.

11. A moving body comprising the magnetic element according to claim 9.

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