Insulator-coated soft magnetic powder, dust core, magnetic element and electronic device

Abstract

To provide an insulator-coated soft magnetic powder that can be used to produce a green compact having high density, high insulation properties, and high mechanical strength, a powder core that includes the insulator-coated soft magnetic powder, a magnetic element that includes the powder core, and an electronic device that includes the magnetic element.SOLUTION: An insulator-coated soft magnetic powder includes a soft magnetic powder and an insulating coating that coats the particle surfaces of the soft magnetic powder, and the soft magnetic powder has an average particle size of 2.0 μm or more and 40.0 μm or less, a specific surface area of 10% or more and 100% or less of the specific surface area of the soft magnetic powder alone, and when epoxy resin is mixed in an amount of 2.0 mass % and the powder is molded at a pressure of 294.2 MPa (3.0 t / cm2), the radial crushing strength of the resulting first molded body is 10 MPa or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a soft magnetic material that includes first soft magnetic particles and second soft magnetic particles having a larger average particle size, the first soft magnetic particles having on their surfaces nonpolar hydrocarbon groups or hydrocarbon groups with a linear chain portion having six or more carbon atoms. In such a soft magnetic material, the interaction between the first soft magnetic particles and the binder that binds the soft magnetic material can be reduced, improving the fluidity of the soft magnetic particles during pressure molding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-095629 Summary of the Invention [Problem to be solved by the invention]

[0004] The soft magnetic particles described in Patent Document 1 incorporate nonpolar hydrocarbon groups or hydrocarbon groups with a linear chain containing six or more carbon atoms, thereby reducing interaction with the binder and improving fluidity during compaction. Magnetic elements using soft magnetic powders require low iron loss, and as part of this effort, the diameter of soft magnetic particles is being reduced. Reducing the diameter of soft magnetic particles increases their specific surface area, necessitating the use of a larger amount of binder during compaction. However, increasing the amount of binder used reduces the relative space factor of the soft magnetic particles. As a result, the density of the compact decreases and the magnetic properties deteriorate. On the other hand, reducing the amount of binder used reduces the insulation and mechanical strength of the compact.

[0005] Therefore, the realization of an insulator-coated soft magnetic powder that can be used to produce a green compact having high density, high insulation properties, and high mechanical strength has become an issue. [Means for solving the problem]

[0006] The insulator-coated soft magnetic powder according to the application example of the present invention is soft magnetic powder; an insulating coating that coats the particle surfaces of the soft magnetic powder; Equipped with The soft magnetic powder has an average particle size of 2.0 μm or more and 40.0 μm or less, The specific surface area is 10% or more and 100% or less of the specific surface area of ​​the soft magnetic powder alone, The epoxy resin was mixed to a ratio of 2.0 mass%, and the pressure was 294.2 MPa (3.0 t / cm 2 When the first compact is compacted under a pressure of 10 MPa or more, the radial crushing strength of the resulting first compact is 10 MPa or more.

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

[0008] The magnetic element according to the application example of the present invention includes: The dust core according to the application example of the present invention is provided.

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

[0010] [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] FIG. 2 is a process diagram illustrating a method for producing an insulator-coated soft magnetic powder. [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] 1 is a perspective view showing a mobile personal computer as an electronic device according to an embodiment. [Figure 6] FIG. 1 is a plan view showing a smartphone as an electronic device according to an embodiment. [Figure 7] 1 is a perspective view showing a digital still camera as an electronic device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The insulator-coated soft magnetic powder, dust core, magnetic element, and electronic device of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

[0012] 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."

[0013] 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."

[0014] The soft magnetic powder has an average particle size of 2.0 μm or more and 40.0 μm or less. The insulator-coated soft magnetic powder 1 has a specific surface area of ​​10% or more and 100% or less of the specific surface area of ​​the soft magnetic powder alone. The insulator-coated soft magnetic powder 1 is mixed with an epoxy resin at a ratio of 2.0 mass % and has a viscosity of 294.2 MPa (3.0 t / cm). 2 When the first compact is compacted under a pressure of 10 MPa or more, the radial crushing strength of the resulting first compact is 10 MPa or more.

[0015] According to this configuration, the insulator-coated soft magnetic powder 1 is configured so that the specific surface area is kept small and the compact obtained by compacting under predetermined conditions has sufficiently high radial crushing strength. Therefore, the compact obtained by compacting the insulator-coated soft magnetic powder 1 has high insulation properties, as well as high green density and high mechanical strength.

[0016] 1.1. Soft magnetic powder 1.1.1. Composition of soft magnetic materials The soft magnetic particles 2 are made of 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 properties. 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 mentioned above, including, for example, O, N, S, Na, Mg, and K.

[0017] 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.

[0018] By using a soft magnetic material with such a composition, an insulator-coated soft magnetic powder 1 having high magnetic properties such as magnetic permeability and magnetic flux density and low coercive force can be obtained.

[0019] 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 powder 1, such as magnetic permeability and magnetic flux density.

[0020] 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, the soft magnetic material preferably contains an amorphous alloy composed of an amorphous structure or a nanocrystalline alloy composed of a nanocrystalline structure. By including these, the coercive force is reduced, contributing to the reduction of hysteresis loss of the magnetic element. Note that the soft magnetic material may contain a mixture of structures with different crystallinity.

[0021] Examples of amorphous alloy materials and nanocrystalline alloy 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.

[0022] The soft magnetic particles 2 are preferably made of an amorphous alloy material having the following composition formula: This allows the soft magnetic particles 2 to have both high magnetic permeability and low coercive force.

[0023] Composition formula (Fe 1-x Cr x ) a (Si 1-y B y ) 100-a-b C b [In the above formula, x, y, a, and b satisfy 0 < x ≤ 0.06, 0.3 ≤ y ≤ 0.7, 70.0 ≤ a ≤ 81.0, and 0 < b ≤ 3.0.]

[0024] The above compositional formula represents the ratio in terms of the number of atoms in a composition consisting of five elements: Fe, Cr, Si, B, and C.

[0025] Fe (iron) has a great influence on the basic magnetic properties and mechanical properties of the soft magnetic particles 2. The content of Fe is not particularly limited, but in the soft magnetic particles 2, Fe is set as the main component, that is, the ratio of the number of atoms is the highest. In the soft magnetic particles 2, the content of Fe is preferably 70.0 atomic % or more and 78.0 atomic % or less, more preferably 71.0 atomic % or more and 77.0 atomic % or less, and even more preferably 72.0 atomic % or more and 75.0 atomic % or less.

[0026] Cr (chromium) acts to improve the corrosion resistance of the soft magnetic particles 2. By improving the corrosion resistance, the oxidation of the particles can be suppressed, and the decrease in magnetic properties associated with oxidation can be inhibited. In addition, the passive film also contributes to enhancing the insulation of the particles and suppressing the eddy current loss of the magnetic element.

[0027] x represents the ratio of the content of Cr to the total content when the sum of the content of Fe and the content of Cr is set to 1. In the soft magnetic particles 2, preferably 0 < x ≤ 0.06, more preferably 0.01 ≤ x ≤ 0.05, and even more preferably 0.02 ≤ x ≤ 0.04.

[0028] a represents the ratio of the total content of Fe and the content of Cr, preferably 70.0 ≤ a ≤ 81.0, more preferably 73.0 ≤ a ≤ 80.0, and even more preferably 75.0 ≤ a ≤ 77.0.

[0029] Si (silicon) promotes amorphization and increases the magnetic permeability of the soft magnetic particles 2 when the soft magnetic particles 2 are manufactured from raw materials. Thereby, it is possible to achieve high magnetic permeability and low coercive force.

[0030] When producing the soft magnetic particles 2 from raw materials, B (boron) promotes amorphization. In particular, by using Si and B in combination, synergistic promotion of amorphization can be achieved based on the difference in atomic radii between the two. Thereby, high magnetic permeability and low coercive force can be sufficiently achieved.

[0031] y represents the ratio of the content of B to the total content of Si and B when the total content of Si and B is set to 1. In the soft magnetic particles 2, preferably 0.3 ≤ y ≤ 0.7, more preferably 0.4 ≤ y ≤ 0.6.

[0032] The content rate of Si is preferably 8.0 atomic % or more and 13.5 atomic % or less, more preferably 10.5 atomic % or more and 12.0 atomic % or less.

[0033] The content rate of B is preferably 8.0 atomic % or more and 13.5 atomic % or less, more preferably 10.5 atomic % or more and 12.0 atomic % or less.

[0034] When melting the raw materials of the soft magnetic particles 2, C (carbon) lowers the viscosity of the melt and facilitates amorphization and pulverization. As a result, soft magnetic particles 2 with a small diameter and high magnetic permeability can be obtained. Consequently, eddy current loss can be suppressed even in the high-frequency range.

[0035] b represents the content rate of C. In the soft magnetic particles 2, preferably 0 < b ≤ 3.0, more preferably 1.0 ≤ b ≤ 2.8, still more preferably 1.5 ≤ b ≤ 2.5.

[0036] The composition of the soft magnetic material is specified by the following analysis 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 1.1.2.Particle size distribution 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 2.0 μm or more and 40.0 μm or less, preferably 8.0 μm or more and 35.0 μm or less, and more preferably 15.0 μm or more and 30.0 μm or less.

[0041] If the average particle size of the soft magnetic powder is within the above range, the particle size distribution is optimized, resulting in an insulator-coated soft magnetic powder 1 that has particularly good fluidity and can be used to produce high-density green compacts. Furthermore, since the specific surface area can be kept relatively small, the amount of binder (binding material) used during green compaction can be reduced. This increases the space factor of the soft magnetic powder in the green compact, resulting in a green compact with excellent magnetic properties.

[0042] 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 the packing property during compaction is reduced, making the density of the compacted body likely to decrease. On the other hand, if the average particle size of the soft magnetic powder is above the upper limit, the surface area is reduced, reducing the adhesive force between particles and making the mechanical strength of the compacted body likely to decrease. Furthermore, the manufacturing of the soft magnetic powder becomes more difficult and the manufacturing efficiency decreases.

[0043] The particle size distribution of the soft magnetic powder on a volume basis can be obtained using, for example, a laser diffraction particle size distribution measuring device.

[0044] 1.2.Insulating Coating The insulating coating 3 covers the surface of the soft magnetic particles 2. The insulating coating 3 shown in Fig. 1 is preferably made of an inorganic material, and more preferably contains an inorganic oxide. This allows sufficient insulation to be obtained even when the insulating coating 3 is thin.

[0045] 1.2.1.Insulation Coating Materials Examples of constituent components of inorganic materials include inorganic oxides and inorganic non-oxides.

[0046] Examples of inorganic oxides include silicon oxide such as SiO, magnesium oxide such as MgO, calcium oxide such as CaO, aluminum oxide such as AlO, titanium oxide such as SiO, zirconium oxide such as ZrO, boron oxide such as BO, yttrium oxide such as YO, phosphorus oxide such as PO, bismuth oxide such as BiO, zinc oxide such as ZnO, tin oxide such as SnO, lead oxide such as PbO, lithium oxide such as LiO, sodium oxide such as NaO, potassium oxide such as KO, strontium oxide such as SrO, barium oxide such as BaO, gadolinium oxide such as GdO, lanthanum oxide such as LaO, and ytterbium oxide such as YbO. Note that these compositional formulas are merely examples showing the compositional ratios of the compounds, and the compounds may have compositional ratios other than those described above.

[0047] Examples of inorganic non-oxides include silicon nitride such as Si3N4, aluminum nitride such as AlN, boron nitride such as BN, titanium nitride such as TiN, and tungsten nitride such as WN.

[0048] Among these, the insulating coating 3 preferably contains an inorganic oxide, and more preferably contains silicon oxide or aluminum oxide. These have particularly good insulating properties and chemical stability, and are easily available. This allows the insulating coating 3 to have good insulating properties over a long period of time.

[0049] The insulating coating 3 may contain components other than those described above. The content of the above components in the insulating coating 3 is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. This provides the insulating coating 3 with particularly good insulating properties.

[0050] The surface of the insulating coating 3 may be treated with a coupling agent or the like, if necessary.

[0051] 1.2.2.Average Thickness The average thickness of the insulating coating 3 is preferably 1 nm or more and 100 nm or less, more preferably 5 nm or more and 70 nm or less, and even more preferably 10 nm or more and 50 nm or less. When the average thickness of the insulating coating 3 is within this range, the insulating properties of the insulating coating 3 can be sufficiently ensured, while the space factor of the insulating coating 3 in the powder core can be reduced and the packing rate of the soft magnetic particles 2 can be increased. Furthermore, if the surfaces of the soft magnetic particles 2 are uneven, the insulating coating 3 will smooth out the unevenness and also contribute to making the particles more spherical. This further improves the fluidity of the insulator-coated soft magnetic powder 1.

[0052] 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 and the irregularities on the surfaces of the soft magnetic particles 2 may not be sufficiently smoothed. On the other hand, if the average thickness of the insulating coating 3 exceeds the upper limit, the insulating coating 3 may be prone to peeling and the space factor of the soft magnetic particles 2 in the green compact may decrease.

[0053] 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 insulator-coated soft magnetic particle 4. The measured values ​​are then averaged, and this calculation result is used as the average thickness of the insulating coating 3. The distribution range of the insulating coating 3 in the observation image can be more clearly confirmed by, for example, combining EDX analysis (energy dispersive X-ray analysis), Auger electron spectroscopy, or the like.

[0054] 1.2.3.Oxygen content derived from insulating coating The oxygen content derived from the insulating coating 3 is preferably 500 ppm or more and 7000 ppm or less, more preferably 700 ppm or more and 5000 ppm or less, and even more preferably 900 ppm or more and 3000 ppm or less, by mass ratio. When the oxygen content derived from the insulating coating 3 is within this range, the insulating properties of the insulating coating 3 can be particularly enhanced. Therefore, even if the insulating coating 3 is thin, the insulation between particles is excellent, and insulator-coated soft magnetic particles 4 can be obtained from which a green compact having, for example, excellent voltage resistance can be produced. Furthermore, when the oxygen content derived from the insulating coating 3 is within the above range, the adhesion of the insulating coating 3 to the soft magnetic particles 2 is enhanced, and a green compact having, for example, excellent mechanical strength can be produced.

[0055] If the oxygen content falls below the lower limit, the insulating properties of the insulating coating 3 and its adhesion to the soft magnetic particles 2 may be reduced. On the other hand, if the oxygen content exceeds the upper limit, the space factor of the insulating coating 3 increases, which may result in reduced magnetic properties in the powder compact, for example.

[0056] The oxygen content derived from the insulating coating 3 is calculated by subtracting the oxygen content derived from the soft magnetic particles 2 from the oxygen content of the insulator-coated soft magnetic powder 1. Each oxygen content is measured, for example, in accordance with the general rules for oxygen determination in metallic materials specified in JIS Z 2613:2006. Specifically, the measurement can be performed using a LECO oxygen / nitrogen analyzer, TC-300 / EF-300, or a LECO oxygen / nitrogen / hydrogen analyzer, ONH836, or the like.

[0057] The oxygen content derived from the soft magnetic particles 2 can also be obtained by removing the insulating coating 3 from the insulator-coated soft magnetic powder 1 by a removal method such as ion sputtering, and then measuring it by the above-mentioned measurement method.

[0058] 1.3.Characteristics of insulator-coated soft magnetic powder Next, the characteristics of the insulator-coated soft magnetic powder 1 will be described.

[0059] 1.3.1.Specific surface area When the specific surface area of ​​the insulator-coated soft magnetic powder 1 is the specific surface area of ​​the portion of the insulator-coated soft magnetic powder 1 excluding the insulating coating 3, i.e., the specific surface area of ​​the soft magnetic powder alone, is used as the standard, the ratio to this standard is set within the following range. Hereinafter, this ratio will be referred to as the "specific surface area ratio."

[0060] The specific surface area ratio of the insulator-coated soft magnetic powder 1 is 10% or more and 100% or less. It is also preferably 15% or more and 80% or less, and more preferably 20% or more and 60% or less. When the specific surface area ratio of the insulator-coated soft magnetic powder 1 is within the above range, it is confirmed that the formation of the insulating coating 3 evenly fills in the surface irregularities of the soft magnetic particles 2. Therefore, even when the particle size of the soft magnetic powder is small, an insulator-coated soft magnetic powder 1 with excellent fluidity and packing properties can be obtained. This insulator-coated soft magnetic powder 1 can realize a compact with high density and a reduced binder content. This compact has high density, high insulation properties, and high mechanical strength.

[0061] If the ratio of specific surface areas is below the lower limit, the insulating coating 3 needs to have a sufficient thickness, which increases the space factor of the insulating coating 3 in the green compact. Also, the contact area between the insulator-coated soft magnetic powder 1 and the binder decreases, which reduces the mechanical strength of the green compact. On the other hand, if the ratio of specific surface areas is above the upper limit, the packing ability of the insulator-coated soft magnetic powder 1 during compaction decreases, which reduces the density, mechanical strength, magnetic properties, etc. of the green compact.

[0062] The specific surface area of ​​the insulator-coated soft magnetic powder 1 is preferably 0.010 [m 2 / g] or more 0.600[m 2 / g] or less, more preferably 0.015 [m 2 / g] or more 0.300[m 2 / g] or less, and more preferably 0.020 [m 2 / g] or more 0.100[m 2 / g] or less. If the specific surface area is within this range, aggregation due to surface energy is suppressed, and therefore the packing property of the insulator-coated soft magnetic powder 1 during compaction is improved. Furthermore, if the specific surface area is within this range, the occupancy rate of the insulating coating 3 in the compact can be optimized. As a result, the density and mechanical strength of the compact can be increased, and a decrease in the magnetic permeability of the compact can be suppressed.

[0063] If the specific surface area is below the lower limit, the contact area between the insulator-coated soft magnetic powder 1 and the binder decreases, which may result in a decrease in the mechanical strength of the green compact. On the other hand, if the specific surface area is above the upper limit, the packing property during compaction may decrease, which may result in a decrease in the density, mechanical strength, magnetic properties, etc. of the green compact.

[0064] The specific surface area of ​​the insulator-coated soft magnetic powder 1 and the specific surface area of ​​the soft magnetic powder are each obtained by the BET method. An example of an apparatus for measuring the specific surface area is the BET-type specific surface area measuring apparatus HM1201-010 manufactured by Mountech Co., Ltd., and the amount of sample is 5 g.

[0065] 1.3.2. Radial crushing strength The insulator-coated soft magnetic powder 1 has a first compact obtained by compacting under predetermined conditions, and the radial crushing strength of the first compact is 10 MPa or more. The radial crushing strength is preferably 10 MPa or more and 55 MPa or less, more preferably 15 MPa or more and 45 MPa or less, and even more preferably 20 MPa or more and 35 MPa or less. The insulator-coated soft magnetic powder 1 that achieves such a radial crushing strength contributes to the realization of a dust core (compressed powder) having good mechanical strength.

[0066] If the radial crushing strength is below the lower limit, defects such as chipping or cracking may occur when the powder magnetic core is subjected to a load such as a strong impact. On the other hand, the radial crushing strength may exceed the upper limit, but in that case, there is a risk of large variations in the mechanical strength of the powder magnetic core.

[0067] The radial crushing strength was measured as follows. First, the insulator-coated soft magnetic powder 1 is mixed with 2.0 mass % of epoxy resin relative to the mass of the powder, dried at 50°C for 1 hour, and then crushed to obtain a granulated powder. Next, the obtained granulated powder is subjected to a pressure of 294.2 MPa (3 t / cm 2 ), and then heated at 150°C for 3 hours to harden the epoxy resin. This produces a first molded body. The first molded body has a ring-shaped shape with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. Next, the radial crushing strength of the obtained first molded body is measured. The method for measuring the radial crushing strength is a method that conforms to the radial crushing strength test method specified in JIS Z 2507:2000. Specifically, when the radial crushing strength is K, the outer diameter is D, the radial thickness (half the difference between the outer diameter and the inner diameter) is t, the thickness is L, and the breaking load is F, the radial crushing strength K is calculated as follows: K=F(Dt) / (Lt 2 ) can be calculated using

[0068] 1.3.3. Density of the compact The density of the first compact obtained as described above was 4.40 [g / cm 3 ] or more than 5.00[g / cm 3 ] or less, and 4.50 [g / cm 3 ] or more than 4.95[g / cm 3 ] or less, and more preferably 4.60 [g / cm 3 ] or more than 4.90[g / cm 3 If the density of the first compact is within the above range, an insulator-coated soft magnetic powder 1 that can be used to produce a high-density powder magnetic core can be realized. Such a powder magnetic core can then be used to realize a magnetic element with high magnetic properties.

[0069] The density of the first compact can be determined by dividing the mass of the first compact obtained as described above by the volume.

[0070] 1.3.4.Dielectric Strength The insulator-coated soft magnetic powder 1 has a second compact formed under predetermined conditions with a withstand voltage of preferably 200 V / mm or more, more preferably 200 V / mm or more and 4000 V / mm or less, even more preferably 300 V / mm or more and 3000 V / mm or less, and particularly preferably 400 V / mm or more and 2000 V / mm or less. The insulator-coated soft magnetic powder 1 that achieves such withstand voltage contributes to the realization of magnetic elements that are small but have a high rated voltage.

[0071] If the withstand voltage is below the lower limit, the rated voltage of the magnetic element may not be increased sufficiently. On the other hand, the withstand voltage may be above the upper limit, but in that case, the withstand voltage of the magnetic element may vary greatly.

[0072] The method for measuring the withstand voltage is as follows. First, the insulator-coated soft magnetic powder 1 is mixed with 2.0 mass % of epoxy resin relative to the mass of the powder, dried at 50°C for 1 hour, and then crushed to obtain a granulated powder. Next, the obtained granulated powder is subjected to a pressure of 49.0 MPa (0.5 t / cm 2 ) to form a cylindrical shape with a height of 5 mm, and then heat it at 150°C for 30 minutes to harden the epoxy resin. This produces a second molded body. During the press molding process, copper electrodes with a thickness of 1 mm are embedded on the top and bottom of the cylinder.

[0073] Next, each electrode is connected to a power supply and a DC voltage is applied between the electrodes. The electrical resistance between the electrodes is measured with a digital multimeter while the voltage is increased in 50V increments. The voltage at which the electrical resistance falls below 1MΩ is taken as the breakdown voltage. For example, if the electrical resistance falls below 1MΩ at a voltage of 550V, the breakdown voltage is taken as 500V.

[0074] Next, the breakdown voltage is divided by the distance between the electrodes to determine the withstand voltage. For example, if the breakdown voltage is 500 V and the distance between the electrodes is 3 mm, the withstand voltage is 167 V / mm.

[0075] 2. Manufacturing method of insulator-coated soft magnetic powder Next, an example of a method for producing the insulator-coated soft magnetic powder 1 will be described.

[0076] FIG. 2 is a process diagram illustrating a method for producing the insulator-coated soft magnetic powder 1. As shown in FIG. 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.

[0077] 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 an insulator-coated soft magnetic powder 1 with particularly high interparticle insulation. In addition, the fast cooling rate makes it possible to produce soft magnetic powders containing amorphous or nanocrystalline structures.

[0078] The water atomization method is a method for producing metal powder by spraying cooling water in an inverted cone shape and passing molten metal through the water atomization. The water atomization method can efficiently produce soft magnetic powder with a relatively small particle size.

[0079] The rotary water atomization method is a method for producing metal powder by rotating cooling water along the inner surface of a vessel and bringing finely divided molten metal into contact with the water. The rotary water atomization method can efficiently produce soft magnetic powder with a relatively large particle size.

[0080] 2.2. Insulating film formation process In the insulating coating formation step S104, the insulating coating 3 that covers the surface of the soft magnetic particles 2 is formed.

[0081] The method for forming the insulating coating 3 is not particularly limited, but examples thereof include a mechanochemical method, a vapor phase film formation method, and a liquid phase film formation method.

[0082] Examples of vapor phase film formation methods include plasma polymerization, ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), and ion plating. Examples of the liquid phase film forming method include a sol-gel method and an electrolytic reduction method.

[0083] The mechanochemical method and the sol-gel method will be described below as representative methods. 2.2.1. Mechanochemical method The mechanochemical method applies mechanical stress to ceramic particles to change their physicochemical properties. For example, a mechanochemical reactor with a high-speed rotating cylindrical chamber equipped with internal compression tools and blades is used to induce a mechanical interaction (mechanochemical reaction) between soft magnetic particles 2 and inorganic material particles, forming an insulating coating 3 made of an inorganic material on the surface of the soft magnetic particles 2. This mechanical coating formation method ensures good adhesion of the insulating coating 3 even when contaminants are present on the surface of the soft magnetic particles 2 or when adhesion is low. Furthermore, because the insulating coating 3 is formed without high temperatures, thermal denaturation of the soft magnetic particles 2, such as unintended crystal coarsening, can be suppressed. This prevents a decrease in the soft magnetic properties of the soft magnetic particles 2.

[0084] 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.

[0085] 2.2.2. Sol-gel method The sol-gel method is a method for producing an inorganic oxide by hydrolysis of a metal alkoxide. For example, when forming a silicon oxide film to serve as the insulating coating 3, the hydrolysis reaction of silicon alkoxide can be utilized. The method using silicon alkoxide will be described below.

[0086] First, the soft magnetic particles 2 are dispersed in an alcohol solution containing silicon alkoxide. Examples of the alcohol solution include lower alcohols such as ethanol and methanol. For example, 1 part by mass of tetraethoxysilane can be mixed with 10 parts by mass to 50 parts by mass of alcohol.

[0087] Next, ammonia water is added as a catalyst to promote the reaction, causing hydrolysis. This causes a dehydration condensation reaction between the hydrolyzates and between the hydrolyzates and the silicon alkoxide, forming -Si-O-Si- bonds on the particle surface. This results in the formation of an insulating coating 3 made of silicon oxide. The insulating coating 3 may then be heated as needed.

[0088] 3. Powder cores and magnetic elements Next, the powder magnetic core and the magnetic element according to the embodiment will be described.

[0089] 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.

[0090] Two types of coil components will be described below as representative examples of magnetic elements. 3.1.Toroidal type First, a toroidal type coil component will be described as an example of a magnetic element according to the embodiment. FIG. 3 is a plan view schematically showing the toroidal type coil component 10. As shown in FIG.

[0091] 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.

[0092] The powder magnetic core 11 is obtained by mixing the insulator-coated soft magnetic powder 1 according to the embodiment with a binder and compacting the resulting mixture. Because the powder magnetic core 11 is a compact containing the insulator-coated soft magnetic powder 1 according to the embodiment, it is possible to realize a coil component 10 that achieves both magnetic properties, insulation properties, and mechanical strength. Therefore, when the coil component 10 is installed in an electronic device or the like, it is possible to improve the performance and miniaturize the electronic device or the like.

[0093] Examples of binder materials used in producing the powder magnetic core 11 include organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, thermosetting polyimide resins, and polyphenylene sulfide resins, as well as 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 resins and epoxy resins are particularly preferred. These resin materials are easily cured by heating and have excellent heat resistance. This improves the ease of production and heat resistance of the powder magnetic core 11.

[0094] The ratio of binder to insulator-coated soft magnetic powder 1 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 0.3 to 5.0 mass%, more preferably about 0.5 to 3.0 mass%, and even more preferably about 0.7 to 2.0 mass%. This allows the particles of the insulator-coated soft magnetic powder 1 to be sufficiently bound together, and allows for the production of coil components 10 with excellent magnetic properties. If necessary, various additives may be added to the mixture for any purpose.

[0095] Examples of materials constituting the conductor 12 include highly conductive materials, such as metal materials containing Cu, Al, Ag, Au, Ni, etc. Furthermore, an insulating film may be provided on the surface of the conductor 12 as needed.

[0096] 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.

[0097] The powder magnetic core 11 may contain soft magnetic powder other than the insulator-coated soft magnetic powder 1 according to the embodiment described above, or non-magnetic powder, as needed.

[0098] 3.2.Closed magnetic circuit type Next, a closed magnetic circuit type coil component, which is an example of a magnetic element according to the embodiment, will be described. FIG. 4 is a see-through perspective view that schematically shows a coil component 20 of a closed magnetic circuit type.

[0099] The closed magnetic circuit type coil component 20 will be described below, but the following description will focus on the differences from the toroidal type coil component 10, and a description of similar points will be omitted.

[0100] 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 above-described insulator-coated soft magnetic powder 1, 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 above-described powder magnetic core 11. This makes it possible to realize a coil component 20 with high magnetic properties, insulation properties, and mechanical strength.

[0101] Furthermore, the coil component 20 having such a configuration can be made relatively small. Therefore, when the coil component 20 is mounted in an electronic device or the like, the electronic device or the like can be made smaller and with higher performance.

[0102] 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.

[0103] 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.

[0104] Furthermore, the powder magnetic core 21 may contain soft magnetic powders other than the insulator-coated soft magnetic powder 1 according to the embodiment described above, or non-magnetic powders, as needed.

[0105] 4.Electronic equipment Next, an electronic device including the magnetic element according to the embodiment will be described with reference to FIGS.

[0106] Fig. 5 is a perspective view showing a mobile personal computer 1100, which is an electronic device according to an embodiment. The personal computer 1100 shown in Fig. 5 includes a main body 1104 having a keyboard 1102, and a display unit 1106 having 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.

[0107] Fig. 6 is a plan view showing a smartphone 1200, which is an electronic device according to an 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 built-in magnetic element 1000, such as an inductor, a noise filter, or a motor.

[0108] 7 is a perspective view showing an electronic device according to an embodiment, namely, a digital still camera 1300. 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.

[0109] 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.

[0110] 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.

[0111] Examples of electronic devices according to the embodiments include a personal computer 1100 in FIG. 5, a smartphone 1200 in FIG. 6, and a digital still camera 1300 in 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.

[0112] As described above, such electronic devices include the magnetic element according to the embodiment, thereby enjoying the effects of the magnetic element according to the embodiment, which achieves both magnetic properties, insulating properties, and mechanical strength, and enabling the electronic devices to be made more compact and with higher performance.

[0113] 5. Effects of the above embodiment As described above, the insulator-coated soft magnetic powder 1 according to the embodiment includes soft magnetic powder and an insulating coating 3. The insulating coating 3 coats the surfaces of the soft magnetic particles 2 (particle surfaces of the soft magnetic powder). The soft magnetic powder has an average particle size of 2.0 μm or more and 40.0 μm or less. The insulator-coated soft magnetic powder 1 has a specific surface area of ​​10% or more and 100% or less of the specific surface area of ​​the soft magnetic powder alone. The insulator-coated soft magnetic powder 1 is mixed with an epoxy resin at a ratio of 2.0 mass %, and has a viscosity of 294.2 MPa (3.0 t / cm). 2 When the first compact is compacted under a pressure of 10 MPa or more, the radial crushing strength of the resulting first compact is 10 MPa or more.

[0114] According to this configuration, an insulator-coated soft magnetic powder 1 is obtained that can be used to produce a green compact having high density, high insulation properties, and high mechanical strength.

[0115] In the insulator-coated soft magnetic powder 1 according to the embodiment, the insulating coating 3 contains an inorganic oxide.

[0116] With this configuration, the insulating coating 3 can have good insulating properties for a long period of time because inorganic oxides have particularly good insulating properties and chemical stability.

[0117] In addition, in the insulator-coated soft magnetic powder 1 according to the embodiment, the epoxy resin is mixed to a ratio of 2.0 mass % and the compressive strength is 49.0 MPa (0.5 t / cm 2 When the second compact is molded under a pressure of 1000 V / mm or more, the resulting second compact has a withstand voltage of 200 V / mm or more.

[0118] With this configuration, it is possible to obtain the insulator-coated soft magnetic powder 1 that contributes to realizing a magnetic element that is small but has a high rated voltage.

[0119] Also, in the insulating-coated soft magnetic powder 1 according to the above embodiment, the specific surface area is 0.010 [m 2 / g] or more and 0.600 [m 2 / g] or less.

[0120] According to such a configuration, aggregation due to surface energy is suppressed, so that the filling property during powder pressing of the insulating-coated soft magnetic powder 1 is improved. Also, if the specific surface area is within the above range, the occupancy rate of the insulating film 3 in the compact can be optimized. As a result, an insulating-coated soft magnetic powder 1 capable of increasing the density and mechanical strength of the compact and suppressing a decrease in the magnetic permeability of the compact can be obtained.

[0121] Also, in the insulating-coated soft magnetic powder 1 according to the above embodiment, the soft magnetic particles 2 (particles of the soft magnetic powder) are composed of an amorphous alloy material having a composition represented by the composition formula (Fe[[ID=十六]] 1-x [[ID=十七]]Cr[[ID=十八]] x [[ID=十九]])[[ID=二十]] a [[ID=二十一]](Si[[ID=二十二]] 1-y [[ID=二十三]]B[[ID=二十四]] y [[ID=二十五]])[[ID=二十六]] 100-a-b [[ID=二十七]]C[[ID=二十八]] b [[ID=二十九]][where x, y, a, and b are such that 0 < x ≤ 0.06, 0.3 ≤ y ≤ 0.7, 70.0 ≤ a ≤ 81.0, and 0 < b ≤ 3.0]. [[ID=三十]] [[ID=三十一]]

[0122] [[ID=三十二]] [[ID=三十三]]According to such a configuration, soft magnetic particles 2 having both high magnetic permeability and low coercive force can be obtained. [[ID=三十四]] [[ID=三十五]]

[0123] [[ID=三十六]] [[ID=三十七]]Also, in the insulating-coated soft magnetic powder 1 according to the above embodiment, the density of the first compact is 4.40 [g / cm[[ID=三十八]] 3 [[ID=三十九]]] or more and 5.00 [g / cm[[ID=四十]] 3 [[ID=四十一]]] or less. [[ID=四十二]] [[ID=四十三]]

[0124] [[ID=四十四]] [[ID=四十五]]According to such a configuration, an insulating-coated soft magnetic powder 1 capable of manufacturing a high-density powder compact magnetic core can be realized. And according to such a powder compact magnetic core, a magnetic element having high magnetic characteristics can be realized. [[ID=四十六]] [[ID=四十七]]

[0125] [[ID=四十八]] In addition, in the insulator-coated soft magnetic powder 1 according to the embodiment, the amount of oxygen derived from the insulating coating 3 is 500 ppm or more and 7000 ppm or less by mass ratio.

[0126] This configuration particularly enhances the insulating properties of the insulating coating 3. Therefore, even if the insulating coating 3 is thin, the insulating-material-coated soft magnetic powder 1 has excellent insulation between particles, and can be used to produce a green compact with excellent voltage resistance, for example. Furthermore, if the oxygen content derived from the insulating coating 3 is within the above range, the insulating coating 3 adheres well to the soft magnetic particles 2, and a green compact with excellent mechanical strength, for example, can be produced.

[0127] In addition, in the insulator-coated soft magnetic powder 1 according to the embodiment, the average thickness of the insulating coating 3 is 1 nm or more and 100 nm or less.

[0128] With this configuration, it is possible to reduce the space factor of the insulating coating 3 in the powder core and increase the packing factor of the soft magnetic particles 2 while ensuring sufficient insulation of the insulating coating 3. Furthermore, if the surfaces of the soft magnetic particles 2 are uneven, the insulating coating 3 evens out and smooths the unevenness, and also contributes to making the particles more spherical. This further improves the fluidity of the insulator-coated soft magnetic powder 1.

[0129] The powder magnetic core according to the embodiment includes the insulator-coated soft magnetic powder according to the embodiment, thereby obtaining a powder magnetic core that can realize a magnetic element that achieves both magnetic properties, insulation properties, and mechanical strength.

[0130] Furthermore, the magnetic element according to the embodiment includes the powder magnetic core according to the embodiment, thereby obtaining a magnetic element that achieves both magnetic properties, insulation properties, and mechanical strength.

[0131] Furthermore, the electronic device according to the embodiment includes the magnetic element according to the embodiment, thereby providing an electronic device with high performance and miniaturization.

[0132] The insulator-coated soft magnetic powder, dust core, magnetic element, and electronic device of the present invention have been described above based on preferred embodiments, but the present invention is not limited to these.

[0133] For example, in the above embodiment, a dust 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 dust core and the magnetic element are not limited to those shown in the drawings and may be any shape.

[0134] Furthermore, the powder magnetic core and magnetic element according to the present invention may be configured by adding any desired components to the above-described embodiments. [Example]

[0135] Next, specific examples of the present invention will be described. 6. Preparation of insulator-coated soft magnetic powder First, soft magnetic powders having the compositions shown in Table 1 were prepared by rotary water atomization or water atomization. The manufacturing methods and average particle sizes of the soft magnetic powders are shown in Table 2.

[0136] Next, an insulating coating was formed on the surface of the soft magnetic powder particles. The method of forming the insulating coating, the constituent materials, the film thickness (average thickness), and the oxygen content are as shown in Table 2. In this manner, the insulator-coated soft magnetic powders of the respective sample numbers shown in Table 2 were obtained.

[0137] The specific surface area and radial crushing strength of the obtained insulator-coated soft magnetic powder were then measured. Furthermore, the "specific surface area ratio" was calculated based on the specific surface area of ​​the soft magnetic powder before the insulating coating was formed. The measurement and calculation results are shown in Table 2.

[0138] [Table 1]

[0139] The composition 1 shown in Table 1 is the composition formula (Fe 1-x Cr x ) a (Si 1-y B y ) 100-a-b C b The composition is [x=0.03, y=0.5, a=76.0, b=2.0].

[0140] In Table 2 shown later, among the insulator-coated soft magnetic powders of each sample number, those corresponding to the present invention are designated as "Examples," and those not corresponding to the present invention are designated as "Comparative Examples."

[0141] 7. Evaluation of insulator-coated soft magnetic powder 7.1. Relative density of compact First, the insulator-coated soft magnetic powder of each Example and Comparative Example was mixed with 2.0 mass % of epoxy resin and toluene relative to the mass of the powder, and the resulting mixture was dried at 50°C for 1 hour and then crushed to obtain a granulated powder. Next, the resulting granulated powder was crushed under a pressure of 294.2 MPa (3 t / cm 2 ) and then heated at 150°C for 3 hours to harden the epoxy resin. This yields a green body. The green body has a ring-like shape with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. The mass of the green body obtained was then divided by the volume to calculate the density. The density obtained was then divided by the true density of the insulator-coated soft magnetic powder to calculate the relative density. The calculated relative density was then evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.

[0142] A: Relative density is 67% or more B: Relative density is 63% or more and less than 67% C: Relative density is less than 63%

[0143] 7.2. Magnetic permeability of compact First, a compact similar to that in 7.1 was prepared for each of the insulator-coated soft magnetic powders of each Example and Comparative Example. Next, the magnetic permeability of the prepared compact was measured. The magnetic permeability of the compact is the relative magnetic permeability, i.e., effective magnetic permeability, determined from the self-inductance of a closed magnetic circuit core coil prepared using the aforementioned compact. The magnetic permeability was measured using an impedance analyzer at a measurement frequency of 100 kHz. The number of turns of the winding was 7, and the wire diameter of the winding was 0.6 mm.

[0144] The measured magnetic permeability was then evaluated in accordance with the following evaluation criteria. The evaluation results are shown in Table 2. Note that the reference values ​​in the following evaluation criteria are values ​​set for each soft magnetic material, and the reference value for Samples Nos. 1 to 5 and 8 to 12 is Sample No. 7. The reference value for Sample No. 6 is Sample No. 13. The reference value for Sample No. 14 is Sample No. 15. The reference value for Samples Nos. 16, 17, and 19 is Sample No. 18.

[0145] A: The measured permeability is 105% or more of the standard value. B: The measured permeability is 100% or more but less than 105% of the standard value. C: The measured permeability is less than 100% of the reference value.

[0146] 7.3.Voltage resistance The withstand voltage of the insulator-coated soft magnetic powders of each Example and Comparative Example was measured by the method described above. The evaluation results are shown in Table 2.

[0147] [Table 2]

[0148] As shown in Table 2, it was found that the insulator-coated soft magnetic powders of each Example were capable of producing a compact having high density and high insulation properties compared to the insulator-coated soft magnetic powders of each Comparative Example. This confirms that the use of the insulator-coated soft magnetic powders of each Example makes it possible to realize a dust core having high mechanical strength, magnetic properties, and a high withstand voltage. [Explanation of symbols]

[0149] 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, S102...preparation step, S104...inorganic insulating film forming step

Claims

1. soft magnetic powder; an insulating coating that coats the particle surfaces of the soft magnetic powder; Equipped with The soft magnetic powder has an average particle size of 2.0 μm or more and 40.0 μm or less, a specific surface area of ​​the soft magnetic powder is 10% or more and 100% or less of the specific surface area of ​​the soft magnetic powder alone; The epoxy resin was mixed to a ratio of 2.0 mass%, and the pressure was 294.2 MPa (3.0 t / cm ２ 2. An insulator-coated soft magnetic powder, characterized in that when the powder is compacted under a pressure of 10 MPa or more, the radial crushing strength of the resulting first compact is 10 MPa or more.

2. The insulator-coated soft magnetic powder according to claim 1 , wherein the insulating coating contains an inorganic oxide.

3. The epoxy resin was mixed to a ratio of 2.0 mass%, and the pressure was 49.0 MPa (0.5 t / cm ２ 3. The insulator-coated soft magnetic powder according to claim 1, wherein when the second compact is compacted under a pressure of 1000 V / mm or more, the withstand voltage of the resulting second compact is 200 V / mm or more.

4. The specific surface area is 0.010 [m ２ / g] or more 0.600[m ２ 3. The insulator-coated soft magnetic powder according to claim 1, wherein the powder has a surface roughness of 0.1 μm or less.

5. The particles are Composition formula expressed by atomic ratio (Fe １－ｘ Cr ｘ ) ａ (Si １－ｙ B ｙ ) １００－ａ－ｂ C ｂ [where x, y, a and b are 0<x≦0.06, 0.3≦y≦0.7, 70.0≦a≦81.0, 0<b≦3.0.] 3. The insulator-coated soft magnetic powder according to claim 1, which is composed of an amorphous alloy material having the following composition:

6. The density of the first compact is 4.40 [g / cm ３ ] or more 5.00 [g / cm ３ 6. The insulator-coated soft magnetic powder according to claim 5, wherein the average particle diameter is 100 nm or less.

7. 3. The insulator-coated soft magnetic powder according to claim 1, wherein the amount of oxygen derived from the insulating coating is 500 ppm or more and 7000 ppm or less by mass ratio.

8. 3. The insulator-coated soft magnetic powder according to claim 1, wherein the average thickness of the insulating coating is 1 nm or more and 100 nm or less.

9. A dust core comprising the insulator-coated soft magnetic powder according to claim 1 or 2.

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

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

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