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

Abstract

Provided are an insulator-coated soft magnetic powder capable of producing a powder compact having high density, high insulativity, and high mechanical strength, a powder magnetic core containing the insulator-coated soft magnetic powder, a magnetic element provided with the powder magnetic core, and an electronic device provided with the powder magnetic core. The electronic equipment is provided with the magnetic element. A soft magnetic powder coated with an insulating material, which is provided with a soft magnetic powder and an insulating coating film that covers the particle surface of the soft magnetic powder, and which is characterized in that: the soft magnetic powder has an average particle diameter of 2.0-40.0 [mu] m and a specific surface area of 10-100% of the specific surface area of the soft magnetic powder monomer; when the epoxy resin is mixed in such a manner that the ratio of the epoxy resin is 2.0 mass% and the mixture is molded at a pressure of 294.2 MPa, i.e., 3.0 t / cm2, the compression ring strength of the obtained first molded body is 10 MPa or more.

Description

Technical Field

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

[0002] Patent Document 1 discloses a soft magnetic material comprising first soft magnetic particles and second soft magnetic particles having an average particle size larger than the first soft magnetic particles. The first soft magnetic particles are particles having nonpolar hydrocarbon groups or hydrocarbon groups having linear chains with 6 or more carbon atoms on their surfaces. 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, thereby improving the fluidity of the soft magnetic particles during press molding.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2021-095629

[0004] In the soft magnetic particles described in Patent Document 1, by introducing a non-polar hydrocarbon group or a hydrocarbon group having a straight chain portion with more than 6 carbon atoms, the interaction with the binder is reduced and the fluidity during press molding is improved. In magnetic elements using soft magnetic powder, low iron loss is required, and as a part of this, the size reduction of soft magnetic particles is continuously developing. When the soft magnetic particles are reduced in size, the specific surface area becomes larger, so it is necessary to increase the amount of binder used during press molding. However, if the amount of binder used is increased, the space factor of the soft magnetic particles is relatively reduced. As a result, the density of the powder compact is reduced and the magnetic properties are reduced. On the other hand, if the amount of binder used is reduced, the insulation and mechanical strength of the powder compact are reduced.

[0005] Therefore, it has become a technical problem to realize an insulator-coated soft magnetic powder capable of producing a green compact having high density, high insulation and high mechanical strength. Summary of the Invention

[0006] An insulator-coated soft magnetic powder according to an application example of the present invention includes:

[0007] soft magnetic powder; and

[0008] an insulating film covering the surface of the particles of the soft magnetic powder,

[0009] The average particle size of the soft magnetic powder is 2.0 μm or more and 40.0 μm or less.

[0010] The specific surface area of ​​the soft magnetic powder covered by the insulating material is not less than 10% and not more than 100% of the specific surface area of ​​the soft magnetic powder alone.

[0011] The epoxy resin was mixed so as to be 2.0% by mass and the pressure was 294.2 MPa (3.0 t / cm2 When the pressure is formed, the compression ring strength of the obtained first molded body is greater than 10 MPa.

[0012] The powder magnetic core according to the application example of the present invention,

[0013] The invention also includes the insulator-coated soft magnetic powder according to an application example of the present invention.

[0014] The magnetic element according to the application example of the present invention,

[0015] A powder magnetic core according to an application example of the present invention is provided.

[0016] The electronic device involved in the application example of the present invention is:

[0017] A magnetic element according to an application example of the present invention is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a cross-sectional view schematically showing one particle of the insulator-coated soft magnetic powder according to the embodiment.

[0019] Figure 2 This is a process diagram for explaining a method for producing insulator-coated soft magnetic powder.

[0020] Figure 3 It is a plan view schematically showing a ring-shaped coil component.

[0021] Figure 4 It is a perspective view schematically showing a closed magnetic circuit type coil component.

[0022] Figure 5 It is a perspective view showing a mobile personal computer as an electronic device according to an embodiment.

[0023] Figure 6 It is a plan view showing a smartphone as the electronic device according to the embodiment.

[0024] Figure 7 It is a perspective view showing a digital still camera as an electronic device according to an embodiment.

[0025] Description of Reference Numerals

[0026] 1: Insulator covering soft magnetic powder; 2: Soft magnetic particles; 3: Insulator coating; 4: Insulator covering soft magnetic particles; 10: Coil component; 11: Pressed powder core; 12: Wire; 20: Coil component; 21: Pressed powder core; 22: Wire; 100: Display unit; 1000: Magnetic element; 1100: Personal computer; 1102: Keyboard; 1104: Main body; 1106: Display unit; 1200: Smart phone; 1202: Operation button; 1204: Earpiece; 1206: Microphone; 1300: Digital still camera; 1302: Housing; 1304: Light receiving unit; 1306: Shutter button; 1308: Memory; S102: Preparation process; S104: Inorganic insulating film forming process. DETAILED DESCRIPTION

[0027] Hereinafter, the insulator-coated soft magnetic powder, the powder magnetic core, the magnetic element, and the electronic device of the present invention will be described in detail based on preferred embodiments shown in the drawings.

[0028] 1. Insulation covered with soft magnetic powder

[0029] First, the insulator-coated soft magnetic powder according to the embodiment will be described. Figure 1 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 is also referred to as "insulator-coated soft magnetic particle 4".

[0030] Figure 1 The insulator-covered soft magnetic particles 4 shown have soft magnetic particles 2 and an insulating coating 3 arranged on the surface of the soft magnetic particles 2. Wherein, the soft magnetic particles 2 contain a soft magnetic material described later. The insulating coating 3 is arranged in a manner covering the surface of the soft magnetic particles 2 and has insulating properties. It should be noted that, covering in this specification refers to a concept of a state that also includes a part of the state of covering the surface in addition to the state of the entire surface of the soft magnetic particles 2. In addition, in the following description, the aggregate of the soft magnetic particles 2 is also referred to as "soft magnetic powder".

[0031] The average particle size of the soft magnetic powder is 2.0 μm or more and 40.0 μm or less. In addition, the specific surface area of ​​the insulator-coated soft magnetic powder 1 is 10% or more and 100% or less of the specific surface area of ​​the soft magnetic powder alone. In addition, the insulator-coated soft magnetic powder 1 is mixed with epoxy resin at a ratio of 2.0% by mass and heated at 294.2 MPa (3.0 t / cm 2 When the pressure is formed, the compression ring strength of the obtained first molded body is greater than 10 MPa.

[0032] This structure allows the insulator-coated soft magnetic powder 1 to have a relatively low specific surface area, while also providing a sufficiently high ring strength when formed under specified conditions. Consequently, the powder compact formed by compacting the insulator-coated soft magnetic powder 1 can achieve high insulation properties, a high-voltage powder density, and high mechanical strength.

[0033] 1.1. Soft magnetic powder

[0034] 1.1.1. Composition of soft magnetic materials

[0035] 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 main components, i.e., materials containing 50% or more of these elements in terms of atomic ratio. In addition to containing these main components, the soft magnetic material may also contain at least one selected from the group consisting of Cr, Nb, Cu, Al, Mn, Mo, Si, Sn, B, C, P, Ti, and Zr, depending on the target properties. Furthermore, the soft magnetic material may also contain unavoidable impurities within the scope of not impairing the effects of this embodiment. Unavoidable impurities refer to impurities accidentally mixed into the raw materials or during manufacturing. Unavoidable impurities include all elements other than the above-mentioned elements, and as an example, O, N, S, Na, Mg, K, etc. may be cited.

[0036] Specific examples of soft magnetic materials include, in addition to Fe-Si alloys such as silicon steel and Fe-Si-Al alloys such as aluminum silicon powder, various alloys such as Fe-Ni, Fe-Co, Fe-Ni-Co, Fe-Si-B, Fe-Si-BC, Fe-Si-B-Cr-C, Fe-Si-Cr, Fe-B, Fe-PC, Fe-Co-Si-B, Fe-Si-B-Nb, Fe-Si-B-Nb-Cu, Fe-Zr-B, Fe-Cr, and Fe-Cr-Al alloys, Ni-Si-B, Ni-PB, and other Ni alloys, and Co-Si-B, etc.

[0037] By using the soft magnetic material of such a composition, it is possible to obtain the insulator-coated soft magnetic powder 1 having high magnetic properties such as magnetic permeability and magnetic flux density and low coercive force.

[0038] In the soft magnetic material, the content of the main component is preferably 50% or more, more preferably 70% or more in terms of atomic ratio. This can particularly improve magnetic properties such as magnetic permeability and magnetic flux density of the insulator-coated soft magnetic powder 1.

[0039] The organization that constitutes soft magnetic material is not particularly limited, can be any in crystalline structure, amorphous (amorphous) organization or microcrystalline (nanocrystalline) organization.Wherein, soft magnetic material preferably comprises the amorphous alloy that is made of amorphous structure or the nanocrystalline alloy that is made of nanocrystalline structure.By containing them, coercive force diminishes, and helps the reduction of the hysteresis loss of magnetic element.It should be noted that, in soft magnetic material, also can be mixed with the organization that crystallinity is different.

[0040] As amorphous alloy materials and nanocrystalline alloy materials, for example, there can be listed Fe-Si-B series, Fe-Si-BC series, Fe-Si-B-Cr-C series, Fe-Si-Cr series, Fe-B series, Fe-PC series, Fe-Co-Si-B series, Fe-Si-B-Nb series, Fe-Si-B-Nb-Cu series, Fe-Zr-B series and other Fe-based alloys, Ni-Si-B series, Ni-PB series and other Ni-based alloys, Co-Si-B series and other Co-based alloys, etc.

[0041] The soft magnetic particles 2 are particularly preferably made of an amorphous alloy material having the following composition formula: Thereby, soft magnetic particles 2 having both high magnetic permeability and low coercive force can be obtained.

[0042] Composition formula (Fe 1-x Cr x ) a (Si 1-y B y ) 100-a-b C b

[0043] [In the above formula, x, y, a, and b are 0 < x ≤ 0.06, 0.3 ≤ y ≤ 0.7, 70.0 ≤ a ≤ 81.0, and 0 < b ≤ 3.0.]

[0044] The above composition formula represents the ratio of the number of atoms in the composition consisting of five elements: Fe, Cr, Si, B, and C.

[0045] Fe (iron) significantly affects the basic magnetic and mechanical properties of the soft magnetic particles 2. The Fe content is not particularly limited, but is set so that Fe is the main component, i.e., the atomic ratio, in the soft magnetic particles 2 is the highest. The Fe content in the soft magnetic particles 2 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.

[0046] Cr (chromium) improves the corrosion resistance of the soft magnetic particles 2. This improved corrosion resistance suppresses oxidation of the particles, which in turn reduces the degradation of magnetic properties associated with oxidation. Furthermore, the passivation film helps improve the insulation properties of the particles, suppressing eddy current losses in the magnetic element.

[0047] x represents the ratio of the Cr content to the total content when the total of the Fe content and the Cr content is 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.

[0048] a represents the ratio of the total content of Fe and the content of Cr, and is preferably 70.0≤a≤81.0, more preferably 73.0≤a≤80.0, and even more preferably 75.0≤a≤77.0.

[0049] Si (silicon) promotes amorphization when producing the soft magnetic particles 2 from a raw material, and increases the magnetic permeability of the soft magnetic particles 2. This can achieve higher magnetic permeability and lower coercive force.

[0050] Boron (B) promotes amorphization when manufacturing soft magnetic particles 2 from raw materials. In particular, the combined use of Si and B can synergistically promote amorphization due to the difference in their atomic radii. This allows for sufficient high permeability and low coercivity.

[0051] y represents the ratio of the B content to the total content, when the total of the Si content and the B content is set to 1. In the soft magnetic particles 2, 0.3≤y≤0.7 is preferred, and 0.4≤y≤0.6 is more preferred.

[0052] The Si content is preferably 8.0 atomic % or more and 13.5 atomic % or less, and more preferably 10.5 atomic % or more and 12.0 atomic % or less.

[0053] The content of B is preferably 8.0 atomic % or more and 13.5 atomic % or less, and more preferably 10.5 atomic % or more and 12.0 atomic % or less.

[0054] When the raw material for the soft magnetic particles 2 is melted, carbon reduces the viscosity of the melt, facilitating amorphization and micronization. This results in soft magnetic particles 2 with small diameters and high magnetic permeability. As a result, eddy current losses can be suppressed even in high-frequency regions.

[0055] b represents the content of C. In the soft magnetic particles 2, preferably 0<b≤3.0, more preferably 1.0≤b≤2.8, and even more preferably 1.5≤b≤2.5.

[0056] The composition of the soft magnetic material is determined by the following analytical method.

[0057] Examples of the analysis method include the atomic absorption spectrometry for iron and steel specified in JIS G 1257:2000, the inductively coupled plasma emission spectrometry for iron and steel specified in JIS G 1258:2007, the spark discharge emission spectrometry for iron and steel specified in JIS G 1253:2002, the fluorescent X-ray analysis for iron and steel specified in JIS G 1256:1997, and the gravimetric titration-absorptiometry specified in JIS G1211 to G1237.

[0058] Specifically, for example, there can be mentioned a solid-state emission spectrometer manufactured by SPECTRO, in particular a spark discharge emission spectrometer, model: SPECTROLAB, type: LAVMB08A, and an inductively coupled plasma analyzer, model CIROS120, manufactured by Rigaku Corporation.

[0059] In particular, when determining C (carbon) and S (sulfur), the oxygen stream combustion (high-frequency induction heating furnace combustion)-infrared absorption method specified in JIS G 1211: 2011 can also be used. Specifically, the CS-200 carbon and sulfur analyzer manufactured by LECO can be used.

[0060] In particular, when determining N (nitrogen) and O (oxygen), the nitrogen quantitative method for iron and steel specified in JIS G 1228:1997 and the oxygen quantitative method for metallic materials specified in JIS Z 2613:2006 can also be used. Specifically, the oxygen and nitrogen analyzer TC-300 / EF-300 manufactured by LECO can be used.

[0061] 1.1.2. Particle size distribution

[0062] In the volume-based particle size distribution of the soft magnetic powder, when the particle size at which the cumulative frequency is 50% is taken as the average particle size, the average particle size of the soft magnetic powder is greater than or equal to 2.0 μm and less than or equal to 40.0 μm, preferably greater than or equal to 8.0 μm and less than or equal to 35.0 μm, and more preferably greater than or equal to 15.0 μm and less than or equal to 30.0 μm.

[0063] When the average particle size of the soft magnetic powder is within this range, the particle size distribution is optimized, resulting in an insulator-coated soft magnetic powder 1 with particularly good flowability and capable of producing a high-density powder compact. Furthermore, since the specific surface area can be kept relatively small, the amount of binder (adhesive material) used during powder compaction can be reduced. This increases the space factor of the soft magnetic powder in the powder compact, resulting in a powder compact with excellent magnetic properties.

[0064] It should be noted that if the average particle size of the soft magnetic powder is below the lower limit, agglomeration is likely to occur, making the formation of the insulating coating 3 difficult. Furthermore, the packing capacity during powder compaction is reduced, and the density of the powder compact is 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 decreases, thereby reducing the bonding force between the particles and the mechanical strength of the powder compact. Furthermore, the production of the soft magnetic powder becomes more difficult and the production efficiency is reduced.

[0065] The volume-based particle size distribution of the soft magnetic powder can be obtained using, for example, a laser diffraction particle size distribution measuring apparatus.

[0066] 1.2. Insulation coating

[0067] The insulating coating 3 covers the surface of the soft magnetic particles 2 . Figure 1 The insulating film 3 shown 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 film 3 is thin.

[0068] 1.2.1. Insulation coating materials

[0069] Examples of the constituent components of the inorganic material include inorganic oxides and inorganic non-oxides.

[0070] Examples of inorganic oxides include silicon oxides such as SiO2, magnesium oxides such as MgO, calcium oxides such as CaO, aluminum oxides such as Al2O3, titanium oxides such as SiO2, zirconium oxides such as ZrO2, boron oxides such as B2O3, yttrium oxides such as Y2O3, phosphorus oxides such as P2O5, bismuth oxides such as Bi2O3, zinc oxides such as ZnO, tin oxides such as SnO, lead oxides such as PbO, lithium oxides such as Li2O, sodium oxides such as Na2O, potassium oxides such as K2O, strontium oxides such as SrO, barium oxides such as BaO, gadolinium oxides such as Gd2O3, lanthanum oxides such as La2O3, and ytterbium oxides such as Yb2O3. It should be noted that these composition formulas are examples of the composition ratios of the compounds, and the compounds may have composition ratios other than those described above.

[0071] Examples of the inorganic non-oxide include silicon nitride such as Si 3 N 4 , aluminum nitride such as AlN, boron nitride such as BN, titanium nitride such as TiN, and tungsten nitride such as WN.

[0072] The insulating film 3 preferably contains an inorganic oxide, more preferably silicon oxide or aluminum oxide. These oxides have particularly good insulation and chemical stability and are readily available. Therefore, an insulating film 3 with excellent long-term insulation properties can be obtained.

[0073] The insulating film 3 may contain components other than those listed above. The content of the above components in the insulating film 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 film 3 with particularly good insulation properties.

[0074] It should be noted that, if necessary, the surface of the insulating coating 3 may be subjected to a coupling agent treatment or the like.

[0075] 1.2.2. Average thickness

[0076] The average thickness of the insulating film 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. If the average thickness of the insulating film 3 is within the range, the insulating properties of the insulating film 3 can be fully ensured, and the space factor of the insulating film 3 in the powder core can be reduced to improve the filling rate of the soft magnetic particles 2. In addition, when there are irregularities on the surface of the soft magnetic particles 2, the insulating film 3 also helps to make the irregularities flat and smooth, and close to a spherical shape. Thus, the fluidity of the insulating material covering the soft magnetic powder 1 can be further improved.

[0077] 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 surface irregularities of the soft magnetic particles 2 may not be sufficiently smoothed. On the other hand, if the average thickness of the insulating coating 3 is above the upper limit, the insulating coating 3 may be easily peeled off, or the space factor of the soft magnetic particles 2 in the powder compact may be reduced.

[0078] It should be noted that the average thickness of the insulating coating 3 is measured, for example, by magnifying and observing the cross section of the insulating material-covered soft magnetic particles 4. Specifically, the insulating material-covered soft magnetic particles 4 are cut by a focused ion beam to prepare a cross-sectional thin-section sample. Next, the obtained cross-sectional thin-section sample is observed using a scanning transmission electron microscope, and the thickness of the insulating coating 3 is measured at more than 5 locations for one insulating material-covered soft magnetic particle 4. Then, the measured values ​​are averaged, and the calculated result is used as the average thickness of the insulating coating 3. The distribution range of the insulating coating 3 in the observed image can be more clearly confirmed, for example, by using EDX analysis (energy dispersive X-ray analysis), Auger electron spectroscopy, etc.

[0079] 1.2.3. Oxygen content from insulation coating

[0080] 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, in terms of mass ratio. If the oxygen content derived from the insulating coating 3 is within the above range, the insulating properties of the insulating coating 3 can be particularly improved. Therefore, even if the insulating coating 3 is relatively thin, excellent insulation between particles can be obtained, and for example, an insulating material-coated soft magnetic particle 4 can be produced, which can produce a powder compact with excellent withstand voltage. In addition, if 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 particle 2 becomes higher, and for example, a powder compact with excellent mechanical strength can be produced.

[0081] It should be noted that if the oxygen content is below the lower limit, the insulation properties of the insulating coating 3 and the adhesion to the soft magnetic particles 2 may be reduced. On the other hand, if the oxygen content is above the upper limit, the space factor of the insulating coating 3 becomes high, and thus, for example, the magnetic properties of the powder compact may be reduced.

[0082] 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 insulating-coated soft magnetic powder 1. Each oxygen content can be measured, for example, in accordance with the general rules for oxygen quantification of metallic materials specified in JIS Z 2613:2006. Specifically, the measurement can be performed using an oxygen / nitrogen analyzer, TC-300 / EF-300, manufactured by LECO, or an oxygen / nitrogen / hydrogen analyzer, ONH836, manufactured by LECO.

[0083] The oxygen content derived from the soft magnetic particles 2 can also be obtained by removing the insulating film 3 from the insulating-covered soft magnetic powder 1 by a removal method such as ion sputtering and then measuring the result by the above-mentioned measurement method.

[0084] 1.3. Characteristics of Insulator-Coated Soft Magnetic Powder

[0085] Next, the characteristics of the insulator-coated soft magnetic powder 1 will be described.

[0086] Specific surface area

[0087] The ratio of the specific surface area of ​​the insulator-covered soft magnetic powder 1 to the specific surface area of ​​the insulator-covered soft magnetic powder 1, excluding the insulating coating 3, is set within the following range, using as a reference the specific surface area of ​​the soft magnetic powder alone. This ratio is hereinafter referred to as the "specific surface area ratio."

[0088] The ratio of the specific surface area of ​​the insulator-coated soft magnetic powder 1 is not less than 10% and not more than 100%. In addition, it is preferably not less than 15% and not more than 80%, and more preferably not less than 20% and not more than 60%. If the ratio of the specific surface area of ​​the insulator-coated soft magnetic powder 1 is within the above range, it is confirmed that the surface irregularities of the soft magnetic particles 2 are uniformly filled by the formation of the insulating coating 3. Therefore, even when the particle size of the soft magnetic powder is small, an insulator-coated soft magnetic powder 1 with excellent fluidity and filling properties can be obtained. By such an insulator-coated soft magnetic powder 1, a high-density powder compact with a suppressed binder content can be achieved. Such a powder compact has high density, high insulation and high mechanical strength.

[0089] It should be noted that if the specific surface area ratio 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 compact. Furthermore, the contact area between the insulator-coated soft magnetic powder 1 and the binder decreases, reducing the mechanical strength of the compact. On the other hand, if the specific surface area ratio exceeds the upper limit, the packing capacity of the insulating-coated soft magnetic powder 1 during compacting decreases, resulting in reduced density, mechanical strength, and magnetic properties of the compact.

[0090] The specific surface area of ​​the insulator-covered soft magnetic powder 1 is preferably 0.010 m 2 / g or above and 0.600m 2 / g or less, more preferably 0.015m 2 / g or more and 0.300m 2 / g or less, more preferably 0.020m 2 / g or more and 0.100m 2 / g or less. When the specific surface area is within this range, aggregation caused by surface energy can be suppressed, thereby improving the packing capacity of the soft magnetic powder 1 when compacted with an insulating material. Furthermore, when 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, while suppressing a decrease in the magnetic permeability of the compact.

[0091] It should be noted that if the specific surface area is below the lower limit, the contact area between the insulating material covering the soft magnetic powder 1 and the binder may be reduced, thereby reducing the mechanical strength of the compact. On the other hand, if the specific surface area is above the upper limit, the packing capacity during powder compaction may be reduced, thereby reducing the density, mechanical strength, magnetic properties, etc. of the compact.

[0092] The specific surface areas of the insulator-coated soft magnetic powder 1 and the soft magnetic powder were measured by the BET method. Specific surface area measurement apparatuses such as the BET specific surface area measurement apparatus HM1201-010 manufactured by Mountech Co., Ltd. were used. The sample weight was 5 g.

[0093] 1.3.2. Press ring strength

[0094] The first compact formed from the insulator-coated soft magnetic powder 1 under specified conditions has a ring strength of 10 MPa or greater. Furthermore, it is preferably 10 MPa to 55 MPa, more preferably 15 MPa to 45 MPa, and even more preferably 20 MPa to 35 MPa. Insulator-coated soft magnetic powder 1 achieving such a ring strength contributes to the realization of a powder core (powder compact) having excellent mechanical strength.

[0095] It should be noted that if the ring strength is below the lower limit, defects such as chips and cracks may occur when a strong impact load is applied to the powder core. On the other hand, the ring strength can be higher than the upper limit, but in this case, the mechanical strength of the powder core may vary greatly.

[0096] It should be noted that the method for measuring the above-mentioned compression ring strength is as follows.

[0097] First, the insulating material-coated soft magnetic powder 1 was mixed with 2.0% by mass of epoxy resin relative to the mass of the powder, dried at 50°C for 1 hour, and then pulverized to obtain granulated powder. The obtained granulated powder was then subjected to a pressure of 294.2 MPa (3 t / cm 2 The first molded body is formed by press molding, and then heated at 150°C for 3 hours to cure the epoxy resin. Thus, a first molded body is obtained. The shape of the first molded body is a ring with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. Next, the compression ring strength of the obtained first molded body is measured. The method for measuring the compression ring strength is based on the compression ring strength test method specified in JIS Z 2507:2000. Specifically, when the compression ring strength is set to K, the outer diameter is set to D, the wall thickness in the radial direction (half the difference between the outer diameter and the inner diameter) is set to t, the thickness is set to L, and the breaking load is set to F, the compression ring strength K can be calculated by K=F(Dt) / (Lt 2 ) to find out.

[0098] 1.3.3. Density of the molded body

[0099] The density of the first molded body obtained as described above is preferably 4.40 g / cm 3 Above and 5.00g / cm 3Below, more preferably 4.50g / cm 3 Above 4.95g / cm 3 Below, more preferably 4.60g / cm 3 Above and 4.90g / cm 3 If the density of the first compact is within the above range, it is possible to manufacture a high-density powder core of the insulator-coated soft magnetic powder 1. In addition, such a powder core can realize a magnetic element with high magnetic properties.

[0100] The density of the first molded body is determined by dividing the mass of the first molded body obtained as described above by its volume.

[0101] 1.3.4 Withstand voltage

[0102] The second molded body formed from the insulator-coated soft magnetic powder 1 under specified conditions preferably has a withstand voltage of 200 V / mm or greater, more preferably 200 V / mm or greater and 4000 V / mm or less, further preferably 300 V / mm or greater and 3000 V / mm or less, and particularly preferably 400 V / mm or greater and 2000 V / mm or less. Insulator-coated soft magnetic powder 1 that achieves such a withstand voltage contributes to the realization of compact magnetic components with high rated voltages.

[0103] It should be noted that if the withstand voltage is lower than the lower limit, the rated voltage of the magnetic element may not be sufficiently increased. On the other hand, the withstand voltage may be higher than the upper limit, but in this case, the variation in the withstand voltage of the magnetic element may become larger.

[0104] It should be noted that the above-mentioned withstand voltage is measured by the following method.

[0105] First, the insulating material-coated soft magnetic powder 1 was mixed with 2.0% by mass of epoxy resin relative to the mass of the powder, dried at 50°C for 1 hour, and then pulverized to obtain granulated powder. The obtained granulated powder was then subjected to a pressure of 49.0 MPa (0.5 t / cm 2 The lower part was press-formed into a 5mm-high cylindrical shape and then heated at 150°C for 30 minutes to cure the epoxy resin. This produced a second molded body. It should be noted that during press-forming, 1mm-thick copper electrodes were embedded in the upper and lower surfaces of the cylinder.

[0106] Next, connect each electrode to a power supply and apply a DC voltage between the electrodes. Then, while increasing the voltage to 50V, measure the resistance between the electrodes with a digital multimeter. The voltage at which the resistance is below 1MΩ is used as the breakdown voltage. For example, if the voltage is 550V and the resistance is below 1MΩ, the breakdown voltage is set to 500V.

[0107] Next, the breakdown voltage is divided by the distance between electrodes to obtain the withstand voltage. For example, when the breakdown voltage is 500 V and the distance between electrodes is 3 mm, the withstand voltage is 167 V / mm.

[0108] 2. Manufacturing method of insulating material covered soft magnetic powder

[0109] Next, an example of a method for producing the insulator-coated soft magnetic powder 1 will be described.

[0110] Figure 2 These are process diagrams for explaining a method for producing the insulator-coated soft magnetic powder 1 .

[0111] Figure 2 The method for producing the insulator-coated soft magnetic powder shown includes a preparation step S102 and an insulation coating forming step S104 .

[0112] 2.1. Preparation process

[0113] In the preparation step S102, soft magnetic powder is prepared. The soft magnetic powder can be a powder produced by any method. Examples of production methods include various atomization methods such as water atomization, gas atomization, and rotating water flow atomization, as well as reduction methods, carbonyl methods, and pulverization methods. Among them, the atomization method is preferably used. That is, the soft magnetic powder is preferably an atomized powder. Atomized powder is small and has high sphericity, and the production efficiency is also high. In addition, water atomized powder or rotating water flow atomized powder is particularly produced by contact between molten metal and water, and therefore has a thin oxide film on the surface. This oxide film can serve as the base of the insulating coating 3. Therefore, the soft magnetic particles 2 and the insulating coating 3 have excellent adhesion, and the insulation between the particles is particularly high, thereby obtaining an insulating material covering the soft magnetic powder 1. In addition, due to the fast cooling rate, it is also possible to produce a soft magnetic powder containing an amorphous structure and a nanocrystalline structure.

[0114] The water atomization method is a method of producing metal powder by spraying cooling water in an inverted conical shape and passing molten metal through it. The water atomization method can efficiently produce soft magnetic powders with a small diameter.

[0115] The swirling water atomization method produces metal powder by swirling cooling water along the inner surface of a container, bringing atomized molten metal into contact with the water. This method allows for the efficient production of soft magnetic powders with larger diameters.

[0116] 2.2. Insulation coating formation process

[0117] In the insulating film forming step S104 , the insulating film 3 is formed to cover the surface of the soft magnetic particles 2 .

[0118] The method for forming the insulating coating 3 is not particularly limited, and examples thereof include a mechanochemical method, a vapor phase film formation method, and a liquid phase film formation method.

[0119] Examples of the vapor phase film formation method include plasma polymerization, ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), and ion plating.

[0120] Examples of the liquid phase film formation method include a sol-gel method and an electrolytic reduction method.

[0121] Hereinafter, the mechanochemical method and the sol-gel method will be described in order as representatives.

[0122] Mechanochemical method

[0123] Mechanochemical method is to apply mechanical stress to ceramic particles, the method that the physicochemical characteristics of ceramic particles are changed.For example, use and possess compression tool and blade inside, have the mechanochemical reaction device of high-speed rotating cylindrical chamber, when producing mechanical interaction (mechanochemical reaction) between soft magnetic particle 2 and inorganic material particle, can form the insulating coating 3 that is made of inorganic material on the surface of soft magnetic particle 2.By using such mechanical coating forming method, even when the surface of soft magnetic particle 2 is attached with the situation of pollutant or when the adhesive force is low, also can make insulating coating 3 adhere well.In addition, owing to not passing through high temperature state in the formation process of insulating coating 3, therefore can suppress the thermal modification of soft magnetic particle 2, for example can suppress undesirable crystallization coarsening.Thus, can suppress the soft magnetic property of soft magnetic particle 2 to reduce.

[0124] Examples of mechanochemical reaction devices include the "Nobilta" (registered trademark) pulverizer and the "Mechanofusion" (registered trademark) pulverizer manufactured by Hosokawa Micron Co., Ltd., and the "HYBRIDIZATION" (registered trademark) pulverizer manufactured by Nara Machinery Co., Ltd.

[0125] Sol-gel method

[0126] The sol-gel method is a method for producing inorganic oxides by hydrolyzing metal alkoxides. For example, when forming a silicon oxide film to form the insulating coating 3, the hydrolysis reaction of silicon alkoxides can be utilized. The method using silicon alkoxides is described below.

[0127] 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, 10 to 50 parts by mass of alcohol may be mixed with 1 part by mass of tetraethoxysilane.

[0128] Next, aqueous ammonia is added as a catalyst to promote the reaction, causing hydrolysis. This causes a dehydration condensation reaction between the hydrolyzed products and the silicon alkoxide, forming -Si-O-Si- bonds on the particle surfaces. This forms an insulating film 3 composed of silicon oxide. The insulating film 3 can then be heated as needed.

[0129] 3.Powder cores and magnetic components

[0130] Next, the dust core and the magnetic element according to the embodiment will be described.

[0131] The magnetic components according to the embodiments can be applied to various magnetic components including magnetic cores, such as choke coils, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the powder magnetic cores according to the embodiments can be applied to the magnetic cores of these magnetic components.

[0132] Hereinafter, two types of coil components will be described as representative examples of magnetic elements.

[0133] 3.1. Ring type

[0134] First, a ring-shaped coil component as an example of a magnetic element according to the embodiment will be described.

[0135] Figure 3 It is a plan view schematically showing the ring-shaped coil component 10 .

[0136] Figure 3 The coil component 10 shown includes a ring-shaped powder magnetic core 11 and a conductive wire 12 wound around the powder magnetic core 11. Such a coil component 10 is generally called a toroidal coil.

[0137] The dust core 11 is formed by mixing the insulator-coated soft magnetic powder 1 according to the embodiment with a binder and then molding the resulting mixture. Because the dust core 11 is a compact containing the insulator-coated soft magnetic powder 1 according to the embodiment, a coil component 10 having a balanced combination of magnetic properties, insulation, and mechanical strength can be achieved. Therefore, when the coil component 10 is incorporated into electronic equipment, the performance of the electronic equipment can be enhanced while also being miniaturized.

[0138] Examples of materials constituting the binder used in manufacturing the dust core 11 include organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, thermosetting 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 resins and epoxy resins are particularly preferred. These resin materials are easily cured by heating and have excellent heat resistance. Therefore, the dust core 11 can be easily manufactured and its heat resistance improved.

[0139] The ratio of the binder to the insulator-coated soft magnetic powder 1 varies slightly depending on the target magnetic and mechanical properties, the permissible eddy current loss, and other factors of the powder core 11 to be produced, but is preferably between approximately 0.3% and 5.0% by mass, more preferably between approximately 0.5% and 3.0% by mass, and even more preferably between approximately 0.7% and 2.0% by mass. This allows the particles of the insulator-coated soft magnetic powder 1 to be sufficiently bonded to each other, resulting in a coil component 10 having excellent magnetic properties.

[0140] Various additives may be added to the mixture for any purpose as needed.

[0141] Examples of the material constituting the conductive wire 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 conductive wire 12 as necessary.

[0142] The shape of the powder core 11 is not limited to Figure 3 The ring shape shown may be, for example, a shape in which a portion of the ring is missing, a shape in which the longitudinal direction is linear, a sheet shape, a film shape, or the like.

[0143] The powder core 11 may contain soft magnetic powder and non-magnetic powder other than the insulator-coated soft magnetic powder 1 according to the above-described embodiment, as needed.

[0144] 3.2 Closed magnetic circuit type

[0145] Next, a closed magnetic circuit type coil component will be described as an example of the magnetic element according to the embodiment.

[0146] Figure 4 It is a transparent perspective view schematically showing a closed magnetic circuit type coil component 20 .

[0147] The closed magnetic circuit type coil component 20 will be described below. However, the following description will focus on differences from the ring type coil component 10 , and descriptions of the same matters will be omitted.

[0148] like Figure 4 As shown, the coil component 20 of this embodiment is formed by embedding a coiled conductive wire 22 within a powder core 21. Specifically, the coil component 20, serving as a magnetic element, comprises a powder core 21 containing the aforementioned insulator-coated soft magnetic powder 1, with the conductive wire 22 molded around the powder core 21. This powder core 21 has the same structure as the aforementioned powder core 11. This allows for a coil component 20 with superior magnetic properties, insulation, and mechanical strength.

[0149] Furthermore, the coil component 20 of this embodiment can be relatively easily miniaturized. Therefore, when the coil component 20 is mounted on an electronic device or the like, the electronic device or the like can achieve higher performance and smaller size.

[0150] Furthermore, since the conductive wire 22 is embedded in the dust core 21, a gap is unlikely to form between the conductive wire 22 and the dust core 21. This suppresses vibration caused by magnetostriction of the dust core 21 and the generation of noise associated with the vibration.

[0151] It should be noted that the shape of the powder core 21 is not limited to Figure 4 The shape shown may also be a sheet, a film, etc.

[0152] Furthermore, the powder core 21 may contain soft magnetic powder and non-magnetic powder other than the insulator-coated soft magnetic powder 1 according to the above-described embodiment, as needed.

[0153] 4. Electronic devices

[0154] Then, based on Figures 5 to 7 An electronic device including the magnetic element according to the embodiment will be described.

[0155] Figure 5 It is a perspective view showing a mobile personal computer 1100 as an electronic device according to the embodiment. Figure 5 The illustrated personal computer 1100 includes a main body 1104 with a keyboard 1102 and a display unit 1106 with 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 incorporates, for example, a choke coil for a switching power supply, an inductor, and a magnetic component 1000 such as a motor.

[0156] Figure 6 It is a plan view showing a smartphone 1200 as an electronic device according to the embodiment. Figure 6The smartphone 1200 shown includes a plurality of operation buttons 1202, an earpiece 1204, and a microphone 1206. The display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 includes built-in magnetic components 1000 such as an inductor, a noise filter, and a motor.

[0157] Figure 7 1 is a perspective view showing a digital still camera 1300 as an electronic device according to an embodiment. The digital still camera 1300 generates an imaging signal by photoelectrically converting a light image of a subject using an imaging element such as a CCD (Charge Coupled Device).

[0158] Figure 7 The digital still camera 1300 shown includes a display unit 100 disposed on the back of a housing 1302. The display unit 100 functions as a viewfinder that displays an electronic image of a subject. Furthermore, a light receiving unit 1304, which includes an optical lens and a CCD, is disposed on the front side of the housing 1302, i.e., the back side in the figure.

[0159] When the photographer checks the subject image displayed on the display unit 100 and presses the shutter button 1306, the imaging signal of the CCD at that time is transmitted and stored in the memory 1308. Such a digital still camera 1300 also has a built-in magnetic element 1000 such as an inductor element or a noise filter.

[0160] As the electronic device involved in the embodiment, in addition to Figure 5 Personal computer 1100, Figure 6 Smartphone 1200, Figure 7 In addition to the digital still camera 1300, examples thereof include mobile phones, tablet terminals, watches, inkjet printers and other inkjet ejection devices, notebook personal computers, televisions, cameras, video tape recorders, car navigation devices, pagers, electronic notepads, electronic dictionaries, calculators, electronic game consoles, word processors, workstations, videophones, anti-theft TV monitors, electronic binoculars, POS terminals, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic equipment, electronic endoscopes and other medical equipment, fish finders, various measuring equipment, measuring instruments for vehicles, aircraft, and ships, mobile body control equipment such as motor vehicle control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, flight simulators, etc.

[0161] As described above, such an electronic device includes the magnetic element according to the embodiment. Thus, the effects of the magnetic element according to the embodiment, which achieves a balance between magnetic properties, insulation, and mechanical strength, can be enjoyed, thereby achieving higher performance and smaller size of the electronic device.

[0162] 5. Effects of the Implementation Method

[0163] As described above, the insulator-coated soft magnetic powder 1 involved in the embodiment comprises soft magnetic powder and an insulating coating 3. The insulating coating 3 covers the surface of the soft magnetic particles 2 (the particle surface of the soft magnetic powder). In addition, the average particle size of the soft magnetic powder is not less than 2.0 μm and not more than 40.0 μm. In addition, the specific surface area of ​​the insulator-coated soft magnetic powder 1 is not less than 10% and not more than 100% of the specific surface area of ​​the soft magnetic powder alone. In addition, the insulator-coated soft magnetic powder 1 is mixed in such a manner that the epoxy resin reaches a ratio of 2.0 mass %, and the epoxy resin is heated at 294.2 MPa, i.e., 3.0 t / cm 2 When the pressure is formed, the compression ring strength of the obtained first molded body is greater than 10 MPa.

[0164] With such a structure, the insulator-coated soft magnetic powder 1 can be obtained, which can produce a green compact having high density, high insulation properties, and high mechanical strength.

[0165] Furthermore, in the insulator-coated soft magnetic powder 1 according to the above-described embodiment, the insulating coating 3 contains an inorganic oxide.

[0166] With such a structure, since inorganic oxides have particularly excellent insulation properties and chemical stability, an insulating film 3 with excellent long-term insulation properties can be obtained.

[0167] In the insulator-coated soft magnetic powder 1 according to the embodiment, the epoxy resin is mixed at a ratio of 2.0 mass %, and the pressure is 49.0 MPa, i.e., 0.5 t / cm 2 When the pressure is formed, the withstand voltage of the obtained second molded body is 200V / mm or more.

[0168] With such a structure, it is possible to obtain the insulator-coated soft magnetic powder 1 that contributes to the realization of a compact magnetic element with a high rated voltage.

[0169] In addition, in the insulator-coated soft magnetic powder 1 according to the above embodiment, the specific surface area is 0.010 m 2 / g or above and 0.600m 2 / g or less.

[0170] This structure suppresses agglomeration caused by surface energy, improving the packing capacity of the insulator-coated soft magnetic powder 1 during compaction. Furthermore, if the specific surface area falls within the aforementioned range, the occupancy rate of the insulating coating 3 within the compact can be optimized. As a result, an insulator-coated soft magnetic powder 1 can be obtained that improves the density and mechanical strength of the compact while suppressing a decrease in the magnetic permeability of the compact.

[0171] In the insulator-coated soft magnetic powder 1 according to the embodiment, the soft magnetic particles 2 (particles of the soft magnetic powder) are composed of a composition formula (Fe 1-x Cr x ) a (Si 1-y B y ) 100-a-b C b [wherein x, y, a, and b are 0<x≤0.06, 0.3≤y≤0.7, 70.0≤a≤81.0, and 0<b≤3.0.]

[0172] With such a structure, it is possible to obtain soft magnetic particles 2 having both high magnetic permeability and low coercive force.

[0173] In the insulator-coated soft magnetic powder 1 of the embodiment, the density of the first compact is 4.40 g / cm 3 Above and 5.00g / cm 3 the following.

[0174] This structure enables the manufacture of a high-density powder core by insulating the soft magnetic powder 1. Furthermore, this powder core can realize a magnetic element having high magnetic properties.

[0175] Furthermore, in the insulator-coated soft magnetic powder 1 according to the above embodiment, the amount of oxygen derived from the insulating coating 3 is 500 ppm or more and 7000 ppm or less in terms of mass ratio.

[0176] This structure particularly improves the insulation properties of the insulating coating 3. Therefore, even with a relatively thin insulating coating 3, an insulating-material-coated soft magnetic powder 1 can be obtained, which can produce a green compact having excellent interparticle insulation, for example, excellent withstand voltage. Furthermore, if the oxygen content of the insulating coating 3 is within the above range, the insulating coating 3 exhibits enhanced adhesion to the soft magnetic particles 2, enabling the production of a green compact having, for example, excellent mechanical strength.

[0177] In the insulator-coated soft magnetic powder 1 according to the above embodiment, the average thickness of the insulating coating 3 is 1 nm or more and 100 nm or less.

[0178] This structure ensures sufficient insulation properties of the insulating coating 3, reduces the space factor of the insulating coating 3 in the powder core, and improves the filling rate of the soft magnetic particles 2. Furthermore, even if the soft magnetic particles 2 have surface irregularities, the insulating coating 3 helps to smooth these irregularities and make them more spherical. This further improves the fluidity of the insulating coating 3 covering the soft magnetic powder 1.

[0179] Furthermore, the dust core according to the embodiment includes the insulator-coated soft magnetic powder according to the embodiment, thereby providing a dust core capable of realizing a magnetic element having a good balance of magnetic properties, insulation, and mechanical strength.

[0180] Furthermore, the magnetic element according to the embodiment includes the powder magnetic core according to the embodiment, thereby achieving a magnetic element having a good balance among magnetic properties, insulation properties, and mechanical strength.

[0181] Furthermore, the electronic device according to the embodiment includes the magnetic element according to the embodiment, thereby achieving electronic device with improved performance and reduced size.

[0182] As mentioned above, the insulator-coated soft magnetic powder, the powder magnetic core, the magnetic element, and the electronic device of the present invention have been described based on preferred embodiments, but the present invention is not limited thereto.

[0183] For example, in the above embodiments, a powder core is used as an example of an application of the insulator-coated soft magnetic powder of the present invention. However, the application is not limited to this example and may also include magnetic devices such as magnetic fluids, magnetic heads, and magnetic shielding sheets. Furthermore, the shapes of the powder core and magnetic element are not limited to those shown in the figure and may be any shape.

[0184] Furthermore, the powder magnetic core and the magnetic element according to the present invention may have arbitrary components added to the above-described embodiments.

[0185] Example

[0186] Next, specific examples of the present invention will be described.

[0187] 6. Preparation of soft magnetic powder covered with insulation

[0188] First, a soft magnetic powder having the composition shown in Table 1 was produced by a rotary water atomization method or a water atomization method. Table 2 shows the production method and average particle size of the soft magnetic powder.

[0189] Next, an insulating film was formed on the surface of the soft magnetic powder particles. Table 2 shows the film forming method, constituent materials, film thickness (average thickness), and oxygen content of the insulating film.

[0190] As described above, the insulator-coated soft magnetic powders of the sample Nos. shown in Table 2 were obtained.

[0191] The specific surface area and ring compression strength of the resulting insulation-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 insulation coating was formed. The measurement and calculation results are shown in Table 2.

[0192] [Table 1]

[0193] Composition formula (atomic ratio) Composition 1 <![CDATA[(Fe 0.97 Cr 0.03 ) 76 (Yes 0.5 B 0.5 ) 22 C2]]> Composition 2 <![CDATA[Fe 79 (And 0.3 B 0.7 ) 19 C2]]>

[0194] It should be noted that the composition 1 shown in Table 1 is a composition formula represented by the atomic ratio (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].

[0195] In Table 2 shown below, among the insulator-coated soft magnetic powders of each sample No., those corresponding to the present invention are designated as "Examples," and those not corresponding to the present invention are designated as "Comparative Examples."

[0196] 7. Evaluation of Insulation-Coated Soft Magnetic Powder

[0197] 7.1. Relative density of molded body

[0198] First, the insulator-coated soft magnetic powder of each example and each comparative example, 2.0% by mass of epoxy resin, and toluene were mixed. The resulting mixture was dried at 50°C for 1 hour and then pulverized to obtain granulated powder. The obtained granulated powder was then subjected to a pressure of 294.2 MPa (3 t / cm 2 The molded body was pressed and then heated at 150°C for 3 hours to cure the epoxy resin. Thus, a molded body was obtained. The shape of the molded body was a ring with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. Next, the density was calculated by dividing the mass of the obtained molded body by the volume. Next, the relative density was calculated by dividing the obtained density by the true density of the insulator-coated soft magnetic powder. The calculated relative density was then evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2.

[0199] A: Relative density is more than 67%

[0200] B: Relative density is 63% or more and less than 67%

[0201] C: Relative density less than 63%

[0202] 7.2. Magnetic permeability of molded bodies

[0203] First, molded bodies similar to those described in 7.1. were produced using the insulator-coated soft magnetic powder of each Example and Comparative Example. The magnetic permeability of the resulting molded bodies was then measured. The magnetic permeability of a molded body is the relative permeability, or effective permeability, obtained from the self-inductance of a closed magnetic circuit core coil fabricated within the aforementioned molded body. The magnetic permeability was measured using an impedance analyzer at a frequency of 100 kHz. The winding had 7 turns and a wire diameter of 0.6 mm.

[0204] The measured magnetic permeability was then evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2. It should be noted that the reference values ​​in the following evaluation criteria are values ​​set for each soft magnetic material. The reference value for Samples No. 1 to 5 and Samples No. 8 to 12 is Sample No. 7. Furthermore, the reference value for Sample No. 6 is Sample No. 13. Furthermore, the reference value for Sample No. 14 is Sample No. 15. Furthermore, the reference value for Samples No. 16, 17, and 19 is Sample No. 18.

[0205] A: The measured value of magnetic permeability is 105% or more of the reference value

[0206] B: The measured value of magnetic permeability is 100% or more and less than 105% of the reference value

[0207] C: The measured value of magnetic permeability is less than 100% of the reference value

[0208] 7.3 Withstand voltage

[0209] The withstand voltage of the insulator-coated soft magnetic powder of each Example and each Comparative Example was measured by the aforementioned method. The evaluation results are shown in Table 2.

[0210] [Table 2]

[0211]

[0212] As shown in Table 2, the insulator-coated soft magnetic powders of each Example can produce a powder compact having a higher density and higher insulation properties than the insulator-coated soft magnetic powders of each Comparative Example. This demonstrates that the use of the insulator-coated soft magnetic powders of each Example can produce a powder core having high mechanical strength and magnetic properties, as well as a high withstand voltage.

Claims

1. An insulator-covered soft magnetic powder, characterized in that: The insulator-covered soft magnetic powder comprises: soft magnetic powder; and an insulating film covering the surface of the particles of the soft magnetic powder, The average particle size of the soft magnetic powder is 2.0 μm or more and 40.0 μm or less. The specific surface area of ​​the soft magnetic powder covered by the insulating material is not less than 10% and not more than 100% of the specific surface area of ​​the soft magnetic powder alone. The epoxy resin was mixed so as to be 2.0% by mass and the pressure was 294.2 MPa (3.0 t / cm 2 When the pressure is formed, the compression ring strength of the obtained first molded body is greater than 10 MPa.

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

3. The insulator-coated soft magnetic powder according to claim 1 or 2, wherein: The epoxy resin was mixed so as to be 2.0% by mass and the pressure was 49.0 MPa, i.e., 0.5 t / cm 2 When the pressure is formed, the withstand voltage of the obtained second molded body is 200V / mm or more.

4. The insulator-coated soft magnetic powder according to claim 1 or 2, wherein The specific surface area of ​​the soft magnetic powder covered by the insulation is 0.010m 2 / g or above and 0.600m 2 / g or less.

5. The insulator-coated soft magnetic powder according to claim 1 or 2, wherein The particles are composed of a composition formula represented by an atomic ratio (Fe 1-x Cr x ) a (Si 1-y B y ) 100-a-b C b The composition of the amorphous alloy material is composed of 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。 6. The insulator-coated soft magnetic powder according to claim 5, wherein The density of the first molded body is 4.40 g / cm 3 Above and 5.00g / cm 3 the following.

7. The insulator-coated soft magnetic powder according to claim 1 or 2, wherein The amount of oxygen derived from the insulating coating is 500 ppm or more and 7000 ppm or less in terms of mass ratio.

8. The insulator-coated soft magnetic powder according to claim 1 or 2, wherein The average thickness of the insulating film is greater than or equal to 1 nm and less than or equal to 100 nm.

9. A powder magnetic core, characterized in that: Containing the insulator-coated soft magnetic powder according to claim 1 or 2.

10. A magnetic element, characterized in that: A powder magnetic core according to claim 9 is provided.

11. An electronic device, characterized in that: A magnetic element according to claim 10 is provided.

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