Soft magnetic metal powder, dust cores, magnetic parts and electronic devices

Abstract

To provide a magnetic powder core favorable in voltage endurance and magnetic permeability, a magnetic component comprising the same and a soft-magnetic metal powder suited for the magnetic powder core.SOLUTION: A soft-magnetic metal powder contains soft-magnetic metal particles, in which the soft-magnetic metal particles each comprise a metal particle and an oxidized portion covering the metal particle. The metal particle and the oxidized portion have an interface having irregularity, in which the interface between the metal particle and the oxidized portion has a roughness having a maximum height Rz of 1.0 nm or greater and 50.0 nm or smaller.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a soft magnetic metal powder, a dust core, a magnetic component, and an electronic device. [Background technology]

[0002] Patent Document 1 discloses that powdered glass containing an oxide of phosphorus (P) is softened by mechanical friction to form an insulating coating layer on the surface of Fe-based amorphous alloy powder. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-132010 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for a higher level of both voltage resistance and high magnetic permeability.

[0005] An object of the present invention is to provide a powder magnetic core having good voltage resistance and magnetic permeability, a magnetic component including the powder magnetic core, and soft magnetic metal powder suitable for the powder magnetic core. [Means for solving the problem]

[0006] The soft magnetic metal powder according to the present invention comprises soft magnetic metal particles, the soft magnetic metal particles have metal particles and oxidized portions coating the metal particles, The interface between the metal particle and the oxidized portion has irregularities, and the maximum height Rz of the roughness of the interface between the metal particle and the oxidized portion is 1.0 nm or more and 50.0 nm or less.

[0007] The arithmetic mean roughness Ra of the interface may be 0.2 nm or more and 10.0 nm or less.

[0008] The average thickness of the oxidized portion may be 1.0 nm or more and 100 nm or less.

[0009] The soft magnetic metal particles may further have a coating portion that coats the oxidized portion.

[0010] The average thickness of the coating portion may be 1.0 nm or more and 100 nm or less.

[0011] The dust core of the present invention contains the soft magnetic metal powder described above.

[0012] The magnetic component of the present invention contains the soft magnetic metal powder described above.

[0013] The electronic device of the present invention includes the soft magnetic metal powder described above. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a cross-sectional schematic view of a soft magnetic metal particle. [Figure 2] FIG. 2 is a cross-sectional schematic view of a soft magnetic metal particle. [Figure 3] 1 is a cross-sectional image of a soft magnetic metal particle. [Figure 4] 1 is a cross-sectional image of a soft magnetic metal particle. [Figure 5] FIG. 1 is a cross-sectional schematic view of a powder coating apparatus. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described in detail below based on specific embodiments shown in the drawings in the following order.

[0016] 1. Soft magnetic metal powder 1.1.Material of metal particles 1.2.Oxidation section 1.3. Covering 2.Powder magnetic core 3. Magnetic parts 4.Electronic equipment 5. Manufacturing method of powder magnetic core 5.1. Manufacturing method of soft magnetic metal powder 5.2. Manufacturing method of powder magnetic core

[0017] (1. Soft magnetic metal powder) The soft magnetic metal powder includes soft magnetic metal particles 1. As shown in Fig. 1, the soft magnetic metal particles 1 have metal particles 2 and oxidized portions 11 that coat the metal particles 2. Furthermore, as shown in Fig. 1, the soft magnetic metal particles 1 may further have coating portions 12 that coat the oxidized portions 11.

[0018] The shape of the soft magnetic metal particles 1 contained in the soft magnetic metal powder is preferably spherical. For example, the average circularity of the cross section of the soft magnetic metal particles 1 contained in the soft magnetic metal powder may be 0.85 or more. The circularity of the cross section of the soft magnetic metal particle 1 is preferably 2×(π×cross-sectional area) 1 / 2 The circularity calculated by dividing the circumference by the cross section was used.

[0019] The average particle size (D50) of the soft magnetic metal particles 1 contained in the soft magnetic metal powder may be selected depending on the application and material. The average particle size (D50) of the soft magnetic metal particles 1 may be in the range of 0.3 to 100 μm. By setting the average particle size of the soft magnetic metal particles 1 within the above range, it becomes easy to maintain sufficient moldability. It also becomes easy to maintain predetermined magnetic properties. There are no particular limitations on the method for measuring the average particle size of the soft magnetic metal particles 1. For example, a laser diffraction scattering method may be used.

[0020] When calculating the average particle diameter (D50) from a magnetic component, the cross section of the magnetic component may be observed. In this case, the circle-equivalent diameter of each soft magnetic metal particle contained in the cross section of the magnetic component is calculated, and the circle-equivalent diameter of each soft magnetic metal particle is used as the particle diameter of each soft magnetic metal particle. The average particle diameter (D50) is then calculated from the particle diameter of each soft magnetic metal particle.

[0021] The soft magnetic metal particles 1 contained in the soft magnetic metal powder may all be made of the same material or may be made of different materials.

[0022] (1.1. Metal particles) The metal particles 2 may be made of a soft magnetic metal containing iron (Fe). Examples of soft magnetic metals containing iron include Fe-based crystalline materials, Fe-based amorphous alloys, and Fe-based nanocrystalline alloys.

[0023] The Fe-based amorphous alloy may be composed of only an amorphous phase, or may have a structure in which primary crystallites are dispersed in an amorphous phase, that is, a nanoheterostructure.

[0024] Fe-based nanocrystalline alloys have a structure in which nanometer-order Fe-based nanocrystals are dispersed in an amorphous phase.

[0025] The soft magnetic metal containing iron is preferably an Fe-based amorphous alloy or an Fe-based nanocrystalline alloy. In the following, an Fe-based amorphous alloy and an Fe-based nanocrystalline alloy will be described.

[0026] The Fe-based amorphous alloy may be composed of only an amorphous phase, or may have a nanoheterostructure. The nanoheterostructure is a structure obtained by rapidly cooling a molten metal of a soft magnetic metal raw material. The nanoheterostructure is a structure in which a large number of primary microcrystals are precipitated and dispersed in the amorphous alloy. The average crystal grain size of the primary microcrystals may be 0.3 nm or more and 10 nm or less.

[0027] The composition of Fe-based amorphous alloys will be explained in detail.

[0028] There are no particular limitations on the composition of the Fe-based amorphous alloy. system The composition of amorphous alloys is (Fe (1-(α+β)) X1 α X2 β ) (1-(a+b+c+d+e+f)) M a B b P c Si d C e S f It may be expressed as:

[0029] In the above composition formula, M is at least one element selected from the group consisting of niobium (Nb), hafnium (Hf), zirconium (Zr), tantalum (Ta), molybdenum (Mo), tungsten (W), titanium (Ti), and vanadium (V).

[0030] The atomic ratio (a) of M may satisfy 0≦a≦0.300 from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core. system The amorphous alloy may not contain M.

[0031] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦a≦0.150 may be satisfied. Furthermore, a may be 0.040 or more, or 0.050 or more. a may be 0.100 or less, or 0.080 or less. A small a makes it easier to optimize the saturation magnetization of the soft magnetic metal powder.

[0032] The atomic ratio (b) of boron (B) may satisfy 0≦b≦0.400 from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core. system The amorphous alloy may not contain B.

[0033] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦b≦0.200 may be satisfied. Furthermore, b may be 0.025 or more, 0.060 or more, or 0.080 or more. b may be 0.150 or less, or 0.120 or less. A small b makes it easier to optimize the saturation magnetization of the soft magnetic metal powder.

[0034] The atomic ratio (c) of phosphorus (P) may satisfy 0≦c≦0.400 from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core. system The amorphous alloy may not contain P.

[0035] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦c≦0.200 may be satisfied. Furthermore, c may be 0.005 or more, or 0.010 or more. c may be 0.100 or less. When c is within the above range, the resistivity of the soft magnetic metal powder is likely to be improved and the coercive force is likely to be reduced. When c is small, the saturation magnetization of the soft magnetic metal powder is likely to be optimized.

[0036] The atomic ratio (d) of silicon (Si) may satisfy 0≦d≦0.400 from the viewpoint of optimizing the withstand voltage and strength of the powder magnetic core. system The amorphous alloy may not contain Si.

[0037] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦d≦0.200 may be satisfied. Furthermore, d may be 0.001 or more, or 0.005 or more. d may be 0.040 or less. When d is within the above range, the coercive force of the soft magnetic metal powder is likely to decrease.

[0038] The atomic ratio (e) of carbon (C) may satisfy 0≦e≦0.400 from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core. system The amorphous alloy may not contain C.

[0039] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦e≦0.200 may be satisfied. Furthermore, e may be 0.001 or more. e may be 0.035 or less, or may be 0.030 or less. When e is within the above range, the coercive force of the soft magnetic metal powder is likely to decrease.

[0040] The atomic ratio (f) of sulfur (S) may satisfy 0≦f≦0.040 from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core. system The amorphous alloy may not contain S.

[0041] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, 0≦f≦0.020 may be satisfied. Furthermore, f may be 0.001 or more, or 0.002 or more. f may be 0.010 or less. When f is within the above range, the coercive force of the soft magnetic metal powder is likely to decrease.

[0042] Furthermore, when f is 0.001 or more, the circularity of the cross section of the soft magnetic metal particles 1 contained in the soft magnetic metal powder is more likely to be improved compared to when f = 0. This makes it easier to improve the density of the powder magnetic core.

[0043] The atomic ratio of iron (Fe) (1-(a+b+c+d+e+f)) may be 0.410 or more and 0.910 or less, from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core.

[0044] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, (1-(a+b+c+d+e+f)) may be 0.700 or more and 0.850 or less. When (1-(a+b+c+d+e+f)) is within the above range, a crystalline phase composed of crystals with a crystal grain size of more than 100 nm is less likely to occur.

[0045] Furthermore, as shown in the above composition formula, a portion of the iron may be compositionally substituted with X1 and / or X2.

[0046] X1 is at least one element selected from the group consisting of cobalt (Co) and nickel (Ni). In the above composition formula, α indicates the atomic ratio of X1 to the total of Fe, X1, and X2. α is 0 or more. That is, Fe system The amorphous alloy may not contain X1.

[0047] From the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core, the atomic ratio of X1 to the total number of atoms in the entire composition, i.e., the total number of atoms of X1 to the sum of Fe, X1, X2, M, B, P, Si, C, and S, may be 70.00 at % or less. In other words, the relationship 0≦α{1−(a+b+c+d+e+f)}≦0.7000 may be satisfied.

[0048] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, the atomic ratio of X1 to the total of Fe, X1, X2, M, B, P, Si, C, and S may be 40.00 at% or less. In other words, the relationship 0≦α{1−(a+b+c+d+e+f)}≦0.4000 may be satisfied.

[0049] X2 is at least one element selected from the group consisting of aluminum (Al), manganese (Mn), silver (Ag), zinc (Zn), tin (Sn), arsenic (As), antimony (Sb), copper (Cu), chromium (Cr), bismuth (Bi), nitrogen (N), oxygen (O), and rare earth elements. In the above composition formula, β indicates the atomic ratio of X2 to the total of Fe, X1, and X2. β is 0 or more. That is, Fe system The amorphous alloy may not contain X2.

[0050] From the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core, the atomic ratio of X2 to the total number of atoms in the entire composition, i.e., the total number of atoms of Fe, X1, X2, M, B, P, Si, C, and S, may be 6.00 at % or less, i.e., the relationship 0≦β{1−(a+b+c+d+e+f)}≦0.0600 may be satisfied.

[0051] From the viewpoint of optimizing the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, the atomic ratio of X2 to the total of Fe, X1, X2, M, B, P, Si, C, and S may be 3.00 at% or less. In other words, the relationship 0≦β{1−(a+b+c+d+e+f)}≦0.0300 may be satisfied.

[0052] Furthermore, from the viewpoint of optimizing the voltage resistance and strength of the powder magnetic core, the range in which X1 and / or X2 substitute for iron (substitution ratio) may be 0.94 or less of the total number of Fe atoms in atomic terms, i.e., 0≦α+β≦0.94.

[0053] To optimize the soft magnetic properties of the soft magnetic metal powder and the powder magnetic core, the range in which X1 and / or X2 substitute for iron may be less than half the total number of Fe atoms in atomic terms. That is, 0≦α+β≦0.50 may be satisfied. If α+β>0.50, it is difficult to obtain a soft magnetic metal in which Fe-based nanocrystals are precipitated by heat treatment.

[0054] The Fe-based amorphous alloy may contain, as unavoidable impurities, elements other than those mentioned above, i.e., elements other than Fe, X1, X2, M, B, P, Si, C, and S. For example, the Fe-based amorphous alloy may contain 0.1% by mass or less in total of elements other than Fe, X1, X2, M, B, P, Si, C, and S relative to 100% by mass of the Fe-based amorphous alloy.

[0055] By heat treating an Fe-based amorphous alloy having a nanoheterostructure under predetermined conditions, primary crystallites can be grown to obtain an Fe-based nanocrystalline alloy.

[0056] Fe-based nanocrystalline alloys contain Fe-based nanocrystals. Fe-based nanocrystals are Fe crystals with a crystal grain size on the order of nanometers and a bcc (body-centered cubic) crystal structure. In Fe-based nanocrystalline alloys, numerous Fe-based nanocrystals are precipitated and dispersed in the amorphous phase. Fe-based nanocrystals can be conveniently obtained by heat-treating Fe-based amorphous alloys with nanoheterostructures to grow primary microcrystals.

[0057] Therefore, the average crystal grain size of the Fe-based nanocrystals tends to be slightly larger than that of the primary crystallites. In this embodiment, the average crystal grain size of the Fe-based nanocrystals may be 5 nm or more and 30 nm or less. A soft magnetic metal powder containing a soft magnetic metal in which Fe-based nanocrystals are dispersed in an amorphous phase is likely to have high saturation magnetization and low coercive force.

[0058] In this embodiment, the composition of the Fe-based nanocrystalline alloy may be the same as the composition of the Fe-based amorphous alloy described above, and therefore the above description of the composition of the Fe-based amorphous alloy also applies to the description of the composition of the Fe-based nanocrystalline alloy.

[0059] (1.2. Oxidized part) The oxidized portion 11 is formed so as to cover the surface of the metal particle 2 as shown in FIG. 1 . Furthermore, "the surface is coated with a substance" is synonymous with "the substance comes into contact with the surface and is fixed so as to cover the contacted portion." Furthermore, the oxidized portion 11 that covers the metal particle 2 only needs to cover at least a portion of the surface of the metal particle 2. Approximately 90% or more of the surface of the metal particle 2 may be covered with the oxidized portion 11. The entire surface of the metal particle 2 may be covered with the oxidized portion 11. The oxidized portion 11 may cover the surface of the metal particle 2 continuously or discontinuously.

[0060] The composition of the oxidized portion 11 is not particularly limited, but it contains at least an oxide of an element contained in the metal particle 2. For example, if the metal particle 2 contains Fe, it contains an oxide of Fe. As will be described later, the surface of the metal particle 2 is oxidized to form an oxide. Department 11 may be formed.

[0061] As shown in FIG. 2, in the soft magnetic metal particle 1, the interface 2a between the metal particle 2 and the oxidized portion 11 has irregularities.

[0062] The roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 increases due to the unevenness. Specifically, the maximum height Rz of the roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 is 1.0 nm or more and 50.0 nm or less. The maximum height Rz may be 4.3 nm or more and 49.3 nm or less. The arithmetic mean roughness Ra of the roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 may be 0.2 nm or more and 10.0 nm or less, or 0.2 nm or more and 9.9 nm or less.

[0063] When the maximum height Rz is within a predetermined range, the withstand voltage of the powder magnetic core produced using the soft magnetic metal powder containing the soft magnetic metal particles 1 is improved. If the maximum height Rz is too small or too large, the withstand voltage of the powder magnetic core is not sufficiently improved. Furthermore, the magnetic permeability of the powder magnetic core may also decrease.

[0064] Furthermore, by having the arithmetic mean roughness Ra within a predetermined range, it becomes easier to achieve a good balance between the withstand voltage and the magnetic permeability.

[0065] Hereinafter, the term "roughness" refers to two types of roughness: maximum height Rz and arithmetic mean roughness Ra. There are no particular limitations on the method for measuring roughness. Below, a method for measuring roughness by observing the cross section of the soft magnetic metal particle 1 will be described.

[0066] In observing the cross section of the soft magnetic metal particle 1, the cross section of the soft magnetic metal particle 1 is observed using a known electron microscope (scanning electron microscope: SEM, transmission electron microscope: TEM, etc.). For example, the metal particle 2 and the oxidized portion 11 are identified based on the contrast difference in the observed image, the results of composition analysis by EDS, etc. The curve that is the interface 2a between the metal particle 2 and the oxidized portion 11 is taken as the contour curve. Then, the roughness is calculated from the obtained contour curve.

[0067] For example, Fig. 3 shows a cross-sectional image of an example described later. Fig. 4 shows a cross-sectional image of a comparative example described later in which the roughness is too small. In the cross-sectional image shown in Fig. 3, the soft magnetic metal particle 1 has unevenness at the interface 2a between the metal particle 2 and the oxidized portion 11. Therefore, the soft magnetic metal particle 1 shown in Fig. 3 has sufficiently large roughness at the interface 2a. In contrast, in the cross-sectional image shown in Fig. 4, the soft magnetic metal particle 1 does not have unevenness at the interface 2a between the metal particle 2 and the oxidized portion 11. Therefore, the soft magnetic metal particle 1 shown in Fig. 4 has too small roughness at the interface 2a.

[0068] Specifically, the roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 can be calculated using a method similar to that used to calculate surface roughness. First, factors due to the shape and factors due to waviness are removed from the obtained profile curve to obtain a roughness curve. Based on the obtained roughness curve, Rz and Ra are calculated in accordance with the method specified in JIS B 601. That is, Rz and Ra can be measured using a method similar to that specified in JIS B 601. However, Rz and Ra may also be measured under conditions different from those specified in JIS B 601.

[0069] The roughness curve can be obtained from the contour curve by known filtering, smoothing, or the like.

[0070] Furthermore, when the soft magnetic metal particles 1 are contained in a soft magnetic metal powder, in order to obtain highly accurate Rz and Ra, it is preferable to measure the roughness of the interface 2a for soft magnetic metal particles 1 with a high circularity, specifically soft magnetic metal particles 1 with a circularity of 0.95 or more. Furthermore, it is preferable to measure the roughness of the interface 2a at any location on any 10 to 100 soft magnetic metal particles 1 with a high circularity.

[0071] The reference length of the profile curve may be 0.1 μm to 50 μm. The profile curve may be measured at approximately 10 to 100 locations per soft magnetic metal particle 1. The average value of Rz calculated from the respective measurement results may be used as the Rz of the soft magnetic metal powder. The average value of Ra calculated from the respective measurement results may be used as the Ra of the soft magnetic metal powder.

[0072] The maximum height Rz is the sum of the height of the highest peak and the depth of the deepest valley in a reference length extracted from the roughness curve in the direction of the mean line of the roughness curve.

[0073] The arithmetic mean roughness Ra is defined as shown in Equation 2 when a reference length is extracted from the roughness curve in the direction of the mean line of the roughness curve, the x-axis is taken in the direction of the mean line of this extracted portion, and the y-axis is taken in the direction of the longitudinal magnification, and the roughness curve is expressed by Equation 1. In other words, it is the average distance from the mean line of the roughness curve to the roughness curve itself. Note that L is the reference length.

[0074]

number

[0075]

number

[0076] (1.3. Covering part) As shown in FIG. 1 , the coating 12 is formed so as to cover the surface of the oxidized portion 11. The coating 12 is formed so as to cover the surface of the metal particle 2 in the areas where the oxidized portion 11 is not formed. Hereinafter, "the surface of the oxidized portion 11 or the metal particle 2" means "the surface of the oxidized portion 11 in the areas where the oxidized portion 11 is formed and the surface of the metal particle 2 in the areas where the oxidized portion 11 is not formed." Furthermore, in this embodiment, "the surface is coated with a substance" is synonymous with "a substance is in contact with the surface and fixed so as to cover the contacted area." Furthermore, the coating 12 that coats the oxidized portion 11 or the metal particle 2 need only cover at least a portion of the surface of the oxidized portion 11. Approximately 90% or more of the "surface of the oxidized portion 11 or the metal particle 2" may be covered by the coating 12. The entire "surface of the oxidized portion 11 or the metal particle 2" may be covered by the coating 12. The coating 12 may cover the "surface of the oxidized portion 11 or the metal particle 2" continuously or intermittently.

[0077] There are no particular restrictions on the material of the coating portion 12. The material of the coating portion 12 may be any material that can insulate the soft magnetic metal particles 1 that make up the soft magnetic metal powder from each other. In other words, the material of the coating portion 12 is insulating. For example, the coating portion 12 may contain at least one element selected from the group consisting of phosphorus (P), aluminum (Al), calcium (Ca), barium (Ba), bismuth (Bi), silicon (Si), chromium (Cr), sodium (Na), zinc (Zn), and oxygen (O). Preferably, the coating portion 12 contains a compound containing at least one element selected from the group consisting of phosphorus, zinc, and sodium. The compound is more preferably an oxide, and particularly preferably an oxide glass.

[0078] When the compound is an oxide, the coating 12 preferably contains, as a primary component, an oxide of at least one element selected from the group consisting of P, Al, Ca, Ba, Bi, Si, Cr, Na, and Zn. "The coating 12 preferably contains, as a primary component, an oxide of at least one element selected from the group consisting of P, Al, Ca, Ba, Bi, Si, Cr, Na, and Zn" means that, when the total amount of elements excluding oxygen in the coating 12 is taken as 100 mass%, the total amount of at least one element selected from the group consisting of P, Al, Ca, Ba, Bi, Si, Cr, Na, and Zn is the largest. Furthermore, the total amount of at least one element selected from the group consisting of P, Al, Ca, Ba, Bi, Si, Cr, Na, and Zn in the coating 12 is preferably 50 mass% or more, and more preferably 60 mass% or more.

[0079] When the compound is oxide glass, the type of oxide glass is not particularly limited, and examples thereof include phosphate (P2O5)-based glass, bismuthate (Bi2O3)-based glass, and borosilicate (B2O3-SiO2)-based glass.

[0080] The P2O5-based glass is preferably a glass containing 50 mass% or more of P2O5. Examples of P2O5-based glass include P2O5-ZnO-R2O-Al2O3-based glass. Note that R contained as R2O in P2O5-based glass is an alkali metal.

[0081] The Bi2O3-based glass is preferably a glass containing 50 mass % or more of Bi2O3. Examples of Bi2O3-based glass include Bi2O3-ZnO-B2O3-SiO2-based glass.

[0082] The B2O3-SiO2-based glass is preferably a glass containing 10% by mass or more of B2O3 and 10% by mass or more of SiO2. Examples of the B2O3-SiO2-based glass include BaO-ZnO-B2O3-SiO2-Al2O3-based glass.

[0083] In the soft magnetic metal powder, metal particles 2 having oxidized portions 11 with Ra and Rz within the predetermined ranges further have coating portions 12, thereby improving the withstand voltage of a dust core made of the soft magnetic metal powder.

[0084] The components contained in the coating portion 12 can be identified from information such as lattice constants obtained by elemental analysis using energy dispersive X-ray spectroscopy (EDS) with a transmission electron microscope (TEM) such as a scanning transmission electron microscope (STEM), elemental analysis using electron energy loss spectroscopy (EELS), or fast Fourier transform (FFT) analysis of TEM images.

[0085] There are no particular limitations on the method for measuring the thickness of the oxidized portion 11 and the coating portion 12. For example, the thickness can be measured by observing the cross section of the soft magnetic metal particle 1 with a known electron microscope (scanning electron microscope: SEM, transmission electron microscope: TEM, etc.) and identifying the oxidized portion 11 and the coating portion 12 based on the contrast difference in the observed image and the results of composition analysis by EDS. The thickness of the oxidized portion 11 and the coating portion 12 are preferably measured at approximately 5 to 10 locations per soft magnetic metal particle 1. Furthermore, the average thickness of the oxidized portion 11 and the average thickness of the coating portion 12 are preferably measured for 10 to 100 soft magnetic metal particles 1. The average thickness of the oxidized portion 11 and the average thickness of the coating portion 12 can be calculated from the obtained measurement results.

[0086] There is no particular limitation on the average thickness of the oxidized portion 11. For example, it may be 1.0 nm or more and 100 nm or less. From the viewpoint of obtaining high magnetic permeability, it is preferably 20 nm or less. From the viewpoint of achieving both high magnetic permeability and high withstand voltage, it is preferably 5.0 nm or more and 20 nm or less, and more preferably 5.0 nm or more and 15 nm or less.

[0087] There is no particular limitation on the average thickness of the coating portion 12. For example, it may be 1.0 nm or more and 100 nm or less, or 1.0 nm or more and 50 nm or less, and preferably 10 nm or more and 50 nm or less.

[0088] Furthermore, when the number ratio of soft magnetic metal particles 1 contained in the soft magnetic metal powder is 100%, the number ratio of soft magnetic metal particles 1 having metal particles 2, oxidized portions 11 coating the metal particles 2, and coating portions 12 coating the oxidized portions 11 may be 90% or more, or may be 95% or more.

[0089] (2.Powder magnetic core) The powder magnetic core may contain the soft magnetic metal powder and be formed into a predetermined shape. The powder magnetic core may contain, for example, a soft magnetic metal powder and a resin as a binder. The soft magnetic metal particles constituting the soft magnetic metal powder may be bonded to each other via the resin, thereby fixing the powder magnetic core into a predetermined shape.

[0090] The dust core may be made of a mixed powder of the soft magnetic metal powder and other magnetic powder, and may be formed into a predetermined shape.

[0091] Generally, in powder magnetic cores, the magnetic properties can be improved by increasing the proportion of magnetic components (filling rate). One known method for increasing the proportion of magnetic components (filling rate) is to reduce the amount of insulating resin. However, reducing the resin content in a powder magnetic core increases the proportion of soft magnetic metal particles that come into contact with each other. As a result, when an AC voltage is applied to a magnetic component that contains a powder magnetic core, losses due to the current flowing between contacting soft magnetic metal particles (interparticle eddy currents) increase. This results in increased core loss in the powder magnetic core.

[0092] In order to suppress eddy currents, a coating portion is formed on the surface of the soft magnetic metal particles. The present inventors have found that by producing a powder magnetic core containing the above-mentioned soft magnetic metal powder, it is possible to produce a powder magnetic core with high withstand voltage and magnetic permeability and low core loss.

[0093] (3. Magnetic parts) The magnetic component may be any component that includes a powder magnetic core containing the soft magnetic metal powder. For example, the magnetic component may be a powder magnetic core of a predetermined shape with an air-core coil formed by winding a wire embedded inside. Alternatively, the magnetic component may be a powder magnetic core of a predetermined shape with a predetermined number of turns of wire wound around the surface thereof.

[0094] (4.Electronic equipment) The electronic device may be any electronic device having a magnetic component including a powder magnetic core containing the soft magnetic metal powder. For example, a power inductor used in a power supply circuit may be used. When the magnetic component includes a powder magnetic core containing the soft magnetic metal powder, the voltage resistance is good.

[0095] Other known magnetic components used in the power supply circuits of various electronic devices include transformers and choke coils.

[0096] (5. Manufacturing method of powder magnetic core) A method for producing a dust core containing the soft magnetic metal powder will now be described. First, a method for producing the soft magnetic metal powder will be described.

[0097] (5.1. Method for producing soft magnetic metal powder) To obtain the soft magnetic metal powder, first, a powder containing the metal particles 2 is produced. As a method for producing the metal particles 2, a method similar to a known production method can be used. Specifically, the metal particles 2 can be produced using a gas atomization method, a water atomization method, a rotating disk method, or the like. Alternatively, the metal particles 2 can be produced by mechanically pulverizing a thin ribbon obtained by a single roll method, or the like. Of these production methods, the gas atomization method is preferably used from the viewpoint that it is easy to obtain soft magnetic metal powder having the desired shape and magnetic properties.

[0098] In the gas atomization method, first, a molten metal is obtained by melting the raw materials of the metal particles 2. Raw materials (pure metals, etc.) of each metal element contained in the metal particles 2 are prepared, weighed to obtain the final composition of the obtained metal particles 2, and the raw materials are melted. There are no particular limitations on the method for melting the raw materials of the metal elements. For example, there is a method in which the raw materials are melted by high-frequency heating after evacuating the chamber of the atomization device. The temperature during melting may be determined taking into consideration the melting point of each metal element. It can be 1200 to 1600°C.

[0099] The resulting molten metal is supplied as a linear, continuous fluid into the chamber through a nozzle at the bottom of the crucible. High-pressure gas is sprayed onto the supplied molten metal to break it into droplets and rapidly cool it to obtain a fine powder. The gas injection temperature, pressure within the chamber, and other factors can be determined depending on the composition, structure, and other factors of the metal particles 2.

[0100] The gas injection temperature may be 10 to 200°C.

[0101] The average particle size (D50) of the obtained metal powder may be 1 to 50 μm. The average circularity of the cross section of the metal particles contained in the obtained powder may be 0.60 to 1.00, preferably 0.85 to 1.00, and more preferably 0.93 to 1.00. The particle size of the metal particles 2 may be adjusted by sieve classification, air classification, or the like.

[0102] By producing powder containing metal particles under conditions within the above ranges, it becomes easier to control Rz and Ra within specific ranges by mechanochemical treatment in an oxygen atmosphere, which will be described later.

[0103] The metal particles 2 contained in the powder obtained at this stage are made of a crystalline or amorphous alloy.

[0104] If the metal particles 2 contain crystals with a crystal particle diameter greater than 30 nm, the metal particles 2 are determined to be crystalline. If the metal particles 2 do not contain crystals with a crystal particle diameter greater than 30 nm, the metal particles 2 are determined to be amorphous alloys. Whether or not the metal particles 2 contain crystals with a crystal particle diameter greater than 30 nm can be evaluated by a known method. For example, X-ray diffraction measurement or TEM observation can be used. When using TEM, this can be confirmed by obtaining a selected area diffraction image or a nanobeam diffraction image. When using a selected area diffraction image or a nanobeam diffraction image, if the metal particles 2 are made of an amorphous alloy, ring-shaped diffraction is formed in the diffraction pattern. In contrast, if the metal particles 2 are made of a crystalline material, diffraction spots due to the crystalline structure are formed in the diffraction pattern.

[0105] There are no particular limitations on the method for evaluating the presence or absence of primary crystallites and the average crystal particle size in the metal particles 2 made of an amorphous alloy. They may be evaluated by a known method. For example, they can be confirmed by obtaining a bright-field image or a high-resolution image using a TEM on a sample thinned by ion milling. Specifically, at a magnification of 1.00 × 10 5 ~3.00×10 5The presence or absence of primary microcrystals and the average crystal particle size can be evaluated by visually observing bright-field images or high-resolution images obtained at 370x magnification.

[0106] When obtaining a powder containing metal particles 2 made of a nanocrystalline alloy, it is preferable to heat treat the powder containing metal particles 2 made of an amorphous alloy in order to precipitate Fe-based nanocrystals.

[0107] By subjecting powder containing metal particles 2 made of an amorphous alloy to heat treatment, the metal particles 2 are prevented from sintering together and the powder becomes coarse, while diffusing the elements contained in the metal particles 2 is promoted. As a result, Fe-based nanocrystals can be precipitated on the metal particles 2.

[0108] The heat treatment conditions are not particularly limited as long as they facilitate the precipitation of Fe-based nanocrystals. For example, the heat treatment temperature can be 400 to 700°C, and the holding time can be 0.5 to 10 hours. The heat treatment is performed in an inert atmosphere, such as an Ar atmosphere.

[0109] The heat treatment results in a powder containing metal particles 2 made of a nanocrystalline alloy.

[0110] Next, the obtained powder containing metal particles 2 is subjected to a pretreatment to form oxidized portions 11 on the metal particles 2. There are no particular limitations on the pretreatment method for forming oxidized portions 11. For example, a method using mechanochemical treatment in an oxygen atmosphere can be mentioned.

[0111] Conventionally, a method of forming an oxidized portion 11 on the surface of a metal particle 2 involves heat treatment in an oxygen atmosphere. However, with this method, the roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 hardly changes from the surface roughness of the metal particle 2 before the heat treatment. Furthermore, Rz does not reach 1.0 nm or more.

[0112] The present inventors have found that the pretreatment for forming the oxidized portion 11 can be performed by mechanochemical treatment in an oxygen atmosphere. Specifically, the mechanochemical treatment in an oxygen atmosphere is performed using a powder coating apparatus 100 shown in FIG. 5. The powder coating apparatus 100 has traditionally been used for coating various powders. The present inventors have found that by using the powder coating apparatus 100 to oxidize the metal particles 2 contained in the powder, the oxidation can be favorably promoted while increasing the roughness of the interface 2a between the metal particles 2 and the oxidized portion 11.

[0113] Specifically, first, powder containing metal particles 2 is charged into the powder coating apparatus 100 in an oxygen atmosphere. Next, the rotor 101 in the powder coating apparatus 100 is rotated. In the oxygen atmosphere, the powder containing metal particles 2 is compressed between the press head 102 and the inner wall of the rotor 101. Then, in the oxygen atmosphere, the surfaces of the metal particles 2 become hot due to heat generated by friction, and the friction increases the surface roughness of the metal particles 2. At the same time, oxidation of the surfaces of the metal particles 2 progresses.

[0114] In the mechanochemical treatment under an oxygen atmosphere, first, the oxygen concentration in the powder coating apparatus 100 is adjusted. From the viewpoint of controlling Rz to 1.0 nm or more and 50 nm or less, it is preferable to set the oxygen concentration to 1% or more and 5% or less. If the oxygen concentration is too low, Rz becomes too small. If the oxygen concentration is too high, Rz becomes too large.

[0115] The gap is the distance between the inner wall of the rotor 101 and the press head 102 in the powder coating apparatus 100. The larger the gap, the smaller the friction between the surface of the metal particles 2 and the wall surface. As a result, when the soft magnetic metal particles 1 finally obtained are compressed to produce a powder magnetic core, the voltage resistance of the resulting powder magnetic core tends to deteriorate. The size of the gap varies depending on the structure of the powder coating apparatus 100 and the particle size of the metal particles, but may be, for example, 1 mm or more and 10 mm or less.

[0116] There is no particular limit to the processing time for mechanochemical treatment in an oxygen atmosphere. The longer the processing time, the thicker the oxidized portion 11. The thicker the oxidized portion 11, the higher the withstand voltage of the final powder magnetic core, but the lower the magnetic permeability. The processing time may be, for example, 15 minutes or more and 180 minutes or less. In addition, the oxygen concentration in the oxidizing atmosphere, the gap size, the processing time, etc. may be appropriately adjusted so that Rz and Ra fall within a favorable range.

[0117] Next, the coating portion 12 is formed on the metal particles 2 on which the oxidized portion 11 has been formed. There are no particular limitations on the method for forming the coating portion 12, and any known method can be used. For example, the coating portion 12 may be formed by subjecting the metal particles 2 to a wet treatment, or may be formed by subjecting the metal particles 2 to a dry treatment. Alternatively, the coating portion can be formed by a mechanochemical coating method, a phosphate treatment method, a sol-gel method, or the like.

[0118] In a mechanochemical coating method, for example, a powder coating apparatus 100 shown in FIG. 5 is used. When oxidized portions 11 are formed on metal particles 2 by mechanochemical processing in an oxygen atmosphere, a powder coating material of the material constituting the coating portion (e.g., a compound of P, Al, Ca, Ba, Bi, Si, Cr, Na, or Zn) is added to powder containing metal particles 2 on which oxidized portions 11 are formed in the powder coating apparatus 100 to prepare a mixture 50. Then, by rotating the rotor 101, the mixture 50 is compressed between the press head 102 and the inner wall of the rotor 101, causing friction and generating heat. The generated frictional heat softens the powder coating material, and the powder coating material adheres to the surface of the oxidized portion 11 due to the compression action. The adhered coating material is cooled to form the coating portion 12.

[0119] In the mechanochemical coating method, the generated frictional heat can be controlled by adjusting the rotation speed, gap, etc. of the rotor 101. The temperature of the mixture 50 can also be controlled. The temperature of the mixture 50 may be 50°C or higher and 150°C or lower. By setting the temperature within this range, the coating portion 12 can be easily formed to cover the surface of the oxidized portion 11. Furthermore, the thickness of the coating portion 12 can be easily controlled by adjusting the mixing ratio between the metal particles 2 and the powder of the material that constitutes the coating portion 12.

[0120] If necessary, the soft magnetic metal powder containing the soft magnetic metal particles 1 on which the coating portions 12 are formed may be heat-treated.

[0121] When the oxidized portion 11 is formed on the metal particle 2 by mechanochemical treatment in an oxygen atmosphere, the roughness of the interface 2a between the metal particle 2 and the oxidized portion 11 is greater than that of the conventional method. That is, the metal particle 2 has irregularities, and the oxidized portion 11 also has irregularities. Department There may be a gap between 11.

[0122] When the powder coating material softens in this state, the softened coating material adheres to the surface of the oxidized portion 11. Furthermore, the metal particles 2 and the oxidized portion 11 are Department If there is a gap between the metal particles 2 and the oxide film 11, the softened coating material fills the gap. Department When 11 and the coating material are cooled to room temperature and hardened, the coating material undergoes volumetric shrinkage. If the metal particles 2 have irregularities, this volumetric shrinkage improves the adhesion between the metal particles 2 and the oxidized portion 11 and the coated portion 12.

[0123] When a powder magnetic core is produced using soft magnetic metal powder containing soft magnetic metal particles 1 with improved adhesion as described above, the number of locally voltage-vulnerable portions is reduced, resulting in an improved voltage resistance of the powder magnetic core.

[0124] (5.2. Manufacturing method of powder magnetic core) The powder magnetic core is manufactured using the soft magnetic metal powder described above. There are no particular limitations on the specific manufacturing method, and any known method can be used. For example, first, a soft magnetic metal powder containing soft magnetic metal particles 1 is mixed with a known resin as a binder to obtain a mixture. If necessary, the obtained mixture may be made into a granulated powder. The mixture or granulated powder is then filled into a mold and compression-molded to obtain a compact having the shape of the powder magnetic core to be manufactured.

[0125] The obtained compact is subjected to a heat treatment at, for example, 50 to 200°C, whereby the resin hardens and a powder magnetic core of a predetermined shape is obtained in which the soft magnetic metal particles 1 are fixed via the resin. A magnetic component such as an inductor is obtained by winding a wire a predetermined number of times around the obtained powder magnetic core.

[0126] Alternatively, the mixture or granulated powder and an air-core coil formed by winding a wire a predetermined number of times may be filled into a mold and compression-molded to obtain a compact with the coil embedded therein. The obtained compact is subjected to a heat treatment to obtain a powder magnetic core of a predetermined shape with the coil embedded therein. Since such a powder magnetic core has a coil embedded therein, it functions as a magnetic component such as an inductor.

[0127] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and may be modified in various ways within the scope of the present invention. [Example]

[0128] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0129] (Experimental Example 1) First, the raw material metal for the soft magnetic metal powder was prepared. The prepared raw material metal was weighed so that the Fe content was 95.5% by mass and the Si content was 4.5% by mass, and then placed in a crucible placed in an atomization device. Next, after evacuating the chamber, the crucible was heated by high-frequency induction using a work coil installed outside the crucible. The raw material metal in the crucible was melted and mixed to obtain a molten metal at 1600°C.

[0130] The resulting molten metal was fed into the chamber as a linear, continuous fluid through a nozzle at the bottom of the crucible, and gas was sprayed onto the molten metal to obtain powder. The gas temperature was set to 20°C.

[0131] The average particle size (D50) of the obtained powder was 20 μm, and the average circularity of the cross section of the particles contained in the obtained powder was 0.97 to 0.98.

[0132] The obtained powder was subjected to X-ray diffraction measurement to confirm the presence or absence of crystals with a crystal grain size larger than 30 nm. If no crystals with a crystal grain size larger than 30 nm were present, it was determined that the soft magnetic metal constituting the powder was made of an amorphous alloy, and if crystals with a crystal grain size larger than 30 nm were present, it was determined that the soft magnetic metal was made of a crystalline material.

[0133] In Experimental Example 1, all of the resulting powder was crystalline.

[0134] The resulting powders were then subjected to the pretreatments shown in Table 1. Powders marked "None" in the pretreatment column were not subjected to pretreatment. Powders marked "Heat treated" were subjected to heat treatment. Powders marked "Mechanochemically treated" were subjected to mechanochemical treatment.

[0135] The heat treatment was performed at a temperature of 300° C. for 30 minutes with an oxygen concentration of 1% in the atmosphere.

[0136] The conditions of the mechanochemical treatment (gap size, oxygen concentration in the atmosphere, and holding time) are shown in Table 1.

[0137] When pretreatment was not performed, no oxidized portion was formed. When pretreatment was performed, the thickness of the oxidized portion measured by the measurement method described below is shown in Table 1.

[0138] Next, the powder of each sample was placed in the container of a powder coating device together with a powder coating material. The powder coating material was then coated onto the surfaces of the particles contained in the powder to form a coating. The amount of powder coating material added was set to 0.01 to 3 mass% relative to 100 mass% of the powder after heat treatment. The coating time was 0.1 to 8 hours. The temperature of the mixture of powder and powder coating material after heat treatment was 50 to 150°C. The number ratio of coated particles in the powder after coating formation was 85 to 95%. The thickness of the coating, as measured by the measurement method described below, was set to 25 nm.

[0139] In Experimental Example 1, phosphate-based glass having a composition of P2O5-ZnO-R2O-Al2O3 was used as the powdered coating material. The specific composition of the phosphate-based glass was 50 mass% P2O5, 12 mass% ZnO, 20 mass% R2O, 6 mass% Al2O3, and the remainder were minor components.

[0140] The inventors also conducted similar experiments using glass or the like having a composition of 60 mass % P2O5, 20 mass % ZnO, 10 mass % R2O, 5 mass % Al2O3, and the remainder being minor components as the powder coating material, and confirmed that similar results to those described below were obtained.

[0141] For soft magnetic metal particles on which an oxidized portion and a coating portion were formed, the thickness of the oxidized portion and the thickness of the coating portion were measured as follows. The cross section of the soft magnetic metal particle was observed using a TEM. The oxidized portion and the coating portion were identified based on the contrast difference in the obtained observation image. The size and magnification of the observation image were set to be sufficient to measure the thickness and roughness described below. Furthermore, the interface between the metal particle and the oxidized portion and the interface between the oxidized portion and the coating portion were also identified. When the interface between the oxidized portion and the coating portion could not be identified based on the observation image alone, EDS was used to identify it.

[0142] The thickness of the identified oxidized portion was measured at 10 points. The average value of the measured thicknesses was taken as the thickness of the oxidized portion. The thickness of the oxidized portion is shown in Table 1.

[0143] The thickness of the specified coating portion was measured at 10 points. The average value of the measured thicknesses was taken as the thickness of the coating portion. As described above, the thickness of the coating portion was 25 μm for all samples.

[0144] The roughness of the interface between the metal particle and the oxidized portion was then measured from the observed image. The results are shown in Table 1. Note that for Sample 1, in which the soft magnetic metal particles did not contain an oxidized portion, the roughness of the interface between the metal particle and the coating portion was measured. The results are shown in Table 1.

[0145] The coercive force Hc of the soft magnetic metal powder was measured using a measuring device, Model K-HC1000, manufactured by Tohoku Special Steel Co., Ltd., at a measuring magnetic field of 150 kA / m. The results are shown in Table 1.

[0146] Next, a powder magnetic core was produced. First, the thermosetting resin (epoxy resin) and the curing agent (imide resin) were weighed out so that the total amount was 3 parts by mass per 100 parts by mass of the obtained soft magnetic metal powder. The thermosetting resin and curing agent were added to acetone. The obtained solution was mixed with the soft magnetic metal powder. After mixing, the acetone was evaporated to obtain granules. The obtained granules were sized using a 355 μm mesh. The sized granules were filled into a toroidal mold with an outer diameter of 11 mm and an inner diameter of 6.5 mm. Next, a molding pressure of 3.0 t / cm was applied. 2The resulting powder core compact was heat treated at 180°C for 1 hour to harden the resin, thereby obtaining a powder core.

[0147] The withstand voltage of the obtained powder magnetic core was measured by the following method. In-Ga electrodes were formed on both ends of the obtained powder magnetic core sample. A voltage was applied to both ends using a voltage boosting breakdown tester (THK-2011ADMPT manufactured by Tama Densoku Co., Ltd.), and the voltage value when a current of 1 mA flowed was measured. The withstand voltage was calculated by dividing the obtained voltage value by the length of the powder magnetic core. The results are shown in Table 1.

[0148] The magnetic permeability of the obtained powder magnetic core was measured using an impedance analyzer (E4990A manufactured by Keysight Technologies), and the results are shown in Table 1. A magnetic permeability of 32.0 or more was considered good, and 35.0 or more was considered even better.

[0149] The withstand voltage ratio R is the withstand voltage ratio of each sample to the withstand voltage of a sample that was processed under the same conditions except for not undergoing pretreatment. V The magnetic permeability ratio Rμ was calculated by comparing the magnetic permeability of each sample with that of a sample that was run under the same conditions except that no pretreatment was performed. V × Rμ was calculated. The results are shown in Table 1. R V R was judged to be good when it was 1.20 or more. Rμ was judged to be good when it was 0.90 or more. V When ×Rμ was 1.20 or more, it was rated as good, and when it was 1.40 or more, it was rated as even better.

[0150] [Table 1]

[0151] As can be seen from Table 1, the soft magnetic metal powder that underwent mechanochemical pretreatment had a high Rz value. Top 5 The powder magnetic cores manufactured using the soft magnetic metal powders of each example, which are 0.0 nm or less, have a withstand voltage ratio R V and the magnetic permeability ratio Rμ were excellent. V ×Rμ was also good.

[0152] In contrast, the soft magnetic metal powder of the comparative example, which was subjected to heat treatment as a pretreatment, had lower Rz and Ra than the soft magnetic metal powder that was not subjected to pretreatment. As a result, the powder cores produced using the soft magnetic metal powder that was subjected to heat treatment as a pretreatment were inferior in magnetic permeability ratio Rμ to the powder cores of the examples, and further, V ×Rμ was also inferior.

[0153] Although mechanochemical treatment was performed as a pretreatment, the comparative powder cores, which had too high Rz, had a lower withstand voltage ratio R V and the permeability ratio Rμ is poor, and furthermore, R V ×Rμ was also inferior.

[0154] The examples with Ra of 0.2 nm or more and 10 nm or less have higher withstand voltage and magnetic permeability than the examples with Ra exceeding 10 nm. V ×Rμ was also excellent.

[0155] (Experimental Example 2) The experiment was carried out under the same conditions as in Experimental Example 1, except that the prepared raw material metals were weighed so that the Fe content was 88.4 mass%, the Si content was 6.5 mass%, the B content was 2.6 mass%, and the Cr content was 2.5 mass%. The results are shown in Table 2. In Experimental Example 2, all of the obtained powders were composed of amorphous alloys.

[0156] [Table 2]

[0157] As can be seen from Table 2, the soft magnetic metal powders that were subjected to mechanochemical treatment as a pretreatment had a high Rz. Furthermore, the powder magnetic cores produced using the soft magnetic metal powders of each example having an Rz of 1.0 nm or more and 50.0 nm or less had a high withstand voltage ratio R V and the magnetic permeability ratio Rμ were excellent. V ×Rμ was also good.

[0158] In contrast, the soft magnetic metal powder of the comparative example, which was subjected to heat treatment as a pretreatment, had a lower Rz than the soft magnetic metal powder that was not subjected to pretreatment. As a result, the powder cores produced using the soft magnetic metal powder that was subjected to heat treatment as a pretreatment were inferior in magnetic permeability ratio Rμ to the powder cores of the examples, and further, V ×Rμ was also inferior.

[0159] Although mechanochemical treatment was performed as a pretreatment, the comparative powder cores, which had too high Rz, had a lower withstand voltage ratio R V and the permeability ratio Rμ is poor, and furthermore, R V ×Rμ was also inferior.

[0160] The examples with Ra of 0.2 nm or more and 10 nm or less have higher withstand voltage and magnetic permeability than the examples with Ra exceeding 10 nm. V ×Rμ was also excellent.

[0161] (Experimental Example 3) The conditions were the same as in Experimental Example 1, except that the raw metals were weighed to contain 81.7% by mass of Fe, 7.6% by mass of Si, 2.3% by mass of B, 7.3% by mass of Nb, and 1.1% by mass of Cu, and that heat treatment was performed at 600°C for 1 hour before pretreatment. The results are shown in Table 3. In Experimental Example 3, all of the powders obtained consisted of nanocrystalline alloys.

[0162] [Table 3]

[0163] As can be seen from Table 3, the soft magnetic metal powders that were subjected to mechanochemical treatment as a pretreatment had a high Rz. Furthermore, the powder magnetic cores produced using the soft magnetic metal powders of each example having an Rz of 1.0 nm or more and 50.0 nm or less had a high withstand voltage ratio R V and the magnetic permeability ratio Rμ were excellent. V ×Rμ was also good.

[0164] In contrast, the soft magnetic metal powder of the comparative example, which was subjected to heat treatment as a pretreatment, had a lower Rz than the soft magnetic metal powder that was not subjected to pretreatment. As a result, the powder cores produced using the soft magnetic metal powder that was subjected to heat treatment as a pretreatment were inferior in magnetic permeability ratio Rμ to the powder cores of the examples, and further, V ×Rμ was also inferior.

[0165] Although mechanochemical treatment was performed as a pretreatment, the comparative powder cores, which had too high Rz, had a lower withstand voltage ratio R V is inferior, and furthermore, R V ×Rμ was also inferior.

[0166] The examples with Ra of 0.2 nm or more and 10 nm or less have higher withstand voltage and magnetic permeability than the examples with Ra exceeding 10 nm. V ×Rμ was also excellent.

[0167] (Experimental Example 4) Except for the fact that the thickness of the coating was changed, the test was carried out under the same conditions as for Samples No. 15 and 17. The results are shown in Table 4.

[0168] [Table 4]

[0169] From Table 4, it was confirmed that the thicker the coating, the higher the withstand voltage, but the lower the magnetic permeability. V ×Rμ was good in all Examples, especially when the thickness of the coating portion was 10 nm or more and 50 nm or less.

[0170] (Experimental Example 5) The conditions were the same as for sample No. 17, except that the thickness of the oxide was changed by changing the holding time of the mechanochemical treatment. The results are shown in Table 5.

[0171] [Table 5]

[0172] From Table 5, it was confirmed that the thicker the oxidation part, the higher the withstand voltage, but the lower the magnetic permeability. V ×Rμ was good in all Examples, especially when the thickness of the oxidized portion was 10 nm or more and 20 nm or less.

[0173] (Experimental Example 6) Except for changing the composition of the powder coating material, the test was carried out under the same conditions as for Samples Nos. 15 and 17. The results are shown in Table 6.

[0174] Glass having the composition Bi2O3-ZnO-B2O3-SiO2 was used as the powder coating material for Samples No. 34 and 35. The specific composition of the glass was 40-60 mass% Bi2O3, 10-15 mass% ZnO, 15-25 mass% B2O3, 15-20 mass% SiO2, and the remainder were minor components.

[0175] Glass having the composition BaO-ZnO-B2O3-SiO2-Al2O3 was used as the powdered coating material for Samples No. 36 and 37. The specific composition of the glass was 35-40 mass% BaO, 30-40 mass% ZnO, 5-15 mass% B2O3, 5-15 mass% SiO2, 5-15 mass% Al2O3, and the remainder were minor components.

[0176] [Table 6]

[0177] From Table 6, it can be seen that the same tendency was observed even when the composition of the coating portion was changed. [Explanation of symbols]

[0178] 1...Soft magnetic metal particles 2...metal particles 2a…interface 11...oxidized part 12...Covering part 50...Mixture 100...Powder coating device 101...Rotor 102...Press head

Claims

1. A soft magnetic metal powder containing soft magnetic metal particles, the soft magnetic metal particles have metal particles and oxidized portions coating the metal particles, the soft magnetic metal particles have a composition expressed by a composition formula Fe(1-d)Sid in terms of atomic ratio, and satisfy the relationship 0.001≦d≦0.400; A composition expressed by the atomic ratio formula (Fe (1-β) Cr β ) (1-(b+d)) B b Si d , where 0.025≦b≦0.400, 0.001≦d≦0.400, 0.410≦1-(b+d)≦0.974, and 0<β{1-(b+d)}≦0.0600 are satisfied, or It has a composition represented by the atomic ratio formula (Fe(1-β)Cuβ)(1-(a+b+d))Nb a B b Si d, and has a composition that satisfies 0.040≦a≦0.300, 0.025≦b≦0.400, 0.001≦d≦0.400, 0.410≦1-(a+b+d)≦0.934, and 0<β{1-(a+b+d)}≦0.0600, The soft magnetic metal powder has an uneven interface between the metal particle and the oxidized portion, and the maximum height Rz of the roughness of the interface between the metal particle and the oxidized portion is 1.0 nm or more and 50.0 nm or less.

2. 2. The soft magnetic metal powder according to claim 1, wherein the arithmetic mean roughness Ra of the interface is 0.2 nm or more and 10.0 nm or less.

3. 3. The soft magnetic metal powder according to claim 1, wherein the average thickness of the oxidized portion is 1.0 nm or more and 100 nm or less.

4. The soft magnetic metal powder according to any one of claims 1 to 3, wherein the soft magnetic metal particles further have a coating portion that coats the oxidized portion.

5. 5. The soft magnetic metal powder according to claim 4, wherein the coating portion has an average thickness of 1.0 nm or more and 100 nm or less.

6. A dust core comprising the soft magnetic metal powder according to any one of claims 1 to 5.

7. A magnetic part comprising the soft magnetic metal powder according to any one of claims 1 to 5.

8. An electronic device comprising the soft magnetic metal powder according to any one of claims 1 to 5.

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