Soft magnetic powder, magnetic core, magnetic component, and electronic device

Abstract

To provide soft magnetic powder capable of reducing magnetic loss.SOLUTION: When a predetermined region on the surface of the soft magnetic particle 10 is observed, at least one of light regions and dark regions are observed in a dispersed manner. The predetermined region 12 of the particle surface is divided into 9 * 9 grids, and in each grid, the ratio of the number of pixels in the bright region is calculated as the bright region ratio for each grid, and the standard deviation of the bright region ratio for each grid is 3% or more and 45% or less.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

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

[0002] Electronic components such as inductors, transformers, and choke coils are widely used in the power supply circuits of various electronic devices. These electronic components include a coil and a magnetic core placed inside the coil. In recent years, soft magnetic metal powder has been widely used as the material for the magnetic core, replacing the conventional ferrite.

[0003] This is because soft magnetic metal powder has higher saturation magnetization (saturation magnetic flux density) and superior DC bias characteristics compared to ferrite, making it suitable for miniaturizing electronic components (magnetic cores) (Patent Document 1).

[0004] However, when soft magnetic metal powder is used in a magnetic core, eddy currents are likely to occur within the magnetic core due to electrical conduction between the soft magnetic metal particles contained in the soft magnetic metal powder. In other words, when soft magnetic metal powder is used in a magnetic core, core loss (especially eddy current loss) is likely to occur. Core loss reduces the efficiency of the power supply circuit and increases the power consumption of electronic devices. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3342767 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a soft magnetic powder that can reduce magnetic loss. [Means for solving the problem]

[0007] As a result of extensive research into soft magnetic powders that can reduce magnetic loss, the inventors discovered that magnetic loss can be reduced by using soft magnetic powders that contain soft magnetic particles that, when the surface of the soft magnetic particles is observed, for example, using a backscattered electron image, show a mottled pattern on the surface, and thus completed the present invention.

[0008] That is, the soft magnetic powder according to one aspect of the present invention is A soft magnetic powder containing soft magnetic particles, When a predetermined region on the surface of the soft magnetic particle is observed, at least one of a bright region and a dark region is observed to be dispersed, Dividing the predetermined area into a 9×9 grid, and calculating the ratio of the number of pixels in the bright area in each grid as a bright area ratio for each grid; The standard deviation of the bright region ratio for each grid is 3% or more and 45% or less.

[0009] Such soft magnetic powder can reduce core loss in magnetic cores. Furthermore, this soft magnetic powder may be used to manufacture magnetic components other than magnetic cores, and in such cases, magnetic loss can also be reduced. The reason why magnetic loss, such as core loss, can be reduced is believed to be that the concentration distribution of specific elements, such as oxygen, on the surface of the soft magnetic particles is observed as a mottled pattern (dark or light regions), which appears as a standard deviation within a predetermined range.

[0010] Preferably, the standard deviation of the bright region ratio for each grid is 7% or more and 40% or less, which can further reduce magnetic losses such as core loss.

[0011] The observation of the predetermined area on the surface of the soft magnetic particle may be performed using an image obtained by trimming a backscattered electron image of the surface of the soft magnetic particle at the predetermined area and then binarizing the image.

[0012] The predetermined region may be a quadrangular region that includes the center of the soft magnetic particle and has a length on one side that is within a range of 1 / 2 to 1 / 6 of the outer diameter of the soft magnetic particle.

[0013] Preferably, the soft magnetic particles have an insulating coating on the surface thereof.

[0014] Preferably, the soft magnetic particles contain at least Fe.

[0015] A magnetic core according to one aspect of the present invention includes the soft magnetic powder described above.

[0016] A magnetic component according to one aspect of the present invention includes the soft magnetic powder described above.

[0017] An electronic device according to an aspect of the present invention includes the magnetic component described above. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic cross-sectional view of a coil device included in an electronic device according to one embodiment of the present invention. [Figure 2A] FIG. 2A is a photograph of a backscattered electron image of soft magnetic metal particles according to an example contained in soft magnetic metal powder for producing the coil device shown in FIG. [Figure 2B] FIG. 2B is a photograph of a backscattered electron image of soft magnetic metal particles according to a comparative example corresponding to FIG. 2A. [Figure 3A] FIG. 3A is an enlarged view of a main portion of the surface of the soft magnetic metal particle shown in FIG. 2A. [Figure 3B] FIG. 3B is an enlarged view of a main part of the surface of the soft magnetic metal particle shown in FIG. 2B. [Figure 4A] FIG. 4A is a diagram of the image shown in FIG. 3A after it has been subjected to binarization processing. [Figure 4B] FIG. 4B is a diagram of the image shown in FIG. 3B after it has been subjected to binarization processing. [Figure 5A] FIG. 5A shows the image shown in FIG. 4A after adding a grid. [Figure 5B]FIG. 5B shows the image shown in FIG. 4B after adding a grid. [Figure 6] FIG. 6 is a schematic diagram showing a method for producing soft magnetic particles according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following describes the embodiments.

[0020] First embodiment 1, a coil component 1 included in an electronic device according to this embodiment is used as, for example, an inductor or a choke coil, and has a magnetic core 2 as a magnetic component. In this embodiment, a coil 5 is embedded inside the magnetic core 2, and ends 5a and 5b of the coil 5 are drawn out to the end faces of the magnetic core 2, respectively.

[0021] Furthermore, external electrodes 7 and 9 are formed on both end surfaces of the magnetic core 2 along the X-axis, respectively, and the pair of external electrodes 7 and 9 are electrically connected to the ends 5a and 5b of the coil 5, respectively.

[0022] In this embodiment, the magnetic core 2 only needs to maintain a predetermined shape, and its external dimensions and shape are not particularly limited. The magnetic core 2 is manufactured using soft magnetic powder having soft magnetic metal particles 10, for example, as shown in FIG. 2A. In this embodiment, the magnetic core 2 includes soft magnetic powder having soft magnetic metal particles 10 and a resin, and the soft magnetic powder is dispersed in the resin. In other words, the soft magnetic powder is bound together via the resin, thereby forming the predetermined shape of the magnetic core 2.

[0023] The resin material is not particularly limited, and preferably includes a thermosetting resin such as epoxy resin. The magnetic core 2 may also include a modifier to prevent contact between the soft magnetic metal particles. Polymeric materials such as polyethylene glycol (PEG), polypropylene glycol (PPG), and polycaprolactone (PCL) can be used as the modifier, and a polymeric material having a polycaprolactone structure is preferred. Examples of polymers having a polycaprolactone structure include urethane raw materials such as polycaprolactone diol and polycaprolactone tetraol, or parts of polyester. The content of the modifier is preferably 0.025 wt% or more and 0.500 wt% or less of the total amount of the magnetic core 2. It is believed that the modifier described above is present by adsorbing to coat the surfaces of the soft magnetic metal particles 10.

[0024] The total area ratio of the soft magnetic powder including the soft magnetic metal particles 10 in the cross section of the magnetic core 2 is not particularly limited, but is, for example, 50% to 95%. This total area ratio of the soft magnetic powder corresponds to the filling rate of the soft magnetic powder in the magnetic core 2, and can be calculated by analyzing the cross section of the magnetic core 2 using an electron microscope such as an SEM (scanning electron microscope) or an STEM (scanning transmission electron microscope).

[0025] For example, any cross section of the magnetic core 2 is divided into multiple consecutive fields of view and observed, and the area of ​​each soft magnetic metal particle 10 included in each field of view is measured. Then, the total area of ​​the soft magnetic powder is divided by the total area of ​​the observed fields of view to calculate the total area percentage (%) of the soft magnetic powder. In this cross-sectional analysis, the total area of ​​the fields of view must be at least 1,000,000 μm 2 It is preferable to set the following.

[0026] The soft magnetic powder contained in the magnetic core 2 may be soft magnetic metal particles 10, or may contain other soft magnetic particles with different particle diameters, compositions, material states, etc. The weight ratio of the soft magnetic metal particles 10 of this embodiment in the soft magnetic powder contained in the core 2 is not particularly limited, but is preferably 20 wt% or more (including 100 wt%), more preferably 50 wt% or more, or even preferably 60 to 100 wt%. The area ratio of the soft magnetic metal particles 10 of this embodiment in the soft magnetic powder contained in the core is also not particularly limited, but is preferably 20% or more (including 100%), more preferably 50% or more, or even preferably 60% to 100%.

[0027] The particle size of the soft magnetic metal particles 10 is not particularly limited, but is preferably 1 to 50 μm, and more preferably 10 to 40 μm. The particle size can be determined, for example, by laser diffraction.

[0028] In the soft magnetic powder, the soft magnetic metal particles 10 may be composed of two particle groups (large particles and small particles) with different average particle diameters, and the particle size distribution of the soft magnetic metal particles 10 may have two peaks. Alternatively, the soft magnetic metal particles 10 may be composed of three or more particle groups (for example, large particles, medium particles, and small particles) with different average particle diameters, and the particle size distribution of the soft magnetic metal particles 10 may have three or more peaks.

[0029] The circularity of the soft magnetic metal particles 10 is not particularly limited, but is preferably 0.70 or more, or 0.80 or more, and more preferably 0.90 or more. The higher the circularity of the soft magnetic metal particles 10 with a relatively large particle diameter, the more the withstand voltage and DC bias characteristics can be improved. The circularity of the particles 10 can be determined, for example, by calculating the area of ​​each particle 10 photographed as S L , where L is the perimeter of each particle, and 2(πS L ) 1 / 2 The circularity of a perfect circle is 1, and the closer the circularity is to 1, the higher the sphericity of the particle.

[0030] In this embodiment, the composition and material state of the soft magnetic metal particle 10 are not particularly limited and may be a crystalline structure, an amorphous structure, or a nanocrystalline structure. Here, "amorphous (non-crystalline) structure" refers to a material state in which there is almost no long-range order like in crystals and the degree of amorphization X is 85% or more. Amorphous structures include structures that are solely amorphous and structures consisting of heteroamorphous materials. A heteroamorphous structure refers to a structure in which primary crystallites exist in an amorphous state, and the average diameter of the primary crystallites in a heteroamorphous structure is preferably 0.1 nm or more and 10 nm or less.

[0031] Furthermore, "nanocrystalline structure" refers to a material state in which the degree of amorphization X is less than 85% and the average crystallite diameter is 0.5 nm or more and 30 nm or less. The maximum diameter of the crystallites in the nanocrystalline structure is preferably 100 nm or less. On the other hand, a crystalline structure has a structure different from an amorphous structure or a nanocrystalline structure. "Crystalline structure" refers to a material state in which the degree of amorphization X is less than 85% and the average crystallite diameter is 100 nm or more.

[0032] The material state of the particles 10 (i.e., the degree of amorphism X and crystallite size) can be determined by structural analysis using various electron microscopes such as SEM, TEM, and STEM, electron diffraction, XRD (X-ray diffraction), or EBSD (electron backscatter diffraction). For example, crystalline and amorphous portions can be visually distinguished in an EBSD orientation mapping image, and the degree of amorphism X can be calculated from the area ratio. Furthermore, the average crystallite diameter can be measured by analyzing a bright-field image from an electron microscope. Furthermore, if no crystalline spots are identified by electron diffraction, the particles being measured can be determined to have an amorphous structure.

[0033] There are no particular limitations on the composition of the crystalline particles 10. Examples of soft magnetic metals (crystalline metal magnetic materials) having a crystalline structure include pure iron such as carbonyl iron, Co, Fe-Ni alloys, Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-Al-Ni alloys, Fe-Ni-Si-Co alloys, Fe-Co alloys, Fe-Co-V alloys, Fe-Co-Si alloys, Fe-Co-Si-Al alloys, and Co alloys.

[0034] There are no particular limitations on the composition of the amorphous or nanocrystalline particles 10. For example, examples of soft magnetic alloys having a nanocrystalline structure or an amorphous structure include Fe-Si-B alloys, Fe-Si-BC alloys, Fe-Si-BC-Cr alloys, Fe-Nb-B alloys, Fe-Nb-BP alloys, Fe-Nb-B-Si alloys, Fe-Co-PC alloys, Fe-Co-B alloys, Fe-Co-B-Si alloys, Fe-Si-B-Nb-Cu alloys, Fe-Si-B-Nb-P alloys, Fe-Co-BP-Si alloys, Fe-Co-BP-Si alloys, Fe-Co-BP-Si-C alloys, Fe-Co-BP-Si-C-Cr alloys, Fe-Co-BP-Si-Cr alloys, Co-Fe-Nb-BP-Si alloys, and Co-Nb-BP-Si alloys. The composition of the soft magnetic metal particles 10 can be analyzed using, for example, an EDX device attached to an electron microscope or an EPMA.

[0035] 2A, when the surface of the soft magnetic metal particles 10 contained in the soft magnetic powder of this embodiment is observed using a backscattered electron image of an SEM, at least one of bright and dark regions is observed to be dispersed in a mottled pattern. In order to quantitatively evaluate the surface state of the particles 10 observed to be dispersed in a mottled pattern, the following method is used in this embodiment.

[0036] First, determine the volumetric particle size distribution of the soft magnetic powder to be observed, and observe particles with a particle diameter of D50, which is the median value of the particle size distribution, using a backscattered electron image from an SEM. There is no particular limit to the number of particles to be observed, but for example, 20 particles can be used. When photographing, use the auto-brightness and auto-contrast functions, and adjust the brightness and contrast so that the brightness values ​​(horizontal axis) in the brightness histogram of the photographed area are distributed across the entire range.

[0037] The imaging conditions for the device are, for example, as follows: acceleration voltage is 5 kV, working distance (WD) is 10 mm, spot intensity is 30, and BSE-ALL images are taken.

[0038] The diameter D of the photographed particle 10 is determined by image processing, and a predetermined quadrangular region 12 including the center of the particle 10 and having a length of one side within a range of 1 / 2 to 1 / 6 of the outer diameter D is trimmed. In this embodiment, a regular quadrangular predetermined region 12 having a length of D / 4 is trimmed.

[0039] The purpose of trimming is to ensure accurate binarization in the next step. If the entire particle 10 were binarized without trimming, the brightness of the image would differ between the center and the outer edge of the particle, making it difficult to accurately perform the binarization. Figure 3A shows an example of an image after trimming a predetermined region 12 of the particle 10 shown in Figure 2A.

[0040] After trimming, binarization preprocessing is performed as necessary, and then the image shown in FIG. 3A is binarized. Examples of binarization preprocessing include brightness histogram equalization. When photographing particles, the images are photographed so that the brightness histogram is flat, but trimming can change the brightness histogram. Therefore, to facilitate the subsequent binarization process, it is preferable to perform brightness histogram equalization (preferably adaptive histogram equalization).

[0041] Then, the image shown in Fig. 3A is binarized. Although there are no particular limitations on the binarization process, it is preferable to use Otsu's binarization process. This binarization process can automatically determine the threshold that maximizes the degree of separation in the luminance histogram.

[0042] FIG. 4A shows an image after binarization of the image shown in FIG. 3A. In this embodiment, the binarized image is divided into, for example, a 9×9 grid as shown in FIG. 5A. The ratio of the number of pixels in bright regions in each grid is calculated as the bright region ratio for each grid, and the standard deviation of the bright region ratio for each grid is determined. In particle 10 of this embodiment, the standard deviation of the bright region ratio for each grid is 3% to 45%, preferably 7% to 40%, or preferably 15% to 30%.

[0043] In this embodiment, the average value of the bright region ratio for each grid (average value of 9×9=81 grids) is preferably 10 to 95%, and more preferably 20 to 80%.

[0044] As shown in Fig. 2B, when a backscattered electron image of the soft magnetic paraxial particles 10a contained in the conventional soft magnetic powder (a conventional example (comparative example)) is obtained under the same conditions as Fig. 2A, no mottled pattern of dispersed bright or dark regions is observed on the surface. Therefore, when the particles are trimmed under the same conditions as Fig. 3A as shown in Fig. 3B, binarized under the same conditions as Fig. 4A as shown in Fig. 4B, and divided into grids under the same conditions as Fig. 5A as shown in Fig. 5B, the standard deviation of the bright region ratio for each grid is less than 3.

[0045] A soft magnetic powder having soft magnetic metal particles 10 shown in FIG. 2A can reduce the core loss of, for example, the magnetic core 2 shown in FIG. 1. This soft magnetic powder may also be used to manufacture magnetic components other than the magnetic core 2, and in such cases, magnetic loss can also be reduced. The reason that magnetic losses such as core loss can be reduced is thought to be that the concentration distribution of specific elements such as oxygen on the surface of the soft magnetic metal particles 10 is observed as a mottled pattern (dark or light regions), which appears as a standard deviation within a predetermined range.

[0046] An example of a method for manufacturing the magnetic core 2 according to this embodiment will now be described. First, a soft magnetic powder (raw material powder) containing soft magnetic metal particles 10 shown in Fig. 2A is prepared. There are no particular limitations on the method for producing the raw material powder, and an appropriate production method may be adopted depending on the desired particle composition.

[0047] For example, the raw material powder may be produced by an atomization method such as water atomization or gas atomization. Alternatively, the raw material powder may be produced by a synthesis method such as a CVD method using at least one of evaporation, reduction, and thermal decomposition of metal salts. The raw material powder may also be produced by an electrolysis method or a carbonyl method, or by pulverizing a ribbon-shaped or thin plate-shaped starting alloy. In particular, raw material powder containing particles 10 with an amorphous structure or nanocrystalline structure is preferably produced by a quenching gas atomization method.

[0048] In addition, in this embodiment, when forming a mottled pattern of light or dark regions as shown in Figure 2A without performing a special coating treatment on the surface of the soft magnetic metal particles 10, it is preferable to use a special gas atomization method as shown in Figure 6.

[0049] In this gas atomization method, molten metal (particle raw material) 10α dripping from a nozzle is atomized by the spray of high-pressure gas into metal droplets 10β, and before these droplets 10β are rapidly cooled and solidified, mist water is sprayed onto them as indicated by the white arrow A. The oxygen concentration of the gas atomization atmosphere is preferably fixed at, for example, 1%, and the mist water is sprayed at a flow rate greater than 0 mL / min and up to 1000 mL / min. The metal droplets 10β sprayed with the mist water are rapidly cooled, for example, by cooling water flowing spirally along the inner surface of a cylinder (not shown) located at the bottom of FIG. 6.

[0050] By producing soft magnetic metal particles 10 using this method, a mottled pattern of light and dark regions with a predetermined standard deviation is observed on the surface of the particles 10, as shown in Figure 2A. This is thought to result in a high core loss reduction effect. The reason for this is thought to be that the atomized water spray causes unevenness in the oxygen concentration in the oxide film formed on the surface of the particles 10, which contributes to the core loss reduction effect.

[0051] The particle size of the raw material powder can be adjusted by the powder production conditions and various classification methods. When particles 10 having a nanocrystalline structure are to be obtained, it is preferable to subject the raw material powder to a heat treatment in the range of, for example, 400 to 700°C to control the crystal structure.

[0052] The raw material powder may also contain one or more types of soft magnetic particles having an average particle size and / or composition different from the average particle size of the soft magnetic metal particles 10 shown in Fig. 2A. Alternatively, a raw material powder containing large particles and a raw material powder containing small particles may be obtained by producing a raw material powder containing particles 10 having a wide particle size distribution and classifying the raw material powder.

[0053] A method for manufacturing the magnetic core 2 using raw material powder of the soft magnetic metal particles 10 will be described below. First, the raw material powders on which the insulating coating has been formed and a resin raw material (such as a thermosetting resin) are kneaded to obtain a resin compound. This kneading step can be performed using various kneading machines such as a kneader, planetary mixer, rotation-revolution mixer, or twin-screw extruder, and modifiers, preservatives, dispersants, non-magnetic powders, etc. may be added to the resin compound.

[0054] Next, the resin compound is filled into a mold and compression molded to obtain a green body. Note that a coil 5 may be placed inside the mold beforehand. The molding pressure at this time is not particularly limited. Note that the total area ratio of the soft magnetic metal particles 10 in the magnetic core 2 can be controlled by the amount of resin 20 added, but it can also be controlled by the molding pressure. When a thermosetting resin is used as the resin 20, the above green body is kept at 100°C to 200°C for 1 hour to 5 hours to cure the thermosetting resin.

[0055] The above steps result in a magnetic core 2 as shown in Figure 1. Terminal electrodes 7 and 9, which are baked electrodes coated with a conductive paste film, are formed on each end face of the magnetic core 2 in the X-axis direction. A plating film may be formed on the surfaces of the terminal electrodes 7 and 9.

[0056] The use of the coil component 1 having the magnetic core 2 shown in Fig. 1 is not particularly limited, but it is suitable, for example, for a power inductor used in a power supply circuit. Note that the magnetic component including the magnetic core 2 is not limited to the form shown in Fig. 1, and may be a magnetic component in which a wire is wound a predetermined number of times around the surface of the magnetic core 2 having a predetermined shape.

[0057] Second embodiment In this embodiment, an insulating coating film is formed on the surface of soft magnetic metal particle 10 shown in Figure 2A by an insulating coating process, and a mottled pattern of light or dark regions with a predetermined range of standard deviation is observed on the surface of particle 10. Except for this, the same configuration and effects as those of the first embodiment are provided below. Differences from the first embodiment will be described in detail below, and common parts will not be described.

[0058] The soft magnetic metal particles 10 of this embodiment have an insulating coating film covering the particle surface. The insulating coating film may cover the entire particle surface, or may cover only a portion of the particle surface. In either case, a mottled pattern of bright or dark regions with a predetermined standard deviation is observed on the surface of the particle 10 on which the insulating coating film is formed, as shown in FIG. 2A, for example.

[0059] The material of the insulating coating film is not particularly limited and may include a coating formed by oxidation of the particle surface and / or a coating containing an inorganic material such as BN, SiO2, MgO, Al2O3, phosphate, silicate, borosilicate, bismuthate, or various glasses. From the viewpoint of suppressing a decrease in the resistivity of the magnetic core 2, it is preferable that each insulating coating film has an oxide glass coating containing one or more elements selected from P, Si, Bi, and Zn. In the oxide glass coating, when the total amount of elements contained in the coating excluding oxygen is taken as 100 wt%, the total amount of one or more elements selected from P, Si, Bi, and Zn is preferably the largest, more preferably 50 wt% or more, and even more preferably 60 wt% or more.

[0060] Examples of oxide glass coatings include phosphate (P2O5)-based glass coatings, bismuthate (Bi2O3)-based glass coatings, and borosilicate (B2O3-SiO2)-based glass coatings. Examples of phosphate-based glasses include P-Zn-Al-O-based glasses and P-Zn-Al-RO-based glasses (where "R" represents one or more elements selected from alkali metals), with phosphate-based glass coatings preferably containing 50 wt% or more of P2O5. Examples of bismuthate-based glasses include Bi-Zn-B-Si-O-based glasses and Bi-Zn-B-Si-Al-O-based glasses, with bismuthate-based glass coatings preferably containing 50 wt% or more of Bi2O3. Examples of borosilicate glasses include Ba-Zn-B-Si-Al-O-based glasses, with borosilicate glass coatings preferably containing 10 wt% or more of B2O3.

[0061] Furthermore, each insulating coating film may have a single-layer structure or a multi-layer structure. An example of a multi-layer structure is a laminated structure including an oxide layer on the particle surface and an oxide glass layer covering the oxide layer. When the insulating coating film has a multi-layer structure, the total thickness of each layer is defined as the thickness of the insulating coating film. Furthermore, the composition of the insulating coating film can be analyzed by, for example, EDX, EPMA, or EELS (electron energy loss spectroscopy).

[0062] The average thickness of the insulating coating film is not particularly limited, and is preferably, for example, 0.5 nm to 200 nm, and more preferably 1 nm to 100 nm. The thickness of the insulating coating film does not necessarily have to be uniform.

[0063] The method for forming an insulating coating film on the particles 10 is not particularly limited, and examples include heat treatment, phosphate treatment, mechanical alloying, silane coupling treatment, or hydrothermal synthesis. An appropriate coating formation process can be selected depending on the type of insulating coating film to be formed.

[0064] For example, if the soft magnetic powder contains a phosphate-based insulating coating, it can be formed by phosphate treatment. Specifically, first, phosphoric acid or a phosphate containing an additive element (α, β) is dissolved in a solvent such as water or alcohol to prepare a phosphate solution. Then, the soft magnetic metal powder is impregnated with the solution, or the solution is sprayed onto the soft magnetic metal powder and dried, thereby forming a phosphate coating on the surface of the soft magnetic metal powder. Examples of additive elements include additive element α (alkali metal or alkaline earth metal) or additive element β (Zn, Al).

[0065] Furthermore, when the soft magnetic powder includes an insulating coating film of SiO2, the insulating coating film can be formed by spraying a solution containing a silane coupling agent serving as a Si source onto the soft magnetic metal powder, or by impregnating the soft magnetic metal powder with the solution, followed by drying and / or heat treatment. Examples of the silane coupling agent used in this case include tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), and hexyltrimethylsilane, with TEOS being preferred. Examples of solvents for dissolving the silane coupling agent include water, ethanol, acetone, and isopropyl alcohol, but there are no particular limitations. The thickness of the insulating coating can be controlled by the concentration of the silane coupling agent contained in the treatment solution, the amount sprayed, the impregnation treatment time, etc.

[0066] Furthermore, when the insulating coating film includes an oxide glass coating, the oxide glass coating film may be formed by a mechanochemical method using a mechanofusion apparatus. Specifically, in the coating formation process using the mechanochemical method, raw material powder including particles 10 and a powdered coating material including the constituent elements of the insulating coating film are introduced into a rotating rotor of the mechanofusion apparatus, and the rotating rotor is rotated.

[0067] A press head is installed inside the rotor, and when the rotor is rotated, the mixture of raw material powder and coating material is compressed in the gap between the inner wall surface of the rotor and the press head, generating frictional heat. This frictional heat softens the coating material, which then adheres to the surface of the particles 10 through compression, forming an oxide glass coating.

[0068] The thickness of the insulating coating film can be controlled based on the mixing ratio of the coating material, the rotation speed, the processing time, etc. The insulating coating film is preferably formed by mixing the powdered coating material containing the constituent elements of the insulating coating film with the particles 10 while applying mechanical impact energy, and can also be formed by mixing while applying impact, compression, and shear energy.

[0069] In this embodiment, in order to form the surface pattern shown in Fig. 2A, it is preferable to use a coating agent for the insulating coating film, which is made by blending insulating coating materials having oxide glasses with two or more different average particle sizes in a predetermined ratio. For example, it is preferable to use two types of glass frit, one of which has a volumetric particle size distribution D50 of 0.5 to 3 µm, and the other of which has a volumetric particle size distribution D50 of 10 to 20 µm.

[0070] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0071] For example, in the above-described embodiment, the magnetic core 2 as a magnetic component has a coil 5 therein, but in another embodiment, the magnetic core may have a coil wound around it without having a coil 5 therein. For example, the coil component included in the electronic device of this embodiment is not limited to an inductor or choke coil having a magnetic core with a coil disposed therein, but may also be an inductor, choke coil, transformer, noise filter, or the like having a magnetic core with a coil wound around it. Furthermore, at least a portion of the magnetic core may be composed only of the magnetic powder of this embodiment, without including resin.

[0072] Furthermore, the magnetic component is not limited to a magnetic core, but may be a magnetic sheet, etc. That is, the magnetic component included in the electronic device is not limited to a magnetic core, but may also be a magnetic sheet, etc. [Example]

[0073] The following provides a more detailed explanation based on examples, but is not limited to these examples.

[0074] Experimental Example 1 Powder A was prepared using a quenched gas atomization method. The powder was an Fe-Co-BP-Si-Cr alloy powder (57.4Fe-24.6Co-11B-5.0P-1.0Si-1.0Cr (atomic ratio)) with an average particle size of 25 μm. Powder B was prepared using a pure Fe powder with an average particle size of 0.8 μm.

[0075] The prepared powder A was subjected to a coating process using a mechanofusion device (AMS-Lab, manufactured by Hosokawa Micron Corporation) to form an insulating coating film of P-Zn-Al-O-based oxide on the surface to a thickness of 10 nm. In the insulating coating process, the amount of oxide glass P with a volumetric particle size distribution D50 of 1 μm and / or oxide glass Q with a volumetric particle size distribution D50 of 15 μm added was varied in the weight ratio range of 100:0 to 0:100 shown in Table 1, to obtain soft magnetic metal powders of sample numbers 1 to 15.

[0076] Next, powder A and powder B were kneaded with epoxy resin to obtain a resin compound. The amount of epoxy resin added (resin amount) in the resin compound was 3.0 parts by mass per 100 parts by mass of the metal magnetic particles (i.e., the sum of powder A and powder B). The mixing ratio of powder A to powder B was 80:20 by mass.

[0077] Next, the resin compound was filled into a mold and pressurized to obtain a toroidal-shaped compact. The molding pressure was controlled so that the magnetic core's magnetic permeability (μi) was 30. The compact was then heat-treated at 180°C for 60 minutes to harden the epoxy resin in the compact, resulting in a toroidal-shaped magnetic core (outer diameter 11 mm, inner diameter 6.5 mm, thickness 2.5 mm).

[0078] The soft magnetic metal powder (powder A) and the magnetic core thus produced were evaluated as follows.

[0079] (Evaluation of surface condition) Backscattered electron images (particle backscattered electron images) of several particles of Powder A were obtained using an electron microscope (Hitachi High-Tech: SU-5000). The imaging conditions were an accelerating voltage of 5 kV, a working distance (WD): 10 mm, and a spot intensity of 30, with brightness and contrast adjusted using the auto-brightness and auto-contrast functions. Particles to be observed were randomly selected from those with a particle size between 90 and 110% of the D50 of the volume-based particle size distribution of the powder.

[0080] In the example, when a backscattered electron image of a particle in which the entire particle to be measured is observed in the center of the screen as shown in Fig. 2A, a mottled pattern of bright and dark areas was observed. In order to quantitatively express the mottled pattern, the following procedure was performed.

[0081] A square predetermined area 12 with a side length of D / 4 was trimmed to align with the center of a particle 10 to be measured, with the particle diameter D. An example of the image after trimming is shown in Figure 3A. The trimmed image was subjected to adaptive histogram equalization and then Otsu's binarization, resulting in the image shown in Figure 4A.

[0082] For example, as shown in Figure 5A, the binarized image was divided into a 9 × 9 grid, and the area ratio of bright regions was calculated for each grid. Then, based on the distribution data of the bright region ratio obtained, the standard deviation of the area ratio of bright regions in the photographed particles was calculated.

[0083] The above procedure was repeated for 20 particles, and the average of the standard deviations determined for each particle was used to calculate the standard deviation of the bright region ratio in powder A, which was taken as the standard deviation of particle A: σA. The results are shown in Table 1.

[0084] The backscattered electron image of the particles belonging to Powder A of Sample No. 1 shown in Table 1 was similar to the image shown in FIG. 2B.

[0085] (Core loss evaluation) First, polyurethane copper wire (UEW wire) was wound around a toroidal magnetic core. Then, the magnetic permeability of the magnetic core was measured at a frequency of 1 MHz using an LCR meter (Agilent Technologies 4284A). The magnetic permeability of each magnetic core was adjusted to 30.

[0086] Core loss of each magnetic core (unit: kW / m 3) was measured using a BH analyzer (SY-8218 manufactured by Iwatsu Measurement Co., Ltd.). The magnetic flux density when measuring the core loss was set to 10 mT, and the frequency was set to 3 MHz. In addition, for the magnetic cores of sample numbers 1 to 15, the improvement rate (reduction rate) of core loss relative to the magnetic core of sample number 1, in which the ratio of oxide glass P to oxide glass Q was 100:0, was determined. In this example, an improvement rate of 5% or more was rated as "good," 10% or more as "particularly good," and 15% or more as "even better." The results are shown in Table 1.

[0087] [Table 1]

[0088] As shown in Table 1, the standard deviation σ A It was found that the magnetic core molded using the soft magnetic powder containing the powder A of the example in which the bright regions are suitably distributed so that the standard deviation σ satisfies a predetermined range can reduce the core loss compared to the magnetic core of the comparative example. In this example, by changing the mixing ratio of oxide glasses with different particle sizes, unevenness is generated in the concentration distribution of the coating component on the particle surface, and the standard deviation σ A It is thought that this can be controlled.

[0089] Experimental Example 2 For powder A, soft magnetic metal powders and magnetic cores of sample numbers 16 to 29 were prepared in the same manner as sample number 1 or sample number 8, except that the amount of coating material was adjusted so that the thickness of the insulating coating film would be the value shown in Table 2, and evaluations were carried out in the same manner as in Experimental Example 1. The results are shown in Table 2.

[0090] [Table 2]

[0091] As shown in Table 2, even when the thickness of the insulating coating is different, it was found that the magnetic core molded using soft magnetic powder containing powder A, in which the bright region is suitably distributed, can reduce core loss compared to the magnetic core of the comparative example.

[0092] Experimental Example 3 Soft magnetic metal powders of sample numbers 30 to 41 were produced in the same manner as sample number 1 or sample number 8, except that the production conditions for powder A were changed so that the average particle size of powder A would be the value shown in Table 3. For sample numbers 30 and 31, the molding pressure was controlled so that the magnetic core had a magnetic permeability of 20, and for sample numbers 32 and 33, the magnetic core was produced by controlling the molding pressure so that the magnetic core had a magnetic permeability of 25. For sample numbers 34 to 41, magnetic cores were produced in the same manner as sample number 1 or sample number 8, and evaluations were performed in the same manner as in Experimental Example 1. The results are shown in Table 3.

[0093] [Table 3]

[0094] As shown in Table 3, even when the particle diameter of Powder A was changed, it was confirmed that magnetic cores molded using soft magnetic powder containing Powder A of the embodiment, in which the bright regions are suitably distributed within a predetermined range, can reduce core loss compared to the magnetic cores of the comparative example.

[0095] Experimental Example 4 For powder A, except that the material of the insulating coating film was changed to the material shown in Table 4A, soft magnetic metal powders and magnetic cores of sample numbers 42 to 47 were produced in the same manner as sample number 1 or sample number 8, and evaluated in the same manner as in Experimental Example 1. The results are shown in Table 4A.

[0096] For sample numbers 48 and 49, a phosphate coating was formed by spraying a phosphate solution onto powder A of sample number 162 or sample number 169 (described below) and drying it. For sample numbers 50 and 51, a SiO2 coating was formed by spraying a solution containing tetraethoxysilane onto powder A of sample number 162 or sample number 169 (described below) and drying it. Soft magnetic metal powders and magnetic cores were prepared under the same conditions as sample number 1 or sample number 8, and the same evaluations as in Example 1 were performed. The results are shown in Table 4B.

[0097] [Table 4A]

[0098] [Table 4B]

[0099] As shown in Tables 4A and 4B, even when the type of insulating coating used in the insulating coating process to form the insulating coating film was changed, it was found that magnetic cores using the soft magnetic powder of the examples, in which the bright areas were suitably distributed, were able to reduce core loss compared to the magnetic cores of the comparative examples.

[0100] Experimental Example 5 Soft magnetic metal powders and magnetic cores of sample numbers 52 to 103 were prepared in the same manner as sample number 1 or sample number 8, except that the soft magnetic powders used for powder A were those whose materials are listed in Tables 5A and 5B, and evaluations were carried out in the same manner as in Experimental Example 1. The results are shown in Tables 5A and 5B. Powder A in sample numbers 52 to 67 was confirmed to have an amorphous structure. Powder A in sample numbers 68 to 79 was confirmed to have a nanocrystalline structure. Powder A in sample numbers 80 to 103 was confirmed to have a crystalline structure.

[0101] [Table 5A]

[0102] [Table 5B]

[0103] As shown in Tables 5A and 5B, even when the material of powder A was changed, it was found that magnetic cores molded using soft magnetic powder containing powder A of the embodiment in which the bright regions were suitably distributed could reduce core loss compared to the magnetic cores of the comparative examples.

[0104] Experimental Example 6 Soft magnetic metal powders and magnetic cores of sample numbers 104 to 109 were prepared in the same manner as sample number 1 or sample number 8, except that the mixing ratio of powder A and powder B was changed to the ratio shown in Table 6, and evaluations were carried out in the same manner as in Experimental Example 1. The results are shown in Table 6.

[0105] [Table 6]

[0106] As shown in Table 6, even when the mixing ratio of powder A and powder B was changed, it was found that magnetic cores molded using soft magnetic powder containing powder A in which the bright regions were suitably distributed could reduce core loss compared to the magnetic cores of the comparative examples.

[0107] Experimental Example 7 Soft magnetic metal powders and magnetic cores of sample numbers 110 to 115 were produced in the same manner as sample number 1 or sample number 8, except that the production conditions for powder B were changed so that the average particle size of powder B would be the value shown in Table 7, and evaluations were performed in the same manner as in Experimental Example 1. The results are shown in Table 7.

[0108] [Table 7]

[0109] As shown in Table 7, even when the particle diameter of Powder B was changed, it was confirmed that magnetic cores molded using soft magnetic powder containing Powder A of the embodiment, in which the bright regions are suitably distributed within a predetermined range, can reduce core loss compared to the magnetic cores of the comparative examples.

[0110] Experimental Example 8 Soft magnetic metal powders and magnetic cores of sample numbers 116 to 123 were prepared in the same manner as sample number 1 or sample number 8, except that powder B was made of the material listed in Table 8, and were evaluated in the same manner as in Experimental Example 1. The results are shown in Table 8.

[0111] [Table 8]

[0112] As shown in Table 8, even when the material of powder B was changed, it was found that magnetic cores molded using soft magnetic powder containing powder A in which the bright regions were suitably distributed could reduce core loss compared to the magnetic cores of the comparative examples.

[0113] Experimental Example 9 Soft magnetic metal powders and magnetic cores of sample numbers 124 to 133 were prepared in the same manner as sample number 1 or sample number 8, except that soft magnetic alloy powder C (56.0Fe-24.0Co-11.0B-6.0P-3.0Si (atomic ratio)) made of an FeCoBPSi-based material with an average particle size of 3 μm was mixed in addition to powders A and B in the proportions shown in Table 9, and evaluations were performed in the same manner as in Experimental Example 1. The results are shown in Table 9.

[0114] [Table 9]

[0115] As shown in Table 9, even when a single soft magnetic metal powder or a mixture of three or more types of soft magnetic metal powder is used, it was found that magnetic cores molded using soft magnetic powder containing powder A in which the bright regions are suitably distributed can reduce core loss compared to the magnetic cores of the comparative examples.

[0116] Experimental Example 10 For powder C, except that powder of the material shown in Table 10 was used, soft magnetic metal powders and magnetic cores of sample numbers 134 to 155 were produced in the same manner as sample number 128 or sample number 129, and evaluated in the same manner as in Experimental Example 1. The results are shown in Table 10.

[0117] [Table 10]

[0118] As shown in Table 10, even when the material of the soft magnetic metal powder for powder C was changed, it was found that the magnetic core molded using the soft magnetic powder having powder A in which the bright regions were suitably distributed could reduce core loss compared to the magnetic core of the comparative example.

[0119] Experimental Example 11 Soft magnetic metal powders and magnetic cores of sample numbers 156 to 161 were produced in the same manner as sample number 128 or sample number 129, except that the production conditions for powder C were changed so that the average particle size of powder C would be the value shown in Table 11, and evaluations were performed in the same manner as in Experimental Example 9. The results are shown in Table 11.

[0120] [Table 11]

[0121] As shown in Table 11, even when the particle diameter of powder C was changed, it was confirmed that magnetic cores molded using soft magnetic powder containing powder A of the embodiment, in which the bright regions are suitably distributed within a predetermined range, can reduce core loss compared to the magnetic cores of the comparative examples.

[0122] Experimental Example 12 For Powder C, similarly to Powder A, soft magnetic powder was used that was insulatingly coated with the coating material listed in Table 12 using oxide glass P and / or oxide glass Q. Soft magnetic metal powders and magnetic cores of Sample Nos. 162 and 163 were prepared in the same manner as Sample No. 128 or Sample No. 129, and evaluated in the same manner as in Experimental Example 1. The results are shown in Table 12.

[0123] [Table 12]

[0124] As shown in Table 12, it was found that the magnetic core molded using soft magnetic powder having powder A and powder C in which the bright areas are suitably distributed can reduce core loss compared to the magnetic core of the comparative example.

[0125] Experimental Example 13 As Powder A, Fe-Co-BP-Si-Cr alloy powder was produced by a special gas atomization method shown in Figure 6, in an atmosphere with an oxygen concentration of 1%, by spraying water in mist form at a rate of 0 to 1000 mL / min, and soft magnetic powder A was produced in the same manner as in Experimental Example 1 without performing an insulating coating treatment. Soft magnetic metal powders and magnetic cores of sample numbers 164 to 178 were produced in the same manner as in Example 1, and similar evaluations were performed. The results are shown in Table 13.

[0126] [Table 13]

[0127] As shown in Table 13, even without insulating coating, the standard deviation σ A It was found that a magnetic core molded using soft magnetic powder containing powder A of the example, in which the bright regions are suitably distributed so that the value satisfies a predetermined range, can reduce core loss compared to the magnetic core of the comparative example. [Explanation of symbols]

[0128] 1... Coil parts 2... Magnetic core (magnetic part) 5... Coil 5a... End 5b... End 7,9… External electrode 10,10a… Soft magnetic metal particles 10α… molten metal 10β…metal droplet 12... Predetermined area

Claims

1. A soft magnetic powder containing soft magnetic particles, When a predetermined region on the surface of the soft magnetic particle is observed, at least one of a bright region and a dark region is observed to be dispersed, Dividing the predetermined area into a 9×9 grid, and calculating the ratio of the number of pixels in the bright area in each grid as a bright area ratio for each grid; A soft magnetic powder in which the standard deviation of the bright region ratio for each grid is 3% or more and 45% or less.

2. 2. The soft magnetic powder according to claim 1, wherein the standard deviation of the bright region ratio for each grid is 7% or more and 40% or less.

3. The soft magnetic powder according to claim 1 or 2, wherein the observation of a predetermined area on the surface of the soft magnetic particle is carried out using an image obtained by trimming a backscattered electron image of the surface of the soft magnetic particle at the predetermined area and then binarizing the image.

4. The soft magnetic powder according to claim 1 or 2, wherein the predetermined region is a rectangular region including the center of the soft magnetic particle and having a length of one side within a range of 1 / 2 to 1 / 6 of the outer diameter of the soft magnetic particle.

5. 3. The soft magnetic powder according to claim 1, wherein the soft magnetic particles have an insulating coating film on their surfaces.

6. The soft magnetic powder according to claim 1 or 2, wherein the soft magnetic particles contain at least Fe.

7. A magnetic core comprising the soft magnetic powder according to claim 1 or 2.

8. A magnetic part comprising the soft magnetic powder according to claim 1 or 2.

9. An electronic device comprising the magnetic component according to claim 8.

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