Soft magnetic powder and method for producing the same, coil component using the soft magnetic powder, and method for producing magnetic material using the soft magnetic powder

Abstract

A soft magnetic powder comprises a core made of a soft magnetic metal material and an insulating film covering the surface of the core. The insulating film contains an insulating metal oxide and an iron component, and the iron component is embedded in the insulating film.

Description

Technical Field

[0001] The present invention relates to soft magnetic powder and a method for producing the same, a coil component containing the soft magnetic powder, and a method for producing a magnetic material using the soft magnetic powder. Background Art

[0002] Magnetic materials used in magnetic components such as coils require high electrical resistance. For example, Patent Document 1 describes a magnetic material powder characterized by adding metal powder to a solution containing at least one metal alkoxide and uniformly dispersing it. Distilled water is then added to the solution to hydrolyze the metal alkoxide, allowing hydroxide to adsorb on the surface of the metal powder. The powder is then filtered, dried, and heated.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 9-125111 Summary of the Invention

[0006] With the development of miniaturization of electrical appliances, there is also a need for miniaturization of electronic components. Compared with ferrite, metal magnetic bodies have excellent DC superposition characteristics and are therefore useful for the miniaturization of electronic components. When metal magnetic bodies are used in electronic components such as coil components, in order to ensure insulation and reduce magnetic loss (core loss), the surface of the metal magnetic body is sometimes subjected to insulation treatment. However, the inventors have found that it is difficult to increase the magnetic permeability when the surface of the metal magnetic body is subjected to insulation treatment. According to the research of the inventors, this problem tends to become particularly significant in applications that require high-frequency magnetic properties.

[0007] An object of the present invention is to provide a soft magnetic powder having high magnetic permeability and high electrical resistance, a method for producing the same, a coil component using the same, and a magnetic material using the same.

[0008] The present inventors conducted intensive research to solve the above-mentioned problems and found that by introducing an iron component into the insulating film covering the surface of a core made of a soft magnetic metal material, a soft magnetic powder with higher magnetic permeability and higher electrical resistance can be obtained, thereby completing the present invention.

[0009] According to one embodiment of the present invention, there is provided a soft magnetic powder having:

[0010] A core made of soft magnetic metal material, and

[0011] The insulating film covering the core surface,

[0012] The insulating film contains an insulating metal oxide and an iron component, and the iron component is embedded in the insulating film.

[0013] According to one embodiment of the present invention, there is provided a method for producing a soft magnetic powder, comprising:

[0014] A core composed of a soft magnetic metal material, an iron salt, a metal alkoxide, and at least one selected from a water-soluble polymer and a surfactant are mixed in a solvent to obtain a slurry; and

[0015] The slurry is dried to obtain a soft magnetic powder having a core and an insulating film covering the surface of the core.

[0016] According to one embodiment of the present invention, there is provided a coil component, comprising:

[0017] A magnetic core comprising the above-mentioned soft magnetic powder and a binder, and

[0018] Coil conductor.

[0019] According to one embodiment of the present invention, there is provided a method for manufacturing a magnetic material, comprising:

[0020] The soft magnetic powder is molded to obtain a molded body, and

[0021] The molded body is heat-treated to obtain a magnetic material.

[0022] The soft magnetic powder of the present invention can achieve both high magnetic permeability and high electrical resistance. Furthermore, the method for producing a soft magnetic powder of the present invention can produce a soft magnetic powder having both high magnetic permeability and high electrical resistance. Furthermore, the coil component of the present invention can be formed from a magnetic material having both high magnetic permeability and high electrical resistance. Furthermore, the method for producing a magnetic material of the present invention can produce a magnetic material having both high magnetic permeability and high electrical resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1a It is the STEM-EDX analysis result (C (carbon) element mapping result) of the cross section of the soft magnetic powder according to the embodiment of the present invention.

[0024] Figure 1b It is the STEM-EDX analysis result (the mapping result of the O (oxygen) element) of the cross section of the soft magnetic powder according to the embodiment of the present invention.

[0025] Figure 1c It is the STEM-EDX analysis result (the mapping result of Si (silicon) element) of the cross section of the soft magnetic powder which concerns on embodiment of this invention.

[0026] Figure 1d It is the STEM-EDX analysis result (Fe (iron) element mapping result) of the cross section of the soft magnetic powder according to the embodiment of the present invention.

[0027] Figure 2a This is a TEM image of a cross section of the soft magnetic powder according to the first embodiment of the present invention.

[0028] Figure 2b This is a TEM image of a cross section of the soft magnetic powder according to the first embodiment of the present invention.

[0029] Figure 3 It is a diagram schematically showing a coil component according to a second embodiment of the present invention.

[0030] Figure 4a It is a perspective view schematically showing a coil component according to a third embodiment of the present invention.

[0031] Figure 4b It is an exploded perspective view schematically showing a unit cell constituting a coil component according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0032] [First embodiment]

[0033] The following describes the soft magnetic powder of the first embodiment of the present invention. The soft magnetic powder of this embodiment has a core made of a soft magnetic metal material and an insulating film covering the surface of the core. It should be noted that in this specification, whether a film is an "insulating film" can be determined based on the volume resistivity. For example, a high resistance resistivity meter (Hiresta (registered trademark) -UX MCP-HT800) manufactured by Mitsubishi Chemical Analytech Co., Ltd. is used as a powder resistance measuring instrument, and the sample amount of the soft magnetic powder with an insulating film is set to 10g. The volume resistivity measured under a load of 20kN is 10 6 If the resistivity is greater than Ωcm, the film can be judged as an "insulating film". Similarly, in this specification, "insulating property" means that the volume resistivity is 10 6 Ωcm or more.

[0034] (core)

[0035] The type of soft magnetic metal material constituting the core is not particularly limited and can be appropriately selected according to the application, etc. The core is preferably composed of a soft magnetic metal material of the Fe series, Ni series or Co series. More specifically, the soft magnetic metal material constituting the core may be, for example, Fe, Fe-Ni alloy, Fe-Co alloy, Fe-Si alloy, Fe-Si-Cr alloy, Fe-Si-Al alloy or Fe-Si-B-Cr alloy. The average particle size of the core is preferably 20 μm or less, more preferably 10 μm or less, and further preferably 5 μm or less. By setting the average particle size of the core to a small particle size of 20 μm or less, a soft magnetic powder with a small particle size can be obtained. If the soft magnetic powder has a small particle size, the core loss at high frequencies can be reduced as described later. The average particle size of the core can be obtained by grinding to obtain a cross section of the soft magnetic powder, obtaining an electron microscope image of the cross section, and analyzing the obtained image using image analysis software.

[0036] (Insulating film)

[0037] The insulating film covers the surface of the core. The insulating film contains an insulating metal oxide and an iron component, and the iron component is embedded in the insulating film. Here, the insulating metal oxide and the iron component are different substances. In addition, "embedded" means that the entire surface of the iron component is embedded in the insulating film, but a portion of the iron component may also exist on the surface of the insulating film. In the case where the iron component is in particulate form, "embedded" means that the entire surface of the iron component particle is covered by the components (insulating metal oxide and organic matter) that constitute the insulating film, but for some iron component particles, a portion of their surface may be exposed on the surface of the insulating film.

[0038] The average thickness of the insulating film is preferably 10 nm to 100 nm, more preferably 20 nm to 40 nm. If the average thickness of the insulating film is 10 nm or more, more preferably 20 nm or more, it is easier to embed the iron component that helps improve the magnetic properties inside it. If the average thickness of the insulating film is 100 nm or less, more preferably 40 nm or less, the magnetic permeability of the soft magnetic powder can be further improved. The average thickness of the insulating film can be measured according to the following steps. First, the soft magnetic powder to be measured is embedded in a resin and ground, and a sample for STEM-EDX observation is made by FIB (focused ion beam) processing. Using this sample, a cross-section of the soft magnetic powder in three fields of view is photographed for one particle by STEM-EDX, and for each EDX image, the thickness of the insulating film is set and measured at any four points at equal intervals. The above measurement is performed on three particles, and the average value obtained from the thickness of the insulating film measured at all points (three fields of view × four points × three = 36 points) is defined as the "average thickness".

[0039] The soft magnetic powder of this embodiment has a core composed of a soft magnetic metal material coated with an insulating film, and the iron component, a magnetic substance, is embedded in the insulating film, resulting in higher magnetic permeability and higher electrical resistance. In other words, according to the soft magnetic powder of this embodiment, since the insulating film contains the iron component, a magnetic substance, it can suppress the degradation of magnetic properties while imparting insulating properties to the soft magnetic powder. Furthermore, since the core of the soft magnetic powder of this embodiment is coated with an insulating film, when the soft magnetic powder of this embodiment is molded to obtain a magnetic material, contact between the cores of the soft magnetic powder can be prevented, further reducing the magnetic loss of the magnetic material.

[0040] The above-mentioned effects of improving magnetic properties and increasing resistance are particularly useful in applications that require high-frequency magnetic properties. With the development of high-frequency switching frequencies such as DC / DC converters, inductors that reduce core losses caused by high-frequency switching are needed. By using soft magnetic powder with a small particle size as a magnetic material, core losses at high frequencies can be reduced. However, soft magnetic powder has a tendency to have a lower magnetic permeability as the particle size becomes smaller. Therefore, it is difficult to achieve both reduced core losses at high frequencies and high magnetic permeability. In contrast, the soft magnetic powder of this embodiment can achieve higher magnetic permeability even when the particle size of the soft magnetic powder is small because the insulating film covering the surface of the core composed of a soft magnetic metal material contains a magnetic iron component.

[0041] Whether the iron component is embedded in the insulating film can be confirmed by STEM-EDX (Scanning Transmission Electron Microscope - Energy Dispersive X-ray Analysis) in the following steps. First, the soft magnetic powder to be measured is embedded in resin and ground, and a sample for STEM-EDX observation is prepared by FIB processing. Using this sample, elemental mapping of the cross section of the insulating film is performed using a STEM-EDX device. An example of the elemental mapping result is shown in Figure 1a to Figure 1d The core used was a FeSi alloy with a weight ratio of Fe:Si=93.5:6.5. Figure 1a is the mapping result of the C (carbon) element, Figure 1b is the mapping result of the O (oxygen) element, Figure 1c is the mapping result of Si (silicon) element, Figure 1d is the mapping result of Fe (iron) element. Figure 1a to Figure 1d From the element mapping results, we can see that the area between the two dotted lines in the figure is the insulating film, and the area below the insulating film is the core. Figure 1d It can be seen that there is iron in the insulating film. Figure 1d As shown in FIG, when iron is detected in the insulating film, it can be said that the iron component is buried in the insulating film. Figure 1d , described later Figure 2a and Figure 2bAs shown in FIG, the iron component may be more distributed near the core than near the surface of the insulating film. It should be noted that when analyzing the iron content in the insulating film of the soft magnetic powder contained in the electronic component, it is possible to confirm whether the iron component is embedded by performing the above analysis on the cross section of the electronic component. Figure 1b and Figure 1c Since silicon and oxygen were detected at almost the same position, it was confirmed that the insulating film contained silicon oxide as the insulating metal oxide.

[0042] After the insulating film is formed, the iron component may be additionally imparted to the surface of the insulating film, so that the iron component may be present on the surface of the insulating film, but it is preferred that no iron component be present on the surface of the insulating film. That is, it is preferred that only components other than the iron component be present on the surface of the insulating film (for example, only insulating metal oxides and organic matter). If the iron component is present on the surface of the insulating film, there is a risk of reduced resistance of the soft magnetic powder, and also a risk of reduced moisture resistance. Whether the iron component is present on the surface of the insulating film can be confirmed by XPS (X-ray photoelectron spectroscopy). In the case where no peak from Fe is detected by XPS analysis of the insulating film, it can be determined that no iron component is present on the surface of the insulating film.

[0043] The iron component is a component containing the iron element. The iron component is preferably an oxide containing iron, more preferably iron oxide. In this case, the composition of the iron oxide (oxidation number of iron) is not particularly limited. The iron component can be a magnetic oxide such as hematite, hematite, and magnetite. Since the resistivity of iron oxide is higher than that of metallic iron, if the iron component is iron oxide, the insulation of the insulating film can be further improved. Whether the iron component is iron oxide can be confirmed by the above-mentioned element mapping. Figure 1b and Figure 1d As shown in FIG, when iron and oxygen are detected at almost the same position, the iron component is considered to be iron oxide.

[0044] The insulating film preferably contains particles of iron components. In other words, in the insulating film, the iron component preferably exists in the form of particles. The entire surface of the iron component particles is covered with the components (insulating metal oxides and organic matter) constituting the insulating film, and is dispersed in the insulating film. Whether the iron component exists in the form of particles can be confirmed by the above-mentioned element mapping and the transmission electron microscope (TEM) image of the cross section of the insulating film. An example of a TEM image of the cross section of the insulating film is shown in Figure 2a and Figure 2b .like Figure 2b As shown in FIG, in the TEM image, the region where lattice stripes are observed corresponds to particles of the iron component. The lattice stripes in the TEM image indicate the presence of crystallinity.

[0045] The average particle size of the particles of the iron component is preferably 5nm to 20nm. If the average particle size is 5nm or more, the relative magnetic permeability of the soft magnetic powder can be further improved. If the average particle size is 20nm or less, the particles of the iron component can be made smaller than the size of the magnetic region, and the magnetic loss can be further reduced. That is, the insulating film preferably contains nanoparticles of the iron component (crystals with a particle size of nanometers). The average particle size of the particles of the iron component can be obtained based on the TEM image according to the following steps. In the TEM image, for each of the 10 particles of the iron component, the major diameter (the longest diameter) and the minor diameter (the shortest diameter) are measured, and the average value of the major diameter and the minor diameter is used as the particle size of the particle. The average value of the particle sizes of the 10 particles obtained in this way is defined as the average particle size.

[0046] When calculated from the ratio of the weight of Fe in the insulating film to the weight of the core, the iron content in the insulating film is, for example, 0.3% to 5% by weight, preferably 0.5% to 3% by weight. An iron content of 0.5% or more by weight can further increase the magnetic permeability of the soft magnetic powder. An iron content of 3% or less by weight can further increase the electrical resistance. The iron content in the insulating film can be estimated from the amount of iron salt charged as a raw material for the iron content.

[0047] The insulating metal oxide constituting the insulating film is preferably a hydrolyzate of a metal alkoxide. As described below, the insulating film may contain an organic substance. An insulating film obtained by mixing a high-melting-point insulating metal oxide with a low-melting-point organic substance can be formed by utilizing the hydrolysis reaction of a metal alkoxide, which can produce the insulating metal oxide in a low-temperature process. Metal alkoxides are described in detail below. The insulating metal oxide is preferably at least one selected from titanium oxide, silicon oxide, aluminum oxide, and zirconium oxide. Furthermore, the insulating metal oxide is preferably amorphous.

[0048] The insulating film preferably further contains an organic substance. The organic substance is preferably at least one selected from a water-soluble polymer and a surfactant. As described later, when the insulating film is formed on the surface of the core, the water-soluble polymer and the surfactant help introduce the iron component into the insulating film. The water-soluble polymer and the surfactant are described in detail below.

[0049] The insulating film preferably contains at least one element selected from the group consisting of C, N, and P. These elements are derived from the water-soluble polymer and / or the surfactant.

[0050] Insulating films contain an insulating metal oxide and an organic substance (a water-soluble polymer and / or surfactant) in a mixed state (uniformly mixed at the molecular level). Whether the insulating metal oxide and the organic substance are mixed, and the constituent elements of the organic substance, can be determined by analyzing the insulating film using Fourier transform infrared spectrophotometry (FT-IR) and based on the shift in the OH group peak in the resulting IR spectrum. The constituent elements of the organic substance can also be determined by analyzing the soft magnetic powder using gas chromatography-mass spectrometry (GC-MS) and based on the detected organic components.

[0051] On the surface of the soft magnetic powder, a portion of the core may be exposed without being covered by the insulating film, but preferably the entire surface of the core is covered by the insulating film. The average coverage of the soft magnetic powder by the insulating film is preferably 90% or greater, more preferably 95% or greater, further preferably 99% or greater, and particularly preferably 100%.

[0052] (Method for producing soft magnetic powder)

[0053] Next, the method for producing the soft magnetic powder of the first embodiment will be described. The method for producing the soft magnetic powder of the first embodiment includes:

[0054] A core composed of a soft magnetic metal material, an iron salt, a metal alkoxide, and at least one selected from a water-soluble polymer and a surfactant are mixed in a solvent to obtain a slurry; and

[0055] The slurry is dried to obtain a soft magnetic powder having a core and an insulating film covering the surface of the core.

[0056] (Preparation of slurry)

[0057] First, a core composed of a soft magnetic metal material, an iron salt, a metal alkoxide, and at least one selected from a water-soluble polymer and a surfactant are mixed in a solvent to obtain a slurry.

[0058] The type and average particle size of the soft magnetic metal material constituting the core are as described above. It should be noted that the average particle size of the core of the raw material is considered to be substantially the same as the average particle size of the core in the obtained soft magnetic powder. The average particle size of the core of the raw material can be measured by using a laser diffraction particle size distribution measuring device or the like. In addition, the average particle size of the core of the raw material can be expressed by a volume-based median diameter.

[0059] (Iron Salt)

[0060] The iron salt becomes the raw material of the iron component contained in the insulating film. The iron salt can be selected from any iron salt such as inorganic salts such as ferric chloride, ferric sulfate, ferric nitrate, ferric phosphate and ferric nitrite and their hydrates, organic salts such as ferric oxalate, ferric acetate, ferric succinate and ferric malate, and composite salts. When alcohol is used as a solvent, the iron salt is preferably soluble in alcohol. Specifically, the iron salt is preferably selected from at least one of ferric chloride and ferric nitrate and their hydrates. As the iron salt, one iron salt can be used alone, or two or more iron salts can be used in combination. The iron salt is preferably added in a ratio of 0.1% to 20% by weight relative to the weight of the core.

[0061] (Metal alkoxide)

[0062] The metal alkoxide forms the raw material for the insulating metal oxide contained in the insulating film. By hydrolyzing the metal alkoxide in the slurry, an insulating film containing the insulating metal oxide is formed on the surface of the core. By utilizing the hydrolysis reaction of the metal alkoxide, an insulating film can be formed by mixing the insulating metal oxide with an organic substance (water-soluble polymer and / or surfactant).

[0063] Metal alkoxides are represented by the chemical formula M(OR) x (M: metal element, OR: alkoxy). The metal species M constituting the metal alkoxide can be at least one selected from Li, Na, Mg, Al, Si, K, Ca, Ti, Cu, Sr, Y, Zr, Ba, Ce, Ta and Bi. Among them, the metal alkoxide is preferably at least one alkoxide selected from Si, Ti, Al and Zr, more preferably Si. If the metal alkoxide is at least one alkoxide selected from Si, Ti, Al and Zr, an insulating metal oxide with higher strength and higher specific resistance can be formed. Furthermore, if the metal species M is Si, the metal alkoxide (Si(OR)4) is chemically more stable and therefore easier to handle during manufacturing.

[0064] The alkoxy group OR constituting the metal alkoxide is not particularly limited and may, for example, be an alkoxy group having 10 or fewer carbon atoms, particularly 5 or fewer, and more particularly 3 or fewer carbon atoms. The smaller the number of carbon atoms, the easier the hydrolysis reaction. The alkoxy group is preferably at least one selected from the group consisting of a methoxy group, an ethoxy group, and a propoxy group. Specifically, the metal alkoxide is preferably at least one selected from the group consisting of tetraethyl orthosilicate, titanium tetraisopropoxide, zirconium n-butoxide, and aluminum isopropoxide.

[0065] In the production method of this embodiment, a single metal alkoxide may be used, or two or more metal alkoxides may be used in combination. The metal alkoxide is preferably added at a ratio of 0.1 to 5% by weight relative to the weight of the core, calculated as the insulating metal oxide obtained.

[0066] (Water-soluble polymers and surfactants)

[0067] The water-soluble polymer and surfactant play a role in helping to introduce the iron component into the insulating film. The water-soluble polymer and surfactant have a ligand that can form a coordination compound with the Fe ion and a proton accepting group and / or a proton donating group that can form a hydrogen bond with the hydrolyzate of the metal alkoxide. Therefore, the water-soluble polymer and / or surfactant that is coordinated with the Fe ion forms a hydrogen bond with the hydrolyzate of the metal alkoxide, and the iron component is taken into the insulating film. As a ligand that can form a coordination compound with the Fe ion, for example, a compound having a functional group, etc. can be used, and the above-mentioned functional group has a lone pair of electrons that can donate electrons to the empty d orbital of the Fe ion.

[0068] The water-soluble polymer may be any of anionic, cationic and nonionic, and for example, a polymer selected from polyethyleneimine, polyvinylpyrrolidone, polyethylene glycol, polyacrylic acid, carboxymethylcellulose, hydroxypropylcellulose, polyacrylamide, poly(2-methyl-2- Among them, the water-soluble polymer is preferably selected from polyvinyl pyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, poly (2-methyl-2- At least one of oxazoline, polyethyleneimine, polyacrylic acid and carboxymethyl cellulose.

[0069] The surfactant may be anionic, cationic, nonionic, or amphoteric. For example, at least one selected from the group consisting of fatty acid salts, α-sulfo fatty acid ester salts, alkylbenzenesulfonates, alkyl sulfates, alkyl ether sulfate ester salts, alkyl triethanolamine sulfate, fatty acid diethanolamide, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, alkyl trimethylammonium salts, dialkyldimethylammonium chloride, alkylpyridinium chloride, and alkylcarboxybetaine can be used. Among these, the surfactant is preferably at least one selected from the group consisting of polyoxyalkylene styrylphenyl ether sodium phosphate, cetyltrimethylammonium bromide, and lauric acid diethanolamide.

[0070] As the organic matter that forms a coordination compound with the Fe ion, one water-soluble polymer can be used alone, or two or more water-soluble polymers can be used in combination. Alternatively, as the organic matter that forms a coordination compound with the Fe ion, one surfactant can be used alone, or two or more surfactants can be used in combination. Alternatively, as the organic matter that forms a coordination compound with the Fe ion, one or more water-soluble polymers and one or more surfactants can be used in combination. The organic matter that forms a coordination compound with the Fe ion is preferably added at a ratio of 0.1% to 1% by weight relative to the weight of the core.

[0071] (Solvent)

[0072] As the solvent, a solvent commonly used in the sol-gel method can be appropriately used. The solvent preferably contains an alcohol. When the solvent contains an alcohol, for example, methanol, ethanol, etc. can be used as the alcohol.

[0073] (catalyst)

[0074] To accelerate the hydrolysis rate of the metal alkoxide, a catalyst may be added as needed. Examples of catalysts include acidic catalysts such as hydrochloric acid, acetic acid, and phosphoric acid; alkaline catalysts such as ammonia, sodium hydroxide, and piperidine; and salt catalysts such as ammonium carbonate and ammonium acetate. Ammonia is preferred because it has low reactivity with the core and does not adversely affect the resistance of the insulating film even if it remains in the insulating film.

[0075] A slurry is obtained by mixing the above-mentioned raw materials. This slurry may include hydrolyzing the metal alkoxide. Mixing can be performed at room temperature, but it can also be performed while heating. The resulting slurry may be filtered and / or cleaned before drying, as described below. Filtration can be performed using, for example, a pressure filter such as a filter press, a vacuum filter such as a suction filter, or a centrifugal filter. Cleaning can be performed using, for example, acetone.

[0076] (dry)

[0077] Next, the slurry is dried to obtain a soft magnetic powder having a core and an insulating film covering the surface of the core. Drying can be performed at room temperature, but can also be performed while heating.

[0078] The above method can form an insulating film containing an insulating metal oxide and an iron component, wherein the iron component is embedded in the insulating film. The soft magnetic powder obtained by the above method has higher magnetic permeability and higher electrical resistance due to the presence of such an insulating film.

[0079] The insulating metal oxide is preferably at least one oxide selected from Si, Al, Ti, and Zr. If the insulating metal oxide is at least one oxide selected from Si, Al, Ti, and Zr, the strength and resistivity of the insulating film can be further improved.

[0080] [Second embodiment]

[0081] Next, a magnetic material and a coil component according to a second embodiment of the present invention will be described below.

[0082] The magnetic material of this embodiment comprises the soft magnetic powder of the embodiment of the present invention and a binder. As the binder, at least one selected from thermosetting resins such as epoxy resin, phenolic resin and silicone resin, and low-melting-point glass can be used. The magnetic material of this embodiment can be manufactured by adding a binder to the soft magnetic powder, molding it into a specified shape, and heating it to solidify it as needed. Molding can be performed, for example, by using a mold or filling it into the injected part. The heating temperature can be appropriately set according to the curing temperature of the binder used. For example, when epoxy resin is used as the binder, the epoxy resin can be cured by heating at a temperature of 150°C to 200°C. The magnetic material of this embodiment has higher magnetic permeability and higher electrical resistance.

[0083] Figure 3 A coil component according to a second embodiment is schematically shown. Figure 3 The coil component 1 shown includes a magnetic core 12 and a coil conductor 11, and the magnetic core 12 includes the soft magnetic powder and binder of an embodiment of the present invention. The magnetic core 12 is composed of a magnetic material including the soft magnetic powder and binder of an embodiment of the present invention. The coil conductor 11 is a conductor formed in a coil shape, for example, it can be a wire wound into an α-winding coil shape. As the wire, for example, a copper wire or a silver wire can be used. In addition, the coil conductor 11 can also be formed by applying a conductor paste in a coil shape on a substrate. In addition, the coil conductor 11 can also be formed by forming a metal film into a coil shape pattern on a substrate by etching or the like. In the coil component 1 of this embodiment, the coil conductor 11 can be as shown in FIG. Figure 3 Although shown as being arranged in the magnetic core 12, the coil conductor 11 may be wound around the magnetic core 12. The coil component 1 of this embodiment has a higher magnetic permeability and a higher electrical resistance.

[0084] exist Figure 3 In the coil component 1 shown, the coil conductor 11 is embedded in a magnetic core (unit body) 12 containing soft magnetic powder and a binder. The winding ends 11A and 11B of the coil conductor 11 are electrically connected to terminal electrodes 13 respectively formed at the two ends of the magnetic core 12. The terminal electrode 13 can be formed, for example, by applying a conductor paste such as Ag paste or Cu paste to the core. Alternatively, the terminal electrode 13 can also be formed by Ni sputtering, Ti sputtering, NiCr sputtering, etc. Alternatively, as the terminal electrode 13, for example, a cap-shaped metal conductor can be used. In this case, the cap-shaped metal conductor (terminal electrode) 13 is respectively embedded at the two ends of the unit body 12, and a conductive adhesive can be used to connect and fix the terminal electrode 13 to the unit body 12 and the winding ends 11A and 11B. The terminal electrode 13 can be a single layer, but can also be stacked in multiple layers.

[0085] The following describes an example of a method for manufacturing the coil component 1 of the present embodiment. First, a soft magnetic powder and a binder are mixed to obtain a mixture. The mixture is molded into a sheet to obtain a magnetic sheet. After the coil conductor 11 is embedded in the magnetic sheet, it is cut into a specified size and heated to a specified temperature to solidify the binder, thereby obtaining a magnetic core 12 with the coil conductor 11 disposed therein. By forming terminal electrodes 13 on the magnetic core 12, the coil component 1 can be obtained. As another method, the magnetic core 12 with the coil conductor 11 disposed therein can also be produced by the following method. First, a coil conductor pattern is formed on a magnetic sheet obtained by molding a mixture of coil soft magnetic powder and a binder. A specified number of magnetic sheets with the coil conductor pattern formed thereon are stacked to obtain a laminate. After the laminate is cut into a specified size, it is heated to a specified temperature to solidify the binder, thereby obtaining a magnetic core 12 with the coil conductor 11 disposed therein. By forming terminal electrodes 13 on the magnetic core 12, the coil component 1 can be obtained.

[0086] [Third embodiment]

[0087] Next, a magnetic material and a coil component according to a third embodiment of the present invention will be described below.

[0088] The manufacturing method of the magnetic material of the present embodiment includes: molding the soft magnetic powder of the embodiment of the present invention to obtain a molded body and heat-treating the molded body to obtain a magnetic material. First, a binder such as PVA (polyvinyl alcohol) is added to the soft magnetic powder and mixed to obtain a magnetic paste. The magnetic paste is molded using a scraper method or the like to obtain a molded body. The magnetic material can be obtained by heat-treating (calcining) the molded body at a prescribed temperature in an atmospheric atmosphere. The temperature of the heat treatment is preferably about 200°C to 850°C. The cores in the magnetic material of the present embodiment are preferably bonded to each other by an oxide film covering the surface of each core. The magnetic material obtained in this way has higher magnetic permeability and higher electrical resistance.

[0089] Figure 4a and Figure 4b An example of a coil component made of a magnetic material according to this embodiment is shown. Figure 4a is a perspective view of the coil component 2, Figure 4b It is an exploded perspective view of the unit cell 22 constituting the coil component 2 . Figure 4a The coil component 2 shown includes a unit body 22 and a coil conductor arranged inside the unit body 22. The unit body 22 is made of a magnetic material made of a soft magnetic powder according to an embodiment of the present invention. Figure 4b As shown, the coil conductor can be composed of coil conductor patterns 21A to 21C, and the unit cell 22 can be composed of magnetic layers 22A to 22D. The coil component 2 further includes a terminal electrode 23. The coil component 2 of this embodiment has higher magnetic permeability and higher resistance.

[0090] The following describes an example of a method for manufacturing the coil component 2 of the present embodiment. First, a binder such as PVA is added to a soft magnetic powder and mixed to obtain a magnetic paste for forming the magnetic layers 22A to 22D. In addition, a conductor paste such as Ag paste is prepared separately to form the coil conductor patterns 21A to 21C. By alternately printing the magnetic paste and the conductor paste in layers, a molded body is obtained. The molded body is subjected to a debinding treatment at a predetermined temperature in the atmosphere, and then subjected to a heat treatment at a predetermined temperature, thereby obtaining a unit body 22. Terminal electrodes 23 are formed at both ends of the obtained unit body 22. The terminal electrode 23 can be formed, for example, by applying a conductor paste such as Ag paste for the terminal electrode 13 to both ends of the unit body 22, sintering the paste, and then applying plating.

[0091] Example

[0092] (Example 1)

[0093] The soft magnetic powder of Example 1 was prepared according to the following procedure. In Example 1, FeSi alloy powder (Fe:Si = 93.5:6.5 (weight ratio)) with an average particle size (volume-based median diameter) of 5 μm, produced by a water atomization method, was used as the core. Iron chloride tetrahydrate was used as the iron salt, tetraethyl orthosilicate was used as the metal alkoxide, polyvinyl pyrrolidone K30 was used as the water-soluble polymer, ethanol was used as the solvent, and ammonia was used as the alkaline catalyst. 10 g of a 9 wt% ammonia solution and 50 g of the FeSi alloy powder were added to 14.2 g of ethanol. Polyvinyl pyrrolidone K30 and iron chloride tetrahydrate were added to the ethanol containing the ammonia solution and FeSi alloy powder, respectively, to a concentration of 0.5 wt% relative to the weight of the FeSi alloy powder and 3.5 wt% relative to the weight of the FeSi alloy powder, and the mixture was stirred to obtain a mixed solution. Tetraethyl orthosilicate was weighed to a concentration of 3 wt% relative to the weight of the FeSi alloy powder, as SiO2, and added dropwise to the mixed solution. The dropwise added mixed solution was stirred and mixed for 60 minutes to obtain a slurry. The slurry was filtered, washed with acetone, and dried at 60°C to obtain the soft magnetic powder of Example 1. Almost no iron was detected in the filtrate after filtration and the washing liquid after washing.

[0094] (Example 2)

[0095] The soft magnetic powder of Example 2 was prepared by the same procedure as in Example 1 except that polyvinyl pyrrolidone K30 was added so as to be 0.25 wt % based on the weight of the FeSi alloy powder (Fe:Si=93.5:6.5 (weight ratio)).

[0096] (Example 3)

[0097] The soft magnetic powder of Example 3 was prepared by the same procedure as in Example 1 except that ferric chloride tetrahydrate was added so as to be 1.7 wt % based on the weight of the FeSi alloy powder.

[0098] (Examples 4 to 6)

[0099] Soft magnetic powders of Examples 4 to 6 were prepared by the same procedures as in Example 1 except that tetraisopropoxytitanium, n-butoxyzirconium, and isopropoxyaluminum were used as metal alkoxides instead of tetraethyl orthosilicate.

[0100] (Examples 7 to 12)

[0101] Instead of polyvinyl pyrrolidone K30, polyvinyl alcohol, hydroxypropyl cellulose, poly (2-methyl-2- oxazoline), sodium polyoxyalkylene styryl phenyl ether phosphate, cetyltrimethylammonium bromide and lauric acid diethanolamide, the soft magnetic powders of Examples 7 to 12 were prepared by the same steps as in Example 1.

[0102] (Example 13)

[0103] The soft magnetic powder of Example 13 was prepared by the same procedure as in Example 1 except that iron nitrate nonahydrate was used as the iron salt instead of iron chloride tetrahydrate.

[0104] (Comparative Example 1)

[0105] A soft magnetic powder of Comparative Example 1 was prepared by the same procedure as in Example 1 except that no water-soluble polymer was added.

[0106] (Comparative Example 2)

[0107] A soft magnetic powder of Comparative Example 2 was prepared by the same procedure as in Example 1 except that no iron salt was added.

[0108] (Comparative Example 3)

[0109] A soft magnetic powder of Comparative Example 3 was prepared by the same procedure as in Example 1 except that no metal alkoxide was added.

[0110] (Analysis of Iron Content)

[0111] For each of the soft magnetic powders of Examples 1 to 13 and Comparative Examples 1 to 3, the average particle size of the iron component present in the insulating film and the presence or absence of the iron component on the surface of the insulating film were measured according to the steps described below. First, the soft magnetic powder to be measured was embedded in a resin and ground, and a sample for STEM-EDX observation was made by FIB (focused ion beam) processing. Using this sample, elemental mapping of the cross section of the insulating film was performed using a STEM-EDX device. The STEM used was JEM-2000FS manufactured by JEOL Ltd., and the EDX device used was Noran System 7. As a result of the elemental mapping, for the soft magnetic powders of Examples 1 to 13, it was confirmed that the iron component was embedded in the insulating film. As a representative example, the elemental mapping results of Example 1 are shown in FIG. Figure 1a to Figure 1d .like Figure 1b and Figure 1d As shown in FIG, since iron and oxygen were detected at almost the same position, it can be inferred that the iron component is iron oxide. On the other hand, for the soft magnetic powders of Comparative Examples 1 to 3, no iron component was observed embedded in the insulating film. Figure 1a In the case of the ionization of carbon, the C (carbon) element generated by organic matter was detected in the insulating film. Figure 1d A film containing iron oxide was detected near the boundary between the insulating film and the core. This is presumably an oxide film formed on the surface of the FeSi alloy powder (Fe:Si = 93.5:6.5 (weight ratio)) used to make the core during water atomization.

[0112] For the soft magnetic powders of Examples 1 to 13, in which the presence of the iron component embedded in the insulating film was confirmed, images of the cross sections of the insulating films were taken using TEM. As a representative example, the TEM image of the cross section of the insulating film of Example 1 is shown in FIG. Figure 2a and Figure 2b .exist Figure 2a and Figure 2bIn the TEM image, lattice stripes corresponding to the particles of the iron component were observed. Based on the obtained TEM image, the average particle size of the particles of the iron component embedded in the insulating film was determined according to the following steps. For each of the 10 particles of the iron component, the major axis (the longest diameter) and the minor axis (the shortest diameter) were measured, and the average of the major axis and the minor axis was taken as the particle size of the particle. The average of the particle sizes of the 5 particles was taken as the average particle size. The results are shown in Table 1. In addition, the content of the iron component embedded in the insulating film (excluding the iron component on the surface of the insulating film) is shown in Table 1. The content of the iron component (weight %) was calculated from the ratio of the weight of Fe in the insulating film to the weight of the core. The numerical values recorded in Table 1 are values that are inferred from the feed amount of the iron salt as the raw material of the iron component, that is, the iron in the iron salt is completely absorbed into the insulating film. It should be noted that for the soft magnetic powders of Comparative Examples 1 to 3 in which the iron component embedded in the insulating film was not observed in the elemental mapping of the cross section of the insulating film measured by the STEM-EDX device, the content of the iron component in Table 1 was set to 0 weight %.

[0113] The soft magnetic powders of Examples 1 to 13 and Comparative Examples 1 to 3 were used to confirm the presence of iron on the surface of the insulating film by XPS analysis. XPS analysis was performed using a VersaProbe manufactured by ULVAC-PHI, Inc. The presence of iron on the surface of the insulating film was confirmed when an Fe peak was detected by XPS analysis, and is indicated as "Present" in Table 1. The absence of an Fe peak indicated the absence of iron on the surface of the insulating film, and is indicated as "Absent" in Table 1.

[0114] (Making of annular rings)

[0115] Using the soft magnetic powders of Examples 1 to 13 and Comparative Examples 1 to 3, annular rings were produced according to the following procedures. The soft magnetic powders were mixed with a silicone resin at 3% by weight relative to the weight of the soft magnetic powder to produce granules. The granules were heated and molded in a mold, followed by curing to produce annular rings.

[0116] (Measurement of specific resistance)

[0117] The specific resistance of the rings produced using the soft magnetic powders of Examples 1 to 13 and Comparative Examples 1 to 3 was measured by applying a voltage of 10 V for 5 seconds. The specific resistance was measured using a digital electrometer (Advantest R8340A ULTRA HIGH RESISTANCE METER) manufactured by Advantest. The results are shown in Table 1.

[0118] (Determination of relative magnetic permeability)

[0119] The relative magnetic permeability at 1 MHz was measured for each of the annular rings produced using the soft magnetic powders of Examples 1 to 13 and Comparative Examples 1 to 3. The relative magnetic permeability was measured using an impedance analyzer (Agilent E4991A RF) manufactured by Agilent Technologies. The results are shown in Table 1.

[0120] [Table 1]

[0121]

[0122] As shown in Table 1, nanoparticles of iron components embedded in the insulating film were detected in the soft magnetic powders of Examples 1 to 13. In addition, in the soft magnetic powders of Examples 1 to 13, no components were detected on the surface of the insulating film. In contrast, in the soft magnetic powder of Comparative Example 1, to which no water-soluble polymer and surfactant were added, no iron components embedded in the insulating film were detected. In addition, in the soft magnetic powder of Comparative Example 1, iron components were detected on the surface of the insulating film. In the soft magnetic powder of Comparative Example 2, to which no iron salt was added, no iron components embedded in the insulating film were detected. In the soft magnetic powder of Comparative Example 3, to which no metal alkoxide was added, no iron components embedded in the insulating film were detected. In addition, in the soft magnetic powder of Comparative Example 1, iron components were detected on the surface of the insulating film.

[0123] In addition, as shown in Table 1, the soft magnetic powders of Examples 1 to 13 showed a value of 9.80×10 11 The soft magnetic powder of Comparative Example 1, to which no water-soluble polymer or surfactant was added, exhibited a lower specific resistivity and a lower relative magnetic permeability than the soft magnetic powders of Examples 1 to 13. The soft magnetic powder of Comparative Example 2, to which no iron salt was added, exhibited a lower relative magnetic permeability than the soft magnetic powders of Examples 1 to 13. The soft magnetic powder of Comparative Example 3, to which no metal alkoxide was added, exhibited a lower specific resistivity and a lower relative magnetic permeability than the soft magnetic powders of Examples 1 to 13.

[0124] The present invention includes the following aspects, but is not limited to these aspects.

[0125] (Scheme 1)

[0126] A soft magnetic powder having:

[0127] A core made of soft magnetic metal material, and

[0128] The insulating film covering the core surface,

[0129] The insulating film contains an insulating metal oxide and an iron component, and the iron component is embedded in the insulating film.

[0130] (Scheme 2)

[0131] The soft magnetic powder according to claim 1, wherein the iron component is iron oxide.

[0132] (Scheme 3)

[0133] The soft magnetic powder according to claim 1 or 2, wherein the insulating film contains particles containing an iron component.

[0134] (Scheme 4)

[0135] The soft magnetic powder according to any one of aspects 1 to 3, wherein the average particle size of particles of the iron component is 5 nm to 20 nm.

[0136] (Scheme 5)

[0137] The soft magnetic powder according to any one of aspects 1 to 4, wherein the insulating metal oxide is a hydrolyzate of a metal alkoxide.

[0138] (Scheme 6)

[0139] The soft magnetic powder according to any one of aspects 1 to 5, wherein the insulating film further contains an organic substance.

[0140] (Scheme 7)

[0141] The soft magnetic powder according to claim 6, wherein the organic substance is at least one selected from the group consisting of a water-soluble polymer and a surfactant.

[0142] (Scheme 8)

[0143] The soft magnetic powder according to any one of aspects 1 to 7, wherein the insulating film contains at least one element selected from the group consisting of C, N, and P.

[0144] (Scheme 9)

[0145] The soft magnetic powder according to any one of aspects 1 to 8, wherein the insulating metal oxide is at least one selected from the group consisting of titanium oxide, silicon oxide, aluminum oxide, and zirconium oxide.

[0146] (Scheme 10)

[0147] The soft magnetic powder according to any one of aspects 1 to 11, wherein the core is composed of an Fe-based, Ni-based, or Co-based soft magnetic metal material.

[0148] (Scheme 11)

[0149] The soft magnetic powder according to any one of aspects 1 to 10, wherein no iron component is present on the surface of the insulating film.

[0150] (Scheme 12)

[0151] The soft magnetic powder according to any one of aspects 1 to 11, further comprising a film containing an iron oxide.

[0152] The film containing the oxide of iron is formed near a boundary between the insulating film and the core.

[0153] (Scheme 13)

[0154] A method for producing soft magnetic powder, comprising:

[0155] A core composed of a soft magnetic metal material, an iron salt, a metal alkoxide, and at least one selected from a water-soluble polymer and a surfactant are mixed in a solvent to obtain a slurry; and

[0156] The slurry is dried to obtain a soft magnetic powder having a core and an insulating film covering the surface of the core.

[0157] (Scheme 14)

[0158] The method for producing a soft magnetic powder according to claim 13, wherein obtaining the slurry includes hydrolyzing a metal alkoxide.

[0159] (Scheme 15)

[0160] The method for producing a soft magnetic powder according to claim 13 or 14, wherein the iron salt is soluble in alcohol.

[0161] (Scheme 16)

[0162] The method for producing a soft magnetic powder according to claim 15, wherein the iron salt is at least one selected from ferric chloride, ferric nitrate, and hydrates thereof.

[0163] (Scheme 17)

[0164] The method for producing a soft magnetic powder according to any one of aspects 13 to 16, wherein the water-soluble polymer and the surfactant have a ligand capable of forming a coordination compound with Fe ions.

[0165] (Scheme 18)

[0166] The method for producing a soft magnetic powder according to claim 17, wherein the water-soluble polymer is selected from polyvinyl pyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, poly (2-methyl-2- At least one of oxazoline, polyethyleneimine, polyacrylic acid and carboxymethyl cellulose.

[0167] (Scheme 19)

[0168] The method for producing a soft magnetic powder according to claim 17 or 18, wherein the surfactant is at least one selected from the group consisting of sodium polyoxyalkylene styrylphenyl ether phosphate, cetyltrimethylammonium bromide, and lauric acid diethanolamide.

[0169] (Scheme 20)

[0170] The method for producing a soft magnetic powder according to any one of aspects 13 to 19, wherein the metal alkoxide is at least one alkoxide selected from the group consisting of Si, Al, Ti, and Zr.

[0171] (Scheme 21)

[0172] The method for producing a soft magnetic powder according to any one of aspects 13 to 20, wherein the solvent contains alcohol.

[0173] (Scheme 22)

[0174] A coil component, comprising:

[0175] A magnetic core comprising the soft magnetic powder according to any one of claims 1 to 12 and a resin, and

[0176] A coil conductor is provided inside the unit body.

[0177] (Scheme 23)

[0178] A method for manufacturing a magnetic material, comprising:

[0179] The soft magnetic powder of any one of claims 1 to 12 is molded to obtain a molded body, and

[0180] The molded body is heat-treated to obtain a magnetic material.

[0181] While one embodiment of the present invention has been described above, this is merely a typical example within the applicable scope of the present invention. Therefore, it will be readily understood by those skilled in the art that the present invention is not limited thereto and that various modifications are possible.

[0182] Industrial applicability

[0183] The soft magnetic powder and its production method, the coil component using the soft magnetic powder, and the magnetic material using the soft magnetic powder of the present invention can achieve higher magnetic permeability and higher electrical resistance, and thus can be well used in a wide range of applications such as high-frequency applications.

[0184] Explanation of symbols

[0185] 1.2 Coil components

[0186] 11 Coil conductor

[0187] 11A, 11B roll end

[0188] 12, 22 unit body (magnetic core)

[0189] 13, 23 terminal electrodes

[0190] 21A, 21B, 21C Coil conductor pattern

[0191] 22A, 22B, 22C, 22D magnetic layers

Claims

1. A soft magnetic powder having: A core made of soft magnetic metal material, and an insulating film covering the surface of the core, The insulating film contains an insulating metal oxide and an iron component, and the iron component includes an iron component embedded in the insulating film. Furthermore, the insulating film contains the iron component particles. The insulating film contains the iron component as a magnetic substance, and the iron component particles are dispersed in the insulating film.

2. The soft magnetic powder according to claim 1, wherein The iron component is iron oxide.

3. The soft magnetic powder according to claim 1, wherein The average particle size of the iron component particles is 5 nm to 20 nm.

4. The soft magnetic powder according to any one of claims 1 to 3, wherein The insulating metal oxide is a hydrolyzate of a metal alkoxide.

5. The soft magnetic powder according to any one of claims 1 to 3, wherein The insulating film further contains an organic substance. The soft magnetic powder according to claim 5 , wherein The organic matter is at least one selected from water-soluble polymers and surfactants.

7. The soft magnetic powder according to any one of claims 1 to 3, wherein The insulating film contains at least one element selected from C, N, and P.

8. The soft magnetic powder according to any one of claims 1 to 3, wherein The insulating metal oxide is at least one selected from titanium oxide, silicon oxide, aluminum oxide, and zirconium oxide.

9. The soft magnetic powder according to any one of claims 1 to 3, wherein The core is made of a Fe-based, Ni-based, or Co-based soft magnetic metal material.

10. The soft magnetic powder according to any one of claims 1 to 3, wherein The iron component does not exist on the surface of the insulating film.

11. The soft magnetic powder according to any one of claims 1 to 3, wherein further comprising a film containing an iron oxide, The film containing the oxide of iron is formed near a boundary between the insulating film and the core.

12. A method for producing soft magnetic powder, comprising: A core composed of a soft magnetic metal material, an iron salt, a metal alkoxide, and at least one selected from a water-soluble polymer and a surfactant are mixed in a solvent to obtain a slurry; and drying the slurry to obtain a soft magnetic powder having the core and an insulating film covering the surface of the core; Wherein, obtaining the slurry includes hydrolyzing the metal alkoxide.

13. The method for producing a soft magnetic powder according to claim 12, wherein: The iron salt is soluble in alcohol.

14. The method for producing a soft magnetic powder according to claim 13, wherein: The iron salt is at least one selected from ferric chloride, ferric nitrate and hydrates thereof.

15. The method for producing a soft magnetic powder according to any one of claims 12 to 14, wherein: The water-soluble polymer and the surfactant have ligands capable of forming a coordination compound with Fe ions.

16. The method for producing a soft magnetic powder according to claim 15, wherein: The water-soluble polymer is selected from polyvinyl pyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, poly (2-methyl-2- at least one of oxazoline, polyethyleneimine, polyacrylic acid and carboxymethyl cellulose.

17. The method for producing a soft magnetic powder according to claim 15, wherein: The surfactant is at least one selected from polyoxyalkylene styryl phenyl ether sodium phosphate, cetyltrimethylammonium bromide and lauric acid diethanolamide.

18. The method for producing a soft magnetic powder according to any one of claims 12 to 14, wherein: The metal alkoxide is at least one alkoxide selected from Si, Al, Ti and Zr.

19. The method for producing a soft magnetic powder according to any one of claims 12 to 14, wherein: The solvent comprises an alcohol.

20. A coil component comprising: a magnetic core and a coil conductor, The magnetic core comprises the soft magnetic powder according to any one of claims 1 to 11 and a binder.

21. A method for manufacturing a magnetic material, comprising: The soft magnetic powder according to any one of claims 1 to 11 is molded to obtain a molded body, The molded body is heat-treated to obtain a magnetic material.

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