Soft magnetic metal powder, inductor, and method for producing soft magnetic metal powder

Abstract

The present invention provides a soft magnetic metal powder and an inductor which have better withstand voltage characteristics and in which structural defects in an insulating film caused by stress that occurs in the course of production have been further reduced, and a method for producing said soft magnetic metal powder. A soft magnetic metal powder 20 of the present disclosure comprises soft magnetic metal particles 21 and insulating films 22 that cover the soft magnetic metal particles 21, wherein: the insulating films 22 contain a silanol group; and A1 / A0 is 0.052-0.085 where A0 is the infrared absorbance derived from an Si-O bond that is contained in the insulating films 22, and A1 is the infrared absorbance derived from an OH group that is contained in the silanol group.

Description

Soft magnetic metal powder, inductor, and method for manufacturing soft magnetic metal powder

[0001] The present disclosure relates to a soft magnetic metal powder, an inductor, and a method for manufacturing the soft magnetic metal powder.

[0002] Electronic components such as inductors are widely used in power supply circuits of various electronic devices. These electronic components include an element body containing a magnetic material and a coil disposed within the element body. In recent years, soft magnetic metal materials have been adopted as the magnetic material used in the element body (see, for example, Patent Documents 1 and 2). Soft magnetic metal materials have higher saturation magnetization (saturation magnetic flux density) and superior DC bias characteristics compared to ferrite, a conventional magnetic material, and are therefore suitable for miniaturizing electronic components.

[0003] When soft magnetic metal materials are used as magnetic materials in electronic components, they tend to be easily ionized and are therefore highly susceptible to corrosion, etc. This causes a deterioration in the magnetic properties of the electronic components, etc. To reduce the corrosion of such soft magnetic metal materials, a technique of coating the soft magnetic metal material with an insulating coating is known (e.g., Patent Documents 3 and 4).

[0004] Japanese Patent No. 3342767 Japanese Patent Application Laid-Open No. 2017-034228 Japanese Patent Application Laid-Open No. 2006-097123 Japanese Patent Application Laid-Open No. 2017-188588

[0005] When electronic components are installed in power supply circuits, etc., they require good electrostatic discharge characteristics. Therefore, the insulating coating of soft magnetic metal particles needs to have excellent voltage resistance. Furthermore, when manufacturing inductors using soft magnetic metal particles coated with an insulating coating, stress generated during the manufacturing process can cause structural defects such as cracks in the insulating coating.

[0006] In view of these points, the present disclosure provides a soft magnetic metal powder, an inductor, and a method for manufacturing soft magnetic metal powder that have better voltage resistance characteristics and that further reduce structural defects in the insulating coating caused by stresses that occur during the manufacturing process.

[0007] The soft magnetic metal powder according to the present disclosure is a soft magnetic metal powder comprising soft magnetic metal particles and an insulating coating that covers the soft magnetic metal particles, wherein the insulating coating contains a silanol group, and the infrared absorbance derived from the Si—O bond contained in the insulating coating is A ０ The infrared absorbance derived from the OH group contained in the silanol group is represented by A １ When this is done, A １ / A ０ is 0.052 or more and 0.085 or less.

[0008] The inductor of the present disclosure includes an element body including the above-described soft magnetic metal powder, and a coil provided within the element body.

[0009] The method for producing soft magnetic metal powder according to the present disclosure includes an insulating film forming step of forming an insulating film of an organic-inorganic composite on the surface of soft magnetic metal particles, and a reduction treatment step of performing a reduction treatment to reduce OH groups in the insulating film, and the infrared absorbance derived from Si—O bonds is reduced to A ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０ The soft magnetic metal powder is produced with an insulating coating that coats the soft magnetic metal particles, and the insulating coating has a value of 0.052 or more and 0.085 or less.

[0010] According to the present disclosure, the infrared absorbance derived from the Si—O bond is A ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０ is 0.052 or more and 0.085 or less, it is possible to achieve both good voltage resistance characteristics and a reduction in structural defects in the insulating coating.

[0011] Fig. 1 is a perspective view of an inductor according to the present disclosure. Fig. 2 is an exploded perspective view of one embodiment of the inductor according to the present disclosure. Fig. 3 is a cross-sectional view taken along the arrow III-III in the region defined by the dashed line in Fig. 2. Fig. 4 is a perspective view of another embodiment of the inductor according to the present disclosure. Fig. 5 is a manufacturing flow chart illustrating the manufacturing process of the soft magnetic metal powder according to the present disclosure.

[0012] The soft magnetic metal powder, inductor, and method for manufacturing the soft magnetic metal powder according to the present disclosure will be described in detail below. While the description will refer to the drawings as necessary, the contents shown in the drawings are merely schematic and illustrative for the purpose of understanding the present disclosure, and the appearance and dimensional ratios may differ from the actual products.

[0013] FIG. 1 is a perspective view of an inductor of the present disclosure, FIG. 2 is an exploded perspective view of one embodiment of the inductor of the present disclosure, FIG. 3 is a cross-sectional view taken along the arrow III-III in the area bounded by the dashed line in FIG. 2, FIG. 4 is a perspective view of another embodiment of the inductor of the present disclosure, and FIG. 5 is a manufacturing flow chart illustrating the manufacturing process of the soft magnetic metal powder of the present disclosure.

[0014] <Description of Soft Magnetic Metal Powder According to the Present Disclosure> First, the soft magnetic metal powder according to the present disclosure will be described. The soft magnetic metal powder 20 includes soft magnetic metal particles 21 and insulating coatings 22 that coat the soft magnetic metal particles 21 (see FIG. 3 ).

[0015] An example of the soft magnetic metal particles 21 may be an Fe (iron) or Fe—Si (silicon)-based amorphous alloy. Such soft magnetic metal materials can provide suitable magnetic permeability when used in inductors. The soft magnetic metal particles 21 may be an Fe—Si—Cr (chromium)-based alloy, an Fe—Si—Al (aluminum)-based alloy, an Fe—Si—B (boron)-P (phosphorus)-Cu (copper)-C (carbon)-based alloy, an Fe—Si—B—Nb (niobium)-Cu-based alloy, or the like. The soft magnetic metal particles 21 may also contain impurities such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur), or Co (cobalt) that are not intended during manufacturing. The soft magnetic metal particles 21 may also be contained in a magnetic paste, as will be described in detail in the description of the manufacturing method. Therefore, the soft magnetic metal particles 21 may contain an element (e.g., Cr, Al, Li (lithium), Zn (zinc)) that is more easily oxidized than the Fe added when the magnetic paste is prepared. By adding Si to the soft magnetic metal particles 21, oxidation of the Fe element contained in the soft magnetic metal particles 21 can be suppressed, thereby further increasing the magnetic permeability of the inductor manufactured using the soft magnetic metal particles 21. The resin component contained in the magnetic paste may be eliminated by heat treatment, or may remain.

[0016] The insulating coating 22 has insulating properties. In this specification, "insulating" means that the volume resistivity is 1 MΩcm or more. The insulating coating 22 contains Si—O bonds and silanol groups.

[0017] The OH groups contained in the Si-O bonds and silanol groups in the insulating coating 22 can be detected by Fourier transform infrared spectroscopy (FT-IR). The amount of OH groups contained in the Si-O bonds and silanol groups can be measured by using an infrared spectrophotometer (Bruker Japan Co., Ltd., Model: VERTEX 70V) to measure the diffuse reflected light from the sample surface to obtain an infrared spectrum (diffuse reflectance method). Specifically, the OH groups contained in the Si-O bonds and silanol groups are detected by the vibration of the Si-O bonds at 1230 cm -1 Infrared absorbance A ０ , and 1600-1700 cm resulting from the vibration of the OH group contained in the silanol group. -1 Infrared absorbance A １ It can be determined by measuring

[0018] The soft magnetic metal powder 20 of the present disclosure has an A １ / A ０ may be 0.052 or more and 0.085 or less. １ / A ０ By specifying the range of the optimum content of OH groups contained in the silanol groups in the soft magnetic metal powder 20, the range of the optimum content of OH groups contained in the silanol groups in the soft magnetic metal powder 20 is defined. Here, the OH groups in the soft magnetic metal powder 20 act to increase the binding strength with the resin, but are also polar as functional groups and have electron donating properties. Therefore, reducing the OH groups reduces the formation of electron conduction paths and improves the withstand voltage. On the other hand, excessively reducing the OH groups may reduce the binding strength with the resin, and structural defects such as cracks may occur in the insulating coating 22 due to stress generated during the manufacturing process. Therefore, as in the present disclosure, １ / A ０ By setting the value of the OH group content to 0.052 or more and 0.085 or less, the content of OH groups is optimized, and it is possible to achieve both good voltage resistance characteristics and a reduction in structural defects in the insulating coating.

[0019] In a preferred embodiment of the insulating coating 22, the insulating coating 22 may contain an organic-inorganic composite. The term "organic-inorganic composite" as used herein refers to a combination of a silica gel film formed on the surface of the soft magnetic metal particles 21 during the hydrolysis and polymerization reaction of a metal alkoxide and a polymer having a carbonyl group, resulting in a molecular level compatibility. In other words, the organic-inorganic composite is formed by hydrogen bonding between the OH groups bonded to the silica present on the gel film and the carbonyl groups of the polymer. By including the organic-inorganic composite in the insulating coating 22, a hydrolysis and polymerization reaction can be initiated, resulting in an insulating coating 22 that achieves high voltage resistance and reduced structural defects.

[0020] Metal alkoxides have the chemical formula M(OR) ｘ (M: metal element, OR: alkoxy group). The metal species M constituting the metal alkoxide may be Si. When the metal species is Si, an insulating metal oxide having higher strength and higher resistivity can be formed. Furthermore, metal alkoxides in which the metal species M is Si (Si(OR) ４ ) is chemically more stable and therefore easier to handle during manufacturing.

[0021] The alkoxy group OR constituting the metal alkoxide is not particularly limited, and may be, for example, an alkoxy group having 10 or less carbon atoms, particularly 5 or less carbon atoms, and more particularly 3 or less carbon atoms. The smaller the carbon number, the more easily the hydrolysis reaction can proceed. 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 tetraethyl orthosilicate or tetramethoxysilane.

[0022] Furthermore, the soft magnetic metal powder 20 of the present disclosure undergoes a reduction treatment to reduce OH groups in the insulating coating 22, as will be described in detail later in the manufacturing method. The reduction treatment is performed, for example, using dimethylamine borane and / or sodium borohydride. Therefore, the insulating coating 22 of the present disclosure may contain N (nitrogen) elements resulting from the above-mentioned dimethylamine borane. When the insulating coating 22 contains nitrogen elements, the OH groups are appropriately reduced, improving the withstand voltage.

[0023] The average particle size of the soft magnetic metal powder 20 of the present disclosure may be 1 μm or more and 30 μm or less. The average particle size of the soft magnetic metal powder 20 can be measured using the procedure described below. An inductor sample is cut to obtain a cross-section of the sample. Specifically, the sample cross-section is obtained by cutting the sample through the winding axis of the coil of the element body, perpendicular to the mounting surface and end surface of the element body. Multiple (e.g., five) regions (e.g., 130 μm x 100 μm) of the obtained cross-section are photographed using an SEM. The obtained SEM images are analyzed using image analysis software (e.g., image analysis software "Win R00F" (manufactured by Mitani Shoji Co., Ltd.)) to determine the circle-equivalent diameter of the soft magnetic metal powder. The average value of the obtained circle-equivalent diameters is defined as the average particle size of the soft magnetic metal powder. Note that, in this specification, "average particle size" may refer to the average particle size D50 (particle size corresponding to a cumulative percentage of 50% on a volume basis).

[0024] <Method for manufacturing soft magnetic metal powder according to the present disclosure> Next, a method for manufacturing soft magnetic metal powder according to the present disclosure will be described with reference to Fig. 5. The method for manufacturing soft magnetic metal powder according to the present disclosure includes an insulating coating formation step and a reduction treatment step. The following description will be given along the manufacturing flow shown in Fig. 5.

[0025] Insulating Coating Forming Step The insulating coating forming step is a step of forming an insulating coating 22 of organic-inorganic composite on the surface of the soft magnetic metal particles 21. First, a slurry for forming the insulating coating 22 is prepared.

[0026] To prepare the slurry, a solution is prepared by dissolving a metal alkoxide containing Si (e.g., tetraethyl orthosilicate) in an alcohol solution having OH groups (e.g., isopropanol). That is, a solution containing a compound having Si atoms and a compound having OH groups is prepared. Granular material (e.g., iron powder) that constitutes the soft magnetic metal particles 21 is added to the solution. The solution reacts in an alkaline environment to produce silanol groups. Note that the alcohol solution having OH groups described above is not limited to isopropanol, and ethanol, for example, may be used. Furthermore, the metal alkoxide containing Si is not limited to tetraethyl orthosilicate, and tetramethoxysilane, for example, may be used.

[0027] Furthermore, to prepare the slurry, a solution containing a resin having a water-soluble polymer (e.g., pyrrolidone or polyvinylpyrrolidone) is mixed with the solution to which the above-mentioned particulate matter has been added, and the mixture is stirred for a predetermined period of time. This prepares the slurry for forming the insulating coating 22. Obtaining the slurry in this manner may involve hydrolysis of the metal alkoxide. The solutions may be mixed at room temperature or under heating. The resin is not limited to pyrrolidone or polyvinylpyrrolidone; for example, polyvinyl alcohol, polyacrylamide, etc. may also be used.

[0028] After preparing the slurry, the slurry is subjected to solid-liquid separation by suction filtration or the like, and then dried to obtain a powdery material having an insulating coating of the organic-inorganic composite. Before the solid-liquid separation, the product may be washed (for example, with acetone). Instead of the above-mentioned suction filtration, pressure filtration such as with a filter press or centrifugal filtration may be performed.

[0029] Reduction Treatment Step The reduction treatment step is a step of performing a reduction treatment to reduce OH groups in the insulating coating. Specifically, a powder having an insulating coating of an organic-inorganic composite is dispersed in an alcohol solution (e.g., isopropanol). Then, the dispersion solution is mixed with a solution in which a reducing agent (e.g., a hydride reducing agent, specifically, dimethylamine borane) is dissolved, and the mixture is stirred for a predetermined period of time. Obtaining a solution in this manner may involve the reduction of OH groups by the reducing agent. The solutions may be mixed at room temperature or may be heated. The alcohol solution described above is not limited to isopropanol, and for example, ethanol may be used. The reducing agent described above is not limited to dimethylamine borane, and for example, sodium borohydride may be used.

[0030] After the reduction treatment, the mixture is subjected to solid-liquid separation by suction filtration or the like, and then dried to obtain the soft magnetic metal particles of the present disclosure.

[0031] As described above, according to the method for producing soft magnetic metal powder of the present disclosure, the infrared absorbance derived from the Si—O bond measured by Fourier transform infrared spectroscopy (FT-IR) is A ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０ However, it is possible to produce soft magnetic metal powder having an insulating coating that coats soft magnetic metal particles, in which the coefficient of elasticity is 0.052 or more and 0.085 or less.

[0032] Furthermore, to be more specific, focusing on the production of an inductor using this soft magnetic metal powder, by adding a water-soluble polymer during the hydrolysis polymerization reaction of a metal alkoxide containing Si, it is possible to form a flexible organic-inorganic composite that can adapt to deformation due to load during magnetic core molding. As a result, when the soft magnetic metal powder of the present disclosure is used to produce an inductor, it is possible to improve the volume resistivity (electrical resistance) while reducing structural defects.

[0033] Furthermore, the silica surface obtained by the hydrolysis polymerization reaction is generally composed of Si-O bonds and silanol residues. By partially reducing the carbonyl groups contained in the organic-inorganic composite with a reducing agent, the amount of OH groups derived from the silanol residues on the surface can be appropriately adjusted. By appropriately reducing the amount of OH groups, the formation of electron conduction paths can be suppressed, improving the withstand voltage.

[0034] On the other hand, if the OH groups and carbonyl groups are reduced excessively, the bonding strength with the resin decreases because there are fewer bonding points that interact with the functional groups of the resin, which can lead to cracks during core molding. Therefore, by using an appropriate amount of reducing agent, the OH content in the insulating coating can be adjusted to an optimal range, achieving both improved voltage resistance and reduced structural defects.

[0035] <Description of Inductor of the Present Disclosure> Next, the inductor of the present disclosure will be described with reference to Figures 1 to 4. The inductor of the present disclosure includes an element body 10 including the soft magnetic metal powder described above, and a coil provided within the element body 10.

[0036] The inductor of the present disclosure may be an inductor configured by laminating a plurality of base layers G1 to G8, each having a coil conductor CD and a magnetic layer ML, as shown in Fig. 2 (hereinafter referred to as inductor 1A of the first embodiment), or an inductor configured by winding a conductor wire as shown in Fig. 4 (hereinafter referred to as inductor 1B of the second embodiment). In the following explanation, the inductor of the first embodiment will be described first, followed by the inductor of the second embodiment.

[0037] Description of the Inductor of the First Embodiment The element body 10 has, for example, a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape having six sides. The element body 10 may have rounded corners and ridges. A corner is a portion where three sides of the element body 10 intersect, and a ridge is a portion where two sides of the element body 10 intersect.

[0038] 1, the length direction, width direction, and height direction of the inductor 1A and the element body 10 are shown as L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are perpendicular to each other. The mounting surface of the inductor 1A is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

[0039] 1 has a first main surface 11 and a second main surface 12 that face each other in a height direction T, a first end surface 13 and a second end surface 14 that are perpendicular to the height direction T and face each other in a length direction L, and a first side surface 15 and a second side surface 16 that face each other in a width direction W that is perpendicular to the length direction L and the height direction T. In the example shown in FIG. 1 , the first main surface 11 of the element body 10 corresponds to the mounting surface (bottom surface) of the element body 10. Note that the second main surface 12 may also be the mounting surface of the element body 10.

[0040] The element body 10 has a laminated structure in which a plurality of element body layers, each having a magnetic layer ML and a coil conductor CD formed thereon, are stacked in a stacking direction (for example, height direction T). In this embodiment, the element body 10 is constructed by stacking element body layers G1 to G8 as shown in FIG. 2. A coil is then constructed by stacking a plurality of coil conductors CD. By constructing a coil by stacking coil conductors CD, it is possible to make it smaller than the coil C of the second embodiment described below. Note that the boundaries between the layers in the laminated structure of the element body 10 disappear. Furthermore, each of the element body layers G1 to G8 may be constructed by stacking a plurality of identical patterns.

[0041] A coil formed by stacking multiple coil conductors CD is provided within the element body 10. In the example shown in FIG. 2, two coils (a first coil and a second coil) are provided within the element body 10 along the stacking direction. More specifically, the first coil is formed by the coil conductors CD of element body layers G4 and G5, and the second coil is formed by the coil conductors CD of element body layers G2 and G3. The inductor 1A of the first embodiment is not limited to this example, and may have, for example, three or more coils provided along the stacking direction. Furthermore, a coil array may be formed by arranging multiple coils side by side within the element body 10 in a direction intersecting the stacking direction (direction L in FIG. 1).

[0042] External electrodes E are provided on the mounting surface (first main surface 11) of the element body 10. In the example shown in Fig. 2, the external electrodes E include a first external electrode E1 and a second external electrode E2 connected to the respective ends of the first coil, and a third external electrode E3 and a fourth external electrode E4 connected to the respective ends of the second coil. Two external electrodes are provided for each coil. Therefore, if the number of coils is three, the number of external electrodes may be six.

[0043] The through-hole conductors TH may be used to connect the coil C and the external electrodes E. That is, the first through-hole conductors TH1 to TH4 may be provided corresponding to the first external electrode E1 to the fourth external electrode E4. The first through-hole conductors TH1 to TH4 may extend along the stacking direction.

[0044] The inductor of the present disclosure uses the above-described soft magnetic metal powder 20 in the manufacture of the element body 10. Therefore, according to the inductor of the present disclosure, the infrared absorbance derived from the Si—O bond measured by Fourier transform infrared spectroscopy (FT-IR) is A ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０ Since the soft magnetic metal powder contains a material having a modulus of 0.052 or more and 0.085 or less, the material has better voltage resistance characteristics and can further reduce structural defects caused by stresses that occur during the manufacturing process of the inductor.

[0045] An example of a method for identifying the insulating coating 22 of the soft magnetic metal particles 21 in the inductor of the present disclosure is as follows. (1) A cross section is created by cutting the element body 10 in the thickness direction along the longitudinal direction of the element body 10 at a position passing through the winding axis of the coil C from the mounting surface side of the element body 10. (2) This cross section is photographed at 1000x magnification using an SEM and / or EDX at the winding axis portion of the coil C so that the soft magnetic metal powder 20 is included in the field of view, and the measurement location of the soft magnetic metal powder 20 is identified. The insulating coating 22 of the soft magnetic metal powder 20 identified using SEM and / or EDX is observed using an infrared microscope, and the infrared absorption spectrum is measured using Fourier transform infrared spectroscopy (FT-IR), thereby confirming the presence of Si—O bonds and OH groups. Furthermore, the presence of C—O bonds, bonds between metal elements and C, and N can also be confirmed by measuring the same location using an XPS photoelectron spectrum.

[0046] Furthermore, in the inductor 1A of the first embodiment, the magnetic layers ML and the coil conductors CD are stacked and sintered to form the element body 10, and therefore there are portions within the element body 10 where the insulating coatings 22 of the soft magnetic metal powder particles 20 are bonded together (see FIG. 3). Furthermore, after the magnetic layers ML and the coil conductors CD are stacked and sintered, resin is impregnated between the soft magnetic metal powder particles 20. Therefore, by bonding the insulating coatings 22 of the soft magnetic metal powder particles 20 together, the rigidity of the element body 10 can be increased compared to when the soft magnetic metal powder particles are simply in contact with each other.

[0047] Description of Inductor of Second Embodiment Next, an inductor 1B of a second embodiment will be described with reference to Fig. 4. Note that the description of the configuration common to the inductor 1A of the first embodiment will be omitted as appropriate.

[0048] In the inductor 1B of the second embodiment, a coil C is formed by winding a conductor wire, and the coil C is embedded inside the element body 10.

[0049] The conductor wire is preferably made of a rectangular wire, which has the effect of allowing the wires to be wound densely without gaps between them and reducing DC resistance. However, the conductor wire is not limited to this example, and for example, a round wire or the like may also be used.

[0050] The conductor is preferably made of a metal wire (e.g., copper wire) coated with an insulating material such as resin, which, in combination with a resin (e.g., epoxy resin) contained in the element body 10 (described later), allows the coil C to be firmly molded within the element body 10.

[0051] The element body 10 further contains a resin in addition to the soft magnetic metal powder 20 described above. The resin is contained in the element body 10 and cured, causing the soft magnetic metal powder particles 20 to come into contact with each other. The resin may be, for example, a thermosetting epoxy resin and / or a phenoxy resin. The resin content may be 2 wt % or more and 3.5 wt % or less, more preferably 2.7 wt % or more and 3.0 wt % or less, based on the total weight of the soft magnetic metal powder 20 and the resin.

[0052] In the element body 10 of the inductor 1B of the second embodiment, the soft magnetic metal powder 20 may be composed of a first magnetic powder and a second magnetic powder having a smaller average particle size than the first magnetic powder. With this configuration, the second magnetic powder having a smaller average particle size than the first magnetic powder fills the gaps between the first magnetic powder particles, thereby improving the filling rate of the soft magnetic metal powder in the element body 10.

[0053] The soft magnetic metal powder 20 as the first magnetic powder may have an average particle size of 20 μm to 30 μm, more preferably 21.4 μm to 27.4 μm, while the second magnetic powder may have an average particle size of 1 μm to 10 μm, more preferably 1.5 μm to 1.8 μm.

[0054] The first magnetic powder is an Fe—Si—B amorphous alloy and may have an oxide film.

[0055] The second magnetic powder is carbonyl iron powder. The second magnetic powder may have an oxide film. The second magnetic powder may be composed of the same material as the first magnetic powder, or may be composed of a different material. The first magnetic powder and the second magnetic powder may be coated with the insulating coating 22 to form the soft magnetic metal powder, or both may be coated with the insulating coating 22 to form the soft magnetic metal powder. By forming the soft magnetic metal powder by coating at least one of the first magnetic powder and the second magnetic powder with different average particle sizes, the sliding property between the first magnetic powder and the second magnetic powder can be improved, thereby further increasing the filling rate of the soft magnetic metal powder in the base body 10.

[0056] Furthermore, based on the total weight of the first and second magnetic powders, the first magnetic powder may be 70 wt % to 85 wt %, preferably 70 wt % to 80 wt %, and the second magnetic powder may be 15 wt % to 30 wt %, preferably 20 wt % to 30 wt %.

[0057] The soft magnetic metal powders of the present disclosure were subjected to a verification test, which will be described in detail below. Specifically, the soft magnetic metal powders of Examples 1 to 3 and Comparative Examples 1 and 2 were produced.

[0058] Example 1 (Step 1) 2.80 g of tetraethyl orthosilicate (TEOS, Kanto Chemical) was dissolved in 55.0 g of isopropanol (IPA, Kanto Chemical), and 150.0 g of iron powder was added. Next, PVP (Pitzcol K-30, Daiichi Kogyo Seiyaku) was dissolved in 11.0 g of 9% aqueous ammonia (Daisei Kako), and this was subsequently added. The mixture was then stirred for 90 minutes. (Step 2) After stirring, the powder slurry was subjected to solid-liquid separation by suction filtration, and the powder surface was washed with acetone (Nacalai Tesque). The mixture was then air-dried overnight to obtain a powder with an insulating coating of organic-inorganic composite. (Step 3) The resulting powder was again dispersed in 55.0 g of IPA. Next, 1.2 g of dimethylamine borane (hereinafter referred to as DMAB, Shirai Pharmaceuticals) was dissolved in 10.0 g of 9% aqueous ammonia and added. The mixture was then stirred for 60 minutes. (Step 4) After stirring, the powder slurry was subjected to solid-liquid separation by suction filtration, and the powder surface was washed with acetone (Nacalai Tesque). The mixture was then air-dried overnight to obtain soft magnetic metal powder that had been reduced with DMAB.

[0059] Example 2 In (step 3) of Example 1, the amount of DMAB was changed to 2.4 g, and other steps were carried out in the same manner as in Example 1 to produce soft magnetic metal powder.

[0060] Example 3 In (Step 3) of Example 1, the amount of DMAB was changed to 3.6 g, and other steps were carried out in the same manner as in Example 1 to produce soft magnetic metal powder.

[0061] Comparative Example 1 Steps 3 and 4 of Example 1 were not carried out. In other words, soft magnetic metal powder was produced without carrying out a reduction treatment to reduce the OH groups in the insulating coating.

[0062] Comparative Example 2 In (Step 3) of Example 1, the amount of DMAB was changed to 7.0 g, and other steps were carried out in the same manner as in Example 1 to produce soft magnetic metal powder.

[0063] The soft magnetic metal powders of Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to the following verification tests.

[0064] (Demonstration Test 1: Infrared Absorbance Measurement) The obtained soft magnetic metal powder was measured using an infrared spectrophotometer (Bruker Japan Co., Ltd., Model No. VERTEX 70V) to measure the 1230 cm absorption due to the vibration of the Si—O bond. -1 Infrared absorbance A ０ , and 1600-1700 cm resulting from the vibration of the OH group contained in the silanol group. -1 Infrared absorbance A １ was measured.

[0065] (Demonstration Test 2: Measurement of Corrosion Potential, Corrosion Current Density, and Volume Resistivity) The soft magnetic metal powder and carbon paste were mixed with a spatula in a 2:1 (mass ratio) to prepare a carbon paste working electrode. A 3% by mass NaCl aqueous solution was added to a glass cell, and the carbon paste working electrode, Ag / AgCl electrode, and Pt counter electrode were inserted to prepare a three-electrode cell. Anodic polarization measurements were performed to determine the corrosion potential (the potential at which anodic polarization measurements began). The increase in corrosion current density after a potential sweep from negative to positive was also determined.

[0066] The measurement results are shown in the table below.

[0067]

[0068] Here, the more positive the "corrosion potential" in the table, the more the oxidation of the surface is suppressed, and the smaller the "corrosion current density" value, the more the oxidation of the surface is suppressed.

[0069] According to the measurement results shown in Table 1, the soft magnetic metal powders of Examples 1 to 3 were more inhibited in oxidation and / or corrosion than the soft magnetic metal powders of Comparative Examples 1 and 2, and had a volume resistivity of 10 9 The results showed an order of magnitude reduction.

[0070] Next, a demonstration test on an inductor using the soft magnetic metal powder of the present disclosure will be described in detail. Specifically, powder magnetic cores for use in the inductors described in Examples 4 to 6 and Comparative Examples 3 and 4 below were manufactured.

[0071] Example 4 (Step 1) The soft magnetic metal powder (reduced using 1.2 g of DMAB) described in Example 1 above was mixed with a solution of epoxy resin (thermosetting resin), imide resin (curing agent), and acetone, and the acetone was evaporated to obtain granules. The total mass of the epoxy resin and imide resin was 3 mass% by powder weight ratio. (Step 2) The granules were sized using a stainless steel sieve. The mesh size of the stainless steel sieve was 180 μm. A molded body was obtained by molding the granules using a toroidal mold. The inner diameter of the mold was 6.5 mm, and the outer diameter of the mold was 11 mm. The molding pressure was 3.0 t / cm. 2 The molded body was heated at 180°C for 1 hour to harden the epoxy resin, thereby obtaining a toroidal powder magnetic core.

[0072] Example 5 A dust core was manufactured through the same steps as in Example 4, except that in (step 1) of Example 4, the soft magnetic metal powder described in Example 2 (which had been subjected to a reduction treatment using 2.4 g of DMAB) was used.

[0073] Example 6 A dust core was manufactured through the same steps as in Example 4, except that in (step 1) of Example 4, the soft magnetic metal powder described in Example 3 (which had been subjected to a reduction treatment using 3.6 g of DMAB) was used.

[0074] Comparative Example 3 A dust core was manufactured through the same steps as in Example 4, except that in (step 1) of Example 4, the soft magnetic metal powder described in Comparative Example 1 (which had not been subjected to reduction treatment) was used.

[0075] Comparative Example 4 A dust core was manufactured through the same steps as in Example 4, except that in (step 1) of Example 4, the soft magnetic metal powder described in Comparative Example 2 (which had been subjected to a reduction treatment with 7.0 g of DMAB) was used.

[0076] The powder magnetic cores of Examples 4 to 6 and Comparative Examples 3 and 4 were subjected to the following verification tests.

[0077] (Demonstration Test 3: Confirmation of the Presence or Absence of Structural Defects) The presence or absence of structural defects was confirmed by visual inspection. Specifically, when the powder magnetic cores were visually inspected, those with cracks were judged to have "structural defects" and those without cracks were judged to have "no structural defects."

[0078] (Demonstration Test 4: Withstand Voltage Measurement) A voltage was applied to the powder core using a digital ultra-high resistance / microcurrent meter (model number: R8340A, manufacturer: ADC). The current in the powder core was continuously measured while the voltage was continuously increased. The withstand voltage of the powder core was defined as the voltage when the current in the powder core reached 1 mA.

[0079] The measurement results are shown in the table below.

[0080]

[0081] According to the measurement results shown in Table 2, the powder magnetic cores of Examples 4 to 6 were free from structural defects and had higher withstand voltages than the powder magnetic cores of Comparative Examples 3 and 4.

[0082] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. The technical scope of the present disclosure also includes all modifications within the scope and meaning equivalent to the claims.

[0083] The soft magnetic metal powder, inductor, and soft magnetic metal powder of the present disclosure are as follows: <1> A soft magnetic metal powder comprising soft magnetic metal particles and an insulating coating that covers the soft magnetic metal particles, wherein the insulating coating contains silanol groups, and the infrared absorbance derived from Si—O bonds contained in the insulating coating is A ０ The infrared absorbance derived from the OH group contained in the silanol group is represented by A １ When this is done, A １ / A ０is 0.052 or more and 0.085 or less. <2> The soft magnetic metal powder according to <1>, having an average particle size of 1 μm or more and 30 μm or less. <3> The soft magnetic metal powder according to <1> or <2>, wherein the insulating coating contains an organic-inorganic composite. <4> The soft magnetic metal powder according to any one of <1> to <3>, wherein the insulating coating contains N element. <5> The soft magnetic metal powder according to any one of <1> to <4>, wherein the soft magnetic metal particles are Fe or an Fe-Si amorphous alloy. <6> An inductor comprising: an element body including the soft magnetic metal powder according to any one of <1> to <5>; and a coil provided within the element body. <7> The inductor according to <6>, wherein the coil is configured by stacking a plurality of conductor layers. <8> The inductor according to <7>, wherein the insulating coatings of the soft magnetic metal powder are bonded to each other in the element body. <9> The inductor according to <6>, wherein the coil is formed of a wound conductor. <10> The inductor according to any one of <6> to <9>, wherein the element body comprises a first magnetic powder and a second magnetic powder having an average particle size smaller than that of the first magnetic powder, and wherein the first magnetic powder and / or the second magnetic powder is the soft magnetic metal powder. <11> The inductor according to any one of <6> to <10>, wherein the element body further contains a resin. <12> The inductor according to <6> to <10>, wherein the inductor further comprises an insulating coating forming step of forming an insulating coating of an organic-inorganic composite on the surface of soft magnetic metal particles, and a reduction treatment step of performing a reduction treatment to reduce OH groups in the insulating coating, and wherein the infrared absorbance derived from Si—O bonds is A ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０<13> A method for producing soft magnetic metal powder having an insulating coating covering the soft magnetic metal particles, wherein the insulating coating forming step uses a solution containing a compound having a Si atom and a compound having an OH group. <14> A method for producing soft magnetic metal powder according to <12> or <13>, wherein the insulating coating forming step uses a solution further containing pyrrolidone. <15> A method for producing soft magnetic metal powder according to any one of <12> to <14>, wherein the reduction treatment step performs reduction treatment with dimethylamine borane.

[0084] The soft magnetic metal powder, inductor, and method for manufacturing soft magnetic metal powder of the present disclosure can be suitably used as electronic components having better voltage resistance characteristics and reduced structural defects in the insulating coating caused by stresses generated during the manufacturing process.

[0085] 1, 1A, 1B Inductor 10 Body 11 First main surface 12 Second main surface 13 First end surface 14 Second end surface 15 First side surface 16 Second side surface 20 Soft magnetic metal powder 21 Soft magnetic metal particle 22 Insulating coating C Coil CD Coil conductor E External electrode E1 to E4 First external electrode to fourth external electrode G1 to G6 Body layer ML Magnetic layer TH Through-hole conductor TH1 to TH4 First through-hole conductor to fourth through-hole conductor

Claims

1. A soft magnetic metal powder comprising soft magnetic metal particles and an insulating coating covering the soft magnetic metal particles, wherein the insulating coating contains a silanol group, and the infrared absorbance derived from the Si-O bond contained in the insulating coating is A ０ The infrared absorbance derived from the OH group contained in the silanol group is represented by A １ When this is done, A １ / A ０ is 0.052 or more and 0.085 or less.

2. The soft magnetic metal powder according to claim 1, having an average particle size of 1 μm or more and 30 μm or less.

3. The soft magnetic metal powder according to claim 1 or 2, wherein the insulating coating contains an organic-inorganic composite.

4. The soft magnetic metal powder according to any one of claims 1 to 3, wherein the insulating coating contains N element.

5. The soft magnetic metal powder according to any one of claims 1 to 4, wherein the soft magnetic metal particles are Fe or an Fe-Si amorphous alloy.

6. An inductor comprising: an element body comprising the soft magnetic metal powder according to any one of claims 1 to 5; and a coil provided within the element body.

7. The inductor according to claim 6, wherein the coil is constructed by laminating a plurality of conductor layers.

8. The inductor according to claim 7, wherein the insulating coatings of the soft magnetic metal powder are bonded to each other in the element body.

9. The inductor of claim 6, wherein the coil is constructed from wound conductor wire.

10. An inductor as described in any one of claims 6 to 9, wherein the base body comprises a first magnetic powder and a second magnetic powder having an average particle size smaller than that of the first magnetic powder, and the first magnetic powder and / or the second magnetic powder is the soft magnetic metal powder.

11. The inductor according to any one of claims 6 to 10, wherein the body further contains a resin.

12. A method for producing a soft magnetic metal particle by a method comprising the steps of: forming an insulating film of an organic-inorganic composite on the surface of the soft magnetic metal particle; and performing a reduction treatment to reduce OH groups in the insulating film. ０ , the infrared absorbance due to the OH group contained in the silanol group is A １ When this is done, A １ / A ０ The method for producing soft magnetic metal powder having the insulating coating covering the soft magnetic metal particles, wherein 13. The method for producing soft magnetic metal powder according to claim 12, wherein the insulating coating forming step uses a solution containing a compound having a Si atom and a compound having an OH group.

14. The method for producing soft magnetic metal powder according to claim 12 or 13, wherein the insulating coating forming step further uses a solution containing pyrrolidone.

15. A method for producing soft magnetic metal powder according to any one of claims 12 to 14, wherein the reduction treatment step is performed using dimethylamine borane.

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