WO2025115318A1 - Soft magnetic metal powder, inductor, and method for producing soft magnetic metal powder - Google Patents

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

This disclosure relates to soft magnetic metal powder, inductors, and methods for manufacturing soft magnetic metal powder.

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

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

Patent No. 3342767 JP 2017-034228 A JP 2006-097123 A JP 2017-188588 A

When electronic components are mounted on power supply circuits, etc., they are required to have good electrostatic discharge characteristics. Therefore, the insulating coating of the soft magnetic metal particles needs to have excellent voltage resistance characteristics. Furthermore, when manufacturing inductors using soft magnetic metal particles coated with an insulating coating, stresses that arise during the manufacturing process can cause structural defects such as cracks in the insulating coating.

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

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,
the insulating coating contains a silanol group;
When the infrared absorbance due to the Si—O bond contained in the insulating coating is A ₀ and the infrared absorbance due to the OH group contained in the silanol group is A ₁ ,
A ₁ /A ₀ is equal to or greater than 0.052 and equal to or less than 0.085.

The inductor of the present disclosure is
An element body including the soft magnetic metal powder described above;
and a coil provided within the element body.

The method for producing the soft magnetic metal powder according to the present disclosure includes:
an insulating coating forming step of forming an insulating coating of an organic-inorganic composite on the surface of the soft magnetic metal particles;
a reduction treatment step of performing a reduction treatment to reduce OH groups in the insulating coating,
The soft magnetic metal powder is manufactured having an insulating coating that covers the soft magnetic _metal particles, in which _A1 / _A0 is 0.052 or more and 0.085 or less, where _A0 is the infrared absorbance derived from the Si-O bond and A1 is the infrared absorbance derived from the OH group contained in the silanol group.

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

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

The soft magnetic metal powder, inductor, and manufacturing method of the soft magnetic metal powder disclosed herein are described in detail below. The explanation will refer to the drawings as necessary, but the contents shown are merely schematic and illustrative for the understanding of the present disclosure, and the appearance and dimensional ratios may differ from the actual product.

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 line III-III in the region bounded by the dashed lines in FIG. 2, FIG. 4 is a perspective view of another embodiment of the inductor according to the present disclosure, and FIG. 5 is a manufacturing flow chart illustrating the manufacturing process of the soft magnetic metal powder according to the present disclosure.

<Description of the soft magnetic metal powder of the present disclosure>
First, the soft magnetic metal powder of the present disclosure will be described. The soft magnetic metal powder 20 includes soft magnetic metal particles 21 and an insulating coating 22 that coats the soft magnetic metal particles 21 (see FIG. 3).

An example of the soft magnetic metal particles 21 may be an Fe (iron) or Fe-Si (silicon) based amorphous alloy. Such a soft magnetic metal material can provide a suitable magnetic permeability when used in an inductor. 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 in the manufacturing process. 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 elements (e.g., Cr, Al, Li (lithium), Zn (zinc)) that are more easily oxidized than the Fe added when the magnetic paste is prepared. By adding Si to the soft magnetic metal particles 21, the oxidation of the Fe element contained in the soft magnetic metal particles 21 can be suppressed, and the magnetic permeability of the inductor manufactured using the soft magnetic metal particles 21 can be further increased. The resin component contained in the magnetic paste may disappear by heat treatment, or may remain.

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.

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 number: VERTEX 70V) to measure 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 can be identified by measuring the infrared absorbance A ₀ at 1230 cm ^-1 originating from the vibration of the Si-O bonds, and the infrared absorbance A ₁ at 1600 to 1700 cm ^-1 originating from the vibration of the OH groups contained in the silanol groups.

The soft magnetic metal powder 20 of the present disclosure may have A ₁ /A ₀ obtained by the above-mentioned Fourier transform infrared spectroscopy (FT-IR) of 0.052 or more and 0.085 or less. In other words, by specifying A ₁ /A ₀ , the optimal content range of OH groups contained in the silanol groups in the soft magnetic metal powder 20 is specified. Here, the OH groups in the soft magnetic metal powder 20 act to increase the binding strength with the resin, but have polarity 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, excessive reduction of the OH groups may cause structural defects such as cracks in the insulating coating 22 due to the reduced binding strength with the resin and the stress generated during the manufacturing process. Therefore, by setting A ₁ /A ₀ to 0.052 or more and 0.085 or less as in the present disclosure, the content of OH groups is optimized, and good withstand voltage characteristics and reduced structural defects in the insulating coating can be achieved at the same time.

As a preferred embodiment of the insulating coating 22, the insulating coating 22 may contain an organic-inorganic composite. In this specification, the term "organic-inorganic composite" 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 the metal alkoxide and a polymer having a carbonyl group, which is compatible at the molecular level. In other words, an 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 containing an organic-inorganic composite in the insulating coating 22, a hydrolysis and polymerization reaction can be caused, resulting in an insulating coating 22 that achieves high voltage resistance and reduced structural defects.

Metal alkoxides are represented by 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 ) are chemically more stable and therefore easier to handle during production.

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, and more particularly 3 or less. The smaller the carbon number, the easier the hydrolysis reaction can be. The alkoxy group is preferably at least one selected from the group consisting of, for example, a methoxy group, an ethoxy group, and a propoxy group. Specifically, the metal alkoxide is preferably tetraethyl orthosilicate or tetramethoxysilane.

Furthermore, the soft magnetic metal powder 20 of the present disclosure is subjected to a reduction treatment to reduce OH groups in the insulating coating 22, which will be described in detail later in the manufacturing method. As an example, the reduction treatment is performed using dimethylamine borane and/or sodium borohydride. Therefore, the insulating coating 22 of the present disclosure may contain N element (nitrogen element) resulting from the above-mentioned dimethylamine borane. If the insulating coating 22 contains nitrogen element, the OH groups are appropriately reduced and the withstand voltage can be improved.

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 by the procedure described below. The inductor sample is cut to obtain a sample cross section. Specifically, the sample cross section is obtained by cutting through the winding axis of the coil of the element so as to be perpendicular to the mounting surface and end surface of the element. For the obtained cross section, multiple (e.g., 5) areas (e.g., 130 μm x 100 μm) are photographed with an SEM, and the obtained SEM images are analyzed using image analysis software (e.g., image analysis software "Win R00F" (manufactured by Mitani Shoji Co., Ltd.)) to obtain the circle equivalent diameter of the soft magnetic metal powder. The average value of the obtained circle equivalent diameters is set as the average particle size of the soft magnetic metal powder. Note that the "average particle size" in this specification may mean the average particle size D50 (particle size equivalent to 50% cumulative percentage based on volume).

<Method of producing soft magnetic metal powder according to the present disclosure>
Next, the manufacturing method of the soft magnetic metal powder of the present disclosure will be described with reference to Fig. 5. The manufacturing method of the soft magnetic metal powder of the present disclosure includes an insulating coating forming step and a reduction treatment step. The manufacturing flow shown in Fig. 5 will be described below.

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

The slurry is prepared by dissolving a metal alkoxide containing Si (e.g., tetraethyl orthosilicate) in an alcohol solution having an OH group (e.g., isopropanol). In other words, a solution containing a compound having an Si atom and a compound having an OH group is prepared. Granular material (e.g., iron powder) constituting the soft magnetic metal particles 21 is added to the solution. The solution reacts in an alkaline environment to generate silanol groups. Note that the above-mentioned alcohol solution having an OH group 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.

Furthermore, to prepare the slurry, a solution containing a resin having a water-soluble polymer (for example, pyrrolidone or polyvinylpyrrolidone) is mixed with the solution to which the above-mentioned granular material has been added, and the mixture is stirred for a predetermined 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 may be mixed while being heated. The above-mentioned resin is not limited to pyrrolidone or polyvinylpyrrolidone, and may be, for example, polyvinyl alcohol or polyacrylamide.

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. Note that the product may be washed (for example, with acetone) before the solid-liquid separation. Moreover, instead of the above-mentioned suction filtration, pressure filtration such as with a filter press or centrifugal filtration may be performed.

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

After the reduction treatment, the soft magnetic metal particles of the present disclosure are obtained by solid-liquid separation using suction filtration or the like and drying.

As described above, according to the method for producing soft magnetic metal powder disclosed herein, when the infrared absorbance derived from the Si-O bond measured by Fourier transform infrared spectroscopy (FT-IR) _{is A0} and the infrared absorbance derived from the OH group contained in the silanol group is _A1 , it is possible to produce soft magnetic metal powder having an insulating coating covering soft magnetic metal particles in which _A1 / _A0 is 0.052 or more and 0.085 or less.

Furthermore, focusing on the point of manufacturing 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 follow the deformation caused by the load during magnetic core molding. As a result, when the soft magnetic metal powder disclosed herein is used to manufacture an inductor, it is possible to improve the volume resistivity (electrical resistance) while reducing structural defects.

In addition, the silica surface obtained by the hydrolysis polymerization reaction is generally composed of Si-O bonds and silanol residues. At this time, the amount of OH groups derived from the silanol residues on the surface can be appropriately adjusted by partially reducing the carbonyl groups contained in the organic-inorganic composite with a reducing agent. By appropriately reducing the amount of OH groups, it is possible to suppress the formation of paths for electronic conduction and improve the withstand voltage.

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 occurring during core molding. Therefore, by using an appropriate amount of reducing agent, the amount of OH in the insulating coating can be adjusted to the optimal range, making it possible to improve voltage resistance while suppressing structural defects.

<Description of Inductor in 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 comprises an element body 10 including the soft magnetic metal powder described above, and a coil provided within the element body 10.

The inductor of the present disclosure may be an inductor constructed by laminating multiple base layers G1 to G8 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 constructed 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.

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 corners and ridges of the element body 10 may be rounded. The corners are portions where three sides of the element body 10 intersect, and the ridges are portions where two sides of the element body 10 intersect.

In FIG. 1, the length, width, and height directions of the inductor 1A and the base body 10 are shown as L, W, and T directions, respectively. The length direction L, width direction W, and height direction T are mutually orthogonal. The mounting surface of the inductor 1A is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

The base body 10 shown in FIG. 1 has a first main surface 11 and a second main surface 12 that face the height direction T, a first end surface 13 and a second end surface 14 that are perpendicular to the height direction T and face the length direction L, and a first side surface 15 and a second side surface 16 that face the 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 base body 10 corresponds to the mounting surface (bottom surface) of the base body 10. Note that the second main surface 12 may also be the mounting surface of the base body 10.

The base body 10 has a laminated structure in which a plurality of base body layers, each having a magnetic layer ML and a coil conductor CD formed thereon, are laminated in a lamination direction (e.g., height direction T). In this embodiment, the base body 10 is constructed by laminating base body layers G1 to G8 as shown in FIG. 2. A coil is constructed by laminating a plurality of coil conductors CD. By constructing a coil by laminating 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 base body 10 have disappeared. Also, each of the base body layers G1 to G8 may be constructed by laminating a plurality of identical patterns.

The base body 10 includes a coil formed by stacking multiple coil conductors CD. In the example shown in FIG. 2, two coils (a first coil and a second coil) are arranged in the base body 10 along the stacking direction. More specifically, the first coil is formed by the coil conductors CD of base body layers G4 and G5, and the second coil is formed by the coil conductors CD of base body layers G2 and G3. Note that the inductor 1A of the first embodiment is not limited to this example, and for example, three or more coils may be arranged along the stacking direction. Also, a coil array may be formed by arranging multiple coils side by side inside the base body 10 in a direction intersecting the stacking direction (L direction in FIG. 1).

An external electrode E is provided on the mounting surface (first main surface 11) of the element body 10. In the example shown in FIG. 2, the external electrode E includes 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. Note that two external electrodes are provided for each coil. Therefore, if the number of coils is three, the number of external electrodes may be six.

The coil C and the external electrode E may be connected using through-hole conductors TH. That is, the first through-hole conductor TH1 to the fourth through-hole conductor TH4 may be provided in correspondence with the first external electrode E1 to the fourth external electrode E4. Furthermore, the first through-hole conductor TH1 to the fourth through-hole conductor TH4 may extend along the stacking direction.

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, when the infrared absorbance derived from the Si-O bond measured by Fourier transform infrared spectroscopy (FT-IR) _{is A0} and the infrared absorbance derived from the OH group contained in the silanol group is _A1 , the inductor contains soft magnetic metal powder in which _A1 / _A0 is 0.052 or more and 0.085 or less, and therefore has better voltage resistance characteristics and can further reduce structural defects caused by stress generated during the inductor manufacturing process.

An example of a method for identifying the insulating coating 22 of the soft magnetic metal particle 21 from the inductor of the present disclosure is as follows.
(1) A cut surface is prepared by cutting element body 10 in the thickness direction along the length of element body 10 at a position passing through the winding axis of coil C from the mounting surface side of element body 10 .
(2) This cut surface is photographed with a 1000x SEM and/or EDX so that the soft magnetic metal powder 20 is in the field of view of the winding shaft of the coil C, 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 with the SEM and/or EDX is observed with 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. In addition, by measuring the same location with an XPS photoelectron spectrum, the presence of C-O bonds, bonds between metal elements and C, and N can also be confirmed.

In addition, in the inductor 1A of the first embodiment, the magnetic layer ML and the coil conductor CD are laminated and sintered to form the base body 10, so that the base body 10 has a portion where the insulating coatings 22 of the soft magnetic metal powder 20 are bonded together (see FIG. 3). After the magnetic layer ML and the coil conductor CD are laminated 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 base body 10 can be increased compared to when the soft magnetic metal powder particles are simply in contact with each other.

Description of the Inductor of the Second Embodiment Next, an inductor 1B of the 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.

In the second embodiment, the inductor 1B is configured by winding a conductor wire to form a coil C, which is embedded inside the element body 10.

The conductor is preferably made of rectangular wire, which has the effect of allowing the wires to be wound densely without gaps between them, and of reducing DC resistance. Note that the conductor is not limited to this example, and for example, round wire, etc. may also be used.

The conductor is preferably constructed by covering a metal wire (e.g., copper wire) with an insulating material such as resin. In this case, in combination with the resin (e.g., epoxy resin) contained in the base body 10 described below, the coil C can be firmly molded within the base body 10.

The base body 10 further contains resin in addition to the soft magnetic metal powder 20 described above. The base body 10 contains resin, and the resin is cured to bring the soft magnetic metal powder 20 into contact with each other. The resin may be, for example, a thermosetting epoxy resin and/or a phenoxy resin. Furthermore, the resin 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.

In the base 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 base body 10.

The first magnetic powder, soft magnetic metal powder 20, may have an average particle size of 20 μm or more and 30 μm or less, more preferably 21.4 μm or more and 27.4 μm or less. On the other hand, the second magnetic powder may have an average particle size of 1 μm or more and 10 μm or less, more preferably 1.5 μm or more and 1.8 μm or less.

The first magnetic powder is an Fe-Si-B amorphous alloy. The first magnetic powder may have an oxide film.

The second magnetic powder is carbonyl iron powder. The second magnetic powder may have an oxide film. The second magnetic powder may be made of the same material as the first magnetic powder, or may be made of a different material. The first magnetic powder and the second magnetic powder may be made of the soft magnetic metal powder by having the insulating coating 22 applied to one of them, or by having the insulating coating 22 applied to both of them. By making the first magnetic powder and the second magnetic powder have different average particle sizes and having the insulating coating 22 applied to at least one of them, the slipperiness between the first magnetic powder and the second magnetic powder can be improved, and the filling rate of the soft magnetic metal powder in the base body 10 can be further improved.

Furthermore, based on the total weight of the first magnetic powder and the second magnetic powder, the first magnetic powder may be 70 wt% or more and 85 wt% or less, preferably 70 wt% or more and 80 wt% or less. Furthermore, the second magnetic powder may be 15 wt% or more and 30 wt% or less, preferably 20 wt% or more and 30 wt% or less.

The following describes in detail the demonstration tests for the soft magnetic metal powder disclosed herein. Specifically, the soft magnetic metal powders of Examples 1 to 3 and Comparative Examples 1 and 2 below were manufactured.

Example 1
(Step 1) 2.80 g of tetraethyl orthosilicate (hereinafter referred to as TEOS, Kanto Chemical) was dissolved in 55.0 g of isopropanol (hereinafter referred to as IPA, Kanto Chemical), and 150.0 g of iron powder was added. Next, PVP (Pittscol K-30, Daiichi Kogyo Seiyaku) was dissolved in 11.0 g of 9% ammonia water (Taisei Kako), and this was added subsequently. Then, the mixture was 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). After that, it was air-dried for one day to obtain a powder having an insulating coating of the organic-inorganic composite.
(Step 3) The obtained powder was dispersed again in 55.0 g of IPA. Next, 1.2 g of dimethylamine-borane (hereinafter referred to as DMAB, Shirai Chemicals) was dissolved in 10.0 g of 9% ammonia water, and this was then added. After that, the mixture was 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). After that, it was air-dried for one day to obtain soft magnetic metal powder reduced with DMAB.

Example 2
In step 3 of Example 1, the amount of DMAB was changed to 2.4 g. Except for this, the same steps as in Example 1 were carried out to produce soft magnetic metal powder.

Example 3
In step 3 of Example 1, the amount of DMAB was changed to 3.6 g. Except for this, the same steps as in Example 1 were carried out to produce soft magnetic metal powder.

Comparative Example 1
The steps 3 and 4 of Example 1 were not carried out. In other words, the soft magnetic metal powder was produced without carrying out a reduction treatment for reducing the OH groups in the insulating coating.

Comparative Example 2
In step 3 of Example 1, the amount of DMAB was changed to 7.0 g. Except for this, the same steps as in Example 1 were carried out to produce soft magnetic metal powder.

The following demonstration tests were conducted on the soft magnetic metal powders of Examples 1 to 3 and Comparative Examples 1 and 2 described above.

(Demonstration test 1: Infrared absorbance measurement)
The obtained soft magnetic metal powder was measured using an infrared spectrophotometer (Bruker Japan, model number: VERTEX 70V) for infrared absorbance A ₀ at 1230 cm ^-1 due to the vibration of Si-O bonds, and infrared absorbance A ₁ at 1600 to 1700 cm ^-1 due to the vibration of OH groups contained in silanol groups.

(Demonstration Test 2: Measurement of Corrosion Potential, Corrosion Current Density, and Volume Resistivity)
The obtained soft magnetic metal powder and carbon paste were mixed with a spatula in a mass ratio of 2:1 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. Anode polarization measurements were performed to determine the corrosion potential (measurement start potential of anode polarization). The increase in corrosion current density after the potential was swept from negative to positive was also determined.

The measurement results are shown in the table below.

In the table, the more positive the "corrosion potential" is, the more surface oxidation is suppressed, and the smaller the "corrosion current density" is, the more surface oxidation is suppressed.

According to the measurement results shown in Table 1, the soft magnetic metal powders of Examples 1 to 3 were found to be less susceptible to oxidation and/or corrosion than the soft magnetic metal powders of Comparative Examples 1 and 2, and had a volume resistivity reduced by an order of magnitude ^{of 10} .

Next, we will provide a detailed description of demonstration tests on inductors using the soft magnetic metal powder disclosed herein. Specifically, we manufactured powder magnetic cores for use in the inductors described in Examples 4 to 6 and Comparative Examples 3 and 4 below.

Example 4
(Step 1) The soft magnetic metal powder (reduced with 1.2 g of DMAB) described in Example 1 above was mixed with a solution of epoxy resin (thermosetting resin), imide resin (hardener) and acetone, and acetone was evaporated to obtain granules. The total mass of the epoxy resin and imide resin was 3% by weight of the powder.
(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-shaped 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/ ^cm2 . The molded body was heated at 180°C for 1 hour to harden the epoxy resin and obtain a toroidal-shaped powder magnetic core.

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 reduction treatment with 2.4 g of DMAB) was used.

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 reduction treatment with 3.6 g of DMAB) was used.

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.

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 reduction treatment with 7.0 g of DMAB) was used.

The following demonstration tests were conducted on the powder magnetic cores of Examples 4 to 6 and Comparative Examples 3 and 4 described above.

(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 as having "structural defects" and those without cracks were judged as having "no structural defects."

(Demonstration test 4: Voltage resistance measurement)
A voltage was applied to the powder core using a digital ultra-high resistance/microammeter (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.

The measurement results are shown in the table below.

The measurement results shown in Table 2 show that the powder magnetic cores of Examples 4 to 6 were free of structural defects and had higher withstand voltage than the powder magnetic cores of Comparative Examples 3 and 4.

The embodiments disclosed herein are illustrative in all respects and are not intended to be a basis for restrictive interpretation. Therefore, the technical scope of this disclosure should not be interpreted solely based on the embodiments described above, but should be defined based on the claims. Furthermore, the technical scope of this disclosure includes all modifications that are equivalent in meaning and scope to the claims.

Aspects of the soft magnetic metal powder, the inductor, and the 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,
the insulating coating contains a silanol group;
When the infrared absorbance due to the Si—O bond contained in the insulating coating is A ₀ and the infrared absorbance due to the OH group contained in the silanol group is A ₁ ,
A soft magnetic metal powder, wherein A ₁ /A ₀ is 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 elements.
<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-based amorphous alloy.
<6> An element body comprising the soft magnetic metal powder according to any one of <1> to <5>,
and a coil provided within the element body.
<7> The inductor described in <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 element body includes a first magnetic powder and a second magnetic powder having an average particle size smaller than that of the first magnetic powder,
The inductor according to any one of <6> to <9>, 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 further contains a resin.
<12> An insulating coating forming step of forming an insulating coating of an organic-inorganic composite on the surface of soft magnetic metal particles;
a reduction treatment step of performing a reduction treatment to reduce OH groups in the insulating coating,
A method for producing a soft magnetic metal powder having an insulating coating that covers the soft magnetic metal particles, wherein _{A 1 /} A ₀ is 0.052 or more and 0.085 or less, where A ₀ is the infrared absorbance derived from a Si-O bond and A 1 is the infrared absorbance derived from an OH group contained in a silanol group.
<13> The method for producing a soft magnetic metal powder according to <12>, in which the insulating coating formation step uses a solution containing a compound having a Si atom and a compound having an OH group.
<14> The method for producing a soft magnetic metal powder according to <12> or <13>, wherein the insulating coating forming step further uses a solution containing pyrrolidone.
<15> The method for producing a soft magnetic metal powder according to any one of <12> to <14>, wherein the reduction treatment step is performed using dimethylamine borane.

The soft magnetic metal powder, inductor, and manufacturing method of the soft magnetic metal powder disclosed herein can be suitably used as electronic components that have better voltage resistance characteristics and have fewer structural defects in the insulating coating caused by stresses that arise during the manufacturing process.

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 electrodes E1 to E4 First external electrode to fourth external electrode G1 to G6 Body layer ML Magnetic layer TH Through-hole conductors TH1 to TH4 First through-hole conductor to fourth through-hole conductor

Claims (15)

A soft magnetic metal powder comprising soft magnetic metal particles and an insulating coating that covers the soft magnetic metal particles,
the insulating coating contains a silanol group;
When the infrared absorbance due to the Si—O bond contained in the insulating coating is A ₀ and the infrared absorbance due to the OH group contained in the silanol group is A ₁ ,
A soft magnetic metal powder, wherein A ₁ /A ₀ is 0.052 or more and 0.085 or less. The soft magnetic metal powder according to claim 1, having an average particle size of 1 μm or more and 30 μm or less. The soft magnetic metal powder according to claim 1 or 2, wherein the insulating coating contains an organic-inorganic composite. The soft magnetic metal powder according to any one of claims 1 to 3, wherein the insulating coating contains N element. 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. An element comprising the soft magnetic metal powder according to any one of claims 1 to 5;
and a coil provided within the element body. The inductor according to claim 6, wherein the coil is constructed by stacking multiple conductor layers. The inductor according to claim 7, wherein the insulating coatings of the soft magnetic metal powder are bonded together in the element body. The inductor of claim 6, wherein the coil is made of wound conductor wire. the element body includes a first magnetic powder and a second magnetic powder having an average particle size smaller than that of the first magnetic powder,
The inductor according to any one of claims 6 to 9, wherein the first magnetic powder and/or the second magnetic powder is the soft magnetic metal powder. The inductor according to any one of claims 6 to 10, wherein the body further contains a resin. an insulating coating forming step of forming an insulating coating of an organic-inorganic composite on the surface of the soft magnetic metal particles;
a reduction treatment step of performing a reduction treatment to reduce OH groups in the insulating coating,
The method for producing a soft magnetic metal powder having an insulating coating covering the soft magnetic metal particles, wherein _{A 1 /} A ₀ is 0.052 or more and 0.085 or less, where A ₀ is the infrared absorbance derived from a Si-O bond and A 1 is the infrared absorbance derived from an OH group contained in a silanol group. The method for producing soft magnetic metal powder according to claim 12, wherein the insulating coating forming process uses a solution containing a compound having a Si atom and a compound having an OH group. The method for producing soft magnetic metal powder according to claim 12 or 13, wherein the insulating coating forming process further uses a solution containing pyrrolidone. The 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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