Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/16—Metallic particles coated with a non-metal
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/14—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys
  • H01F1/20—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder
  • H01F1/22—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together
  • H01F1/24—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials metals or alloys in the form of particles, e.g. powder pressed, sintered, or bound together the particles being insulated
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
  • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
  • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
  • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
  • H01F1/33—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials mixtures of metallic and non-metallic particles; metallic particles having oxide skin
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type
  • H01F17/04—Fixed inductances of the signal type with magnetic core
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F27/00—Details of transformers or inductances, in general
  • H01F27/24—Magnetic cores
  • H01F27/255—Magnetic cores made from particles
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets

Definitions

• This disclosure relates to an inductor and a method for manufacturing an inductor.
• Patent Document 1 discloses a coil component in which a spiral coil part covered with a magnetic part is in direct contact with the magnetic part, the magnetic part being mainly composed of magnetic alloy particles and not containing a glass component, and an oxide film of the magnetic alloy particles is present on the surface of each magnetic alloy particle. It also discloses that the oxide film contains at least Fe3O4 , which belongs to the magnetic material, and Fe2O3 and Cr2O3 , which belong to the non-magnetic material.
• the coil component described in Patent Document 1 contains Cr, a non-magnetic component, as an oxide film between the magnetic alloy particles, so further improvement of the magnetic properties was required. More specifically, it was discovered that the magnetic properties of the inductor can be improved by improving the concentration of the non-magnetic component in the oxide film.
• the present disclosure aims to provide an inductor with improved magnetic properties and a method for manufacturing an inductor.
• the inductor according to the present disclosure comprises: An element body including a plurality of metal magnetic powders; A coil provided within the element body,
• the metal magnetic powder includes metal magnetic particles containing Fe and an oxide coating containing an oxidizable material that is more easily oxidized than Fe,
• an intergranular layer region a region where the distance between the surface of a first metal magnetic particle and the surface of a second metal magnetic particle adjacent to the first metal magnetic particle becomes small
• a region where the distance becomes large is defined as a non-intergranular layer region
• the concentration of the easily oxidizable material in the non-intergranular layer region is higher than the concentration of the easily oxidizable material in the intergranular layer region.
• a method for manufacturing an inductor according to the present disclosure includes: A method of manufacturing the inductor described above, comprising the steps of: a preparation step of preparing a magnetic material constituting an element body by adding the easily oxidizable material to the metal magnetic particles; a pressurizing step of pressurizing a precursor body formed using the magnetic material, thereby distributing the easily oxidizable material more in the non-intergranular layer region than in the intergranular layer region; and a heat treatment step of heating the magnetic material to form an oxide film containing the easily oxidizable material on the surface of the metal magnetic particles.
• This disclosure provides an inductor with improved magnetic properties and a method for manufacturing an inductor.
• 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.
• FIG. 3 is a cross-sectional view showing one field of view at the center of the cut surface, taken through the center of the element body and the winding axis of the coil in FIG. 1 and perpendicular to the mounting surface and end surfaces of the element body.
• FIG. 4 is an enlarged cross-sectional view of the area enclosed by the dashed line in FIG.
• FIG. 5A is a graph showing the concentration distributions of Si, Fe, and Zn in the intergranular layer region.
• FIG. 5B is a graph showing the concentration distributions of Si, Fe, and Zn in the non-intergranular layer region.
• FIG. 5C is a graph showing the concentration distributions of Si, Fe and Zn at other positions in the non-intergranular layer region.
• FIG. 6 is a manufacturing flow illustrating the manufacturing process of the inductor of the present disclosure.
• FIG. 7 is an element mapping image of the inductor of the comparative example.
• FIG. 8 is an element mapping image of the inductor of the example.
• FIG. 9 is a graph showing the change in magnetic permeability before and after the heat treatment.
• FIG. 10 is a table showing the changes in magnetic permeability in the comparative example and examples 1 to 4 on which the graph in FIG. 9 is based.
• inductor of the present disclosure is described below. Note that the present disclosure is not limited to the configurations below, and may be modified as appropriate without departing from the spirit of the present disclosure. In addition, a combination of multiple individual preferred configurations described below also constitutes the present disclosure.
• the inductor disclosed herein is used, for example, in a DC-DC converter.
• the inductor disclosed herein can also be used for purposes other than DC-DC converters.
• the inductor of the present disclosure will be described with reference to Figures 1 to 5C.
• the inductor of the present disclosure comprises an element body 10 including a plurality of magnetic metal powder particles MP (see Figure 3), and a coil provided within the element body 10.
• 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.
• the first main surface 11 of the base body 10 corresponds to the mounting surface (bottom surface) of the base body 10.
• the second main surface 12 may also be the mounting surface of the base body 10.
• the base body 10 includes a coil formed by stacking multiple coil conductors CD.
• two coils a first coil and a second coil
• the first coil is formed by the coil conductors CD of base body layers G4 and G5
• the second coil is formed by the coil conductors CD of base body layers G2 and G3.
• the inductor 1 of the first embodiment is not limited to this example, and for example, three or more coils may be arranged along the stacking direction.
• 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.
• 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.
• Through-hole conductors TH are used to connect the coil (coil conductor CD) to the external electrode E. That is, the first through-hole conductor TH1 to the fourth through-hole conductor TH4 are provided in correspondence with the first external electrode E1 to the fourth external electrode E4. The first through-hole conductor TH1 to the fourth through-hole conductor TH4 are also provided extending along the stacking direction.
• the magnetic layer ML of each of the base layers G1 to G8 is provided with metal magnetic powder MP (see FIG. 3) made of a magnetic material.
• the metal magnetic powder MP includes metal magnetic particles DP, an oxide film OL, and a resin.
• the average particle size of the metal magnetic powder MP may be preferably 0.2 ⁇ m or more and 20 ⁇ m or less, more preferably 0.2 ⁇ m or more and 15 ⁇ m or less, and even more preferably 1 ⁇ m or more and 6 ⁇ m or less.
• the average particle size of the metal magnetic powder MP can be measured by the following procedure.
• the inductor sample is cut to obtain a sample cross section.
• the sample cross section is obtained by cutting through the center of the element body and the winding axis of the coil so as to be perpendicular to the mounting surface and end surface of the element body.
• the sample cross section may be made flat by ion milling or the like.
• three arbitrary points in the center of the cut surface, which corresponds to the center of the element body 10 are photographed by SEM (magnification of about 1000 times) and composition analysis is performed by EDX.
• SEM magnification of about 1000 times
• the average value of the obtained circle equivalent diameters for the confirmed metal magnetic powder MP is taken as the average particle size of the metal magnetic particles.
• the average particle size in this specification may mean the average particle size D50 (particle size equivalent to 50% cumulative percentage based on volume).
• the metal magnetic particles DP contain at least Fe (iron). More specifically, they may be particles or alloy particles containing Fe and Si. Examples of the metal magnetic particles DP may be Fe-Si alloys, Fe-Si-Cr (chromium) alloys, Fe-Si-Al (aluminum) alloys, Fe-Si-B (boron)-P (phosphorus)-Cu (copper)-C (carbon) alloys, Fe-Si-B-Nb (niobium)-Cu alloys, etc. The metal magnetic particles DP 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.
• impurities such as Cr, Mn (manganese), Cu, Ni (nickel), P, S (sulfur) or Co (cobalt) that are not intended in the manufacturing process.
• the metal magnetic particles DP may also be contained in the magnetic paste, as will be described in detail in the explanation of the manufacturing method.
• the magnetic paste may contain an easily oxidizable material (e.g., any one of Zn (zinc), Zr (zirconium), Al (aluminum), Ti (titanium), Mg (magnesium), Cr (chromium), and Mo (molybdenum)) that is more easily oxidized than Fe.
• the easily oxidizable material can be attached to the surface of the metal magnetic particles DP, and the easily oxidizable material on the surface of the metal magnetic particles DP is preferentially oxidized, so that the oxide of the easily oxidizable material remains on the surface of the metal magnetic particles DP, and the oxidation of the Fe element contained in the metal magnetic particles is reduced.
• the resin component contained in the magnetic paste may disappear or remain due to the heat treatment of the element body.
• the material of the easily oxidizable material that is more easily oxidized than Fe is selected to be different from the material contained in the metal magnetic particles DP, for example, if the material of the metal magnetic particles DP is an Fe-Si-Cr alloy, the easily oxidizable material is selected to be a material other than Si or Cr.
• the surfaces of the metal magnetic particles DP are covered with an insulating coating.
• insulating refers to a volume resistivity of 1 M ⁇ cm or more. If the surfaces of the metal magnetic particles DP are covered with an insulating coating, the insulation between the metal magnetic particles DP can be increased.
• a specific example of the insulating coating is an oxide coating OL, as shown in FIG. 3. Note that a configuration in which an insulating material is provided outside the oxide coating OL, that is, the metal magnetic particles DP and the oxide coating OL may be coated with an insulating material not shown, may also be used.
• the thickness of the oxide film OL can be measured, for example, by photographing a cross section obtained by polishing an inductor sample with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and measuring the thickness of the oxide film OL covering the surface of the metal magnetic particles DP from the obtained SEM image.
• the thickness of the oxide film OL is measured by photographing any three points in the center of the cut surface cut perpendicular to the mounting surface and end surface of the element through the center of the element and the winding axis of the coil. In each field of view, the thickness of the oxide film OL is measured at three arbitrary points in the center.
• the thickness of the oxide film OL can be determined by averaging these nine points (three arbitrary points in the center of the cut surface) x (three arbitrary points in the center of each field of view).
• Suitable easily oxidizable materials may include at least one selected from the group consisting of Zr, Al, Ti, Mg, Cr, and Mo. More specifically, a metal with a greater ionization tendency than Fe may be used. When such a material is used as the easily oxidizable material, the easily oxidizable material is oxidized preferentially over the metal magnetic powder, thereby reducing the oxidation of the metal magnetic particles DP that contain Fe.
• the base body 10 which is formed by stacking the above-mentioned base body layers G1 to G8, may be impregnated with resin after heat treatment of the base body 10, so that the resin is present between adjacent metal magnetic powders MP bonded with an insulating coating.
• the resin impregnated after heat treatment of the base body 10 may be one or more resins selected from the group consisting of epoxy resin, phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, alkyd resin, etc.
• a cut surface is obtained by cutting the element through the center of the element and the winding axis of the coil perpendicular to the mounting surface and end surface of the element, and photographing three arbitrary points in the center of the cut surface, and it can be seen that in each field of view, there are areas around the multiple metal magnetic powders MP, indicated by dots, where resin impregnated in the element and voids are present, as shown in Figure 3.
• image analysis software for example, image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.) is used to select from the multiple metal magnetic powders MP those in which the distance between the center points of gravity of two metal magnetic particles DP is 100 nm or less, thereby identifying one metal magnetic particle DP and the other metal magnetic particle DP adjacent to that metal magnetic particle DP. Then, as shown in FIG.
• the region where the distance between the surface of one metal magnetic particle DP and the surface of the other metal magnetic particle DP adjacent to the metal magnetic particle DP becomes small is defined as the intergranular layer region R1
• the region where the distance between the surface of one metal magnetic particle DP and the surface of the other metal magnetic particle DP adjacent to the metal magnetic particle DP becomes large is defined as the non-intergranular layer region R2
• the concentration of the easily oxidizable material in the non-intergranular layer region R2 is higher than the concentration of the easily oxidizable material in the intergranular layer region R1.
• the "intergranular layer region” refers to the region between two particles that are opposed between the two virtual lines L2, as shown in FIG. 4, in which the line segment connecting the centroids of adjacent particles is defined as the virtual line L1, and virtual lines L2 of ⁇ 10° are drawn on both sides of the virtual line L1 as the center of the centroid of the metal magnetic particle.
• the maximum distance between the two particles is, for example, 50 nm or less.
• the virtual lines L1 and L2 can be drawn using image analysis software (for example, image analysis software WinROOF2021 (manufactured by Mitani Shoji Co., Ltd.)) when determining the circle-equivalent diameter of the above-mentioned metal magnetic powder MP.
• the "non-intergranular layer region” in this specification refers to a region other than the intergranular layer region, in which the interparticle distance is greater than that of the intergranular layer region.
• the "concentration of the easily oxidizable material" in this specification can be measured by the procedure described below.
• a cut surface is created by cutting the element body 10 in the thickness direction along the length of the element body 10 at a position passing through the coil winding axis from the mounting surface (first main surface 11) side of the element body 10.
• TEM photography magnification of about 600,000 times
• Quantitative analysis is performed at the identified position using EDX.
• composition analysis is performed by line analysis so as to straddle the outer edge of the metal magnetic particle DP, and the maximum concentration value of the concentration of the easily oxidizable material in the obtained composition analysis graph is measured.
• concentration of the easily oxidizable material in the intergranular layer region is measured at two locations inside the virtual line L1 and the virtual line L2 and equally spaced from the virtual line L1, and the average value of the maximum concentration values is taken as the concentration of the easily oxidizable material in the intergranular layer region.
• the "concentration of the easily oxidizable material in the non-intergranular layer region” is measured at two equally spaced locations, one outside one virtual line L2 and the other outside the other virtual line L2, and the average of the maximum concentration values is taken as the concentration of the easily oxidizable material in the non-intergranular layer region.
• the details of the analysis will be described in detail in the [Example] below, but the line analysis results for the intergranular layer region R1 are as shown in FIG. 5A, and the line analysis results for the non-intergranular layer region R2 are as shown in FIG. 5B and FIG. 5C.
• the "concentration of the easily oxidizable material” in this specification does not include O (oxygen), C (carbon), or other impurities.
• the line analysis results show that the concentration of the easily oxidizable material in the non-intergranular layer region R2 (maximum value of the Zn concentration in FIG. 5B or FIG. 5C) is higher than the concentration of the easily oxidizable material in the intergranular layer region R1 (maximum value of the Zn concentration in FIG. 5A).
• One reason for this line analysis result is thought to be that in the pressurizing step of the "Inductor Manufacturing Method" described below, the magnetic material is pressurized, pushing the easily oxidizable material in the intergranular layer region R1 toward the non-intergranular layer region R2, resulting in such a concentration of the easily oxidizable material.
• the concentration of the easily oxidizable material in the non-intergranular layer region R2 is relatively high at 5 atom% or more and 30 atom% or less, so that the easily oxidizable material is preferentially oxidized over Fe, and it is possible to reduce the oxidation of Fe.
• the method for manufacturing an inductor according to the present disclosure includes a preparation step, a pressurizing step, and a heat treatment step. As will be described later, the method may also include an optional degreasing step.
• the magnetic material (magnetic paste) constituting the magnetic layers ML of the element layers G1 to G8 described with reference to FIG. 2 and the conductor paste constituting the coil conductor CD are prepared.
• a metal powder such as an Fe-Si alloy or an Fe-Si-Cr alloy with a cumulative 50% particle diameter by volume, D50, is prepared between 2 ⁇ m and 20 ⁇ m.
• An easily oxidizable material that oxidizes more easily than Fe for example, Zn particles: 0.5 wt% or more
• a binder such as cellulose or polyvinyl butyral (PVB) and a solvent such as a mixture of terpineol and butyl diglycol acetate (BCA) are added, and the mixture is kneaded to make a magnetic paste.
• a paste containing Ag as a conductive material is prepared.
• the above evaluation results of the inductor confirmed that the maximum Zn concentration in the non-intergranular layer region R2 was higher than the maximum Zn concentration in the intergranular layer region R1. Therefore, in the non-intergranular layer region R2, oxidizable materials that are more easily oxidized than Fe are oxidized preferentially over Fe, making it possible to reduce the oxidation of Fe compared to conventional inductors. Furthermore, in the intergranular layer region R1, the concentration of oxidizable materials is low, making it possible to reduce nonmagnetic components and improve the magnetic properties compared to conventional inductors.

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• 2024
  • 2024-10-21 CN CN202480041199.4A patent/CN121420364A/zh active Pending
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  • 2024-10-21 WO PCT/JP2024/037430 patent/WO2025150243A1/ja active Pending

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