Composite metal magnetic body, inductor, method for manufacturing composite metal magnetic body, and method for manufacturing inductor

Abstract

Provided are a composite metal magnetic body, an inductor, a method for manufacturing a composite metal magnetic body, and a method for manufacturing an inductor that enable an improvement in magnetic characteristics. A composite metal magnetic body CP according to the present disclosure comprises metal magnetic particles DP containing Fe, Ni, and Al, and an insulating coating film (oxide coating film OL) covering the metal magnetic particles DP, wherein: the plurality of metal magnetic particles DP are bonded together by means of the insulating coating film; the metal magnetic particles DP have Al agglomeration regions A1 inside which Al is agglomerated; and a peak derived from an FeAl phase and a peak derived from an FeNi phase are present in X-ray diffraction.

Description

Composite metal magnetic body, inductor, and method for manufacturing a composite metal magnetic body and method for manufacturing an inductor

[0001] The present disclosure relates to a composite metal magnetic body, an inductor, a method for manufacturing a composite metal magnetic body, and a method for manufacturing an inductor.

[0002] Patent Document 1 discloses an Fe—Ni alloy powder core used in noise filters, choke coils for switching power supplies, and the like, in which the composition of the Fe—Ni alloy powder contains 70 to 85% Ni by weight.

[0003] Japanese Unexamined Patent Publication No. 62-99401

[0004] Ni is rare and expensive compared to Fe, and using a large amount of Ni may increase the manufacturing cost. On the other hand, reducing the Ni content is also an option, but reducing the Ni content may result in a decrease in magnetic properties such as magnetic permeability.

[0005] In view of the above, an object of the present disclosure is to provide a composite metal magnetic body and an inductor that can improve magnetic properties, as well as a method for manufacturing a composite metal magnetic body and a method for manufacturing an inductor.

[0006] The composite metal magnetic body of the present disclosure comprises metal magnetic particles containing Fe, Ni, and Al, and an insulating coating that covers the metal magnetic particles, and is a composite metal magnetic body in which a plurality of the metal magnetic particles are bonded via the insulating coating or a resin, and the metal magnetic particles have Al aggregation regions in which Al is aggregated, and X-ray diffraction shows peaks derived from an FeAl phase and peaks derived from an FeNi phase.

[0007] The inductor of the present disclosure includes the composite metal magnetic body described above.

[0008] The method for manufacturing the above-mentioned composite metal magnetic body of the present disclosure includes a heat treatment step in which the metal magnetic particles are heated at 400°C or higher and 1000°C or lower in a low-oxygen atmosphere or a reducing atmosphere to form an insulating coating mainly composed of an oxide containing an oxide of Al on the surface of the metal magnetic particles.

[0009] The method for manufacturing the above-mentioned inductor of the present disclosure includes a heat treatment process in which the metal magnetic particles are heated to 400°C or higher and 1000°C or lower in a low-oxygen atmosphere or a reducing atmosphere to form an insulating coating mainly composed of an oxide containing an oxide of Al on the surface of the metal magnetic particles.

[0010] The composite metal magnetic body of the present disclosure can improve magnetic properties. Specifically, X-ray diffraction shows peaks derived from the FeAl phase and peaks derived from the FeNi phase, and the metal magnetic particles have Al agglomerated regions in which Al is aggregated. Therefore, the FeAl phase increases the lattice constant of the FeNi phase, thereby reducing apparent magnetostriction. Therefore, the magnetic properties of the composite metal magnetic body can be improved.

[0011] FIG. 1 is a perspective view of an inductor according to the present disclosure. FIG. 2 is an exploded perspective view of the inductor according to the present disclosure. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. FIG. 4 is a table showing the results of a demonstration test. FIG. 5 is a photograph showing the results of wavelength-dispersive X-ray fluorescence analysis. FIG. 6 is a graph showing the results of X-ray diffraction measurement. FIG. 7 is a graph showing the relationship between the Al compounding ratio and the coercive force Hc. FIG. 8 is a graph showing the relationship between the top position of the FeNi peak and the coercive force Hc.

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

[0013] <Description of the composite metal magnetic body of the present disclosure> First, the composite metal magnetic body CP of the present disclosure will be described. Note that the "composite metal magnetic body" as used herein refers to a form in which metal magnetic particles DP are coated with an insulating coating (oxide coating OL) and metal magnetic powders MP are bonded together via the insulating coating, as shown in Figure 3.

[0014] The metal magnetic powder MP includes metal magnetic particles DP and an insulating coating (oxide coating OL). Depending on the method for forming the insulating coating, the insulating coating may contain a resin component.

[0015] The average particle size of the metal magnetic particles DP is preferably 0.2 μm to 20 μm, more preferably 0.5 μm to 15 μm, and even more preferably 1 μm to 6 μm. Such an average particle size can achieve high magnetic permeability and low core loss.

[0016] The average particle size of the metal magnetic particles DP can be measured using the procedure described below. An inductor sample is cut to obtain a cross section. Specifically, the sample cross section is obtained by cutting the sample through the center of the element body and the winding axis of the coil, perpendicular to the mounting surface and end surface of the element body. The sample cross section may be flattened by ion milling or the like. Three randomly selected central locations of the cut surface, which corresponds to the center of the element body 10, are photographed using an SEM (approximately 1000x magnification) and subjected to composition analysis using EDX. The position of the metal magnetic particles DP in the SEM image can be identified by confirming the position of Fe in the photographed field of view using the EDX composition analysis results. Then, the obtained SEM images are analyzed at three randomly selected central locations in each field of view using image analysis software (e.g., image analysis software WinROOF2021 (manufactured by Mitani Corporation)), and the identified metal magnetic particles DP are analyzed to determine the circle-equivalent diameter of the metal magnetic particles. The average of the obtained circle-equivalent diameters is taken as the average particle size of the metal magnetic particles. The average particle size in this specification may refer to the average particle size D50 (particle size corresponding to a cumulative percentage of 50% on a volume basis).

[0017] The metal magnetic particles DP contain at least Fe, Ni, and Al. The metal magnetic particles DP may be contained in the magnetic paste, as will be described in detail in the explanation of the manufacturing method. The resin component contained in the magnetic paste may be lost by heat treatment or may remain.

[0018] The metal elements (Fe, Ni, and Al) constituting the heat-treated metal magnetic particles DP can be measured using a wavelength-dispersive X-ray fluorescence analyzer (manufactured by JEOL, model number JXA-8530F). Specifically, the measurement can be performed using the procedure described below. A cross section is created by cutting the element body 10 (see FIG. 1 ) from the mounting surface (first main surface 11) side through the coil winding axis along the length of the element body 10 in the thickness direction of the element body 10. This cross section is photographed with a TEM at 600,000x magnification so that the metal magnetic particles DP are within the field of view at the coil winding axis, and the position of the metal magnetic particles DP is identified. At the identified position, quantitative analysis of the metal elements is performed using a wavelength-dispersive X-ray fluorescence analyzer. The quantitative analysis results will be described in the Examples below, and the analysis results shown in FIG. 4 are obtained.

[0019] Furthermore, analysis results using a wavelength-dispersive X-ray fluorescence analyzer show that the metal magnetic particles DP have Al agglomeration regions A1 (see FIG. 5 ) inside which Al is agglomerated. The term "Al agglomeration region" as used herein refers to the Al concentration in the Al agglomeration region A1 being 1.5 times or more higher than the Al concentration in the outside A2 of the Al agglomeration region in the analysis results shown in FIG. 4 . Specifically, FIG. 4 shows that the Al concentration in the outside A2 of the Al agglomeration region is less than approximately 100 LEVEL, whereas the Al concentration in the Al agglomeration region A1 is approximately 150 LEVEL or higher.

[0020] The metal magnetic particles DP contain an FeAl phase and an FeNi phase. These phase compositions can be measured using an X-ray diffractometer (Rigaku Corporation, Model No. SmartLab). Specifically, the measurement can be performed using the procedure described below. A cross section is created by cutting the element body 10 (see FIG. 1 ) from the mounting surface (first main surface 11) side through the coil winding axis along the length of the element body 10 in the thickness direction of the element body 10. X-rays are irradiated onto this cross section at the position of the metal magnetic particles DP, and a θ-2θ scan is performed while maintaining a 1:2 ratio between the X-ray incident angle and the detector angle relative to the measurement position. This measurement produces a diffraction profile such as that shown in FIG. 5, where the horizontal axis represents the diffraction angle and the vertical axis represents the diffraction intensity. Note that in FIG. 5, a single metal magnetic particle was extracted from a sample cross section prepared using the method described above and solidified with resin to more easily visualize the state of the metal magnetic particle.

[0021] According to the analysis results using a wavelength dispersive X-ray fluorescence analyzer and the measurement results using an X-ray diffractometer, the metal magnetic particles DP of the present disclosure have Al aggregation regions A1 in which Al is aggregated inside the heat-treated metal magnetic particles DP, and X-ray diffraction shows peaks derived from the FeAl phase and peaks derived from the FeNi phase. Therefore, the FeAl phase increases the lattice constant of the FeNi phase, thereby reducing the apparent magnetostriction of the composite metal magnetic body. Therefore, the composite metal magnetic body of the present disclosure can improve its magnetic properties. Detailed explanations of the effects will be given in the examples below.

[0022] As a preferred embodiment of the content ratio of the metal elements of the metal magnetic particles DP, based on the metal elements contained in the metal magnetic particles DP, Fe may be 46 wt% to 92 wt%, Ni may be 6 wt% to 50 wt%, and Al may be 2 wt% to 7 wt%. In other words, the metal elements constituting the metal magnetic particles DP are Fe, Ni, and Al, and when the total of these metal elements is 100 wt%, Fe may be 46 wt% to 92 wt%, Ni may be 6 wt% to 50 wt%, and Al may be 2 wt% to 7 wt%. Note that the metal magnetic particles DP may contain impurities of elements unavoidable in production. With such a content ratio, the content of at least the Ni element can be reduced compared to conventional methods, reducing production costs while improving magnetic properties as described in the examples below.

[0023] Furthermore, as a preferred embodiment of the Al aggregation region A1 of the metal magnetic particle DP, the Al aggregation region A1 may be localized within the metal magnetic particle DP. As used herein, "localized" refers to the presence of the Al aggregation region A1 in a limited location within the metal magnetic particle DP. Another way to specify the embodiment of the Al aggregation region A1 is that, when the metal magnetic particle DP is viewed in cross section as shown in FIG. 5, the cross-sectional area of ​​the Al aggregation region A1 may be 1% or more and 20% or less of the cross-sectional area of ​​the entire metal magnetic particle DP. Such an embodiment of the Al aggregation region A1 can improve the magnetic properties, as will be described in the examples below.

[0024] The surfaces of the metal magnetic particles DP are covered with an insulating coating (oxide coating OL). As used herein, "insulating" refers to a volume resistivity of 1 MΩcm or more. When the surfaces of the metal magnetic particles DP are covered with an insulating coating, the insulation between the metal magnetic particles DP can be improved. A specific example of the insulating coating is an oxide coating OL, as shown in FIG. 3. Adjacent metal magnetic particles DP are bonded via this oxide coating OL. Between the metal magnetic particles DP bonded by the oxide coating OL, a resin R is present in the gap between the oxide coating OL of the metal magnetic particles DP and the oxide coating OL of the metal magnetic particles DP. As described below, an epoxy resin is used as the resin R, but one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, alkyd resin, etc. may also be used.

[0025] The oxide film OL is a film produced by oxidizing the metal magnetic particles DP by subjecting the metal magnetic particles DP to a heat treatment. In other words, it may contain oxygen. Furthermore, as an example, the oxide film OL may contain an oxide derived from the Al contained in the metal magnetic particles DP. In other words, the oxide film OL is mainly composed of an oxide of Al, an oxide of Al and Fe, or a composite oxide of these (i.e., aluminum oxide or FeAl ２ O ４ The Al oxide coating may contain aluminum oxide and composite oxides thereof. By forming the Al oxide coating, high insulation reliability can be achieved.

[0026] The thickness of the oxide film OL may be preferably 5 nm to 100 nm, more preferably 5 nm to 50 nm, and even more preferably 5 nm to 20 nm. 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 three arbitrary central points on a cut surface cut perpendicular to the mounting surface and end surface of the element body through the center of the element body and the winding axis of the coil. The thickness of the oxide film OL is measured at three arbitrary central points in each field of view. The thickness of the oxide film OL may be calculated by averaging these nine points: (any three arbitrary central points on the cut surface) x (any three arbitrary central points in each field of view).

[0027] The oxide film OL may be produced by firing in a low-oxygen atmosphere or a reducing atmosphere, as will be described in detail in the manufacturing method of the composite metal magnetic body below. In this specification, a low-oxygen atmosphere refers to an atmosphere in which the oxygen concentration is 2 ppm or more and 200 ppm or less. A reducing atmosphere refers to an atmosphere that causes a reaction in which oxygen is removed from a substance. As will be described in the examples below, firing in an air atmosphere did not allow the Al aggregation region A1 shown in FIG. 5 to be formed in the metal magnetic particles DP. Furthermore, according to the coercive force measurement described in the examples below, the coercive force was beyond the measurement range and could not be measured.

[0028] Resin R may be used to increase the strength of the inductor element, which will be described later. As an example, resin R may be present between adjacent metal magnetic powder particles MP bonded by oxide coatings OL by heat-treating element body 10, which is formed by stacking magnetic layers G1 to G8 (see FIG. 2), which will be described later, and then impregnating element body 10 with resin. Examples of the resin impregnated after heat-treating element body 10 include epoxy resin and silicone resin. Other resins that may be used include one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, acrylic resin, polyvinyl butyral resin, cellulose resin, and alkyd resin.

[0029] <Description of Inductor of the Present Disclosure> Next, an inductor of the present disclosure will be described with reference to Figures 1 and 2. The inductor of the present disclosure includes an element body 10 including the composite metal magnetic body CP described above, and a coil provided within the element body 10.

[0030] The element body 10 has, for example, a rectangular parallelepiped or approximately rectangular parallelepiped shape having six sides. The corners and ridges of the element body 10 may be rounded. 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.

[0031] 1, the length direction, width direction, and height direction of the inductor 1 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 1 is, for example, a surface (LW surface) parallel to the length direction L and width direction W.

[0032] 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.

[0033] The element body 10 has a laminated structure in which a plurality of magnetic 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 element body 10 is constructed by laminating magnetic layers G1 to G8 as shown in FIG. 2. A coil is constructed by laminating a plurality of coil conductors CD. Constructing a coil by laminating coil conductors CD can contribute to miniaturization. Note that the boundaries between layers in the laminated structure of the element body 10 disappear. Furthermore, each of the magnetic layers G1 to G8 may be constructed by laminating a plurality of identical patterns.

[0034] 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 the magnetic layers G4 and G5, and the second coil is formed by the coil conductors CD of the magnetic layers G2 and G3. The coil conductors CD are mainly composed of Cu. The use of Cu can improve inductance characteristics. Note that, as an example of the material for the coil conductor CD, metal conductors such as Ag, Au, or alloys thereof may also be used instead of Cu. The inductor 1 of the first embodiment is not limited to this example, and for example, three or more coils may be 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 (the L direction in FIG. 1).

[0035] 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.

[0036] The through-hole conductors TH may be used to connect the coil 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.

[0037] According to the inductor of the present disclosure, by firing in a low-oxygen atmosphere or a reducing atmosphere, it is possible to provide an inductor having Al agglomerated regions A1 in which Al is agglomerated inside the metal magnetic particles DP, and in which peaks derived from the FeAl phase and peaks derived from the FeNi phase are present in X-ray diffraction. Therefore, the FeAl phase increases the lattice constant of the FeNi phase, thereby reducing the apparent magnetostriction of the composite metal magnetic body.

[0038] <Method for manufacturing a composite metal magnetic body and a method for manufacturing an inductor according to the present disclosure> Next, a method for manufacturing an inductor according to the present disclosure will be described. Note that the method for manufacturing a composite metal magnetic body is included in the method for manufacturing an inductor, so description thereof will be omitted.

[0039] 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.

[0040] - Preparation Step - A magnetic material (magnetic paste) for forming the magnetic layers ML of the magnetic layers G1 to G8 described with reference to FIG. 2 and a conductor paste for forming the coil conductor CD are prepared.

[0041] As an example of a method for producing a magnetic paste, a metal powder containing Fe with a cumulative 50% particle diameter (D50) of 2 μm to 20 μm by volume is prepared. Al powder (e.g., Al particles: 0.1 wt% to 10 wt%) is added to the metal powder, and 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, followed by kneading to produce a magnetic paste.

[0042] The conductive paste may be, for example, a paste containing Cu as a conductive material. Note that the conductive material is not limited to Cu, and a conductive material such as Ag, Au, or an alloy thereof may be formed into a paste.

[0043] The magnetic layers G1 to G8 shown in FIG. 2 are prepared and laminated by screen printing or the like using the magnetic paste and conductive paste described above.

[0044] - Pressurizing step (optional step) - After the magnetic layers G1 to G8 are stacked, the magnetic layers G1 to G8 are pressurized. This pressurization may be performed at a pressure of 300 MPa or more. By pressing the magnetic layers G1 to G8, two or more metal magnetic powders MP are bonded to form a composite metal magnetic body CP.

[0045] - Degreasing step (optional step) - A manufacturing process of a preferred inductor manufacturing method may include a degreasing step. The degreasing step is a step of removing binders contained in the magnetic paste and conductive paste. As an example, degreasing is performed at a temperature of about 300°C or higher and 500°C or lower. This removes the binders contained in the magnetic paste and conductive paste.

[0046] Heat Treatment Step Heat treatment is performed after the degreasing step. As an example of heat treatment conditions, nitrogen is injected into the furnace of the heat treatment device at a flow rate of 19 L / min, thereby creating a low-oxygen atmosphere inside the furnace. As another example of heat treatment conditions, nitrogen is injected into the furnace of the heat treatment device at a flow rate of 19 L / min and hydrogen is injected into the furnace of the heat treatment device at a flow rate of 0.19 L / min, thereby creating a reducing atmosphere inside the furnace. The heat treatment temperature is a temperature at which the coil conductor is sintered, and may be, for example, between 400°C and 1000°C. Furthermore, it is desirable to set the temperature to between 700°C and 900°C in order to simultaneously reduce the coercive force and suppress the thermal diffusion of the coil conductor material components into the base body. In particular, FeAl ２ O ４ When forming a highly corrosion-resistant composite oxide such as those mentioned above, the temperature is preferably set to 750° C. or higher and 900° C. This heat treatment forms an insulating coating mainly composed of an oxide of Al on the surface of the metal magnetic particles within the element, and adjacent metal magnetic particles can be bonded by the insulating coating.

[0047] Furthermore, to increase the strength of the element body, a resin may be impregnated into the gaps between the oxide films of adjacent metal magnetic particles within the element body and then cured. The resin impregnated into the element body is typically an epoxy resin, but one or more resins selected from the group consisting of phenolic resin, polyester resin, polyimide resin, polyolefin resin, silicone resin, acrylic resin, polyvinyl butyral resin, cellulose resin, and alkyd resin may also be used. The inductor element body of the present disclosure is formed through the above process.

[0048] External electrodes electrically connected to the coil conductors are then formed on the formed element body. The external electrodes are formed by electrolytic plating at the positions where the through-hole conductors are exposed on the mounting surface (first main surface 11) of the element body 10. The plating material may be Cu plating. Other examples include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu, and / or Cu-Ni-Au. After the external electrodes are formed, the inductor of this embodiment can be manufactured by cutting into individual elements.

[0049] As described above, the inductor manufacturing method described in this embodiment can manufacture an inductor having Al agglomerated regions A1 in which Al is agglomerated inside the metal magnetic particles DP, and in which peaks derived from the FeAl phase and peaks derived from the FeNi phase are present in X-ray diffraction. Therefore, the FeAl phase increases the lattice constant of the FeNi phase, and the apparent magnetostriction of the composite metal magnetic body can be reduced.

[0050] The following describes in detail the demonstration tests for the composite metal magnetic body of the present disclosure. Specifically, the inductors described in Examples 1 to 8 and Comparative Examples 1 to 4 below were manufactured.

[0051] -Explanation of the inductor of Example 1- (1) A magnetic paste was prepared by kneading a metal powder containing Fe (54 wt%), Ni (45 wt%), and Al (1 wt%) with a D50 of 5 μm, with ethyl cellulose as a binder and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then the magnetic layers were pressurized at approximately 300 MPa and degreased (pressurization process and degreasing process). (3) A heat treatment was performed at 750°C in a reducing atmosphere (nitrogen flow rate 19 L / min, hydrogen flow rate 0.19 L / min) in the furnace of the heat treatment device.

[0052] -Description of Inductors of Examples 2 to 4- In the inductor of Example 2, the Al content of the metal powder was 3 wt%. In the inductor of Example 3, the Al content of the metal powder was 5 wt%. In the inductor of Example 4, the Al content of the metal powder was 7 wt%. The Ni content was the same as in Example 1. In addition, in each of the above examples, the Fe content was reduced by the amount that the Al content increased. The other processes were the same as in Example 1.

[0053] -Explanation of the inductor of Example 5- (1) A magnetic paste was prepared by kneading a metal powder containing Fe (54 wt%), Ni (45 wt%), and Al (1 wt%) with a D50 of 5 μm, with ethyl cellulose as a binder and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then the magnetic layers were pressurized at approximately 300 MPa and degreased (pressurization process and degreasing process). (3) A heat treatment was performed at 700°C in a low-oxygen atmosphere (nitrogen flow rate 19 L / min) inside the furnace of the heat treatment device.

[0054] -Description of Inductors of Examples 6 to 8- In the inductor of Example 6, the Al content of the metal powder was 3 wt%. In the inductor of Example 7, the Al content of the metal powder was 5 wt%. In the inductor of Example 8, the Al content of the metal powder was 7 wt%. The Ni content was the same as in Example 5. In addition, in each of the above examples, the Fe content was reduced by the amount that the Al content increased. The other processes were the same as in Example 5.

[0055] - Explanation of the inductor of comparative example 1 - (1) A magnetic paste was prepared by kneading a metal powder containing Fe (54 wt%), Ni (45 wt%), and Al (1 wt%) with a D50 of 5 μm, with ethyl cellulose as a binder and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then the magnetic layers were pressurized at approximately 300 MPa and degreased (pressurization process and degreasing process). (3) A heat treatment was carried out at 700°C with the furnace of the heat treatment device in an air atmosphere.

[0056] - Explanation of inductors of comparative examples 2 to 4 - In the inductor of comparative example 2, the Al content of the metal powder was 3 wt%. In the inductor of comparative example 3, the Al content of the metal powder was 5 wt%. In the inductor of comparative example 4, the Al content of the metal powder was 7 wt%. The Ni content was the same as in comparative example 1. Furthermore, in each of the above comparative examples, the Fe content was reduced by the amount that the Al content increased. The other processes were the same as in comparative example 1.

[0057] - Inductor Evaluation 1 (Wavelength-Dispersive X-Ray Fluorescence Analysis) - Wavelength-dispersive X-ray fluorescence analysis was performed on the inductors of Examples 1 to 8 and Comparative Examples 1 to 4. The specific analysis procedure was as described above in <Description of the Composite Metal Magnetic Body of the Present Disclosure>. As an example of the analysis results, the analysis results for the inductor of Example 3 are shown in FIG. 5. Note that the results in FIG. 5 show, from left to right, <Al analysis results>, <Fe analysis results>, and <Ni analysis results>.

[0058] 5, it can be seen that Al agglomeration regions A1 with an Al concentration of about 150 LEVEL or more are localized, and that the Al concentration (about 150 LEVEL) in the Al agglomeration regions A1 is 1.5 times or more higher than the Al concentration (less than about 100 LEVEL) outside the Al agglomeration regions A2.

[0059] On the other hand, in the inductors of Comparative Examples 1 to 4, no Al agglomeration region A1 as shown in FIG. 5 could be confirmed.

[0060] -Inductor Evaluation 2 (X-ray Diffraction)- X-ray diffraction measurements were performed on the inductors of Examples 1 to 8 and Comparative Examples 1 to 4. The specific measurement procedures were as described above in <Description of the Composite Metal Magnetic Body of the Present Disclosure>. As an example of the measurement results, the measurement results for the inductors of Examples 4 and 8 and Comparative Example 4 are shown in Figure 6.

[0061] 6, peaks derived from the FeAl phase and peaks derived from the FeNi phase were confirmed in the inductors of Examples 1 to 12. On the other hand, peaks derived from the FeAl phase and peaks derived from the FeNi phase were not confirmed in the inductors of Comparative Examples 1 to 4.

[0062] - Inductor Evaluation 3 (Measurement of Magnetic Properties (Coercive Force Hc)) - The magnetic properties (coercive force Hc) of the inductors of Examples 1 to 8 and Comparative Examples 1 to 4 were measured. Specifically, an automatic coercive force meter (manufactured by Tohoku Special Steel Co., Ltd., model number: K-HC1000) was used to measure the coercive force Hc by applying a standard magnetic field for the device (1850 Oe (Oersted)). Note that the smaller the value of the coercive force Hc measured in this test, the smaller the area of ​​the DC hysteresis loop, the smaller the hysteresis loss, and the greater the magnetic permeability. Therefore, it is intended that a smaller Hc indicates better inductance characteristics.

[0063] The coercive force Hc of the inductors of Comparative Examples 1 to 4 exceeded the measurement range and was therefore unmeasurable. On the other hand, the coercive force Hc of the inductors of Examples 1 to 12 was lower than the coercive force Hc of the inductors of Comparative Examples 1 to 4 (see FIGS. 6 and 7).

[0064] Furthermore, the inductors fired in a reducing atmosphere (Examples 1 to 4) had lower coercive forces Hc than the inductors fired in a low-oxygen atmosphere (Examples 5 to 8).

[0065] Furthermore, taking into consideration the results of the above-mentioned "Inductor Evaluation 2 (X-ray Diffraction)," a graph (FIG. 8) was obtained in which the horizontal axis represents the peak top position of the FeNi peak (the peak top position around 74.73° in FIG. 6) and the vertical axis represents the coercive force Hc. The results showed that changing the Al content resulted in a peak shift in the FeNi peak. This peak shift indicates that changing the Al content of the metal magnetic particles increases the lattice constant of the FeNi phase. In other words, this means that the FeAl phase increases the lattice constant of the FeNi phase. As a result, the apparent magnetostriction can be reduced, and the magnetic properties of the composite metal magnetic material can be improved. In other words, the magnetic properties can be improved while reducing the Ni content in metal magnetic particles containing Fe, Ni, and Al.

[0066] The composite metal magnetic body and inductor, as well as the method for manufacturing a composite metal magnetic body and the method for manufacturing an inductor according to the present disclosure, are as follows: <1> A composite metal magnetic body comprising metal magnetic particles containing Fe, Ni, and Al, and an insulating coating covering the metal magnetic particles, wherein a plurality of the metal magnetic particles are bonded via the insulating coating, wherein the metal magnetic particles have Al agglomerated regions therein where Al is agglomerated, and wherein X-ray diffraction shows a peak derived from an FeAl phase and a peak derived from an FeNi phase. <2> The composite metal magnetic body according to <1>, wherein the insulating coating is mainly composed of an oxide containing an oxide of Al. <3> The oxide is FeAl ２ O ４<4> The composite metal magnetic body according to any one of <1> to <3>, wherein the metal magnetic particles have an average particle size of 1 μm or more and 6 μm or less. <5> The composite metal magnetic body according to any one of <1> to <4>, wherein the Al agglomeration regions are localized within the metal magnetic particles. <6> An inductor comprising the composite metal magnetic body according to any one of <1> to <5>. <7> A method for producing the composite metal magnetic body according to any one of <1> to <5>, comprising a heat treatment step of heating the metal magnetic particles at 400°C or more and 1000°C or less in a low-oxygen atmosphere or a reducing atmosphere to form an insulating coating mainly made of an oxide containing an oxide of Al on the surface of the metal magnetic particles. <8> The oxide is FeAl ２ O ４ <9> The method for manufacturing an inductor according to <6>, comprising a heat treatment step of heating the metal magnetic particles at 400°C or higher and 1000°C or lower in a low-oxygen atmosphere or a reducing atmosphere to form an insulating coating mainly made of an oxide containing an oxide of Al on the surface of the metal magnetic particles. <10> The oxide is FeAl ２ O ４ The method for manufacturing an inductor according to <9>,

[0067] The composite metal magnetic body and inductor, as well as the manufacturing method thereof, of the present disclosure can be suitably used as electronic components capable of improving magnetic properties.

[0068] REFERENCE SIGNS LIST 1 inductor 10 element 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 A1 Al aggregation region A2 outside of Al aggregation region C coil CD coil conductor CP composite metal magnetic body DP metal magnetic particle E external electrode E1 to E4 first external electrode to fourth external electrode G1 to G8 magnetic layer ML magnetic layer MP metal magnetic powder OL oxide film R resin TH through-hole conductor TH1 to TH4 first through-hole conductor to fourth through-hole conductor

Claims

1. A composite metal magnetic body comprising metal magnetic particles containing Fe, Ni, and Al, and an insulating coating covering the metal magnetic particles, wherein a plurality of the metal magnetic particles are bonded together via the insulating coating, wherein the metal magnetic particles have Al agglomeration regions within which Al is agglomerated, and wherein X-ray diffraction reveals peaks derived from the FeAl phase and peaks derived from the FeNi phase.

2. The composite metal magnetic body according to claim 1, wherein the insulating coating is mainly composed of an oxide containing an oxide of Al.

3. The oxide is FeAl ２ O ４ The composite metal magnetic body according to claim 2 , wherein 4. The composite metal magnetic body according to any one of claims 1 to 3, wherein the metal magnetic particles have an average particle size of 1 μm or more and 6 μm or less.

5. The composite metal magnetic body according to any one of claims 1 to 4, wherein the Al agglomerated regions are localized within the metal magnetic particles.

6. An inductor comprising the composite metal magnetic body according to any one of claims 1 to 5.

7. A method for producing a composite metal magnetic body according to any one of claims 1 to 5, comprising a heat treatment step of heating the metal magnetic particles at 400°C or higher and 1000°C or lower in a low-oxygen or reducing atmosphere to form an insulating coating mainly made of an oxide containing an oxide of Al on the surface of the metal magnetic particles.

8. The oxide is FeAl ２ O ４ The method for producing a composite metal magnetic body according to claim 7, wherein 9. A method for manufacturing an inductor according to claim 6, comprising a heat treatment step of heating the metal magnetic particles at 400°C or higher and 1000°C or lower in a low-oxygen or reducing atmosphere to form an insulating coating mainly made of an oxide containing an oxide of Al on the surface of the metal magnetic particles.

10. The oxide is FeAl ２ O ４ The method for manufacturing an inductor according to claim 9, wherein:

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