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

Abstract

Provided is a composite metal magnetic body, an inductor, a method for manufacturing the composite metal magnetic body, and a method for manufacturing the inductor, in which insulation characteristics are improved as compared with a case where chromium oxide is used as a passive film. A composite metal magnetic body CP according to the present disclosure comprises a plurality of metal magnetic powders MP each having metal magnetic particles DP including Fe and a passivation element that is more easily oxidized than Cr, and an oxide film OL covering the metal magnetic particles DP, the metal magnetic particles DP being bonded with the oxide film OL interposed therebetween. When an element amount in a region from the center portion of a metal magnetic particle DP to the outer surface of the oxide film OL is analyzed, the maximum percentage of the passivation element contained in the oxide film is 75 atm% or more on the basis of the entire metal element.

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 a coil component in which a spiral coil part covered with a magnetic material part is in direct contact with the magnetic material part, the magnetic material part being mainly composed of magnetic alloy grains and not containing a glass component, and an oxide film of the magnetic alloy grains is present on the surface of each magnetic alloy grain. ３ O ４ and Fe, which belongs to the non-magnetic material ２ O ３ and Cr ２ O ３ It is disclosed that the above at least includes the following.

[0003] JP 2012-164958 A

[0004] The coil component described in Patent Document 1 contains Cr, an element that is easily oxidized, in the magnetic material. As a result, a chromium oxide passive film is formed on the surface of the magnetic material when fired. In this specification, the term "passive film" refers to the state in which an oxide film that resists corrosion has formed on the metal surface. This oxide film does not dissolve even when exposed to solutions or acids, and therefore can be used to protect the internal metal from corrosion.

[0005] However, chromium oxide is an unstable passive film, meaning that depending on the condition of the oxide film, it may be reduced by the load during use of the inductor, resulting in a deterioration of the insulating properties.

[0006] The present disclosure aims to provide a composite metal magnetic body and an inductor having improved insulating properties compared to when chromium oxide is used as a passive film, as well as a method for manufacturing a composite metal magnetic body and a method for manufacturing an inductor.

[0007] The composite metal magnetic body of the present disclosure is a composite metal magnetic body in which a plurality of metal magnetic powders each having metal magnetic particles containing a passivation element and Fe that are more easily oxidized than Cr, and an oxide film covering the metal magnetic particles, are bonded together via the oxide film, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the maximum proportion of the passivation element based on the total metal elements contained in the oxide film is 75 atomic % or more.

[0008] The inductor of the present disclosure uses the above-described composite metal magnetic body.

[0009] The method for manufacturing a composite metal magnetic body disclosed herein includes a heat treatment step in which metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr are heat treated in a low-oxygen atmosphere or a reducing atmosphere to form an oxide film on the surface of the metal magnetic particle, wherein the heat treatment step bonds adjacent metal magnetic particles together via the oxide film within the composite metal magnetic body, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum proportion of the passivation element of 75 atomic % or more based on the total metal elements contained in the oxide film.

[0010] The method for manufacturing an inductor disclosed herein includes a heat treatment process in which metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr are heat treated in a low-oxygen or reducing atmosphere to form an oxide film on the surface of the metal magnetic particles, wherein the heat treatment process bonds multiple adjacent metal magnetic particles together via the oxide film within the element, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum proportion of the passivation element of 75 atomic % or more based on the total metal elements contained in the oxide film.

[0011] According to the present disclosure, it is possible to provide a composite metal magnetic body and an inductor having improved insulating properties compared to when chromium oxide is used as a passivation coating, as well as a method for manufacturing a composite metal magnetic body and a method for manufacturing an inductor.

[0012] FIG. 1 is a perspective view of an inductor of the present disclosure. FIG. 2 is an exploded perspective view of the inductor of the present disclosure. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2 . FIG. 4A is a cross-sectional view of a composite metal magnetic body of the present disclosure. FIG. 4B is a cross-sectional view of another embodiment of a composite metal magnetic body of the present disclosure. FIG. 5A is a cross-sectional view of a composite metal magnetic body of the present disclosure heat-treated in a low-oxygen atmosphere. FIG. 5B is a cross-sectional view of a composite metal magnetic body of the present disclosure heat-treated in a reducing atmosphere. FIG. 6A is a graph showing the results of a composition analysis of the composite metal magnetic body shown in FIG. 5A. FIG. 6B is a graph showing the results of a composition analysis of the composite metal magnetic body shown in FIG. 5B. FIG. 6C is a graph showing another result of a composition analysis of the composite metal magnetic body shown in FIG. 5B. FIG. 6D is a graph showing another result of a composition analysis of the composite metal magnetic body shown in FIG. 5B. FIG. 6E is a graph showing another result of a composition analysis of the composite metal magnetic body shown in FIG. 5B. FIG. 7 is a table showing the results of measuring powder resistivity.

[0013] 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.

[0014] <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" referred to in this specification refers to a configuration in which metal magnetic powders MP formed by coating metal magnetic particles DP with an oxide film OL are bonded together via the oxide film OL, as shown in Fig. 4A, and may also have at least a portion in which the metal magnetic powders MP are bonded together via a resin R without an oxide film as shown in Fig. 4B. In other words, the "composite metal magnetic body" refers to a configuration in which multiple (two or more) metal magnetic powders MP are directly bonded or indirectly bonded to a portion.

[0015] The metal magnetic powder MP includes metal magnetic particles DP and an oxide film OL. Depending on the method for forming the oxide film OL, the oxide film OL may contain a resin component.

[0016] The average particle size of the metal magnetic particles DP may be preferably 0.2 μm or more and 20 μm or less, more preferably 0.5 μm or more and 15 μm or less, and even more preferably 1 μm or more and 6 μm or less.

[0017] 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).

[0018] The metal magnetic particles DP contain at least Fe (iron) element. The metal magnetic particles DP may also contain Ni element. More specifically, they may contain an element that is less susceptible to oxidation than the passivation element described below. Furthermore, the metal magnetic particles DP contain a passivation element that is more easily oxidized than Cr. In this specification, the "passivation element that is more easily oxidized than Cr" may be an index determined with reference to the Ellingham diagram.

[0019] As an example of a preferred passivation element, the passivation element may include at least one element selected from the group consisting of Al, Zr, and Ti. Among the passivation elements, Al is the element that is most easily oxidized, followed by Zr and Ti in order of least oxidization. In the following description, the passivation element will be described as Al.

[0020] 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 the heat treatment, or may remain.

[0021] 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.

[0022] The oxide film OL is a film generated by the oxidation of the metal magnetic particles DP. In other words, it may contain oxygen. Furthermore, it may contain a passivating element and may contain an oxide derived from the passivating element. For example, when Al is used as the passivating element, the oxide film OL may contain aluminum oxide. 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 locations on a cross section 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. In each field of view, the thickness of the oxide film OL is measured at three arbitrary central locations. The thickness of the oxide film OL may be determined by averaging these nine points (any three points in the center of the cut surface) x (any three points in the center of each field of view).

[0023] The state of the oxide film OL will be described in detail in the manufacturing method of the composite metal magnetic body described later, but the state of the oxide film OL may differ between when fired in a low-oxygen atmosphere and when fired in a reducing atmosphere.

[0024] When firing is performed in a low-oxygen atmosphere in the manufacturing method of the composite metal magnetic body, the oxide film OL may have a two-layer structure (a structure including a first oxide film OL1 and a second oxide film OL2 outside the first oxide film OL1) as shown in Figure 5A. In this case, the first oxide film OL1 may be an oxide derived from the metal magnetic particles, and the second oxide film OL2 may be an oxide derived from a passivating element. Details of the analysis will be described in the Examples below.

[0025] Furthermore, when firing is performed in a reducing atmosphere in the manufacturing method of the composite metal magnetic body, the oxide film OL may have a single-layer structure, as shown in FIG. 5B . More specifically, the outermost surface of the oxide film OL may have the highest proportion of passivating elements among the metal elements constituting the oxide film OL. By firing in a reducing atmosphere in this manner, the insulation resistance of the oxide film OL can be further increased, as will be described in detail in the [Examples]. Note that the term "metal element" as used herein refers to an element that constitutes a metal as a simple substance, and may include semimetallic elements such as Si, B, Ge, As, Sb, and Te.

[0026] The resin may be used to increase the strength of the inductor element, which will be described later. As an example, the element 10, which is formed by stacking magnetic layers G1 to G8 (see FIG. 2), which will be described later, may be heat-treated and then impregnated with resin, so that the resin is present between adjacent metal magnetic powder particles MP bonded by insulating coatings. Examples of the resin impregnated into the element 10 after heat treatment 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, alkyd resin, and the like.

[0027] In the composite metal magnetic body CP of the present disclosure, when the elemental amounts in the region from the center of the metal magnetic particle DP to the outer surface of the oxide film OL are analyzed, the maximum proportion of passivating elements relative to the total metal elements contained in the oxide film OL is 75 atm% or more. The "maximum proportion of passivating elements relative to the total metal elements contained in the oxide film" in this specification can be measured 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. This cross section is then photographed using a TEM (approximately 800,000 times magnification) at the coil winding axis portion so that the metal magnetic powder MP is within the field of view, thereby identifying the location of the metal magnetic powder MP. At the identified location, quantitative analysis of the metal elements is performed using EDX. In quantitative analysis using EDX, composition analysis is performed by line analysis across the outer edge of the metal magnetic particle DP (line analysis is performed along the arrows in Figures 5A and 5B), and the maximum proportion of passivating elements relative to the total metal elements contained in the oxide film in the obtained composition analysis graph is measured. Note that in the composition analysis, the maximum proportion may be the average of the maximum proportions of passivating elements at (any three locations in the center of the cut surface) x (any three locations in the center of each field of view) = 9 locations.

[0028] Although the details of the analysis will be described later in the [Example], when the composite metal magnetic body sintered in the low-oxygen atmosphere as shown in Fig. 5A was subjected to line analysis, the results shown in Fig. 6A were obtained, and the maximum ratio of the passivating elements to the total metal elements contained in the oxide film OL was 79.88 atm%. The volume resistivity of this composite metal magnetic body was 2.7 × 10 as shown in Fig. 7. ８ 6A, the arrow indicates the outermost surface of the oxide film OL, and the proportion of the passivating elements is the highest in the arrow portion.

[0029] In a preferred embodiment of the composite metal magnetic material CP, when the elemental amounts in the region from the metal magnetic particles DP to the oxide film OL are analyzed, the maximum proportion of passivating elements relative to the total metal elements contained in the oxide film OL may be 90 atm% or more. Details of the analysis will be described in detail in the Examples below. When a composite metal magnetic material sintered in a reducing atmosphere as shown in FIG. 5B was subjected to line analysis, the results shown in FIG. 6B were obtained, and the maximum proportion of passivating elements relative to the total metal elements contained in the oxide film OL was 95.64 atm%. The volume resistivity of this composite metal magnetic material was 8.9 × 10, as shown in FIG. 7. ８ This tendency also applies to the case where the passivation element is Zr (see FIG. 6D) and Ti (see FIG. 6E), and the volume resistivity is 5.0×10 Ω·cm, as shown in FIG. ９ Ω・cm, 1.0×10 ８ 6B to 6E, the arrowed portions correspond to the outermost surface of the oxide film OL, and the proportion of the passivating elements is the highest in the arrowed portions.

[0030] <Description of Inductor of the Present Disclosure> Next, the inductor of the present disclosure will be described with reference to Figures 1 to 4. The inductor of the present disclosure includes an element body 10 including the composite metal magnetic body CP described above, and a coil provided within the element body 10.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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).

[0036] 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.

[0037] 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.

[0038] According to the inductor of the present disclosure, the base body 10 is constructed using a composite metal magnetic body sintered in a low-oxygen atmosphere as shown in FIG. 5A or a composite metal magnetic body sintered in a reducing atmosphere as shown in FIG. 5B, thereby achieving good insulation properties.

[0039] <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.

[0040] 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.

[0041] - 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.

[0042] As an example of a method for producing a magnetic paste, a metal magnetic powder containing Fe with a cumulative 50% particle diameter (D50) of 2 μm to 20 μm by volume is prepared. A passivating element (e.g., Al: 0.1 wt% to 10 wt%) that is more easily oxidized than Cr is added to this metal magnetic 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 and kneaded to produce a magnetic paste.

[0043] 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.

[0044] 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.

[0045] - 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.

[0046] - 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.

[0047] Heat Treatment Step After the degreasing step, a heat treatment is performed. For example, as shown in FIG. 5A, when a composite metal magnetic material CP having a two-layer oxide film OL is produced, nitrogen is injected into the furnace of the heat treatment device at a flow rate of 19 L / min to create a low-oxygen atmosphere in the furnace. For example, as shown in FIG. 5B, when a composite metal magnetic material CP having a single-layer oxide film OL is produced, 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 at a flow rate of 0.19 L / min to create a reducing atmosphere in the furnace. The heat treatment temperature is a temperature at which the coil conductor sinters, and may be, for example, between 400°C and 1000°C. Furthermore, a temperature between 700°C and 900°C is preferable to achieve both a reduction in coercive force and a suppression of 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. or lower. This heat treatment forms an oxide film on the surface of the metal magnetic particles within the element, and adjacent metal magnetic particles can be bonded by the oxide film.

[0048] Furthermore, to increase the strength of the element body, the gaps between the oxide films of adjacent metal magnetic particles may be impregnated with a resin 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.

[0049] 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.

[0050] As described above, according to the inductor manufacturing method described in this embodiment, it is possible to manufacture an inductor having a base body 10 formed using a composite metal magnetic body sintered in a low-oxygen atmosphere as shown in FIG. 5A or a composite metal magnetic body sintered in a reducing atmosphere as shown in FIG. 5B, thereby obtaining good insulation properties.

[0051] The following describes in detail the demonstration tests for the composite metal magnetic body of the present disclosure. Specifically, the inductors described in the following examples and comparative examples were manufactured.

[0052] -Description of the inductor of Example 1- (1) A magnetic paste was prepared by kneading a metal powder containing Fe, Ni, and Al (passivating elements) with a D50 of 5 μm, adding ethyl cellulose as a binder, and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). The magnetic paste was prepared as described above using Fe40Ni5Al (40% Ni, 5% Al, and the remainder Fe) as the metal magnetic particles. (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then 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) in the furnace of the heat treatment device.

[0053] -Description of the inductor of Example 2- (1) A magnetic paste was prepared by kneading a metal powder containing Fe, Ni, and Al (passivating elements) with a D50 of 5 μm, adding ethyl cellulose as a binder, and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). The magnetic paste was prepared as described above using Fe40Ni5Al (40% Ni, 5% Al, and the remainder Fe) as the metal magnetic particles. (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then 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.

[0054] -Description of the inductor of Example 3- (1) A magnetic paste was prepared by kneading a metal powder containing Fe and Al (passivating elements) with a D50 of 5 μm, adding ethyl cellulose as a binder, and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). The magnetic paste was prepared as described above using Fe5Al (5% Al overall, the remainder Fe) as the metal magnetic particles. (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then 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.

[0055] -Description of the inductor of Example 4- (1) A magnetic paste was prepared by kneading a metal powder containing Fe, Ni, and Zr (passivating elements) with a D50 of 5 μm, adding ethyl cellulose as a binder, and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). The magnetic paste was prepared as described above using Fe40Ni5Zr (40% Ni, 5% Zr, and the remainder Fe) as the metal magnetic particles. (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then 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 a heat treatment device.

[0056] -Description of the inductor of Example 5- (1) A magnetic paste was prepared by kneading a metal powder containing Fe, Ni, and Ti (passivating elements) with a D50 of 5 μm, adding ethyl cellulose as a binder, and a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent (preparation process). The magnetic paste was prepared as described above using Fe40Ni5Ti (40% Ni, 5% Ti, and the remainder Fe) as the metal magnetic particles. (2) As shown in Figure 2, the magnetic layers G1 to G8 were stacked, and then 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 a heat treatment device.

[0057] - Explanation of Inductor of Comparative Example 1 - The inductor of Comparative Example 1 is the same as that of Example 1 except that a metal powder containing Fe, Si, and Cr was used as the metal powder in Example 1.

[0058] - Explanation of Inductor of Comparative Example 2 - The inductor of Comparative Example 2 is the same as that of Example 2 except that a metal powder containing Fe, Si, and Cr was used as the metal powder in Example 2.

[0059] - Evaluation of inductors (part 1) - A "composition analysis by line analysis" was performed on the manufactured inductors. Specifically, composition analysis was performed using EDX (Noran, System 7) along the arrows in Figures 5A and 5B, straddling the outer edge of the metal magnetic particles DP. As described above, the composition analysis was performed at nine locations: (any three locations in the center of the cut surface) x (any three locations in the center of each field of view).

[0060] The graph shown in Figure 6A corresponds to the measurement results of the inductor of Example 1, with the horizontal axis representing the measurement position in the line analysis and the vertical axis representing the content. Here, region A1 in Figure 6A, where the oxygen content is lower than the Fe content or Ni content (the content of metal magnetic particles), corresponds to metal magnetic particles DP in Figure 5A. Region B1 in Figure 6A, where the Al content (the content of passivating elements) is higher than the Fe content or Ni content (the content of metal magnetic particles), corresponds to first oxide film OL1 in Figure 5A. Region C1 in Figure 6A, where the Fe content is higher than the Al content (the content of passivating elements), corresponds to second oxide film OL2 in Figure 5A. In other words, the graph shown in Figure 6A reveals that the oxide film has a two-layer structure consisting of first oxide film OL1, which is an oxide film rich in metal magnetic particles, and second oxide film OL2, which is an oxide film rich in passivating elements.

[0061] 6A, the Al content (content of passivating elements) peaks in region B1. Calculating the ratio of the Al content (Al content / total metal elements) at the peak position yields a result of 79.88 atm %.

[0062] The graph shown in Figure 6B corresponds to the measurement results of the inductor of Example 2, with the horizontal axis representing the measurement position in the line analysis and the vertical axis representing the content. Here, region A2 in Figure 6B, where the oxygen content is lower than the Fe content or Ni content (content of the metal magnetic particles), corresponds to the metal magnetic particles DP in Figure 5B. Region B2 in Figure 6B, where the Al content (content of the passivation element) is higher than the Fe content or Ni content (content of the metal magnetic particles), corresponds to the oxide film OL in Figure 5B. In other words, the graph shown in Figure 6B reveals that the oxide film has a single-layer structure.

[0063] 6B, the Al content (content of passivating elements) peaks in region B2. Calculating the ratio of the Al content (Al content / total metal elements) at this peak position yields a result of 95.64 atm %.

[0064] 6C to 6E respectively correspond to the measurement results of the inductors of Examples 3 to 5. As described above, the inductors of Examples 3 to 5 were fired in a reducing atmosphere, and therefore, it can be seen that the oxide film has a single-layer structure, similar to the graph shown in Fig. 6B.

[0065] - Evaluation of Inductors (Part 2) - Volume resistivity measurements were performed on the manufactured inductors of Examples 1 to 5 and Comparative Examples 1 and 2. Specifically, a digital ultra-high resistance measuring device (manufactured by ADC Corporation, model number: 54541) was used to apply a voltage of 5 V to the inductor element body 10, and the volume resistivity was calculated from the measurement results of the electrical resistance value and the volume of the portion to which the voltage was applied.

[0066] The measurement results of powder resistance are shown in Figure 7. According to the measurement results, Examples 1 to 5 had higher powder resistance values ​​than Comparative Examples 1 and 2, and therefore better insulation properties. Furthermore, when comparing Example 1 and Example 2, in which the metal magnetic particles were Fe40Ni5Al, the composite metal magnetic body of Example 2, in which the oxide film had a single-layer structure, had a higher volume resistivity value than the composite metal magnetic body of Example 1, in which the oxide film had a two-layer structure. These results indicated that it is more preferable for the outermost surface of the oxide film OL to be a composite metal magnetic body in which the proportion of passivating elements among the elements constituting the oxide film OL is the highest.

[0067] Furthermore, when Example 2 in which the metal magnetic particles were Fe40Ni5Al was compared with Example 3 in which the metal magnetic particles were Fe5Al, almost the same insulating properties were obtained.

[0068] Furthermore, when Example 2, in which the metal magnetic particles are Fe40Ni5Al, Example 4, in which the metal magnetic particles are Fe40Ni5Zr, and Example 5, in which the metal magnetic particles are Fe40Ni5Ti, were compared, the volume resistivity was higher in the order of Example 4 > Example 2 > Example 5. In other words, the best insulating properties were obtained when Zr was used as the passivation element. Considering the reason for this result, it is thought that although Example 4 uses a different passivation element from Example 2, a thick oxide film was formed by heat treatment in a reducing atmosphere, resulting in a high volume resistivity. Furthermore, in Example 5, the oxide film was Al ２ O ３ and ZrO ２ TiO, which has a lower volume resistivity than ２ This is thought to be the reason why the volume resistivity was low.

[0069] It should be noted that the embodiments disclosed herein are illustrative in all respects and are not intended to be limiting. Therefore, the technical scope of the present disclosure should not be interpreted solely by the above-described embodiments, but should be defined based on the claims. The technical scope of the present disclosure also includes all modifications within the scope and meaning equivalent to the claims.

[0070] The present disclosure provides a composite metal magnetic body, an inductor, and a method for manufacturing a composite metal magnetic body and an inductor, each of which includes the following aspects: <1> A composite metal magnetic body comprising a plurality of metal magnetic powders bonded together via an oxide film, the metal magnetic powder comprising metal magnetic particles containing Fe and a passivating element that is more easily oxidized than Cr, and an oxide film covering the metal magnetic particles, wherein, when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the maximum proportion of the passivating element relative to the total metal elements contained in the oxide film is 75 atm% or more. <2> The composite metal magnetic body according to <1>, wherein the metal magnetic particles contain at least Fe and Al, or Fe, Ni, and Al. <3> The composite metal magnetic body according to <1> or <2>, wherein the passivating element comprises at least one element selected from the group consisting of Al, Zr, and Ti. <4> The composite metal magnetic body according to any one of <1> to <3>, wherein, when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the maximum proportion of the passivating element based on the total amount of metal elements contained in the oxide film is 90 atm% or more. <5> The composite metal magnetic body according to any one of <1> to <4>, wherein the proportion of the passivating element is the highest among the metal elements contained in the oxide film at the outermost surface of the oxide film. <6> The composite metal magnetic body according to any one of <1> to <5>, wherein the oxide film is mainly composed of an oxide containing an oxide of Al. <7> The oxide is FeAl ２ O ４<6> The composite metal magnetic body according to <8>, wherein the oxide film has a thickness of 5 nm or more and 100 nm or less. <9> The composite metal magnetic body according to any one of <1> to <8>, wherein the particle size of the metal magnetic particles is 1 μm or more and 6 μm or less. <10> The composite metal magnetic body according to any one of <1> to <9>, wherein an epoxy resin or a silicone resin is present between the metal magnetic particles bonded via the oxide film. <11> An inductor using the composite metal magnetic body according to any one of <1> to <10>. <12> An inductor comprising a magnetic layer formed from the composite metal magnetic body according to any one of <1> to <11> and a coil conductor stacked together, the coil conductor containing Cu as a main component. <12> A method for manufacturing a composite metal magnetic body, comprising a heat treatment step of heat treating metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr in a low-oxygen atmosphere or a reducing atmosphere to form an oxide film on the surface of the metal magnetic particle, wherein the heat treatment step bonds multiple adjacent metal magnetic particles together via the oxide film within the composite metal magnetic body, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum proportion of the passivation element of 75 atomic % or more based on the total metal elements contained in the oxide film. <13> A method for manufacturing an inductor, comprising a heat treatment step of heat treating metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr in a low-oxygen atmosphere or a reducing atmosphere to form an oxide film on the surface of the metal magnetic particles, wherein the heat treatment step bonds multiple adjacent metal magnetic particles together via the oxide film within an element, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum proportion of the passivation element of 75 atomic % or more based on the total metal elements contained in the oxide film.

[0071] 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 having improved insulating properties compared to those using chromium oxide as a passivation coating.

[0072] 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 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 body layer ML magnetic layer MP metal magnetic powder OL oxide film OL1 to OL2 first oxide film to second 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 in which multiple metal magnetic powders are bonded together via an oxide film, the metal magnetic powder having metal magnetic particles containing a passivating element and Fe that are more easily oxidized than Cr, and an oxide film covering the metal magnetic particles, wherein, when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the maximum proportion of the passivating element based on the total metal elements contained in the oxide film is 75 atm% or more.

2. The composite metal magnetic body according to claim 1, wherein the metal magnetic particles contain at least Fe and Al, or Fe, Ni and Al.

3. The composite metal magnetic body according to claim 1 or 2, wherein said passivating element comprises at least one element selected from the group consisting of Al, Zr and Ti.

4. A composite metal magnetic body described in any one of claims 1 to 3, wherein, when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the maximum proportion of the passivating element based on the total metal elements contained in the oxide film is 90 atomic % or more.

5. A composite metal magnetic body according to any one of claims 1 to 4, wherein the outermost surface of the oxide film has the highest proportion of the passivating element among the metal elements contained in the oxide film.

6. A composite metal magnetic body according to any one of claims 1 to 5, wherein the oxide film is mainly composed of an oxide containing an oxide of Al.

7. The oxide is FeAl ２ O ４ The composite metal magnetic body according to claim 6, wherein 8. A composite metal magnetic body according to any one of claims 1 to 7, wherein the thickness of the oxide film is 5 nm or more and 100 nm or less.

9. A composite metal magnetic body according to any one of claims 1 to 8, wherein the particle size of the metal magnetic particles is 1 μm or more and 6 μm or less.

10. A composite metal magnetic body according to any one of claims 1 to 9, wherein an epoxy resin or a silicone resin is present between the metal magnetic particles bonded via the oxide film.

11. An inductor using the composite metal magnetic material according to any one of claims 1 to 10.

12. An inductor comprising a magnetic layer formed from the composite metal magnetic material according to any one of claims 1 to 10 and a coil conductor stacked together, the coil conductor being primarily composed of Cu.

13. A method for manufacturing a composite metal magnetic body, comprising a heat treatment step in which metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr are heat treated in a low-oxygen or reducing atmosphere to form an oxide film on the surface of the metal magnetic particle, wherein the heat treatment step bonds multiple adjacent metal magnetic particles together via the oxide film within the composite metal magnetic body, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum ratio of the passivation element to the total metal elements contained in the oxide film of 75 atm% or more.

14. A method for manufacturing an inductor, comprising a heat treatment step of heat treating metal magnetic particles containing Fe and a passivation element that is more easily oxidized than Cr in a low-oxygen atmosphere or a reducing atmosphere to form an oxide film on the surface of the metal magnetic particles, wherein the heat treatment step bonds multiple adjacent metal magnetic particles together via the oxide film within the element, and when the amount of elements in the region from the center of the metal magnetic particle to the outer surface of the oxide film is analyzed, the oxide film has a maximum proportion of the passivation element of 75 atm% or more based on the total metal elements contained in the oxide film.

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