Composite metal magnetic body, inductor, and method of producing composite metal magnetic body

Abstract

Provided are a composite metal magnetic body, an inductor, and a method of producing a composite metal magnetic body that further reduce degradation of an oxide film covering metallic magnetic particles. A composite metal magnetic body CP1, CP2 of the present disclosure comprises metallic magnetic particles DP and an oxide film OL covering the metallic magnetic particles DP, a plurality of metallic magnetic particles DP being bonded together via the oxide film OL, wherein the oxide film OL comprises an inside oxide film OLi that is in contact with the metallic magnetic particles DP and composed mainly of Si, and an outside oxide film OLo that is located on the outside of the inside oxide film OLi and contains either Al or Ti, and Zr.

Description

Composite metal magnetic material, inductor, and method for manufacturing a composite metal magnetic material

[0001] This disclosure relates to a composite metal magnetic material, an inductor, and a method for manufacturing a composite metal magnetic material.

[0002] Patent Document 1 discloses a coil component of the type in which a spiral coil portion covered by a magnetic material portion is in direct contact with the magnetic material portion, wherein the magnetic material portion mainly consists of a group of magnetic alloy particles and does not contain a glass component, and an oxide film of magnetic alloy particles exists on the surface of each magnetic alloy particle (see Claim 1 of Patent Document 1). Furthermore, the oxide film contains Fe, which belongs to the magnetic material. ３ O ４ And Fe, which belongs to the non-magnetic material ２ O ３ and Cr ２ O ３ The document discloses at least the following (see paragraph

[0018] of Patent Document 1).

[0003] Japanese Patent Publication No. 2012-164958

[0004] The oxide film described in Patent Document 1 was susceptible to degradation of its insulating properties due to reduction of the oxide film under load during inductor use. Therefore, the present disclosure aims to provide a composite metal magnetic material, an inductor, and a method for manufacturing the composite metal magnetic material that further reduces the degradation of the oxide film coating the metal magnetic particles.

[0005] The composite metallic magnetic material of the present disclosure comprises metallic magnetic particles and an oxide film coating the metallic magnetic particles, wherein a plurality of the metallic magnetic particles are bonded together via the oxide film, and the oxide film comprises an inner oxide film mainly composed of Si in contact with the metallic magnetic particles and an outer oxide film located outside the inner oxide film and containing Al or Ti and Zr.

[0006] The inductor of this disclosure comprises the composite metal magnetic material described above.

[0007] The present disclosure provides a method for producing a composite metal magnetic material, comprising: a surface treatment step of surface-treating metal magnetic particles with a coupling agent containing Al or Ti; a metal magnetic precursor formation step of adding a metal organic compound containing Zr to the surface-treated metal magnetic particles to form a metal magnetic precursor; a pressurization step of pressurizing the metal magnetic precursor; and a heat treatment step of heat-treating the metal magnetic precursor to form an oxide film on the surface of the metal magnetic particles and bonding a plurality of the metal magnetic particles via the oxide film.

[0008] The composite metallic magnetic material of this disclosure can further reduce the deterioration of the insulating properties of the oxide film coating the metallic magnetic particles. Specifically, the composite metallic magnetic material of this disclosure has an outer oxide film containing Al or Ti and Zr on the outside of an inner oxide film mainly composed of Si that is in contact with the metallic magnetic particles. Therefore, the reduction reaction that removes oxygen can be reduced by the Al or Ti oxide and the Zr oxide, which are chemically more stable than Fe oxide, and thus the deterioration of insulating properties can be reduced.

[0009] Figure 1 is a perspective view of the inductor of this disclosure. Figure 2 is an exploded perspective view of the inductor of this disclosure. Figure 3 is a dashed cross-sectional view taken in the direction of the arrow III-III in Figure 2. Figure 4 is a graph showing the compositional analysis results of the composite metal magnetic material of the first embodiment. Figure 5 is a graph showing the compositional analysis results of a modified example of the composite metal magnetic material of the first embodiment. Figure 6 is a graph showing the compositional analysis results of the composite metal magnetic material of the second embodiment. Figure 7 is a graph showing the compositional analysis results of a modified example of the composite metal magnetic material of the second embodiment. Figure 8 is a flowchart showing the manufacturing flow of the method for manufacturing the composite metal magnetic material of this disclosure. Figure 9 is a table showing the results of the verification test related to the composite metal magnetic material.

[0010] The composite metal magnetic material and inductor, as well as the method for manufacturing the composite metal magnetic material, will be described in detail below. While the drawings will be referenced as necessary, the illustrations are provided for illustrative purposes only to aid in understanding this disclosure, and their appearance and dimensional ratios may differ from those of the actual product.

[0011] <Description of the Composite Metal Magnetic Material of the First Embodiment> First, the composite metal magnetic material CP1 of the first embodiment will be described. In this specification, "composite metal magnetic material" refers to a configuration in which metal magnetic powders MP, composed of metal magnetic particles DP coated with an oxide film OL, are bonded together via the oxide film OL, as shown in Figure 3. However, it is not limited to the configuration shown in Figure 3, and for example, at least a portion may have metal magnetic powders MP bonded together via a resin R without an oxide film. In other words, "multiple bonding" in this specification refers to a configuration in which multiple (two or more) metal magnetic powders MP are directly bonded or partially indirectly bonded.

[0012] The metal magnetic powder MP comprises metal magnetic particles DP and an oxide film OL. As shown in Figure 3, a resin R may be present in the gaps between the oxide films OL of the metal magnetic particles DP, which are bonded together by the oxide film OL. As will be described later, epoxy resin is used for 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, and alkyd resin may be used. Furthermore, the oxide film OL may contain a resin component depending on the method of forming the oxide film OL.

[0013] The average particle size of the metallic magnetic particles DP is 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.

[0014] The average particle size of the metallic magnetic particles DP can be measured by the procedure described below. A sample of the inductor is cut to obtain a sample cross-section. Specifically, the sample cross-section is obtained by cutting the main body 10 (see Figure 1) through the center and the winding axis of the coil, perpendicular to the mounting surface and end face of the main body. The sample cross-section may be made flat by ion milling or the like. For the obtained cross-section, three arbitrary locations in the center of the cut surface corresponding to the central part of the main body 10 are photographed with an SEM (magnification of approximately 2000 to 3000 times). Then, in each field of view, the obtained SEM images are analyzed at three arbitrary locations in the center using image analysis software (for example, image analysis software WinROOF2021 (manufactured by Mitani Corporation)) to identify the metallic magnetic particles DP and determine the equivalent circle diameter of the metallic magnetic particles. The average value of the obtained equivalent circle diameters is taken as the average particle size of the metallic magnetic particles. In this specification, the average particle size may mean the average particle size D50 (particle size equivalent to 50% of the cumulative percentage by volume).

[0015] The metallic magnetic particles DP may be an Fe-Si alloy. The metallic magnetic particles DP may be contained in the magnetic paste. The resin components contained in the magnetic paste may be removed by heat treatment or may remain.

[0016] The oxide film OL covers the surface of the metal magnetic particles DP, providing insulation between them. When the surface of the metal magnetic particles DP is covered with the oxide film OL, the insulation between the metal magnetic particles DP can be increased.

[0017] The oxide film OL is a film produced by the oxidation of the metallic magnetic particles DP. In other words, it may contain oxygen and elements contained in the surface treatment agent used for surface treatment of the metallic magnetic particles DP (Ti, Al), as well as elements that are more easily oxidized than Fe added during the production of the magnetic paste (e.g., Zr, Ti, Al, Cr, Mg, Mn, Zn) and oxides of these elements. The total thickness of the oxide film OL is 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 taking a scan electron microscope (SEM) or transmission electron microscope (TEM) image of a cross-section obtained by polishing an inductor sample, and measuring the thickness of the oxide film OL covering the surface of the metallic magnetic particles DP from the obtained SEM image. The thickness of the oxide film OL is measured by taking images of three arbitrary locations in the center of a cross-section cut perpendicular to the mounting surface and end face of the base body 10, passing through the center of the base body 10 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 average of these nine points ((three arbitrary points in the center of the cross section) × (three arbitrary points in the center of each field of view)) can be used as the thickness of the oxide film OL.

[0018] The oxide film OL comprises at least an inner oxide film OLi and an outer oxide film OLo. Furthermore, an intervening portion OLm may be provided in a part of the inner oxide film OLi or the outer oxide film OLo. The boundary between the inner oxide film OLi, the outer oxide film OLo, and the intervening portion OLm is determined by the compositional analysis results of the metal magnetic powder MP. Specifically, a cross-section obtained by polishing an inductor sample is photographed with a transmission electron microscope (TEM) (at a magnification of approximately 800,000 times), and the composition is determined from the results of quantitative compositional analysis performed on the cross-section by line analysis along the arrows in the illustrated example (Figure 3, etc.). The compositional analysis results of the composite metal magnetic material CP1 of the first embodiment are shown in Figure 4 or Figure 5.

[0019] The inner oxide film OLi is in contact with the metallic magnetic particles DP and is mainly composed of Si. In this specification, "main component" refers to the component that is most abundant among the metallic elements and Si in the inner oxide film OLi. The inner oxide film OLi in this embodiment is SiO ２This may be the intended meaning. More preferably, SiO2 with a higher O content than Si content. ２ This may be intended. Furthermore, the inner oxide film OLi may contain metal elements resulting from oxides described later (e.g., Zr), and elements that constitute the outer oxide film OLo.

[0020] The boundary between the inner oxide film OLi and the metallic magnetic particles DP may be intended to be the position P1 in the compositional analysis graph (see Figure 4 or Figure 5) where the Si content is greater than the Fe content. Similarly, the boundary between the inner oxide film OLi and the outer oxide film OLo may be intended to be the position P2 in the compositional analysis graph (see Figure 4) where the Fe content is greater than the Si content.

[0021] The outer oxide film OLo is located outside the inner oxide film OLi and contains Ti or Al and Zr. In this embodiment, the outer oxide film OLo is described as an oxide film containing Al and Zr (see Figure 4). In addition to Al and Zr, the outer oxide film OLo may also contain Si and Fe. Here, Al and Zr are elements that are more easily oxidized than Fe. In this specification, the indicator of ease of oxidation may be determined with reference to the Ellingham diagram.

[0022] The outer edge of the outer oxide film OLo may be defined as position P4 in the compositional analysis graph (see Figure 4), where the Zr content no longer corresponds to the main component, or it may be determined from SEM or TEM images.

[0023] Thus, when the outer oxide film OLo contains Al and Zr, which are more easily oxidized than Fe, Al and Zr are oxidized preferentially over Fe, making it difficult for Fe oxides to form. As a result, the formation of Fe oxides, which are unstable as oxides, is reduced, and the insulating properties can be improved by the Al and Zr oxides, which are more chemically stable than Fe oxides. In addition, the Al and Zr oxides, which are more chemically stable than Fe oxides, can reduce the reduction reaction that removes oxygen from the oxide film, thereby reducing the deterioration of insulating properties.

[0024] As a further preferred aspect of the present embodiment, as shown in FIG. 4, the peak PZr of the Zr content may be present in the outer oxide film OLo. By thus causing an oxide of Zr, which is more chemically stable than the oxide of Fe, to exist on the outermost side of the oxide film OL, deterioration of insulation due to a reduction reaction can be further reduced.

[0025] Also, in the present embodiment, an intervening portion OLm may be provided in a part of the outer oxide film OLo. One boundary position P2 of the intervening portion OLm may be the boundary position between the inner oxide film OLi and the outer oxide film OLo, and the other boundary position P3 may be the position where the Zr content becomes larger than the Fe content. Because of such boundary positions, the intervening portion OLm may have a peak PAl of the Al content as shown in FIG. 4. When the intervening portion OLm has a peak PAl of the Al content, an oxide of Al is more likely to be formed by Al, which is more easily oxidized than Fe. Therefore, generation of an oxide of Fe, which is an unstable oxide, can be made less likely to occur. Since the Al content is an extremely small amount compared to other metal elements, it may not have a peak PAl of the Al content as shown in FIG. 4 and may contain Al gently. In this case, the Al content can be measured by elemental analysis using EDS (energy dispersive X-ray spectroscopy). Also, even when Al is contained slightly, the presence of Al can be confirmed by mapping in compositional analysis. Also, in the intervening portion OLm of the present embodiment, the peak PAl of the Al content and the peak PZr of the Zr content in the intervening portion OLm may overlap. That is, the outer oxide film OLo and the intervening portion OLm may overlap.

[0026] The intervening portion OLm preferably contains an oxide of Al and ZrSiO ４ For such an oxide, since the oxide of Al and ZrSiO ４ are chemically stable oxides, a reduction reaction in which oxygen is removed from the oxide film can be further reduced, and deterioration of insulation can be further reduced.

[0027] Furthermore, as will be detailed in the manufacturing method of the composite metal magnetic material described later, the Al contained in the intervening portion OLm is a material derived from a coupling agent, and the Zr contained in the outer oxide film OLo may be a material derived from a metal-organic compound. Generally, since metal-organic compounds (for example, resinates containing Zr) are hydrophobic, there was room to further improve the affinity with hydrophilic metal magnetic particles DP and to further improve the insulating properties of the composite metal magnetic material after the pressurizing process in which multiple metal magnetic powders MP are bonded together. Therefore, by forming an outer oxide film OLo derived from a metal-organic compound on the surface of the metal magnetic particles DP via an intervening portion OLm derived from a coupling agent, the affinity with the metal-organic compound can be further improved, and the insulating properties of the composite metal magnetic material can be further improved.

[0028] Furthermore, in the composite metal magnetic material CP1 of the first embodiment, as shown in Figure 3, when multiple bonded positions via the outer oxide film OLo are designated as bonded positions BP, and a desired position between each bonded position BP in the outer oxide film OLo is designated as the interbonded position IP, the Zr content in the interbonded position IP may be greater than the Zr content in the bonded positions BP. In this specification, "bonded position BP" refers to the region between two opposing metal magnetic powders MP, as shown in Figure 3, where a line segment L1 is drawn connecting the centroids of adjacent metal magnetic powders MP, and virtual lines L2 are drawn on both sides of the virtual line L1 with the centroids of the metal magnetic powders MP at ±10°, with the virtual line L2 as the reference. In addition, in this specification, "interbonded position IP" refers to the position between the contacting parts when multiple metal magnetic powders MP are in contact with one metal magnetic powder MP. The Zr content can also be adjusted by the heat treatment process in the manufacturing method of the composite metal magnetic material described later. With such a Zr content, the Zr content of the outermost surface film is higher in the interbonding position IP that is in contact with the external environment, and the Fe content is relatively lower, thus reducing the influence of the reduction reaction of Fe oxides.

[0029] In the first embodiment described above, the outer oxide film OLo contained Al, but similar effects can be obtained even if the outer oxide film OLo contains Ti instead of Al. Also, when the outer oxide film OLo contains Ti, the intervening portion is TiO ２ And, ZrSiO ４ It may contain TiO. ２ and ZrSiO ４ Because it is a stable oxide, the reduction reaction that removes oxygen from the oxide film can be further reduced, thereby reducing the deterioration of insulation properties.

[0030] The following explanation will describe the compositional analysis graph of a composite metallic magnetic material in which the outer oxide film OLo contains Ti instead of Al, with reference to Figure 5. Points common to the "compositional analysis graph of a composite metallic magnetic material in which the outer oxide film OLo contains Al," as explained using Figure 4, will be omitted as appropriate.

[0031] Although the inner oxide film OLi differs in that it contains Ti instead of Al, the trends in the Fe, Si, and Zr content shown in the graph in Figure 4 and the Fe, Si, and Zr content shown in the graph in Figure 5 are almost identical.

[0032] The outer oxide film OLo is located outside the inner oxide film OLi and contains Ti and Zr. In addition to Ti and Zr, the outer oxide film OLo may also contain Si and Fe. The outer edge of the outer oxide film OLo may be defined as position P4 in the compositional analysis graph (see Figure 5) where the Zr content no longer corresponds to the main component, or the outer edge of the outer oxide film OLo may be determined from SEM or TEM images.

[0033] When the outer oxide film OLo contains Ti and Zr which are more easily oxidized than Fe, Ti and Zr are more easily oxidized than Fe, and the formation of Fe oxide is less likely to occur. As a result, the formation of unstable Fe oxide as an oxide is reduced, and the insulation can be improved by the oxides of Ti and Zr which are more chemically stable than the oxide of Fe. Further, the reduction reaction in which oxygen is removed from the oxide film can be reduced by the oxides of Ti and Zr which are more chemically stable than the oxide of Fe, and the deterioration of insulation can be reduced.

[0034] As shown in FIG. 5, the intervening portion OLM may have a peak PTi in the Ti content. When the intervening portion OLM has a peak PTi in the Ti content, Ti oxide is more likely to be formed by Ti which is more easily oxidized than Fe. Therefore, the formation of unstable Fe oxide can be made less likely to occur. Since the Ti content is an extremely small amount compared to other metal elements, it may not have a peak PTi in the Ti content as shown in FIG. 5, and Ti may be contained gently. In this case, the Ti content can be measured by elemental analysis by EDS (energy dispersive X-ray spectroscopy). Also, even when Ti is contained slightly, the presence of Ti can be confirmed by mapping in the composition analysis. Further, in the intervening portion OLM of the present embodiment, the peak PTi in the Ti content and the peak PZr in the Zr content in the intervening portion OLM may overlap. That is, the outer oxide film OLo and the intervening portion OLM may overlap.

[0035] The intervening portion OLM preferably contains an oxide of Ti and ZrSiO ４ . For such an oxide, since the oxides of Ti and ZrSiO ４ are chemically stable oxides compared to the oxide of Fe, the reduction reaction in which oxygen is removed from the oxide film can be further reduced, and the deterioration of insulation can be further reduced.

[0036] Furthermore, as will be detailed in the manufacturing method of the composite metal magnetic material described later, the Ti contained in the intervening portion OLm is a material derived from a coupling agent, and the Zr contained in the outer oxide film OLo may be a material derived from a metal-organic compound. Generally, since metal-organic compounds (for example, resinates containing Zr) are hydrophobic, there was room to further improve the affinity with hydrophilic metal magnetic particles DP and to further improve the insulating properties of the composite metal magnetic material after the pressurization process in which multiple metal magnetic powders MP are bonded together. Therefore, by forming an outer oxide film OLo derived from a metal-organic compound on the surface of the metal magnetic particles DP via an intervening portion OLm derived from a coupling agent, the affinity with the metal-organic compound can be further improved, and the insulating properties of the composite metal magnetic material can be further improved.

[0037] <Description of the Composite Metal Magnetic Material of the Second Embodiment> Next, the composite metal magnetic material CP2 of the second embodiment will be described with reference to Figure 6. In describing the composite metal magnetic material CP2 of the second embodiment, explanations of points that are common with the configuration of the composite metal magnetic material CP1 of the first embodiment will be omitted as appropriate. In other words, the following description will focus on the configurations that differ from the composite metal magnetic material CP1 of the first embodiment.

[0038] As shown in Fig. 6, the composite metal magnetic material CP2 of the second embodiment may have an intervening portion OLm in a part of the inner oxide film OLi. One boundary position P3 of the intervening portion OLm may be a position where the content of Al is more than the content of Fe, and the other boundary position P2 may be the boundary position between the inner oxide film OLi and the outer oxide film OLo. Because of such boundary positions, the intervening portion OLm may have a peak PAl of the content of Al as shown in Fig. 6. When the intervening portion OLm has a peak PAl of the content of Al, it becomes easier to generate an oxide of Al by Al which is more easily oxidized than Fe. Therefore, it is possible to make it more difficult to generate an oxide of Fe which is an unstable oxide. Since the content of Al is an extremely small amount compared with other metal elements, it may not have a peak PAl of the content of Al as shown in Fig. 6 and Al may be contained gently. In this case, the content of Al can be measured by elemental analysis using EDS (Energy Dispersive X-ray Spectroscopy). Also, even when Al is contained slightly, the presence of Al can be confirmed by mapping in the composition analysis.

[0039] As shown in Fig. 6, the thickness T1 of the inner oxide film OLi of the composite metal magnetic material CP2 of the second embodiment may be thicker than the thickness T2 of the outer oxide film OLo. By setting such a thickness relationship, the insulation property is further improved, it becomes more difficult to generate an oxide of Fe, and the deterioration of the insulation property due to the reduction reaction can be further reduced.

[0040] In the present embodiment, although the mode having the intervening portion OLm in a part of the inner oxide film OLi has been described, it is not limited to this mode, and a mode in which the outer oxide film OLo and the intervening portion OLm overlap may be used.

[0041] In the second embodiment described above, although the mode in which the oxide film OL contains Al has been described, the same operational effects can be obtained even when the oxide film OL contains Ti instead of Al. Hereinafter, a graph of the composition analysis of the composite metal magnetic material in which the oxide film OL contains Ti instead of Al will be described with reference to Fig. 7. The points common to the "graph of the composition analysis of the composite metal magnetic material in which the oxide film OL contains Al" described using Fig. 6 will be omitted as appropriate.

[0042] In the compositional analysis graph of the composite metallic magnetic material shown in Figure 7, the intervening portion OLm may have a peak PTi indicating the Ti content. Having a Ti content peak PTi in the intervening portion OLm makes it easier for Ti oxides to be formed due to Ti being more easily oxidized than Fe. Therefore, the formation of Fe oxides, which are unstable oxides, can be made less likely. However, since the Ti content is extremely small compared to other metallic elements, the Ti content may not have a peak PTi as shown in Figure 7, but rather be distributed more smoothly. In this case, the Ti content can be measured by elemental analysis using EDS (energy-dispersive X-ray spectroscopy). Furthermore, even when only a small amount of Ti is present, its presence can be confirmed by mapping in the compositional analysis.

[0043] <Description of the Inductor of the Disclosure> Next, the inductor of the Disclosure will be described with reference to Figures 1 and 2. The inductor of the Disclosure comprises a base body 10 having the composite metal magnetic material described above, and a coil provided within the base body 10.

[0044] The base body 10 is, for example, a rectangular prism shape or a roughly rectangular prism shape having six faces. The corners and edges of the base body 10 may be rounded. The corners are the parts where three faces of the base body 10 intersect, and the edges are the parts where two faces of the base body 10 intersect.

[0045] Figure 1 shows the length, width, and height directions of the inductor 1 and the base body 10 as the L, W, and T directions, respectively. The length L, width W, and height T are orthogonal to each other. The mounting surface of the inductor 1 is, for example, a surface parallel to the length L and width W (LW surface).

[0046] The base body 10 shown in Figure 1 has a first main surface 11 and a second main surface 12 facing the height direction T, a first end surface 13 and a second end surface 14 perpendicular to the height direction T and facing the length direction L, and a first side surface 15 and a second side surface 16 perpendicular to the width direction W, which is perpendicular to both the length direction L and the height direction T. In the example shown in Figure 1, 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.

[0047] The base body 10 has a laminated structure in which multiple magnetic layers, each having a magnetic layer ML and a coil conductor CD, are stacked in the stacking direction (for example, the height direction T). In this embodiment, the base body 10 is constructed by stacking magnetic layers G1 to G8 as shown in Figure 2. A coil is formed by stacking multiple coil conductors CD and connecting the coil conductors CD between the magnetic layers ML. Constructing a coil by stacking coil conductors CD contributes to miniaturization. Note that the boundaries between each layer of the laminated structure of the base body 10 have disappeared.

[0048] The base body 10 contains a coil formed by stacking multiple coil conductors CD. In the example shown in Figure 2, two coils (a first coil and a second coil) are provided within the base body 10 along the stacking direction. More specifically, the first coil is formed by the coil conductors CD of magnetic layers G4 and G5, and the second coil is formed by the coil conductors CD of magnetic layers G2 and G3. The coil conductors CD mainly consist of Ag. Using Ag can improve the inductance characteristics. As an example of the material for the coil conductors CD, metal conductors such as Cu, Au, or their alloys may be used instead of Ag. Furthermore, the inductor 1 of the first embodiment is not limited to this example, and for example, the base body 10 may contain only one coil. Alternatively, multiple coils may be arranged side by side inside the base body 10 in a direction intersecting the stacking direction (direction L in Figure 1) to form a coil array.

[0049] External electrodes E are provided on the mounting surface (first main surface 11) of the base body 10. In the example shown in Figure 2, the external electrodes E include a first external electrode E1 and a second external electrode E2 connected to each end of the first coil, and a third external electrode E3 and a fourth external electrode E4 connected to each end of the second coil. Note that two external electrodes are provided for each coil.

[0050] A through-hole conductor TH may be used to connect the coil to the external electrode E. That is, the first through-hole conductor TH1 to the fourth through-hole conductor TH4 may be provided corresponding to the first external electrode E1 to the fourth external electrode E4. Furthermore, the first through-hole conductor TH1 to the fourth through-hole conductor TH4 may extend along the lamination direction.

[0051] According to the inductor of this disclosure, since it comprises the composite metal magnetic material CP1 or composite metal magnetic material CP2 described above, the reduction reaction that removes oxygen from the oxide film can be reduced by Al and Zr oxides, which are chemically more stable than Fe oxides, thereby improving insulation properties.

[0052] <Description of the manufacturing method of the composite metal magnetic material of the first embodiment> Next, the manufacturing method of the composite metal magnetic material of the present disclosure will be described. However, since the composite metal magnetic material of the present disclosure is intended to be used in an inductor, the description will be mainly given as a method for manufacturing an inductor. First, the manufacturing method of the composite metal magnetic material of the first embodiment shown in Figure 4 or Figure 5 will be described with reference to Figure 8.

[0053] The method for manufacturing an inductor comprising a composite metal magnetic material according to the first embodiment may include a preparation step, a surface treatment step, a metal magnetic precursor formation step, a pressurization step, a degreasing step, and a heat treatment step (see Figure 8). The details of each step will be described below.

[0054] -Preparation Process- Prepare the magnetic material (magnetic paste) that constitutes the magnetic layer ML of the magnetic layers G1 to G8 as explained in Figure 2, and the conductive paste that constitutes the coil conductor CD.

[0055] As an example of a magnetic paste material, a metallic magnetic powder containing Fe and Si with a D50 (cumulative 50% particle size by volume) of 2 μm to 20 μm is prepared.

[0056] As a conductive paste, for example, a paste containing Ag as a conductive material is prepared. However, the conductive material is not limited to Ag; a paste made from conductive materials such as Cu, Au, or their alloys may also be used.

[0057] -Surface Treatment Process- The metal magnetic powder used to create the magnetic paste is subjected to a surface treatment with a coupling agent. Specifically, this surface treatment is performed so as to cover the surface of the metal magnetic powder with the coupling agent. It is not necessary for the entire surface of the metal magnetic powder to be covered with the coupling agent; it is sufficient if only a part of the surface of the metal magnetic powder is covered with the coupling agent. Alternatively, this surface treatment may be performed by adding the coupling agent to the magnetic paste before the Zr resinate described later, thereby adhering the coupling agent to the surface of the metal magnetic powder. The coupling agent used in the surface treatment process contains 0.5% by weight of Al or Ti relative to the metal magnetic particles, based on the total coupling agent. This surface treatment process produces a metal magnetic powder containing Al or Ti derived from the coupling agent.

[0058] -Metal Magnetic Precursor Formation Process- A magnetic paste is prepared by adding 0.5% by weight of a metal-organic compound (for example, Zr resinate) whose main component is an element that is more easily oxidized than Fe to a metal magnetic powder that has been surface-treated with a coupling agent containing Al or Ti, and then kneading the mixture.

[0059] Then, using the magnetic paste and conductive paste described above, the magnetic layers G1 to G8 shown in Figure 2 are prepared and stacked by screen printing or the like, thereby forming a metallic magnetic precursor.

[0060] -Pressurization Process- After laminating the magnetic layers G1 to G8, the magnetic layers G1 to G8 are subjected to pressurization. This pressurization may be performed at a pressure of 300 MPa or higher. Pressurizing the magnetic layers G1 to G8 improves the packing density of the metal magnetic powder MP within the laminate of magnetic layers G1 to G8. Furthermore, this pressurization pushes the metal-organic compound, which is the material of the outer oxide film of the metal magnetic particles, from the bonding positions of multiple adjacent metal magnetic particles to the interbonding positions.

[0061] - Degreasing Process - A degreasing process may be included as a preferred manufacturing process. The degreasing process is a process of removing binders contained in magnetic paste and conductive paste. As an example, degreasing is performed in an air atmosphere at a temperature of approximately 300°C to 500°C. This removes the binders contained in magnetic paste and conductive paste.

[0062] - Heat Treatment Process - Heat treatment is performed after the degreasing process. The furnace of the heat treatment apparatus is kept in an air atmosphere. The heat treatment temperature is such that the coil conductor is sintered, for example, it may be between 400°C and 1000°C. Furthermore, to achieve both a reduction in coercivity and suppression of heat diffusion of the coil conductor material components into the base body, it is desirable to set the temperature between 600°C and 800°C. Through this heat treatment, adjacent metal magnetic powders MP are bonded together by an oxide film OL. Furthermore, a base body 10 is produced which comprises a composite metal magnetic material CP1 having an inner oxide film OLi mainly composed of Si in contact with the metal magnetic particles DP, and an outer oxide film OLo located outside the inner oxide film OLi and containing Al or Ti and Zr.

[0063] Furthermore, according to the heat treatment process of this embodiment, a composite metal magnetic material CP1 can be obtained in which an intervening portion having a peak in the Ti or Al content is formed in a part of the inner oxide film, as shown in Figure 4 or Figure 5.

[0064] Furthermore, in order to increase the strength of the base material, resin may be impregnated into the gaps between the oxide films of adjacent metal magnetic particles within the base material and cured. The resin used to impregnate the base material is 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. By going through the above steps, the base material of the inductor of this disclosure is formed.

[0065] Subsequently, external electrodes electrically connected to the coil conductor are formed on the formed body. The external electrodes are formed by electroplating at the positions where the through-hole conductor is exposed on the mounting surface (first main surface 11) of the body 10. The plating material may be Cu plating. Other materials include, but are not limited to, Ni-Sn, Ni-Au, Ni-Cu and / or Cu-Ni-Au. After the external electrodes are formed, the element can be cut into individual pieces to manufacture the inductor of this embodiment.

[0066] As described above, the method for manufacturing a composite metallic magnetic material of this embodiment makes it possible to produce a composite metallic magnetic material having an inner oxide film mainly composed of Si in contact with metallic magnetic particles, and an outer oxide film containing Al or Ti and Zr on the outside. Furthermore, because the reduction reaction that removes oxygen can be reduced by the Al or Ti oxide and the Zr oxide, which are more stable than Fe oxide, the deterioration of insulating properties can be reduced.

[0067] <Description of the Method for Manufacturing a Composite Metal Magnetic Material in the Second Embodiment> Next, the method for manufacturing a composite metal magnetic material in the second embodiment shown in Figure 6 or Figure 7 will be described. The method for manufacturing a composite metal magnetic material in the second embodiment differs from the method for manufacturing a composite metal magnetic material in the first embodiment in the conditions of the degreasing process and the heat treatment process. Therefore, explanations of points common to the method for manufacturing a composite metal magnetic material in the first embodiment will be omitted as appropriate, and the following description will focus on the heat treatment process that differs from the method for manufacturing a composite metal magnetic material in the first embodiment.

[0068] - Degreasing process - A suitable degreasing process is to carry out degreasing in a low-oxygen atmosphere. More specifically, degreasing may be carried out in an oxygen atmosphere of 2 ppm to 200 ppm. This removes the binder contained in the magnetic paste and conductive paste.

[0069] -Heat Treatment Process- The heat treatment process may be carried out in a nitrogen atmosphere of 97% to 99%. Hydrogen may be supplied in the atmosphere at a concentration of 1% to 3%. The amount of hydrogen injected in the heat treatment process is limited to the upper limit of industrially safe usage (3%). The heat treatment temperature is such that the coil conductor is sintered, for example, it may be around 400°C to 1000°C. Furthermore, it is desirable to set the temperature to 600°C to 800°C in order to achieve both a reduction in coercivity and suppression of thermal diffusion of the coil conductor material components into the base body. This heat treatment produces a base body 10 comprising a composite metallic magnetic material CP1, which has an inner oxide film mainly composed of Si in contact with the metallic magnetic particles, and an outer oxide film located outside the inner oxide film that contains Al or Ti and Zr.

[0070] Furthermore, according to the heat treatment process of this embodiment, a composite metal magnetic material CP2 can be obtained in which an intervening portion having a peak in the Ti or Al content is formed in a part of the outer oxide film, as shown in Figure 6 or Figure 7.

[0071] The demonstration tests concerning the composite metallic magnetic materials of this disclosure are described in detail. Specifically, the composite metallic magnetic materials described in the following examples and comparative examples were manufactured.

[0072] -Composite Metal Magnetic Material of Example 1- A composite metal magnetic material was manufactured according to the manufacturing method of the first embodiment, through a preparation step, a surface treatment step, a metal magnetic precursor formation step, a pressurization step, a degreasing step, and a heat treatment step. In the surface treatment step, the composite metal magnetic material of Example 1 was surface-treated with a coupling agent containing Al. In the degreasing step, degreasing was performed in an air atmosphere according to the manufacturing method of the first embodiment, and in the heat treatment step, heat treatment was performed in an air atmosphere according to the manufacturing method of the first embodiment.

[0073] -Composite Metal Magnetic Material of Example 2- A composite metal magnetic material was manufactured according to the manufacturing method of the first embodiment, through a preparation step, a surface treatment step, a metal magnetic precursor formation step, a pressurization step, a degreasing step, and a heat treatment step. In the composite metal magnetic material of Example 2, the surface treatment step was performed with a coupling agent containing Ti. In the degreasing step, degreasing was performed in an air atmosphere according to the manufacturing method of the first embodiment, and in the heat treatment step, heat treatment was performed in an air atmosphere according to the manufacturing method of the first embodiment.

[0074] -Comparative example of a composite metal magnetic material- The comparative example of a composite metal magnetic material does not undergo a surface treatment step in the manufacturing method of the first embodiment. Furthermore, in the metal magnetic precursor formation step, a metal-organic compound mainly composed of an element that is more easily oxidized than Fe (for example, Zr resinate) is not added. Except as described above, the composite metal magnetic material was manufactured in accordance with the manufacturing method of the first embodiment. In the degreasing step, degreasing was performed in an air atmosphere in accordance with the manufacturing method of the first embodiment, and in the heat treatment step, heat treatment was performed in an air atmosphere in accordance with the manufacturing method of the first embodiment.

[0075] - Evaluation of Insulation Resistance of Composite Metal Magnetic Materials - The insulation resistance of the composite metal magnetic materials of the manufactured examples and the composite metal magnetic materials of the comparative examples was evaluated.

[0076] To evaluate the insulation resistance, a composite magnetic substrate with a diameter of 8 mm and a thickness of 1 mm was fabricated using a composite metallic magnetic material. Conductive electrodes were formed on the top and bottom surfaces of the composite magnetic substrate, and the insulation resistance was measured using an insulation resistance meter (Advantest Corporation, model number: R8340).

[0077] The insulation resistance evaluation is shown in Figure 9. According to the insulation resistance evaluation, when the insulation resistance of the comparative example composite metal magnetic material was measured and compared before and after thermal loading, a decrease in the insulation resistance value occurred after thermal loading, confirming deterioration of insulation due to the reduction reaction. On the other hand, when the insulation resistance of the composite metal magnetic materials of Example 1 and Example 2 was measured and compared before and after thermal loading, the decrease in insulation resistance was reduced compared to the comparative example, confirming that good insulation characteristics were obtained. From this insulation resistance evaluation, it can be concluded that the composite metal magnetic material of this disclosure can further reduce the deterioration of the oxide film coating the metal magnetic particles.

[0078] Furthermore, comparing Example 1 and Example 2, it is generally known that Al is more easily oxidized than Ti. Therefore, comparing the composite metal magnetic material of Example 1 with the composite metal magnetic material of Example 2, the composite metal magnetic material of Example 1, which was surface-treated with a coupling agent containing Al, showed better insulating properties.

[0079] The embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Therefore, the technical scope of this disclosure is not construed solely by the embodiments described above, but is defined based on the claims. Furthermore, the technical scope of this disclosure includes all modifications within the meaning and scope of equivalence to the claims.

[0080] The embodiments of the composite metal magnetic material, inductor, and method for manufacturing the composite metal magnetic material of the present disclosure are as follows: <1> A composite metal magnetic material having metallic magnetic particles and an oxide film covering the metallic magnetic particles, wherein a plurality of metallic magnetic particles are bonded together via the oxide film, wherein the oxide film comprises: an inner oxide film mainly composed of Si in contact with the metallic magnetic particles, and an outer oxide film located outside the inner oxide film and containing Al or Ti and Zr. <2> The composite metal magnetic material according to <1>, wherein the inner oxide film or a part of the outer oxide film has an intervening portion having a peak in the content of Al or Ti. <3> The composite metal magnetic material according to <1> or <2>, wherein the peak in the content of Zr is in the outer oxide film. <4> The composite metal magnetic material according to any one of <1> to <3>, wherein the thickness of the inner oxide film is greater than the thickness of the outer oxide film. <5> The intervening portion is composed of an oxide of Al and ZrSiO ４ A composite metallic magnetic material according to <2>, or any one of <3> or <4> that references <2>. <6> The intervening portion is TiO ２ And, ZrSiO ４A composite metallic magnetic material according to any one of <2>, or <3> or <4>, which references <2>, containing <2>. <7> A composite metallic magnetic material according to any one of <1> to <6>, wherein when the positions on which multiple bonds are made to each other via the outer oxide film are defined as bond positions, and the positions between each bond position in the outer oxide film are defined as interbond positions, the Zr content at the bond positions is greater than the Zr content at the interbond positions. <8> A composite metallic magnetic material according to any one of <1> to <7>, wherein the metallic magnetic particles are an alloy containing Fe and Si. <9> A composite metallic magnetic material according to any one of <2> or <3> to <8>, which references <2>, wherein the Al or Ti contained in the intervening portion is a material derived from a coupling agent, and the Zr contained in the outer oxide film is a material derived from a metal-organic compound. <10> An inductor comprising the composite metallic magnetic material according to any one of <1> to <9>. <11> A method for producing a composite metal magnetic material, comprising: a surface treatment step of surface-treating metal magnetic particles with a coupling agent containing Al or Ti; a metal magnetic precursor formation step of adding a metal organic compound containing Zr to the surface-treated metal magnetic particles to form a metal magnetic precursor; a pressurization step of pressurizing the metal magnetic precursor; and a heat treatment step of heat-treating the metal magnetic precursor to form an oxide film on the surface of the metal magnetic particles and bonding a plurality of the metal magnetic particles via the oxide film. <12> The method for producing a composite metal magnetic material according to <11>, wherein the heat treatment step forms an inner oxide film mainly composed of Si in contact with the metal magnetic particles, and an outer oxide film located outside the inner oxide film and containing Al or Ti and Zr. <13> The method for producing a composite metal magnetic material according to <12>, wherein the heat treatment step further forms an intervening portion having a peak in the Ti or Al content in the inner oxide film or a part of the outer oxide film. <14> The method for producing a composite metal magnetic material according to any one of <11> to <13>, wherein the heat treatment step is carried out in a nitrogen atmosphere of 97% to 99%. <15> The method for producing a composite metal magnetic material according to <14>, wherein the heat treatment step is carried out by supplying hydrogen in the atmosphere to a concentration of 1% to 3%.<16> A method for producing a composite metal magnetic material according to any one of <11> to <15>, wherein degreasing is performed in an oxygen atmosphere of 2 ppm to 200 ppm before the heat treatment step.

[0081] The composite metal magnetic material, inductor, and method for manufacturing the composite metal magnetic material described herein can be suitably used as electronic components that further reduce the degradation of the oxide film coating the metal magnetic particles.

[0082] 1 Inductor 10 Base 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 CD Coil conductor CP1-CP3 Composite metal magnetic material DP Metal magnetic particles E External electrodes E1-E4 First external electrode to fourth external electrode G1-G8 Magnetic layer ML Magnetic layer MP Metal magnetic powder OL Oxide film OLi Inner oxide film OLm Interposed oxide film OLo Outer oxide film R Resin TH Through-hole conductor TH1-TH4 First through-hole conductor to fourth through-hole conductor M1, M2 Peak position P1-P4 Position BP Coupling position IP Inter-coupling position P1-P4 Boundary position T1 Thickness of inner oxide film T2 Thickness of outer oxide film PAl Peak value of Al content Peak value of PZr Zr content

Claims

1. A composite metallic magnetic material having metallic magnetic particles and an oxide film coating the metallic magnetic particles, wherein a plurality of the metallic magnetic particles are bonded together via the oxide film, the oxide film comprising: an inner oxide film mainly composed of Si in contact with the metallic magnetic particles; and an outer oxide film located outside the inner oxide film and containing Al or Ti and Zr.

2. The composite metallic magnetic material according to claim 1, wherein the inner oxide film or a part of the outer oxide film has an intervening portion having a peak in the content of Al or Ti.

3. The composite metallic magnetic material according to claim 1 or 2, wherein the peak of the Zr content is present in the outer oxide film.

4. The composite metallic magnetic material according to any one of claims 1 to 3, wherein the thickness of the inner oxide film is greater than the thickness of the outer oxide film.

5. The intervening portion consists of Al oxide and ZrSiO ４ A composite metallic magnetic material according to claim 2, or any one of claims 3 or 4 that references claim 2.

6. The intervening portion is TiO ２ And, ZrSiO ４ A composite metallic magnetic material according to claim 2, or any one of claims 3 or 4 that references claim 2.

7. The composite metallic magnetic material according to any one of claims 1 to 6, wherein when the positions where multiple elements are bonded to each other via the outer oxide film are defined as bond positions, and the spaces between each bond position in the outer oxide film are defined as interbond positions, the Zr content at the interbond positions is greater than the Zr content at the bond positions.

8. The composite metallic magnetic material according to any one of claims 1 to 7, wherein the metallic magnetic particles are an alloy containing Fe and Si.

9. The composite metallic magnetic material according to claim 2 or any one of claims 3 to 8 that references claim 2, wherein the Al or Ti contained in the intervening portion is a material derived from a coupling agent, and the Zr contained in the outer oxide film is a material derived from a metal-organic compound.

10. An inductor comprising a composite metallic magnetic material according to any one of claims 1 to 9.

11. A method for producing a composite metal magnetic material, comprising: a surface treatment step of surface-treating metal magnetic particles with a coupling agent containing Al or Ti; a metal magnetic precursor formation step of adding a metal organic compound containing Zr to the surface-treated metal magnetic particles to form a metal magnetic precursor; a pressurization step of pressurizing the metal magnetic precursor; and a heat treatment step of heat-treating the metal magnetic precursor to form an oxide film on the surface of the metal magnetic particles and bonding a plurality of the metal magnetic particles via the oxide film.

12. The method for producing a composite metal magnetic material according to claim 11, wherein the heat treatment step forms an inner oxide film mainly composed of Si in contact with the metal magnetic particles, and an outer oxide film located outside the inner oxide film and containing Al or Ti and Zr.

13. The method for producing a composite metal magnetic material according to claim 12, wherein the heat treatment step further forms an intervening portion having a peak in the Ti or Al content in the inner oxide film or a part of the outer oxide film.

14. The method for producing a composite metal magnetic material according to any one of claims 11 to 13, wherein the heat treatment step is carried out in a nitrogen atmosphere of 97% or more and 99% or less.

15. The method for producing a composite metal magnetic material according to any one of claims 11 to 14, wherein the heat treatment step is carried out by supplying hydrogen in an atmosphere such that it is 1% or more and 3% or less.

16. A method for producing a composite metal magnetic material according to any one of claims 11 to 15, wherein degreasing is performed in an oxygen atmosphere of 2 ppm to 200 ppm before the heat treatment step.

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