Magnetic alloy powder and method for manufacturing the same, coil component, and circuit board

Abstract

The present application provides a magnetic alloy powder and a manufacturing method thereof, a coil component, and a circuit board. The magnetic alloy powder is composed of magnetic particles (100) in which an alloy phase (1) is covered with an oxide film (2). The alloy phase (1) is formed of an alloy phase in which the content of Fe is 98% by mass or more and Si and at least one element (M element) other than Si that is more easily oxidized than Fe are contained. The oxide film (2) is formed so that, in the element distribution in the film thickness direction, the content of Si at the position where the content of Si is the largest in terms of mass proportion is more than the content of Fe and the content of the M element at the position, respectively. The magnetic alloy powder of the present application has a high content of Fe in the metal and excellent insulation.

Description

Technical Field

[0001] This invention relates to magnetic alloy powder and its manufacturing method, as well as coil components made from magnetic alloy powder and circuit boards on which the coil components are mounted. Background Technology

[0002] In recent years, with the increasing performance of electrical and electronic equipment, there are higher requirements for the performance and miniaturization of coil components such as inductors. The performance of coil components is affected by the amount of magnetic material they contain. Therefore, in order to achieve both miniaturization and high performance of components that are related to reducing the amount of magnetic material they contain, high-performance magnetic materials are required.

[0003] For components in the coil that carry relatively large currents, it is required that the change in inductance caused by the current be small. To meet this requirement, it is common to use metals with Fe as the main component as the magnetic material.

[0004] Since Fe-based metallic materials are electrically conductive, when forming magnetic materials from their powder, it is necessary to electrically insulate the particles constituting the powder from each other. Therefore, an insulating coating is formed on the surface of each particle constituting the metallic powder.

[0005] For example, Patent Document 1 discloses the following: a metallic magnetic powder with a composition of 9.4% Si, 5.2% Al and the remainder Fe by weight is oxidized in an oxygen-nitrogen mixed gas atmosphere with an oxygen concentration of 2% by volume at 850°C for 1 hour to form an insulating oxide coating, etc.

[0006] Furthermore, Patent Document 2 discloses the following technical concept: forming a silicone resin layer on the surface of pure iron powder particles, and then heat-treating it at a temperature of 600-650°C in a non-oxidizing atmosphere after forming, thereby forming an insulating coating on the particle surface.

[0007] In addition, Patent Document 3 discloses that Fe-1%Si atomized alloy particles are subjected to an oxidation reaction at 450°C for 2 hours in an atmosphere with a very low oxygen concentration of 100% relative humidity (room temperature) formed by mixing water vapor with nitrogen. The result is that an insulating nanofilm consisting of a 5nm thick SiO2 oxide film is formed on the particle surface.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2007-299871

[0011] Patent Document 2: Japanese Patent Application Publication No. 2015-70222

[0012] Patent Document 3: Japanese Patent Application Publication No. 2006-49625 Summary of the Invention

[0013] The technical problem that the invention aims to solve

[0014] As shown in Patent Document 1, when forming an insulating coating by heat-treating metallic magnetic powder in an oxidizing atmosphere, it is necessary to contain elements other than Fe, such as Al, in a certain amount in the metal. Therefore, the Fe content in the metal becomes relatively low, resulting in insufficient magnetic properties.

[0015] On the other hand, as shown in Patent Document 2, when using metallic magnetic powders with a high Fe content, such as pure iron, it is difficult to form an insulating coating through the oxidation of the metal components. Therefore, it is necessary to form the insulating coating by other methods, such as covering the surface of the metal particles. As a result, the insulating coating is formed to be relatively thick. During molding, the distance between the metal particles becomes larger due to the thickness of the insulating coating, which leads to a decrease in magnetic properties. In addition, there are also problems such as: the low bonding strength between the metal particles and the insulating coating, resulting in peeling or defects of the insulating coating during molding; and the increased cost of the coating process.

[0016] Furthermore, as shown in Patent Document 3, when a small amount of Si (other than Fe) in a metal is oxidized in a weakly oxidizing atmosphere to form an insulating film, the SiO2 oxide film is thin and brittle, making it susceptible to peeling or cracking during processing, exposing the metal portion and reducing insulation. Additionally, the exposed metal portion is easily oxidized by reacting with oxygen in the atmosphere, which also contributes to the reduction of magnetic properties. Therefore, the pressure applied during the molding process is limited, making it difficult to balance both insulation and filler content.

[0017] Therefore, the purpose of this invention is to provide a magnetic alloy powder with a high Fe content and excellent insulation properties that can solve the above problems, and a simple manufacturing method thereof.

[0018] Technical solutions for solving technical problems

[0019] In order to solve the above-mentioned problems, the inventors conducted various studies and discovered that by heat-treating magnetic alloy powder containing a high Fe content and other elements such as Si and Fe that are more easily oxidized, a film rich in Si oxide is formed on the surface of each particle constituting the magnetic alloy powder, thereby solving the problem and completing the present invention.

[0020] That is, the first embodiment of the present invention for solving the above-mentioned technical problems is a magnetic alloy powder, characterized in that: it is composed of magnetic particles covered by an oxide film of an alloy phase, wherein the content of Fe in the alloy phase is 98% by mass or more, and contains Si and at least one M element, wherein the M element is an element other than Si that is more easily oxidized than Fe, and in the elemental distribution along the thickness direction of the oxide film, the content of Si, expressed as a mass ratio, is greater than the content of Fe and the content of the M element in that region.

[0021] Furthermore, a second embodiment of the present invention is a method for manufacturing magnetic alloy powder, characterized in that: the magnetic alloy powder is composed of magnetic particles whose alloy phase is covered by an oxide film, and the method for manufacturing the magnetic alloy powder includes: a step of preparing a raw material powder for a magnetic alloy, wherein the Fe content in the raw material powder is 96.5% to 99% by mass, and contains Si and at least one M element, wherein the M element is an element other than Si that is more easily oxidized than Fe; and a step of heat-treating the raw material powder to form an oxide film on the surface of each particle constituting the raw material powder to obtain the magnetic alloy powder, wherein the Fe content in the alloy phase of the magnetic alloy powder is higher than that in the raw material powder, and in the elemental distribution along the film thickness direction of the oxide film, the Si content at the location where the Si content expressed in mass ratio is the largest is greater than the Fe content and the M element content at that location.

[0022] Invention Effects

[0023] According to the present invention, it is possible to provide magnetic alloy powder with a high Fe content and excellent insulation properties. Attached Figure Description

[0024] Figure 1 This is a schematic diagram showing the structure of the magnetic particles constituting the magnetic alloy powder of the first embodiment of the present invention.

[0025] Figure 2 This is an explanatory diagram illustrating an example of the structure of a composite material coil component according to an embodiment of the present invention.

[0026] Figure 3 This is an explanatory diagram illustrating an example of the structure of a wound coil component according to an embodiment of the present invention, wherein... Figure 3 (a) is the overall three-dimensional view. Figure 3 (b) is the AA cross-section of (a).

[0027] Figure 4 This is an explanatory diagram illustrating an example of the structure of a laminated coil component according to an embodiment of the present invention, wherein... Figure 4 (a) is the overall three-dimensional view. Figure 4 (b) is the BB cross-section of (a).

[0028] Figure 5 This is an explanatory diagram illustrating an example of the structure of a thin-film coil component according to an embodiment of the present invention.

[0029] Figure 6 The results show the elemental distribution along the thickness of the oxide film in the magnetic alloy powder and raw material powder of Example 6, where the solid line represents the magnetic alloy powder and the dashed line represents the raw material powder.

[0030] Explanation of reference numerals in the attached figures

[0031] 100 magnetic particles

[0032] 1 Alloy phase

[0033] 2. Oxide film. Detailed Implementation

[0034] Hereinafter, with reference to the accompanying drawings, the structure and effects of the present invention will be described interspersed with technical concepts. However, the mechanism of action includes inference, and its correctness does not limit the present invention. In addition, among the constituent elements in the following embodiments, constituent elements not described in the independent claim representing the highest concept can be described as arbitrary constituent elements. Furthermore, the description of numerical ranges (the description of two numerical values ​​connected by "~") is intended to also include numerical values ​​denoted as lower and upper limits.

[0035] (Magnetic alloy powder)

[0036] The magnetic alloy powder of the first embodiment of the present invention (hereinafter sometimes simply referred to as "the first embodiment"), such as Figure 1 As shown, the feature is that it is composed of magnetic particles 100 covered by an oxide film 2 of an alloy phase 1, wherein the alloy phase 1 contains 98% by mass or more of Fe and includes Si and at least one element other than Si that is more easily oxidized than Fe (hereinafter, sometimes referred to as "M element"). In the elemental distribution of the oxide film 2 in the film thickness direction, the content of Si, expressed as a mass percentage, is the largest at a location where the content of Si is greater than the content of Fe and the content of the aforementioned M element at that location.

[0037] In the first embodiment, alloy phase 1 contains 98% by mass or more of Fe as a constituent element. Because the alloy phase has a high Fe content, it becomes a magnetic material with excellent magnetic properties such as permeability when formed. Preferably, the Fe content in alloy phase 1 is 99% by mass or more.

[0038] In addition to Fe, the aforementioned alloy phase 1 also contains at least one element, M. Because alloy phase 1 contains Si, an oxide film 2 with high electrical insulation and a smooth surface can be formed on the surface of the magnetic particles. Furthermore, the presence of M element suppresses the oxidation of Fe, the main component of alloy phase 1, thus stabilizing magnetic properties such as permeability when forming a magnetic material.

[0039] Examples of elements that can be considered as M include Cr, Al, Ti, Zr, or Mg. Among these elements, considering the high oxidation inhibition effect of Fe, Cr or Al are preferred, with Cr being particularly preferred.

[0040] Element M can be present in alloy phase 1 as a single element or as two or more elements.

[0041] Regarding the first embodiment, it is composed of magnetic particles 100 covered by an oxide film 2 of the alloy phase 1 described above.

[0042] In the elemental distribution along the thickness direction of the oxide film 2 on the surface of the magnetic particles 100, the region with the highest Si content (expressed as a mass ratio) also has a high proportion of Fe and M elements. This means that the oxide film 2 is a thin layer containing the most Si as a constituent element. Such a thin layer has excellent insulation properties, therefore the oxide film 2 with this thin layer and the magnetic particles 100 exhibit high insulation performance.

[0043] The oxide film 2 on the surface of magnetic particles 100 preferably has a high total Si content, high total Fe content, and high total M content. Due to its high Si content, the oxide film 2 exhibits higher insulation properties.

[0044] Furthermore, the oxide film 2 preferably contains element M. Because the oxide film 2 contains element M, it can suppress the oxidation of Fe in the alloy phase 1 located inside it, and stabilize magnetic properties such as permeability when forming a magnetic body.

[0045] Here, the mass ratio of each element in alloy phase 1 and oxide film 2 was measured by the following method. Using an X-ray photoelectron spectroscopy (XPS) instrument (ULVAC-PHI, INCORPORATED. PHI Quantera II), the content ratio (atomic %) of each element, primarily iron (Fe), on the surface of the magnetic particles constituting the magnetic alloy powder was repeatedly measured, and sputtering was performed on the particle surface. This allowed the distribution of each element along the depth direction (radial) of the particles to be obtained. For the measurement of the content ratio of each element, monochromatic AlKα rays were used as the X-ray source, and the detection area was set to 100 μm. Sputtering was performed every 5 nm. The sputtering conditions were as follows: argon (Ar) was used as the sputtering gas, the applied voltage was set to 2.0 kV, and the sputtering rate was set to approximately 5 nm / min (converted to SiO2). In the measured Fe concentration distribution (atomic %), when observed from the surface side of the particles, the measurement points where the concentration difference was initially less than 1 atomic % were considered the boundary between alloy phase 1 and oxide film 2. Furthermore, the mass percentage of elements was calculated for the region shallower than this boundary (oxide film 2) and the region deeper than this boundary (alloy phase 1).

[0046] In the first embodiment, preferably all elements of Si and M contained in the alloy phase 1 are included in the oxide film 2 as a whole. The inclusion of these elements in the oxide film 2 as a whole indicates that the oxide film 2 is formed through diffusion of the components in the alloy phase 1. Regarding the magnetic alloy powder with the oxide film 2 formed through this process, the distribution of each element within the constituent particles is continuous from the interior of the particles to the outer periphery, thus reducing the stress generated within the particles. This, in turn, suppresses the decrease in the permeability of the particles themselves.

[0047] Here, the fact that all elements contained in the alloy phase 1 of Si and M are included in the oxide film 2 as a whole can be confirmed by the following method: in the distribution of each element in the depth direction (radial direction) obtained by measuring the mass ratio of each element in the alloy phase 1 and oxide film 2, all of the elements can be detected at all measurement points located in the region where the oxide film 2 is formed.

[0048] To obtain magnetic particles 100 in which all elements of the alloy phase 1 of Si and M are contained within the oxide film 2, as described later, it is effective to heat-treat the raw material powder of the magnetic alloy in a low-oxygen atmosphere (approximately 5 ppm to 500 ppm or less). By forming such an oxidizing atmosphere, vigorous oxidation reactions can be suppressed. This allows for the selective oxidation of elements that are more easily oxidized than Fe. In particular, as an element more easily oxidized than Fe, Si oxidation can be promoted. However, while the same oxidation reaction can be obtained when an even lower oxygen atmosphere is formed, the heat treatment time is longer, and the range of oxygen supply is easily limited, leading to uneven oxidation reactions due to the lack of contact between particles. Therefore, forming a low-oxygen atmosphere as described above is preferable.

[0049] In the first embodiment, the oxide film 2 preferably has a thickness of 10 nm or more. By making the oxide film 2 thicker than 10 nm, the electrical insulation between the magnetic particles 100 can be improved. Moreover, even if the oxide film 2 is damaged during processing, it can prevent the alloy phase 1 from contacting the atmosphere, and it can suppress the diffusion of oxygen from the atmosphere to the metal part, thereby suppressing the reduction of magnetic properties caused by the oxidation of Fe. The thickness of the oxide film 2 is more preferably 20 nm or more.

[0050] The upper limit of the thickness of the oxide film 2 is not particularly limited, but it is preferably 500 nm or less. When the thickness of the oxide film 2 is formed to be 500 nm or less, the smoothness of the surface of the oxide film 2 can be maintained. When it is thicker than 500 nm, the proportion of components other than Si increases, and with this, it is easy to generate unevenness on the surface. The thickness of the oxide film 2 is more preferably 200 nm or less. By making the thickness of the oxide film 2 200 nm or less, it is possible to suppress the cracking or damage of the oxide film 2 due to particle collisions during processing. In addition, when forming a magnetic material, a higher magnetic permeability can be obtained. The thickness of the oxide film 2 is more preferably 100 nm or less. Furthermore, considering the need to improve the smoothness of the surface of the magnetic particles 100 to form a magnetic alloy powder with excellent flowability, the thickness of the oxide film 2 is more preferably 50 nm or less.

[0051] Here, the thickness of the oxide film 2 is calculated by observing the cross-section of the magnetic particles 100 constituting the magnetic alloy powder using a scanning transmission electron microscope (STEM) (JEM-2100F manufactured by Nippon Electron Ltd.). The oxide film 2 is identified based on the difference in contrast (brightness) between the oxide film 2 and the alloy phase 1 inside the particles, which is based on the difference in composition. The thickness of the oxide film 2 is measured at 500,000x magnification at 10 different locations of the particles, and the average value is calculated.

[0052] The particle size in the first embodiment is not particularly limited; for example, it is possible to calculate the average particle size (median diameter (D)) based on the particle size distribution measured on a volume basis. 50 The particle size ranges from 0.5 μm to 30 μm. The average particle size is preferably from 1 μm to 10 μm. This average particle size can be measured using a particle size distribution measuring device that utilizes, for example, laser diffraction / scattering.

[0053] Furthermore, in the first embodiment, the specific surface area S (m 2 / g) and average particle size D 50 The relationship between (μm) preferably satisfies the following equation (1).

[0054] (Equation 1)

[0055] logS ≤ -0.98logD 50 +0.34 (1)

[0056] This formula is based on the specific surface area S(m²). 2 Common logarithm and average particle size D ( / g) 50 The specific surface area of ​​a powder is derived from the empirical principle that the logarithm of μm is linearly related to the surface area of ​​the powder particles. The specific surface area of ​​a powder is affected not only by the surface roughness of the particles constituting the powder but also by the particle size. Therefore, it cannot be assumed that a powder with a small specific surface area is composed of smooth particles with few surface roughness. Therefore, according to the above equation (1), the influence of particle surface condition on specific surface area is separated from the influence of particle size on specific surface area. Magnetic alloy powders with a smaller specific surface area due to the former are considered magnetic alloy powders with a smooth surface and few surface roughness. By adjusting S and D... 50 The relationship satisfies the above equation (1), and can form a powder with better flowability.

[0057] Specific surface area S (m 2 / g) and average particle size D 50 The relationship of (μm) is more preferably satisfied by the following equation (2), and even more preferably satisfied by the following equation (3).

[0058] (Equation 2)

[0059] logS ≤ -0.98logD 50 +0.30 (2)

[0060] (Equation 3)

[0061] logS ≤ -0.98logD 50 +0.25 (3)

[0062] Here, the specific surface area S is measured and calculated using a fully automated specific surface area measuring device (Macsorb manufactured by Mountech Co., Ltd.) via nitrogen adsorption. First, after degassing the sample in a heater, the amount of adsorbed nitrogen is measured by allowing the sample to adsorb and desorb nitrogen. Next, the monolayer adsorption amount is calculated using the BET1 point method based on the obtained amount of adsorbed nitrogen, and the sample's surface area is calculated using the area occupied by one nitrogen molecule and Avogadro's number. Finally, the specific surface area S of the powder is obtained by dividing the obtained sample surface area by the sample's mass.

[0063] In addition, the average particle size D 50The particle size distribution is measured and calculated using a laser diffraction / scattering particle size distribution measurement device (HORIBA, Ltd. LA-950). First, water, acting as a dispersant, is placed in a wet flow cell. Then, pre-crushed powder is added to the cell at a concentration sufficient to obtain a suitable detection signal to measure the particle size distribution. Next, the median diameter in the obtained particle size distribution is calculated, and this value is taken as the average particle size D. 50 .

[0064] (Manufacturing method of magnetic alloy powder)

[0065] In the method for manufacturing magnetic alloy powder according to the second embodiment of the present invention (hereinafter, sometimes simply referred to as "the second embodiment"), a raw material powder of a magnetic alloy is prepared, wherein the Fe content is 96.5% to 99% by mass and contains Si and at least one M element. The raw material powder is then heat-treated to obtain magnetic alloy powder composed of magnetic particles consisting of an alloy phase covered by an oxide film. Furthermore, the magnetic alloy powder is formed such that the Fe content in the alloy phase is higher than that in the raw material powder, and in the elemental distribution along the film thickness direction in the oxide film, the portion where the Si content (expressed as a mass percentage) is the largest has a higher proportion of Si, and the Fe and M element contents are also higher in that portion.

[0066] In the second embodiment, the raw material powder of the magnetic alloy contains 96.5% to 99% Fe as a constituent element. By making the Fe content 96.5% or more, a magnetic alloy powder with an alloy phase having a high Fe content can be obtained by heat treatment as described later. When a magnetic body is formed, it becomes a magnetic body with excellent magnetic properties such as permeability. The Fe content is preferably 97% or more. On the other hand, by making the Fe content 99% or less, the oxidation of Fe caused by the heat treatment described later can be suppressed, and the decrease in magnetic properties such as permeability can be suppressed. The Fe content in the alloy phase is preferably 98% or less.

[0067] The aforementioned raw material powder contains not only Fe but also Si. Because the raw material powder contains Si, a Si-rich oxide film can be formed on the surface of the magnetic particles through the heat treatment described later, resulting in high electrical insulation.

[0068] Furthermore, the aforementioned raw material powder contains at least one element M. Because the raw material powder contains element M, the element M diffuses onto the surface of the magnetic particles through the heat treatment described later, forming an oxide film containing element M. This suppresses the oxidation of Fe and inhibits the decrease in magnetic properties such as permeability. The content of element M is not particularly limited, but from the perspective of effectively suppressing the oxidation of Fe, it is preferably 0.2% by mass or more, more preferably 0.5% by mass or more.

[0069] Examples of elements that can be considered as M include Cr, Al, Ti, Zr, or Mg. Among these elements, considering the high oxidation inhibition effect of Fe, Cr or Al are preferred, with Cr being particularly preferred.

[0070] Element M can be present in the alloy phase as a single element or as two or more elements.

[0071] The particle size of the raw material powder is not particularly limited; for example, it can be calculated based on the average particle size (median diameter (D)) measured on a volume basis. 50 The particle size is 0.5 μm to 30 μm. The average particle size is preferably 1 μm to 10 μm. This average particle size can be measured, for example, using a particle size distribution measuring device that utilizes laser diffraction / scattering.

[0072] In the second embodiment, it is preferable to perform heat treatment on the raw material powder in an atmosphere with an oxygen concentration of 5 ppm to 500 ppm. By maintaining the oxygen concentration within this range, the oxidation of Si can be promoted and the oxidation of other elements can be suppressed. This allows for the formation of an oxide film containing more Si, resulting in a surface with fewer irregularities. Furthermore, by maintaining an oxygen concentration of 5 ppm or more in the heat treatment atmosphere, the diffusion of Si to the surface of the magnetic particles can be promoted, enabling the formation of a Si-rich oxide film with excellent electrical insulation properties. Simultaneously, the diffusion of element M is also promoted, and by forming an oxide film containing element M, the oxidation of Fe in the alloy can be effectively suppressed. The oxygen concentration in the heat treatment atmosphere is more preferably 50 ppm or more, and even more preferably 100 ppm or more. Additionally, by performing heat treatment in a low-oxygen atmosphere, an oxide film with a smooth surface and few minor irregularities can be formed on the surface of the magnetic particles; therefore, it is preferable that the oxygen concentration in the heat treatment atmosphere is 500 ppm or less, more preferably 400 ppm or less, and even more preferably 300 ppm or less.

[0073] The heat treatment temperature of the raw material powder is preferably 600°C or higher. By setting the heat treatment temperature to 600°C or higher, Si diffuses sufficiently on the surface of each particle constituting the raw material powder, forming an oxide film with high electrical insulation properties. Furthermore, the proportion of Fe in the alloy phase increases, improving magnetic properties such as permeability. Simultaneously, M element also diffuses sufficiently to form an oxide film containing this element, thereby effectively suppressing the oxidation of Fe in the alloy. The heat treatment temperature is preferably 650°C or higher, more preferably 700°C or higher. While there is no particular upper limit to the heat treatment temperature, considering the need to suppress excessive oxidation of Fe to obtain a magnetic material with excellent magnetic properties, 850°C or lower is preferred, more preferably 800°C or lower, and even more preferably 750°C or lower.

[0074] The heat treatment time for the raw material powder is preferably 4 hours or more. This heat treatment suppresses Fe oxidation while promoting the oxidation of components other than Fe, increasing the Fe content relative to the raw material powder. Therefore, the increased Fe content within the alloy phase improves magnetic saturation characteristics. Furthermore, although Si is oxidized, Si remains in the alloy phase, thus maintaining permeability and loss characteristics. Microscopically, this can be explained by the fact that through prolonged heat treatment, Si and M elements contained in the raw material powder diffuse sufficiently onto the surface of the magnetic particles, increasing the Fe content in the alloy phase, thereby improving magnetic properties such as permeability. The heat treatment time is preferably 5 hours or more, more preferably 10 hours or more. While there is no particular upper limit to the heat treatment time, considering the need to complete the heat treatment quickly to improve productivity, a heat treatment time of 24 hours or less is preferred, more preferably 12 hours or less.

[0075] The heat treatment in the second embodiment can be either batch processing or flow processing. As an example of flow processing, a method can be described as follows: multiple heat-resistant containers containing raw material powder of a magnetic alloy are continuously fed into a tunnel kiln, allowing it to pass through a region maintained at a specified atmosphere and temperature for a specified time.

[0076] According to the first and second embodiments described above, magnetic alloy powder with a high Fe content and excellent insulation properties can be obtained. Using this magnetic alloy powder, high-performance coil components can be obtained. The coil component manufactured from the magnetic alloy powder includes a so-called composite coil component, i.e., a coil portion, and a core portion in which the coil portion is embedded. This core portion contains magnetic alloy powder and resin. Due to the advantages described above in the first and second embodiments, a component with excellent magnetic properties, durability, and reliability is formed, and miniaturization of the component is also possible. Furthermore, high performance and miniaturization of the circuit board on which such a coil component is mounted can also be achieved. Therefore, the composite coil component and circuit board, which are preferred embodiments of the present invention, will be described below as the third and fourth embodiments.

[0077] (Coil component)

[0078] The coil component of the third embodiment of the present invention (hereinafter, sometimes simply referred to as "the third embodiment") is a coil component, characterized in that: the coil component includes a coil portion made of a metal conductor and a magnetic matrix containing magnetic alloy particles, wherein the magnetic alloy particles are magnetic alloy particles constituting the magnetic alloy powder of the first embodiment.

[0079] Regarding the configuration of the coil section, it can also be embedded in the magnetic substrate. Alternatively, it can be wound around the magnetic substrate.

[0080] The magnetic matrix contains magnetic alloy particles that constitute the magnetic alloy powder of the first embodiment.

[0081] Regarding the structure of the magnetic matrix, it can contain resin in addition to magnetic alloy particles, creating a structure that maintains shape through the action of the resin. Alternatively, it can be a structure in which the magnetic alloy particles maintain shape by bonding with each other using the aforementioned oxide film.

[0082] As a third implementation, an example is shown below. Figure 2 The composite material coil component shown Figure 3 The winding coil component shown Figure 4 The stacked coil components shown are Figure 5 The thin-film coil component shown is an example.

[0083] As a third embodiment of the manufacturing method, for example, in the case of a composite material coil component, typically, magnetic alloy powder and resin are mixed and prepared into a mixture, and then the mixture is put into a forming mold such as a metal mold pre-configured with a hollow coil. After pressure molding, the resin is cured to obtain the coil component.

[0084] The magnetic alloy powder used has already been explained above, so the explanation is omitted here.

[0085] The resin used can be any resin that can bond the magnetic alloy powder particles together to form and maintain their shape; there are no restrictions on the type, and various resins such as epoxy resin or silicone resin can be used. There are also no restrictions on the amount of resin used; for example, 1 to 10 parts by weight relative to 100 parts by weight of the magnetic alloy powder can be used. In the second embodiment, when using magnetic alloy powder obtained by heat treatment of the raw material powder in a low-oxygen atmosphere, the excellent flowability of this magnetic alloy powder allows for a reduction in the amount of resin used and an increase in the proportion of magnetic alloy powder. Therefore, it is preferable that the amount of resin used is 3 parts by weight or less relative to 100 parts by weight of the magnetic alloy powder.

[0086] There are no restrictions on the mixing of magnetic alloy powder and resin, or on the method of adding the mixture to the molding die. Besides adding the mixture in a flowing state to the molding die, methods such as adding granulated magnetic alloy powder coated with resin to the molding die are also possible. Furthermore, as a method for simultaneously adding the mixture to the molding die and performing the pressure molding described later, a method of introducing the mixture, shaped into a sheet, into the molding die under pressure can also be used.

[0087] There are no restrictions on the temperature and pressure of the pressure molding process. The appropriate temperature and pressure can be determined based on the material and shape of the hollow coil placed in the mold, the flowability of the magnetic alloy powder added, and the type and amount of resin added.

[0088] The curing temperature of the resin should be determined appropriately based on the resin used.

[0089] The magnetic matrix of the third embodiment can be formed by pressing a mixture of magnetic alloy powder and resin into shape, and then heat-treating the resulting molded body at a temperature higher than the curing temperature of the resin. In this case, the resin decomposes due to the heat treatment, and an oxide film grows on the surface of the magnetic alloy particles, which binds the magnetic alloy particles together. Furthermore, the resin components are substantially decomposed due to the heat treatment, although carbon may still remain in some areas.

[0090] By winding a wire around the magnetic substrate thus obtained, a wound coil component can be obtained. The wound coil component is also an example of the coil component in the third embodiment.

[0091] Furthermore, when the coil component is a laminated coil component, it can be manufactured using a sheet method. The sheet method involves first mixing magnetic alloy powder and resin to create a mixture, then applying it to a sheet using a scraper or similar method. After cutting the sheet, through holes are made at predetermined locations using a laser or similar tool, and internal patterns are printed at predetermined locations. Next, these sheets are laminated in a predetermined order and heat-pressed to obtain a laminate. Then, as needed, the laminate is cut to the dimensions of each component using a cutting machine or laser cutting machine. Finally, the laminate is heat-treated to obtain the laminated coil component. This laminated coil component is also an example of the coil component in the third embodiment.

[0092] Furthermore, when the coil component is a thin-film coil component, photolithography can be used. The thin-film coil component is also an example of the third embodiment.

[0093] In addition to the manufacturing methods exemplified above, known manufacturing methods corresponding to the shape of the coil components can also be used.

[0094] In the third embodiment, a magnetic alloy powder with a high Fe content and excellent insulation properties is used as the magnetic alloy powder, thus forming a high-performance coil component. As a result, the coil component can be miniaturized because the size of the components required to obtain the same inductance can be reduced.

[0095] (Circuit board)

[0096] The circuit board of the fourth embodiment of the present invention (hereinafter, sometimes simply referred to as "the fourth embodiment") is a circuit board equipped with the coil component of the third embodiment.

[0097] There are no restrictions on the structure of the circuit board; any circuit board appropriate for the purpose can be used.

[0098] In the fourth embodiment, by using the coil component of the third embodiment, high performance and miniaturization can be achieved.

[0099] (Example)

[0100] The present invention will be described in more detail below through embodiments, but the present invention is not limited to these embodiments.

[0101] (Example 1)

[0102] The raw material powder of a magnetic alloy with a composition of 96% Fe, 2% Si, 1% Cr, and 1% Al and an average particle size of 4.0 μm was placed in a zirconia container and placed in a vacuum heat treatment furnace.

[0103] Next, the oxygen concentration in the furnace was reduced to 5 ppm by venting the furnace, and then the temperature was increased to 650°C at a rate of 5°C / min. After heat treatment for 5 hours, the furnace was cooled to room temperature to obtain the magnetic alloy powder of Example 1.

[0104] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the method described above: Fe was 98.0% by mass, Si was 1.0% by mass, Cr was 0.8% by mass, and Al was 0.2% by mass.

[0105] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the method described above. It was confirmed that Si was the most abundant element at the measurement location where the Si content was the highest, and Cr and Al were also present at the measurement location.

[0106] Furthermore, regarding the obtained magnetic alloy powder, the thickness of the oxide film formed on the surface of the magnetic particles was measured using the method described above, and it was found to be 20 nm.

[0107] (Example 2)

[0108] The magnetic alloy powder of Example 2 was obtained in the same manner as in Example 1, with the oxygen concentration of the atmosphere during heat treatment being 100 ppm.

[0109] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the same method as in Example 1, with Fe being 98.1% by mass, Si being 0.8% by mass, Cr being 0.7% by mass, and Al being 0.4% by mass.

[0110] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1. It was confirmed that Si was the element with the highest Si content at the measurement location, and Cr and Al were also present at the measurement location.

[0111] Furthermore, regarding the obtained magnetic alloy powder, the thickness of the oxide film formed on the surface of the magnetic particles was measured using the same method as in Example 1, and was 45 nm.

[0112] (Example 3)

[0113] The heat treatment was held for 10 hours, otherwise the process was the same as in Example 1, and the magnetic alloy powder of Example 3 was obtained in this manner.

[0114] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the same method as in Example 1, with Fe being 98.3% by mass, Si being 1.7% by mass, Cr being 0.6% by mass, and Al being 0.4% by mass.

[0115] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1. It was confirmed that Si was the element with the highest Si content at the measurement location, and Cr and Al were also present at the measurement location.

[0116] (Comparative Example 1)

[0117] The raw material powder of a magnetic alloy with a composition of 96% Fe, 2% Si, and 2% Cr and an average particle size of 4.0 μm was placed in a zirconia container and placed in a heat treatment furnace.

[0118] Next, the temperature was increased to 650°C in an atmospheric atmosphere at a heating rate of 5°C / min and held for 5 hours for heat treatment. After that, the furnace was cooled to room temperature to obtain the magnetic alloy powder of Comparative Example 1.

[0119] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the method described above. The mass ratios were 97.3% Fe, 1.8% Si, and 0.9% Cr.

[0120] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1 above. It was confirmed that at the measurement location where the Si content was the largest, the element with the most content was Cr, and Si was also present at that measurement location.

[0121] (Comparative Example 2)

[0122] As the raw material powder for the magnetic alloy, a raw material powder having a composition of 98% by mass of Fe and 2% by mass of Si and an average particle size of 4.0 μm was used. Otherwise, the same method as in Example 3 was used to obtain the magnetic alloy powder of Comparative Example 2.

[0123] Regarding the obtained magnetic alloy powder, the thickness of the oxide film formed on the surface of the magnetic particles was measured using the same method as in Example 1 above, and was 320 nm. In this comparative example, since the raw material powder does not contain M element, it can be understood that Si was oxidized during heat treatment, resulting in a relatively thick oxide film.

[0124] Based on a comparison of the composition of the raw material powder and the magnetic alloy powder in Examples 1, 2, and 3, it was determined that the mass proportion of Fe in the alloy phase increased after heat treatment, while the mass proportion of Si, Cr, or Al decreased. In the oxide film formed on the surface of the magnetic particles constituting the magnetic alloy powder, since the mass proportion of Si, Cr, or Al is higher than that of the alloy phase, it can be said that the Si, Cr, or Al in the alloy phase diffused to the surface of the magnetic particles and formed oxides after heat treatment.

[0125] The magnetic alloy powder in this embodiment, due to its high Fe mass ratio in the alloy phase of the magnetic particles, can be said to be able to form coil components with small inductance changes relative to current. Furthermore, a Si-rich oxide film is formed on the surface of the magnetic particles, thus the magnetic alloy powder of this embodiment exhibits excellent insulation properties. Moreover, the magnetic alloy powder of this embodiment contains Cr or Al as M elements in the oxide film, thus exhibiting excellent oxidation resistance. In fact, after the magnetic alloy powder of this embodiment was placed in the atmosphere for several days, the composition of the magnetic particles and the thickness of the oxide film were measured, and no changes were confirmed.

[0126] (Example 4) (Evaluation of the coil component)

[0127] The magnetic alloy powder from Example 1 was mixed with resin to form a mixture. This mixture was then filled into a molding die containing a hollow coil. After pressure molding, the resin was cured by heating to obtain a magnetic body. Electrodes were formed on the surface of the magnetic body, and a coil component was formed by making them conductive with the coil.

[0128] The obtained coil component, as expected based on the structure of the magnetic particles constituting the magnetic alloy powder, namely the high mass proportion of Fe in the alloy phase and the formation of a Si-rich oxide film on the particle surface, exhibits high specific permeability, saturation magnetic flux density, and excellent insulation.

[0129] (Example 5)

[0130] In order to study the effect of heat treatment temperature on the elemental distribution of magnetic particles, magnetic alloy powder was manufactured by changing the heat treatment temperature of the raw material powder in Examples 5 and 6.

[0131] The heat treatment temperature was set to 700°C, otherwise the process was the same as in Example 1, and the magnetic alloy powder of Example 5 was obtained in this manner.

[0132] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the same method as in Example 1, with Fe being 98.1% by mass, Si being 1.0% by mass, Cr being 0.7% by mass, and Al being 0.2% by mass.

[0133] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1. It was confirmed that at the measurement location where the Si content was the largest, the element containing the most Si was Si. In addition, Cr and Al were also present at this measurement location.

[0134] (Example 6)

[0135] The heat treatment temperature was set to 750°C, otherwise the process was the same as in Example 1, and the magnetic alloy powder of Example 6 was obtained in this manner.

[0136] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the same method as in Example 1, with Fe being 98.3% by mass, Si being 1.1% by mass, Cr being 0.4% by mass, and Al being 0.2% by mass.

[0137] Furthermore, regarding the obtained magnetic alloy powder and the raw material powder used, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1. The results are expressed as follows: Figure 6 In the figure, solid lines represent the results of the magnetic alloy powder of Example 6, and dashed lines represent the results of the raw material powder used. Based on these results, it was confirmed that in the elemental distribution along the film thickness direction, the Si content at the measurement location (around 6 nm from the surface) is greater than that of Fe and M elements (the combined amount of Cr and Al), and that M element is present at this measurement location.

[0138] Based on the comparison of Examples 1, 5, and 6, it was confirmed that the proportion of Fe in the alloy phase of the magnetic particles increased as the heat treatment temperature increased. According to this result, it can be said that by increasing the heat treatment temperature within a range where Fe will not be excessively oxidized, the proportion of Fe in the alloy phase can be increased, thereby improving magnetic saturation characteristics.

[0139] (Example 7)

[0140] In this embodiment, it was confirmed that even if the raw material powder contains only one type of element M, it is possible to obtain magnetic alloy powder with the desired microstructure.

[0141] As the raw material powder, a magnetic alloy having a composition of 96.5% by mass of Fe, 2% by mass of Si, and 1.5% by mass of Cr was used. Otherwise, the same method as in Example 1 was used to obtain the magnetic alloy powder of Example 7.

[0142] Regarding the obtained magnetic alloy powder, the mass ratio of each element in the alloy phase constituting the magnetic particles was measured using the same method as in Example 1, with Fe being 98.3% by mass, Si being 1.0% by mass, and Cr being 0.7% by mass.

[0143] In addition, regarding the obtained magnetic alloy powder, the mass ratio of each element in the oxide film constituting the magnetic particles was measured using the same method as in Example 1. It was confirmed that Si was the element with the highest content at the measurement location, and Cr was also present at the measurement location.

[0144] Industrial availability

[0145] This invention provides a magnetic alloy powder with a high Fe content in the alloy phase and excellent insulation properties. This magnetic alloy powder is useful in forming magnetic materials with excellent magnetic properties and high-performance coil components. Furthermore, in a preferred embodiment of the invention where the oxide film contains the Fe element, the Fe in the alloy phase is less prone to oxidation, which is advantageous in obtaining stable magnetic properties.

Claims

1. A magnetic alloy powder, characterized by: magnetic particles covered with an oxide film on an alloy phase, the alloy phase containing Fe in an amount of 98 mass% or more and containing Si and at least one M element which is an element other than Si that is more easily oxidized than Fe, in an element distribution in a film thickness direction of the oxide film, a content of Si at a position where the content of Si becomes the largest in a mass ratio is more than a content of Fe at the position and a content of the M element at the position, respectively.

2. The magnetic alloy powder according to claim 1, characterized in that: in the oxide film, a total content of Si is more than a total content of Fe and a total content of the M element, respectively.

3. The magnetic alloy powder according to claim 1 or 2, characterized in that: the oxide film contains the M element.

4. The magnetic alloy powder according to claim 1 or 2, characterized in that: the oxide film contains, in the entire film, Si and all of the M elements contained in the alloy phase.

5. The magnetic alloy powder according to claim 1 or 2, characterized in that: the M element is Cr, Al, Ti, Zr, or Mg.

6. The magnetic alloy powder according to claim 1 or 2, characterized in that: the M element includes Cr.

7. A method for producing a magnetic alloy powder, characterized by: the magnetic alloy powder being composed of magnetic particles covered with an oxide film on an alloy phase, the method for producing the magnetic alloy powder including: a step of preparing a raw material powder of a magnetic alloy, the raw material powder of the magnetic alloy containing Fe in an amount of 96.5 mass% to 99 mass% and containing Si and at least one M element which is an element other than Si that is more easily oxidized than Fe; and a step of subjecting the raw material powder to heat treatment to form the oxide film on surfaces of each particle constituting the raw material powder to obtain the magnetic alloy powder, in the magnetic alloy powder, a content ratio of Fe in the alloy phase is higher than in the raw material powder, and in an element distribution in a film thickness direction of the oxide film, a content of Si at a position where the content of Si becomes the largest in a mass ratio is more than a content of Fe at the position and a content of the M element at the position, respectively.

8. The method for producing the magnetic alloy powder according to claim 7, characterized in that: in the oxide film of the magnetic alloy powder, a total content of Si is more than a total content of Fe and a total content of the M element, respectively.

9. The method for producing the magnetic alloy powder according to claim 7 or 8, characterized in that: a content of Fe in the alloy phase is 98 mass% or more.

10. The method for producing the magnetic alloy powder according to claim 7 or 8, characterized in that: the heat treatment is performed at a temperature of 600°C to 850°C for 10 hours or more in an atmosphere having an oxygen concentration of 5 ppm to 500 ppm.

11. The method for producing the magnetic alloy powder according to claim 7 or 8, characterized in that: the heat treatment is performed so that the oxide film contains the M element.

12. The method for producing the magnetic alloy powder according to claim 7 or 8, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ The heat treatment is performed so that the entirety of the oxide film contains Si and all of the M elements contained in the alloy phase.

13. The method of producing a magnetic alloy powder according to claim 7 or 8, characterized in that: The M element is Cr, Al, Ti, Zr, or Mg.

14. The method of producing a magnetic alloy powder according to claim 7 or 8, characterized in that: The M element contains Cr.

15. A coil member characterized by: comprising a coil portion composed of a metal conductor and a magnetic base containing magnetic alloy particles, The magnetic alloy particles are the magnetic alloy particles that constitute the magnetic alloy powder according to any one of claims 1 to 6.

16. A circuit board characterized by: The circuit board mounts the coil member according to claim 15.

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