Soft magnetic powder, magnetic core, magnetic component, and electronic device

Abstract

This invention provides a soft magnetic powder that can improve core loss regardless of the composition of the soft magnetic metal particles. In the soft magnetic powder of this invention, the relationship between the average cumulative frequency of the number of particles from the first to the fourth particle group and the average area envelope of each particle group is depicted in an imaginary two-dimensional coordinate system. The depicted data is linearly approximated using the least squares method. When the slope of the resulting approximate straight line is set as my, the absolute value of my, |my|, is between 0.005 and 0.500.

Description

Technical Field

[0001] This invention relates to soft magnetic powder, magnetic core, magnetic components, and electronic devices. Background Technology

[0002] Inductors, transformers, and choke coils are commonly used in the power circuits of various electronic devices. These components consist of coils and magnetic cores located inside the coils. In recent years, soft magnetic powders containing soft magnetic metal particles have largely replaced ferrites as the material for magnetic cores. This is because soft magnetic metals have higher saturation magnetization (saturation magnetic flux density) and better DC superposition characteristics (allowing for larger DC superposition currents) compared to ferrites, making them suitable for miniaturization of electronic components (magnetic cores).

[0003] However, when soft magnetic metals are used in the magnetic core, eddy currents are easily generated within the core due to the conduction between multiple soft magnetic metal particles. That is, core losses (eddy current losses) are easily generated when soft magnetic metals are used in the magnetic core. Due to core losses, the efficiency of the power supply circuit decreases, and the power consumption of electronic devices increases. Therefore, it is necessary to reduce core losses (see Patent Document 1).

[0004] Traditionally, core losses have been reduced by controlling the composition of soft magnetic metal particles and the composition of the oxide coating. However, when the composition of the soft magnetic metal particles is determined, the permeability and DC superposition characteristics are also fixed, thus limiting design freedom. Therefore, it is urgent to find other factors that can reduce iron losses, independent of the composition of the soft magnetic metal particles.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent document 1: Japanese Patent Application Publication No. 2021-27327. Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] The present invention was made in view of the following actual situation, and its object is to provide a soft magnetic powder that can improve core loss regardless of the composition of the soft magnetic metal particles.

[0010] Technical means for solving problems

[0011] To achieve the above objectives, one aspect of the present invention involves a soft magnetic powder comprising soft magnetic metal particles having a particle size distribution. The soft magnetic metal particles comprising particles whose cumulative frequency of particle size distribution exceeds 30% but is less than 40% are classified as a first particle group, particles whose cumulative frequency exceeds 50% but is less than 60% are classified as a second particle group, particles whose cumulative frequency exceeds 70% but is less than 80% are classified as a third particle group, and particles whose cumulative frequency exceeds 90% are classified as a fourth particle group. An imaginary two-dimensional coordinate system is established with the cumulative frequency of particle size distribution as the horizontal axis and the area envelope of the soft magnetic metal particles as the vertical axis. The relationship between the average cumulative frequency of particle size distribution and the average area envelope of each particle group from the first to the fourth particle group is plotted on the imaginary two-dimensional coordinate system. The plotted data is linearly approximated using the least squares method. When the slope of the resulting approximate straight line is set as my, the absolute value of my, |my|, is 0.005 to 0.500, preferably 0.010 to 0.300.

[0012] The inventors conducted in-depth research on soft magnetic powders that can improve core loss regardless of the composition of soft magnetic metal particles, and found that soft magnetic powders with the above-mentioned structure can improve core loss, thus completing the present invention.

[0013] Preferably, the median particle size in the volume reference of the soft magnetic metal particles is 1 μm or more and 50 μm or less, and more preferably 2 μm or more and 35 μm or less.

[0014] One embodiment of the magnetic core of the present invention comprises the soft magnetic powder described above.

[0015] One aspect of the magnetic component of the present invention comprises the soft magnetic powder described above.

[0016] An electronic device according to one aspect of the present invention includes the magnetic component described above. Attached Figure Description

[0017] Figure 1 This is a schematic cross-sectional view of a coil component of a magnetic core having an exemplary embodiment of the present invention.

[0018] Figure 2 yes Figure 1 The cross-sectional view of the magnetic core shown.

[0019] Figure 3 This is a schematic diagram illustrating the calculation method for the envelope of magnetic metal particles.

[0020] Figure 4 This is a schematic cross-sectional view showing the apparatus used to manufacture the soft magnetic powder in the embodiment.

[0021] Figure 5A From along Figure 4 The bottom view of the device, showing the direction of the arrow on the VV line.

[0022] Figure 5B This is a bottom view of an existing example device.

[0023] Figure 6 This is a graph showing the relationship between the cumulative frequency and area envelope of the soft magnetic powders in the embodiments and comparative examples of the present invention. Detailed Implementation

[0024] The implementation method will be described below.

[0025] First Implementation Method

[0026] like Figure 1 As shown, the coil component 2 with a magnetic core 6, which is an example of a magnetic component in this embodiment, has a winding portion (coil) 4 made of conductor 5 inside the magnetic core 6. Figure 2 An example of an enlarged cross-sectional view of magnetic core 6.

[0027] like Figure 2 As shown, the magnetic core 6 of this embodiment may comprise a resin 6b, having a structure in which a soft magnetic powder comprising a plurality of soft magnetic metal particles 6a is dispersed within the resin 6b. The soft magnetic powder of this embodiment may comprise soft magnetic metal particles having single or multiple pores.

[0028] There are no particular restrictions on the type and content of resin 6b. For example, thermosetting resins such as phenolic resin and epoxy resin can be used as examples of resin types. When the magnetic core 6 contains resin, the content of resin 6b in the magnetic core 6 is preferably 1% by mass or more and 5% by mass or less relative to the soft magnetic alloy.

[0029] The soft magnetic metal particles 6a are preferably composed of soft magnetic metals (including alloys) containing Fe or Co.

[0030] The soft magnetic metal in this embodiment can be composed of the formula (Fe). 1-（α+β） X1 α X2 β ) 1-（a+b+c+d+e+f+g） M a B b P c Si d Cr e C f S gThe soft magnetic powder is composed of (atomic ratio), where X1 is selected from one or more of Co and Ni, X2 is selected from one or more of Mn, Ag, Zn, As, Sn, Cu, Bi, N, O, rare earth elements and platinum group elements, and M is selected from one or more of Nb, Hf, Zr, Ta, Mo, W, Al, Ti and V.

[0031] It can be: α≥0

[0032] 0≤β≤0.030

[0033] 0≤a≤0.200

[0034] 0≤b≤0.250

[0035] 0≤c≤0.200

[0036] 0≤d≤0.200

[0037] 0≤e≤0.130

[0038] 0≤f≤0.070

[0039] 0≤g≤0.070

[0040] 0.600≤1―(a+b+c+d+e+f+g)≤1.000.

[0041] Additionally, the preferred value is: 0 ≤ α ≤ 0.800

[0042] 0≤β≤0.030

[0043] 0≤a≤0.140

[0044] 0.02≤b≤0.200

[0045] 0≤c≤0.100

[0046] 0≤d≤0.130

[0047] 0≤e≤0.110

[0048] 0≤f≤0.050

[0049] 0 ≤ g ≤ 0.050

[0050] 0.650≤1―(a+b+c+d+e+f+g)≤1.000.

[0051] By ensuring that the soft magnetic metal particles contained in the soft magnetic powder of this embodiment meet the above-mentioned composition range, an improvement in core loss can be expected in a magnetic core containing the soft magnetic powder of this embodiment.

[0052] As an unavoidable impurity, the soft magnetic metal particles contained in the soft magnetic powder of this embodiment may also contain elements other than those mentioned above, namely, elements other than Fe, X1, X2, M, B, P, Si, Cr, C, and S. For example, they may contain less than 1% by mass relative to 100% by mass of the soft magnetic metal (including alloys).

[0053] The median particle size of the soft magnetic metal particles contained in the soft magnetic powder of this embodiment is not particularly limited in terms of volume, but is preferably 1 μm or more and 50 μm or less in terms of the area circle equivalent diameter, and more preferably 2 μm or more and 35 μm or less. Hereinafter, the area circle equivalent diameter will sometimes be simply referred to as the circle equivalent diameter. In addition, the area circle equivalent diameter is sometimes also referred to as the Heywood diameter.

[0054] The microstructure of the soft magnetic metal particles contained in the soft magnetic powder of this embodiment is not particularly limited, but it is preferable to have a structure composed of amorphous material, heteromorphic amorphous material, or nanocrystalline material. This is because it is easy to improve the core loss in the magnetic core using the soft magnetic powder of this embodiment.

[0055] In this embodiment, an amorphous structure refers to a structure with an amorphization rate X of 85% or higher, where no crystals are observed. A structure composed of heteroamorphous materials refers to a structure with an amorphization rate X of 85% or higher, where crystals exist within the amorphous material. A structure composed of nanocrystals refers to a structure with an amorphization rate X of less than 85% and an average crystal grain size of less than 100 nm. A structure composed of crystals refers to a structure with an amorphization rate X of less than 85% and an average crystal grain size exceeding 100 nm.

[0056] When the soft magnetic powder of this embodiment has a structure composed of heterogeneous amorphous materials, the average crystal grain size is preferably 0.1 nm or more and 10 nm or less. When the soft magnetic powder of this embodiment has a structure composed of nanocrystals, the average crystal grain size is preferably 3 nm or more and 50 nm or less.

[0057] There are no particular limitations on the methods for evaluating amorphization rate X. It can also be determined by EBSD (crystal orientation analysis) and electron beam diffraction. Additionally, XRD is also used.

[0058] The following describes the method for evaluating amorphization using XRD. It should be noted that there are no particular limitations on the method for evaluating the average grain size; it can be appropriately evaluated using commonly used methods such as TEM-based observation or the Scherrer method based on XRD.

[0059] When evaluating the amorphization rate X by XRD, the amorphization rate X is calculated by the following formula (1).

[0060] X=100-(Ic / (Ic+Ia)×100)…(1)

[0061] Ic: Integral intensity of crystalline scattering

[0062] Ia: Integral intensity of amorphous scattering

[0063] The amorphization rate X is obtained by performing X-ray crystal structure analysis on soft magnetic powder using XRD, identifying the phase, reading the peak of Fe or compound after crystallization (Ic: integrated intensity of crystalline scattering, Ia: integrated intensity of amorphous scattering), and calculating the crystallization rate from the peak intensity using the above formula (1).

[0064] In this embodiment, such as Figure 2 As shown, by cutting off the cross-section of the magnetic core 6 and observing the cut surface, the particle size of each particle 6a, the cumulative frequency of the number of particles, and the area envelope of each particle 6a can be determined. There are no particular restrictions on the calculation methods for particle size and area envelope.

[0065] Figure 3 This is a graph used to illustrate area envelope. To calculate area envelope, for example... Figure 3 As shown, firstly, for each particle 6a, the perimeter L of the envelope surrounding the particle 6a is estimated by contacting the convex outer shell of the particle 6a but not the concave outer shell. The estimation of the perimeter L can be achieved using methods such as Sklansky's algorithm, the gift wrapping method, Graham scan, and QuickHull. Next, for each particle 6a, the actual area S1 of the particle 6a and the internal area S2 of the perimeter L corresponding to that particle 6a are calculated. The ratio of S1 to S2 is then used as the area envelope degree for each particle 6a. Furthermore, as mentioned above, the particle diameter of each particle 6a is determined using the area circle equivalent diameter.

[0066] For example, analysis programs can be used to calculate particle size and area envelope. However, when using analysis programs, there is a possibility that parts that are clearly not particles may be identified as particles, so such parts should be appropriately excluded from the calculation. In addition, particles that are truncated at the edge of the image should not be included in the calculation of particle size and area envelope, and it is preferable to observe at least 1000 particles 6a.

[0067] Particle size and area envelope can be analyzed using the Morphologi G3 (Malvern Panalytical), a particle image analysis device, and the same tendency can be observed in this case. The Morphologi G3 is a device capable of dispersing powder by air, projecting individual particle shapes, and evaluating the resulting projection images.

[0068] In this embodiment, for example, what is observed in the cross-section, such as Figure 2 The particles in the soft magnetic metal particles 6a observed in that way are classified as follows: particles with a cumulative frequency of particle size exceeding 30% and below 40% are classified as the first particle group; particles exceeding 50% and below 60% are classified as the second particle group; particles exceeding 70% and below 80% are classified as the third particle group; and particles exceeding 90% are classified as the fourth particle group, satisfying the relationship shown below.

[0069] like Figure 6 As shown, an imaginary two-dimensional coordinate system is set with the cumulative frequency of the number of soft magnetic metal particles 6a as the horizontal axis and the area envelope of the soft magnetic metal particles 6a as the vertical axis. The relationship between the average cumulative frequency of the number of particles from the first particle group to the fourth particle group and the average area envelope of each particle group is plotted on this two-dimensional coordinate system.

[0070] The data plotted in this way is linearly approximated using the least squares method. In this embodiment, if the slope of the resulting approximate line is set to my, then... Figure 6 As shown by the approximate straight line A1 or A2, the absolute value of the slope my of the approximate straight line, |my|, is 0.005 to 0.500, preferably 0.010 to 0.300. Furthermore, in conventional soft magnetic powders containing soft magnetic metal particles, such as... Figure 6 As shown in the approximate straight line B1, the absolute value of the slope my of the approximate straight line, |my|, is greater than 0 and less than 0.005.

[0071] In a magnetic core containing soft magnetic metal particles 6a of this embodiment with such a relationship, it was observed that the core loss could be improved regardless of the composition of the soft magnetic metal particles.

[0072] The following describes a method for manufacturing a coil component 2 containing the soft magnetic powder of this embodiment.

[0073] First, the soft magnetic powder of this embodiment is manufactured. The method for manufacturing the soft magnetic powder of this embodiment is not particularly limited. The soft magnetic metal powder of this embodiment can be manufactured by methods such as water atomization, gas atomization, or spray pyrolysis. Alternatively, for example, the soft magnetic metal powder can be manufactured by pulverizing a metal strip. Preferably, the soft magnetic metal powder is manufactured by... Figure 4 and Figure 5A The atomizing device 20 shown produces soft magnetic powder using either water atomization or gas atomization. By controlling the amount of molten metal and the water pressure (or gas pressure) using the atomizing device 20, the soft magnetic metal particles 6a of this embodiment, in which the relationship between the cumulative frequency and the area envelope based on the number of particles, can be easily obtained.

[0074] like Figure 4 As shown, the atomizing device 20 has a heat-resistant container 22 for containing molten metal 21. A heating coil 24 is arranged on the outer periphery of the heat-resistant container 22 to heat the molten metal 21 contained inside the container 22 and maintain it in a molten state. A molten metal outlet 23 is formed at the bottom of the container 22, from which the molten metal 21 is ejected as dripping molten metal.

[0075] An injection device 26 is disposed on the outer side of the bottom wall of the container 22 in a manner that surrounds the molten metal outlet 23. The injection device 26 has injection holes 27. High-pressure water or high-pressure gas is injected from the injection holes 27 toward the dripping molten metal discharged from the molten metal outlet 23.

[0076] like Figure 5A As shown, in this embodiment, the structure includes a plurality of injection holes 27 arranged around the molten metal ejection outlet 23, with first injection holes 27a and second injection holes 27b having an inner diameter D2 smaller than the inner diameter D1 of the first injection hole 27a arranged alternately along the circumferential direction at predetermined intervals W. Furthermore, the number and position of the first injection holes 27a and the second injection holes 27b are not particularly limited.

[0077] D2 / D1 is not particularly limited as long as it is less than 1, but is preferably 4 / 5 to 1 / 3, 3 / 4 to 1 / 3, or 2 / 3 to 1 / 3. Furthermore, the specified interval W is not particularly limited, but for example, it is approximately 1 / 2 or more of the inner diameter D2 of the second injection hole 27b, and less than 3 times the inner diameter D1 of the first injection hole 27a. Additionally, as... Figure 5B As shown, in the conventional injection device 26α, injection holes 27c of the same diameter are arranged at predetermined intervals along the circumference.

[0078] High-pressure water and high-pressure gas are ejected from the molten metal outlet 23 and sprayed diagonally downwards at an angle θ1 around the molten metal. The molten metal drips down as multiple droplets, which are then transported along the flow of high-pressure water and high-pressure gas to the cooling or recovery device located below.

[0079] In this embodiment, the particle size of the soft magnetic metal particles 6a can be adjusted by appropriately changing the atomization conditions. Alternatively, the particle size can be adjusted by using dry classification or wet classification. Examples of dry classification methods include sieving using a dry sieve and airflow classification. Examples of wet classification methods include classification based on wet filter filtration and classification based on centrifugal separation.

[0080] The molten metal 21 with the above composition is easily oxidized by brief contact with air, thus forming an oxide film. If an oxide film forms, it is difficult to miniaturize. When injecting gas from the injection hole 27, using an inert gas or a reducing gas can prevent the formation of an oxide film, thus facilitating pulverization. Examples of inert gases include nitrogen, argon, and helium. Examples of reducing gases include ammonia decomposition gas. High-pressure water jets can also be injected from the injection hole 27.

[0081] By use Figure 4 and Figure 5A The soft magnetic powder composed of soft magnetic metal particles 6a produced by the spraying device 26 shown is, for example, a soft magnetic powder composed of soft magnetic metal particles 6a. Figure 6 The approximate relationship between lines A1 and A2 is shown, where the absolute value of the slope my, |my|, is 0.005 to 0.500, preferably 0.010 to 0.300. Furthermore, due to the use of... Figure 5B The soft magnetic powder, composed of soft magnetic metal particles, produced by the conventional jetting device 26α, is, for example, Figure 6 The approximate straight line B1 is shown, and the absolute value of the slope my of the approximate straight line, |my|, is less than 0.005.

[0082] In this embodiment, a coating layer with a composition different from that of the soft magnetic particles can be formed on the surface of the soft magnetic powder. This coating layer can also be formed by a coating method. Even if a coating layer is formed on the surface of the soft magnetic metal particles, in this embodiment, for example, at... Figure 6 The approximate straight lines A1 or A2 shown above have a relationship where the absolute value of the slope my of the approximate straight line, |my|, also satisfies the above relationship. Alternatively, a coating layer can be formed on the surface of soft magnetic metal particles in a manner that satisfies the above relationship.

[0083] A magnetic core can be obtained by shaping the soft magnetic powder obtained as described above into a molding powder. The molding method is not particularly limited. As an example, a method for obtaining a magnetic core by pressure molding will be described.

[0084] First, the soft magnetic powder is mixed with resin. By mixing the resin, a molded article with high strength can be easily obtained through molding. There are no particular limitations on the type of resin. Examples include phenolic resin and epoxy resin. There are also no particular limitations on the amount of resin added. When adding resin, it can be added at more than 1% by mass and less than 5% by mass relative to the magnetic powder. At this time, soft magnetic metal powder other than the soft magnetic metal powder of this embodiment and / or non-magnetic powder can also be added. In addition, modifiers, preservatives, dispersants, etc. can also be added.

[0085] A resin composite is obtained by mixing soft magnetic powder and resin. The resin composite can be a granulated powder. There are no particular limitations on the granulation method. For example, a mixer can also be used for granulation. There are no particular limitations on the particle size of the granulated powder.

[0086] The obtained resin composite is press-molded to obtain a molded body. There are no particular limitations on the molding pressure. Then, the resin contained in the molded body can be cured to obtain a magnetic core. There are no particular limitations on the curing method; heat treatment can be performed under conditions that allow the resin used to cure.

[0087] In this embodiment, such as Figure 1 As shown, a coil with conductor 5 wound around it is placed inside a mold (not shown), and soft magnetic powder obtained as described above is placed inside the mold as molding powder and compressed to form the coil component 2.

[0088] In this embodiment, using Figure 4 as well as Figure 5A The atomizing device 20 shown can control the distribution of the area envelope of soft magnetic powder by adjusting the amount of molten molten material and the water or air pressure. The reasoning for this is not necessarily clear, but it can be considered, for example, as follows.

[0089] from Figure 5A The water or gas ejected from the first injection hole 27a cuts off the molten metal ejected from the molten metal outlet 23, forming droplets. The water or gas ejected from the second injection hole 27b causes the droplets to contact each other and change shape during solidification, allowing control of the area envelope. Different particle sizes of the powder can be controlled by varying water or gas pressure; higher water or gas pressure results in smaller particle sizes and shape changes. This allows control of the area envelope distribution in the soft magnetic powder. Since the particle size changes with variations in water or gas pressure, by varying the molten liquid volume accordingly to maintain a constant ratio of molten liquid volume to water pressure, a constant particle size can be achieved.

[0090] The soft magnetic powder according to this embodiment can improve core loss.

[0091] The application of the magnetic core in this embodiment is not particularly limited. For example, it can be used as a magnetic core for inductors, especially power inductors. Furthermore, it can also be used in inductors in which the magnetic core and coil are integrally formed.

[0092] Furthermore, magnetic components containing the aforementioned soft magnetic powder can be used as magnetic cores in electronic devices, or as magnetic components other than magnetic cores in other electronic devices. Examples of magnetic components other than magnetic cores include magnetic sheets.

[0093] In particular, because the aforementioned magnetic cores improve core loss, they are suitable for applications requiring miniaturization, high frequency, high efficiency, and energy saving. For example, they are suitable for use in magnetic cores, magnetic components, and electronic devices integrated into ICT equipment, electric vehicles, etc.

[0094] Second Implementation Method

[0095] In this embodiment, the process is the same as described above, except that other soft magnetic metal particles are added to the soft magnetic metal particles 6a of the first embodiment to prepare molding powder, and the molding powder is used to manufacture a magnetic core. It is also possible to mix them with the soft magnetic metal particles 6a of the first embodiment. There are no particular limitations on the other soft magnetic metal particles; the median particle size in the composition and volume metric may be the same or different. Furthermore, the other soft magnetic metal particles do not necessarily have… Figure 6 The relationship shown by the approximate straight lines A1 or A2 can also be... Figure 6 The approximate straight line B1 shown represents the relationship between existing soft magnetic metal particles.

[0096] However, having Figure 6 The soft magnetic metal particles 6a, as shown by the approximate straight lines A1 or A2, preferably comprise 15% or more, 25% or more, 50% or more, or 70% or more by mass relative to the total soft magnetic powder. Alternatively, the soft magnetic metal particles 6a in the cross-sectional view of the magnetic core preferably comprise 3% or more of the total area of ​​the soft magnetic powder. The soft magnetic powder in this embodiment may, for example, be a powder having peaks with two or more particle size distributions.

[0097] In this embodiment, the soft magnetic metal particles can have a single composition or multiple compositions. A particle group is defined as having the same composition, and the soft magnetic metal particles in one or more particle groups only need to have… Figure 6 The approximate straight line relationship A1 or A2 shown is sufficient, but from the viewpoint of improving core loss, it is preferable to have two or more types of soft magnetic metal particles. Figure 6 The relationship between the approximate straight lines A1 and A2 is shown.

[0098] There are no particular restrictions on the composition of soft magnetic metal particles. Examples include pure iron such as carbonyl iron, Fe-Ni alloys, Fe-Si alloys, Fe-Si-Cr alloys, Fe-Si-Al alloys, Fe-Si-Al-Ni alloys, Fe-Ni-Si-Co alloys, Fe-Co alloys, Fe-Co-V alloys, Fe-Co-Si alloys, or Fe-Co-Si-Al alloys, Fe-Si-B alloys, Fe-Si-BC alloys, Fe-Si-BC-Cr alloys, Fe-Nb-B alloys, Fe-Nb-BP alloys, Fe-Nb-B-Si alloys, Fe-Co-PC alloys, Fe-Co-B alloys, Fe-Co-B-Si alloys, Fe-Si-B-Nb-Cu alloys, Fe-Si-B-Nb-P alloys, Fe-Co-BP-Si alloys, Fe-BP-Si-Cu alloys, Fe-Co-BP-Si-Cu alloys, and Fe-Co-BP-Si-Cr alloys.

[0099] In addition, the composition of metallic magnetic particles can be analyzed using, for example, an EDX device or EPMA attached to an electron microscope. Alternatively, 3DAP (three-dimensional atomic probe microanalysis) can also be used to analyze the composition of metallic magnetic particles. When using 3DAP, a small region (e.g., a 20 nm × 100 nm region) can be defined within the metallic magnetic particles to determine the average composition, thus eliminating the influence of resin components in the magnetic core, oxidation of the particle surface, etc., to determine the composition of the particle bulk.

[0100] Furthermore, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the present invention.

[0101] For example, the magnetic core in this embodiment is not limited to a magnetic core with a built-in winding section, but may also be a magnetic core in which a conductor is wound into a coil shape.

[0102] [Example]

[0103] The following description is based on embodiments, but the present invention is not limited to these embodiments.

[0104] Experimental Example 1

[0105] The raw material metal was weighed in an atomic ratio of 57.4Fe-24.6Co-11.0B-5.0P-1.0Si-1.0Cr, and then melted by high-frequency heating to produce a master alloy.

[0106] After heating the prepared master alloy to form a molten metal, in the embodiment, by using... Figure 4 and Figure 5AThe apparatus shown (referred to as "different velocity injection method" in the table) is used for gas atomization to produce soft magnetic powder A for each sample under the conditions shown in Tables 1A and 1B. Here, the orifice diameter D1 of the first injection orifice 27a is 1.2 mm, and the orifice diameter D2 of the second injection orifice is half the orifice diameter D1 of the first injection orifice 27a. Furthermore, the interval W is approximately three-quarters of the orifice diameter D1.

[0107] In addition, in the comparative example, by using Figure 4 and Figure 5B The gas atomization method of the apparatus shown (referred to as "conventional method" in the table) produced soft magnetic powder A for each sample under the conditions shown in Tables 1A and 1B. Here, the gas atomization apparatus used in the comparative examples is as follows: Figure 5B As shown, the diameter of the injection hole 27c is... Figure 5A The first injection hole 27a shown has the same diameter D1 as the others, except that the number of injection holes 27c is adjusted to be the same as the total flow path cross-sectional area of ​​all injection holes 27a and 27b. Figure 5A The devices are the same.

[0108] Next, a resin composite is obtained by mixing the raw material powder of metallic magnetic particles with epoxy resin. More specifically, the soft magnetic powder A prepared by the above method is used in a conventional manner... Figure 4 and Figure 5B The apparatus shown was used to prepare Fe powder (as soft magnetic powder B), which was mixed with epoxy resin to obtain a resin composite. Furthermore, the amount of epoxy resin added to the resin composite (resin amount) was set to 2.6 parts by mass relative to 100 parts by mass of the metallic magnetic particles in any sample of Experimental Example 1. Additionally, soft magnetic powder A and soft magnetic powder B were mixed in any sample of Experimental Example 1 in a mass ratio of "soft magnetic powder A: soft magnetic powder B = 70:30".

[0109] Next, the resin composite is filled into a mold and pressurized to obtain a ring-shaped molded body. The molding pressure is controlled so that the magnetic permeability (μi) of the core is 30. Then, the molded body is heated at 180°C for 60 minutes to cure the epoxy resin in the molded body, thereby obtaining a ring-shaped magnetic core (11 mm outer diameter, 6.5 mm inner diameter, and 2.5 mm thickness).

[0110] In each sample of Experimental Example 1, the fabricated magnetic cores were evaluated as follows.

[0111] Cross-sectional observation of the magnetic core

[0112] The cross-section of the magnetic core was ground using ion milling, and observed using SEM, allowing at least 1000 particles to be observed in one or more fields of view. The SEM was performed with an accelerating voltage of 5kV, a spot intensity of 50, BSE imaging, and a resolution of 2560×1920. Automatic brightness and contrast were also used. Furthermore, the brightness and contrast were adjusted during shooting to ensure that the brightness values ​​(horizontal axis) in the brightness histogram of the captured area were distributed across the entire range.

[0113] During image parsing, Otsu's binarization method is used for image binarization. Otsu's binarization automatically determines the threshold for maximum separation in the brightness histogram. Additionally, to separate contacting particles, the Watershed algorithm is used to define the contact interface, separating and processing each particle individually. The Watershed algorithm is a method for identifying and separating contacting objects.

[0114] The Heywood diameter (area circle equivalent diameter, circle equivalent diameter) of the metallic magnetic particles was determined from cross-sectional images, and surface analysis using EDX was performed to determine the composition of each metallic magnetic particle system. The metallic magnetic particles observed in the cross-section of the magnetic core were classified into powder A and powder B. In the particle size calculation, at least one particle with an area of ​​0.02 μm was considered. 2 Particles with a total pixel count of 300px or more were selected as the measurement targets, and at least 1000 such particles were observed. In each sample of Experiment 1, the median particle size in the volume reference of powder A was approximately 25 μm, and the median particle size in the volume reference of powder B was approximately 0.8 μm. Then, for each of powders A and B, based on the obtained particle size distribution, a first particle group, a second particle group, a third particle group, and a fourth particle group were determined, and data related to particle shape (area envelope) were obtained. The area envelope was calculated using Sklansky's algorithm.

[0115] Then, as Figure 6As shown, an imaginary two-dimensional coordinate system is assumed, with the cumulative frequency in the quantity reference as the horizontal axis and the area envelope as the vertical axis. The relationship between the cumulative frequency and the average area envelope in the quantity reference for each of the first to fourth particle groups is plotted on this imaginary two-dimensional coordinate system. The plotted data is linearly approximated using the least squares method, and the slope of the resulting approximate straight line is taken as *my*. The average area envelope of powder A is 0.891–0.988, and the average roundness is 0.945–0.968. Furthermore, the average area envelope of powder B is confirmed to be 0.971–0.975, and *my* is -0.002–0.003. The results are shown in Tables 1A and 1B. In addition, the slope *my* of the approximate straight line represents the rate of change of area envelope with increasing particle size.

[0116] Core loss

[0117] Core losses of each magnetic core (unit: kW / m) 3 The core loss was measured using a BH analyzer (SY-8218 manufactured by Iwatsu Measurement Co., Ltd.). The magnetic flux density was set to 10 mT and the frequency to 3 MHz when measuring the core loss. The core loss of sample 1 (used as a comparative example) was calculated, and the reduction rate of core loss relative to the comparative example was determined, which was taken as the improvement rate. The results are shown in Table 1A. Additionally, the core loss of sample 19 (used as a comparative example) was calculated, and the reduction rate of core loss relative to the comparative example was determined, which was taken as the improvement rate. The results are shown in Table 1B. In this experiment, a core loss improvement rate of 7.5% or more was considered good, and a rate of 15% or more was considered better.

[0118] [Table 1A]

[0119]

[0120] [Table 1B]

[0121]

[0122] As shown in Tables 1A and 1B, it can be seen that by appropriately controlling the area envelope, the magnetic cores of each embodiment containing soft magnetic powder A with an absolute value of the slope my of the area envelope relative to the cumulative frequency of the soft magnetic powder being 0.005 or more and 0.5 or less, show improved core loss compared to the magnetic cores of the comparative example where the absolute value of my is less than 0.005. Furthermore, it can be seen that when the absolute value of the slope my of the area envelope relative to the cumulative frequency of the soft magnetic powder is 0.010 or more and 0.300 or less, particularly good core loss can be obtained.

[0123] Experimental Example 2A

[0124] For soft magnetic powder A, using from Figure 5A The injection hole 27 shown or Figure 5B The water atomization method shown in the spray orifice 27c, which sprays water instead of inactive gas, was used to prepare powders in the same manner as for test samples 4, 6, 7, 18, and 21 of Experimental Example 1, except that the water pressure was varied. Test samples 25-54 were prepared by controlling the forming pressure to achieve a magnetic permeability of 20, and were evaluated in the same way as in Experimental Example 1. The average area envelope of the soft magnetic powder A was 0.919-0.975. The results are shown in Table 2A.

[0125] Experimental Example 2B

[0126] Except for changing the melt volume and gas pressure to the values ​​listed in Table 2B to adjust the particle size, the powders were prepared in the same manner as those for samples 4, 6, 7, 18, and 21 of Experimental Example 1. Samples were prepared by controlling the forming pressure to achieve a permeability of 20 for the magnetic cores of samples 55-59 and a permeability of 30 for the magnetic cores of samples 60-79, and the same evaluations were performed as in Experimental Example 1. The average area envelope of the soft magnetic powder A was 0.916-0.976. The results are shown in Table 2B.

[0127] [Table 2A]

[0128]

[0129] [Table 2B]

[0130]

[0131] As shown in Tables 2A and 2B, it can be seen that even when the particle size of powder A is varied, the magnetic cores of each embodiment containing soft magnetic powder A with appropriately controlled area envelope show improved core loss compared to the magnetic cores of the comparative examples. As observed in samples 50-59 with a median particle size of approximately 10 μm in the volume reference, it can be seen that even when prepared using either water atomization or gas atomization methods, the magnetic cores of each embodiment containing soft magnetic powder A with appropriately controlled area envelope show improved core loss compared to the magnetic cores of the comparative examples.

[0132] Experimental Example 3

[0133] Regarding the composition of soft magnetic powder A, it was changed to the composition described in Tables 3A to 3F. Otherwise, samples with magnetic core numbers 80 to 349 were prepared in the same manner as samples 4, 6, 7, 18, and 21 of Experimental Example 1, and the same evaluation was performed as in Experimental Example 1. The average area envelope of soft magnetic powder A was 0.924 to 0.973. The results are shown in Tables 3A to 3F.

[0134] [Table 3A]

[0135]

[0136] [Table 3B]

[0137]

[0138] [Table 3C]

[0139]

[0140] [Table 3D]

[0141]

[0142] [Table 3E]

[0143]

[0144] [Table 3F]

[0145]

[0146] As shown in Tables 3A to 3F, it can be seen that even if the composition of the soft magnetic powder A is changed, similar to Experimental Example 1, the magnetic core containing the soft magnetic powder A with appropriately controlled area envelope has improved core loss compared to the magnetic core of the comparative example.

[0147] Experiment Example 4

[0148] For samples 4, 6, 7, 18, and 21 shown in Tables 1A and 1B, the mixing ratio of powder A and powder B was varied as shown in Table 4. Otherwise, samples with magnetic cores numbered 350–359 were prepared in the same manner as samples 4, 6, 7, 18, and 21, and evaluated in the same way as in Experimental Example 1. The average area envelope of the soft magnetic powder A was 0.925–0.978. The results are shown in Table 4.

[0149] [Table 4]

[0150]

[0151] As shown in Table 4, it can be seen that even when the mixing ratio of powder A and powder B is varied, the magnetic cores of each embodiment containing soft magnetic powder A with appropriately controlled area envelope have improved core loss compared to the magnetic cores of the comparative examples.

[0152] Experimental Example 5

[0153] For soft magnetic powder B, the median particle size in the volume reference was changed to the value recorded in Table 5. Otherwise, samples with magnetic cores numbered 360 to 369 were prepared in the same manner as samples 4, 6, 7, 18, and 21, and evaluated in the same way as in Experimental Example 1. The average area envelope of soft magnetic powder A was 0.925 to 0.978. The results are shown in Table 5.

[0154] [Table 5]

[0155]

[0156] As shown in Table 5, it can be seen that even when the particle size of powder B is varied, the magnetic cores of each embodiment containing soft magnetic powder A with appropriately controlled area envelope have improved core loss compared to the magnetic cores of the comparative examples.

[0157] Experimental Example 6

[0158] The composition of the soft magnetic powder B was changed to that shown in Table 6. Otherwise, samples of magnetic cores numbered 370-389 were prepared in the same manner as samples 4, 6, 7, 18, and 21 of Experimental Example 1, and the same evaluation was performed as in Experimental Example 1. The average area envelope of the soft magnetic powder A was 0.924-0.978. The results are shown in Table 6.

[0159] [Table 6]

[0160]

[0161] As shown in Table 6, it can be seen that even if the composition of the soft magnetic powder B is changed, just like in Experimental Example 1, the magnetic core containing the soft magnetic powder A with the area envelope properly controlled improves the core loss compared to the magnetic core of the comparative example.

[0162] Experimental Example 7

[0163] For the soft magnetic powder A manufactured under the same conditions as samples 4, 6, 7, 18 and 21 of Experimental Example 1, the existing method was additionally used. Figure 4 and Figure 5BThe apparatus shown was used to prepare soft magnetic powders B and C. The mixing ratios of soft magnetic powders A, B, and C were varied as shown in Table 7. In addition, samples with magnetic core numbers 390-399 were prepared in the same manner as samples 4, 6, 7, 18, and 21, and evaluated in the same way as in Experimental Example 1. Here, the average area envelope of soft magnetic powder A was 0.925-0.973, and the average roundness was 0.943-0.967. Soft magnetic powder B was composed of Fe, with a median particle size of approximately 0.8 μm in volumetric reference, an average area envelope of 0.970-0.974, and a my value of -0.002-0.002. Soft magnetic powder C was composed of Fe-Ni, with a median particle size of approximately 3 μm in volumetric reference, an average area envelope of 0.972-0.975, and a my value of -0.003-0.002. The results are shown in Table 7.

[0164] [Table 7]

[0165]

[0166] As shown in Table 7, it can be seen that even when the mixing ratio of powder A, powder B and powder C is varied, the magnetic cores of each embodiment with appropriate control of the area envelope of powder A have improved core loss compared with the magnetic cores of the comparative examples.

[0167] Experimental Example 8

[0168] For soft magnetic powder C, the median particle size in the volume reference was changed to the value recorded in Table 8. Otherwise, samples with magnetic cores numbered 400-414 were prepared in the same manner as samples 395-399, and the same evaluation as in Experimental Example 1 was performed. The average area envelope of soft magnetic powder A was 0.927-0.973. The results are shown in Table 8.

[0169] [Table 8]

[0170]

[0171] As shown in Table 8, it can be seen that even when the particle size of powder C is varied, the core containing soft magnetic powder A with appropriately controlled area envelope has improved core loss compared to the core of the comparative example.

[0172] Experimental Example 9

[0173] Regarding the composition of the soft magnetic powder C, it was changed to the composition described in Tables 9A and 9B. Otherwise, magnetic cores numbered 415-464 were prepared in the same manner as those for test samples 395-399 in Experimental Example 7, and the same evaluation was performed as in Experimental Example 7. The average area envelope of the soft magnetic powder A was 0.924-0.973. The results are shown in Tables 9A and 9B.

[0174] [Table 9A]

[0175]

[0176] [Table 9B]

[0177]

[0178] As shown in Tables 9A and 9B, it can be seen that even if the composition of the soft magnetic powder C is changed, similar to Experimental Example 1, the magnetic core containing the soft magnetic powder A with appropriately controlled area envelope improves the core loss compared to the magnetic core of the comparative example.

[0179] Experimental Example 10

[0180] To adjust the area envelope of soft magnetic powder A, the manufacturing conditions of soft magnetic powder A were changed as described in Table 10. To adjust the area envelope of soft magnetic powder B, the manufacturing conditions of soft magnetic powder B were changed as described in Table 10. To adjust the area envelope of soft magnetic powder C, the manufacturing conditions of soft magnetic powder C were changed as described in Table 10. In addition, magnetic cores numbered 465-488 were fabricated in the same manner as samples 395-399 of Experimental Example 7, and the same evaluation was performed. Furthermore, the average area envelope of soft magnetic powder A, fabricated using the conventional method, was 0.971-0.975, and my was -0.002-0.003; the average area envelope of soft magnetic powder B was 0.968-0.973, and my was ~0.003-0.003; and the average area envelope of powder C was 0.969-0.975, and my was -0.003-0.003. Furthermore, the average area envelope of soft magnetic powder A, prepared by heterogeneous flow velocity jetting, was 0.924–0.976, and the average sphericity was 0.945–0.968; the average area envelope of soft magnetic powder B was 0.924–0.975, and the average sphericity was 0.940–0.961; and the average area envelope of soft magnetic powder C was 0.924–0.975, and the average sphericity was 0.939–0.964. The results are shown in Table 10.

[0181] [Table 10]

[0182]

[0183] As shown in Table 10, it can be seen that magnetic cores containing soft magnetic powder A, soft magnetic powder B, or soft magnetic powder C with appropriately controlled area envelope exhibit improved core loss compared to the cores in the comparative examples. Furthermore, it can be seen that magnetic cores containing two types of soft magnetic powders with appropriately controlled area envelope further improve core loss. Additionally, it can be seen that magnetic cores with appropriately controlled area envelope of soft magnetic powders A, B, and C further improve core loss.

[0184] Explanation of reference numerals in the attached figures

[0185] 2…coil components

[0186] 4… Winding section

[0187] 5… conductor

[0188] 6… magnetic core

[0189] 6a… Soft magnetic metal particles

[0190] 6b…resin

[0191] 20…Atomizing device

[0192] 21…molten metal

[0193] 22…Heat-resistant containers

[0194] 23…Molten metal ejection outlet

[0195] 26…spraying device

[0196] 27…Injection Hole

[0197] 27a…First injection hole

[0198] 27b…Second injection hole.

Claims

1. A soft magnetic powder comprising soft magnetic metal particles having a particle size distribution, wherein, Particles representing the first particle group (those with a cumulative frequency of particle size exceeding 30% but less than 40%), the second particle group (those exceeding 50% but less than 60%), the third particle group (those exceeding 70% but less than 80%), and the fourth particle group (those exceeding 90%) are classified into four groups. An imaginary two-dimensional coordinate system is established, with the cumulative frequency of particle size as the horizontal axis and the area envelope as the vertical axis. The relationship between the average cumulative frequency of particle size and the average area envelope of each particle group (from the first to the fourth group) is plotted on this imaginary coordinate system. A linear approximation is applied to the plotted data using the least squares method. The slope of the resulting approximate line is set as *my*. The absolute value of my, |my|, is greater than 0.005 and less than 0.

500.

2. The soft magnetic powder according to claim 1, wherein, The median particle size in the volume reference of the soft magnetic metal particles is greater than 1 μm and less than 50 μm.

3. A magnetic core comprising the soft magnetic powder as described in claim 1 or 2.

4. A magnetic component comprising the soft magnetic powder as described in claim 1 or 2.

5. An electronic device comprising the magnetic component of claim 4.

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