Soft magnetic powder, magnetic core, magnetic components, and electronic equipment

Abstract

To provide a soft magnetic powder that can improve core loss regardless of the composition of the soft magnetic metal particles. [Solution] The relationship between the average of the number-based cumulative frequencies for each of the first to fourth particle groups and the average of the area envelopes for each group is plotted on a virtual two-dimensional coordinate system. The plotted data is linearly approximated using the least squares method, and when the slope of the resulting approximation line is denoted as my, the absolute value of my |my| is between 0.005 and 0.500.

Description

[Technical Field]

[0001] The present invention relates to soft magnetic powder, magnetic core, magnetic component, and electronic equipment. [Background technology]

[0002] Electronic components such as inductors, transformers, and choke coils are widely used in the power supply circuits of various electronic devices. These electronic components consist of a coil and a magnetic core placed inside the coil. In recent years, soft magnetic powder containing soft magnetic metal particles has been widely used as the material for the magnetic core instead of conventional ferrite. This is because soft magnetic metals have a higher saturation magnetization (saturation magnetic flux density) and superior DC superposition characteristics (higher DC superposition current tolerance) compared to ferrite, making them suitable for miniaturizing electronic components (magnetic cores).

[0003] However, when soft magnetic metals are used in a magnetic core, eddy currents are easily generated within the core due to conductivity between multiple soft magnetic metal particles. In other words, when soft magnetic metals are used in a magnetic core, core loss (eddy current loss) is likely to occur. Core loss reduces the efficiency of the power supply circuit and increases the power consumption of electronic devices. Therefore, it is necessary to reduce core loss (see Patent Document 1).

[0004] Conventionally, core loss is generally reduced by controlling the composition of soft magnetic metal particles and the oxide film. However, once the composition of the soft magnetic metal particles is determined, the permeability and DC superposition characteristics are also determined, limiting the design flexibility. Therefore, there is a need to find factors that can reduce core loss independently of the composition of soft magnetic metal particles. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-27327 [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention has been made in view of the above circumstances, and its objective is to provide a soft magnetic powder that can improve core loss regardless of the composition of the soft magnetic metal particles. [Means for solving the problem]

[0007] To achieve the above objective, the soft magnetic powder according to one aspect of the present invention is A soft magnetic powder containing soft magnetic metal particles having a particle size distribution, Among the soft magnetic metal particles, the cumulative frequency based on particle size is, Particles that are between 30% and 40% are designated as the first particle group. Particles that are between 50% and 60% are designated as the second particle group. Particles that are between 70% and 80% are designated as the third particle group. Particles exceeding 90% are designated as the fourth particle group. A virtual two-dimensional coordinate system is set with the cumulative frequency of the soft magnetic metal particles based on the number of particles on the horizontal axis and the area envelope degree of the soft magnetic metal particles on the vertical axis. On the aforementioned virtual two-dimensional coordinate system, the relationship between the average of the number-based cumulative frequencies for each of the first to fourth particle groups and the average of the area envelopes for each group is plotted. When the plotted data is linearly approximated using the least squares method, and the slope of the resulting approximation line is denoted as my, The absolute value of my, |my|, is between 0.005 and 0.500, preferably between 0.010 and 0. It is 300 or less.

[0008] The inventors diligently studied soft magnetic powders that can improve core loss regardless of the composition of the soft magnetic metal particles, and as a result found that a soft magnetic powder having the above configuration can improve core loss, thus completing the present invention.

[0009] Preferably, the median diameter of the soft magnetic metal particles in terms of volume is 1 μm or more and 50 μm or less, more preferably 2 μm or more and 35 μm or less.

[0010] A magnetic core according to one aspect of the present invention is a magnetic core containing the soft magnetic powder described above.

[0011] A magnetic component according to one aspect of the present invention contains the soft magnetic powder described above.

[0012] An electronic device according to one aspect of the present invention contains the magnetic component described above.

Brief Description of Drawings

[0013] [Figure 1] FIG. 1 is a schematic cross-sectional view of a coil component having a magnetic core according to an exemplary embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of the magnetic core shown in FIG. 1. [Figure 3] FIG. 3 is a schematic diagram showing a method for calculating the degree of enclosure of magnetic metal particles. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an apparatus for manufacturing the soft magnetic powder according to the embodiment. [Figure 5A] FIG. 5A is a bottom view of the apparatus as viewed from the direction of the arrow along the V-V line shown in FIG. 4. [Figure 5B] FIG. 5B is a bottom view of the apparatus according to the conventional example. [Figure 6A] FIG. 6A is a graph showing the relationship between the cumulative frequency and the area enclosure degree of the soft magnetic powder according to the examples and comparative examples of the present invention.

Modes for Carrying Out the Invention

[0014] Hereinafter, embodiments will be described.

[0015] First Embodiment As shown in FIG. 1, a coil component 2 having a magnetic core 6 as an example of a magnetic component according to the present embodiment has a winding portion (coil) 4 made of a conductor 5 inside the magnetic core 6. An example of an enlarged cross-sectional view of the magnetic core 6 is shown in FIG. 2.

[0016] As shown in FIG. 2, the magnetic core 6 of the present embodiment may contain a resin 6b, and has a configuration in which a soft magnetic powder containing a large number of soft magnetic metal particles 6a is dispersed in the resin 6b. The soft magnetic powder according to the present embodiment may contain soft magnetic metal particles in which single or plural pores are formed.

[0017] There are no particular restrictions on the type and content of the resin 6b. For example, examples of the type of resin include thermosetting resins such as phenol resins and epoxy resins. When the magnetic core 6 contains a resin, the content of the resin 6b in the magnetic core 6 is preferably 1% by mass or more and 5% by mass or less with respect to the soft magnetic alloy.

[0018] The soft magnetic metal particles 6a are preferably composed of a soft magnetic metal (including an alloy) containing Fe or Co.

[0019] The soft magnetic metal according to the present embodiment has a composition 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 g (atomic ratio), and may be a soft magnetic powder, X1 is one or more selected from Co and Ni, X2 is one or more selected from the group consisting of Mn, Ag, Zn, As, Sn, Cu, Bi, N, O, rare earth elements, and platinum group elements, M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W, Al, Ti, and V, α≧0 0≦β≦0.030 0 ≤ a ≤ 0.200 0 ≤ b ≤ 0.250 0 ≤ c ≤ 0.200 0 ≤ d ≤ 0.200 0 ≤ e ≤ 0.130 0 ≤ f ≤ 0.070 0 ≤ g ≤ 0.070 0.600≦1―(a+b+c+d+e+f+g)≦1.000 That's fine.

[0020] Furthermore, preferably, 0 ≤ α ≤ 0.800 0 ≤ β ≤ 0.030 0 ≤ a ≤ 0.140 0.02 ≤ b ≤ 0.200 0 ≤ c ≤ 0.100 0 ≤ d ≤ 0.130 0 ≤ e ≤ 0.110 0 ≤ f ≤ 0.050 0 ≤ g ≤ 0.050 0.650≦1―(a+b+c+d+e+f+g)≦1.000 It is preferable that the following conditions be met.

[0021] By ensuring that the soft magnetic metal particles contained in the soft magnetic powder according to this embodiment satisfy the above composition range, an improvement in core loss can be expected in the magnetic core containing the soft magnetic powder according to this embodiment.

[0022] The soft magnetic metal particles contained in the soft magnetic powder according to this embodiment may contain elements other than those mentioned above, i.e., elements other than Fe, X1, X2, M, B, P, Si, Cr, C, and S, as unavoidable impurities. For example, they may contain 1% by mass or less per 100% by mass of soft magnetic metal (including alloys).

[0023] The median diameter of the soft magnetic metal particles contained in the soft magnetic powder according to this embodiment is not particularly limited by volume, but is preferably 1 μm to 50 μm, and more preferably 2 μm to 35 μm, in terms of area circle equivalent diameter. Hereinafter, the area circle equivalent diameter may simply be referred to as the circle equivalent diameter. The area circle equivalent diameter may also be referred to as the Heywood diameter.

[0024] There are no particular restrictions on the microstructure of the soft magnetic metal particles contained in the soft magnetic powder according to this embodiment, but it is preferable that they have an amorphous structure, a heteroamorphous structure, or a nanocrystalline structure. This is because it is easier to improve core loss in a magnetic core using the soft magnetic powder according to this embodiment.

[0025] In this embodiment, an amorphous structure refers to a structure in which the amorphous ratio X is 85% or more and no crystals are observed. A heteroamorphous structure refers to a structure in which the amorphous ratio X is 85% or more and crystals exist within the amorphous material. A nanocrystalline structure refers to a structure in which the amorphous ratio X is less than 85% and the average crystal grain size is 100 nm or less. A crystalline structure refers to a structure in which the amorphous ratio X is less than 85% and the average crystal grain size is greater than 100 nm.

[0026] When the soft magnetic powder according to this embodiment has a heteroamorphous structure, it is preferable that the average crystal grain size is 0.1 nm or more and 10 nm or less. When the soft magnetic powder according to this embodiment has a nanocrystalline structure, it is preferable that the average crystal grain size is 3 nm or more and 50 nm or less.

[0027] There are no particular restrictions on the method for evaluating the amorphousness rate X. It may be measured by EBSD (electron beam scanning) or electron diffraction. XRD (X-ray diffraction) can also be used.

[0028] The following describes a method for evaluating the amorphousness using XRD. There are no particular restrictions on the method for evaluating the average grain size; it can be evaluated using commonly used methods such as TEM observation or the Scherrer method using XRD.

[0029] When evaluating the amorphousness rate X by XRD, the amorphousness rate X is calculated using the following formula (1). X = 100 - (Ic / (Ic + Ia) × 100) ... (1) Ic: Crystalline scattering integrated intensity Ia: Amorphous scattering integral intensity The amorphous fraction X is calculated by performing X-ray crystal structure analysis on the soft magnetic powder using XRD to identify the phase, reading the peaks of the crystallized Fe or compound (Ic: crystalline scattering integral intensity, Ia: amorphous scattering integral intensity), determining the crystallization fraction from the peak intensity, and then calculating it using the above formula (1).

[0030] In this embodiment, as shown in Figure 2, the particle diameter of each particle 6a, the number-based cumulative frequency of the particle diameter, and the area envelope of each particle 6a can be determined by cutting the cross-section of the magnetic core 6 and observing the cross-section. There are no particular restrictions on the method for calculating the particle diameter and area envelope.

[0031] Figure 3 is a diagram illustrating the area envelope degree. To calculate the area envelope degree, for example as shown in Figure 3, first, for each particle 6a, the envelope circumference L surrounding the particle 6a is estimated such that it contacts the convex outer shell of the particle 6a but not the concave outer shell. Sklansky's algorithm, the gift wrapping method, Graham scan, Quickhull, etc., may be used to estimate the envelope circumference L. Next, for each particle 6a, the actual area S1 of the particle 6a and the internal area S2 of the envelope circumference L corresponding to that particle 6a are calculated, and S1 / S2 is calculated to obtain the area envelope degree for each particle 6a. The particle diameter of each particle 6a is determined by the area circle equivalent diameter, as described above.

[0032] For example, particle size and area envelope can be calculated using an analysis program. However, when using an analysis program, parts that are clearly not particles may be mistakenly identified as particles, so such parts should be excluded from the calculation as appropriate. Also, particles that are cut off 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.

[0033] Particle size and area envelope are measured using a particle image analyzer, the Morphologi G3 (Malvern Pa). You may also use (Natural Corporation), and in that case, a similar trend will be observed. The Morphologi G3 is a device that disperses powder with air, projects the shape of individual particles, and can evaluate the resulting projection.

[0034] In this embodiment, for example, among the soft magnetic metal particles 6a observed in cross-section as shown in Figure 2, the cumulative frequency based on the number of particles in terms of particle size is, Particles that are between 30% and 40% are designated as the first particle group. Particles that are between 50% and 60% are designated as the second particle group. Particles that are between 70% and 80% are designated as the third particle group. Particles exceeding 90% are designated as the fourth particle group, and the following relationship is satisfied.

[0035] As shown in Figure 6A, a virtual two-dimensional coordinate system is set up with the number-based cumulative frequency of soft magnetic metal particles 6a on the horizontal axis and the area envelope degree of soft magnetic metal particles 6a on the vertical axis. On this two-dimensional coordinate system, the relationship between the average number-based cumulative frequency of each particle group from the first to the fourth particle group and the average area envelope degree of each particle group is plotted.

[0036] When the data plotted in this manner is linearly approximated by the least squares method, and the slope of the resulting approximation line is denoted as my, in this embodiment, as shown in approximation line A1 or A2 in Figure 6A, the absolute value of the slope my of the approximation line, |my|, is 0.005 or more and 0.500 or less, preferably 0.010 or more and 0.300 or less. In contrast, in conventional soft magnetic powders with soft magnetic metal particles, as shown in approximation line B1 in Figure 6A, the absolute value of the slope my of the approximation line, |my|, is 0 or more and less than 0.005.

[0037] In a magnetic core where soft magnetic powder having soft magnetic metal particles 6a of this embodiment having such a relationship is observed, core loss can be improved regardless of the composition of the soft magnetic metal particles.

[0038] The following describes a method for manufacturing a coil component 2 having soft magnetic powder according to this embodiment.

[0039] First, the soft magnetic powder according to this embodiment is manufactured. There are no particular limitations on the method for manufacturing the soft magnetic powder according to this embodiment. The soft magnetic metal powder according to this embodiment can be manufactured by methods such as water atomization, gas atomization, or spray pyrolysis. Alternatively, the soft magnetic metal powder can be manufactured by crushing a metal ribbon, for example. Preferably, the soft magnetic powder is produced by water atomization or gas atomization using the atomization apparatus 20 shown in Figures 4 and 5A. By using the atomization apparatus 20 and controlling the amount of molten metal and the water pressure (or gas pressure), the soft magnetic metal particles 6a of this embodiment, in which the relationship between the cumulative frequency based on the number of particles and the area envelope is controlled, can be easily obtained.

[0040] As shown in Figure 4, the atomizing device 20 has a heat-resistant container 22 that holds molten metal 21. A heating coil 24 is arranged around the outer circumference 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 discharge port 23 is formed at the bottom of the container 22, from which the molten metal 21 is discharged as dripping molten metal.

[0041] An injection device 26 is positioned on the outer side of the bottom wall of the container 22, surrounding the molten metal discharge port 23. The injection device 26 is equipped with injection holes 27. From the injection holes 27, a high-pressure water stream or high-pressure gas is injected towards the dripping molten metal discharged from the molten metal discharge port 23.

[0042] As shown in Figure 5A, in this embodiment, the plurality of injection holes 27 arranged around the molten metal discharge port 23 have a configuration in which 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 are alternately arranged along the circumferential direction at predetermined intervals W. The number and position of the first injection holes 27a and the second injection holes 27b are not particularly limited.

[0043] 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. The predetermined interval W is not particularly limited, but for example it is at least half the inner diameter D2 of the second injection hole 27b and at least three times the inner diameter D1 of the first injection hole 27a. As shown in Figure 5B, in the conventional injection device 26α, injection holes 27c of the same diameter are arranged at predetermined intervals along the circumferential direction.

[0044] The high-pressure water stream or high-pressure gas is injected at an angle θ1 diagonally downward from the entire circumference of the molten metal discharged from the molten metal discharge port 23, and the dripping molten metal becomes numerous droplets which are carried along the flow of the high-pressure water stream or high-pressure gas toward a cooling device or recovery device located below.

[0045] In this embodiment, the particle size of the soft magnetic metal particles 6a can be adjusted by appropriately changing the atomization conditions. It is also possible to adjust the particle size by adjusting the particle size using dry classification or wet classification. Examples of dry classification methods include sieving classification using a dry sieve and airflow classification. Examples of wet classification methods include classification by wet filter filtration and classification by centrifugal separation.

[0046] The molten metal 21 having the above composition readily oxidizes and forms an oxide film upon brief contact with air. Once an oxide film forms, it becomes difficult to pulverize it. When injecting gas from the injection hole 27, using an inert gas or a reducing gas prevents the formation of an oxide film and allows for easy pulverization. Examples of inert gases include nitrogen gas, argon gas, and helium gas. An example of a reducing gas is ammonia decomposition gas. A high-pressure water stream may also be injected from the injection hole 27.

[0047] The soft magnetic powder consisting of soft magnetic metal particles 6a produced using the injection device 26 shown in Figures 4 and 5A has, for example, the relationship between the approximate lines A1 or A2 shown in Figure 6A, and the absolute value of the slope my of the approximate line |my| is between 0.005 and 0.500, preferably between 0.010 and 0.300. Furthermore, the soft magnetic powder consisting of soft magnetic metal particles produced using the conventional injection device 26α shown in Figure 5B has, for example, the relationship between the approximate line B1 shown in Figure 6A, and the absolute value of the slope my of the approximate line |my| is less than 0.005.

[0048] In this embodiment, a coating layer may be formed on the surface of the soft magnetic metal particles of the soft magnetic powder, with a composition different from that of the soft magnetic particles, or the coating layer may be formed by a coating method. Even if the coating layer is formed on the surface of the soft magnetic metal particles, in this embodiment, for example, the relationship is that of the approximate straight lines A1 or A2 shown in Figure 6A, and the absolute value |my| of the slope my of the approximate straight line satisfies the above-described relationship. Alternatively, the coating layer may be formed on the surface of the soft magnetic metal particles in such a way as to satisfy the above-described relationship.

[0049] A magnetic core can be obtained by molding the soft magnetic powder obtained as described above into a molding powder. There are no particular limitations on the molding method. As an example, a method for obtaining a magnetic core by pressure molding will be described.

[0050] First, the soft magnetic powder and resin are mixed. By mixing with resin, the strength of the molding process is increased. This makes it easier to obtain molded articles. There are no particular restrictions on the type of resin. Examples include phenolic resins and epoxy resins. There are also no particular restrictions on the amount of resin added. When adding resin, it may be added in an amount of 1% to 5% by mass relative to the magnetic powder. In this case, soft magnetic metal powders other than the soft magnetic metal powder according to this embodiment, and / or non-magnetic powders may be added. Modifiers, preservatives, dispersants, etc. may also be added.

[0051] A resin compound is obtained by mixing soft magnetic powder and resin. The resin compound may be a granulated powder. There are no particular restrictions on the granulation method. For example, granulation may be performed using a stirrer. There are no particular restrictions on the particle size of the granulated powder.

[0052] The obtained resin compound is pressure-molded to obtain a molded body. There are no particular restrictions on the molding pressure. Then, the resin contained in the molded body is cured to obtain a magnetic core. There are no particular restrictions on the curing method, and heat treatment may be performed under conditions that can cure the resin used.

[0053] In this embodiment, as shown in Figure 1, a coil with a conductor 5 wound around it is placed inside a mold (not shown), and the soft magnetic powder obtained as described above is placed inside the mold as molding powder and compressed to obtain the coil component 2.

[0054] In this embodiment, the area envelope distribution in the soft magnetic powder can be controlled by adjusting the amount of molten metal and the water pressure or gas pressure using the atomizing device 20 shown in Figures 4 and 5A. The reason for this is not entirely clear, but it can be considered as follows.

[0055] The water or gas injected from the first injection port 27a shown in Figure 5A divides the molten metal discharged from the molten metal discharge port 23 into droplets. The water or gas injected from the second injection port 27b causes contact and shape changes between droplets during solidification, allowing control of the area envelope. The controllable powder particle size differs depending on the water pressure or gas pressure; the higher the water pressure or gas pressure, the smaller the particle size of the powder can be changed. This allows control of the area envelope distribution in soft magnetic powder. Since the particle size also changes with changes in water pressure or gas pressure, the particle size can be kept constant by changing the amount of molten metal according to the water pressure or gas pressure and keeping the ratio of the amount of molten metal to the water pressure constant.

[0056] According to the soft magnetic powder of this embodiment, core loss can be improved.

[0057] There are no particular limitations on the application of the magnetic core of this embodiment. For example, it can be suitably used as a magnetic core for inductors, especially power inductors. Furthermore, it can also be suitably used in inductors in which the magnetic core and coil are integrally molded.

[0058] Furthermore, the magnetic component containing the above-mentioned soft magnetic powder may be suitably used as a magnetic core in electronic devices, or it may be used as a magnetic component other than a magnetic core in other electronic devices. Examples of magnetic components other than magnetic cores include magnetic sheets.

[0059] In particular, because the above-mentioned magnetic core has improved core loss, it is suitable for use in fields where miniaturization, high frequency, high efficiency, and energy saving are required. For example, it can be suitably used in magnetic cores, magnetic components, and electronic devices mounted in ICT equipment and electric vehicles.

[0060] Second Embodiment In this embodiment, the process is the same as in the previously described embodiment, except that a molding powder is prepared by adding other soft magnetic metal particles to the soft magnetic metal particles 6a according to the first embodiment, and a magnetic core is manufactured using the molding powder. These particles may be mixed with the soft magnetic metal particles 6a according to the first embodiment. The other soft magnetic metal particles are not particularly limited, and their composition and median diameter based on volume may be the same or different. Furthermore, the other soft magnetic metal particles do not necessarily have the relationship shown by the approximate straight line A1 or A2 in Figure 6A, but may be conventional soft magnetic metal particles that have the relationship shown by the approximate straight line B1 in Figure 6A.

[0061] However, the soft magnetic metal particles 6a having the relationship shown in the approximate straight lines A1 or A2 in Figure 6A are preferably 15% by mass or more, 25% by mass or more, 50% by mass or more, or 70% by mass or more of the total soft magnetic powder. Alternatively, the soft magnetic metal particles 6a in the cross-sectional view of the magnetic core are preferably 3 area % or more of the total soft magnetic powder. The soft magnetic powder according to this embodiment may be, for example, a powder having two or three or more peaks in its particle size distribution.

[0062] In this embodiment, the soft magnetic metal particles may have a single composition or multiple compositions. It is sufficient if a group of particles with the same composition has a relationship between the approximate straight lines A1 or A2 shown in Figure 6A, where the soft magnetic metal particles of one or more particle groups are related. However, from the viewpoint of improving core loss, it is preferable that two or more particle groups of soft magnetic metal particles have a relationship between the approximate straight lines A1 or A2 shown in Figure 6A.

[0063] The composition of the soft magnetic metal particles is not particularly limited. For example, 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, F Examples include e-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.

[0064] The composition of metallic magnetic particles can be analyzed, for example, using an EDX device attached to an electron microscope or an EPMA device. Alternatively, the composition of metallic magnetic particles may be analyzed using a 3DAP (3D atom probe). When using a 3DAP, a small region (e.g., a 20 nm × 100 nm region) can be set within the metallic magnetic particle being measured to measure the average composition, thereby excluding the effects of resin components contained in the magnetic core and oxidation on the particle surface, and allowing for the determination of the composition of the particle itself.

[0065] It should be noted that the present invention is not limited to the embodiments described above, and can be modified in various ways within the scope of the present invention.

[0066] For example, the magnetic core in this embodiment is not limited to a magnetic core that incorporates a winding section, but may also be a magnetic core in which a conductor is wound in a coil shape. [Examples]

[0067] The present invention will be described below based on examples, but it is not limited to these examples.

[0068] Experimental Example 1 The raw metals were weighed to achieve an atomic ratio of 57.4Fe-24.6Co-11.0B-5.0P-1.0Si-1.0Cr, and the master alloy was prepared by melting them using high-frequency heating.

[0069] After heating the prepared master alloy to a molten state, in the examples, soft magnetic powder A for each sample was prepared by gas atomization using the apparatus shown in Figures 4 and 5A (referred to as the "variable flow rate injection method" in the table) under the conditions shown in Tables 1A and 1B. Here, the hole diameter D1 of the first injection hole 27a was 1.2 mm, and the hole diameter D2 of the second injection hole was half the hole diameter D1 of the first injection hole 27a. The spacing W was approximately 3 / 4 of the hole diameter D1.

[0070] In the comparative example, soft magnetic powder A of each sample was prepared using the gas atomization method with the apparatus shown in Figures 4 and 5B (referred to as the "conventional method" in the table) under the conditions shown in Tables 1A and 1B. Here, the gas atomization apparatus used in the comparative example is the same as the apparatus in Figure 5A, except that the diameter of the injection holes 27c is the same as the diameter D1 of the first injection hole 27a shown in Figure 5A, and the number of injection holes 27c is adjusted so that it is the same as the total flow path cross-sectional area of ​​all injection holes 27a and 27b.

[0071] Next, a resin compound was obtained by kneading the raw material powder of the metal magnetic particles with epoxy resin. More specifically, a resin compound was obtained by mixing soft magnetic powder A, which was prepared by the method described above, Fe powder as soft magnetic powder B, which was prepared using the conventional apparatus shown in Figures 4 and 5B, with epoxy resin. The amount of epoxy resin added to the resin compound (resin amount) was 2.6 parts by mass per 100 parts by mass of metal magnetic particles for all samples in Experimental Example 1. Furthermore, soft magnetic powder A and soft magnetic powder B were blended in a mass ratio of "soft magnetic powder A:soft magnetic powder B = 70:30" for all samples in Experimental Example 1.

[0072] Next, a resin compound was filled into a mold and pressurized to obtain a toroidal molded body. The molding pressure was controlled so that the magnetic permeability (μi) of the magnetic core was 30. Then, the above molded body was heat-treated at 180°C for 60 minutes to cure the epoxy resin inside the molded body, and a toroidal magnetic core (outer diameter 11 mm, inner diameter 6.5 mm, thickness 2.5 mm) was obtained.

[0073] For each sample in Experimental Example 1, the following evaluations were performed on the fabricated magnetic core.

[0074] Cross-sectional observation of the magnetic core Cross-sectional polishing was performed using ion milling, and the cross-section of the magnetic core was observed using a scanning electron microscope (SEM) to allow observation of at least 1000 particles in one or more observation fields. The SEM settings were: acceleration voltage: 5kV, spot intensity: 50, BSE image, resolution: 2560×1920. Auto-brightness and auto-contrast functions were also used. Furthermore, brightness and contrast were adjusted so that the luminance values ​​(horizontal axis) in the luminance histogram of the imaging area were distributed across the entire range.

[0075] For image analysis, Otsu's binarization method was used for image binarization. Otsu's binarization method is a technique that automatically determines the threshold that maximizes the separation in the luminance histogram. In addition, to separate contacting particles, the Watershed algorithm was used to clarify the contact interface, and the images were processed separately for each particle. The Watershed algorithm is a technique for recognizing and separating contacting objects.

[0076] From cross-sectional images, the Heywood diameter (area-equivalent circle diameter, circle-equivalent diameter) of the metallic magnetic particles was measured, and surface analysis using EDX was performed to identify the composition system of each metallic magnetic particle. The metallic magnetic particles observed in the cross-section of the magnetic core were then classified into powder A and powder B. For the calculation of particle size, an area of ​​at least 0.02 μm per particle was required. 2In addition to the above, particles with a total number of pixels per particle of 300px or more were selected for measurement, and at least 1000 target particles were observed. In each sample of Experiment 1, the median diameter based on volume was approximately 25 μm for powder A and approximately 0.8 μm for powder B. For powders A and B, the first, second, third, and fourth particle groups were identified based on the obtained particle size distribution, and data on particle shape (area envelope) was obtained. Sklansky's algorithm was used to calculate the area envelope.

[0077] Subsequently, as shown in Figure 6A, a hypothetical two-dimensional coordinate system was assumed with the cumulative frequency based on particle count on the horizontal axis and the area envelope on the vertical axis. The relationship between the cumulative frequency based on particle count and the average area envelope for each of the first to fourth particle groups was plotted on this hypothetical two-dimensional coordinate system. The plotted data was linearly approximated using the least squares method, and the slope of the resulting approximation line was determined as my. The average area envelope of powder A was 0.891 to 0.988, and the average circularity was 0.945 to 0.968. Furthermore, it was confirmed that the average area envelope of powder B was 0.971 to 0.975, and my was -0.002 to 0.003. The results are shown in Tables 1A and 1B. Note that the slope my of the approximation line indicates the rate of change in area envelope with increasing particle size.

[0078] Koalos Core loss of each magnetic core (unit: kW / m) 3 The core loss was measured using a BH analyzer (Iwatsu Instruments Co., Ltd. SY-8218). 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 No. 1, a comparative example, was calculated, and the reduction rate relative to the core loss of the comparative example was determined and defined as the improvement rate. The results are shown in Table 1A. The core loss of sample No. 19, a comparative example, was also calculated, and the reduction rate relative to the core loss of the comparative example was determined and defined as the improvement rate. The results are shown in Table 1B. In this experiment, a core loss improvement rate of 7.5% or higher was considered good, and an improvement rate of 15% or higher was considered even better.

[0079] [Table 1A]

[0080] [Table 1B]

[0081] As shown in Tables 1A and 1B, it was found that by suitably controlling the area envelope, the magnetic cores of each example containing soft magnetic powder A, where the absolute value of the slope my of the area envelope with respect to the cumulative frequency of the soft magnetic powder is 0.005 or more and 0.5 or less, exhibit 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 was found that particularly good core loss can be obtained when the absolute value of the slope my of the area envelope with respect to the cumulative frequency of the soft magnetic powder is 0.010 or more and 0.300 or less.

[0082] Experimental Example 2A For soft magnetic powder A, the powder was prepared using the water atomization method, in which water was ejected instead of inert gas from the injection hole 27 shown in Figure 5A or the injection hole 27c shown in Figure 5B, and the water pressure was changed, but otherwise the powder was prepared in the same manner as for samples 4, 6, 7, 18, and 21 in Experimental Example 1. For magnetic core samples corresponding to samples 25 to 54, the molding pressure was controlled so that the magnetic permeability of the magnetic core was 20, and the same evaluation as in Experimental Example 1 was performed. The average area envelope of soft magnetic powder A was 0.919 to 0.975. The results are shown in Table 2A.

[0083] Experimental Example 2B The powders were prepared in the same manner as for samples 4, 6, 7, 18, and 21 in Experimental Example 1, except that the amount of molten metal and gas pressure were changed to the values ​​listed in Table 2B to adjust the particle size. The magnetic core samples for samples 55-59 were prepared by controlling the molding pressure so that the magnetic permeability of the magnetic core was 20, and the magnetic core samples for samples 60-79 were prepared so that the magnetic core permeability was 30. The same evaluation as in Experimental Example 1 was performed. The average area envelope of soft magnetic powder A was 0.916-0.976. The results are shown in Table 2B.

[0084] [Table 2A]

[0085] [Table 2B]

[0086] As shown in Tables 2A and 2B, even when the particle size of powder A was changed, the magnetic cores of each example containing soft magnetic powder A with suitably controlled area envelope showed improved core loss compared to the magnetic cores of the comparative examples. As seen in samples 50-59, where the median diameter on a volume basis is approximately 10 μm, the magnetic cores of each example containing soft magnetic powder A with suitably controlled area envelope showed improved core loss compared to the magnetic cores of the comparative examples, regardless of whether they were prepared by the water atomization method or the gas atomization method.

[0087] Experimental Example 3 Except for changing the composition of soft magnetic powder A to match the compositions shown in Tables 3A to 3F, magnetic core samples corresponding to sample numbers 80 to 349 were prepared in the same manner as sample numbers 4, 6, 7, 18, and 21 in Experimental Example 1, and evaluated in the same manner 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.

[0088] [Table 3A]

[0089] [Table 3B]

[0090] [Table 3C]

[0091] [Table 3D]

[0092] [Table 3E]

[0093] [Table 3F]

[0094] As shown in Tables 3A to 3F, even when the composition of soft magnetic powder A is changed, it was found that, similar to Experimental Example 1, the magnetic core containing soft magnetic powder A with suitably controlled area envelope exhibits improved core loss compared to the comparative example's magnetic core.

[0095] Experimental Example 4 For sample numbers 4, 6, 7, 18, and 21 shown in Tables 1A and 1B, magnetic core samples for sample numbers 350-359 were prepared in the same manner as sample numbers 4, 6, 7, 18, and 21, except that the mixing ratio of powder A and powder B was changed as shown in Table 4, and the same evaluation as in Experimental Example 1 was performed. The average area envelope of soft magnetic powder A was 0.925-0.978. The results are shown in Table 4.

[0096] [Table 4]

[0097] As shown in Table 4, even when the mixing ratio of powder A and powder B is changed, the area envelope It was found that the magnetic cores of each embodiment containing soft magnetic powder A, whose degree of magnetic properties is suitably controlled, exhibit improved core loss compared to the magnetic cores of the comparative examples.

[0098] Experimental Example 5 For soft magnetic powder B, magnetic core samples for sample numbers 360-369 were prepared in the same manner as for sample numbers 4, 6, 7, 18, and 21, except that the median diameter on a volume basis was changed to the value shown in Table 5. The same evaluation as in Experimental Example 1 was performed. The average area envelope of soft magnetic powder A was 0.925-0.978. The results are shown in Table 5.

[0099] [Table 5]

[0100] As shown in Table 5, even when the particle size of powder B was changed, the magnetic cores of each example containing soft magnetic powder A with suitably controlled area envelope showed improved core loss compared to the magnetic core of the comparative example.

[0101] Experimental Example 6 Except for changing the composition of soft magnetic powder B to the composition shown in Table 6, magnetic core samples corresponding to sample numbers 370-389 were prepared in the same manner as sample numbers 4, 6, 7, 18, and 21 in Experimental Example 1, and evaluated in the same manner as in Experimental Example 1. The average area envelope of soft magnetic powder A was 0.924-0.978. The results are shown in Table 6.

[0102] [Table 6]

[0103] As shown in Table 6, even when the composition of soft magnetic powder B is changed, it was found that, similar to Experimental Example 1, the magnetic core containing soft magnetic powder A, in which the area envelope degree is suitably controlled, exhibits improved core loss compared to the magnetic core of the comparative example.

[0104] Experimental Example 7 To soft magnetic powder A, which was manufactured under the same conditions as samples 4, 6, 7, 18, and 21 in Experimental Example 1, soft magnetic powders B and C, which were manufactured using the conventional apparatus shown in Figures 4 and 5B, were added. Except for changing the mixing ratio of soft magnetic powders A, B, and C as shown in Table 7, magnetic core samples for samples 390 to 399 were prepared in the same manner as samples 4, 6, 7, 18, and 21, and evaluated in the same manner as in Experimental Example 1. Here, the average area envelope of soft magnetic powder A was 0.925 to 0.973, and the average circularity was 0.943 to 0.967. The composition of soft magnetic powder B was Fe, its median diameter on a volume basis was approximately 0.8 μm, its average area envelope was 0.970 to 0.974, and my was -0.002 to 0.002. Furthermore, the composition of the soft magnetic powder C was Fe-Ni, its volume-based median diameter was approximately 3 μm, its average area envelope was 0.972 to 0.975, and my was -0.003 to 0.002. The results are shown in Table 7.

[0105] [Table 7]

[0106] As shown in Table 7, even when the mixing ratio of powder A, powder B, and powder C was changed, the magnetic cores of each embodiment in which the area envelope of powder A was suitably controlled showed improved core loss compared to the magnetic core of the comparative example.

[0107] Experimental Example 8 For soft magnetic powder C, magnetic core samples were prepared in the same manner as for sample numbers 400-414, except that the median diameter on a volume basis was changed to the value shown in Table 8, and evaluated in the same manner as in Experimental Example 1. The average area envelope of soft magnetic powder A was 0.927-0.973. The results are shown in Table 8.

[0108] [Table 8]

[0109] As shown in Table 8, even when the particle size of powder C was changed, the magnetic core containing soft magnetic powder A with suitably controlled area envelope showed improved core loss compared to the comparative example magnetic core.

[0110] Experimental Example 9 Except for changing the composition of soft magnetic powder C to the compositions shown in Tables 9A and 9B, magnetic cores corresponding to sample numbers 415 to 464 were prepared in the same manner as sample numbers 395 to 399 in Experimental Example 7, and evaluated in the same manner as in Experimental Example 7. The average area envelope of soft magnetic powder A was 0.924 to 0.973. The results are shown in Tables 9A and 9B.

[0111] [Table 9A]

[0112] [Table 9B]

[0113] As shown in Tables 9A and 9B, even when the composition of soft magnetic powder C is changed, it was found that, similar to Experimental Example 1, the magnetic core containing soft magnetic powder A, in which the area envelope degree is suitably controlled, exhibits improved core loss compared to the comparative example's magnetic core.

[0114] Experimental Example 10 Except for the following modifications to adjust the area envelope of soft magnetic powder A, the manufacturing conditions for soft magnetic powder B, and the manufacturing conditions for soft magnetic powder C, which were also modified as described in Table 10, magnetic cores for sample numbers 465-488 were prepared and evaluated in the same manner as sample numbers 395-399 in Experimental Example 7. The average area envelope of soft magnetic powder A prepared using the conventional method was 0.971-0.975, with my being -0.002-0.003; the average area envelope of soft magnetic powder B was 0.968-0.973, with my being -0.003-0.003; and the average area envelope of powder C was 0.969-0.975, with my being -0.003-0.003. Furthermore, the average area envelope of soft magnetic powder A, produced by the differential flow rate injection method, was 0.924-0.976, and the average circularity was 0.945-0.968. The average area envelope of soft magnetic powder B was 0.924-0.975, and the average circularity was 0.940-0.961. The average area envelope of soft magnetic powder C was 0.924-0.975, and the average circularity was 0.939-0.964. The results are shown in Table 10.

[0115] [Table 10]

[0116] As shown in Table 10, magnetic cores containing soft magnetic powder A, soft magnetic powder B, or soft magnetic powder C with suitably controlled area envelope showed improved core loss compared to the comparative example magnetic core. Furthermore, magnetic cores containing two soft magnetic powders with suitably controlled area envelope showed even greater core loss improvement. In addition, magnetic cores in which the area envelopes of soft magnetic powders A, B, and C were suitably controlled showed even greater core loss improvement. [Explanation of symbols]

[0117] 2… Coil components 4… Winding section 5… Conductor 6… Magnetic core 6a… Soft magnetic metal particles 6b…Resin 20… Atomizing device 21… Molten metal 22… Heat-resistant container 23… Molten metal discharge port 26… Injection device 27… Injection hole 27a... 1st injection hole 27b... 2nd injection hole

Claims

1. A soft magnetic powder containing soft magnetic metal particles having a particle size distribution, Among the soft magnetic metal particles, the cumulative frequency based on particle size is, Particles that are between 30% and 40% are designated as the first particle group. Particles that are between 50% and 60% are designated as the second particle group. Particles that are between 70% and 80% are designated as the third particle group. Particles exceeding 90% are designated as the fourth particle group. A virtual two-dimensional coordinate system is set with the cumulative frequency of the soft magnetic metal particles based on the number of particles on the horizontal axis and the area envelope degree of the soft magnetic metal particles on the vertical axis. On the aforementioned virtual two-dimensional coordinate system, the relationship between the average of the number-based cumulative frequencies for each of the first to fourth particle groups and the average of the area envelopes for each group is plotted. When the plotted data is linearly approximated using the least squares method, and the slope of the resulting approximation line is denoted as my, A soft magnetic powder in which the absolute value of my |my| is between 0.005 and 0.

500.

2. The soft magnetic powder according to claim 1, wherein the median diameter of the soft magnetic metal particles, based on volume, is 1 μm or more and 50 μm or less.

3. A magnetic core comprising the soft magnetic powder according to claim 1 or 2.

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

5. An electronic device comprising the magnetic component described in claim 4.

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