Powder magnetic core and method for manufacturing the same

Abstract

A powder magnetic core (10) includes: a metal magnetic substance powder (11); a binding agent (12) that binds together the particles of the metal magnetic substance powder (11); and an insulating powder (13) provided in the binding agent (12). The insulating powder (13) contains a first insulating powder (13a) and a second insulating powder (13b) which are needle-shaped or tabular. The median diameter D50 of the second insulating powder (13b) is smaller than the median diameter D50 of the first insulting powder (13a).

Description

[Technical Field]

[0001] The present disclosure relates to a powder magnetic core used in an inductor and a method for manufacturing the powder magnetic core. [Background technology]

[0002] Various electronic devices use step-up / step-down circuits for adjusting the power supply voltage as their drive circuits, DC / DC converter circuits, etc. These circuits use inductors such as choke coils and transformers.

[0003] Conventionally, inductors that use a powder magnetic core manufactured by compression molding a composite magnetic material obtained by mixing a metal magnetic powder and a thermosetting resin have been known due to their superior DC bias characteristics, etc. For example, Patent Document 1 discloses a magnetic element (i.e., the above-mentioned inductor) in which a coil is embedded in the above-mentioned powder magnetic core. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-305108 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in response to the recent growing demand for smaller electronic devices and higher performance, there is room for improvement in the performance of the above-mentioned conventional magnetic elements as powder magnetic cores. In view of the above, an object of the present disclosure is to provide a powder magnetic core with higher performance. [Means for solving the problem]

[0006] A powder magnetic core according to one embodiment of the present disclosure includes a metal magnetic powder, a binder that binds particles of the metal magnetic powder together, and an insulating powder provided in the binder, wherein the insulating powder includes a first insulating powder and a second insulating powder that have an acicular or plate-like shape, and the median diameter D50 of the second insulating powder is smaller than the median diameter D50 of the first insulating powder. The material of the first insulating powder and the second insulating powder is talc.

[0007] A method for producing a powder magnetic core according to one aspect of the present disclosure includes a first step of mixing a metal magnetic powder and an insulating powder, a second step of adding a thermosetting resin to the metal magnetic powder and the insulating powder and mixing them after the first step, and a third step of pressure-molding the mixture produced in the second step, wherein in the first step, the insulating powder includes a first insulating powder and a second insulating powder having an acicular or plate-like shape, and the median diameter D50 of the second insulating powder is smaller than the median diameter D50 of the first insulating powder. The material of the first insulating powder and the second insulating powder is talc. [Effects of the Invention]

[0008] According to the present disclosure, a powder magnetic core and the like with higher performance are provided. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic perspective view showing the configuration of an electrical component including a powder magnetic core according to an embodiment. [Figure 2] FIG. 2 is a diagram schematically showing a cross section of a powder magnetic core according to an embodiment. [Figure 3] FIG. 3 is a flowchart showing a method for manufacturing a powder magnetic core according to an embodiment. [Figure 4] FIG. 4 is a diagram showing the evaluation results of the powder magnetic cores of the comparative examples. [Figure 5] FIG. 5 shows an SEM image and a BSE image of the powder magnetic core of Sample No. 3, which is a comparative example. [Figure 6] FIG. 6 shows an SEM image and a BSE image of the powder magnetic core of Sample No. 8, which is a comparative example. [Figure 7] FIG. 7 is a diagram showing the evaluation results of the powder magnetic cores of the examples and the comparative examples. [Figure 8] FIG. 8 shows an SEM image and a BSE image of the powder magnetic core of Sample No. 17, which is an example. [Figure 9A] FIG. 9A is a diagram showing the results of elemental analysis of the dust core of Sample No. 3. [Figure 9B] FIG. 9B is a diagram showing the amount of Mg element detected at each measurement point in the dust core of Sample No. 3. [Figure 10A] FIG. 10A is a diagram showing the results of elemental analysis of the dust core of Sample No. 8. [Figure 10B] FIG. 10B is a diagram showing the amount of Mg element detected at each measurement point in the dust core of Sample No. 8. [Figure 11A] FIG. 11A is a diagram showing the results of elemental analysis of the powder magnetic core of Sample No. 17. [Figure 11B] FIG. 11B is a diagram showing the amount of Mg element detected at each measurement point in the dust core of Sample No. 17. [Figure 12] FIG. 12 is a diagram showing the evaluation results of powder magnetic cores of other examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] (Knowledge that led to disclosure) Powder magnetic cores are produced by adding insulating powder to metal magnetic powder to obtain insulation between the metal magnetic powder particles, and then adding a thermosetting resin material to bind them together, followed by pressure molding. To improve the magnetic properties of powder magnetic cores, it is important to reduce the distance between the particles of the metal magnetic powder. In other words, it is important to pack the metal magnetic powder densely.

[0011] One of the measures to achieve this is to reduce the amount of resin material and insulating powder added, which reduces the amount of resin material and insulating powder distributed between particles of the metal magnetic powder, improves the packing density of the metal magnetic powder, and results in a dust core with high magnetic permeability.

[0012] However, reducing the amount of insulating powder added reduces the voltage at which dielectric breakdown occurs between particles of the metal magnetic powder. In other words, the withstand voltage performance of the powder magnetic core decreases as the amount of insulating powder added decreases. That is, such a powder magnetic core exhibits high magnetic permeability but has low withstand voltage performance. On the other hand, increasing the amount of insulating powder added leads to a decrease in magnetic permeability. Thus, there is a trade-off between the magnetic permeability and withstand voltage of a powder magnetic core.

[0013] The insulating powder mixed with the metal magnetic powder of the present disclosure includes a first insulating powder having an acicular or plate-like shape and a second insulating powder having an acicular or plate-like shape, and is characterized in that the median diameter D50 of the second insulating powder is smaller than the median diameter D50 of the first insulating powder. This provides a powder magnetic core that can advantageously achieve both high magnetic permeability and high voltage resistance without relying on the trade-off relationship described above.

[0014] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0015] Note that the embodiments described below each illustrate a specific example of the present disclosure. The numerical values, shapes, materials, components, component placement positions, connection configurations, steps, and step sequences shown in the following embodiments are examples and are not intended to limit the present disclosure. Furthermore, among the components in the following embodiments, components that are not recited in independent claims are described as optional components.

[0016] (Embodiment) [composition] First, an electrical component as an example of use of a powder magnetic core according to an embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. FIG.

[0017] Fig. 1 is a schematic perspective view showing the configuration of an electrical component including a powder magnetic core according to an embodiment. Fig. 1 shows the general shape of a powder magnetic core 10, which will be described later, and further shows a see-through view of the interior of the powder magnetic core 10. For example, components such as a coil member 40 that are hidden by being embedded in the powder magnetic core 10 are shown with dashed lines, indicating that they can be seen through the powder magnetic core 10.

[0018] As shown in FIG. 1, the electrical component 100 includes a powder magnetic core 10, a coil member 40, a first terminal member 25, and a second terminal member .

[0019] As an example, the electrical component 100 is a rectangular parallelepiped inductor, and the approximate outer shape is determined by the shape of the powder core 10. The powder core 10 can be formed into any shape by pressure molding. In other words, the shape of the powder core 10 during pressure molding can be used to realize the electrical component 100 in any shape.

[0020] The electric component 100 is a passive element that stores electric energy flowing between the first terminal member 25 and the second terminal member 35 as magnetic energy using the coil member 40. In this embodiment, the electric component 100 is described as one example of use of the powder magnetic core 10, but the powder magnetic core 10 can be used simply as a magnetic material, and the use example is not limited to the electric component 100 of this embodiment. The powder magnetic core 10 may be used in any desired application that can utilize the properties of a magnetic material that combines high magnetic properties (specifically, high magnetic permeability) and high strength.

[0021] The powder magnetic core 10 has rectangular opposing surfaces on which the first terminal member 25 and the second terminal member 35 are respectively formed, and has a substantially square prism shape in which the four sides of each opposing surface are connected by a top surface, a bottom surface, and two side surfaces. In this embodiment, the bottom surface and the top surface are rectangular with dimensions of 14.0 mm × 12.5 mm, and the distance from the bottom surface to the top surface is 8.0 mm.

[0022] FIG. 2 is a diagram schematically showing a cross section of the powder magnetic core 10. As shown in FIG.

[0023] As shown in FIG. 2, the powder core 10 includes a metal magnetic powder 11, a binder 12 that binds the particles of the metal magnetic powder 11 together, and an insulating powder 13 provided in the binder 12.

[0024] Metal magnetic powders such as Fe-Si-Al, Fe-Si, Fe-Si-Cr, or Fe-Si-Cr-B are used as the metal magnetic powder 11. The metal magnetic powder 11 has a higher saturation magnetic flux density than magnetic powders such as ferrite, and is therefore useful for use under large currents.

[0025] For example, when using an Fe-Si-Al-based metal magnetic powder, the composition elements are 8% by weight or more and 12% by weight or less of Si, 4% by weight or more and 6% by weight or less of Al, and the remaining composition elements are Fe and unavoidable impurities. Here, examples of unavoidable impurities include Mn, Ni, P, S, and C. By setting the contents of the composition elements that make up the metal magnetic powder 11 within the above composition ranges, high magnetic permeability and low coercive force can be obtained.

[0026] For example, when using an Fe-Si based metal magnetic powder, the composition elements include Si with a content of 1% by weight or more and 8% by weight or less, and the remaining composition elements include Fe and unavoidable impurities, which are the same as those described above.

[0027] For example, when Fe-Si-Cr based metal magnetic powder is used, the composition elements are Si in an amount of 1% by weight or more and 8% by weight or less, Cr in an amount of 2% by weight or more and 8% by weight or less, and the remaining composition elements are Fe and unavoidable impurities, which are the same as those described above.

[0028] For example, Fe- Si When using -Cr-B based metal magnetic powder, the composition elements are 1% by weight or more and 8% by weight or less of Si, 2% by weight or more and 8% by weight or less of Cr, and the remaining composition elements are Fe and unavoidable impurities, which are the same as those described above.

[0029] The role of Si in the composition elements of the above-mentioned metal magnetic powder 11 is to reduce magnetic anisotropy and magnetostriction constant, increase electrical resistance, and reduce eddy current loss. By making the Si content in the composition elements 1 wt% or more, it is possible to obtain an effect of improving soft magnetic properties, and by making it 8 wt% or less, it is possible to suppress a decrease in saturation magnetization and thus a decrease in DC bias characteristics.

[0030] Furthermore, the effect of improving weather resistance can be imparted by including Cr in the metal magnetic powder 11. By making the Cr content in the composition elements 2% by weight or more, the weather resistance improvement effect can be obtained, and by making it 8% by weight or less, the deterioration of soft magnetic properties can be suppressed.

[0031] The median diameter D50 of these metal magnetic powders 11 is, for example, 5.0 μm or more and 35 μm or less. From the viewpoint of ensuring voltage resistance performance, it is preferable to configure the metal magnetic powder 11 with a small median diameter D50 in order to alleviate electric field concentration between particles, and by setting the median diameter D50 as described above, a high filling factor can be ensured. Furthermore, by setting the median diameter D50 of the metal magnetic powder 11 to 35 μm or less, core loss can be reduced in the high frequency range, and eddy current loss in particular can be reduced. The median diameter D50 of the metal magnetic powder 11 is the particle diameter when the particle size distribution measured by the laser diffraction scattering method is counted from the smallest particle size and the integrated value reaches 50% of the total.

[0032] The binder 12 is provided so as to cover the periphery of the metal magnetic powder 11. The material of the binder 12 is a thermosetting resin, and is selected from, for example, phenol resin, xylene resin, epoxy resin, polyimide resin, silicone resin, and the like.

[0033] The insulating powder 13 is a substance that acts as an electrical insulator. The insulating powder 13 generally has high heat resistance, and by using it as an electrical insulator, the insulation between the particles of the metal magnetic powder 11 is ensured.

[0034] The insulating powder 13 includes a first insulating powder 13a and a second insulating powder 13b each having a needle-like or plate-like shape. The first insulating powder 13a and the second insulating powder 13b are made of an inorganic material, such as talc (Mg3SiO4). 10 (OH)2).

[0035] The first insulating powder 13a and the second insulating powder 13b are each provided in a binder 12. Therefore, the first insulating powder 13a and the second insulating powder 13b are provided so as to be positioned between particles of the metal magnetic powder 11. The first insulating powder 13a and the second insulating powder 13b may be entirely covered with the binder 12, or part of the periphery may be in contact with the metal magnetic powder 11. Note that the first insulating powder 13a or the second insulating powder 13b does not need to be present in all spaces between the particles of the metal magnetic powder 11.

[0036] The first insulating powder 13a and the second insulating powder 13b have different particle size distributions, so that the particle size distribution of the insulating powder 13 has two different peaks.

[0037] In this embodiment, the median diameter D50 of second insulating powder 13b is smaller than the median diameter D50 of first insulating powder 13a. In other words, the median diameter D50 of first insulating powder 13a is larger than the median diameter D50 of second insulating powder 13b. Note that the median diameter D50 is the particle diameter measured by a particle size distribution meter using a laser diffraction scattering method, counting from the smallest particle size to the largest particle size, and the cumulative value reaches 50% of the total.

[0038] For example, the median diameter D50 of the first insulating powder 13a is 1.40 to 11.67 times the median diameter D50 of the second insulating powder 13b. For example, the median diameter D50 of the first insulating powder 13a is more than 0.11 to 1.14 times the median diameter D50 of the metal magnetic powder 11. More preferably, the median diameter D50 of the first insulating powder 13a is 0.28 to 0.80 times the median diameter D50 of the metal magnetic powder 11. These relationships will be explained in detail later.

[0039] Furthermore, when the median diameter D50 of the first insulating powder 13a is 2.5 μm or more and 7 μm or less, the aspect ratio is preferably 30 / 1 or more. This can improve the flowability of the metal magnetic powder during molding of the powder core. When the median diameter D50 of the second insulating powder 13b is 0.6 μm or more and 1.5 μm or less, the aspect ratio is preferably 20 / 1 or less. This can contribute to the insulation between particles of the metal magnetic powder 11. Note that the aspect ratio here refers to the ratio of the long side to the short side of an acicular or plate-like shape.

[0040] Continuing with reference to FIG. 1, the coil member 40, the first terminal member 25, and the second terminal member 35 will be described.

[0041] The coil member 40 is wound with a conductor wire, which is a long conductor coated with an insulating film (winding portion), and both ends of the conductor wire are connected to the first terminal member 25 and the second terminal member 35, respectively (lead portions 20 and 30). diameterIn this example, a round conductor wire with a diameter of 0.65 mm is used. The thickness and shape of the conductor wire are not particularly limited; any round conductor wire or rectangular conductor wire can be used as long as it is thick enough to be wound. The winding portion is embedded near the center of the powder magnetic core 10. In the lead portions 20 and 30, both ends of the conductor wire extend continuously from the winding portion to the opposing surfaces, protruding outward from the powder magnetic core 10. A portion of the lead portion is flattened and bent to fit along the opposing surfaces and the bottom. The insulating film covering is removed from the extended portions, allowing electrical connection to the outside.

[0042] The first terminal member 25 and the second terminal member 35 are made of a conductive plate such as phosphor bronze or copper. Each of the first terminal member 25 and the second terminal member 35 has a recess near the center along the opposing surface and is configured to recess into the powder core 10. The lead portions 20 and 30 are disposed outside this recess, and are electrically connected to the first terminal member 25 and the second terminal member 35. The lead portions 20 and 30 are connected to the first terminal member 25 and the second terminal member 35 by resistance welding or the like. The first terminal member 25 and the second terminal member 35 are bent so as to be inserted toward the inside of the powder core 10, and the first terminal member 25 and the second terminal member 35 are fixed to the powder core 10 with the bent portions inserted into the powder core 10.

[0043] Additionally, the first terminal member 25 and the second terminal member 35 are bent together with the lead portions 20 and 30 so as to fit along the bottom surface of the powder magnetic core 10. As a result, the lead portions 20 and 30 are held by the first terminal member 25 and the second terminal member 35 and routed around the underside of the bottom of the electrical component 100. In other words, the lead portions 20 and 30 can be directly connected to lands (not shown) of a mounting board or the like on which the electrical component 100 is mounted.

[0044] The first terminal member 25 and the second terminal member 35 are not essential components. If the lead portions 20 and 30 have the strength to maintain their shape independently, the first terminal member 25 and the second terminal member 35 do not have to be provided.

[0045] As described above, the powder core 10 of this embodiment includes metal magnetic powder 11, binder 12 that binds particles of the metal magnetic powder 11 together, and insulating powder 13 provided in the binder 12. The insulating powder 13 includes first insulating powder 13a and second insulating powder 13b that have an acicular or plate-like shape, and the median diameter D50 of the second insulating powder 13b is smaller than the median diameter D50 of the first insulating powder 13a.

[0046] This configuration allows the first insulating powder 13a, which has a large median diameter D50, to be provided between particles of the metal magnetic powder 11. This allows the spacing between particles to be widened in the region where the first insulating powder 13a is provided, thereby increasing the withstand voltage of the powder core 10. Furthermore, the second insulating powder 13b, which has a small median diameter D50, can be provided between particles of the metal magnetic powder 11 in a region other than the region where the first insulating powder 13a is provided. This allows the spacing between particles to be narrowed in the other region, preventing it from widening, thereby preventing a decrease in the magnetic permeability of the powder core 10. These features allow the powder core 10 to have high performance.

[0047] [Manufacturing method] Next, a method for manufacturing the above-mentioned powder magnetic core 10 will be described with reference to FIG.

[0048] FIG. 3 is a flowchart showing a method for manufacturing a powder magnetic core according to an embodiment.

[0049] In the manufacturing of the dust core 10 in this embodiment, first, metal magnetic powder 11 containing predetermined composition elements is prepared (step S101).

[0050] Next, the metal magnetic powder 11 is mixed with an electrical insulating material made of insulating powder 13 (first step S102). The insulating powder 13 includes two types of powder: first insulating powder 13a and second insulating powder 13b. The median diameter D50 of the second insulating powder 13b is smaller than the median diameter D50 of the first insulating powder 13a. The weight of the first insulating powder 13a in the insulating powder 13 is, for example, 0.2 to 0.9 times the total weight of the first insulating powder 13a and the second insulating powder 13b.

[0051] In a state where the metal magnetic powder 11 and the electrical insulating material are dispersed substantially uniformly by the above-mentioned mixing, a thermosetting resin as the binder 12 is added, and further mixing is carried out (second step S103).

[0052] In the second step S103, a silicone resin, which is a thermosetting resin, is dissolved in a solvent such as IPA (Isopropyl Alcohol) in advance and then added to the mixture of the metal magnetic powder 11 and the electrical insulating material, followed by mixing (kneading). Kneading of the thermosetting resin is carried out by mixing the uncured resin material in a mortar, mixer, ball mill, V-type mixer, cross rotary, or the like.

[0053] The mixture thus mixed is heated at a temperature of 65°C or higher and 150°C or lower to evaporate the solvent, and then pulverized to obtain a composite magnetic material with good moldability. Furthermore, by classifying this composite magnetic material to obtain a mixed powder with particle sizes within a predetermined range, moldability can be further improved.

[0054] The mixed powder obtained as described above is put into a mold and pressure-molded into a desired shape to obtain the powder core 10 (third step S104). In the third step S104, a pressure of 3 to 7 ton / cm is applied. 2 Pressure molding is performed within the range.

[0055] These steps S101 to S104 produce powder magnetic core 10. The produced powder magnetic core 10 is used as part of an electrical component 100 in which a coil is embedded.

[0056] Comparative Examples and Examples Examples of the powder magnetic core based on the above embodiment and comparative examples will be described.

[0057] In the comparative examples and examples, Fe-Si-Cr-based metal magnetic powder was used as the metal magnetic powder. The median diameter D50 of the metal magnetic powder was 8.8 μm. A silicone resin, which is a thermosetting resin, was used as the binder. The amount of silicone resin added was 3.0 parts by weight per 100 parts by weight of the metal magnetic powder. Talc was used as the material for the first insulating powder and the second insulating powder in the insulating powder. Using these materials, a mixture of metal magnetic powder, thermosetting resin, and insulating powder was prepared.

[0058] The mixture was heated to 4 ton / cm at room temperature. 2 The powder magnetic core was then produced by drying at a temperature of 150°C for 2 hours to harden the thermosetting resin.

[0059] The mixture was heated to 4 ton / cm at room temperature. 2 The powder magnetic core was then produced by drying at 150°C for 2 hours to harden the thermosetting resin.

[0060] [Method of calculating magnetic permeability] The magnetic permeability was determined by measuring the inductance L at 0 A using an LCR meter for electrical components produced using each powder magnetic core, and calculating the initial magnetic permeability μi using the following equation 1 (measurement frequency: 100 kHz).

[0061] μi=(L×le) / (μ0×Ae×n 2 ) ···(1)

[0062] Here, le is the effective magnetic path length, μ0 is the magnetic permeability of a vacuum, Ae is the cross-sectional area, and n is the number of turns of the measuring coil.

[0063] [Evaluation method for withstand voltage] To measure the withstand voltage value, the produced compact was sandwiched between conductive rubber placed on both main surfaces, and an initial DC voltage of 10 V was applied. The applied voltage value was then continuously increased at a rate of 5 V / min. The applied voltage value just before breakdown occurred was divided by the thickness of the compact (V / mm), and this was taken as the withstand voltage value of each powder magnetic core.

[0064] [Evaluation indicators] The evaluation index for the powder magnetic core was a value expressed as "magnetic permeability x voltage resistance." A larger value indicates that the powder magnetic core has an excellent balance of magnetic permeability and voltage resistance.

[0065] [Evaluation results of magnetic permeability and withstand voltage] First, the powder magnetic core of the comparative example will be described with reference to FIGS.

[0066] The powder magnetic core of the comparative example was composed of one type of insulating powder. In the comparative example, the amount of silicone resin added was 3.0 parts by weight per 100 parts by weight of the metal magnetic powder.

[0067] Fig. 4 shows the evaluation results of the powder magnetic cores of the comparative examples, including the sample number of the powder magnetic core, the median diameter D50 of the insulating powder, the ratio of the median diameters D50 of the insulating powder and the metal magnetic powder, the amount of insulating powder added, the magnetic permeability, the withstand voltage, and "magnetic permeability x withstand voltage."

[0068] 4, in the powder magnetic core of the comparative example, the smaller the median diameter D50 of the insulating powder, the higher the magnetic permeability and the lower the withstand voltage. In other words, the larger the median diameter D50 of the insulating powder, the lower the magnetic permeability and the higher the withstand voltage.

[0069] Fig. 5 shows a scanning electron microscope (SEM) image and a backscattered electron (BSE) image of the powder magnetic core of comparative example Sample No. 3. Fig. 5 also shows 20 measurement points, which will be described later.

[0070] FIG. 5(a) shows an SEM image, and FIG. 5(b) shows a BSE image of the same cross section as FIG. 5(a). The white areas in the BSE image of FIG. 5(b) are areas where talc, an insulating powder, is present. The black areas in the BSE image are areas where metal magnetic powder and thermosetting resin, a binder, are present. BSE White areas in the image are represented as yellow in the actual image.

[0071] As shown in Figure 5, for sample No. 3, the white areas in the BSE image are locally agglomerated and large. This is thought to be because insulating powder with a large median diameter D50 is present between the particles of the metal magnetic powder, widening the spaces between the particles. As a result, sample No. 3 exhibits a high withstand voltage of 245 V / mm, but a low magnetic permeability of 19.5.

[0072] Fig. 6 shows an SEM image and a BSE image of the powder magnetic core of comparative example Sample No. 8. Note that Fig. 6 also shows 20 measurement points, which will be described later.

[0073] Figure 6(a) shows an SEM image, and Figure 6(b) shows a BSE image of the same cross section as (a). As shown in Figure 6(b), white areas in the BSE image of Sample No. 8 are scattered throughout the sample, and the white areas are small. This is thought to be due to the presence of insulating powder with a small median diameter D50 between the particles of the metal magnetic powder, narrowing the spacing between the particles. Therefore, Sample No. 8 exhibits a high magnetic permeability of 27.5, but a low withstand voltage of 170 V / mm.

[0074] As described above, in the comparative example, there is a trade-off between magnetic permeability and withstand voltage. In contrast, in the examples described below, the above trade-off is improved compared to the comparative example.

[0075] A dust core 10 of the example will be described with reference to FIGS.

[0076] In the powder core 10 of the example, the insulating powder 13 is composed of two types of insulating powder. In the example, the amount of silicone resin added was 3.0 parts by weight with respect to 100 parts by weight of the metal magnetic powder.

[0077] Fig. 7 shows the evaluation results of the powder magnetic cores of the examples and comparative examples. Fig. 7 shows the sample number of the powder magnetic core, the median diameter D50 etc. of the first insulating powder, the median diameter D50 etc. of the second insulating powder, the ratio of the median diameter D50 of the first insulating powder to the median diameter D50 of the second insulating powder, the magnetic permeability, the withstand voltage, and "magnetic permeability x withstand voltage." In this figure, the sample numbers are arranged in descending order of the median diameter D50 of the first insulating powder.

[0078] The powder magnetic cores 10 of the examples are Samples Nos. 14 to 23, and the powder magnetic cores of the comparative examples are Samples Nos. 1, 3 to 5, 7, 10 to 13, 24, and 25. Note that, since Comparative Samples Nos. 1, 3 to 5, and 7 contain one type of insulating powder, the median diameters D50 of the first insulating powder and the second insulating powder were set to the same value.

[0079] In the following, the "magnetic permeability x withstand voltage (=5095)" of Sample No. 6 as a comparative example will be compared with the "magnetic permeability x withstand voltage" of the example.

[0080] 7, focusing on the median diameters D50 of the first insulating powder and the second insulating powder, in Samples No. 14 to 23 of the example, the median diameter D50 of the second insulating powder 13b is smaller than the median diameter D50 of the first insulating powder 13a. Furthermore, in Samples No. 14 to 23, the median diameter D50 of the first insulating powder 13a is 1.40 to 11.67 times the median diameter D50 of the second insulating powder 13b, and the value of "magnetic permeability × withstand voltage" is larger than that of Sample No. 6 of the comparative example. Therefore, in order to increase the value of "magnetic permeability × withstand voltage," it is desirable to set the median diameter D50 of the first insulating powder 13a to be 1.40 to 11.67 times the median diameter D50 of the second insulating powder 13b.

[0081] Furthermore, when focusing on the median diameter D50 of the first insulating powder 13a and the metal magnetic powder 11, in samples 14 to 23, the median diameter D50 of the first insulating powder 13a is 0.28 to 0.80 times the median diameter D50 of the metal magnetic powder 11, and the value of "magnetic permeability × withstand voltage" is larger than that of comparative sample No. 6. On the other hand, in comparative sample No. 10, the median diameter D50 of the first insulating powder is too large compared to the median diameter D50 of the metal magnetic powder, so the value of "magnetic permeability × withstand voltage" is smaller than that of sample No. 6. Furthermore, in comparative samples Nos. 24 and 25, the median diameter D50 of the first insulating powder is too small compared to the median diameter D50 of the metal magnetic powder, so the value of "magnetic permeability × withstand voltage" is smaller than that of sample No. 6. From these results, it can be seen that the median diameter D50 of the first insulating powder 13a is 0.11 times larger than the median diameter D50 of the metal magnetic powder 11. double Greater than 1.14 double It is believed that when the value is smaller, good results can be obtained in terms of "magnetic permeability x withstand voltage."

[0082] Furthermore, in the examples, as shown in Samples 15 to 17, 19, 20, 22, and 23, when the median diameter D50 of first insulating powder 13a is 2.5 μm or more and 7.0 μm or less and the median diameter D50 of first insulating powder 13a is 2.5 times or more the median diameter D50 of second insulating powder 13b, the value of "magnetic permeability × withstand voltage" is large. Therefore, to further increase the value of "magnetic permeability × withstand voltage," it is desirable to set the median diameter D50 of first insulating powder 13a to 2.5 μm or more and 7.0 μm or less and to set the median diameter D50 of first insulating powder 13a to 2.5 times or more the median diameter D50 of second insulating powder 13b.

[0083] Fig. 8 shows an SEM image and a BSE image of the powder magnetic core 10 of Example Sample No. 17. Note that Fig. 8 also shows 20 measurement points, which will be described later.

[0084] FIG. 8(a) shows an SEM image, and FIG. 8(b) shows a BSE image of the same cross section as (a). As shown in FIG. 8(b), sample No. 17 has both areas where the white regions in the BSE image are larger and areas where the white regions are smaller. This is thought to be because the powder core 10 has areas where the first insulating powder 13a with a large median diameter D50 is provided and areas where the second insulating powder 13b with a small median diameter D50 is provided. As a result, sample No. 17 has both areas where the spacing between particles of the metal magnetic powder is widened and areas where the spacing is narrowed, which is thought to be why the powder core 10 has both excellent magnetic permeability and excellent withstand voltage.

[0085] To confirm this point, the dispersion state of the insulating powder in the dust core will be explained below.

[0086] [Dispersion state of insulating powder in powder magnetic core] The dispersion state of the insulating powder in the dust core will be described with reference to FIGS. 5, 6, 8, and 9A to 11B.

[0087] In this example, the amount of Mg element detected between particles of the metal magnetic powder is examined to determine the dispersion state of the insulating powder. The reason for focusing on the Mg element is that it is not contained in the metal magnetic powder or the binder, but is contained only in the insulating powder. Therefore, elemental analysis of the powder core is performed based on an image of the cross section of the powder core, and the amount of Mg element detected between particles of the metal magnetic powder is examined to determine the dispersion state of the insulating powder.

[0088] First, a comparative example, Sample No. 3, will be described, along with a method for determining the dispersion state of the insulating powder.

[0089] As mentioned above, Fig. 5 shows SEM and BSE images of the powder magnetic core of comparative example Sample No. 3. In Fig. 5, 20 measurement points, which are target regions for elemental analysis, are marked on each of the SEM and BSE images.

[0090] First, we searched for areas where insulating powder (talc) was present between particles of the metal magnetic powder in the SEM and BSE images (white areas in the BSE images), and selected 20 measurement points where Mg elements were predicted to be detected. Figure 5 shows the 20 measurement points consisting of spectrum 1 to spectrum 20.

[0091] The number of measurement points is not limited to 20, and may be any number sufficient to determine the dispersion state of the insulating powder. At each measurement point, the amount of Mg element detected is determined by removing metallic magnetic powder and the like from the detection data, so the measurement points may include black areas. At each measurement point, the amounts of multiple elements detected are expressed as a ratio when performing elemental analysis, so the area of ​​each measurement point may be different.

[0092] Before determining the amount of Mg detected at each measurement point, elemental analysis of the entire BSE image was performed to determine a reference amount of Mg detected. The reference amount of Mg detected is the detection rate of Mg in the remaining area of ​​the entire BSE image excluding the metal magnetic powder, and is used to determine the segregation or dispersion of Mg at each of the 20 measurement points.

[0093] 9A shows the results of elemental analysis of the powder magnetic core of Sample No. 3. Fig. 9A shows that the detected amounts of each element contained in the powder magnetic core of Sample No. 3 were 71.3 mass% Fe, 14.1 mass% C, 5.6 mass% Si, 3.9 mass% O, 3.5 mass% Cr, and 1.4 mass% Mg. These analysis results can be obtained using, for example, an energy dispersive X-ray analyzer.

[0094] Based on the elemental analysis results, the reference detection amount of Mg element between particles of the metal magnetic powder is calculated. For example, if the elements contained in the metal magnetic powder are removed from the multiple elements contained in the powder magnetic core, the elements contained in the thermosetting resin and the insulating powder remain. Therefore, by using the detected amount of Mg element in the elemental analysis results of FIG. 9A as the numerator and the sum of the detected amounts of the multiple elements contained in the thermosetting resin and the insulating powder as the denominator, the reference detection amount of Mg element, which serves as a criterion for judgment, can be calculated.

[0095] Specifically, if the detected amount (mass%) of Mg element in the entire BSE image is y and the detected amount (mass%) of metal magnetic powder in the entire BSE image is z, the reference detected amount R of Mg element can be calculated by the following (Equation 1).

[0096] R=(y / (100-z))×100 (Formula 1)

[0097] By comparing the reference detection amount R obtained above with the detection amount of Mg element at each measurement point, it is determined whether the Mg element is segregated or dispersed at each measurement point. Specifically, taking the detection amount of Mg element at a predetermined measurement point as x, if the detection amount x is greater than the reference detection amount R, it is determined that the Mg element is segregated at the predetermined measurement point, and if the detection amount x is less than the reference detection amount R, it is determined that the Mg element is dispersed at the predetermined measurement point.

[0098] Furthermore, by comprehensively looking at a plurality of measurement points, it is determined whether the insulating powder in the image is not overly clumped or scattered and is appropriately dispersed. In this example, when there are 5 or more measurement points where the Mg element is segregated and 5 or more measurement points where the Mg element is dispersed among 20 measurement points, it is determined that the insulating powder is appropriately dispersed.

[0099] That is, when there are 5 or more measurement points satisfying x > R and 5 or more measurement points satisfying x < R among 20 measurement points, it is determined that the insulating powder is appropriately dispersed in the image. On the other hand, when there are 5 or more measurement points satisfying x > R among 20 measurement points but less than 5 measurement points satisfying x < R, it is determined that the insulating powder is locally overly clumped in the image. Also, when there are 5 or more measurement points satisfying x < R among 20 measurement points but less than 5 measurement points satisfying x > R, it is determined that the insulating powder is overly scattered in the image.

[0100] Using the above determination method, the dispersion state of the insulating powder is determined for the compacted powder core of sample No. 3 in the comparative example.

[0101] In the case of sample No. 3 in the comparative example, the detection amount y of Mg element in the entire BSE image is y = 1.4. Also, the detection amount z of the metal magnetic powder in the entire BSE image is obtained by z = (mass% of Fe element + mass% of Si element + mass% of Cr element), and z = (71.3 + 5.6 + 3.5). Note that the detection amount z also includes the Si element of the silicone resin and the Si element of the insulating powder, although they are in trace amounts.

[0102] When the reference detection amount R1 of the Mg element is calculated based on the detection amount y and the detection amount z in the above (Equation 1), the reference detection amount R1 is the value shown below.

[0103] R1=(1.4 / (100-71.3-5.6-3.5))×100=7.1

[0104] For the powder magnetic core of sample No. 3, the detected amount x of Mg element at each measurement point is compared with the reference detected amount R1 to determine whether the Mg element is segregated or dispersed at each measurement point.

[0105] Figure 9B shows the amount of Mg detected at each measurement point in the powder magnetic core of sample No. 3. Figure 9B shows the amount x of Mg detected at each of the 20 measurement points in mass %. Note that spectra 11, 16, and 17 are included at measurement points to confirm that the amount of Mg detected is 0 mass % in areas that do not include white regions.

[0106] 9B, the detected amount of Mg element in spectrum 1 is 13.7, which is larger than the reference detected amount R1=7.1, so it is determined that Mg element is segregated at the measurement point of spectrum 1. Similarly, segregation and dispersion of Mg element are determined for the measurement points of the other spectra.

[0107] In sample No. 3, the detected amount x of Mg element at 16 of the 20 measurement points was greater than the reference detected amount R1, and it was determined that segregation occurred. In addition, the detected amount x of Mg element at one of the 20 measurement points was smaller than the reference detected amount R1, and it was determined that dispersion occurred. Therefore, overall, it is determined that the insulating powder in the powder magnetic core of sample No. 3 is locally too agglomerated and not properly dispersed.

[0108] Thus, in the powder magnetic core of sample No. 3, the insulating powder is locally too compacted, which is thought to be why, as shown in Figure 4, the withstand voltage is high at 245 V / mm, but the magnetic permeability is low at 19.5.

[0109] Next, Sample No. 8, which is a comparative example, will be described.

[0110] As mentioned above, Fig. 6 shows SEM and BSE images of the powder magnetic core of comparative example Sample No. 8. In Fig. 6, 20 measurement points, which are target regions for elemental analysis, are marked on each of the SEM and BSE images.

[0111] First, we searched for areas where insulating powder (talc) was present between particles of the metal magnetic powder in the SEM and BSE images (white areas in the BSE images), and selected 20 measurement points where Mg elements were predicted to be detected. Figure 6 shows the 20 measurement points consisting of spectrum 1 to spectrum 20.

[0112] Here, before determining the amount of Mg element detected at each measurement point, elemental analysis of the entire BSE image is performed to determine a reference amount of Mg element detected.

[0113] Fig. 10A is a diagram showing the results of elemental analysis of the powder magnetic core of sample No. 8. Fig. 10A shows that the detected amounts of each element contained in the powder magnetic core of sample No. 8 were 75.1 mass% Fe, 11.5 mass% C, 5.2 mass% Si, 3.7 mass% Cr, 3.4 mass% O, and 1.2 mass% Mg.

[0114] In the case of comparative sample No. 8, the detected amount y of Mg element in the entire BSE image is y = 1.2. The detected amount z of the metal magnetic powder in the entire BSE image is calculated as z = (mass % of Fe element + mass % of Si element + mass % of Cr element), which is z = (75.1 + 5.2 + 3.7). Note that the detected amount z also includes trace amounts of Si element from the silicone resin and the insulating powder.

[0115] When the reference detection amount R2 of the Mg element is calculated based on the detection amount y and the detection amount z in the above (Equation 1), the reference detection amount R2 is the value shown below.

[0116] R2=(1.2 / (100-75.1-5.2-3.7))×100=7.5

[0117] For the powder magnetic core of sample No. 8, the detected amount x of Mg element at each measurement point is compared with the reference detected amount R2 to determine whether the Mg element is segregated or dispersed at each measurement point.

[0118] Figure 10B shows the amount of Mg element detected at each measurement point in the powder magnetic core of sample No. 8. Figure 10B shows the amount of Mg element detected x (mass%) for each of the 20 measurement points. Note that spectrum 2 is included at each measurement point to confirm that the amount of Mg element detected is lower in areas with fewer white regions.

[0119] 10B, the detected amount of Mg element in spectrum 1 is 5.4, which is smaller than the reference detected amount R2=7.5, so it is determined that the Mg element is dispersed at the measurement point of spectrum 1. Similarly, segregation and dispersion of Mg element are determined for the measurement points of the other spectra.

[0120] For sample No. 8, of the 20 measurement points, none had a detected amount x of Mg element greater than the reference detected amount R2, and it was determined that there were no segregated measurement points. Furthermore, of the 20 measurement points, 19 had a detected amount x of Mg element less than the reference detected amount R2, and were determined to be dispersed. Therefore, overall, it was determined that the insulating powder in the powder magnetic core of sample No. 8 was too dispersed and not properly dispersed.

[0121] In the dust core of sample No. 8, the insulating powder is too dispersed, which is why, as shown in Figure 4, the magnetic permeability is high at 27.5, but the withstand voltage is low at 170 V / mm.

[0122] Next, Sample No. 17, which is an example, will be described.

[0123] Fig. 8 shows an SEM image and a BSE image of the powder core 10 of Example Sample No. 17. In Fig. 8, 20 measurement points, which are target regions for elemental analysis, are marked on each of the SEM image and the BSE image.

[0124] First, in the SEM image and the BSE image, areas where the insulating powder 13 (talc) is present between the particles of the metal magnetic powder 11 (white areas in the BSE image) are searched for, and 20 measurement points where Mg element is expected to be detected are selected. Figure 8 shows the 20 measurement points consisting of spectrum 1 to spectrum 20.

[0125] Here, before determining the amount of Mg element detected at each measurement point, elemental analysis of the entire BSE image is performed to determine a reference amount of Mg element detected.

[0126] Fig. 11A is a diagram showing the results of elemental analysis of powder core 10 of sample No. 17. Fig. 11A shows that the detected amounts of each element contained in powder core 10 of sample No. 17 were 70.8 mass% Fe, 13.9 mass% C, 5.8 mass% Si, 4.4 mass% O, 3.5 mass% Cr, and 1.5 mass% Mg.

[0127] In the case of sample No. 17 of the example, the detected amount y of Mg element in the entire BSE image is y = 1.5. The detected amount z of the metal magnetic powder 11 in the entire BSE image is calculated as z = (mass % of Fe element + mass % of Si element + mass % of Cr element), which is z = (70.8 + 5.8 + 3.5). Note that the detected amount z also includes trace amounts of Si element in the silicone resin (binder 12) and Si element in the insulating powder 13.

[0128] When the reference detection amount R3 of the Mg element is calculated based on the detection amount y and the detection amount z in the above (Equation 1), the reference detection amount R3 is the value shown below.

[0129] R3=(1.5 / (100-70.8-5.8-3.5))×100=7.5

[0130] For the powder magnetic core 10 of sample No. 17, the detected amount x of the Mg element at each measurement point is compared with the reference detected amount R3 to determine whether the Mg element is segregated or dispersed at each measurement point.

[0131] Fig. 11B is a diagram showing the amount of Mg element detected at each measurement point in the powder magnetic core 10 of sample No. 17. Fig. 11B shows the amount x of Mg element detected in mass % for each of the 20 measurement points.

[0132] 11B, for spectrum 1, the detected amount of Mg element is 15.4, which is larger than the reference detected amount R3=7.5, so it is determined that Mg element is segregated at the measurement point of spectrum 1. For spectrum 8, the detected amount of Mg element is 5.7, which is smaller than the reference detected amount R3=7.5, so it is determined that Mg element is dispersed at the measurement point of spectrum 8. Similarly, segregation and dispersion of Mg element are determined for the measurement points of the other spectra.

[0133] In Sample No. 17, the detected amount x of Mg element at 9 of the 20 measurement points was greater than the reference detected amount R3, indicating segregation. Furthermore, the detected amount x of Mg element at 11 of the 20 measurement points was smaller than the reference detected amount R3, indicating dispersion. Overall, therefore, in the powder core 10 of Sample No. 17, the insulating powder 13 is neither too clumped nor too scattered, and is considered to be in a moderately dispersed state. Because the insulating powder 13 is in a moderately dispersed state in the powder core 10 of Sample No. 17, as shown in FIG. 7, the magnetic permeability is high at 25.4, and the withstand voltage is high at 237 V / mm. Therefore, the value of "magnetic permeability × withstand voltage" is also considered to be high. Thus, the powder core 10 of Example Sample No. 17 exhibits excellent compatibility between magnetic permeability and withstand voltage.

[0134] (Other Examples) Another example will be described with reference to Fig. 12. In this example, the amounts of first insulating powder 13a and second insulating powder 13b added are changed.

[0135] Fig. 12 shows the evaluation results of powder magnetic cores of other examples. Fig. 12 shows the sample number of the powder magnetic core, the median diameter D50 and amount added of the first insulating powder, the median diameter D50 and amount added of the second insulating powder, the ratio of the median diameter D50 of the first insulating powder to the median diameter D50 of the second insulating powder, the magnetic permeability, the withstand voltage, and "magnetic permeability x withstand voltage." In this figure, the sample numbers are arranged in order of the amount added of the first insulating powder and the median diameter D50 ratio.

[0136] 12, powder magnetic cores 10 of other examples are Samples Nos. 16, 17, and 26 to 35, and powder magnetic cores of comparative examples are Samples Nos. 3, 6, and 8. This figure shows the effects when the total amount of first insulating powder 13a and second insulating powder 13b added is kept constant and the amount of each of first insulating powder 13a and second insulating powder 13b added is varied. In this example, the total amount of first insulating powder 13a and second insulating powder 13b added was 3.0 wt %.

[0137] 12, in Samples Nos. 16, 17, and 26 to 35, the amount (wt %) of first insulating powder 13a was 0.2 to 0.9 times the total amount (wt %) of first insulating powder 13a and second insulating powder 13b. By setting the amount of first insulating powder 13a to 0.2 to 0.9 times the total amount of insulating powder 13, the value of "magnetic permeability × withstand voltage" can be made larger than that of Samples Nos. 3, 6, and 8. In order to further increase the value of "magnetic permeability × withstand voltage," it is desirable to set the amount of first insulating powder 13a to 0.3 to 0.5 times the total amount of insulating powder 13, as in Samples Nos. 16, 17, 28, 29, 33, and 34.

[0138] (summary) As described above, the powder magnetic core 10 according to this embodiment includes metal magnetic powder 11, binder 12 that binds particles of the metal magnetic powder 11 together, and insulating powder 13 provided in binder 12. The insulating powder 13 includes first insulating powder 13a and second insulating powder 13b that have an acicular or plate-like shape. The median diameter D50 of the second insulating powder 13b is smaller than the median diameter D50 of the first insulating powder 13a.

[0139] This makes it possible to increase the withstand voltage of the powder core 10 by the first insulating powder 13a provided between the particles of the metal magnetic powder 11. Furthermore, the magnetic permeability of the powder core 10 can be maintained by the second insulating powder 13b, which has a small median diameter D50 and is provided between the particles of the metal magnetic powder 11. This makes it possible to provide a high-performance powder core 10.

[0140] The median diameter D50 of the first insulating powder 13a may be greater than 0.11 times and smaller than 1.14 times the median diameter D50 of the metal magnetic powder 11.

[0141] In this way, by making the median diameter D50 of the first insulating powder 13a larger than 0.11 times the median diameter D50 of the metal magnetic powder 11 and smaller than 1.14 times the median diameter D50 of the metal magnetic powder 11, it is possible to improve the withstand voltage while suppressing a decrease in the magnetic permeability of the powder core 10. This makes it possible to provide a high-performance powder core 10.

[0142] The median diameter D50 of the first insulating powder 13a may be 1.40 times or more and 11.67 times or less the median diameter D50 of the second insulating powder 13b.

[0143] This makes it possible to increase the withstand voltage of the powder core 10 by using the first insulating powder 13a with a large median diameter D50 provided between the particles of the metal magnetic powder 11. Furthermore, the magnetic permeability of the powder core 10 can be maintained by using the second insulating powder 13b with a small median diameter D50 provided between the particles of the metal magnetic powder 11. This makes it possible to provide a high-performance powder core 10.

[0144] The material of the first insulating powder 13a and the second insulating powder 13b may be talc.

[0145] Talc is a highly insulating material, and therefore can improve the withstand voltage of the powder magnetic core 10 and suppress a decrease in magnetic permeability, thereby providing a high-performance powder magnetic core 10.

[0146] Furthermore, in an elemental analysis of the powder core 10 based on an image of the cross section of the powder core 10, when the amount of Mg element detected at each of 20 measurement points where Mg element is detected between particles of the metal magnetic powder 11 in the image is defined as x, the amount of Mg element detected in the entire image is defined as y, and the amount of metal magnetic powder detected in the entire image is defined as z, There are five or more measurement points that satisfy x>(y / (100-z))×100, and It is also possible to have five or more measurement points that satisfy x<(y / (100-z))×100.

[0147] A powder magnetic core 10 that satisfies this condition can be realized as a powder magnetic core 10 in which the insulating powder 13 is appropriately dispersed. This makes it possible to increase the withstand voltage while maintaining the magnetic permeability of the powder magnetic core 10. This makes it possible to provide a high-performance powder magnetic core 10.

[0148] The method for producing a powder magnetic core according to this embodiment includes a first step of mixing metal magnetic powder 11 and insulating powder 13, a second step of adding a thermosetting resin to metal magnetic powder 11 and insulating powder 13 after the first step and mixing them, and a third step of pressure-molding the mixture produced in the second step. In the first step, insulating powder 13 includes first insulating powder 13a and second insulating powder 13b, each having an acicular or plate-like shape, and second insulating powder 13b has a smaller median diameter D50 than first insulating powder 13a.

[0149] This allows the first insulating powder 13a to be provided between the particles of the metal magnetic powder 11, thereby increasing the withstand voltage of the powder core 10. Furthermore, the second insulating powder 13b with a small median diameter D50 is provided between the particles of the metal magnetic powder 11, thereby maintaining the magnetic permeability of the powder core 10. This allows the powder core 10 to have high performance.

[0150] The amount of first insulating powder 13a added may be 0.2 to 0.9 times the total amount of first insulating powder 13a and second insulating powder 13b added.

[0151] This makes it possible to increase the withstand voltage of the powder core 10 by using the first insulating powder 13a, and to adjust the magnetic permeability of the powder core 10 by using the second insulating powder 13b, thereby providing a high-performance powder core 10.

[0152] (Other embodiments, etc.) Although the powder magnetic cores and the like according to the embodiments of the present disclosure have been described above, the present disclosure is not limited to these embodiments.

[0153] In the above examples, the segregation and dispersion of Mg elements are determined based on a single reference detection amount R. However, the present invention is not limited to this example, and the reference detection amount R may have a predetermined range. For example, a range of ±2% may be set for the reference detection amount R calculated by (Equation 1), and the reference detection amount R3 for Sample No. 17 may be set to R3 = 5.5 to 9.5. In this case, for Sample No. 17, the detection amount x of Mg elements at 9 out of 20 measurement points is greater than the reference detection amount R3, and the sample is determined to be segregated. Furthermore, for 8 out of 20 measurement points, the detection amount x of Mg elements is smaller than the reference detection amount R3, and the sample is determined to be dispersed. Even in this case, the insulating powder 13 in Sample No. 17 is determined to be neither too clumped nor too dispersed, and to be in an appropriate dispersion state.

[0154] In the above embodiment, the segregation and dispersion of Mg element is determined based on 20 measurement points in a BSE image, but the number of measurement points is not limited to 20. For example, the number of measurement points may be N (N is an integer of 10 or more).

[0155] In this case, in an elemental analysis of the powder core 10 based on an image of the cross section of the powder core 10, when the amount of Mg element detected at each of N measurement points where Mg element is detected between particles of the metal magnetic powder 11 in the image is defined as x, the amount of Mg element detected in the entire image is defined as y, and the amount of metal magnetic powder 11 detected in the entire image is defined as z, There are (N / 4) or more measurement points that satisfy x>(y / (100-z))×100, and When there are (N / 4) or more measurement points that satisfy x<(y / (100-z))×100, it may be determined that the insulating powder is adequately dispersed.

[0156] For example, the present disclosure also includes electrical components using the above-described powder magnetic cores. Examples of electrical components include inductance components such as high-frequency reactors, inductors, and transformers. The present disclosure also includes power supply devices equipped with the above-described electrical components.

[0157] Furthermore, the present disclosure is not limited to the embodiment, and various modifications conceivable by those skilled in the art to the present embodiment and forms constructed by combining components of different embodiments may also be included within the scope of one or more aspects, as long as they do not deviate from the spirit of the present disclosure. [Industrial Applicability]

[0158] The powder magnetic core according to the present disclosure can be used as a material for the magnetic core of high-frequency inductors, transformers, and the like. [Explanation of symbols]

[0159] 10 powder magnetic core 11 Metal magnetic powder 12 Binder 13. Insulating powder 13a First insulating powder 13b Second insulating powder 20, 30 Lead section 25 First terminal member 35 Second terminal member 40 Coil material 100 Electrical Components

Claims

1. Metal magnetic powder; a binder that binds the particles of the metal magnetic powder together; an insulating powder disposed in the binder; and the insulating powder includes a first insulating powder and a second insulating powder each having a needle-like or plate-like shape; the median diameter D50 of the second insulating powder is smaller than the median diameter D50 of the first insulating powder; The material of the first insulating powder and the second insulating powder is talc. Powder magnetic core.

2. the median diameter D50 of the first insulating powder is greater than 0.11 times and smaller than 1.14 times the median diameter D50 of the metal magnetic powder; The powder magnetic core according to claim 1 .

3. the median diameter D50 of the first insulating powder is 1.40 times or more and 11.67 times or less the median diameter D50 of the second insulating powder; The powder magnetic core according to claim 2 .

4. In the elemental analysis of the powder magnetic core based on the image of the cross section of the powder magnetic core, Among 20 measurement points where Mg elements are detected between particles of the metal magnetic substance powder in the image, the amount of Mg elements detected at each of the measurement points is defined as x, The detected amount of Mg element in the entire image is defined as y, When the detected amount of the metal magnetic powder in the entire image is z, There are five or more measurement points that satisfy x>(y / (100-z))×100, and There are five or more measurement points that satisfy x < (y / (100 - z)) × 100, The powder magnetic core according to any one of claims 1 to 3.

5. A first step of mixing a metal magnetic powder and an insulating powder; a second step of adding a thermosetting resin to the metal magnetic powder and the insulating powder and mixing them after the first step; a third step of pressure-molding the mixture produced in the second step; Including, In the first step, the insulating powder includes a first insulating powder and a second insulating powder having a needle-like or plate-like shape, and a median diameter D50 of the second insulating powder is smaller than a median diameter D50 of the first insulating powder; The material of the first insulating powder and the second insulating powder is talc. A method for manufacturing a powder magnetic core.

6. the amount of the first insulating powder added is 0.2 to 0.9 times the total amount of the first insulating powder and the second insulating powder added; The method for producing the powder magnetic core according to claim 5 .

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