Soft magnetic powder, compacted magnetic core, magnetic elements, and electronic devices

Abstract

To provide a soft magnetic powder capable of producing compacted powder with high packing properties, good magnetic properties, and the ability to withstand high voltages; a compacted magnetic core and magnetic element containing such soft magnetic powder; and an electronic device equipped with the magnetic element. [Solution] A soft magnetic powder characterized in that it is composed of Fe as the main component, Si in a content of 2.5% to 7.5% by mass, Cr in a content of 0.5% to 10.0% by mass, Al in a content of 0.05% to 0.50% by mass, C in a content of 0.005% to 0.050% by mass, and impurities, wherein a weighed 0.5g sample is placed in a cylinder with an inner diameter of 8mm and an axis in the vertical direction, and the withstand voltage is measured while the sample is sandwiched between electrodes from above and below and a load of 20 [kgf] (196 [N]) is applied, and the withstand voltage is measured to be 400 [V] or more.

Description

[Technical Field]

[0001] This invention relates to soft magnetic powder, compacted magnetic core, magnetic element, and electronic equipment. [Background technology]

[0002] Patent Document 1 discloses a soft magnetic alloy powder comprising Fe and Si, and at least one of Cr or Al as constituent elements, wherein the particle surface has an oxide film comprising at least one of Cr or Al in addition to Si as a constituent element, the mass proportion of these elements contained is higher than that of the alloy portion within the grain, and the Si content, expressed by mass proportion, is greater than the sum of the Cr and Al.

[0003] Such soft magnetic alloy powders allow for a higher packing density, which in turn allows for lower pressing pressure. This makes it possible to prevent damage to conductors in coil components, for example, that have internal conductors. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-145405 [Overview of the project] [Problems that the invention aims to solve]

[0005] The soft magnetic alloy powder described in Patent Document 1 has room for improvement in terms of its packing properties during compaction. On the other hand, when the packing properties during compaction are increased, the distance between particles becomes shorter, which tends to reduce the insulating properties of the compacted material.

[0006] Therefore, the challenge is to realize a soft magnetic powder that can improve packing efficiency during compaction, enhance magnetic properties, and produce compacts capable of handling high voltages. [Means for solving the problem]

[0007] The soft magnetic powder according to an example of the application of the present invention is Fe as the main component, Si with a content of 2.5% by mass or more and 7.5% by mass or less, Cr with a content of 0.5% by mass or more and 10.0% by mass or less, Al with a content of 0.05% by mass or more and 0.50% by mass or less, C with a content of 0.005% by mass or more and 0.050% by mass or less, Impurities and It consists of, A weighed 0.5g sample was used as the test subject. When the subject is placed inside a cylinder with an inner diameter of 8 mm and an axis in the vertical direction, and a load of 20 [kgf] (196 [N]) is applied to the subject by sandwiching it between electrodes from above and below, the withstand voltage is measured. The aforementioned withstand voltage is 400[V] or higher.

[0008] The compacted magnetic core according to an application example of the present invention is This includes soft magnetic powder according to an example of the application of the present invention.

[0009] A magnetic element according to an application example of the present invention is The present invention comprises a compacted magnetic core according to an example of its application.

[0010] The electronic device according to an example of the application of the present invention is The present invention comprises a magnetic element according to an example of its application. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic plan view showing a toroidal coil component. [Figure 2] This is a schematic, transmissive perspective view showing a closed-magnetic-circuit type coil component. [Figure 3] This is a perspective view showing a mobile personal computer, which is an electronic device according to the embodiment. [Figure 4] This is a plan view showing a smartphone, which is an electronic device according to the embodiment. [Figure 5]It is a perspective view showing a digital still camera which is an electronic device according to an embodiment. [Figure 6] It is Table 1 showing the composition, manufacturing conditions and evaluation results of the soft magnetic powder for each sample No. [Figure 7] It is Table 2 showing the composition, manufacturing conditions and evaluation results of the soft magnetic powder for each sample No.

Mode for Carrying Out the Invention

[0012] Hereinafter, the soft magnetic powder, compacted magnetic core, magnetic element and electronic device of the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0013] 1. Soft Magnetic Powder The soft magnetic powder according to the embodiment is a metal powder showing soft magnetism. Such soft magnetic powder can be applied to any use, but for example, it is used to bind particles together and manufacture various compacted bodies such as compacted magnetic cores and electromagnetic wave absorbers.

[0014] 1.1. Composition The soft magnetic powder has Fe (iron) as the main component, Si (silicon) with a content of 2.5 mass% or more and 7.5 mass% or less, Cr (chromium) with a content of 0.5 mass% or more and 10.0 mass% or less, Al (aluminum) with a content of 0.05 mass% or more and 0.50 mass% or less, C (carbon) with a content of 0.005 mass% or more and 0.030 mass% or less, and impurities. Further, when 0.5 g of the weighed sample was used as the test specimen, the test specimen was placed in a cylinder with an inner diameter of 8 mm having an axis in the vertical direction, and the test specimen was sandwiched between electrodes from above and below and the withstand voltage was measured under a load of 20 [kgf] (196 [N]), the withstand voltage was 400 [V] or more.

[0015] According to such a configuration, for the Fe—Si—Cr-based composition forming soft magnetism, the optimum amounts of Al and C are added, so that while the sphericity is increased, the surface insulation is enhanced, and a good withstand voltage can be realized even during powder compaction. Therefore, it is possible to improve the filling property during powder compaction, improve the magnetic properties, and realize a soft magnetic powder capable of manufacturing a compacted body with good withstand voltage.

[0016] The following will explain each component in turn. Fe is the main component of soft magnetic powder. The main component is the element with the highest atomic ratio. Fe has a significant impact on the basic magnetic properties of soft magnetic powder.

[0017] The Fe content is not particularly limited, but is preferably 80.0% by mass or more, and more preferably 85.0% by mass or more.

[0018] The Si content is 2.5% by mass or more and 7.5% by mass or less, but preferably 2.7% by mass or more and 5.0% by mass or less, and more preferably 3.0% by mass or more and 4.5% by mass or less. If the Si content is within the above range, a compacted powder with higher magnetic permeability can be obtained. If the Si content falls below the lower limit, magnetic properties such as magnetic permeability and DC superposition characteristics will decrease. On the other hand, if the Si content exceeds the upper limit, the soft magnetic powder hardens and the packing ability decreases, so the density of the compacted powder decreases.

[0019] The Cr content is 0.5% by mass or more and 10.0% by mass or less, but preferably 0.6% by mass or more and 6.0% by mass or less, and more preferably 0.8% by mass or more and 3.0% by mass or less. If the Cr content is within the above range, the oxidation resistance of the soft magnetic powder is improved and the amount of oxide is optimized. This makes it possible to improve the weather resistance of the soft magnetic powder while ensuring insulation between particles during compaction. As a result, the magnetic properties during compaction are improved and a soft magnetic powder capable of producing compacts that can withstand high voltages can be realized. If the Cr content falls below the lower limit, the oxidation resistance of the soft magnetic powder decreases. On the other hand, if the Cr content exceeds the upper limit, the amount of Fe decreases relatively and the amount of oxide becomes excessive, resulting in a decrease in magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density.

[0020] Furthermore, the mass ratio of Si content to Cr content is defined as Si / Cr. The mass ratio Si / Cr is preferably 0.5 to 5.0, more preferably 1.0 to 4.5, and even more preferably 1.5 to 4.0. If the mass ratio Si / Cr is within the above range, the balance between Si content and Cr content can be optimized. This makes it possible to produce a soft magnetic powder with good magnetic properties without reducing the dielectric strength.

[0021] The Al content is preferably 0.05% by mass or more and 0.50% by mass or less, but more preferably 0.07% by mass or more and 0.40% by mass or less, and more preferably 0.09% by mass or more and 0.30% by mass or less. If the Al content is within the above range, the soft magnetic powder can be made spherical. Also, if the Al content is within the above range, the oxidation resistance of the soft magnetic powder is improved, similar to Cr, and the amount of oxide is optimized. This makes it possible to improve the weather resistance of the soft magnetic powder while ensuring insulation between particles when compacted. As a result, the magnetic properties when compacted are improved, and a soft magnetic powder can be realized that can be manufactured into a compact that can withstand high voltages. Also, if the Al content is within the above range, the surface tension of the molten metal can be lowered, making it easier to make the powder spherical when it is finely powdered. This makes it possible to obtain a soft magnetic powder that has good packing properties and can be manufactured into a compact that is high density and has good magnetic properties. If the Al content falls below the lower limit, the packing properties, oxidation resistance, and voltage withstand when compacted of the soft magnetic powder will decrease. On the other hand, if the Al content exceeds the aforementioned upper limit, the amount of Fe decreases relatively and the amount of oxides becomes excessive, resulting in a decrease in magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density.

[0022] The carbon (C) content is preferably between 0.005% by mass and 0.050% by mass, more preferably between 0.010% by mass and 0.045% by mass, and more preferably between 0.015% by mass and 0.040% by mass. If the carbon (C) content is within the above range, the hardness of the particles of the soft magnetic powder can be optimized. This ensures adequate fluidity before compaction, while also providing a soft magnetic powder that exhibits appropriate deformability during compaction. Such soft magnetic powder has good packing properties and contributes to the production of high-density compacts with good magnetic properties. If the carbon (C) content falls below the lower limit, the particles lack sufficient hardness, resulting in a large number of irregularly shaped particles before compaction. This reduces the fluidity of the soft magnetic powder and decreases the packing properties during compaction. On the other hand, if the carbon (C) content exceeds the upper limit, the particles become excessively hard. This reduces the packing properties of the soft magnetic powder during compaction.

[0023] Furthermore, the mass ratio of the C content to the Al content is defined as C / Al. The mass ratio C / Al is preferably 0.010 to 0.500, more preferably 0.050 to 0.450, and even more preferably 0.080 to 0.400. If the mass ratio C / Al is within the above range, the balance between the C content and the Al content can be optimized. This makes it possible to achieve a more optimal balance between the sphericization of particles by adding Al and the optimization of particle hardness by adding C. As a result, a soft magnetic powder with particularly good packing properties during compaction can be obtained.

[0024] Furthermore, if the mass ratio C / Al falls below the lower limit, the balance between the C content and Al content will be disrupted, potentially leading to insufficient particle hardness, reduced fluidity of the soft magnetic powder, and a decrease in magnetic properties. On the other hand, if the mass ratio C / Al exceeds the upper limit, the balance between the C content and Al content will be disrupted, potentially resulting in excessive particle hardness, reduced packing efficiency of the soft magnetic powder, and insufficient spheroidization of the particles.

[0025] Soft magnetic powder may contain other elements as impurities in addition to the elements mentioned above. Impurities refer to elements other than those mentioned above that are inevitably mixed in.

[0026] The concentration of impurities is preferably 0.10% by mass or less for each element, and more preferably 0.05% by mass or less. Furthermore, the total concentration of impurities is preferably 1.00% by mass or less. Within this range, the presence of other elements is acceptable as it does not affect the effect of the soft magnetic powder.

[0027] Furthermore, the soft magnetic powder according to the embodiment may contain oxygen as an impurity. The oxygen content of the soft magnetic powder is preferably 3000 ppm or less by mass, more preferably 2000 ppm or less, and even more preferably 1500 ppm or less. This suppresses deterioration of particle shape due to surface adhesion of oxides, thereby obtaining a soft magnetic powder with high packing efficiency during compaction. In addition, it suppresses a decrease in the metal occupancy rate in the compacted material, thus obtaining a compacted material with good magnetic properties. On the other hand, a lower limit does not need to be set, but from the viewpoint of ensuring insulation between particles, the lower limit of the oxygen content is preferably 300 ppm or more, and more preferably 500 ppm or more. This ensures sufficient insulation between particles, and a compacted material with good dielectric strength can be obtained.

[0028] The above composition is determined by the following analytical methods. Examples of analytical methods include atomic absorption spectrometry for iron and steel as specified in JIS G 1257:2000, ICP emission spectrometry for iron and steel as specified in JIS G 1258:2007, spark discharge emission spectrometry for iron and steel as specified in JIS G 1253:2002, X-ray fluorescence spectrometry for iron and steel as specified in JIS G 1256:1997, and gravimetric titration-absorbance spectrophotometric methods as specified in JIS G 1211 to G 1237.

[0029] Specifically, examples include solid-state emission spectrometers manufactured by SPECTRO, particularly spark discharge emission spectrometers, model: SPECTROLAB, type: LAVMB08A, and the ICP instrument CIROS120 manufactured by Rigaku Corporation.

[0030] Furthermore, in particular for the identification of C (carbon) and S (sulfur), the combustion in an oxygen stream (high-frequency induction heating furnace combustion)-infrared absorption method specified in JIS G 1211:2011 is also used. Specifically, the LECO CS-200 carbon-sulfur analyzer is used.

[0031] Furthermore, in particular for the identification of nitrogen (N) and oxygen (O), the methods for determining nitrogen in iron and steel specified in JIS G 1228:1997 and the general rules for determining oxygen in metallic materials specified in JIS Z 2613:2006 are also used. Specifically, examples include the LECO TC-300 / EF-300 oxygen / nitrogen analyzer and the LECO ONH836 oxygen / nitrogen / hydrogen analyzer.

[0032] 1.2. Powder Characteristics The average particle size of the soft magnetic powder according to this embodiment is 2.0 μm or more and 12.0 μm or less, preferably 4.0 μm or more and 10.0 μm or less, and more preferably 5.0 μm or more and 9.5 μm or less. This makes it possible to obtain a soft magnetic powder that can be manufactured into a compacted body with high packing efficiency and good dielectric strength.

[0033] Furthermore, if the average particle size of the soft magnetic powder falls below the lower limit, the soft magnetic powder becomes more prone to aggregation, reducing its packing ability and decreasing the density of the compacted material. On the other hand, if the average particle size of the soft magnetic powder exceeds the upper limit, the dielectric strength of the compacted material may decrease.

[0034] The average particle size refers to the particle size D50, where the cumulative frequency from the smallest diameter side accounts for 50% of the volume-based cumulative particle size distribution of soft magnetic powder obtained using a laser diffraction particle size distribution analyzer.

[0035] When the soft magnetic powder according to the embodiment is subjected to particle size classification, it is preferable that the resulting classified products satisfy the following predetermined relationships with one another.

[0036] Specifically, the soft magnetic powder is first classified using a first sieve with a mesh size of 45 μm. The classified material that passes through the first sieve is designated as -45 particles.

[0037] Next, the -45 particles are classified using a second sieve with a mesh size of 32 μm. The particles remaining on the second sieve are designated as +32 particles, and the particles that pass through the second sieve are designated as -32 particles.

[0038] Next, the -32 particles are classified using a third sieve with a mesh size of 16 μm. The particles remaining on the third sieve are designated as +16 particles, and the particles that pass through the third sieve are designated as -16 particles.

[0039] Here, let X be the average circularity of -45 particles. Also, let Y1 be the average circularity of +32 particles, Y2 be the average circularity of +16 particles, and Y3 be the average circularity of -16 particles.

[0040] The soft magnetic powder according to the embodiment preferably satisfies the following formulas (1), (2), and (3).

[0041] Y1 = αX … (1) Y² = βX … (2) Y3 = γX … (3) (The coefficients α in equation (1), β in equation (2), and γ in equation (3) are each between 0.95 and 1.05.)

[0042] By satisfying these relationships, a soft magnetic powder with particularly good packing properties can be obtained. In other words, in order to improve the packing properties of soft magnetic powder, it is particularly required that the particles be made spherical regardless of the particle size, and that the particle size distribution be optimized. In this embodiment, the soft magnetic powder is made spherical not only by optimizing the composition, but also by improving the manufacturing method described later, which minimizes the difference in the degree of sphericity between the classified products. Therefore, the soft magnetic powder in this embodiment has particularly high packing properties when compacted.

[0043] Furthermore, the average circularity X is preferably 0.80 to 0.95, preferably 0.82 to 0.92, and more preferably 0.85 to 0.90. This results in a soft magnetic powder with particularly good packing properties during compaction. In addition, when an insulating film is formed on the particle surface of the soft magnetic powder, it can be formed uniformly and without unevenness. This makes it possible to manufacture a compact with excellent inter-particle insulation properties. Moreover, by forming the film uniformly and without unevenness, the specific surface area can be reduced, so the amount of binder covering the surface can also be reduced. Therefore, since less binder is needed to bind the particles together, the magnetic properties of the compact can be improved from this viewpoint as well.

[0044] Furthermore, if the average circularity X, Y1, Y2, and Y3 each fall below the aforementioned lower limit, the packing efficiency of the soft magnetic powder during compaction may decrease, or the uniformity of the insulating film thickness may decrease. On the other hand, if the average circularity X, Y1, Y2, and Y3 each exceed the aforementioned upper limit, the difficulty of manufacturing the soft magnetic powder may increase.

[0045] The average circularity X, Y1, Y2, and Y3 of the soft magnetic powder are measured as follows:

[0046] First, an image (secondary electron image) of the soft magnetic powder is captured using a scanning electron microscope (SEM). Next, the obtained image is loaded into image processing software. For example, image processing software such as "Mac-View," an image analysis-based particle size distribution measurement software manufactured by Mountec Co., Ltd. is used. The imaging magnification is adjusted so that 50 to 100 particles are captured in each image. Then, multiple images are acquired so that a total of 300 or more particle images are obtained.

[0047] Next, the circularity of more than 300 particle images is calculated using software, and the average value is determined. The resulting average value is the average circularity of the soft magnetic powder. When the circularity is denoted as e, the area of ​​the particle image as S, and the perimeter of the particle image as L, the circularity e can be calculated using the following formula. e = 4πS / L 2

[0048] In the soft magnetic powder according to the embodiment, the Vickers hardness of the particle cross-section is preferably 250 to 400, and more preferably 275 to 350. When the Vickers hardness of the particle cross-section is within this range, the surface of the particles deforms appropriately when the soft magnetic powder is compacted. This improves the packing efficiency of the soft magnetic powder during compaction. If the Vickers hardness falls below the lower limit, the particle surface may deform excessively, potentially reducing the fluidity of the soft magnetic powder. Conversely, if the Vickers hardness exceeds the upper limit, the particle surface may not deform easily, potentially reducing the packing efficiency of the soft magnetic powder during compaction.

[0049] The Vickers hardness of a particle cross-section is measured as follows: First, the cross-section of the particle is exposed and observed with an optical microscope. Next, the Vickers hardness at the center of the cross-section is measured using a hardness tester. A Vickers hardness tester is used. The measurement load is 5 kgf (49 N), and the load holding time is 10 seconds.

[0050] The specific surface area of ​​the soft magnetic powder according to this embodiment is 0.190 m². 2 / g or more 0.350m2 It is preferably below / g, and 0.210 m 2 / g or more and 0.300 m 2 / g or less is more preferable. If the specific surface area is within the above range, the packing property of the soft magnetic powder is improved, and the density of the compacted powder can be increased. If the specific surface area is below the lower limit value, there is a risk that the packing property of the soft magnetic powder may decrease due to the increase in particle size. On the other hand, if the specific surface area exceeds the upper limit value, the particles of the soft magnetic powder tend to aggregate, resulting in a decrease in packing property and a possible decrease in the density of the compacted powder.

[0051] Note that the specific surface area is obtained by the BET method. As a measuring device for the specific surface area, for example, the BET type specific surface area measuring device HM1201-010 manufactured by Mountech Co., Ltd. can be mentioned, and the amount of the sample is 5 g.

[0052] The tap density of the soft magnetic powder according to the embodiment is 4.50 g / cm 3 or more and 5.10 g / cm 3 or less is preferable, and 4.65 g / cm 3 or more and 5.00 g / cm 3 or less is more preferable. If the tap density is within the above range, a soft magnetic powder having particularly good packing property can be obtained. Thereby, a compacted powder with high density and good magnetic properties can be manufactured. If the tap density is below the lower limit value, there is a risk that the packing property of the soft magnetic powder may decrease and the density of the compacted powder may decrease. On the other hand, if the tap density exceeds the upper limit value, there is a risk that the manufacturing difficulty of the soft magnetic powder may increase.

[0053] The tap density of the soft magnetic powder is measured by a powder property evaluation device. Examples of the powder property evaluation device include the Powder Tester (registered trademark) PT-X manufactured by Hosokawa Micron Corporation.

[0054] The relative density of the compacted powder obtained by compacting the soft magnetic powder according to the embodiment at a pressure of 588.4 MPa is preferably 79.0% or more, and more preferably 80.0% or more and 85.0% or less. Thereby, a soft magnetic powder having particularly good packing property and excellent manufacturability can be obtained.

[0055] The relative density of the compacted material is determined by dividing the weight of the compacted material formed under the above pressure by the volume calculated from its external dimensions, and then dividing the resulting density by the true density of the soft magnetic powder.

[0056] 1.3. Electrical and Magnetic Properties In the embodiment, when a 0.5g sample of the soft magnetic powder is placed inside a cylinder with an inner diameter of 8mm and an axis in the vertical direction, and a load of 20kgf (196N) is applied to the sample by sandwiching it between electrodes from above and below, the withstand voltage is measured, and the withstand voltage is 400V or more, preferably 450V to 4000V. Soft magnetic powders with a withstand voltage within this range contribute to the realization of magnetic elements that are small but have a high rated voltage.

[0057] Furthermore, if the withstand voltage falls below the lower limit, the rated voltage of the magnetic element cannot be sufficiently increased. On the other hand, the withstand voltage may exceed the upper limit, but in that case, there is a risk that the variation in the withstand voltage of the magnetic element will increase.

[0058] The method for measuring withstand voltage is as follows: First, 0.5 g of soft magnetic powder is weighed out as the test subject. Next, a resin cylinder with an inner diameter of 8 mm and an axis in the vertical direction is prepared, and the test subject is placed inside. Then, the test subject is sandwiched between two brass electrodes from above and below. The electrodes are cylindrical in shape with an outer diameter (approximately 8 mm) that slides against the inner surface of the cylinder. Next, a load of 20 kgf (196 N) is applied to the test subject through the electrodes, and a DC voltage is applied between the electrodes. Next, the electrical resistance between the electrodes is measured using a digital multimeter while increasing the voltage in 50 V increments. The voltage at which the electrical resistance becomes 1 MΩ or less is defined as the withstand voltage. For example, if the electrical resistance becomes 1 MΩ or less when the voltage is 550 V, the withstand voltage is set to 500 V.

[0059] The saturation magnetic flux density Bs of the soft magnetic powder according to the embodiment is preferably 1.80[T] or higher, and more preferably 1.90[T] or higher. This makes it possible to obtain a soft magnetic powder that can be used to manufacture magnetic elements that are less likely to saturate even at high currents.

[0060] The saturation magnetic flux density Bs of soft magnetic powder is measured by the following method. First, the true density ρ[g / cm³] of the soft magnetic powder was measured using a fully automated gas-filled densimeter, the AccuPyc1330, manufactured by Micromerities Co., Ltd. 3 The ] is measured. Note that the method for measuring the true density ρ is not limited to this. Next, the maximum magnetic moment Mm [emu / g] of the soft magnetic powder is measured using a vibrating sample magnetometer, VSM system, TM-VSM1230-MHHL, manufactured by Tamagawa Seisakusho Co., Ltd. Then, the saturation magnetic flux density Bs [T] is calculated using the following formula. Bs = 4π / 10000 × ρ × Mm

[0061] 2. Method for producing soft magnetic powder Next, we will describe an example of a method for producing the soft magnetic powder mentioned above.

[0062] The soft magnetic powder may be produced by any method. Examples of production methods include various atomization methods such as water atomization, rotary water flow atomization, and gas atomization, as well as pulverization methods. Of these, powder produced by atomization is preferably used for soft magnetic powder. The atomization method allows for the efficient production of metal powder with a particle shape closer to a perfect sphere.

[0063] The atomization method is a method for producing metal powder by causing molten metal to collide with a rapidly sprayed liquid or gas, thereby finely milling and cooling it. In the atomization method, the molten metal undergoes further spheroidization during the solidification process after fine milling, making it possible to produce particles that are closer to perfect spheres.

[0064] The water atomization method is a method for producing metal powder from molten metal by using a liquid such as water as a coolant, spraying it in an inverted cone shape so that it converges to a single point, and simultaneously flowing molten metal down towards this convergence point and causing a collision.

[0065] The rotary water atomization method is a method for producing metal powder by supplying a coolant along the inner surface of a cooling cylinder and swirling it along the inner surface, while simultaneously blowing a jet of liquid or gas onto molten metal and incorporating the scattered molten metal into the coolant.

[0066] The gas atomization method is a method of producing metal powder from molten metal by using a gas as a coolant, spraying it in an inverted cone shape that focuses on a single point, and simultaneously flowing molten metal down towards this point of focus and causing it to collide with the gas.

[0067] The casting temperature of the melting point Tm [°C] of the constituent material of the soft magnetic powder is preferably set to Tm + 200°C or higher, more preferably to Tm + 220°C or higher and Tm + 350°C or lower, and even more preferably to Tm + 250°C or higher and Tm + 300°C or lower. This allows the molten metal to exist for a longer time than conventional methods when it is refined and solidified by various atomization methods. This helps to make the particles spherical.

[0068] In the atomization method, molten metal is flowed down through a narrow nozzle opening, and the resulting fine stream of molten metal is made to collide with a fluid jet. The inner diameter of the nozzle opening from which the molten metal is discharged is not particularly limited, but is preferably 2.5 mm or less, more preferably 0.3 mm to 2.0 mm, and even more preferably 0.5 mm to 1.5 mm. This makes it easier to uniformly apply the fluid jet to the molten metal, so that droplets of an appropriate size are easily dispersed uniformly. As a result, soft magnetic powder with spherical shape can be easily produced regardless of particle size. In addition, because the cooling rate is relatively fast, the particle size of the crystal grains formed inside the particles can be kept small, making it easier to increase the Vickers hardness of the soft magnetic powder.

[0069] Furthermore, the manufactured soft magnetic powder may be classified as needed. Examples of classification methods include dry classification such as sieving, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0070] 3. Compacted magnetic cores and magnetic elements Next, the powdered magnetic core and magnetic element according to the embodiment will be described.

[0071] The magnetic element according to this embodiment is applicable to various magnetic elements equipped with a magnetic core, such as choke coils, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the compacted magnetic core according to this embodiment is applicable to the magnetic cores provided in these magnetic elements.

[0072] Below, we will describe two types of coil components as representative examples of magnetic elements. 3.1. Toroidal type First, we will describe a toroidal coil component, which is an example of a magnetic element according to the embodiment. Figure 1 is a schematic plan view showing a toroidal coil component.

[0073] The coil component 10 shown in Figure 1 has a ring-shaped powdered magnetic core 11 and a conductor 12 wound around this powdered magnetic core 11. Such a coil component 10 is generally called a toroidal coil.

[0074] The compacted magnetic core 11 is obtained by mixing the soft magnetic powder and binder according to the embodiment, supplying the resulting mixture to a mold, and then pressurizing and molding it. Therefore, the compacted magnetic core 11 is a compacted body containing the soft magnetic powder according to the embodiment. With such a compacted magnetic core 11, the packing is improved, and thus the density is increased. As a result, a coil component 10 with improved magnetic properties and the ability to handle high voltages can be obtained. Therefore, when the coil component 10 is mounted on electronic equipment, the performance and miniaturization of the electronic equipment can be improved.

[0075] Examples of binder materials used in the production of the compacted magnetic core 11 include organic materials such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins, and inorganic materials such as phosphates like magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates like sodium silicate. These resin materials harden easily when heated and have excellent heat resistance. Therefore, the ease of manufacturing and heat resistance of the compacted magnetic core 11 can be improved.

[0076] The ratio of binder to soft magnetic powder varies slightly depending on the desired magnetic and mechanical properties of the compacted magnetic core 11 to be manufactured, the allowable eddy current loss, etc., but is preferably around 0.3% to 5.0% by mass, more preferably around 0.5% to 3.0% by mass, and even more preferably around 0.7% to 2.0% by mass. This makes it possible to obtain a coil component 10 with excellent magnetic properties while sufficiently binding the soft magnetic powder particles together. Various additives may be added to the mixture as needed, for any purpose.

[0077] The constituent material of the conductor 12 is a highly conductive material, such as a metallic material containing Cu, Al, Ag, Au, Ni, etc. Furthermore, an insulating film may be provided on the surface of the conductor 12 as needed.

[0078] The shape of the compacted magnetic core 11 is not limited to the ring shape shown in Figure 1. For example, it may be a shape in which a part of the ring is missing, a shape in which the longitudinal direction is straight, or a sheet shape, film shape, etc.

[0079] The compacted magnetic core 11 may, if necessary, contain soft magnetic powders other than the soft magnetic powder described in the above embodiment, or non-magnetic powders.

[0080] 3.2. Closed Magnetic Circuit Type Next, we will describe a closed-circuit type coil component, which is an example of a magnetic element according to the embodiment. Figure 2 is a schematic transmission perspective view showing a closed magnetic circuit type coil component.

[0081] The following describes closed-circuit type coil components, focusing on the differences from toroidal type coil components, and omitting explanations of similar aspects.

[0082] As shown in Figure 2, the coil component 20 according to this embodiment is formed by embedding a coil-shaped conductor 22 inside a compacted magnetic core 21. That is, the coil component 20, which is a magnetic element, comprises a compacted magnetic core 21 containing the aforementioned soft magnetic powder, and the conductor 22 is molded with the compacted magnetic core 21. This compacted magnetic core 21 has the same configuration as the compacted magnetic core 11 described above. This makes it possible to realize a high-density compacted magnetic core 21.

[0083] Furthermore, coil components 20 of this form are relatively easy to miniaturize. Therefore, when coil components 20 are mounted on electronic devices, it is possible to improve the performance and miniaturize the electronic devices.

[0084] Furthermore, since the conductor 22 is embedded inside the compacted magnetic core 21, gaps are less likely to form between the conductor 22 and the compacted magnetic core 21. This suppresses vibrations caused by magnetostriction of the compacted magnetic core 21, and thus suppresses the generation of noise associated with these vibrations.

[0085] The shape of the compacted magnetic core 21 is not limited to the shape shown in Figure 2, and may be in the form of a sheet, film, or the like.

[0086] Furthermore, the compacted magnetic core 21 may, if necessary, contain soft magnetic powders other than the soft magnetic powder described in the embodiment above, or non-magnetic powders.

[0087] 4.Electronic equipment Next, an electronic device equipped with a magnetic element according to the embodiment will be described with reference to Figures 3 to 5.

[0088] Figure 3 is a perspective view showing a mobile personal computer, which is an electronic device according to an embodiment. The personal computer 1100 shown in Figure 3 comprises a main body 1104 equipped with a keyboard 1102 and a display unit 1106 equipped with a display unit 100. The display unit 1106 is rotatably supported by the main body 1104 via a hinge structure. Such a personal computer 1100 incorporates magnetic elements 1000, such as a choke coil or inductor for a switching power supply, and a motor.

[0089] Figure 4 is a plan view showing a smartphone, which is an electronic device according to the embodiment. The smartphone 1200 shown in Figure 4 is equipped with a plurality of operation buttons 1202, an earpiece 1204, and a microphone 1206. A display unit 100 is also positioned between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 incorporates magnetic elements 1000, such as an inductor, a noise filter, and a motor.

[0090] Figure 5 is a perspective view showing a digital still camera, which is an electronic device according to the embodiment. The digital still camera 1300 generates an imaging signal by photoelectrically converting the light image of a subject using an image sensor such as a CCD (Charge Coupled Device).

[0091] The digital still camera 1300 shown in Figure 5 includes a display unit 100 located on the back of the case 1302. The display unit 100 functions as a viewfinder, displaying the subject as an electronic image. A light-receiving unit 1304, including an optical lens and a CCD, is provided on the front side of the case 1302, i.e., the back side in the figure.

[0092] When the photographer confirms the subject image displayed on the display unit 100 and presses the shutter button 1306, the imaging signal from the CCD at that moment is transferred and stored in the memory 1308. Such a digital still camera 1300 also incorporates magnetic elements 1000, such as an inductor and a noise filter.

[0093] Examples of electronic devices according to this embodiment include, in addition to the personal computer in Figure 3, the smartphone in Figure 4, and the digital still camera in Figure 5, mobile phones, tablet terminals, watches, inkjet printers and other inkjet ejection devices, laptop personal computers, televisions, video cameras, video tape recorders, car navigation systems, pagers, electronic organizers, electronic dictionaries, calculators, electronic game devices, word processors, workstations, video phones, security television monitors, electronic binoculars, POS terminals, electronic thermometers, blood pressure monitors, blood glucose meters, electrocardiogram measuring devices, ultrasound diagnostic devices, medical devices such as electronic endoscopes, fish finders, various measuring instruments, instruments for vehicles, aircraft, and ships, mobile control devices such as automobile control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, and flight simulators.

[0094] As described above, such electronic devices are equipped with magnetic elements according to the embodiment. This allows for the enjoyment of the effects of the magnetic elements according to the embodiment, thereby improving the performance and miniaturization of the electronic devices.

[0095] 5. Effects of the Embodiment As described above, the soft magnetic powder according to the embodiment is composed of Fe as the main component, Si in a content of 2.5% to 7.5% by mass, Cr in a content of 0.5% to 10.0% by mass, Al in a content of 0.05% to 0.50% by mass, C in a content of 0.005% to 0.050% by mass, and impurities. Furthermore, when 0.5 g of the soft magnetic powder according to the embodiment is used as a test subject, the test subject is placed in a cylinder with an inner diameter of 8 mm and an axis in the vertical direction, and the withstand voltage is measured while the test subject is sandwiched between electrodes from above and below and a load of 20 [kgf] (196 [N]) is applied to the test subject, the withstand voltage is 400 [V] or more.

[0096] This configuration makes it possible to produce soft magnetic powder that has high packing properties, good magnetic properties, and can withstand high voltages, enabling the manufacture of compacted powders.

[0097] In the soft magnetic powder according to this embodiment, the maximum magnetic moment measured using a vibrating sample magnetometer is Mm [emu / g], and the true density is ρ [g / cm³]. 3 In this case, it is preferable that the saturation magnetic flux density Bs, which can be calculated as Bs = 4π / 10000 × ρ × Mm, is 1.80 T or higher.

[0098] With this configuration, a soft magnetic powder can be obtained that can be used to manufacture magnetic elements that are less likely to saturate even at high currents.

[0099] In the soft magnetic powder according to this embodiment, the powder is classified using a first sieve with a mesh size of 45 μm, and the classified material that passes through the first sieve is designated as -45 particles. The -45 particles are then classified using a second sieve with a mesh size of 32 μm, and the classified material remaining on the second sieve is designated as +32 particles. The classified material that passes through the second sieve is designated as -32 particles. The -32 particles are then classified using a third sieve with a mesh size of 16 μm, and the classified material remaining on the third sieve is designated as +16 particles. The classified material that passes through the third sieve is designated as -16 particles. Furthermore, the average circularity of the -45 particles is denoted as X, the average circularity of the +32 particles as Y1, the average circularity of the +16 particles as Y2, and the average circularity of the -16 particles as Y3. In this case, it is preferable that the soft magnetic powder according to this embodiment satisfies the following formulas (1), (2), and (3).

[0100] Y1 = αX … (1) Y² = βX … (2) Y3 = γX … (3) (The coefficients α in equation (1), β in equation (2), and γ in equation (3) are each between 0.95 and 1.05.) With this configuration, a soft magnetic powder with particularly good packing properties can be obtained.

[0101] In the soft magnetic powder according to the embodiment, the ratio of the C content to the Al content is preferably 0.010 or more and 0.250 or less.

[0102] This configuration allows for a more optimal balance between spherical particle formation through the addition of Al and optimization of particle hardness through the addition of C. As a result, a soft magnetic powder with particularly good packing properties during compaction can be obtained.

[0103] In the soft magnetic powder according to the embodiment, it is preferable that the Vickers hardness of the cross-section of the particles is 250 or more and 400 or less.

[0104] With this configuration, when the soft magnetic powder is compacted, the surface of the particles becomes more easily deformed. This improves the packing efficiency of the soft magnetic powder during compaction.

[0105] The compacted magnetic core according to the embodiment contains the soft magnetic powder according to the embodiment. With this configuration, a high-density compacted magnetic core can be obtained.

[0106] The magnetic element according to the embodiment comprises a compacted magnetic core according to the embodiment. With this configuration, a magnetic element can be obtained that has improved magnetic properties and can withstand high voltages.

[0107] The electronic device according to the embodiment includes a magnetic element according to the embodiment. With this configuration, high-performance and miniaturized electronic devices can be obtained.

[0108] Although the soft magnetic powder, compacted magnetic core, magnetic element, and electronic device of the present invention have been described above based on preferred embodiments, the present invention is not limited thereto. For example, the shape of the compacted magnetic core and magnetic element is not limited to those shown in the figures, and may be any shape. [Examples]

[0109] Next, specific embodiments of the present invention will be described. 6. Manufacturing of soft magnetic powder 6.1. Sample No. 1 First, soft magnetic powder was obtained by the water atomization method. The composition of the obtained soft magnetic powder is shown in Table 1 (Figure 6). The manufacturing conditions (difference between casting temperature and melting point) for the soft magnetic powder by the water atomization method are also shown in Table 1. Figure 6 is Table 1, showing the composition, manufacturing conditions, and evaluation results of the soft magnetic powder for each sample No.

[0110] Furthermore, the average particle size, specific surface area, relationship between the average circularity of the classified particles, and Vickers hardness were measured for the obtained soft magnetic powder. The measurement results are shown in Table 1. The relationship between the average circularity of the classified particles is expressed by the coefficients α, β, and γ in equations (1) to (3) mentioned above. The average circularity X was 0.88.

[0111] 6.2. Samples No. 2-17 Soft magnetic powder was obtained in the same manner as for Sample No. 1, except that the composition of the soft magnetic powder was changed as shown in Table 1 (Figure 6) or Table 2 (Figure 7). The average circularity X of the soft magnetic powder for each Sample No. was in the range of 0.85 to 0.90. Figure 7 is Table 2, which shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powder for each Sample No.

[0112] In Tables 1 and 2, among the soft magnetic powders of each sample number, those corresponding to the present invention are designated as "Examples," and those not corresponding to the present invention are designated as "Comparative Examples."

[0113] 7. Evaluation of soft magnetic powders 7.1. Tap density of soft magnetic powder The tap density was measured for each sample No. of soft magnetic powder. The measurement results were then evaluated on a three-point scale from A to C according to the following evaluation criteria. The evaluation results are shown in Tables 1 and 2.

[0114] A: Tap density is 4.65 g / cm³ 3 More than 5.00g / cm 3 The following is B: Tap density is 4.50 g / cm³ 3 More than 5.10g / cm 3 The following applies (excluding range A): C: Tap density is 4.50 g / cm³ 3 Less than 5.10 g / cm³ 3 The following is

[0115] 7.2. Relative density of compacted soft magnetic powder For each sample number of soft magnetic powder, the relative density of the compacted powder was measured after compaction at a pressure of 588.4 MPa. The measurement results were then evaluated on a three-point scale from A to C according to the following evaluation criteria. The evaluation results are shown in Tables 1 and 2.

[0116] A: The relative density of the compacted powder is between 80.0% and 85.0%. B: The relative density of the compacted powder is 79.0% or more but less than 80.0%, or greater than 85.0%. C: The relative density of the compacted powder is less than 79.0%.

[0117] 7.3. Saturated magnetic flux density of soft magnetic powder The saturation magnetic flux density was measured for each sample No. of soft magnetic powder. The measurement results were then evaluated on a three-point scale from A to C according to the following evaluation criteria. The evaluation results are shown in Tables 1 and 2.

[0118] A: The saturation magnetic flux density is 1.90 [T] or higher. B: The saturation magnetic flux density is between 1.80[T] and less than 1.90[T]. C: Saturation magnetic flux density is less than 1.80 [T]

[0119] 7.4. Overall Rating For each sample No. of soft magnetic powder, a comprehensive evaluation was conducted based on the measured dielectric strength during compaction, as well as the evaluation results of the relative density and saturation magnetic flux density of the compacted powder. The evaluation criteria for the comprehensive evaluation are as follows. The evaluation results are shown in Tables 1 and 2.

[0120] A: Withstand voltage of 400[V] or higher, and the evaluation results for both the relative density and saturated magnetic flux density of the compacted powder are both A. B: Withstand voltage of 400[V] or higher, and at least one of the evaluation results for the relative density and saturated magnetic flux density of the compacted powder is B, with the remaining one being A. C: Withstand voltage is less than 400[V], or both the relative density and saturated magnetic flux density evaluation results of the compacted powder are B, or at least one of them is C.

[0121] As shown in Tables 1 and 2, the soft magnetic powders of each example were found to have high packing properties, enabling the production of high-density compacts, and to have good magnetic properties that can withstand high voltages. [Explanation of Symbols]

[0122] 10... Coil component, 11... Powdered magnetic core, 12... Conductor wire, 20... Coil component, 21... Powdered magnetic core, 22... Conductor wire, 100... Display unit, 1000... Magnetic element, 1100... Personal computer, 1102... Keyboard, 1104... Main unit, 1106... Display unit, 1200... Smartphone, 1202... Operation buttons, 1204... Earpiece, 1206... Transmitter, 1300... Digital still camera, 1302... Case, 1304... Light receiving unit, 1306... Shutter button, 1308... Memory

Claims

1. Fe as the main component, Si with a content of 2.5% by mass or more and 7.5% by mass or less, Cr with a content of 0.5% by mass or more and 10.0% by mass or less, Al with a content of 0.05% by mass or more and 0.50% by mass or less, C, which has a content of 0.005% by mass or more and 0.050% by mass or less, Impurities and It consists of, A weighed 0.5 g was used as the test sample. When the subject is placed inside a cylinder with an inner diameter of 8 mm and an axis in the vertical direction, and a load of 20 [kgf] (196 [N]) is applied to the subject by sandwiching it between electrodes from above and below, the withstand voltage is measured. A soft magnetic powder characterized by having a dielectric strength of 400 [V] or more.

2. Let Mm [emu / g] be the maximum magnetic moment measured using a vibrating sample magnetometer. True density is ρ [g / cm³] ３ When ], The soft magnetic powder according to claim 1, wherein the saturation magnetic flux density Bs, which can be calculated using the formula Bs = 4π / 10000 × ρ × Mm, is 1.80 T or more.

3. The material is classified using a first sieve with a mesh size of 45 μm, and the classified material that passes through the first sieve is designated as -45 particles. The -45 particles are classified using a second sieve with a mesh size of 32 μm, the classified material remaining on the second sieve is designated as +32 particles, and the classified material that passes through the second sieve is designated as -32 particles. The -32 particles are classified using a third sieve with a mesh size of 16 μm, the classified material remaining on the third sieve is designated as +16 particles, and the classified material that passes through the third sieve is designated as -16 particles. Let X be the average circularity of the aforementioned -45 particles. Let Y1 be the average circularity of the aforementioned +32 particles. Let Y2 be the average circularity of the aforementioned +16 particles. When the average circularity of the aforementioned -16 particles is Y3, The soft magnetic powder according to claim 1 or 2, satisfying the following formulas (1), (2), and (3). Y1 = αX ... (1) Y² = βX … (2) Y3 = γX ... (3) (The coefficients α in equation (1), β in equation (2), and γ in equation (3) are each between 0.95 and 1.05.)

4. The soft magnetic powder according to claim 1 or 2, wherein the ratio of the C content to the Al content is 0.010 or more and 0.250 or less.

5. The soft magnetic powder according to claim 1 or 2, wherein the Vickers hardness of the cross-section of the particles is 250 or more and 400 or less.

6. A compacted magnetic core characterized by containing the soft magnetic powder described in claim 1 or 2.

7. A magnetic element characterized by comprising a compacted magnetic core as described in claim 6.

8. An electronic device characterized by comprising the magnetic element described in claim 7.

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