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

Abstract

To provide a soft magnetic powder capable of producing a high-density and high-strength molded body while suppressing the amount of binder added during molding, a compacted magnetic core and magnetic element containing such soft magnetic powder, and an electronic device equipped with the magnetic element. [Solution] The material is composed of Fe, Si in an amount of 2.5% to 7.5% by mass, Cr in an amount of 1.0% to 10.0% by mass, and impurities of 1.0% or less by mass, with an average circularity of 0.80 or more and less than 0.95, where D10 is the particle size when the cumulative value from the smallest diameter side in the cumulative particle size distribution curve is 10%, D50 is the particle size when the cumulative value is 50%, and D90 is the particle size when the cumulative value is 90%, the particle size D50 is 3.0 μm to 11.0 μm, the particle size difference D90-D10 is 4.0 μm to 22.0 μm, and the particle size D50 is A [μm] and the specific surface area is B [m²]. 2 A soft magnetic powder in which A × B is between 1.20 and 2.40 when given as [ / g].

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 describes a material composed of Fe as the main component, Si in a content of 2.5% to 6.5% by mass, Cr in a content of 1.0% to 10.0% by mass, S in a content of 0.0020% to 0.0070% by mass, and impurities, with the oxygen content by mass ratio being A [ppm] and the specific surface area being B [m²]. 2 A soft magnetic powder is disclosed in which, when [ / g] is used, the ratio A / B is between 3000 and 8000.

[0003] Such a soft magnetic powder yields a soft magnetic powder with an optimized oxygen content relative to the specific surface area. In other words, if the ratio A / B is within the aforementioned range, a soft magnetic powder with an optimized oxygen content according to particle size can be realized. As a result, a soft magnetic powder is obtained in which the oxide occupancy rate in the compacted powder is suppressed and inter-particle insulation is ensured. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2024-055483 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In the soft magnetic powder described in Patent Document 1, a challenge is to reduce the amount of binder added during molding. If a large amount of binder is added during molding, the density of the molded body decreases, and the magnetic properties of the molded body deteriorate. On the other hand, if the amount of binder added is reduced, the mechanical strength of the molded body decreases. [Means for solving the problem]

[0006] 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 1.0% by mass or more and 10.0% by mass or less, Impurities with a total content of 1.0% by mass or less, Composed of, The average circularity calculated from the particle's area and perimeter is 0.80 or higher and less than 0.95. When the cumulative particle size distribution curve measured by laser diffraction is 10% from the smallest diameter side, the particle size is defined as D10, when the cumulative particle size is 50%, the particle size is defined as D50, and when the cumulative particle size is 90%, the particle size is defined as D90. The particle size D50 is between 3.0 μm and 11.0 μm. The particle size difference D90-D10 between particle size D90 and particle size D10 is between 4.0 μm and 22.0 μm. Let the particle size D50 be A [μm], and the specific surface area be B [m²]. 2 When [ / g] is used, A × B is between 1.20 and 2.40.

[0007] The compacted magnetic core according to an application example of the present invention is This includes a soft magnetic powder according to an example of the application of the present invention.

[0008] 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.

[0009] 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]

[0010] [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] It is a perspective view showing the configuration of a mobile personal computer which is an electronic device according to an embodiment. [Figure 4] It is a plan view showing the configuration of a smartphone which is an electronic device according to an embodiment. [Figure 5] It is a perspective view showing the configuration of a digital still camera which is an electronic device according to an embodiment. [Figure 6] It is Table 1 showing the composition, production conditions and evaluation results of the soft magnetic powders of Sample Nos. 1 to 11. [Figure 7] It is Table 2 showing the composition, production conditions and evaluation results of the soft magnetic powders of Sample Nos. 12 to 18. [Figure 8] It is Table 3 showing the composition, production conditions and evaluation results of the soft magnetic powders of Sample Nos. 19 to 27.

MODE FOR CARRYING OUT THE INVENTION

[0011] Hereinafter, the soft magnetic powder, the compacted magnetic core, the magnetic element and the electronic device according to the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0012] 1. Soft Magnetic Powder The soft magnetic powder according to the embodiment is a metal powder showing soft magnetism. Such a soft magnetic powder can be applied to any use, but for example, it is used to bind particles to each other and manufacture various molded bodies such as a compacted magnetic core and an electromagnetic wave absorber.

[0013] 1.1. Outline The soft magnetic powder according to the embodiment contains Fe (iron) as a 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 1.0 mass% or more and 10.0 mass% or less, and impurities with a total content of 1.0 mass% or less.

[0014] In addition, the soft magnetic powder according to the embodiment satisfies the following four elements (a) to (d). (a) The average circularity calculated from the area and perimeter of the particles is 0.80 or more and less than 0.95.

[0015] (b) When the particle size D50 is defined as the particle size at which the cumulative value from the smallest diameter side reaches 50% in the volume-based integrated particle size distribution curve measured by laser diffraction, the particle size D50 is 3.0 μm or larger and 11.0 μm or smaller.

[0016] (c) In the volume-based cumulative particle size distribution curve measured by laser diffraction, when the cumulative value from the smallest diameter side is 10%, the particle size is defined as D10, and when the cumulative value from the smallest diameter side is 90%, the particle size difference D90-D10 between particle size D90 and particle size D10 is 4.0 μm or more and 22.0 μm or less.

[0017] (d) Let the particle size D50 be A [μm], and the specific surface area be B [m] 2 When [ / g] is used, A × B is between 1.20 and 2.40.

[0018] With this configuration, even if the amount of binder added during molding is kept low, a soft magnetic powder capable of producing high-density and high-strength molded articles can be obtained. In other words, by using the soft magnetic powder according to this embodiment, even if the amount of binder added is suppressed and the packing density of the soft magnetic powder is increased, the decrease in mechanical strength of the manufactured molded article can be suppressed. As a result, it is possible to manufacture molded articles with good magnetic properties that are less prone to defects such as chipping and cracking.

[0019] 1.2.Composition Fe is the main component of soft magnetic powder. The main component refers to the element with the highest atomic ratio. Fe influences the fundamental magnetic properties of soft magnetic powder.

[0020] 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.

[0021] 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 molded body 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 molded body decreases.

[0022] The Cr content is 1.0% by mass or more and 10.0% by mass or less, preferably 1.2% by mass or more and 6.0% by mass or less, and more preferably 1.4% by mass or more and 3.0% by mass or less. When the Cr content is within the above range, the oxidation resistance of the soft magnetic powder is enhanced and the amount of oxide is optimized. This makes it possible to ensure insulation between particles during compaction while improving the weather resistance and spheroidization of the soft magnetic powder. As a result, the magnetic properties during compaction are improved, and a soft magnetic powder capable of producing molded bodies 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, the amount of oxide becomes excessive, and spheroidization is inhibited, so the density of the molded body decreases, and magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density decrease.

[0023] Furthermore, the mass ratio of Si content to Cr content is defined as Si / Cr. The mass ratio Si / Cr is preferably 0.30 to 5.00, more preferably 0.40 to 3.00, and even more preferably 0.60 to 1.00. 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 realize a soft magnetic powder that can produce molded articles with good magnetic properties without reducing the dielectric strength.

[0024] The soft magnetic powder may further contain Al. The Al content is preferably 0.50% by mass or less, more preferably 0.05% by mass or more and 0.40% by mass or less, and even 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 increased, similar to Cr, and the amount of oxide is optimized. This makes it possible to ensure insulation between particles when compacted while increasing the weather resistance of the soft magnetic powder. As a result, the magnetic properties when compacted are improved, and a soft magnetic powder can be realized that can be manufactured to produce molded articles that can withstand high voltages. In addition, if the Al content is within the above range, the surface tension of the molten metal can be reduced, making it easier to make the powder spherical when it is finely pulverized. This makes it possible to obtain a soft magnetic powder that has good packing properties and can be manufactured to produce molded articles with high density and good magnetic properties. Furthermore, if the Al content falls below the aforementioned lower limit, the packing properties, oxidation resistance, and dielectric strength of the soft magnetic powder may 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, which may lead to a decrease in magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density.

[0025] Furthermore, the mass ratio of Al content to Cr content is defined as Al / Cr. The mass ratio Al / Cr is preferably 0.30 or less, more preferably 0.02 to 0.25, and even more preferably 0.04 to 0.20. If the mass ratio Al / Cr is within the above range, the balance between Cr content and Al content can be optimized. This makes it possible to achieve both improved packing properties due to particle shape and improved magnetic properties due to composition optimization. As a result, a molded body with particularly good magnetic properties can be obtained.

[0026] Furthermore, if the mass ratio Al / Cr falls below the lower limit, the insulating properties between particles and the circularity of the particle shape may decrease, potentially leading to a decrease in the density of the molded product. On the other hand, if the mass ratio Al / Cr exceeds the upper limit, the magnetic properties of the compacted powder may decrease.

[0027] The soft magnetic powder may further contain carbon (C). The C content is preferably 0.050% by mass or less, more preferably 0.005% by mass or more and 0.045% by mass or less, and even more preferably 0.015% by mass or more and 0.040% by mass or less. If the C content is within the above range, the hardness of the particles of the soft magnetic powder can be optimized. This makes it possible to obtain a soft magnetic powder that has appropriate fluidity before compaction while exhibiting appropriate deformability during compaction. Such a soft magnetic powder has good packing properties and contributes to the production of molded articles with high density and good magnetic properties. If the C content falls below the lower limit, the particles may not be hard enough, and there is a risk that there will be many irregularly shaped particles before compaction. This may reduce the fluidity of the soft magnetic powder and decrease the packing properties during compaction. On the other hand, if the C content exceeds the upper limit, the particles may be excessively hard. This may decrease the packing properties of the soft magnetic powder during compaction.

[0028] The soft magnetic powder may further contain Sn. The Sn content is preferably 1.10% by mass or less, more preferably 0.05% by mass or more and 0.80% by mass or less, and even more preferably 0.10% by mass or more and 0.40% by mass or less. If the Sn content is within the above range, the particle shape of the soft magnetic powder can be made closer to spherical. This makes it possible to improve the packing of the soft magnetic powder even with a small particle size, and to increase the density of the molded article.

[0029] Furthermore, if the Sn content falls below the aforementioned lower limit, the circularity of the particle shape may decrease, potentially leading to reduced packing efficiency. This may result in a decrease in the density of the molded body, potentially degrading magnetic properties such as permeability and DC superposition characteristics. On the other hand, if the Sn content exceeds the aforementioned upper limit, the soft magnetic powder may become more susceptible to oxidation, potentially increasing the oxygen content. The oxides produced by oxidation reduce the metal occupancy rate in the molded body, leading to a decrease in the density of the molded body and potentially degrading magnetic properties such as permeability and DC superposition characteristics.

[0030] Furthermore, the mass ratio of Sn content to Cr content is defined as Sn / Cr. The mass ratio Sn / Cr is preferably 0.02 to 0.30, more preferably 0.03 to 0.25, and even more preferably 0.04 to 0.20. If the mass ratio Sn / Cr is within the above range, the balance between Cr content and Sn content can be optimized. This makes it possible to achieve both improved packing properties due to particle shape and improved magnetic properties due to composition optimization. As a result, a molded body with particularly good magnetic properties can be obtained.

[0031] Furthermore, if the mass ratio Sn / Cr falls below the lower limit, the oxidation resistance of the soft magnetic powder improves, but the circularity of the particle shape decreases, which may reduce the packing efficiency of the soft magnetic powder. On the other hand, if the mass ratio Sn / Cr exceeds the upper limit, the soft magnetic powder becomes more spherical, but its oxidation resistance decreases, which may reduce the metal content in the molded body.

[0032] 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.

[0033] The impurity content is preferably 0.10% by mass or less for each element, and more preferably 0.05% by mass or less. Furthermore, the total impurity content is preferably 1.0% by mass or less. Within this range, the presence of other elements is acceptable as it does not affect the effects of the soft magnetic powder.

[0034] 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, resulting in a soft magnetic powder with high packing efficiency during compaction. In addition, it suppresses a decrease in the metal occupancy rate in the molded article, resulting in a molded article 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, resulting in a molded article with good dielectric strength.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 1.3. Powder Characteristics As described above, the soft magnetic powder according to the embodiment satisfies the following four elements (a) to (d).

[0040] 1.3.1.(a) Mean circularity The soft magnetic powder according to this embodiment has an average circularity of 0.80 or more and less than 0.95, calculated from the particle area and perimeter.

[0041] With this configuration, the packing density can be sufficiently increased when the soft magnetic powder is compacted. As a result, a soft magnetic powder capable of producing high-density molded bodies can be obtained.

[0042] Furthermore, if the average circularity of the particles falls below the lower limit, the packing efficiency of the soft magnetic powder decreases, and the density of the molded body decreases. On the other hand, if the average circularity of the particles exceeds the upper limit, the difficulty of manufacturing the soft magnetic powder increases. In addition, the interaction between the particles and the binder decreases, which may reduce the compression strength of the molded body.

[0043] The average circularity of the particles is preferably 0.82 to 0.94, and more preferably 0.85 to 0.93.

[0044] Furthermore, the average circularity of the soft magnetic powder particles is measured as follows: 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.

[0045] Next, the circularity of more than 300 particle images is calculated using software. When the circularity is e, the area of ​​the particle image is S, and the perimeter of the particle image is L, the circularity e can be calculated using the following formula.

[0046] e = 4πS / L 2 Next, the average value of the calculated circularity is determined. The resulting average value represents the average circularity of the soft magnetic powder particles.

[0047] 1.3.2.(b) Particle size D50 In the soft magnetic powder according to the embodiment, when the particle size D50 is defined as the cumulative value from the smallest diameter side to 50% in the volume-based cumulative particle size distribution curve measured by laser diffraction, the particle size D50 is 3.0 μm or more and 11.0 μm or less.

[0048] With this configuration, the packing density can be sufficiently increased when the soft magnetic powder is compacted. Furthermore, the mechanical strength of the resulting molded product can be enhanced.

[0049] Furthermore, if the particle size D50 of the soft magnetic powder falls below the lower limit, the soft magnetic powder tends to aggregate, reducing its packing efficiency and decreasing the density and mechanical strength of the molded body. On the other hand, if the particle size D50 of the soft magnetic powder exceeds the upper limit, the gaps between particles increase, reducing packing efficiency and decreasing the density and mechanical strength of the molded body.

[0050] The particle size D50 of the soft magnetic powder is preferably 3.5 μm or more and 10.0 μm or less, and more preferably 4.0 μm or more and 9.0 μm or less.

[0051] Furthermore, a laser diffraction particle size distribution analyzer is used to obtain the integrated particle size distribution curve using the laser diffraction method.

[0052] 1.3.3.(c) Particle size difference D90-D10 In the soft magnetic powder according to the embodiment, when the cumulative value from the smallest diameter side is 10% in the volume-based cumulative particle size distribution curve measured by laser diffraction, the particle size is defined as D10, and when the cumulative value from the smallest diameter side is 90%, the particle size difference D90-D10 between particle size D90 and particle size D10 is 4.0 μm or more and 22.0 μm or less.

[0053] With this configuration, the particle size distribution of the soft magnetic powder is optimized, allowing for a sufficiently high packing density when the soft magnetic powder is compacted. Furthermore, because a denser packing is possible, the mechanical strength of the resulting molded product can be increased.

[0054] Furthermore, if the particle size difference D90-D10 of the soft magnetic powder falls below the lower limit, the particle size difference between large and small particles in the soft magnetic powder decreases, resulting in a decrease in packing efficiency and a decrease in the mechanical strength of the molded body. On the other hand, if the particle size difference D90-D10 of the soft magnetic powder exceeds the upper limit, the particle size difference between large and small particles in the soft magnetic powder increases, resulting in a decrease in packing efficiency and a decrease in mechanical strength.

[0055] Furthermore, the particle size difference D90-D10 is preferably 6.0 μm or more and 20.0 μm or less, and more preferably 8.0 μm or more and 18.0 μm or less.

[0056] 1.3.4.(d) Particle size D50 x specific surface area (A x B) In the soft magnetic powder according to the embodiment, the particle size D50 is A [μm] and the specific surface area is B [m] 2 When [ / g] is used, A × B is between 1.20 and 2.40.

[0057] This configuration optimizes the balance between the particle size D50 and specific surface area of ​​the soft magnetic powder. As a result, even with a reduced amount of binder added during molding, the binder can uniformly cover the surface of the particles, thus suppressing a decrease in the mechanical strength of the molded body. Consequently, the packing density of the soft magnetic powder in the molded body can be increased, thereby improving the magnetic properties of the molded body.

[0058] Furthermore, if the A×B ratio of the soft magnetic powder falls below the lower limit or exceeds the upper limit, the balance between the particle size D50 and specific surface area of ​​the soft magnetic powder becomes poor. This can lead to a decrease in the mechanical strength of the molded body when the amount of binder added is small, or a decrease in the packing density of the soft magnetic powder in the molded body when the amount of binder added is increased.

[0059] Furthermore, the A×B ratio of the soft magnetic powder is preferably 1.30 to 2.30, and more preferably 1.40 to 2.20.

[0060] The specific surface area of ​​soft magnetic powder is obtained by the BET method. An example of a specific surface area measuring device is the HM1201-010 BET-type specific surface area measuring device manufactured by Mountec Co., Ltd., with a sample volume of 5g.

[0061] 1.4. Other characteristics 1.4.1. Compression strength of the molded body When a molded article is obtained using the soft magnetic powder and epoxy resin according to the embodiment, the compression strength of the obtained molded article is preferably 13 MPa or more, more preferably 15 MPa to 50 MPa, and even more preferably 17 MPa to 30 MPa. If the compression strength of the molded article is within the above range, a soft magnetic powder capable of producing a compacted magnetic core with sufficiently high mechanical strength can be realized. In other words, a soft magnetic powder capable of realizing a highly reliable magnetic element in which chipping and cracking are less likely to occur in the compacted magnetic core can be realized.

[0062] Furthermore, if the compression strength of the molded body falls below the lower limit, chipping or cracking may occur in the powdered magnetic core when a magnetic element is used to manufacture it. On the other hand, the compression strength of the molded body may exceed the upper limit, but in that case, the difficulty of manufacturing the powdered magnetic core may increase, or the dimensional accuracy may decrease.

[0063] The compression strength of the molded body is measured as follows. First, epoxy resin equivalent to 2.0% by mass of soft magnetic powder is mixed with the soft magnetic powder, and then the mixture is subjected to 98.1 MPa (1.0 t / cm²). 2 The material is compressed and molded under a pressure of ). Next, the resulting molded body is heat-treated at 600°C for 1 hour in an atmospheric environment. This yields an annular molded body with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. Next, the compression strength of the resulting molded body is measured. The method for measuring the compression strength shall conform to the compression strength test method specified in JIS Z 2507:2000. Specifically, when the compression strength is K, the outer diameter is D, the radial wall thickness (half the difference between the outer and inner diameters) is t, the thickness is L, and the breaking load is F, the compression strength K is given by K = F(Dt) / (Lt). 2 It can be calculated using ).

[0064] 1.4.2. Relative density of the molded body When a molded article is obtained using the soft magnetic powder and epoxy resin according to the embodiment, the relative density of the obtained molded article is preferably 71.0% or more, more preferably 71.5% to 80.0%, and even more preferably 72.0% to 78.0%. If the relative density of the molded article is within the above range, it is possible to realize a soft magnetic powder capable of producing compacted magnetic cores with a sufficiently high packing density and sufficiently high mechanical strength.

[0065] Furthermore, if the relative density of the molded body falls below the lower limit, there is a risk that the packing density and mechanical strength of the soft magnetic powder in the manufactured compacted magnetic core may not be sufficiently increased. On the other hand, the relative density of the molded body may exceed the upper limit, but in that case, there is a risk that the difficulty of manufacturing the soft magnetic powder capable of producing such a molded body will increase.

[0066] The relative density of the molded body is measured as follows. First, an epoxy resin corresponding to 2.0% by mass of the soft magnetic powder and the soft magnetic powder are mixed and compressed and molded at a pressure of 98.1 MPa (1.0 t / cm 2 ). Next, the obtained molded body is heat-treated at 600° C. for 1 hour in an air atmosphere. Thereby, a molded body having an annular shape with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm is obtained. Next, the volume and mass of the obtained molded body are measured. On the other hand, the particle density of the used soft magnetic powder is measured. For the measurement of the particle density, a dry automatic densitometer capable of measuring by the gas displacement method is used. Next, the density of the molded body is calculated from the volume and mass of the molded body, and the relative density of the molded body is calculated from the density of the obtained molded body and the particle density.

[0067] 1.4.3. Tap density of soft magnetic powder The tap density of the soft magnetic powder according to the embodiment is preferably 3.70 g / cm 3 or more and 5.20 g / cm 3 or less, more preferably 3.90 g / cm 3 or more and 5.00 g / cm 3 or less, and even more preferably 4.00 g / cm 3 or more and 4.90 g / cm 3 or less. If the tap density is within the above range, a soft magnetic powder having particularly good filling properties can be obtained. Thereby, a compacted powder magnetic core having high density and good magnetic properties can be manufactured.

[0068] If the tap density is lower than the lower limit value, the filling property of the soft magnetic powder may decrease, and the density of the compacted powder magnetic core may decrease. On the other hand, if the tap density exceeds the upper limit value, the manufacturing difficulty of the soft magnetic powder may increase.

[0069] The tap density of the soft magnetic powder is measured by a powder property evaluation apparatus. Examples of the powder property evaluation apparatus include Powdertester (registered trademark) PT-X manufactured by Hosokawa Micron Corporation.

[0070] 2. Method for manufacturing soft magnetic powder Next, we will describe an example of a method for producing the soft magnetic powder mentioned above.

[0071] 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 soft magnetic powder with particle shapes closer to perfect spheres.

[0072] The atomization method is a method for producing soft magnetic powder by causing molten metal to collide with a liquid or gas sprayed at high speed, thereby miniaturizing and cooling it.

[0073] The water atomization method is a method for producing soft magnetic 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.

[0074] The rotary water atomization method is a method for producing soft magnetic powder by supplying a cooling liquid 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 cooling liquid.

[0075] The gas atomization method is a method for producing soft magnetic 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.

[0076] 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.

[0077] Furthermore, in the water atomization method, as described in International Publication No. WO99 / 11407, for example, water is sprayed at high speed in an inverted cone shape, and molten metal is made to collide with the area near the apex. As a result, a negative pressure is created near the collision point by the water film, which makes the molten metal finer. In addition, oxidation of the molten metal is suppressed, and even if the soft magnetic powder produced is fine, it can be made spherical.

[0078] The apex angle of the injected water (the angle formed inside the apex of the inverted cone) is preferably 3° to 15°, more preferably 5° to 12°, and even more preferably 6° to 10°. If the apex angle of the injected water is within the above range, the pressure near the impact point formed by the water film can be further reduced, and the time it takes for the flowing molten metal to reach the impact point can be increased. As a result, even if the manufactured soft magnetic powder is fine, sufficient spheroidization can be achieved.

[0079] Furthermore, in the water atomization method, for example, as described in International Publication No. WO99 / 11407, the water may be injected into a cylindrical body called an ejector tube. In this case, the pressure inside the ejector tube is more easily reduced, which allows for further refinement of the molten metal while further suppressing oxidation of the molten metal.

[0080] The suction pipe extends downward from the nozzle that sprays water. The length of the suction pipe is preferably 1500 mm to 5000 mm, more preferably 2000 mm to 3500 mm, and even more preferably 2200 mm to 3000 mm. This allows for the efficient production of soft magnetic powder with higher circularity and a smaller specific surface area.

[0081] In the atomization method, molten metal is flowed down through a narrow nozzle opening, and the resulting molten metal stream is made to collide with a fluid jet. The outer diameter of the molten metal stream is not particularly limited, but is preferably 1.0 mm to 6.0 mm, more preferably 1.5 mm to 5.0 mm, and even more preferably 2.0 mm to 4.0 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 a spherical shape can be easily produced regardless of particle size. In addition, the particle size of the soft magnetic powder produced can be adjusted according to the outer diameter of the stream.

[0082] 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.

[0083] 3. Compacted magnetic cores and magnetic elements Next, the compacted magnetic core and magnetic element according to the embodiment will be described.

[0084] 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. Below, we will describe two types of coil components as representative examples of magnetic elements.

[0085] 3.1. Toroidal type First, a toroidal coil component, which is a magnetic element according to the embodiment, will be described.

[0086] Figure 1 is a schematic plan view showing a toroidal type coil component 10. The coil component 10 shown in Figure 1 has a ring-shaped powder core 11 and a conductor 12 wound around this powder core 11.

[0087] The compacted magnetic core 11 is obtained by mixing the soft magnetic powder and binder according to the embodiment and molding the resulting mixture. The compacted magnetic core 11 is a compacted body containing the soft magnetic powder according to the embodiment. Therefore, a high-density and high-strength compacted magnetic core 11 can be obtained. Furthermore, a coil component 10 with high magnetic permeability and high strength can be obtained. When such a coil component 10 is mounted in an electronic device, the performance and miniaturization of the electronic device can be improved.

[0088] 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.

[0089] The materials used to construct the conductor 12 include highly conductive materials, such as metallic materials containing Cu, Al, Ag, Au, Ni, etc. An insulating film may be provided on the surface of the conductor 12 as needed.

[0090] 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, or a shape in which the longitudinal direction is straight.

[0091] Furthermore, the compacted magnetic core 11 may, if necessary, contain soft magnetic powders other than the soft magnetic powder described in the embodiment above, or non-magnetic powders.

[0092] 3.2. Closed Magnetic Circuit Type Next, we will describe a closed-circuit type coil component, which is a magnetic element according to the embodiment. Figure 2 is a schematic transmission perspective view showing a closed magnetic circuit type coil component 20.

[0093] The following description will focus on the differences between the closed-magnetic-circuit type coil component 20 and the toroidal type coil component 10, omitting explanations of similar aspects.

[0094] The coil component 20 shown in Figure 2 is formed by embedding a coil-shaped conductor 22 inside a compacted magnetic core 21. The compacted magnetic core 21 is a compacted body containing soft magnetic powder according to the embodiment. As a result, a high-density and high-strength compacted magnetic core 21 can be obtained. Furthermore, a coil component 20 with high magnetic permeability and high strength can be obtained. When such a coil component 20 is mounted in electronic equipment, the performance and miniaturization of the electronic equipment can be improved.

[0095] The compacted magnetic core 21 may, if necessary, contain soft magnetic powders other than the soft magnetic powder described in the above embodiment, or non-magnetic powders.

[0096] 4.Electronic equipment An electronic device equipped with a magnetic element according to this embodiment will be described with reference to Figures 3 to 5.

[0097] Figure 3 is a perspective view showing the configuration of a mobile personal computer 1100, 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.

[0098] Figure 4 is a plan view showing the configuration of a smartphone 1200, 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.

[0099] Figure 5 is a perspective view showing the configuration of a digital still camera 1300, which is an electronic device according to the embodiment. The digital still camera 1300 generates an imaging signal by photoelectric conversion of the light image of the subject using an image sensor such as a CCD (Charge Coupled Device).

[0100] 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.

[0101] 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.

[0102] Examples of electronic devices according to this embodiment include, in addition to the personal computer 1100 in Figure 3, the smartphone 1200 in Figure 4, and the digital still camera 1300 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.

[0103] Such electronic devices are equipped with magnetic elements according to the embodiment. This allows for the enjoyment of the effects of the magnetic elements, thereby improving the performance and miniaturization of the electronic devices.

[0104] 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 1.0% to 10.0% by mass, and impurities with a total content of 1.0% by mass or less. Furthermore, in the soft magnetic powder according to the embodiment, the average circularity calculated from the particle area and perimeter is 0.80 or more and less than 0.95. Moreover, in the soft magnetic powder according to the embodiment, when the particle size is defined as D10 when the cumulative value from the smallest diameter side is 10% in the volume-based cumulative particle size distribution curve measured by laser diffraction, the particle size is defined as D50 when the cumulative value from the smallest diameter side is 50%, and the particle size is defined as D90 when the cumulative value from the smallest diameter side is 90%, the particle size D50 is 3.0 μm or more and 11.0 μm or less, and the particle size difference D90-D10 between particle size D90 and particle size D10 is 4.0 μm or more and 22.0 μm or less. Furthermore, in the soft magnetic powder according to the embodiment, the particle size D50 is A [μm] and the specific surface area is B [m] 2When [ / g] is used, A × B is between 1.20 and 2.40.

[0105] This configuration makes it possible to create a soft magnetic powder that allows for the production of high-density and high-strength molded bodies while suppressing the amount of binder added during molding.

[0106] In the soft magnetic powder according to this embodiment, epoxy resin is mixed in a ratio of 2.0% by mass, and the pressure is 98.1 MPa (1.0 t / cm²). 2 When molded into an annular shape with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm under the pressure of ), it is preferable that the resulting molded body has a compression ring strength of 13 MPa or higher.

[0107] This configuration makes it possible to create soft magnetic powder capable of manufacturing compacted magnetic cores with sufficiently high mechanical strength. In other words, it is possible to create soft magnetic powder that is less prone to chipping or cracking of the compacted magnetic core, enabling the creation of highly reliable magnetic elements.

[0108] In the soft magnetic powder according to the embodiment, it is preferable that the relative density of the molded body described above is 71.0% or higher.

[0109] With this configuration, it is possible to realize a soft magnetic powder that has a sufficiently high packing density and also possesses sufficiently high mechanical strength, enabling the production of compacted magnetic cores.

[0110] In the soft magnetic powder according to the embodiment, the tap density is 3.70 [g / cm³]. 3 ] or more than 5.20[g / cm 3 It is preferable that it be less than or equal to the following:

[0111] This configuration yields a soft magnetic powder with particularly good packing properties. This makes it possible to manufacture compacted magnetic cores with high density and good magnetic properties.

[0112] The compacted magnetic core according to the embodiment contains the soft magnetic powder according to the embodiment. This configuration yields a high-density and high-strength compacted magnetic core.

[0113] The magnetic element according to the embodiment comprises a compacted magnetic core according to the embodiment. This configuration allows for the creation of magnetic elements with high permeability and high strength.

[0114] 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.

[0115] 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]

[0116] Next, specific embodiments of the present invention will be described. 6. Manufacturing of soft magnetic powder Figure 6 is Table 1, showing the composition, manufacturing conditions, and evaluation results of soft magnetic powders for samples No. 1 to 11. Figure 7 is Table 2, showing the composition, manufacturing conditions, and evaluation results of soft magnetic powders for samples No. 12 to 18. Figure 8 is Table 3, showing the composition, manufacturing conditions, and evaluation results of soft magnetic powders for samples No. 19 to 27.

[0117] 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 for the soft magnetic powder by the water atomization method are also shown in Table 1.

[0118] Furthermore, the particle size D10, particle size D50(A), particle size D90, particle size difference D90-D10, specific surface area (B), A×B, and average circularity of the obtained soft magnetic powder were measured or calculated. The measurement and calculation results are shown in Table 1.

[0119] 6.2. Samples No. 2-27 Soft magnetic powder was obtained in the same manner as Sample No. 1, except that the composition of the soft magnetic powder was changed as shown in Table 1 (Figure 6), Table 2 (Figure 7), or Table 3 (Figure 8).

[0120] In Tables 1, 2, and 3, 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."

[0121] 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, 2, and 3.

[0122] A: Tap density is 4.00 g / cm³ 3 More than 4.90g / cm 3 The following is B: Tap density is 3.70 g / cm³ 3 More than 5.20g / cm 3 The following applies (excluding range A): C: Tap density is 3.70 g / cm³ 3 Less than 5.20 g / cm³ 3 It is super

[0123] 7.2. Relative density of molded bodies of soft magnetic powder For each sample No. of soft magnetic powder, compaction molding was performed, and the relative density of the resulting molded body was measured. 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, 2, and 3.

[0124] A: The relative density of the molded product is between 72.0% and 78.0%. B: The relative density of the molded product is 71.0% or more and less than 72.0%, or greater than 78.0% and less than or equal to 80.0%. C: The relative density of the molded product is less than 71.0% or greater than 80.0%.

[0125] 7.3. Pressure ring strength of molded bodies of soft magnetic powder For each sample No. of soft magnetic powder, compaction molding was performed, and the compression strength of the resulting molded body was measured. 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, 2, and 3.

[0126] A: The compression strength of the molded product is between 17 MPa and 30 MPa. B: The compression strength of the molded body is 13 MPa or more and less than 17 MPa, or greater than 30 MPa and less than or equal to 50 MPa. C: The compression strength of the molded product is less than 13 MPa or greater than 50 MPa.

[0127] As shown in Tables 1, 2, and 3, the soft magnetic powders of each example were found to have high packing properties, enabling the production of high-density and high-strength molded articles. Therefore, it was found that highly permeable and reliable magnetic elements can be manufactured using the soft magnetic powder according to the present invention.

[0128] Furthermore, when the amount of epoxy resin used was reduced by 10% and the same evaluation was performed, the evaluation results were the same as those in Table 1. Specifically, when molded bodies were prepared using soft magnetic powders No. 1 to 11 and the compression strength was measured, the evaluation results were the same as those in Table 1. Therefore, it was confirmed that good results can be obtained even when the amount of binder added during molding is reduced by using the soft magnetic powder according to the present invention. [Explanation of symbols]

[0129] 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 1.0% by mass or more and 10.0% by mass or less, Impurities with a total content of 1.0% by mass or less, It consists of, The average circularity calculated from the particle's area and perimeter is 0.80 or higher and less than 0.

95. When the cumulative particle size distribution curve measured by laser diffraction is 10% from the smallest diameter side, the particle size is defined as D10, when the cumulative particle size is 50%, the particle size is defined as D50, and when the cumulative particle size is 90%, the particle size is defined as D90. The particle size D50 is 3.0 μm or more and 11.0 μm or less. The particle size difference D90-D10 between particle size D90 and particle size D10 is 4.0 μm or more and 22.0 μm or less. Let the particle size D50 be A [μm], and the specific surface area be B [m²]. ２ A soft magnetic powder characterized in that, when [ / g], A × B is 1.20 or more and 2.40 or less.

2. The epoxy resin is mixed to a ratio of 2.0% by mass, and the pressure is 98.1 MPa (1.0 t / cm²). ２ The soft magnetic powder according to claim 1, wherein when formed into an annular shape with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm under the pressure of ), the resulting molded body has a compression ring strength of 13 MPa or more.

3. The soft magnetic powder according to claim 2, wherein the relative density of the molded body is 71.0% or more.

4. The tap density is 3.70 [g / cm³]. ３ ] or more 5.20 [g / cm ３ The soft magnetic powder according to claim 1 or 2, which is as follows:

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

6. A magnetic element characterized by comprising a compacted magnetic core as described in claim 5.

7. An electronic device characterized by comprising the magnetic element described in claim 6.

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