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

Abstract

This invention provides a soft magnetic powder that suppresses the amount of binder added during molding and enables the production of high-density and high-strength molded bodies; a pressed magnetic core and magnetic element containing such a soft magnetic powder; and an electronic device equipped with the aforementioned magnetic element. The soft magnetic powder is composed of Fe, 2.5% by mass or more and 7.5% by mass or less Si, 1.0% by mass or more and 10.0% by mass or less Cr, and 1.0% by mass or less impurities. Its average roundness is 0.80 or more and less than 0.95. In a cumulative particle size distribution curve, when the particle size at 10% cumulative value from the small diameter side is defined as D10, the particle size at 50% cumulative value is defined as D50, and the particle size at 90% cumulative value is defined as D90, the particle size D50 is 3.0 μm or more and 11.0 μm or less, and the particle size difference D90-D10 is 4.0 μm or more and 22.0 μm or less. The particle size D50 is defined as A [μm], and the specific surface area is defined as B [m²]. 2 When / g], A×B is greater than 1.20 and less than 2.40.

Description

Technical Field

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

[0002] Patent Document 1 discloses a soft magnetic powder comprising 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. The oxygen content by mass ratio is defined as A [ppm], and the specific surface area is defined as B [m²]. 2 When / g], the ratio of A / B is above 3000 and below 8000.

[0003] Based on this soft magnetic powder, a soft magnetic powder with an optimized ratio of oxygen content to specific surface area was obtained. In other words, as long as the ratio A / B is within the above-mentioned range, a soft magnetic powder with an optimized oxygen content corresponding to the particle size can be obtained. As a result, a soft magnetic powder that suppresses the occupancy of oxides in the pressed powder and ensures interparticle insulation is obtained.

[0004] Patent Document 1: Japanese Patent Application Publication No. 2024-055483 In the soft magnetic powder described in Patent Document 1, controlling the amount of binder added during molding has become a problem. When a large amount of binder is added during molding, the density of the molded body decreases, and the magnetic properties of the molded body also decrease. On the other hand, if the amount of binder added is controlled, the mechanical strength of the molded body decreases. Summary of the Invention

[0005] The soft magnetic powder involved in the application example of the present invention is composed of Fe as the main component, Si with a content of 2.5% to 7.5% by mass, Cr with a content of 1.0% to 10.0% by mass, and impurities with a total content of 1.0% by mass or less. The average roundness calculated based on the area and perimeter of the particles is 0.80 or more and less than 0.95. In the cumulative particle size distribution curve based on volume measured by laser diffraction, from... When the cumulative value from the small diameter side is 10%, the particle size is defined as D10; when the cumulative value from the small diameter side is 50%, the particle size is defined as D50; and when the cumulative value from the small 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 between particle size D90 and particle size D10, D90-D10, is 4.0 μm or more and 22.0 μm or less, then particle size D50 is defined as A [μm], and specific surface area is defined as B [m²]. 2 When / g], A×B is greater than 1.20 and less than 2.40.

[0006] The pressed powder magnetic core involved in the application examples of the present invention includes the soft magnetic powder involved in the application examples of the present invention.

[0007] The magnetic element involved in the application example of the present invention has the powder core involved in the application example of the present invention.

[0008] The electronic device described in the application examples of the present invention includes the magnetic element described in the application examples of the present invention. Attached Figure Description

[0009] Figure 1 This is a schematic top view showing a ring-shaped coil component.

[0010] Figure 2 It is a schematic perspective view of a coil component with a closed magnetic circuit.

[0011] Figure 3 This is a perspective view showing the structure of the electronic device involved in the implementation, namely a mobile personal computer.

[0012] Figure 4 This is a top view showing the structure of the electronic device involved in the implementation, namely a smartphone.

[0013] Figure 5 This is a perspective view showing the structure of the electronic device involved in the implementation, namely a digital camera.

[0014] Figure 6 Table 1 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 1 to 11.

[0015] Figure 7 Table 2 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 12 to 18.

[0016] Figure 8 Table 3 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 19 to 27.

[0017] Explanation of reference numerals in the attached figures 10: Coil component; 11: Powder core; 12: Wire; 20: Coil component; 21: Powder core; 22: Wire; 100: Display unit; 1000: Magnetic element; 1100: Personal computer; 1102: Keyboard; 1104: Main body; 1106: Display unit; 1200: Smartphone; 1202: Operation button; 1204: Earpiece; 1206: Microphone; 1300: Digital camera; 1302: Housing; 1304: Light receiving unit; 1306: Shutter button; 1308: Memory. Detailed Implementation

[0018] Hereinafter, the soft magnetic powder, pressed magnetic core, magnetic element, and electronic device involved in the present invention will be described in detail based on the preferred embodiments shown in the accompanying drawings.

[0019] 1. Soft magnetic powder The soft magnetic powder involved in the embodiments is a metal powder that exhibits soft magnetism. Such soft magnetic powder can be applied to any purpose, such as in the manufacture of various molded articles, such as bonding particles together to produce pressed magnetic cores and electromagnetic wave absorbing materials.

[0020] 1.1.Overview The soft magnetic powder involved in the embodiment is composed of Si (silicon) with Fe (iron) as the main component and a content of 2.5% to 7.5% by mass, Cr (chromium) with a content of 1.0% to 10.0% by mass, and impurities with a total content of 1.0% by mass or less.

[0021] Furthermore, the soft magnetic powder involved in the implementation method satisfies the following four elements (a) to (d).

[0022] (a) The average roundness calculated based on the area and perimeter of the particle is greater than 0.80 and less than 0.95.

[0023] (b) In the cumulative particle size distribution curve of the volume reference determined by laser diffraction, when the particle size at which the cumulative value from the small diameter side is 50% is set as D50, the particle size D50 is 3.0 μm or more and 11.0 μm or less.

[0024] (c) In the cumulative particle size distribution curve of the volume reference determined by laser diffraction, when the particle size at the cumulative value of 10% from the small diameter side is set as D10 and the particle size at the cumulative value of 90% from the small diameter side is set as D90, the particle size difference D90-D10 between particle size D90 and particle size D10 is greater than 4.0 μm and less than 22.0 μm.

[0025] (d) When the particle size D50 is set to A [μm] and the specific surface area is set to B [m²], 2 When / g], A×B is greater than 1.20 and less than 2.40.

[0026] Based on this configuration, a soft magnetic powder is obtained that can produce high-density and high-strength molded articles even when the amount of binder added during molding is kept low. In other words, by using the soft magnetic powder according to the embodiment, even when the amount of binder added is suppressed and the volume ratio of the soft magnetic powder is increased in the manufactured molded article, the reduction in mechanical strength can be suppressed. As a result, it is possible to manufacture molded articles with good magnetic properties and that are not prone to defects, cracks, or other adverse conditions.

[0027] 1.2. Composition Fe is the main component of soft magnetic powder. The main component refers to the element with the highest atomic percentage. Fe influences the basic magnetic properties of soft magnetic powder.

[0028] The Fe content is not particularly limited, but it is preferably 80.0% by mass or more, and more preferably 85.0% by mass or more.

[0029] 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. As long as the Si content is within the above range, a molded article with higher magnetic permeability can be obtained. Furthermore, if the Si content is below the lower limit, magnetic properties such as magnetic permeability and DC superposition characteristics decrease. On the other hand, if the Si content exceeds the upper limit, the soft magnetic powder hardens, reducing its filling capacity, and therefore, the density of the molded article decreases.

[0030] The Cr content is 1.0% by mass or more and 10.0% by mass or less, but 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. As long as the Cr content is within the above range, the oxidation resistance of the soft magnetic powder is improved and the amount of oxides is optimized. This improves the durability of the soft magnetic powder and the spheroidization of the particles, and ensures interparticle insulation during powder pressing. As a result, improved magnetic properties during powder pressing are achieved, and soft magnetic powder capable of producing molded bodies that can withstand high voltages can be manufactured. However, if the Cr content is 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 oxides becomes excessive and hinders spheroidization, thus reducing the density of the molded body and decreasing magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density.

[0031] Furthermore, the mass ratio of Si content to Cr content is defined as Si / Cr. The Si / Cr mass ratio is preferably 0.30 or more and 5.00 or less, more preferably 0.40 or more and 3.00 or less, and even more preferably 0.60 or more and 1.00 or less. As long as the Si / Cr mass ratio is within the above range, the balance between the Si and Cr content can be optimized. This allows for the production of soft magnetic powders capable of manufacturing molded bodies with good magnetic properties without reducing voltage withstand capability.

[0032] The soft magnetic powder may also 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. As long as the Al content is within the above range, spheroidization of the soft magnetic powder can be achieved. Furthermore, as with Cr, the oxidation resistance of the soft magnetic powder is improved and the oxide content is optimized when the Al content is within the above range. This improves the durability of the soft magnetic powder and ensures interparticle insulation during calendering. As a result, improved magnetic properties during calendering and the ability to manufacture molded bodies capable of withstanding high voltages are achieved. Furthermore, as long as the Al content is within the above range, the surface tension of the molten metal is reduced, thus spheroidization during micronization is easier. This results in a soft magnetic powder with good filling properties that can be used to manufacture molded bodies with high density and good magnetic properties. However, if the Al content is below the above lower limit, the filling properties, oxidation resistance, and voltage withstand capability of the soft magnetic powder during calendering may decrease. On the other hand, if the content of Al exceeds the above-mentioned upper limit, the amount of Fe will be relatively reduced and the amount of oxides will become excessive, and magnetic properties such as permeability, DC superposition characteristics, and saturation magnetic flux density may be reduced.

[0033] Furthermore, the mass ratio of Al content to Cr content is set as Al / Cr. The mass ratio Al / Cr is preferably 0.30 or less, more preferably 0.02 or more and 0.25 or less, and even more preferably 0.04 or more and 0.20 or less. As long as the mass ratio Al / Cr is within the above range, the balance between the Cr content and the Al content can be optimized. This allows for both improved filling properties based on particle shape and improved magnetic properties based on composition optimization. As a result, a molded article with particularly good magnetic properties is obtained.

[0034] Furthermore, if the Al / Cr mass ratio is lower than the aforementioned lower limit, the interparticle insulation and particle sphericity will decrease, potentially reducing the density of the molded body. On the other hand, if the Al / Cr mass ratio exceeds the aforementioned upper limit, the magnetic properties during powder pressing may decrease.

[0035] The soft magnetic powder may also 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. As long as the C content is within the above range, the hardness of the soft magnetic powder particles can be optimized. This results in a soft magnetic powder that ensures adequate flowability before pressing and exhibits adequate deformability during pressing. Such a soft magnetic powder, due to its good filling properties, facilitates the manufacture of high-density molded articles with good magnetic properties. However, if the C content is below the lower limit, the particle hardness may be insufficient, leading to an increase in irregularly shaped particles during the pre-pressing stage. Therefore, the flowability of the soft magnetic powder may decrease, and the filling properties during pressing may decrease. On the other hand, if the C content exceeds the upper limit, the particle hardness may become excessive. Therefore, the filling properties of the soft magnetic powder during pressing may decrease.

[0036] The soft magnetic powder may also 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. As long as the Sn content is within the above range, the particle shape of the soft magnetic powder can be made closer to spherical. Therefore, even with a small particle size, the filling properties of the soft magnetic powder can be improved, and the density of the molded article can be increased.

[0037] Furthermore, if the Sn content is below the aforementioned lower limit, the sphericity of the particles decreases, and the filling properties may be reduced. This leads to a decrease in the density of the molded body, and potentially a reduction in 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 is more prone to oxidation, and the oxygen content may increase. The oxides generated during oxidation reduce the metal content in the molded body, thus leading to a decrease in the density of the molded body, and potentially a reduction in magnetic properties such as permeability and DC superposition characteristics.

[0038] Furthermore, the mass ratio of Sn content to Cr content is set as Sn / Cr. The Sn / Cr mass ratio is preferably 0.02 or more and 0.30 or less, more preferably 0.03 or more and 0.25 or less, and even more preferably 0.04 or more and 0.20 or less. As long as the Sn / Cr mass ratio is within the above range, the balance between the Cr and Sn contents can be optimized. This allows for both improved filling properties based on particle shape and improved magnetic properties based on composition optimization. As a result, a molded article with particularly good magnetic properties is obtained.

[0039] Furthermore, if the Sn / Cr mass ratio is lower than the aforementioned lower limit, although the oxidation resistance of the soft magnetic powder is improved, the sphericity of the particle shape decreases, and the filling capacity of the soft magnetic powder may be reduced. On the other hand, if the Sn / Cr mass ratio exceeds the aforementioned upper limit, although sphericity of the soft magnetic powder is achieved, the oxidation resistance decreases, and the metal content in the molded body may be reduced.

[0040] Soft magnetic powders may contain other elements as impurities in addition to the elements mentioned above. Impurities refer to elements that are unavoidably mixed in, other than those mentioned above.

[0041] The content of impurities is preferably 0.10% by mass or less for each element, more preferably 0.05% by mass or less. Furthermore, the total content of impurities is preferably 1.0% by mass or less. Moreover, as long as it is within this range, the presence of other elements will not affect the effect of the soft magnetic powder, therefore, their presence is permissible.

[0042] Furthermore, the soft magnetic powder involved in the embodiments may also contain oxygen as an impurity. The oxygen content of the soft magnetic powder is preferably 3000 ppm or less by mass ratio, more preferably 2000 ppm or less, and even more preferably 1500 ppm or less. This suppresses the deterioration of particle shape caused by oxide surface adhesion, thus obtaining a soft magnetic powder with high filling capacity during pressing. Furthermore, it suppresses the reduction of metal occupancy in the molded article, thus obtaining a molded article with good magnetic properties. On the other hand, a lower limit value may not be set, but from the viewpoint of ensuring inter-particle insulation, the lower limit value of the oxygen content is preferably 300 ppm or more, more preferably 500 ppm or more. This sufficiently ensures inter-particle insulation, resulting in a molded article with good voltage resistance.

[0043] The above components were determined using the following analytical method.

[0044] 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; fluorescence X-ray analysis for iron and steel as specified in JIS G 1256:1997; and gravimetric, titration, and absorbance spectrophotometric methods as specified in JIS G 1211 to G 1237.

[0045] Specifically, examples include the solid-state emission spectrometer manufactured by SPECTRO Corporation, particularly the spark discharge emission spectrometer, model: SPECTROLAB, type: LAMVB08A, and the ICP device CIROS120 manufactured by Rigaku Corporation.

[0046] Furthermore, particularly in the determination of C (carbon) and S (sulfur), the oxygen flow combustion (high-frequency induction furnace combustion)-infrared absorption method specified in JIS G 1211:2011 can also be used. Specifically, examples include the LECO carbon and sulfur analysis apparatus, CS-200.

[0047] Furthermore, particularly in the determination of N (nitrogen) and O (oxygen), the quantitative methods for iron and steel-nitrogen as specified in JIS G 1228:1997 and the general rules for the quantitative methods of oxygen in metallic materials as specified in JIS Z 2613:2006 can also be used. Specifically, examples include LECO's oxygen and nitrogen analysis devices, TC-300 / EF-300, LECO's oxygen, nitrogen, and hydrogen analysis devices, and ONH836.

[0048] 1.3.Powder characteristics The soft magnetic powder involved in the implementation method, as described above, satisfies the following four elements (a) to (d).

[0049] 1.3.1. (a) Average roundness The soft magnetic powder involved in the implementation method has an average roundness of 0.80 or more and less than 0.95, calculated based on the area and perimeter of the particles.

[0050] Based on this configuration, the filling rate is significantly improved during the pressing of the soft magnetic powder. Therefore, a soft magnetic powder capable of manufacturing high-density molded articles is obtained.

[0051] Furthermore, if the average sphericity of the particles is below the aforementioned lower limit, the filling properties of the soft magnetic powder decrease, and the density of the molded article decreases. On the other hand, if the average sphericity of the particles exceeds the aforementioned upper limit, the manufacturing difficulty of the soft magnetic powder increases. In addition, the interaction between the particles and the binder decreases, and the ring compression strength of the molded article may decrease.

[0052] In addition, the average roundness of the particles is preferably 0.82 or higher and 0.94 or lower, more preferably 0.85 or higher and 0.93 or lower.

[0053] In addition, the average roundness of the soft magnetic powder particles was determined as follows.

[0054] First, images of the soft magnetic powder (secondary electron images) are captured using a scanning electron microscope (SEM). Next, the obtained images are imported into image processing software. Image processing software such as "Mac-View," an image resolution particle size distribution measurement software manufactured by Mounttech Co., Ltd., is used. Furthermore, the magnification is adjusted so that 50 to 100 particles are displayed in a single image. Then, multiple images are acquired to obtain a total of more than 300 particle images.

[0055] Next, the software is used to calculate the roundness of more than 300 particle images. With roundness set as e, the area of ​​the particle image as S, and the perimeter of the particle image as L, the roundness e is calculated using the following formula.

[0056] e = 4πS / L 2 Next, the average value of the calculated roundness is determined. The obtained average value becomes the average roundness of the soft magnetic powder particles.

[0057] 1.3.2.(b)Particle size D50 For the soft magnetic powder involved in the embodiment, in the cumulative particle size distribution curve based on volume measured by laser diffraction, when the particle size at which the cumulative value from the small diameter side is 50% is set as D50, the particle size D50 is 3.0 μm or more and 11.0 μm or less.

[0058] Based on this configuration, the filling rate is significantly improved when the soft magnetic powder is pressed. Furthermore, the mechanical strength of the resulting molded article is enhanced.

[0059] Furthermore, if the particle size D50 of the soft magnetic powder is lower than the aforementioned lower limit, the soft magnetic powder is prone to agglomeration, reducing its filling capacity and thus 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 aforementioned upper limit, the gaps between particles increase, thus reducing the filling capacity and thus decreasing the density and mechanical strength of the molded body.

[0060] In addition, the particle size D50 of the soft magnetic powder is preferably 3.5 μm or more and 10.0 μm or less, more preferably 4.0 μm or more and 9.0 μm or less.

[0061] In addition, the cumulative particle size distribution curve based on laser diffraction was obtained using a laser diffraction particle size distribution measuring device.

[0062] 1.3.3.(c)Particle size difference D90-D10 For the soft magnetic powder involved in the embodiment, in the cumulative particle size distribution curve based on volume measured by laser diffraction, the particle size when the cumulative value from the small diameter side is 10% is set as D10, and the particle size when the cumulative value from the small diameter side is 90% is set as D90. 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.

[0063] This configuration optimizes the particle size distribution of the soft magnetic powder, thus significantly increasing the filling rate during powder compaction. Furthermore, it allows for denser filling, thereby improving the mechanical strength of the resulting molded article.

[0064] Furthermore, if the particle size difference D90-D10 of the soft magnetic powder is lower than the aforementioned lower limit, the particle size difference between the large-diameter and small-diameter particles of the soft magnetic powder is small, thus reducing the filling rate and decreasing the mechanical strength of the molded article. On the other hand, if the particle size difference D90-D10 of the soft magnetic powder exceeds the aforementioned upper limit, the particle size difference between the large-diameter and small-diameter particles of the soft magnetic powder is large, thus reducing the filling rate and decreasing the mechanical strength.

[0065] Furthermore, the particle size difference D90-D10 is preferably 6.0 μm or more and 20.0 μm or less, more preferably 8.0 μm or more and 18.0 μm or less.

[0066] 1.3.4. (d) Particle size D50 × specific surface area (A × B) For the soft magnetic powder involved in the embodiment, the particle size D50 is set as A [μm], and the specific surface area is set as B [m²]. 2 When / g], A×B is greater than 1.20 and less than 2.40.

[0067] This configuration optimizes the balance between the particle size D50 and specific surface area of ​​the soft magnetic powder. Therefore, even with a small amount of binder added during molding, the binder can uniformly cover the particle surface, thus preventing a decrease in the mechanical strength of the molded article. As a result, the occupancy rate of the soft magnetic powder in the molded article can be increased, thereby improving the magnetic properties of the molded article.

[0068] Furthermore, when the A×B of the soft magnetic powder is lower than the lower limit or higher than the upper limit, the balance between the particle size D50 and the specific surface area of ​​the soft magnetic powder deteriorates. Therefore, when the amount of binder added is small, the mechanical strength of the molded body decreases, or the amount of binder added needs to be increased to reduce the proportion of soft magnetic powder in the molded body.

[0069] In addition, the A×B ratio of the soft magnetic powder is preferably 1.30 or more and 2.30 or less, and more preferably 1.40 or more and 2.20 or less.

[0070] The specific surface area of ​​the soft magnetic powder was obtained by the BET method. For example, the BET-type specific surface area measuring device HM1201-010 manufactured by Mounttech Co., Ltd. was used to measure the specific surface area, with a sample weight of 5g.

[0071] 1.4. Other characteristics 1.4.1. Ring strength of the molded body When obtaining a molded article using the soft magnetic powder and epoxy resin described in the embodiments, the ring strength of the obtained molded article is preferably 13 MPa or more, more preferably 15 MPa or more and 50 MPa or less, and even more preferably 17 MPa or more and 30 MPa or less. As long as the ring strength of the molded article is within the above range, it is possible to obtain soft magnetic powder capable of manufacturing pressed powder magnetic cores with sufficiently high mechanical strength. In other words, pressed powder magnetic cores are less prone to defects, cracks, etc., and soft magnetic powder capable of producing magnetic components with high reliability can be obtained.

[0072] Furthermore, if the ring strength of the molded body is lower than the aforementioned lower limit, the pressed powder core may suffer defects or breakage when using magnetic components to manufacture it. On the other hand, the ring strength of the molded body can also exceed the aforementioned upper limit, but in this case, the manufacturing difficulty of the pressed powder core may increase, or the dimensional accuracy may decrease.

[0073] In addition, the ring strength of the molded body is measured as follows.

[0074] First, epoxy resin and soft magnetic powder, equivalent to 2.0% by mass of the soft magnetic powder, are mixed and subjected to a pressure of 98.1 MPa (1.0 t / cm). 2 The ring is formed by compression under pressure. Next, the resulting molded body is heat-treated at 600°C for 1 hour in an atmospheric environment. This yields a ring-shaped molded body with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. The ring strength of the resulting molded body is then measured. The ring strength is measured according to the method specified in JIS Z2507:2000. Specifically, when the ring strength is set as K, the outer diameter as D, the radial wall thickness (half the difference between the outer and inner diameters) as t, the thickness as L, and the breaking load as F, the ring strength K is determined by K = F(Dt) / (Lt). 2 Find the answer.

[0075] 1.4.2. Relative density of the molded body When obtaining a molded article using the soft magnetic powder and epoxy resin described in the embodiments, the relative density of the obtained molded article is preferably 71.0% or more, more preferably 71.5% or more and 80.0% or less, and even more preferably 72.0% or more and 78.0% or less. As long as the relative density of the molded article is within the above range, the volume fraction of the soft magnetic powder is sufficiently high, and it is possible to manufacture a soft magnetic powder that can produce a pressed magnetic core with sufficiently high mechanical strength.

[0076] Furthermore, if the relative density of the molded body is lower than the aforementioned lower limit, the volume fraction and mechanical strength of the soft magnetic powder in the manufactured pressed magnetic core may not be sufficiently increased. On the other hand, the relative density of the molded body may exceed the aforementioned upper limit, but in this case, the difficulty of manufacturing the soft magnetic powder capable of producing such a molded body may increase.

[0077] In addition, the relative density of the molded body is measured as follows.

[0078] First, epoxy resin and soft magnetic powder, equivalent to 2.0% by mass of the soft magnetic powder, are mixed and subjected to a pressure of 98.1 MPa (1.0 t / cm). 2 The material is compressed under pressure to form a ring. Next, the resulting ring is heat-treated at 600°C for 1 hour in an atmospheric environment. This yields a ring-shaped ring with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm. The volume and mass of the resulting ring are then measured. Simultaneously, the particle density of the soft magnetic powder used is measured. The particle density is measured using a dry automatic density meter capable of gas displacement-based measurements. The density of the ring is calculated based on its volume and mass, and the relative density of the ring is calculated based on the density of the ring and the particle density.

[0079] 1.4.3. Tap density of soft magnetic powder The tap density of the soft magnetic powder involved in the embodiment is preferably 3.70 g / cm³. 3 Above and 5.20 g / cm 3 The preferred value is 3.90 g / cm³. 3 Above and 5.00 g / cm 3 The following is a further preferred value: 4.00 g / cm³ 3 Above and 4.90 g / cm 3 The following applies. As long as the tap density is within the above range, a soft magnetic powder with particularly good filling properties is obtained. Therefore, it is possible to manufacture high-density powder-pressed magnetic cores with excellent magnetic properties.

[0080] Furthermore, if the tap density is lower than the aforementioned lower limit, the filling properties of the soft magnetic powder will decrease, and the density of the pressed magnetic core may decrease. On the other hand, if the tap density exceeds the aforementioned upper limit, the manufacturing difficulty of the soft magnetic powder may increase.

[0081] The tap density of soft magnetic powders is determined using a powder property evaluation device. An example of such a device is the Hosokawa Micron PT-X Powder Tester (registered trademark).

[0082] 2. Method for manufacturing soft magnetic powder Next, an example of the aforementioned method for manufacturing soft magnetic powder will be described.

[0083] Soft magnetic powder can be manufactured by any method. Examples of manufacturing methods include various atomization methods such as water atomization, rotating water atomization, and gas atomization, as well as pulverization. Among these, powder manufactured by atomization is preferred for soft magnetic powder. According to atomization, soft magnetic powder with a particle shape closer to spherical can be manufactured efficiently.

[0084] Atomization is a method of manufacturing soft magnetic powder by colliding molten metal with a high-speed jet of liquid or gas, thereby miniaturizing and cooling it.

[0085] Water atomization is a method that uses liquids such as water as coolants, sprays them into an inverted cone shape that converges to a single point, and causes molten metal to flow down toward and collide with this convergence point, thereby producing soft magnetic powder from the molten metal.

[0086] The rotating water jet atomization method is a method of producing soft magnetic powder by supplying coolant along the inner circumferential surface of a cooling cylinder, causing it to rotate along the inner circumferential surface, and by blowing a jet of liquid or gas into the molten metal, thereby capturing the scattered molten metal into the coolant.

[0087] Gas atomization is a method of producing soft magnetic powder by using gas as a cooling medium, spraying it into an inverted cone shape that converges to a single point, and causing molten metal to flow down toward and collide with this convergence point.

[0088] Regarding the melting point Tm [°C] of the constituent materials of the soft magnetic powder, the casting temperature of the melting point is preferably set to Tm + 200°C or higher, more preferably Tm + 220°C or higher and Tm + 350°C or lower, and even more preferably Tm + 250°C or higher and Tm + 300°C or lower. This ensures that, when the powder is micronized and solidified through various atomization methods, the time it exists as molten metal can be extended compared to the past. This achieves spherical particle formation.

[0089] Furthermore, in water atomization methods, for example as described in International Publication No. WO99 / 11407, high-speed water is sprayed in an inverted cone shape, causing molten metal to collide near the apex. As a result, the water film creates a negative pressure near the collision point, thereby making the molten metal smaller. Furthermore, oxidation of the molten metal is suppressed, and even small soft magnetic powders can be spherically shaped.

[0090] The apex angle of the sprayed water (the angle formed inside the apex of the inverted cone) is preferably 3° or more and 15° or less, more preferably 5° or more and 12° or less, and even more preferably 6° or more and 10° or less. As long as the apex angle of the sprayed water is within the above range, the pressure near the collision point formed by the water film can be further reduced, and the time it takes for the flowing molten metal to reach the collision point can be extended. Therefore, even if the manufactured soft magnetic powder is very small, sphericity can be sufficiently achieved.

[0091] Furthermore, in water atomization methods, for example, as described in International Publication No. WO99 / 11407, the aforementioned water can also be sprayed into a cylindrical body called a suction pipe (jet pipe). In this case, the pressure inside the suction pipe is more easily reduced, enabling further refinement of the molten metal and further suppression of oxidation of the molten metal.

[0092] The suction pipe extends downward from the nozzle of the water jet. The length of the suction pipe is preferably 1500 mm or more and 5000 mm or less, more preferably 2000 mm or more and 3500 mm or less, and even more preferably 2200 mm or more and 3000 mm or less. This allows for the efficient production of soft magnetic powders with higher sphericity and smaller specific surface area.

[0093] Furthermore, in the atomization method, molten metal is flowed down from a fine nozzle orifice, causing the resulting fine stream of molten metal to collide with the fluid jet. While the outer diameter of the fine stream of molten metal is not particularly limited, it is preferably 1.0 mm or more and 6.0 mm or less, more preferably 1.5 mm or more and 5.0 mm or less, and even more preferably 2.0 mm or more and 4.0 mm or less. This facilitates uniform collision of the fluid jet with the molten metal, thus making it easy to uniformly disperse appropriately sized droplets. As a result, it is easy to manufacture soft magnetic powders that achieve sphericity regardless of particle size. Furthermore, the particle size of the manufactured soft magnetic powder can be adjusted according to the outer diameter of the fine stream.

[0094] In addition, the manufactured soft magnetic powder can be classified as needed. Classification methods include, for example, dry classification such as sieving, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0095] 3. Powder-pressed magnetic cores and magnetic components Next, the pressed powder core and magnetic elements involved in the implementation method will be described.

[0096] The magnetic components described in the embodiments can be applied to various magnetic components with magnetic cores, such as chokes, inductors, noise filters, reactors, transformers, motors, actuators, solenoid valves, and generators. Furthermore, the powder-pressed magnetic cores described in the embodiments can be applied to the magnetic cores of these magnetic components.

[0097] The following is an example of a magnetic component, using two types of coil components as representatives.

[0098] 3.1. Ring-shaped First, the magnetic element involved in the embodiment, namely the ring-shaped coil component, will be described.

[0099] Figure 1 This is a schematic top view of the annular coil component 10. Figure 1 The coil component 10 shown has an annular pressed powder core 11 and a wire 12 wound around the pressed powder core 11.

[0100] The pressed powder magnetic core 11 is obtained by mixing the soft magnetic powder and binder according to the embodiment, and molding the resulting mixture. The pressed powder magnetic core 11 is a pressed powder body containing the soft magnetic powder according to the embodiment. Therefore, a pressed powder magnetic core 11 with high density and high strength is obtained. In addition, a coil component 10 with high magnetic permeability and high strength is obtained. Moreover, when such a coil component 10 is mounted in electronic devices, it is possible to achieve high performance and miniaturization of electronic devices, etc.

[0101] The constituent materials of the adhesive used in the fabrication of the pressed powder magnetic core 11 include, for example, organic materials such as silicone resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, and polyphenylene sulfide resin, as well as inorganic materials such as phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and silicates such as sodium silicate.

[0102] Materials with high conductivity can be used as constituent materials for the conductor 12, such as metallic materials containing Cu, Al, Ag, Au, Ni, etc. Furthermore, an insulating film may be provided on the surface of the conductor 12 as needed.

[0103] Furthermore, the shape of the pressed powder core 11 is not limited to Figure 1 The ring shape shown can be, for example, a ring shape with a portion missing, or a shape where the long side is a straight line.

[0104] In addition, the pressed powder core 11 may also include soft magnetic powder or non-magnetic powder other than the soft magnetic powder involved in the aforementioned embodiments, as needed.

[0105] 3.2. Closed magnetic circuit type Next, the magnetic element involved in the embodiment, namely the closed magnetic circuit type coil component, will be described.

[0106] Figure 2 This is a schematic perspective view of a closed magnetic circuit type coil component 20.

[0107] The closed magnetic circuit type coil component 20 will be described below, but the following description will focus on the differences between it and the toroidal type coil component 10, and the same items will be omitted from the description.

[0108] Figure 2 The coil component 20 shown is formed by embedding a spirally shaped wire 22 inside a pressed powder core 21. The pressed powder core 21 is a pressed powder body containing the soft magnetic powder involved in the embodiment. Therefore, a pressed powder core 21 with high density and high strength is obtained. In addition, a coil component 20 with high magnetic permeability and high strength is obtained. Moreover, when such a coil component 20 is mounted in electronic devices, it is possible to achieve high performance and miniaturization of electronic devices, etc.

[0109] In addition, the pressed powder core 21 may also include soft magnetic powder or non-magnetic powder other than the soft magnetic powder involved in the aforementioned embodiments, as needed.

[0110] 4. Electronic devices based on Figures 3-5 An electronic device having the magnetic element described in the embodiments will be described.

[0111] Figure 3 This is a perspective view showing the structure of the electronic device involved in the embodiment, namely the mobile personal computer 1100. Figure 3 The personal computer 1100 shown includes a main body 1104 with a keyboard 1102 and a display unit 1106 with a display unit 100. The display unit 1106 is rotatably supported relative to the main body 1104 via a hinge structure. Such a personal computer 1100 may, for example, have built-in magnetic components 1000 such as a choke coil, inductor, and motor for a switching power supply.

[0112] Figure 4 This is a top view showing the structure of the electronic device involved in the embodiment, namely the smartphone 1200. Figure 4The smartphone 1200 shown includes multiple operation buttons 1202, an earpiece 1204, and a microphone 1206. Furthermore, a display unit 100 is disposed between the operation buttons 1202 and the earpiece 1204. Such a smartphone 1200 may incorporate, for example, magnetic components 1000 such as inductors, noise filters, and motors.

[0113] Figure 5 This is a perspective view showing the structure of the electronic device involved in the embodiment, namely the digital camera 1300. The digital camera 1300 uses an imaging element such as a CCD (Charge Coupled Device) to perform photoelectric conversion on the light image of the subject and generate an imaging signal.

[0114] Figure 5 The digital camera 1300 shown includes a display unit 100 located on the back of the housing 1302. The display unit 100 functions as a viewfinder that displays the subject as an electronic image. In addition, a light-receiving unit 1304, including an optical lens, a CCD, etc., is provided on the front side of the housing 1302, i.e., the back side shown in the figure.

[0115] When the photographer confirms the image of the subject displayed on the display unit 100 and presses the shutter button 1306, the CCD's shooting signal at that moment is transmitted and stored in the memory 1308. Such a digital camera 1300 also incorporates magnetic components 1000 such as inductors and noise filters.

[0116] As an electronic device involved in the implementation method, besides Figure 3 Personal computer 1100 Figure 4 Smartphone 1200 Figure 5 Besides digital cameras (1300), other examples include: mobile phones, tablets, watches, inkjet printers and other inkjet printing devices, laptops, televisions, video cameras, video recorders, vehicle navigation systems, pagers, electronic notebooks, electronic dictionaries, calculators, video game consoles, word processors, workstations, videophones, anti-theft 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 detectors, various measuring devices, instruments for vehicles, airplanes, and ships, mobile control devices such as automobile control equipment, aircraft control equipment, railway vehicle control equipment, and ship control equipment, flight simulators, etc.

[0117] Such an electronic device incorporates the magnetic element involved in the implementation method. Therefore, the effects of the magnetic element can be enjoyed, enabling the electronic device to achieve high performance and miniaturization.

[0118] 5. Effects of the implementation method As described above, the soft magnetic powder according to the embodiment is composed of Fe as the main component, Si with a content of 2.5% to 7.5% by mass, Cr with 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 roundness calculated based on the area and perimeter of the particles is 0.80 or more and less than 0.95. Furthermore, in the soft magnetic powder according to the embodiment, in the cumulative particle size distribution curve based on volume measured by laser diffraction, when the particle size at which the cumulative value from the small diameter side is 10% is defined as D10, the particle size at which the cumulative value from the small diameter side is 50% is defined as D50, and the particle size at which the cumulative value from the small diameter side is 90% is defined as D90, the particle size D50 is 3.0 μm or more and 11.0 μm or less, and the particle size difference D90-D10 between the particle size D90 and the particle size D10 is 4.0 μm or more and 22.0 μm or less. In addition, in the soft magnetic powder according to the embodiment, the particle size D50 is defined as A [μm], and the specific surface area is defined as B [m²]. 2 When / g], A×B is greater than 1.20 and less than 2.40.

[0119] Based on this configuration, it is possible to produce soft magnetic powder that can suppress the amount of binder added during molding and can produce high-density and high-strength molded bodies.

[0120] In the soft magnetic powder involved in the embodiments, it is preferable to mix the epoxy resin in a ratio of 2.0% by mass, and then apply it at 98.1 MPa (1.0 t / cm). 2 When the ring is formed into a ring with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm under pressure, the resulting ring has a compression strength of over 13 MPa.

[0121] Based on this configuration, it is possible to produce soft magnetic powder capable of manufacturing pressed powder magnetic cores with sufficiently high mechanical strength. In other words, it is possible to obtain soft magnetic powder that is not prone to defects or cracks in pressed powder magnetic cores and can achieve highly reliable magnetic components.

[0122] In the soft magnetic powder involved in the embodiments, the relative density of the aforementioned molded body is preferably 71.0% or more.

[0123] Based on this configuration, it is possible to obtain soft magnetic powder with a sufficiently high volume fraction and to manufacture pressed magnetic cores with sufficiently high mechanical strength.

[0124] In the soft magnetic powder involved in the embodiments, a tap density of 3.70 g / cm³ is preferred. 3 Above and 5.20 [g / cm] 3 ]the following.

[0125] Based on this composition, a soft magnetic powder with particularly good filling properties is obtained. This enables the manufacture of high-density powder-pressed magnetic cores with excellent magnetic properties.

[0126] The pressed magnetic core involved in the embodiments comprises the soft magnetic powder involved in the embodiments.

[0127] Based on this configuration, a high-density and high-strength pressed powder magnetic core is obtained.

[0128] The magnetic element involved in the embodiment includes the pressed powder magnetic core involved in the embodiment.

[0129] Based on this configuration, magnetic elements with high permeability and high strength are obtained.

[0130] The electronic device involved in the embodiments includes the magnetic element involved in the embodiments.

[0131] Based on this configuration, high-performance and miniaturized electronic devices are obtained.

[0132] The soft magnetic powder, pressed magnetic core, magnetic element, and electronic device of the present invention have been described above based on preferred embodiments, but the present invention is not limited thereto. For example, the shape of the pressed magnetic core and magnetic element is not limited to the illustrated case and can be any shape.

[0133] Example Next, specific embodiments of the present invention will be described.

[0134] 6. Manufacturing of soft magnetic powder Figure 6 Table 1 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 1 to 11. Figure 7 Table 2 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 12 to 18. Figure 8 Table 3 shows the composition, manufacturing conditions, and evaluation results of the soft magnetic powders for samples No. 19 to 27.

[0135] 6.1. Sample No. 1 First, soft magnetic powder was obtained by water atomization. The composition of the obtained soft magnetic powder is shown in Table 1. Figure 6 As shown in Table 1. Furthermore, the manufacturing conditions for the soft magnetic powder based on the water atomization method are as shown in Table 1.

[0136] In addition, for the obtained soft magnetic powder, the particle size D10, particle size D50 (A), particle size D90, particle size difference D90-D10, specific surface area (B), A×B, and average roundness were measured or calculated. The measurement results and calculation results are shown in Table 1.

[0137] 6.2. Samples No. 2~27 In addition to the composition of the soft magnetic powder as shown in Table 1 ( Figure 6 Table 2 Figure 7 ) or Table 3 ( Figure 8 Except for the changes shown, soft magnetic powder was obtained in the same manner as in sample No. 1.

[0138] In addition, in Tables 1, 2 and 3, samples of soft magnetic powder of each sample No. that are equivalent to the present invention are referred to as "Examples", and samples that are not equivalent to the present invention are referred to as "Comparative Examples".

[0139] 7. Evaluation of soft magnetic powders 7.1. Tap density of soft magnetic powder The tap density of the soft magnetic powder for each sample No. was measured. The results were then evaluated in three stages (A to C) according to the following evaluation criteria. The evaluation results are shown in Tables 1, 2, and 3.

[0140] A: Tap density is 4.00 g / cm³ 3 Above and 4.90 g / cm 3 the following B: Tap density is 3.70 g / cm³ 3 Above and 5.20 g / cm 3 The following (excluding the range of A) C: Tapped density less than 3.70 g / cm³ 3 or exceeding 5.20 g / cm 3 7.2. Relative density of molded bodies of soft magnetic powder For each sample No., the soft magnetic powder was pressed into shape, and the relative density of the resulting molded body was measured. Furthermore, the measurement results were evaluated in three stages (A to C) according to the following evaluation criteria. The evaluation results are shown in Tables 1, 2, and 3.

[0141] A: The relative density of the molded part is above 72.0% and below 78.0%. B: The relative density of the molded part is 71.0% or more but less than 72.0%, or more than 78.0% but less than 80.0%. C: The relative density of the molded part is less than 71.0% or more than 80.0%. 7.3. Ring strength of molded bodies made of soft magnetic powder For each sample No., the soft magnetic powder was pressed into shape, and the ring strength of the resulting molded body was measured. Furthermore, the measurement results were evaluated in three stages (A to C) according to the following evaluation criteria. The evaluation results are shown in Tables 1, 2, and 3.

[0142] A: The ring strength of the molded part is above 17MPa and below 30MPa. B: The ring strength of the molded part is 13MPa or higher but less than 17MPa, or more than 30MPa but less than 50MPa. C: The ring strength of the molded part is less than 13MPa or more than 50MPa. As shown in Tables 1, 2, and 3, the soft magnetic powders of each embodiment are considered to have high filling properties and can be used to manufacture high-density and high-strength molded articles. Therefore, it is believed that by using the soft magnetic powders involved in this invention, magnetic components with high magnetic permeability and high reliability can be manufactured.

[0143] Furthermore, when the amount of epoxy resin used was reduced by 10% and the same evaluation was conducted, the evaluation results were the same as those in Table 1. Specifically, when the molded articles were prepared using the soft magnetic powders No. 1 to 11 and the ring strength was measured, the same evaluation results as those in Table 1 were obtained. Therefore, it is believed that by using the soft magnetic powders involved in this invention, good results can be obtained even when the amount of binder added during molding is suppressed.

Claims

1. A soft magnetic powder, characterized in that, Composed of Fe as the main component, The content of Si is 2.5% by mass or more and 7.5% by mass or less. The content of Cr is 1.0% by mass or more and 10.0% by mass or less, and The total content is less than 1.0% by mass of impurities. The average roundness calculated based on the particle's area and perimeter is greater than 0.80 but less than 0.

95. In the cumulative particle size distribution curve of the volume reference determined by laser diffraction, the particle size at which the cumulative value from the small diameter side is 10% is set as D10, the particle size at which the cumulative value from the small diameter side is 50% is set as D50, and the particle size at which the cumulative value from the small diameter side is 90% is set as D90. Particle size D50 is greater than 3.0 μm and less than 11.0 μm. The particle size difference (D90-D10) between particle size D90 and particle size D10 is greater than 4.0 μm and less than 22.0 μm. When particle size D50 is set as A and specific surface area is set as B, A×B is greater than 1.20 and less than 2.

40. The unit of A is μm and the unit of B is m. 2 / g.

2. The soft magnetic powder according to claim 1, characterized in that, The epoxy resin was mixed in a ratio of 2.0% by mass, and then subjected to a pressure of 98.1 MPa, or 1.0 t / cm. 2 When the ring is formed under pressure into a ring with an outer diameter of 14 mm, an inner diameter of 8 mm, and a thickness of 3 mm, the resulting ring has a compression strength of over 13 MPa.

3. The soft magnetic powder according to claim 2, characterized in that, The relative density of the molded body is 71.0% or higher.

4. The soft magnetic powder according to claim 1 or 2, characterized in that, The tap density is 3.70 g / cm³. 3 Above and 5.20 g / cm 3 the following.

5. A pressed powder magnetic core, characterized in that, It contains the soft magnetic powder as described in claim 1 or 2.

6. A magnetic element, characterized in that, It has the powder-pressed magnetic core as described in claim 5.

7. An electronic device, characterized in that, It has the magnetic element as described in claim 6.

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