Soft magnetic powder, compacted powder core, magnetic element, electronic device, and mobile body

Abstract

To provide a soft magnetic powder capable of manufacturing a green compact in which particles are bound with each other via a binder and which is improved in magnetic characteristics while reducing the quantity of the binder to be used for manufacturing the green compact by reducing a specific surface area of a soft magnetic metal particle per se, a powder magnetic core, a magnetic element, an electronic apparatus and a mobile.SOLUTION: The present invention relates to a soft magnetic powder containing soft magnetic metal particles in which when a specific surface area is defined as S[m2 / g], an average particle diameter is defined as d[μm] and an absolute specific gravity is defined as ρ[g / cm3], following formulas (A) S=k{6 / (d ρ)}, (B) 1.0≤k≤4.0 and (C) 1.0≤d≤10.0 are satisfied.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to soft magnetic powder, compacted magnetic cores, magnetic elements, electronic devices, and mobile bodies.

Background Art

[0002] Patent Document 1 discloses silicon oxide-coated soft magnetic powder composed of particles having a silicon oxide coating layer on the surface of soft magnetic metal particles with an iron content of 20% by mass or more. In this silicon oxide-coated soft magnetic powder, the average film thickness of the silicon oxide coating layer is 0.5 to 30 nm, and the BET specific surface area is 1.0 m 2 / g or less.

[0003] In such powder, by forming a silicon oxide coating layer on the surface of the soft magnetic metal particles, the formation of micropores is reduced, and the BET specific surface area becomes small. When the specific surface area becomes small, the amount of resin used can be reduced when the soft magnetic powder is pressure-molded. Thereby, a decrease in magnetic properties in the compacted magnetic core can be suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the silicon oxide-coated soft magnetic powder described in Patent Document 1, a silicon oxide coating layer is formed to reduce the specific surface area. That is, in the invention described in Patent Document 1, the addition of silicon oxide is required to achieve the purpose of reducing the amount of resin required for pressure molding. Therefore, the filling rate of the soft magnetic metal particles decreases by the amount of silicon oxide added, and conversely, the magnetic properties of the compacted magnetic core deteriorate.

Means for Solving the Problems

[0006] The soft magnetic powder according to the application example of the present invention is with a specific surface area of S [m 2 / g], an average particle diameter of d [μm], and a true specific gravity of ρ [g / cm 3 , and satisfies the following formula (A), the following formula (B), and the following formula (C): together with a soft magnetic material including soft magnetic metal particles see the oxygen content of the soft magnetic metal particles is 10,000 ppm or less by mass ratio This is a soft magnetic powder characterized by this. S = k{6 / (d·ρ)} … (A) 1.0 ≦ k ≦ 4.0 … (B) 1.0 ≦ d ≦ 10.0 … (C) The soft magnetic powder according to the application example of the present invention When the specific surface area is S [m 2 / g], the average particle size is d [μm], and the true specific gravity is ρ [g / cm 3 , it satisfies the following formula (A), the following formula (B) and the following formula (C), and soft magnetic metal particles composed of a soft magnetic material, an insulating film provided on the surface of the soft magnetic metal particles, A soft magnetic powder characterized by having S = k{6 / (d·ρ)} … (A) 1.0 ≦ k ≦ 4.0 … (B) 1.0 ≦ d ≦ 10.0 … (C)

[0007] The compacted powder core according to the application example of the present invention is characterized by including the soft magnetic powder according to the application example of the present invention.

[0008] The magnetic element according to the application example of the present invention is characterized by including the compacted powder core according to the application example of the present invention.

[0009] The electronic device according to the application example of the present invention is characterized by including the magnetic element according to the application example of the present invention.

[0010] The moving body according to the application example of the present invention is characterized by including the magnetic element according to the application example of the present invention.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

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Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

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

[0013] 1. Soft Magnetic Powder The soft magnetic powder according to the embodiment is a metal powder exhibiting soft magnetism. Such soft magnetic powder can be applied to any use, but for example, it is used to produce various compacted bodies such as a compacted magnetic core and an electromagnetic wave absorber by binding particles to each other via a binder.

[0014] The soft magnetic powder according to the embodiment contains soft magnetic metal particles. The soft magnetic metal particles have a specific surface area of S [m 2 / g], an average particle diameter of d [μm], and a true specific gravity of ρ [g / cm 3When it is like this, the following formula (A), the following formula (B), and the following formula (C) are satisfied. S = k{6 / (d·ρ)} … (A) 1.0 ≦ k ≦ 4.0 … (B) 1.0 ≦ d ≦ 10.0 … (C)

[0015] In such soft magnetic powder, as described above, it contains soft magnetic metal particles in which the increase in the specific surface area S is sufficiently small compared to the theoretical specific surface area of true spherical particles hypothesized from the average particle diameter d and the true specific gravity ρ. Therefore, when obtaining a green compact in which the particles are bonded to each other via a binder, it is possible to keep the amount of the binder used small. As a result, the filling rate of the soft magnetic metal particles in the green compact is increased, and a green compact excellent in magnetic properties such as magnetic permeability and magnetic flux density can be obtained.

[0016] Further, since the average particle diameter d of the above soft magnetic powder is sufficiently small, eddy current loss can be kept low in the green compact. Therefore, according to such soft magnetic powder, it is possible to realize a green compact having excellent magnetic properties and less core loss.

[0017] The specific surface area S of the soft magnetic metal particles is measured, for example, using a BET specific surface area measuring device HM1201 - 010 manufactured by Mount Tech Co., Ltd. The amount of the specimen is 5 g.

[0018] It can be said that the soft magnetic metal particles whose specific surface area S satisfies the above formula (A) have a specific surface area S in which the increase from the theoretical specific surface area of true spherical particles calculated from the average particle diameter d and the true specific gravity ρ is sufficiently small.

[0019] The inventor has found that when the coefficient k included in the formula (A) satisfies the above formula (B), even if the amount of the binder used is sufficiently small, the soft magnetic metal particles exhibit good fluidity and fillability. Therefore, when the coefficient k included in the formula (A) satisfies the above formula (B), it is possible to obtain a green compact with good fillability of the soft magnetic powder while suppressing the amount of the binder used. In such a green compact, since the amount of the binder used is small, excellent magnetic properties can be obtained and the strength is increased.

[0020] The coefficient k included in the formula (A) preferably satisfies the following formula (B-1), and more preferably satisfies the following formula (B-2).

[0021] 1.0 ≦ k ≦ 3.5 … (B-1) 1.0 ≦ k ≦ 3.0 … (B-2)

[0022] When the value of the coefficient k exceeds the above upper limit value, the specific surface area S becomes significantly larger than the reference, so that the amount of the binder used also becomes significantly larger. As a result, the filling rate (occupation ratio) of the soft magnetic metal particles in the green compact may decrease, and the magnetic properties of the green compact may deteriorate.

[0023] Further, the average particle diameter d satisfies the above formula (C). If the average particle diameter d is sufficiently small in this way, as described above, the eddy current loss in the green compact can be suppressed to a low level.

[0024] The average particle diameter d preferably satisfies the following formula (C-1), and more preferably satisfies the following formula (C-2).

[0025] 1.5 ≦ d ≦ 9.5 … (C-1) 2.0 ≦ d ≦ 9.0 … (C-2)

[0026] When the average particle diameter d is less than the above lower limit value, aggregation becomes significant, and the fluidity and fillability of the soft magnetic powder may decrease. When the average particle diameter d exceeds the above upper limit value, the eddy current loss in the green compact may increase. Further, the gaps between the particles become large, and the fillability of the soft magnetic powder may decrease.

[0027] The average particle diameter d of the soft magnetic metal particles is determined as the particle diameter D50 at which the cumulative percentage from the smaller diameter side reaches 50% in the volume-based particle size distribution obtained by the laser diffraction method.

[0028] Also, for the soft magnetic metal particles, in the volume-based particle size distribution obtained by the laser diffraction method, the particle diameter at which the cumulative percentage from the smaller diameter side reaches 10% is defined as D10, and the particle diameter at which the cumulative percentage from the smaller diameter side reaches 90% is defined as D90. At this time, (D90 - D10) / D50 is preferably 1.0 or more and 1.5 or less, and more preferably 1.0 or more and 1.3 or less. (D90 - D10) / D50 is an index indicating the degree of spread of the particle size distribution. When this index is within the above range, the fillability of the soft magnetic metal particles is improved. For this reason, a compressed powder having particularly high magnetic properties such as permeability and magnetic flux density can be obtained.

[0029] The soft magnetic powder may contain arbitrary soft magnetic particles or non-magnetic particles in addition to the soft magnetic metal particles that satisfy the above-described conditions. However, the content of the soft magnetic metal particles is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0030] The soft magnetic metal particles are composed of a soft magnetic material. The soft magnetic material is not particularly limited as long as it is a soft magnetic material mainly composed of Fe, Ni, or Co. For example, in addition to various Fe-based alloys such as pure iron and Fe-Si-based alloys such as silicon steel, Fe-Ni-based alloys such as permalloy, Fe-Co-based alloys such as permendur, Fe-Si-Al-based alloys such as sendust, Fe-Cr-Si-based alloys, and Fe-Cr-Al-based alloys, various Ni-based alloys and various Co-based alloys can be mentioned. Among these, from the viewpoints of magnetic properties such as permeability and magnetic flux density, and cost, various Fe-based alloys are preferably used.

[0031] In addition, a material having a composition mainly composed of Fe and containing Si or Cr as an element having a high concentration next to the main component is particularly preferably used. In the particles composed of such a material, an oxide film containing Si oxide or Cr oxide is formed on the particle surface. By suppressing the oxidation of the matrix phase by this oxide film, it is possible to suppress an increase in the specific surface area and a change in the particle shape to an irregular shape. Note that the main component means that the concentration of Fe, Ni, or Co is the highest in terms of atomic ratio.

[0032] Further, the crystal structure of the soft magnetic metal particles is not particularly limited, and may be crystalline, amorphous, or microcrystalline (nanocrystalline).

[0033] Among these, the soft magnetic metal particles preferably contain a microcrystalline material as the main material. This microcrystalline material is a material composed of a crystal structure with a particle size of 1.0 nm or more and 30.0 nm or less. By including such a microcrystalline material, the soft magnetism of the soft magnetic metal particles can be further improved. That is, soft magnetic metal particles that achieve both low coercive force and high magnetic permeability can be obtained.

[0034] Note that the main material means that the proportion of the microcrystalline material in the soft magnetic metal particles is 50% by volume or more, preferably 70% by volume or more. The soft magnetic metal particles may contain at least one of a crystalline material and an amorphous material in addition to the microcrystalline material. The crystalline material refers to a material composed of a crystal structure with a particle size of 30.0 nm or more. The amorphous material refers to a material composed of an amorphous structure.

[0035] In addition, the soft magnetic metal particles preferably contain an amorphous material as the main material. This amorphous material is a material composed of an amorphous structure. By including such an amorphous material, the soft magnetism of the soft magnetic metal particles can be further improved.

[0036] Note that the main material refers to the case where the proportion of the amorphous material in the soft magnetic metal particles is 50% by volume or more, preferably 70% by volume or more. The soft magnetic metal particles may contain at least one of a crystalline material and a microcrystalline material in addition to the amorphous material.

[0037] The soft magnetic powder may contain a mixture of two or more of particles mainly composed of a microcrystalline material, particles mainly composed of an amorphous material, and particles mainly composed of a crystalline material. Thereby, a soft magnetic powder having the characteristics of a plurality of types of particles can be realized.

[0038] Examples of the amorphous material and the microcrystalline material include Fe-based alloys such as Fe-Si-B-based, Fe-Si-B-C-based, Fe-Si-B-Cr-C-based, Fe-Si-Cr-based, Fe-B-based, Fe-P-C-based, Fe-Co-Si-B-based, Fe-Si-B-Nb-based, Fe-Si-B-Nb-Cu-based, Fe-Zr-B-based, Ni-based alloys such as Ni-Si-B-based, Ni-P-B-based, and Co-based alloys such as Co-Si-B-based.

[0039] The soft magnetic powder may contain impurities in addition to the soft magnetic material. For example, the oxygen content of the soft magnetic metal particles is preferably 10,000 ppm or less by mass ratio, more preferably 1,000 ppm or more and 8,000 ppm or less, and even more preferably 2,000 ppm or more and 6,000 ppm or less.

[0040] If the oxygen content of the soft magnetic metal particles is within the above range, the amount of the oxide adhering to the surface of the soft magnetic metal particles can be sufficiently reduced. The oxide on the particle surface is one of the causes for increasing the specific surface area S of the soft magnetic metal particles. Therefore, by reducing the amount of the oxide, the specific surface area S can be made smaller.

[0041] Note that the oxygen content of the soft magnetic metal particles is measured by, for example, an oxygen / nitrogen analyzer, TC-300 / EF-300 manufactured by LECO Corporation.

[0042] An insulating film may be provided on the surface of the soft magnetic metal particles, if necessary. That is, the soft magnetic powder may have soft magnetic metal particles and an insulating film provided on the surface of the soft magnetic metal particles. By providing such an insulating film, the insulation between the soft magnetic metal particles can be enhanced. As a result, the eddy current flowing between the particles can be suppressed, and the eddy current loss in the compact can be suppressed.

[0043] Examples of the insulating film include glass materials, ceramic materials, resin materials, and the like.

[0044] The coercive force of the soft magnetic metal particles is not particularly limited, but is preferably 20 [Oe] or less (1592 [A / m] or less), more preferably 10 [Oe] or less (796 [A / m] or less), and even more preferably 0.1 [Oe] or more and 3.0 [Oe] or less (8.0 [A / m] or more and 239 [A / m] or less). By using soft magnetic metal particles having such a small coercive force, a compact that can sufficiently suppress hysteresis loss even when used in a high-frequency range can be manufactured.

[0045] The coercive force of the soft magnetic metal particles can be measured, for example, by a vibrating sample magnetometer such as TM-VSM1230-MHHL manufactured by Tamagawa Seisakusho Co., Ltd.

[0046] The soft magnetic metal particles according to the embodiment preferably have a magnetic permeability of 15 or more, more preferably 17 or more, at a measurement frequency of 100 kHz when made into a compact. Such soft magnetic metal particles contribute to the realization of a compact magnetic core having excellent magnetic properties.

[0047] The magnetic permeability of the compact is, for example, the relative magnetic permeability obtained from the self-inductance of a closed magnetic circuit core coil with the compact in a toroidal shape, that is, the effective magnetic permeability. For the measurement of the magnetic permeability, an impedance analyzer is used, and the measurement frequency is 100 kHz. Also, the number of turns of the winding is 7, and the wire diameter of the winding is 0.6 mm.

[0048] 2. Method for manufacturing soft magnetic powder Next, an example of the method for manufacturing the soft magnetic powder described above will be described.

[0049] The soft magnetic metal particles described above may be powders manufactured by any method. Examples of the manufacturing method include, for example, various atomization methods such as water atomization method, gas atomization method, rotating water flow atomization method, and also pulverization method and the like. Among these, particles manufactured by the atomization method are preferably used for the soft magnetic metal particles. According to the atomization method, high-quality metal powders with a particle shape closer to a perfect sphere and less formation of oxides and the like can be efficiently manufactured. Therefore, metal powders with a smaller specific surface area can be manufactured by the atomization method.

[0050] The atomization method is a method for manufacturing metal powder by colliding molten metal with a liquid or gas sprayed at high speed, atomizing the molten metal and cooling it. In the atomization method, after the molten metal is refined, spheroidization progresses in the process of solidification, so particles closer to a perfect sphere can be manufactured.

[0051] Among these, the water atomization method is a method for manufacturing metal powder from molten metal by using a liquid such as water as a coolant, spraying it in an inverted conical shape that converges at one point, and flowing down and colliding the molten metal toward this convergence point.

[0052] Also, the rotating water flow atomization method is a method for manufacturing metal powder by supplying a coolant along the inner peripheral surface of a cooling cylinder and swirling it along the inner peripheral surface, while blowing a jet of liquid or gas onto the molten metal to scatter the molten metal and taking it into the coolant.

[0053] Furthermore, the gas atomization method is a method for manufacturing metal powder from molten metal by using a gas as a cooling medium, spraying it in an inverted conical shape that converges at one point, and flowing down and colliding the molten metal toward this convergence point.

[0054] The flow rate of the liquid or gas is not particularly limited, but is preferably set to be 100 m / s or more and 1000 m / s or less. Thereby, sufficient speed is imparted to the scattered droplets, so that the droplets are easily cooled. As a result, the generation of oxides is suppressed, and the specific surface area of the produced particles can be suppressed. Further, since solidification occurs while the atomic arrangement in the molten metal state is preserved, for example, when producing a powder of an amorphous material, a powder with a high degree of amorphization can be efficiently produced. Note that increasing the flow rate of the cooling medium tends to reduce the specific surface area of the soft magnetic powder.

[0055] The temperature of the molten metal is preferably set to be about Tm + 20°C or more and Tm + 200°C or less, and more preferably about Tm + 50°C or more and Tm + 150°C or less, with respect to the melting point Tm of the raw material. Thereby, when the molten metal is atomized, the spheroidization of the produced particles proceeds, and the specific surface area can be suppressed. Note that increasing the temperature of the molten metal tends to reduce the specific surface area of the soft magnetic powder.

[0056] The cooling rate when cooling the molten metal in the atomization method is preferably 1×10 4 °C / s or more, and more preferably 1×10 5 °C / s or more. By such rapid cooling, the generation of oxides is suppressed, and the specific surface area of the produced particles can be suppressed. Further, since solidification occurs while the atomic arrangement in the molten metal state is preserved, for example, when producing a powder of an amorphous material, a powder with a high degree of amorphization can be efficiently produced.

[0057] By subjecting the soft magnetic metal particles produced by the above method to heat treatment, the magnetic properties can be enhanced and further low coercivity can be achieved. Also, the specific surface area can be reduced.

[0058] The heating temperature in the heat treatment is preferably Tx - 250°C or more and less than Tx, and more preferably Tx - 100°C or more and less than Tx, where Tx is the crystallization temperature in the soft magnetic metal particles.

[0059] When the heating temperature is within the above range, the heating time in the heat treatment is preferably 5 minutes or more and 120 minutes or less, and more preferably 10 minutes or more and 60 minutes or less.

[0060] By performing the heat treatment under such heating conditions, the residual stress due to rapid solidification generated during the production of the soft magnetic metal particles can be relaxed. As a result, the strain in the soft magnetic metal particles is relaxed, low coercive magnetization can be achieved, and the magnetic properties can be improved. In addition, the particle surface becomes smooth and the specific surface area becomes small.

[0061] Further, the manufactured soft magnetic metal particles may be classified as necessary. Examples of the classification method include dry classification such as sieving classification, inertial classification, and centrifugal classification, and wet classification such as sedimentation classification.

[0062] 3. Powder Compact Core and Magnetic Element Next, the powder compact core and magnetic element according to the embodiment will be described.

[0063] The magnetic element according to the embodiment is applicable to various magnetic elements provided with a core, such as a choke coil, an inductor, a noise filter, a reactor, a transformer, a motor, an actuator, a solenoid valve, a generator, and the like. Further, the powder compact core according to the embodiment is applicable to the core provided in these magnetic elements.

[0064] Hereinafter, as an example of the magnetic element, two types of coil components will be described as representatives. 3.1. Toroidal Type First, a toroidal type coil component, which is an example of the magnetic element according to the embodiment, will be described. FIG. 1 is a plan view schematically showing a toroidal type coil component.

[0065] The coil component 10 shown in FIG. 1 has a ring-shaped compacted powder core 11 and a conductive wire 12 wound around the compacted powder core 11. Such a coil component 10 is generally referred to as a toroidal coil.

[0066] The compacted powder core 11 is obtained by mixing a soft magnetic powder according to the embodiment and a binder, supplying the obtained mixture to a molding die, and pressurizing and molding it. That is, the compacted powder core 11 is a compacted body containing a soft magnetic powder according to the embodiment. In such a compacted powder core 11, since the amount of the binder used can be small, the filling rate (occupancy rate) of the soft magnetic powder can be increased. Therefore, the coil component 10 including the compacted powder core 11 has high magnetic properties such as magnetic permeability and magnetic flux density. Therefore, when the coil component 10 is mounted on an electronic device or the like, the high performance and miniaturization of the electronic device or the like can be achieved.

[0067] Examples of the constituent materials of the binder used for manufacturing the compacted powder core 11 include organic materials such as silicone-based resins, epoxy-based resins, phenol-based resins, polyamide-based resins, polyimide-based resins, and polyphenylene sulfide-based resins, and phosphates such as magnesium phosphate, calcium phosphate, zinc phosphate, manganese phosphate, and cadmium phosphate, and inorganic materials such as silicates such as sodium silicate. In particular, thermosetting polyimide or epoxy-based resins are preferable. These resin materials are easily cured by heating and have excellent heat resistance. Therefore, the manufacturability and heat resistance of the compacted powder core 11 can be improved.

[0068] The ratio of the binder to the soft magnetic powder slightly varies depending on the intended magnetic properties, mechanical properties, allowable eddy current loss, etc. of the compacted powder core 11 to be manufactured, but it is preferably about 0.3 mass% or more and 5.0 mass% or less, more preferably about 0.5 mass% or more and 3.0 mass% or less, and even more preferably about 0.7 mass% or more and 2.0 mass% or less. Thereby, while sufficiently binding the respective particles of the soft magnetic powder, a coil component 10 excellent in magnetic properties can be obtained. In the mixture, various additives may be added for any purpose as needed.

[0069] As the constituent material of the conductive wire 12, materials with high conductivity can be mentioned, for example, metal materials including Cu, Al, Ag, Au, Ni, etc. Further, an insulating film may be provided on the surface of the conductive wire 12 as needed.

[0070] The shape of the compacted powder core 11 is not limited to the ring shape shown in FIG. 1, and may be, for example, a shape in which a part of the ring is missing, a shape in which the longitudinal shape is linear, or a sheet shape, a film shape, etc.

[0071] The compacted powder core 11 may contain soft magnetic powders other than the soft magnetic powders according to the above-described embodiments and non-magnetic powders as needed.

[0072] As described above, the coil component 10 which is a magnetic element includes the compacted powder core 11 containing the above-described soft magnetic powder. Thereby, a coil component 10 with excellent magnetic characteristics can be realized.

[0073] 3.2. Closed magnetic circuit type Next, a closed magnetic circuit type coil component which is an example of the magnetic element according to the embodiment will be described. FIG. 2 is a perspective view showing schematically a closed magnetic circuit type coil component.

[0074] Hereinafter, the closed magnetic circuit type coil component will be described. In the following description, the description will focus on the differences from the toroidal type coil component, and the description of the same matters will be omitted.

[0075] As shown in Fig. 2, the coil component 20 according to this embodiment is formed by embedding a wire 22 formed in a coil shape inside a compacted powder core 21. That is, the coil component 20, which is a magnetic element, includes the compacted powder core 21 containing the above-described soft magnetic powder, and the wire 22 is molded with the compacted powder core 21. This compacted powder core 21 has the same configuration as the compacted powder core 11 described above. Thereby, a coil component 20 with excellent magnetic characteristics can be realized.

[0076] For a coil component 20 in such a form, a relatively small one can be easily obtained. Also, since the coil component 20 has high magnetic characteristics, when the coil component 20 is mounted on an electronic device or the like, high performance and miniaturization of the electronic device or the like can be achieved.

[0077] Further, since the wire 22 is embedded inside the compacted powder core 21, it is difficult for a gap to occur between the wire 22 and the compacted powder core 21. Therefore, it is possible to suppress the vibration due to the magnetostriction of the compacted powder core 21 and suppress the generation of noise accompanying this vibration.

[0078] Note that the shape of the compacted powder core 21 is not limited to the shape shown in Fig. 2, and it may be in a sheet shape, a film shape, or the like.

[0079] Also, the compacted powder core 21 may contain, if necessary, soft magnetic powders other than the soft magnetic powder according to the above-described embodiment and non-magnetic powders.

[0080] 4. Electronic Devices Next, an electronic device including the magnetic element according to the embodiment will be described with reference to Figs. 3 to 5.

[0081] FIG. 3 is a perspective view showing a mobile personal computer which is an electronic device including the magnetic element according to the embodiment. The personal computer 1100 shown in FIG. 3 includes a main body 1104 having a keyboard 1102 and a display unit 1106 having a display unit 100. The display unit 1106 is rotatably supported with respect to the main body 1104 via a hinge structure. Such a personal computer 1100 incorporates a magnetic element 1000 such as a choke coil, an inductor, or a motor for a switching power supply.

[0082] FIG. 4 is a plan view showing a smartphone which is an electronic device including the magnetic element according to the embodiment. The smartphone 1200 shown in FIG. 4 includes a plurality of operation buttons 1202, a receiver 1204, and a transmitter 1206. Further, a display unit 100 is disposed between the operation button 1202 and the receiver 1204. Such a smartphone 1200 incorporates a magnetic element 1000 such as an inductor, a noise filter, or a motor.

[0083] FIG. 5 is a perspective view showing a digital still camera which is an electronic device including the magnetic element according to the embodiment. The digital still camera 1300 photoelectrically converts the optical image of a subject by an imaging device such as a CCD (Charge Coupled Device) to generate an imaging signal.

[0084] The digital still camera 1300 shown in FIG. 5 includes a display unit 100 provided on the back surface of the case 1302. The display unit 100 functions as a finder for displaying a subject as an electronic image. Further, on the front side of the case 1302, that is, on the back side in the figure, a light receiving unit 1304 including an optical lens, a CCD, etc. is provided.

[0085] When the photographer checks the subject image displayed on the display unit 100 and presses the shutter button 1306, the imaging signal of the CCD at that time is transferred and stored in the memory 1308. Such a digital still camera 1300 also incorporates a magnetic element 1000 such as an inductor, a noise filter, etc.

[0086] As electronic devices according to the embodiment, in addition to the personal computer in FIG. 3, the smartphone in FIG. 4, and the digital still camera in FIG. 5, for example, mobile phones, tablet terminals, watches, inkjet ejection devices such as inkjet printers, laptop personal computers, televisions, video cameras, video tape recorders, car navigation devices, pagers, electronic notebooks, electronic dictionaries, calculators, electronic game devices, word processors, workstations, videophones, security television monitors, electronic binoculars, POS terminals, electronic thermometers, blood pressure monitors, blood glucose monitors, electrocardiogram measurement devices, ultrasonic diagnostic devices, medical devices such as electronic endoscopes, fish finders, various measuring devices, vehicles, aircraft, ship instruments, mobile control devices such as automotive control devices, aircraft control devices, railway vehicle control devices, and ship control devices, flight simulators, etc. can be mentioned.

[0087] As described above, such electronic devices are provided with the magnetic element according to the embodiment. Thereby, the effect of the magnetic element of excellent magnetic properties can be enjoyed, and the high performance of the electronic device can be achieved.

[0088] 5. Mobile body Next, a mobile body provided with the magnetic element according to the present embodiment will be described with reference to FIG. 6. FIG. 6 is a perspective view showing an automobile which is a mobile body provided with the magnetic element according to the embodiment.

[0089] The vehicle 1500 incorporates a magnetic element 1000. Specifically, the magnetic element 1000 is incorporated in various vehicle components such as, for example, a car navigation system, an antilock braking system (ABS), an engine control unit, a battery control unit for a hybrid vehicle or an electric vehicle, a vehicle attitude control system, an electronic control unit (ECU) such as an autonomous driving system, a drive motor, a generator, and an air conditioner unit.

[0090] As described above, such a moving body is provided with the magnetic element according to the embodiment. Thereby, the effect of the magnetic element, which is excellent in magnetic properties, can be enjoyed, and the performance of the moving body can be improved.

[0091] In addition to the vehicle shown in FIG. 6, the moving body according to the present embodiment may be, for example, a motorcycle, a bicycle, an aircraft, a helicopter, a drone, a ship, a submarine, a railway, a rocket, a spacecraft, or the like.

[0092] As described above, the soft magnetic powder, the compacted powder core, the magnetic element, the electronic device, and the moving body of the present invention have been described based on preferred embodiments, but the present invention is not limited thereto.

[0093] For example, in the above embodiment, the compacted powder such as the compacted powder core has been described as an example of the use of the soft magnetic powder of the present invention, but the use examples are not limited thereto, and may be magnetic devices such as magnetic fluid, magnetic head, and magnetic shielding sheet.

[0094] Also, the shapes of the compacted powder core and the magnetic element are not limited to those shown in the drawings, and any shape may be used.

Example

[0095] Next, specific examples of the present invention will be described. 6. Manufacture of soft magnetic powder 6.1. Sample No. 1 First, metal powder was obtained by the water atomization method. Next, the obtained metal powder was classified using a sieve.

[0096] Next, the classified metal powder was heat-treated to obtain soft magnetic metal particles. Then, the obtained soft magnetic metal particles were used as the soft magnetic powder of Sample No. 1.

[0097] The constituent material (soft magnetic material) of the obtained soft magnetic powder is shown in Table 1. The compositional formula shown in Table 1 represents the ratio of the constituent elements of the soft magnetic material in atomic%.

[0098] 6.2. Sample Nos. 2 to 27 Soft magnetic powder was obtained in the same manner as Sample No. 1, except that the composition of the soft magnetic powder was as shown in Table 1 and Table 2 or Table 3. The average particle size d and specific surface area S shown in Table 2 and Table 3 were adjusted by changing the powder production conditions by the atomization method. The production conditions used for the adjustment were mainly the flow rate of the molten metal per unit time, the flow rate of the cooling medium, and the temperature of the molten metal.

[0099]

Table 1

[0100] 7. Evaluation of soft magnetic powder 7.1. Particle size distribution For the soft magnetic powder of each sample number, the particle size distribution was measured. This measurement was performed using a laser diffraction type particle size distribution measuring device, Microtrac, HRA9320-X100, manufactured by Nikkiso Co., Ltd. Then, the particle diameters D10, D50, and D90 of the soft magnetic powder were calculated from the particle size distribution. The calculation results are shown in Table 2 or Table 3. The particle diameter D50 was defined as the average particle size d.

[0101] 7.2. True specific gravity For the soft magnetic powder of each sample number, the true specific gravity ρ was measured using a fully automatic gas displacement type densitometer, AccuPyc1330, manufactured by Micromeritics. The measurement results are shown in Table 2 or Table 3.

[0102] 7.3. Specific surface area The specific surface area S of the soft magnetic powder of each sample No. was measured. This measurement was performed using a BET type specific surface area measuring device, HM1201-010, manufactured by Mountec Co., Ltd. The measurement results are shown in Table 2 or Table 3.

[0103] 7.4.Spherical equivalent specific surface area The spherical equivalent specific surface area 6 / (d ρ) was calculated for each sample number of soft magnetic powder. The spherical equivalent specific surface area 6 / (d ρ) was calculated from the average particle size d and the true specific gravity ρ of the soft magnetic material. The calculation results are shown in Table 2 or Table 3.

[0104] 7.5. Coefficient k as a multiplication factor of the specific surface area S to the spherical equivalent specific surface area 6 / (d ρ) The coefficient k was calculated for each sample number of soft magnetic powder. The coefficient k is the multiple of the measured specific surface area S to the specific surface area equivalent to a true sphere, 6 / (d ρ). The calculation results are shown in Table 2 or Table 3.

[0105] 7.6. Oxygen content The oxygen content in mass ratio was measured for the soft magnetic powder of each sample No. A LECO oxygen / nitrogen analyzer, TC-300 / EF-300, was used. The measurement results are shown in Table 2 or Table 3.

[0106] 8. Manufacturing of green compacts Using the soft magnetic powder of each sample number, a green compact was produced as follows.

[0107] First, the soft magnetic powder, the epoxy resin (binder), and the methyl ethyl ketone (organic solvent) were mixed to obtain a mixed material. The amount of the epoxy resin added was as shown in Table 2 or Table 3.

[0108] Next, the obtained mixed material was stirred and then heated at a temperature of 150° C. for 30 minutes to dry, and a lump-shaped dried body was obtained. Next, this dried body was sieved through a sieve with an opening of 500 μm, and the dried body was pulverized to obtain a granulated powder.

[0109] Next, the obtained granulated powder was filled into a mold, and a molded body was obtained based on the following molding conditions.

[0110] · Molding method: Press molding · Shape of the molded body: Ring shape · Dimensions of the molded body: Outer diameter φ14 mm, inner diameter φ7 mm, thickness 3 mm · Molding pressure: 294 MPa Next, the binder in the molded body was cured by heating. Thereby, a compacted powder was obtained.

[0111] 9. Evaluation of the mixed material For the mixed materials containing the soft magnetic powder of each sample No., the viscosity was measured. For the measurement of the mixed materials, a dynamic viscoelasticity measuring device (rheometer) was used to measure the viscosity at 20°C. Then, the measured viscosity was evaluated according to the following evaluation criteria.

[0112] A: The viscosity is particularly low B: The viscosity is slightly low C: The viscosity is medium D: The viscosity is slightly high E: The viscosity is particularly high The evaluation results are shown in Table 2 or Table 3.

[0113] 10. Evaluation of the soft magnetic powder 10.1. Strength of the compacted powder For the soft magnetic powder of each sample No., a compacted powder was obtained by the method shown in 8.

[0114] Next, the strength of the obtained compacted powder was measured. For the measurement of the strength, a compression testing machine was used to measure the maximum load until the compacted powder was broken. Then, the strength of the compacted powder was evaluated by comparing the measured maximum load with the following evaluation criteria.

[0115] A: The strength of the compacted powder is particularly high B: The strength of the compacted powder is slightly high C: The strength of the compacted powder is medium D: The strength of the compacted powder is slightly low E: The strength of the compacted powder is particularly low Show the evaluation results in Table 2 or Table 3.

[0116] 10.2. Density of the compacted powder For the soft magnetic powder of each sample No., a compacted powder was obtained by the method shown in 8.

[0117] Next, the mass of the obtained compacted powder was measured, and based on the measured mass, the density of the compacted powder was calculated. Then, the calculated density was evaluated according to the following evaluation criteria.

[0118] A: The density of the compacted powder is particularly high B: The density of the compacted powder is slightly high C: The density of the compacted powder is medium D: The density of the compacted powder is slightly low E: The density of the compacted powder is particularly low Show the evaluation results in Table 2 or Table 3.

[0119] 10.3. Coercive force For the soft magnetic powder of each sample No., the coercive force was measured using the Tamagawa Seisakusho VSM system TM-VSM1230-MHHL as the magnetization measurement device. The measurement results are shown in Table 3.

[0120] 10.4. Saturation magnetic flux density For the soft magnetic powder of each sample No., the saturation magnetic flux density was calculated by the following method. First, using the magnetization measurement device, the maximum magnetization Mm of the soft magnetic powder was measured.

[0121] Next, the saturation magnetic flux density Bs was obtained by the following formula. Bs = 4π / 10000 × ρ × Mm The calculation results are shown in Table 3.

[0122]

Table 2

[0123]

Table 3

[0124] In Tables 2 and 3, among the soft magnetic powders of each sample No., those corresponding to the present invention are described as "Examples", and those not corresponding to the present invention are described as "Comparative Examples".

[0125] As shown in Tables 2 and 3, when calculating the coefficient k as the multiple of the specific surface area S measured for the soft magnetic powder (soft magnetic metal particles) with respect to the equivalent specific surface area of a true sphere 6 / (d·ρ), when the coefficient k was within a predetermined range, even when the addition amount of the binder was reduced, appropriate viscosity could be obtained in the mixed material. And it was confirmed that such a mixed material could obtain a green compact with high strength and density even with a small addition amount of the binder. Also, it was recognized that the saturation magnetic flux density was increased in the green compact with high density. Therefore, according to the present invention, it was found that when manufacturing a green compact using a binder, the amount of the binder to be used can be reduced, and it is possible to manufacture a green compact having excellent magnetic properties.

[0126] Furthermore, Table 3 also shows that by using an amorphous material or a microcrystalline material, a soft magnetic powder with a low coercive force can be obtained.

[0127] 10.5. Microscopic Observation The soft magnetic powders of Sample Nos. 17, 19, and 21 were observed by a scanning electron microscope. The observation images are shown in FIGS. 7 to 9. FIG. 7 is an observation image of the soft magnetic powder of Sample No. 17. FIG. 8 is an observation image of the soft magnetic powder of Sample No. 19. FIG. 9 is an observation image of the soft magnetic powder of Sample No. 21.

[0128] In FIG. 7, a region R where foreign substances seem to adhere to some parts of the particle surface is recognized. This region R is considered to be a region where oxides are deposited. Therefore, in the soft magnetic powder of Sample No. 17, it is considered that the specific surface area S is increased due to the deposition of oxides on the particle surface.

[0129] In FIGS. 8 and 9, the dark regions as seen in FIG. 7 were hardly confirmed.

Description of Symbols

[0130] 10…Coil component, 11…Powdered iron core, 12…Conductor, 20…Coil component, 21…Powdered iron core, 22…Conductor, 100…Display unit, 1000…Magnetic element, 1100…Personal computer, 1102…Keyboard, 1104…Main body, 1106…Display unit, 1200…Smartphone, 1202…Operation button, 1204…Earphone jack, 1206…Microphone jack, 1300…Digital still camera, 1302…Case, 1304…Light receiving unit, 1306…Shutter button, 1308…Memory, 1500…Automobile, R…Region

Claims

1. Let the specific surface area be S [m ２ / g], the average particle size be d [μm], and the true specific gravity be ρ [g / cm ３ . When they satisfy the following formula (A), the following formula (B), and the following formula (C), and include soft magnetic metal particles composed of a soft magnetic material, A soft magnetic powder, wherein the oxygen content of the soft magnetic metal particles is 10,000 ppm or less by mass ratio. S = k{6 / (d·ρ)} … (A) 1.0 ≤ k ≤ 4.0 … (B) 1.0 ≤ d ≤ 10.0 … (C)

2. Let the specific surface area be S [m ２ / g], the average particle diameter be d [μm], and the true specific gravity be ρ [g / cm ３ . When they satisfy the following formula (A), the following formula (B), and the following formula (C), together with soft magnetic metal particles composed of a soft magnetic material, An insulating film provided on the surface of the soft magnetic metal particles, and a soft magnetic powder characterized by having the same. S = k{6 / (d·ρ)} … (A) 1.0 ≤ k ≤ 4.0 … (B) 1.0 ≤ d ≤ 10.0 … (C)

3. The soft magnetic powder according to claim 1 or 2, wherein the soft magnetic material constituting the soft magnetic metal particles mainly contains a microcrystalline material composed of a crystal structure having a particle size of 1.0 nm or more and 30.0 nm or less.

4. The soft magnetic powder according to claim 1 or 2, wherein the soft magnetic material constituting the soft magnetic metal particles mainly contains an amorphous material composed of an amorphous structure.

5. The soft magnetic powder according to any one of claims 1 to 4, wherein the soft magnetic material is a material having a composition containing Fe as a main component and containing Si or Cr as an element having a high concentration next to Fe.

6. A compacted magnetic core characterized by containing the soft magnetic powder according to any one of claims 1 to 5.

7. A magnetic element characterized by including the compacted magnetic core according to claim 6.

8. An electronic device characterized by including the magnetic element according to claim 7.

9. A moving body characterized by including the magnetic element according to claim 7.

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