Pelletized powder, magnetic molded body, and inductor

Abstract

The present invention provides a granulated powder, which has high repeatability of filling weight to a molding die, and can improve the density of a molded body produced by heating and pressurizing in the die. The granulated powder is a granulated powder having large particles and small particles, and the difference between the value obtained by dividing the D90 particle size of the granulated powder by the D10 particle size of the granulated powder and the value obtained by dividing the D90 particle size of the large particles by the D10 particle size of the large particles is -1.68 or less.

Description

Technical Field

[0001] This invention relates to a granulated powder, a magnetic molded body, and an inductor. Background Technology

[0002] Patent Document 1 discloses a composite particle comprising a first particle made of a soft magnetic metal material and a second particle fixed to the first particle, covering more than 70% of its surface. It is claimed that the composite particle described in Patent Document 1 reliably bonds the first and second particles, thus enabling uniform distribution of the first and second particles when the composite particle is compressed to form a pressed powder magnetic core, thereby obtaining a pressed powder magnetic core with high filler content and high permeability.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2014-103265 Summary of the Invention

[0006] The density of a magnetic core made by filling granulated powder into a mold and then heating and pressing it may depend on the flowability of the granulated powder.

[0007] The purpose of this invention is to provide a granulated powder, a magnetic molded body, and an inductor that can increase the density of a molded body produced by heating and pressurizing in a molding die by improving the flowability of the granulated powder.

[0008] This specification contains the entire contents of Japanese Patent Application No. 2024-101265, filed on June 24, 2024.

[0009] One aspect of the present invention is a granulated powder having large particles and small particles, wherein the difference between the value obtained by dividing the D90 particle size of the granulated powder by the D10 particle size of the granulated powder and the value obtained by dividing the D90 particle size of the large particles by the D10 particle size of the large particles is -1.68 or less.

[0010] According to the present invention, it is possible to provide granulated powder, magnetic molded body, and inductor that can increase the density of a molded body produced by heating and pressurizing in a molding die by improving the flowability of the granulated powder. Attached Figure Description

[0011] Figure 1 This is a perspective view of the inductor according to an embodiment of the present invention, viewed from the top surface side.

[0012] Figure 2 This is a three-dimensional view of the inductor viewed from the bottom side.

[0013] Figure 3It is a perspective three-dimensional diagram showing the internal structure of an inductor.

[0014] Figure 4 This is a diagram showing the manufacturing process of an inductor.

[0015] Figure 5 This is a schematic diagram showing the composition of the granulated particles contained in the granulated powder.

[0016] Figure 6 This is a schematic diagram illustrating an example of stress measurement results. Detailed Implementation

[0017] In magnetic cores manufactured by filling granulated powder into a mold and then heating and pressing it, the filling rate of the granulated powder in the mold depends on the properties of the granulated powder.

[0018] The inventors, particularly from the viewpoint of increasing the density of the molded body produced by heating and pressurizing within a molding die, conducted in-depth research on the properties and state that granulated powder should possess, thereby completing this invention.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0020] [1. Inductor]

[0021] First, an example of the structure and manufacturing process of an inductor made using granulated powder as the magnetic core material will be explained.

[0022] [1.1. Structure of an Inductor]

[0023] Inductors made using granulated powder as the core material are, for example, chip inductors that are roughly hexagonal in shape.

[0024] Figure 1 , Figure 2 and Figure 3 This is a diagram showing the overall configuration of an inductor 1 according to one embodiment.

[0025] Figure 1 This is a perspective view of inductor 1 as seen from the top surface 12. Figure 2 This is a three-dimensional view of inductor 1 as seen from the bottom 10 side.

[0026] The inductor 1 in this embodiment is configured as a surface-mount electronic component, having a main body 2 with a generally hexahedral shape, i.e., a generally cuboid shape, and a pair of external electrodes 4 disposed on the surface of the main body 2.

[0027] Hereinafter, in the main body 2, a first main surface facing the mounting substrate not shown at the time of mounting is defined as a bottom surface 10, a second main surface opposite to the bottom surface 10 is referred to as an upper surface 12, a pair of third main surfaces orthogonal to the bottom surface 10 is referred to as end surfaces 14, and a pair of fourth main surfaces orthogonal to the bottom surface 10 and the pair of end surfaces 14 is referred to as side surfaces 16.

[0028] As shown in FIG. 1, a distance from the bottom surface 10 to the upper surface 12 is defined as a thickness T of the main body 2, a distance between the pair of side surfaces 16 is defined as a width W of the main body 2, and a distance between the pair of end surfaces 14 is defined as a length L of the main body 2. Further, a direction of the thickness T is defined as a thickness direction DT, a direction of the width W is defined as a width direction DW, and a direction of the length distance is defined as a length direction DL. Figure 1

[0029] The size of the inductor is, for example, 2.0 mm in the length L dimension, 1.2 mm in the width W dimension, and 0.9 mm in the thickness T dimension.

[0030] Figure 3 is a perspective view showing the internal configuration of the inductor.

[0031] The main body 2 is provided with a coil conductor 20 and a substantially hexahedral magnetic core 30 in which the coil conductor 20 is embedded, and is configured as a molded inductor in which the coil conductor 20 is enclosed in the magnetic core 30.

[0032] The magnetic core 30 is compression-molded into a substantially hexahedral molded body by pressure and heat application in a state in which a granulated powder containing metal magnetic particles and resin is enclosed around the coil conductor 20.

[0033] The metal magnetic particles contain both first metal magnetic particles of large particles having a large average particle diameter and second metal magnetic particles of small particles having a small average particle diameter. Thereby, at the time of compression molding, the second metal magnetic particles as the small particles enter between the first metal magnetic particles as the large particles together with the resin, and thereby the density of the metal magnetic particles in the magnetic core 30 can be increased, and the magnetic permeability can be increased.

[0034] Details of the particle diameter of the metal particles of the first metal magnetic particles and the second metal magnetic particles will be described later.

[0035] Both the first metal magnetic particles and the second metal magnetic particles are particles having a metal particle and an insulating film covering the surface thereof. By covering the metal particle with the insulating film, the insulating resistance and the voltage resistance can be increased.

[0036] ​For the first and second metallic magnetic particles, Fe-based metallic magnetic particles, such as Fe (pure iron) or Fe alloys, can be used. As an example of an Fe alloy, an alloy selected from one or more of the following can be used: alloys containing Fe and Ni, alloys containing Fe and Co, alloys containing Fe and Si, alloys containing Fe, Si, and Cr, alloys containing Fe, Si, and Al, alloys containing Fe, Si, B, and C, alloys containing Fe, Si, B, and Cr, and alloys containing Fe, P, Cr, Si, B, Nb, and C.

[0037] The composition of the metal particles in the first metallic magnetic particle can be the same as or different from that in the second metallic magnetic particle.

[0038] The insulating film formed on the surface of the first and second metallic magnetic particles can be, for example, one or more insulating films selected from inorganic glass films, organic-inorganic mixed films, and inorganic insulating films formed by the sol-gel reaction of metal alkoxides.

[0039] In this embodiment, the first metallic magnetic particles are Fe-Si-B-C amorphous alloy powder, and the second metallic magnetic particles are pure iron coated with glass using the sol-gel method.

[0040] The resin material in the granulated powder is preferably a thermosetting resin. As an example, the resin in the granulated powder is a thermosetting epoxy resin.

[0041] The granulated powder will be explained further later.

[0042] like Figure 3 As shown, the coil conductor 20 has a winding portion 22 on which a wire is wound and a pair of leads 24 extending from the winding portion 22 and at least partially exposed from the body 2.

[0043] The coil conductor 20 consists of a wire and a coating formed on the surface of the wire. The wire is a strip-shaped wire (so-called a flat wire) made of copper with a rectangular cross-section.

[0044] It should be noted that the coil conductor 20 does not necessarily need to be wound; it can also be in a straight shape, a meandering shape, etc.

[0045] The winding portion 22 of the coil conductor 20 is formed by winding a wire in a spiral shape so that both ends of a band-shaped wire (hereinafter also simply referred to as a wire) are led out to the outer periphery and connected to each other at the inner periphery. Inside the main body 2, the coil conductor 20 is embedded in the magnetic core 30 in a posture in which the center axis of the winding portion 22 is along the thickness direction DT of the main body 2. The lead-out portion 24 is led out from the winding portion 22 to each of the end faces of the pair of end faces 14, one major surface of which is exposed from the main body 2 and the other major surface of which is embedded in the main body 2. The above-mentioned one major surface of the lead-out portion 24 exposed from the main body 2 is electrically connected to the external electrode 4.

[0046] The pair of external electrodes 4 is a so-called L-shaped electrode composed of an L-shaped member continuously extending from each of the end faces of the end faces 14 of the main body 2 to the bottom face 10. The external electrode 4 is connected to the lead-out portion 24 of the coil conductor 20 at the end face 14, and the portion 4A (L-shaped portion) extending to the bottom face 10 is electrically connected to the wiring of the circuit substrate by a suitable mounting means such as soldering. Figure 2 ) through a suitable mounting means such as soldering. Note that the external electrode 4 is not limited to the above-mentioned L-shaped electrode, but can be a so-called five-surface electrode structure, or a bottom face electrode.

[0047] A main body protective layer as an insulating film is formed on the surface of the main body 2 except for the range of the external electrode 4. The main body protective layer is, for example, an epoxy resin, a phenoxy resin, and a novolak resin, and a material containing metal oxide fine particles as a filler can be used. In the present embodiment, the main body protective layer contains a silica filler as the metal oxide fine particles and an epoxy resin. In addition to the above-mentioned materials, the main body protective layer can be a resin such as polyurethane, acrylic, polyimide, polyimide amide, polyamide, or a glass, an oxide film.

[0048] The inductor configured as described above can improve DC superposition characteristics by using a soft magnetic material as the metal magnetic particle, and thus can be used as an electronic component of an electrical circuit through which a large current flows, a choke coil of a DC-DC converter circuit, a power supply circuit, and the like, and can be used for electronic components of electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, automobile electronic products, medical and industrial machines, and the like. However, the use of the inductor is not limited to this, and the inductor can be used, for example, for a tuning circuit, a filter circuit, a rectification smoothing circuit, and the like.

[0049] [1.2. Manufacturing process of inductor]

[0050] The inductor 1 can be manufactured, for example, as follows.

[0051] Figure 4 is a view showing the manufacturing process of the inductor 1.

[0052] The manufacturing process of inductor 1 may include a granulation process (S1), a preform formation process (S2), a coil conductor formation process (S3), a body forming process (S4), a roller grinding process (S5), a surface treatment process (S6), and an external electrode formation process (S7).

[0053] The granulation process (S1) is a process of granulating the mixed powder, which is a raw material for the magnetic core 30, with the metal magnetic particles and resin to obtain granulated powder. Details of the granulation process (S1) will be described later.

[0054] The preform formation process (S2) is the process of forming a preform called a plate. The preform is a molded body obtained by pressing the granulated powder, which is the material of the main body 2, into a mold and shaping it into a solid shape that is easy to handle. In this embodiment, as an example, two types of plates are formed: a first plate with a groove for the coil conductor 20 to enter and an E-shaped cross-section, and a second plate with a groove covering the first plate and an I-shaped (plate-like) cross-section.

[0055] The coil conductor forming process (S3) is the process of forming a coil conductor 20 from a wire. The coil conductor 20 is formed by winding the wire into a shape, for example, having a winding portion 22 with an α-coil and a pair of lead-out portions 24. It should be noted that, as mentioned above, the coil conductor 20 does not necessarily need to be wound, and can also be in a straight shape, a meandering shape, etc.

[0056] In the main body forming process (S4), the first plate, the coil conductor 20, and the second plate are placed in the forming mold. While heating, pressure is applied along the direction of overlap between the first and second plates to solidify them, thereby integrating the first plate, the coil conductor, and the second plate into one piece. Thus, the main body 2, in which the coil conductor 20 is enclosed within the magnetic core 30, is formed.

[0057] In the drum grinding process (S4), multiple main bodies 2 are filled inside the drum to rotate it in a manner that avoids applying excessive impact. Additionally, a coating liquid serving as a protective layer for the main bodies is sprayed using a sprayer. This rounds the corners of the main bodies 2 and applies the coating liquid to them. Afterward, the main bodies 2 coated with the coating liquid are removed from the drum and subjected to heat treatment, thereby forming a protective layer on the surface of the main bodies 2.

[0058] It should be noted that the formation of the main protective layer is not limited to the above method. A process different from the roller grinding process (S4) can be set up. It can be carried out by various methods such as spraying coating liquid onto the main body 2, immersing the main body 2 in coating liquid, supplying coating liquid to the surface of the main body 2 via a distributor, and / or printing coating material on the surface of the main body 2 by various printing methods.

[0059] The surface treatment step (S5) is a step of modifying the surface of the electrode predetermined position by irradiating laser light to the electrode predetermined position of the surface of the magnetic core 30. Here, the electrode predetermined position refers to a range in which the external electrode 4 should be formed on the surface of the magnetic core 30, including the portion of the lead-out portion 24 exposed. Specifically, by irradiating laser light, the main protective layer of the surface of the magnetic core 30 and the coating layer of the lead-out portion 24 of the coil conductor 20 are removed in the range of the electrode predetermined position, and at the same time, the resin of the surface of the magnetic core 30 is removed, and the insulating film of the surface of the metal magnetic particle exposed from the magnetic core 30 is removed. Thereby, the exposed area of the metal of the metal magnetic particle per unit area of the surface of the magnetic core 30 increases in the portion of the electrode predetermined position in the surface of the magnetic core 30 compared to the other surface portions of the magnetic core 30.

[0060] In the external electrode formation step (S7), the external electrode 4 is formed on the electrode predetermined position on the magnetic core 30. Specifically, first, a Cu plating layer is formed on the electrode predetermined position on the magnetic core 30 by electrolytic plating. Next, a Ni plating layer and a Sn plating layer can be formed on the Cu plating layer by electrolytic plating.

[0061] [2. Granulated powder]

[0062] Next, the granulated powder used to form the magnetic core 30 that is the magnetic core of the inductor 1 will be described.

[0063] As described above, in the magnetic core produced by filling the granulated powder into a mold and performing heat and pressure molding, the filling rate of the granulated powder in the mold depends on the properties of the granulated powder. As the conditions required for the granulated powder, it is particularly important that the filling rate of the granulated powder filled into the mold be high and that the density of the magnetic core produced from the granulated powder be high (i.e., the density of the metal magnetic particle be high).

[0064] From the above viewpoint, the inventors and others have intensively studied the properties and state that the granulated powder should have, and have found that when the D90 particle diameter / D10 particle diameter (the value obtained by dividing the D90 particle diameter by the D10 particle diameter) of the granulated powder is a prescribed value, the sliding property of the granulated powder described later is improved. Thereby, the flowability of the granulated powder at the time of heat and pressure is improved, and high densification of the magnetic core can be achieved.

[0065] The larger the D90 particle diameter / D10 particle diameter, the larger the D90 particle size relative to the D10 particle diameter, and thus the particle size distribution takes a wide shape. On the other hand, the smaller the D90 particle diameter / D10 particle diameter, the closer to 1, and the smaller the D90 particle diameter relative to the D10 particle diameter, and thus the particle size distribution takes a sharp shape.

[0066] Hereinafter, an embodiment and examples of the granulated powder that can improve the shape stability of the magnetic core and can achieve high densification will be described.

[0067] [2.1. Embodiment of granulated powder]

[0068] The difference between the D90 particle size / D10 particle size of the granulated powder of the present embodiment and the D90 particle size / D10 particle size of the first metal magnetic particle monomer is -2.00 or less. More preferably, the difference between the D90 particle size / D10 particle size of the granulated powder and the D90 particle size / D10 particle size of the first metal magnetic particle monomer is -1.68 or less.

[0069] With these preferred particle sizes, the attachment uniformity of the second metal magnetic particles attached around the first metal magnetic particles is good, and the flowability of the granulated powder can be improved.

[0070] Note that the attachment uniformity of the second metal magnetic particles refers to the state of the arrangement and number of the second metal magnetic particles attached around the first metal magnetic particles.

[0071] [2.2. Method of manufacturing granulated powder]

[0072] Next, the method of manufacturing the granulated powder of the present embodiment will be described.

[0073] The method of manufacturing the granulated powder shown below can be implemented in the granulation step (S1) shown in the manufacturing process of Figure 4 .

[0074] The granulated powder is produced by a stirring granulation method or a tumbling fluidized granulation method.

[0075] The stirring granulation method is a method of using a stirring granulator, feeding the powder of the metal magnetic particles as a raw material into a granulation container, rotating a main shaft and a granulation shaft in the horizontal direction, and adding a resin solution of a solution of a thermosetting resin while stirring and mixing the first metal magnetic particles and the second metal magnetic particles, to agglomerate the granulated powder into a spherical shape.

[0076] The tumbling fluidized granulation method is a method of using a tumbling fluidized granulator, feeding the powder of the metal magnetic particles into a substantially cylindrical flow layer container, blowing a blast gas (e.g., nitrogen) from a blast port at the bottom and rotating a stirring blade, causing the above-mentioned powder to flow in the flow layer container, and in this state, spraying a resin solution from a spray nozzle at the upper portion to the above-mentioned flowing powder, to agglomerate the granulated powder into a spherical shape.

[0077] As one example, the composition of the metal magnetic particles and the composition of the resin solution, etc. are as shown below.

[0078] The above powder of metal magnetic particles contains first metal magnetic particles as large particles and second metal magnetic particles as small particles. The first metal magnetic particles are Fe-Si-B-C-based alloy, and the D50 particle diameter is 28.25 μm. The second metal magnetic particles are pure iron coated with glass by a sol-gel method, and the D50 particle diameter is 2.07 μm. The weight ratio of the first metal magnetic particles to the second metal magnetic particles in the above powder of metal magnetic particles is first metal magnetic particles : second metal magnetic particles = 90-60 : 10-40 in either of the stirring granulation method and the rotary flow granulation method, and more preferably first metal magnetic particles : second metal magnetic particles = 65 : 35.

[0079] Further, the resin solution contains a thermosetting resin, i.e., an epoxy resin, as a main agent and an epoxy resin curing agent as a curing agent, and contains methyl ethyl ketone as a dilution solvent. Note that the dilution solvent is not limited to methyl ethyl ketone, and can be any solvent capable of diluting the main agent and the curing agent. For example, as other options for the dilution solvent, ethanol, methanol, acetone, methyl isobutyl ketone, ethyl acetate, isobutyl acetate, toluene, xylene, tetrahydrofuran, n-hexane, and cyclohexane can be mentioned.

[0080] Further, the granulation step (S1) includes sieve treatment of further classifying the particle diameter of the granulation powder obtained by the stirring granulation method or the rotary flow granulation method. The sieve treatment can also be referred to as classification treatment.

[0081] The sieve treatment is the process described below. A sieve having a mesh size of 106 μm is provided on the upper side, and a sieve having a mesh size of 53 μm is provided on the lower side. The obtained granulation powder is fed to the sieve having a mesh size of 106 μm on the upper side, and is left to vibrate in a sieve shaker for 5 minutes. Thereafter, only the granulation powder remaining on the sieve having a mesh size of 53 μm on the lower side is taken out, and is fed to the sieve having a mesh size of 106 μm on the upper side, and is left to vibrate in a sieve shaker for 5 minutes, whereby the first treatment is performed. The above first treatment is repeated three times, and only the granulation powder remaining on the sieve having a mesh size of 53 μm is used, and is moved to the preform molding step (S2) below.

[0082] By performing such sieve treatment, the granulation powder having a particle diameter that is too large and the granulation powder having a particle diameter that is too small can be removed. It is presumed that, in the granulation powder having a particle diameter that is too large, for example, the first metal magnetic particles having a relatively large particle diameter coagulate with each other, or the second metal magnetic particles excessively adhere to the first metal magnetic particles, whereby the adhesion uniformity of the second metal magnetic particles to the first metal magnetic particles deteriorates. It is presumed that, in the granulation powder having a particle diameter that is too small, the second metal magnetic particles having a relatively small particle diameter do not sufficiently adhere to the first metal magnetic particles, and the second metal magnetic particles coagulate with each other, whereby the adhesion uniformity of the second metal magnetic particles to the first metal magnetic particles deteriorates.

[0083] Further, such sieve treatment has an advantage of being able to change the properties of the granulated powder after granulation, which is difficult to achieve by a stirring granulation method, a tumbling flow granulation method, or other known granulation methods.

[0084] Figure 5 is a schematic view showing the configuration of the granulated particles 40 of the granulated powder of the present embodiment. The granulated particles 40 contained in the granulated powder are particles obtained by granulating metal magnetic particles and a main agent and a curing agent of a prescribed weight ratio as a thermosetting resin, and include metal magnetic particles 41 and a thermosetting resin 42. The metal magnetic particles 41 include first metal magnetic particles 41a and second metal magnetic particles 41b that differ in particle diameter. The average particle diameter of the second metal magnetic particles 41b is smaller than the average particle diameter of the first metal magnetic particles 41a. As shown in Figure 5 , the second metal magnetic particles 41b are attached around the first metal magnetic particles 41a.

[0085] [2.3. Examples of Granulated Powder]

[0086] The processes of obtaining the granulated powder were performed by the tumbling granulation method and the tumbling flow granulation method described in the granulation step (S2), respectively. Further, sieve treatment was performed on each of the obtained granulated powders. Evaluation was performed on a total of six kinds of granulated powders obtained by the above two kinds of processes, and the first metal magnetic particles as one of the raw materials of the granulated powder.

[0087] The evaluation targets are listed below.

[0088] The first is the first metal magnetic particle monomer, which is set as Comparative Example 1. The second is a granulated powder produced by a stirring granulation method and not subjected to sieve treatment, which is set as Comparative Example 2. The third is a granulated powder produced by a stirring granulation method and remaining on a sieve having a mesh size of 53 μm in sieve treatment, which is set as Example 1. The fourth is a granulated powder produced by a stirring granulation method and falling to the bottom inside a sieve shaker by a sieve having a mesh size of 53 μm in sieve treatment, which is set as Comparative Example 3. The fifth is a granulated powder produced by a tumbling flow granulation method and not subjected to sieve treatment, which is set as Comparative Example 4. The sixth is a granulated powder produced by a tumbling flow granulation method and remaining on a sieve having a mesh size of 53 μm in sieve treatment, which is set as Example 2. The seventh is a granulated powder produced by a tumbling flow granulation method and falling to the bottom inside a sieve shaker by a sieve having a mesh size of 53 μm in sieve treatment, which is set as Comparative Example 5.

[0089]

[0090] The evaluation results are shown in Table 1.

[0091] (Particle diameter)

[0092] The particle size distribution of each kind of evaluation object, i.e., the D10 particle diameter, the D50 particle diameter, and the D90 particle diameter, was measured using a particle size distribution analyzer (Mastersizer 3000 manufactured by Malvern) by a method according to laser diffraction scattering method according to JIS Z 8825.

[0093] The value obtained by dividing the value of the D90 particle diameter of each kind of evaluation object by the value of the D10 particle diameter, i.e., D90 particle diameter / D10 particle diameter, was calculated. The value of the D90 particle diameter / D10 particle diameter of Comparative Example 1, i.e., the larger first metal magnetic particle, i.e., 5.08, was set as α, and the D90 particle diameter / D10 particle diameter of each kind of evaluation object minus α was calculated.

[0094] The D90 particle diameter / D10 particle diameter minus α corresponds to the difference between the D90 particle diameter / D10 particle diameter of the granulated powder and the D90 particle diameter / D10 particle diameter of the first metal magnetic particle monomer.

[0095] Note that the measurement of the particle size distribution of the evaluation object can also use the following method.

[0096] The following method can be cited: by dissolving the resin contained in the granulated powder with a solvent (e.g., methyl ethyl ketone, acetone, carbon tetrachloride, and the like), or by performing thermal decomposition by heating, a powder is obtained, the particle diameter of the powder is measured, and thereby the particle size distribution is obtained.

[0097] Further, the method of observing the cross section of a plurality of granulated powders and calculating the equivalent circle diameter of the particles of the granulated powder can also be cited. Specifically, about 1 g of the granulated powder is piled up into a mountain and subjected to a heat curing treatment or the like, which is an example of a treatment that changes the shape so as to prevent the resin contained in the granulated powder from dissolving into the resin used to expose the cross section, after the resin is embedded and the cross section is exposed, the cross section is observed, and thereby the particle size distribution using the volume basis of the equivalent circle diameter can be obtained.

[0098] In the peaks of the particle size distributions obtained by the above two methods, the particles falling within the first particle size distribution having the largest peak of the particle diameter are taken as the first metal magnetic particles, and the value of the D90 particle diameter / D10 particle diameter of the large particles is obtained from the above first particle size distribution. In the case where it is difficult to obtain the value of the first particle size distribution having the largest peak assuming that the particle size distributions of the first metal magnetic particles and the second metal magnetic particles overlap, the first metal magnetic particles and the second metal magnetic particles are assumed to be normally distributed, respectively, and the two peaks are separated using any one of a Gaussian function, a Voigt function, or a Lorentz function, and the one having the larger value of the maximum peak is taken as the first metal magnetic particles.

[0099] (Sliding property)

[0100] The sliding property of each kind of evaluation object was evaluated.

[0101] The following describes the method for measuring slippage.

[0102] Slippage can be measured according to JIS-Z 8835. More specifically, slippage can be measured using a single-sided shear test apparatus of the lower unit direct-acting type (Nano Seeds NS-S500 powder layer shear force measuring apparatus manufactured by Nano Seeds Co., Ltd.) through the following steps. The inner diameters of both the upper and lower units are set to 15 mm, and the gap (micro-gap) between the upper and lower units is set to 0.2 mm. Before placing the powder, the upper indenter is positioned in both the upper and lower units and the zero point is set so that the thickness of the powder layer can be measured using a laser sensor. 10 g of powder sample is uniformly filled into the upper and lower units, the upper indenter is gently positioned, and then a 150 N indentation load is applied using a vertical servo motor. At the moment the 150 N indentation load is applied using the vertical servo motor, the position of the load cell of the vertical servo motor is fixed. The indentation speed is set to 0.2 mm / s. Slippage begins 100 seconds after the position of the load cell of the vertical servo motor is fixed. That is, the lateral sliding start delay is set to 100 seconds. After the lateral sliding begins with the operation of the horizontal servo motor, the pressure is measured every 0.1 seconds. The lateral sliding speed is set to 5 μm / s. For each test sample, at least N=50 points are continuously measured during the operation of the horizontal servo motor, and the measurement is stopped when the coefficient of variation (CV value) of the measured value is below 0.4%. The thickness of the finally compacted powder layer (final powder layer thickness) is measured using a laser sensor. Through such measurements, the following results are obtained: Figure 6 The data shown. Figure 6 In the curve graph, the stress on the vertical axis is the measured value of the bottom load (the load applied to the weighing sensor on the bottom side). (a) represents the running time of the vertical servo motor, (b) represents the maximum load applied, (c) represents the load applied at the start of the lateral slide, and (d) represents the running time of the horizontal servo motor.

[0103] Stress relaxation rate [%] = 100 × (maximum indentation load [N] - transverse slip indentation load [N]) / maximum indentation load [N] (1)

[0104] Sliding property [% / mm] = Stress relaxation rate [%] / (Final powder layer thickness [mm]) (2)

[0105] The sliding property can be determined using the above equations (1) and (2) based on the measured maximum indentation load (the value detected by the weighing sensor on the bottom side), the indentation load at the start of the lateral sliding, and the final powder layer thickness.

[0106] As shown in Table 1, it was confirmed that in the granulated powder produced by the stirring granulation method, the sliding property of Example 1, which underwent sieving, was greater than that of Comparative Example 2, which was not sieved, and Comparative Example 3, which was removed during sieving.

[0107] Here, it is presumed that the granulated powder whose sliding property is greater than that of the granulated powder produced by the stirring granulation method and not subjected to the sieve treatment of Comparative Example 2 has better flowability than the granulated powder produced by the usual stirring granulation method.

[0108] When the relationship between the D90 particle diameter / D10 particle diameter - a and the sliding property of each of Comparative Example 2, Example 1, and Comparative Example 3 is fitted with a quadratic function, the D90 particle diameter / D10 particle diameter - a at which the sliding property is 2.74 is calculated to be -1.54 from the fitted equation.

[0109] Note that in the fitting in which the sliding property is a quadratic function of the D90 particle diameter / D10 particle diameter - a, it is presumed that the smaller the D90 particle diameter / D10 particle diameter - a, the greater the sliding property in reality, and therefore the value of the D90 particle diameter / D10 particle diameter - a at which the sliding property is 2.74 is taken as the smaller solution.

[0110] Further, as shown in Table 1, it is confirmed that the sliding property of Example 2, which is subjected to the sieve treatment, is greater than that of Comparative Example 4, which is not subjected to the sieve treatment, and Comparative Example 5, which is removed in the sieve treatment, among the granulated powders produced by the rotary fluidized granulation method.

[0111] From the above results, it is presumed that the granulated powder whose sliding property is greater than that of the granulated powder produced by the rotary fluidized granulation method and not subjected to the sieve treatment of Comparative Example 4 has better flowability than the granulated powder produced by the usual rotary fluidized granulation method.

[0112] When the relationship between the D90 particle diameter / D10 particle diameter - a and the sliding property of each of Comparative Example 4, Example 2, and Comparative Example 5 is fitted with a quadratic function, the D90 particle diameter / D10 particle diameter - a at which the sliding property is 2.86 is calculated to be -1.81.

[0113] From the above presumption, it is presumed that the threshold value of the D90 particle diameter / D10 particle diameter - a at which the sliding property of the granulated powder increases and the flowability improves, regardless of the stirring granulation method or the rotary fluidized granulation method, is the arithmetic mean of -1.54 and -1.81, i.e., -1.68, as compared with the case where the sieve treatment is not performed.

[0114] Thus, it is confirmed that the sliding property of the granulated powder whose D90 particle diameter / D10 particle diameter - a is -1.68 or less is good, and therefore the flowability is good.

[0115] Note that it is presumed that the relationship between the D90 particle diameter / D10 particle diameter - a and the sliding property is a relationship having an extreme value when they are fitted with a quadratic function, and this is presumed to be due to the following reason. That is, it is predicted that the granulated powder that passes through the sieve having a mesh size of 53 μm contains a large amount of substances in which the second metal magnetic particles are aggregated without being attached to the first metal magnetic particles.

[0116] Note that all of the above-described embodiments and examples illustrate one embodiment of the present application, and any modification and application can be made without departing from the spirit of the present application.

[0117] Further, the directions such as horizontal and vertical, and various numerical values, shapes, materials in the above-described embodiments include a range (so-called equivalent range) that functions the same as these directions, numerical values, shapes, materials, unless specifically described.

[0118] [3. Configuration supported by the above-described embodiments and examples]

[0119] The above-described embodiments and examples support the following configurations.

[0120] (Configuration 1) A granulated powder having large particles and small particles, wherein a difference between a value obtained by dividing a D90 particle diameter of the granulated powder by a D10 particle diameter of the granulated powder and a value obtained by dividing a D90 particle diameter of the large particles by a D10 particle diameter of the large particles is -1.68 or less.

[0121] According to Configuration 1, by improving the flowability of the granulated powder, it is possible to improve the density of a molded body produced by heating and pressurizing in a molding die.

[0122] (Configuration 2) The granulated powder according to Configuration 1, wherein a difference between a value obtained by dividing a D90 particle diameter of the granulated powder by a D10 particle diameter of the granulated powder and a value obtained by dividing a D90 particle diameter of the large particles by a D10 particle diameter of the large particles is -2.00 or less.

[0123] According to Configuration 2, by further improving the flowability of the granulated powder compared to Configuration 1, it is possible to improve the density of a molded body produced by heating and pressurizing in a molding die.

[0124] (Configuration 3) The granulated powder according to Configuration 1 or 2, wherein the large particles are a metal magnetic substance.

[0125] According to Configuration 3, the granulated powder exhibits good magnetic properties.

[0126] (Configuration 4) The granulated powder according to any one of Configurations 1 to 3, wherein the small particles are a metal magnetic substance.

[0127] According to Configuration 4, the granulated powder exhibits good magnetic properties.

[0128] (Configuration 5) A magnetic molded body using the granulated powder according to any one of Configurations 1 to 4.

[0129] According to Configuration 5, the same effects and advantages are exhibited.

[0130] (Constitution 6) An inductor using the magnetic molded body described in Constitution 5.

[0131] According to Constitution 6, the same effects as described above are exerted.

[0132] Symbol explanation

[0133] 1... inductor, 2... main body, 4... external electrode, 10... bottom surface, 12... upper surface, 14... end surface, 16... side surface, 20... coil conductor, 22... winding portion, 24... lead-out portion, 30... magnetic core.

Claims

1. A granulated powder having large particles and small particles, The difference between the value obtained by dividing the D90 particle size of the granulated powder by the D10 particle size of the granulated powder and the value obtained by dividing the D90 particle size of the large particle by the D10 particle size of the large particle is less than -1.

68.

2. The granulated powder according to claim 1, wherein, The difference between the value obtained by dividing the D90 particle size of the granulated powder by the D10 particle size of the granulated powder and the value obtained by dividing the D90 particle size of the large particle by the D10 particle size of the large particle is less than -2.

00.

3. The granulated powder according to claim 1 or 2, wherein, The large particles are metallic magnetic materials.

4. The granulated powder according to any one of claims 1 to 3, wherein, The small particles are metallic magnetic materials.

5. A magnetic molded body using the granulated powder according to any one of claims 1 to 4.

6. An inductor using the magnetic molded body of claim 5.

Images