JP2020170823A - Coated particle powder and manufacturing method - Google Patents

Abstract

To provide coated particle powder having a high coverage insulator film with little variation in film thickness even when crushed powder with a distorted shape is used as soft magnetic particle powder.SOLUTION: The coated particle powder includes coating particles that include: soft magnetic particles; and an isolation layer 40 that has a first inorganic insulation layer formed over the surface of the soft magnetic particles and a second inorganic insulation layer formed over the surface of the first inorganic insulation layer. When observing the cross-section, the ratio of coating particles with an aspect ratio of 2 or more, which indicates the ratio of the maximum width to the minimum width of coating particles, is 80% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a coated particle powder whose insulation is coated on soft magnetic particles and a method for producing the same.

In recent years, with the spread of hybrid cars and the advent of electric vehicles, the importance of electric motors as a means of transportation is increasing more than ever. The use of electric motors is expanding not only for transportation means such as automobiles, ships, and airplanes, but also for industrial equipment and electric appliances in general households.

Not limited to electric motors, in power electronics equipment used for alternating current such as inverters, transformers, and reactors, soft magnetic materials are used as iron cores in those equipment. When the iron core is excited at a high frequency, an eddy current loss occurs in addition to the hysteresis loss. The hysteresis loss is proportional to the exciting frequency, while the eddy current loss is proportional to the square of the frequency. For this reason, in order to realize compact, high-efficiency, low-loss power electronics equipment that is expected to become even more demanding from the market in the future, reduction of eddy current of iron core and high resistance using soft magnetic material It is indispensable to change.

As a technique for reducing the eddy current of the iron core and increasing the resistance, in Patent Document 1, first, the insulating film material particles containing a glass material as a main component are pressed and fixed onto the soft magnetic material particles. The first layer is formed by forming the insulating film of the second layer and then spray-applying an aqueous solution of phosphoric acid and boric acid-based salt having low viscosity and high fluidity to form the insulating film of the second layer. Disclosed is a technique for reducing eddy current loss by increasing the coating property of the eye insulating film and thereby improving the insulating property of the soft magnetic powder.

Further, in Patent Document 2, an insulating film such as Fe ₂ O ₃ or phosphate is first formed on the soft magnetic metal powder, and then, along with the soft magnetic metal powder coated with the insulating film, ferrite or the like is used. Disclosed is a technique for improving insulating properties by dispersing ceramic nanopowder such as insulator nanopowder, Al ₂ O ₃ , SiO ₂ , and TiO ₂ in a polymer resin.

Further, in Patent Document 3, the soft magnetic powder particles are first coated with an inorganic insulating material such as a metal phosphate, and then the soft magnetic powder particles coated with the inorganic insulating material are coated with an epoxy resin or the like. A technique for improving withstand voltage and mechanical properties by coating with an organic insulating material is disclosed.

Japanese Patent No. 5293326 Japanese Unexamined Patent Publication No. 2016-92403 International Publication No. WO2016 / 043295

However, in the case of the technique disclosed in Patent Document 1, a uniform insulating film can be formed, but in the friction mixer for forming the first layer insulating film, the shape of the soft magnetic metal powder is spherical. The process is designed for near atomized powders. Therefore, for example, when the soft magnetic metal powder is a crushed powder having a distorted shape other than a spherical shape, the soft magnetic metal powder that becomes the core is mechanically formed in the process of forming the insulating film of the first layer. Cracks are likely to occur due to such stress, and there is a problem that it is difficult to exert a desired effect in terms of film coverage and the like.

Further, in the case of the technique disclosed in Patent Document 2, since the ceramic nanopowder and the insulator nanopowder having the effect of improving the pressure resistance are dispersed in the polymer resin, the soft magnetic particles. Is not completely covered. Therefore, there is a problem that the effect of improving the withstand voltage cannot be expected as much as that of an insulating film completely coated with soft magnetic particles.

Further, in the case of the technique disclosed in Patent Document 3, it is an insulating film having a two-layer structure of an inorganic insulating material such as a phosphoric acid film and an organic insulating film such as an epoxy resin. Of these, the organic resin material also serves as a binder in the normal dust molding process, and has the problem that its dielectric strength is lower than that of an insulating film in which an inorganic insulating material is laminated in two layers. Have.

Therefore, in view of the above problems, in the present invention, even when a pulverized powder having a non-spherical and distorted shape such as atomized powder is used as the soft magnetic particle powder, the thickness variation is small and the insulating property has high coating property. It is an object of the present invention to provide a coating particle powder having a film.

In order to achieve this object, the coating particle powder according to the present invention contains soft magnetic particles and
An insulating layer including a first inorganic insulating layer formed on the surface of the soft magnetic particles and a second inorganic insulating layer formed on the surface of the first inorganic insulating layer.
A coating particle powder containing coating particles comprising
When the cross section is observed, the ratio of the coating particles having an aspect ratio of 2 or more, which indicates the ratio of the maximum width to the minimum width of the coating particles, is 80% or more.

The coating particle powder according to the present invention can alleviate the unevenness of the surface of the powder particles even if the soft magnetic particles used are powder particles having a distorted shape such as crushed powder. As a result, it is possible to obtain coating particles having a uniform insulating layer with little variation in film thickness. Further, by laminating an inorganic insulating film, it is possible to obtain coating particles having high withstand voltage and excellent eddy current suppression performance.

It is schematic cross-sectional view which shows the cross-sectional structure of the coating particle contained in the coating particle powder which concerns on Embodiment 1. FIG. It is schematic cross-sectional view which shows the cross-sectional structure of the coating particle contained in the coating particle powder which concerns on the modification of Embodiment 1. It is a graph which shows the relationship between the Al ₂ O ₃ content ratio and the dielectric strength of the molded product using the coating particle powder which concerns on 1st Example. This is an example of a scanning electron microscope (SEM) photograph showing a cross section of a spherical atomized powder. It is an example of a scanning electron microscope (SEM) photograph showing a cross section of a distorted pulverized powder.

The coating particle powder according to the first aspect includes soft magnetic particles and
An insulating layer including a first inorganic insulating layer formed on the surface of the soft magnetic particles and a second inorganic insulating layer formed on the surface of the first inorganic insulating layer.
A coating particle powder containing coating particles comprising
When the cross section is observed, the ratio of the coating particles having an aspect ratio of 2 or more, which indicates the ratio of the maximum width to the minimum width of the coating particles, is 80% or more.

According to the above configuration, by having these two insulating layers, even if the shape of the particles is not spherical like atomized powder, for example, powder particles having a distorted shape such as crushed powder, the powder particles The unevenness of the surface can be alleviated. As a result, soft magnetic particles having a uniform insulating layer with little variation in film thickness can be obtained, and by laminating an inorganic insulating film, soft magnetic particles having high withstand voltage and excellent eddy current suppression performance can be obtained. Body particles can be obtained.

In the first aspect of the coating particle powder according to the second aspect, at least one of the first inorganic insulating layer and the second inorganic insulating layer is Al ₂ O ₃ , Cr ₂ O ₃ , Nb. _It may contain at least one selected from the group ₂ O ₅ and Ti ₂ O ₃ .

According to the above configuration, the first inorganic insulating layer or the second inorganic insulating layer formed by Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ and Ti ₂ O ₃ is chemically stable passivation. Since a film is formed, coating particles having excellent rust resistance can be obtained.

In the coating particle powder according to the third aspect, in the first or second aspect, the ratio of the metal element contained in the insulating layer is 2 wt% to 50 wt% of the metal element contained in the soft magnetic particle. You may.

According to the above configuration, by adjusting the ratio of the metal elements contained in the insulating layer, the dielectric strength and rust prevention performance of the soft magnetic device using the coating particle powder of this embodiment can be adjusted to a desired level. Can be done.

In the coating particle powder according to the fourth aspect, even if the metal element contained in the insulating layer is at least one of Al, Cr, Nb and Ti in any one of the first to third aspects. Good.

In the fourth aspect of the coating particle powder according to the fifth aspect, the insulating layer may be a metal silicate film containing at least one element of Al, Cr, Nb and Ti.

According to the above configuration, unreacted metals such as Al, Cr, Nb, and Ti in Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , and Ti ₂ O ₃ are oxidized by oxygen in SiO _2. As a result, coating particles having excellent insulation pressure resistance and rust resistance can be obtained.

In the coating particle powder according to the sixth aspect, at least one of the first inorganic insulating layer and the second inorganic insulating layer is formed of SiO ₂ in any one of the first to third aspects. It may be an insulated region.

According to the above configuration, when SiO ₂ becomes the first inorganic insulating layer, the damage caused by the collision of the fine particles with the soft magnetic particles generated in the subsequent dry process for forming the second inorganic insulating layer is mitigated. SiO ₂ acts as a barrier layer. Therefore, there are effects of improving the magnetic characteristics, improving the coating rate of the insulating layer on the soft magnetic particles, and reducing the variation in the film thickness of the insulating layer to improve the withstand voltage. Further, when SiO ₂ forms the second inorganic insulating layer, it could not be covered by the immobilization of the fine particles on the soft magnetic particles in the dry process for forming the first inorganic insulating layer prior to this. SiO ₂ can cover the exposed surface of the soft magnetic particles. Therefore, the coverage of the insulating layer on the soft magnetic particles is improved, the variation in the film thickness of the insulating layer is reduced, and the withstand voltage is improved.

The coated particle powder according to the seventh aspect has the above-mentioned first to sixth aspects, wherein the soft magnetic particles are nanocrystalline material, amorphous material, or nanocrystalline material and amorphous. It may be a mixture of quality materials.

According to the above configuration, even in the case of nanocrystalline or amorphous soft magnetic particles that do not contain the metal element Cr in the soft magnetic particles, it is excellent to use this embodiment. It is possible to obtain a coated particle powder having both magnetic properties and rust resistance.

The coating particle powder according to the eighth aspect may have an average particle size of 0.1 μm to 100 μm in any one of the first to seventh aspects.

According to the above configuration, it is necessary to design a filling rate of soft magnetic particles capable of achieving both magnetic permeability and dielectric strength required in a soft magnetic device using the present coated particle powder within the range of the particle diameter. Can be done.

In the method for producing coated particle powder according to a ninth aspect, a first inorganic insulating layer is formed on the surface of soft magnetic particles.
It includes forming a second inorganic insulating layer on the surface of the first inorganic insulating layer.

According to the above configuration, by going through this two-step insulating layer forming process, even if the shape of the particles is not spherical like atomized powder, for example, powder particles having a distorted shape such as pulverized powder The unevenness on the surface of the powder particles can be alleviated. As a result, soft magnetic particles having a uniform insulating layer with little variation in film thickness can be obtained, and by laminating an inorganic insulating film, soft magnetic particles having high withstand voltage and excellent eddy current suppression performance can be obtained. Body particles can be obtained.

In the method for producing a coated particle powder according to a tenth aspect, in the ninth aspect, the first inorganic insulating layer is formed by a dry process.
The second inorganic insulating layer may be formed by a wet process.

In the method for producing a coated particle powder according to the eleventh aspect, in the ninth aspect, the first inorganic insulating layer is formed by a wet process.
The second inorganic insulating layer may be formed by a dry process.

The method for producing the coated particle powder according to the twelfth aspect is 10% of the average particle size of the soft magnetic particles as the material of the first inorganic insulating layer used in the dry process in the tenth aspect. Insulating fine particles having the following average particle size may be prepared.

The method for producing the coated particle powder according to the thirteenth aspect is 10% of the average particle size of the soft magnetic particles as the material of the second inorganic insulating layer used in the dry process in the eleventh aspect. Insulating fine particles having the following average particle size may be prepared.

According to the above configuration, when the average particle size of the insulating fine particles is not more than the above range, the soft magnetic particles can be uniformly coated, so that the eddy current is reduced, the withstand voltage is improved, and the rust prevention performance is improved. The improvement effect of can be obtained.

Hereinafter, the coating particle powder according to the embodiment and the method for producing the same will be described in detail with reference to the drawings. The embodiments of the present disclosure are not limited to the embodiments described below, and can be changed to various other embodiments.

(Embodiment 1)
FIG. 1 is a schematic cross-sectional view showing a cross-sectional structure of the coating particles 100 contained in the coating particle powder according to the first embodiment. FIG. 2 is a schematic cross-sectional view showing the cross-sectional structure of the coating particles contained in the coating particle powder according to the modified example of the first embodiment.

According to FIG. 1, the coating particles 100 contained in the coating particle powder according to the first embodiment of the present disclosure are the soft magnetic particles 10 and the first inorganic insulating layer 20 that covers the surface of the soft magnetic particles 10. And, the insulating layer 40 composed of the second inorganic insulating layer 30 covering the surface of the first inorganic insulating layer is included. Further, when the cross section of the coated particle powder is observed, the ratio of the coated particles having an aspect ratio of 2 or more indicating the ratio of the maximum width to the minimum width of the coated particles is 80% or more.
According to the coating particle powder according to the first embodiment, even when the pulverized powder having a distorted shape is used as the soft magnetic particle powder, the coating particle powder having an insulating film with little variation in film thickness can be obtained. it can. As a result, it is possible to reduce the eddy current and improve the withstand voltage. In addition, it is possible to improve the rust preventive property in a device using soft magnetic particles that do not contain Cr having antioxidant performance inside.

The components constituting the coated particle powder will be described below.

<Soft magnetic particles>
As the soft magnetic particle 10, pure iron powder, Fe—Si alloy, sendust, permalloy, permendur and the like, as well as amorphous particles, nanocrystalline particles and the like can be used. The amorphous particles and nanocrystal particles may contain any one or more elements such as B, C, P, Cu, Co, and Ni in addition to Fe and Si.

When the soft magnetic particles 10 are amorphous particles, a nanocrystal structure having a crystal size of about 10 nm to 20 nm can be formed in the amorphous particles by performing an appropriate heat treatment at a temperature of 500 ° C. or lower. it can. This makes it possible to reduce the coercive force of the soft magnetic particles 10.

<First inorganic insulating layer>
The first inorganic insulating layer 20 has 1 insulating fine particles 21 such as Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , Ti ₂ O ₃ , and SiO _{2 on} the surface of the soft magnetic particles 10. More than one type, it is formed by physically immobilizing in a dry process. In this case, the first inorganic insulating layer 20 is Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , Ti ₂ O ₃ , SiO ₂ physically fixed to the surface of the soft magnetic particle 10. It is composed of insulating fine particles 21 such as. At this time, the particles physically immobilized on the surface of the soft magnetic particles 10 may be one or more of the metal fine particles 22 such as Al, Cr, Nb, and Ti and the semiconductor fine particles 23 such as Si. When the particles physically immobilized on the surface of the soft magnetic particles 10 are the metal fine particles 22 or the semiconductor fine particles 23, the metal fine particles 22 and the semiconductor fine particles 23 are formed in the step of forming the second inorganic insulating layer 30 described later. It is oxidized. As a result, the first inorganic insulating layer 20 is formed at the same time as the second inorganic insulating layer 30, and the insulating layer 40 including the first inorganic insulating layer 20 and the second inorganic insulating layer 30 is formed. The particle diameters of the insulating fine particles 21, the metal fine particles 22, and the semiconductor fine particles 23 used in the step of forming the first inorganic insulating layer 20 are preferably 10 nm to 1 μm.

Specific physical immobilization methods include methods called mechanochemicals, such as hybridization (registered trademark), mechanofusion (registered trademark), jet mill, and planetary mill. As an example, a method of physically immobilizing the insulating fine particles 21 on the surface of the soft magnetic particles 10 by using a hybridization system (manufactured by Nara Machinery Co., Ltd.) will be described.

(1) In the immobilization of particles by a hybridization device, first, the soft magnetic particle 10 as a base material and the soft magnetic particle 10 are immobilized on the surface of the soft magnetic particle 10 to form a first inorganic insulating layer 20. The base insulating fine particles 21 are charged into the apparatus.
(2) Next, a high-speed air flow is generated in the apparatus to disperse the soft magnetic particles 10 and the insulating fine particles 21. At the same time, by rotating the bladed disk in the device at high speed, centrifugal force and physical impact are applied to the soft magnetic particles 10 and the insulating fine particles 21. As a result, the insulating fine particles 21 can be physically immobilized on the surface of the soft magnetic particles 10 in an extremely short time of less than 10 minutes, and the first inorganic insulating layer 20 can be formed. In the step of forming the first inorganic insulating layer 20, in order to prevent the soft magnetic particles 10 from being oxidized, it is desirable to fill the inside of the apparatus with an inert atmosphere using nitrogen, argon or the like for the treatment.

In the above step, the insulating fine particles 21 collide with the surface of the soft magnetic particles 10 in a state of having high kinetic energy, and are adsorbed or buried on the surface of the soft magnetic particles 10. This has the effect of alleviating the surface irregularities of the soft magnetic particles 10 which are formed by pulverization and have an irregular shape. The collision energy can be controlled by adjusting the rotation speed of the disk of the hybridization device. Therefore, even if the surface irregularities of the soft magnetic particles 10 formed by pulverization change for each production lot, the surface irregularities of the soft magnetic particles 10 can be controlled. As a result, there is an effect that the variation in the film thickness in the step of forming the second inorganic insulating layer 30 described later can be suppressed.

<Second inorganic insulating layer>
Next, the second inorganic insulating layer 30 and the method for forming the second inorganic insulating layer 30 will be described. The second inorganic insulating layer 30 further covers the surface of the first inorganic insulating layer 20 that covers the surface of the soft magnetic particles 10.

The second inorganic insulating layer 30 is formed by forming inorganic insulating particles on the surface of the first inorganic insulating layer 20 by causing a hydrolysis / dehydration condensation reaction of alkoxide, for example, by a sol-gel method. To.

As an example, a case where a SiO ₂ film is formed as the second inorganic insulating layer 30 by using TEOS (tetraethoxysilane) will be described.

The soft magnetic particles 10 coated with the first inorganic insulating layer 20 are immersed in a mixed solution of TEOS, aqueous ammonia as a catalyst, and ethanol as a solvent, stirred, and then dried to dry the solvent. A SiO ₂ film can be formed on the surface of the insulating layer 20 as a second inorganic insulating layer. As a result, the coating particles 100 having the insulating layer 40 including the first inorganic insulating layer 20 and the second inorganic insulating layer 30 are formed on the soft magnetic particles 10. At this time, the film thickness of SiO ₂ formed can be controlled by changing various conditions such as the amount of TEOS, the amount of ammonia water as a catalyst, and the stirring time.

The solvent for the hydrolysis / dehydration condensation reaction of TEOS in the sol-gel method is not limited to ethanol, and for example, 2-propanol (IPA) or the like can be used. Further, the catalyst is not limited to aqueous ammonia, and for example, hydrochloric acid, nitric acid, or the like can be used.

The SiO ₂ film, which is the second inorganic insulating layer 30, is formed on the surface of the first inorganic insulating layer 20 by the hydrolysis / dehydration condensation reaction of TEOS. The SiO ₂ film, which is the second inorganic insulating layer 30, further covers a region on the surface of the soft magnetic particles 10 in which the irregularities on the surface are alleviated by forming the first inorganic insulating layer 20. However, not only that, the SiO ₂ film, which is the second inorganic insulating layer 30, can also cover the exposed surface on which the first inorganic insulating layer 20 is not completely covered on the soft magnetic particles 10. .. As a result, even when the soft magnetic material particles 10 are formed by pulverization and have a distorted shape, the Al ₂ O ₃ film single layer, the Cr ₂ O ₃ film single layer, the Nb ₂ O ₅ film single layer _, or SiO It is possible to form the insulating layer 40 having less variation in the film thickness than when the _two- film single-layer insulating film is formed.

Further, the oxygen in the SiO ₂ film forming the second inorganic insulating layer 30 is unoxidized contained in Al ₂ O ₃ , Cr ₂ O ₃ , and Nb ₂ O ₅ forming the first inorganic insulating layer 20. Can oxidize metal elements. Even when the metal fine particles 22 or the semiconductor fine particles 23 are used instead of the insulating fine particles 21 in the step of forming the first inorganic insulating layer 20, the metal fine particles 22 or the semiconductor is used in the step of forming the second inorganic insulating layer 30. The fine particles 23 are oxidized by reacting with oxygen in the SiO ₂ film forming the second inorganic insulating layer 30, to form the first inorganic insulating layer 20.

When Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , TIO _2, etc. are used as the insulating fine particles 21 in the step of forming the first inorganic insulating layer 20, or Al, Cr, Nb as the metal fine particles 22 , Ti and the like, since metal silicate is formed as the insulating layer 40 in the step of forming the second inorganic insulating layer 30, the withstand voltage of the coating particles 100 increases. Therefore, by changing the ratio of the metal elements contained in the first inorganic insulating layer 20 forming the coating particles 100, it is possible to control the dielectric strength of the magnetic element after powder molding to a desired value. is there. Further, since Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ , TiO _{2 and the} like contained in the insulating layer 40 are particles that form a chemically stable passivation film, the coating particles 100 and the dust powder are formed. It has the effect of enhancing the rust resistance of the soft magnetic element after molding. The rust prevention property can also be controlled by changing the ratio of the metal elements contained in the first inorganic insulating layer 20.

(Modification example)
FIG. 2 is a schematic cross-sectional view showing the cross-sectional structure of the coating particles 100 contained in the coating particle powder according to the modified example of the first embodiment.
The order of the step of forming the first inorganic insulating layer 20 and the step of forming the second inorganic insulating layer 30 may be interchanged. In this case, as shown in FIG. 2, the structure of the insulating layer 40 is such that the insulating fine particles 21, the metal fine particles 22, and the semiconductor fine particles 23 are physically driven into the surface of the SiO ₂ film previously formed by the Zolgel method. It is in a state of being dispersed in the SiO ₂ film. Unreacted metal in the insulating fine particles 21 implanted into the SiO ₂ film is oxidized by the SiO ₂ film, the metal silicate is formed, the withstand voltage of the coated particles 100 is increased. When the SiO ₂ film is first formed and then the insulating fine particles 21, the metal fine particles 22, and the semiconductor fine particles 23 are physically immobilized, the SiO ₂ film becomes the soft magnetic particles 10. It acts as a barrier film against collisions of insulating fine particles, metal fine particles, and semiconductor fine particles. Therefore, the damage caused by the direct collision of the insulating fine particles, the metal fine particles, and the semiconductor fine particles with the soft magnetic particle 10 as the base material is reduced, the dielectric strength is further increased, and at the same time, the rust prevention property is also improved. To do. Further, even when there is a large variation in the film thickness of the SiO ₂ formed due to the unevenness of the surface of the soft magnetic particle 10 as the base material, the unevenness can be smoothed and made uniform by the collision of the fine particles. Therefore, even if a part of the SiO ₂ film formed on the surface of the soft magnetic particle 10 has a thin film thickness region, the electric field concentration in that region can be relaxed and the dielectric strength can be improved. ..

When the first inorganic insulating layer 20 or the second inorganic insulating layer 30 is formed by a wet process, the average thickness is, for example, 50 nm to 300 nm.

In addition, this process can be applied not only to crushed powder having a distorted shape of soft magnetic particles, but also to cases where the shape of soft magnetic particles such as atomized powder is spherical or close to it. it can.

(First Example)
(1) In the first embodiment, soft magnetic particles having an average particle size of 100 μm or less formed by pulverization were prepared, and these were mixed with Al ₂ O ₃ fine particles having an average particle size of 10 nm to 1 μm. The content ratio of the Al ₂ O ₃ fine particles to the soft magnetic particles in the mixed powder at this time was between 2 wt% and 50 wt%.

(2) The mixed powder was put into the hybridization apparatus, and a film forming process was performed at a predetermined rotation speed and time to form an Al ₂ O ₃ film on the surface of the soft magnetic particles.

(3) Next, for 500 g of the soft magnetic particles on which the Al ₂ O ₃ film was formed, 1 kg of ethanol, 50 g of TEOS (tetraethoxysilane, Si (OC ₂ H ₅ ) ₄ ), and aqueous ammonia (containing ammonia). 50 g (amount 28 to 30% by volume) was added, and the mixture was stirred for 2 hours.
(4) After stirring, the pulverized powder was separated and dried to obtain a coated particle powder having a SiO ₂ film formed on the surface of the Al ₂ O ₃ film. The film thickness of the formed insulating layer was 300 nm.

With respect to the obtained coating particles, the ratio of the coating particles having an aspect ratio of 2 or more is 80% or more. Here, the "aspect ratio" indicates the ratio of the maximum width to the minimum width of the coated particles when the coated particles are observed in cross section. The "ratio of particles having an aspect ratio of 2 or more" is the ratio of the sum of the areas of the coated particles having an aspect ratio of 2 or more to the sum of the areas of all the coated particles when the aggregate of the coated particles is observed in cross section. Is shown.

Through each of the above steps, a coating particle powder containing coating particles having an insulating layer formed on the surface of the soft magnetic particles was mixed with a binder, molded, and cured to prepare a square sample. Then, a voltage was applied above and below this sample using a digital ultra-high resistance / micro ammeter 5451 (manufactured by ADC Co., Ltd.) to measure the withstand voltage. The measurement result of the dielectric strength is shown in FIG.

FIG. 3 is a graph showing the relationship between the Al ₂ O ₃ content ratio and the dielectric strength of the molded product using the coated particle powder according to the first embodiment. The horizontal axis of FIG. 3 represents the content ratio of Al ₂ O ₃ , and the vertical axis represents the withstand voltage. As shown in the figure, it can be seen that the withstand voltage increases from about 70 V / mm to 600 V / mm as the content ratio of Al ₂ O ₃ is increased. This indicates that by laminating the SiO ₂ film and the Al ₂ O ₃ film on the particle surface, the surface of the soft magnetic particles having an irregular shape with an aspect ratio of 2 or more can be uniformly coated. ing. In addition, it is also shown that the dielectric strength can be adjusted by appropriately adjusting the content ratio of the Al ₂ O ₃ particles to the soft magnetic particles at the time of forming the Al ₂ O ₃ film formed on the SiO ₂ . As a result, the dielectric strength required by the desired device can be realized.

(Second Example)
(1) In the second embodiment, soft magnetic particles having an average particle diameter of 100 μm or less formed by pulverization are prepared, and a SiO ₂ film is formed on the surface of the soft magnetic particles by the sol-gel method as in the first embodiment. Formed.

(2) Next, the soft magnetic particles having the SiO ₂ film formed on the surface and the Al ₂ O ₃ fine particles having an average particle diameter of 10 nm to 1 μm were mixed. At this time, the content ratio of the Al ₂ O ₃ fine particles to the soft magnetic particles was between 2 wt% and 50 wt%.
(3) By putting the mixed powder into the hybridization apparatus and performing a film forming process at a predetermined rotation speed and time, an Al ₂ O ₃ film is further formed on the surface of the soft magnetic particles on which the SiO ₂ film is formed. A coating particle powder containing the formed coating particles was obtained.
In the obtained coating particles, the film thickness of the insulating layer containing the SiO ₂ film and the Al ₂ O ₃ film formed on the surface of the soft magnetic particles was 50 nm to 300 nm.

Rather than using spherical atomized powder (a coated particle powder having an aspect ratio of 2 or more and a particle ratio of less than 80% can be obtained) as the soft magnetic particle powder, it is a crushed powder having a distorted shape (aspect ratio of 2). When a coated particle powder having the above particle ratio of 80% or more can be obtained), the filling rate of magnetic particles at the time of powder compaction is improved. Therefore, the magnetic characteristics can be improved. The situation is shown in FIGS. 4 and 5. When molded under the same molding conditions, it is clearly obtained by using the pulverized powder having a distorted shape shown in FIG. 5 rather than the filling rate in the case of the coated particle powder obtained by using the atomized powder shown in FIG. 4 in the same volume. It can be seen that the coating particle powder has a higher filling rate. Each filling rate is about 70% for the atomized powder of FIG. 4 and about 85% for the distorted crushed powder of FIG. Further, 90% of the distorted soft magnetic particles in FIG. 5 are distributed between 1 μm and 32 μm in diameter. On the other hand, in the case of the atomized powder of FIG. 4 for comparison, 90% is distributed between 0.1 μm and 10 μm in particle size.

It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and the respective embodiments and / or embodiments. The effects of the examples can be achieved.

The insulating-coated coated particle powder and the method for producing the same according to the present invention provide an insulating film having a small variation in film thickness even when the pulverized powder having a distorted shape is used as the soft magnetic particle powder. It is possible to reduce eddy current and improve dielectric strength. In addition, it is possible to improve the rust preventive property in a device using soft magnetic particles that do not contain Cr having antioxidant performance inside. Therefore, even when the pulverized powder is used as the soft magnetic particle powder, it can be used for a soft magnetic device in which both improvement of magnetic characteristics and reduction of iron loss by reducing eddy current are required.

100 Coating particles 10 Soft magnetic particles 20 First inorganic insulating layer 21 Insulating fine particles 22 Metal fine particles 23 Semiconductor fine particles 30 Second inorganic insulating layer 40 Insulating layer

Claims (13)

With soft magnetic particles,
An insulating layer including a first inorganic insulating layer formed on the surface of the soft magnetic particles and a second inorganic insulating layer formed on the surface of the first inorganic insulating layer.
A coating particle powder containing coating particles comprising
When the cross section is observed, the ratio of the coating particles having an aspect ratio of 2 or more indicating the ratio of the maximum width to the minimum width of the coating particles is 80% or more.
Coated particle powder. At least one of the first inorganic insulating layer and the second inorganic insulating layer contains at least one selected from the group of Al ₂ O ₃ , Cr ₂ O ₃ , Nb ₂ O ₅ and Ti ₂ O _3. , The coating particle powder according to claim 1. The coating particle powder according to claim 1 or 2, wherein the ratio of the metal element contained in the insulating layer is 2 wt% to 50 wt% of the metal element contained in the soft magnetic particles. The coating particle powder according to any one of claims 1 to 3, wherein the metal element contained in the insulating layer is at least one of Al, Cr, Nb and Ti. The coating particle powder according to claim 4, wherein the insulating layer is a metal silicate film containing at least one element of Al, Cr, Nb and Ti. The coating particle powder according to any one of claims 1 to 3, wherein at least one of the first inorganic insulating layer and the second inorganic insulating layer is an insulating region formed of SiO ₂ . The coated particle powder according to any one of claims 1 to 6, wherein the soft magnetic particles are a nanocrystalline material, an amorphous material, or a mixture of a nanocrystalline material and an amorphous material. The coated particle powder according to any one of claims 1 to 7, which has an average particle size of 0.1 μm to 100 μm. A first inorganic insulating layer is formed on the surface of the soft magnetic particles,
Including forming a second inorganic insulating layer on the surface of the first inorganic insulating layer.
Method for producing coated particle powder. The first inorganic insulating layer is formed by a dry process,
The second inorganic insulating layer is formed by a wet process.
The method for producing a coated particle powder according to claim 9. The first inorganic insulating layer is formed by a wet process,
The second inorganic insulating layer is formed by a dry process.
The method for producing a coated particle powder according to claim 9. As the material of the first inorganic insulating layer used in the dry process, insulating fine particles having an average particle size of 10% or less of the average particle size of the soft magnetic particles are prepared.
The method for producing a coated particle powder according to claim 10. As a material for the second inorganic insulating layer used in the dry process, insulating fine particles having an average particle size of 10% or less of the average particle size of the soft magnetic particles are prepared.
The method for producing a coated particle powder according to claim 11.