JP2017135342A - Amorphous magnetic core, magnetic device, and method for manufacturing magnetic core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a small, inexpensive magnetic core in a complicated shape by using amorphous magnetic powder having poor moldability; a method for manufacturing the magnetic core; and a magnetic device using the magnetic core.SOLUTION: An amorphous magnetic core consists of a thermally cured molding product of a magnetic material. The magnetic material is a mixture of magnetic powder and a thermosetting binding resin. The magnetic powder is amorphous metal powder coated with an inorganic insulative material. The thermosetting binding resin is an epoxy resin including a latent hardening agent. The content of the magnetic powder is 97 mass% or more and 98 mass% or less to a total amount of the magnetic powder and the thermosetting binding resin, and the content of the thermosetting binding resin is 2 mass% or more and 3 mass% or less. In the amorphous magnetic core, internal pores are filled with the epoxy resin. The amorphous magnetic core is 70 MPa or more in radial crushing strength.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an amorphous magnetic core and a magnetic element, and a method for manufacturing an amorphous magnetic core, which are used in electrical equipment or electronic equipment such as an inductor, a transformer, an antenna (bar antenna), a choke coil, a filter, and a sensor. In particular, the present invention relates to an amorphous magnetic core with improved material strength and a method of manufacturing the same for use in applications involving vibration and impact such as transportation equipment and industrial equipment such as motorcycles and automobiles.

  In recent years, as electric and electronic devices have been reduced in size, increased in frequency, and increased in current, magnetic cores have been required to respond in the same way. However, the material properties of current mainstream ferrite materials have reached their limits. New magnetic core materials are being sought. For example, ferrite materials are being replaced by compressed magnetic materials such as sendust and amorphous metal, amorphous foil strips, and the like. However, the compressed magnetic material has poor moldability and low mechanical strength after firing. In addition, the amorphous foil strip is expensive to manufacture due to winding, cutting, and gap formation. For this reason, the practical application of these magnetic materials has been delayed.

  In order to provide a method for producing a small and inexpensive magnetic core having a variety of shapes and characteristics using magnetic powder having poor moldability, the present applicant is included in a resin composition used for injection molding. The magnetic powder is coated with an insulating material, and either a powder molded magnetic body or a powder magnet molded body is insert-molded into the resin composition, and the powder molded magnetic body or the powder magnet molded body is more than the injection molding temperature. A patent has been obtained on a method for producing a core part having a predetermined magnetic property containing a binder having a low melting point by injection molding (Patent Document 1).

  However, in the method described in Patent Document 1, when a magnetic powder such as amorphous metal is applied to a thermoplastic resin such as polyphenylene sulfide (PPS) that can be injection-molded, the limit of the magnetic powder that can be blended is about 88% by mass. . When the blending amount of the magnetic powder is further increased, there is a problem that sufficient mechanical strength as a core part cannot be obtained such as cracks. Moreover, since the compounding quantity of magnetic powder cannot be increased, there exists a problem that a magnetic component cannot be improved and size reduction of a core component cannot be achieved.

  Compression molding and thermosetting at least one magnetic powder selected from amorphous metal powder alone and amorphous metal powder coated with an insulating material, and a thermosetting binder resin composed of an epoxy resin cured by a latent curing agent The present applicant has filed a patent application regarding the magnetic core component (Patent Document 2).

  However, the magnetic core component disclosed in Patent Document 2 has a problem that the type of mold, the number of man-hours, and the equipment cost increase. In addition, there is no specific disclosure regarding the insulating material formed on the surface of the amorphous metal powder.

Japanese Patent No. 4766609 Japanese Patent Laying-Open No. 2015-185776

In order to compensate for the problem of reduced formability and material strength of compressed magnetic materials such as amorphous and sendust as magnetic core materials that replace ferrite, the powder density is increased by increasing the pressure applied to the green compact. Although it is conceivable to prevent improvement in formability and material strength, there are problems that the improvement effect cannot be obtained so much and that the manufacturing cost is increased or that it is not suitable for mass production.
The present invention has been made in view of such problems of the prior art, and an object thereof is to provide a small and inexpensive amorphous magnetic core, a manufacturing method thereof, and a magnetic element using the magnetic core.

  The amorphous magnetic core of the present invention is a magnetic core made of a thermosetting molded body of a magnetic material, and the magnetic material is a mixture of amorphous magnetic powder and a thermosetting binder resin. The amorphous magnetic powder constituting the mixture is an amorphous metal powder coated with an inorganic insulating material, and the thermosetting binder resin is an epoxy resin containing a latent curing agent. The amorphous magnetic core is characterized in that the inner vacancies when the magnetic powder is closely packed are filled with the thermosetting binder resin, and the crushing strength is 70 MPa or more. Here, the crushing strength is measured according to JIS Z 2507-2000.

  The blending ratio of the mixture composed of the amorphous magnetic powder and the thermosetting binder resin is 97% by mass to 98% by mass of the magnetic powder with respect to the total amount of the magnetic powder and the thermosetting binder resin. The curable binder resin is 2% by mass or more and 3% by mass or less.

  Moreover, the theoretical density ratio of the amorphous magnetic core of the present invention is 84 to 95%. The magnetic powder used as the raw material for the amorphous magnetic core is a particle that passes through a sieve having a sieve opening of 150 μm and does not pass through the sieve of 25 μm.

  The magnetic element of the present invention includes the amorphous magnetic core of the present invention and a coil wound around the amorphous magnetic core, and is incorporated in an electronic device circuit.

The method for producing an amorphous magnetic core according to the present invention includes the following steps.
(1) A mixing step in which the magnetic material is dry-mixed at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature;
(2) A pulverizing step of pulverizing the agglomerated cake produced by the mixing step to a particle size of 500 μm or less at room temperature;
(3) A primary compression molding step in which the pulverized powder is made into a primary compression molded body at room temperature using a mold at a pressure of 190 to 400 MPa;
(4) A secondary compression molding step in which the primary compression molded body is formed as a secondary compression molded body at a pressure of 190 to 400 MPa at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature;
(5) A curing step in which the secondary compression-compression molded body is thermally cured at 170 to 190 ° C. in the air.

  The magnetic core of the present invention is obtained by forming an amorphous metal powder coated with an inorganic insulating material into an agglomerated cake with a thermosetting binder resin, and further by thermosetting after primary compression molding and secondary compression molding. The internal voids when filled with the powder are fully filled with the thermosetting binder resin. As a result, it was possible to obtain a strong amorphous magnetic core having a crushing strength of 70 MPa or more with a thermosetting binder resin that suppresses the reduction of the filling rate of the amorphous magnetic powder and does not impair the magnetic characteristics and has a higher adhesive effect.

  The method for producing a magnetic core according to the present invention includes the primary and secondary compression molding steps in which a mold is used to form a compression molded body, and is therefore less expensive than injection molding. In addition, since the molding is performed at a relatively low molding pressure, the mold durability life can be extended.

It is a cross-sectional organization chart of a magnetic core. It is a manufacturing process figure of a magnetic core. It is a cross-sectional structure of a primary compression molding. 2 is a surface photograph of Example 1; 2 is a surface photograph of Comparative Example 1.

  In order to reduce the size, increase the frequency, and increase the current of electric / electronic devices, when trying to produce a magnetic core by sintering amorphous metal powder alone, a molding pressure of about 1000 to 2000 MPa is required during compression molding. become. However, by blending the thermosetting binder resin and filling the internal pores with the above-mentioned thermosetting binder resin when filled with amorphous magnetic powder, sufficient mechanical properties can be obtained without causing defects such as cracks. Strength was obtained. The present invention is based on such knowledge.

  The magnetic powder forming the magnetic core is an amorphous metal powder to which a ferromagnetic element such as iron, cobalt, nickel, or gadolinium is added. Examples of the amorphous metal powder include iron alloy series, cobalt alloy series, nickel alloy series, and mixed alloy series amorphous metal powder.

The amorphous metal powder is an amorphous metal powder coated with an insulating material (insulating layer). As the insulating material, metal oxides such as Al ₂ O ₃ , Y ₂ O ₃ , MgO, and ZrO ₂ , glass, or a mixture thereof can be used. Of these, glass materials are preferred. Among glass materials, low melting point glass is preferable. This is because it has a low softening temperature and can be fused to the amorphous metal powder to coat the surface of the powder.

The low melting point glass is not particularly limited as long as it does not react with the amorphous metal powder and softens at a temperature lower than the crystallization start temperature of the amorphous metal, preferably about 550 ° C. or less. For example, known low melting points such as lead glass such as PbO—B ₂ O ₃ glass, P ₂ O ₅ glass, ZnO—BaO glass, and ZnO—B ₂ O ₃ —SiO ₂ glass. Glass can be used. Preferably, a lead-free glass, P ₂ O ₅ based glass providing a low softening point is preferred. For example, P ₂ O ₅ is 60 to 80% by mass, Al ₂ O ₃ is 10% by mass or less, ZnO is 10 to 20% by mass, Li ₂ O is 10% by mass or less, and Na ₂ O is 10% by mass. The following composition can be used.

  As a method for forming the insulating coating, a powder coating method such as mechanofusion, a wet thin film preparation method such as electroless plating or a sol-gel method, or a dry thin film preparation method such as sputtering can be used. Among these, the powder coating method can be performed using, for example, a powder coating apparatus described in JP-A-2001-73062. According to this method, the amorphous metal powder and the low-melting glass powder are subjected to a strong compressive frictional force, and the surface of the amorphous metal powder has a low melting point due to the fusion of the amorphous metal powder and the low-melting glass powder and the welding of the glass powders. An amorphous metal powder coated with an inorganic insulating layer made of glass can be obtained.

  The composition of the insulated amorphous metal powder is preferably 0.3 to 6% by mass of the inorganic insulating material, more preferably 0.4 to 3% by mass of the inorganic insulating material so that the balance is amorphous metal powder. More preferably, the inorganic insulating material is 0.4 to 1% by mass so that the balance is amorphous metal powder, and the balance is amorphous metal powder. If necessary, 0.1 to 0.5% by mass of a stearate lubricant such as zinc stearate or calcium stearate may be added. Moreover, warm molding, metal mold | die lubrication molding, and the molding method combining these can also be utilized as needed.

  The insulated amorphous metal powder passes through a sieve having a sieve opening of 150 μm (100 mesh sieve according to the US ASTM standard) as a particle size before molding used as a raw material, and a 25 μm sieve (500 mesh according to the US ASTM standard). Particles that do not pass through the sieve. Preferably, the particles pass through a 106 μm sieve (US ASTM standard 150 mesh sieve) and do not pass through the 25 μm sieve (US ASTM standard 500 mesh sieve), and a more preferable range is the 90 μm sieve. It is a particle that passes through a 170-mesh sieve (US ASTM standard) and does not pass a 38-μm sieve (a 400-mesh sieve according to the US ASTM standard). The fine powder having a sieve opening of 25 μm makes it difficult to form an inorganic insulating film on the surface of the amorphous metal powder, and the amorphous metal powder that does not pass 150 μm has a large iron loss. That is, iron loss (eddy current loss) is reduced by using fine amorphous metal powder treated with an inorganic insulating coating (particles with a sieve opening passing through a 150 μm sieve but not passing through a 25 μm sieve). Became possible. Further, by forming a particularly thin and high-quality inorganic insulating film, it is possible to maintain the magnetic properties at the conventional product level without impairing the filling rate of the amorphous metal powder.

  Examples of the thermosetting binder resin that forms the magnetic core include an epoxy resin, a phenol resin, a urea resin, and an unsaturated polyester resin. Among these, it is preferable to use an epoxy resin. The binding resin is used for insulation and for binding.

  The epoxy resin that can be used in the present invention is a resin that can be used as an epoxy resin for bonding, and is preferably a resin having a softening temperature of 100 to 120 ° C. For example, an epoxy resin that is solid at room temperature, becomes a paste at 50 to 60 ° C., becomes fluid at 130 to 140 ° C., and starts a curing reaction when further heated can be used. This curing reaction starts at around 120 ° C., but the temperature at which the curing reaction is completed within a practical curing time, for example, 2 hours, is preferably 170 to 190 ° C. In this temperature range, the curing time is 45 to 80 minutes.

  Examples of the resin component of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydrogenated bisphenol A type epoxy resin, hydrogenated bisphenol F type epoxy resin, stilbene type epoxy resin, and triazine skeleton. -Containing epoxy resin, fluorene skeleton-containing epoxy resin, alicyclic epoxy resin, novolac-type epoxy resin, acrylic epoxy resin, glycidylamine-type epoxy resin, triphenolphenolmethane-type epoxy resin, alkyl-modified triphenolmethane-type epoxy resin, biphenyl-type Examples thereof include an epoxy resin, a dicyclopentadiene skeleton-containing epoxy resin, a naphthalene skeleton-containing epoxy resin, and an arylalkylene type epoxy resin.

The curing agent component of the epoxy resin is a latent epoxy curing agent. By using a latent epoxy curing agent, the softening temperature can be set to 100 to 120 ° C. and the curing temperature can be set to 170 to 190 ° C. Formation of an insulating coating film on the amorphous metal powder and subsequent compression Molding and thermosetting can be performed.
Examples of the latent epoxy curing agent include dicyandiamide, boron trifluoride-amine complex, and organic acid hydrazide. Of these, dicyandiamide that meets the above-mentioned curing conditions is preferred.
Moreover, hardening accelerators, such as tertiary amine, an imidazole, and an aromatic amine, can be included with a latent epoxy hardening | curing agent.

  The epoxy resin containing the latent curing agent that can be used in the present invention has curing conditions of 160 ° C. for 2 hours, 170 ° C. for 80 minutes, 180 ° C. for 55 minutes, 190 ° C. for 45 minutes, and 200 ° C. for 30 minutes. Thus, a latent curing agent is blended.

  The blending ratio of the amorphous metal powder and the epoxy resin is 97% by mass or more and 98% by mass or less for the amorphous metal powder and 2% by mass or more and 3% by mass or less for the epoxy resin with respect to the total amount of these. When the epoxy resin content is less than 2% by mass, it is difficult to form an insulating coating. When the epoxy resin content exceeds 3% by mass, the magnetic properties are deteriorated and a resin-rich coarse aggregate is generated.

The cross-sectional structure of the magnetic core of the present invention is shown in FIG. FIG. 1 is a cross-sectional view of a magnetic core cut at an arbitrary cross section.
The magnetic core 1 is closely packed with an amorphous metal powder 2 having an inorganic insulating coating 3 on the surface, and the internal pores are fully filled with a thermosetting binder resin 4. The magnetic core 1 is manufactured by primary compression molding and secondary compression molding described later, and the theoretical density ratio (%) of the morphous magnetic core is 84 to 95%, preferably 84 to 92%. Here, the theoretical density ratio is expressed by the following equation.

Theoretical density ratio (%) = [(density of magnetic core) / (theoretical density)] × 100

Here, the density of the magnetic core is the density of the magnetic core that is the product, and the theoretical density is a density calculated by assuming that the amorphous metal powder is packed as a spherical particle and closest packed.

The magnetic element of the present invention is a magnetic element that includes the amorphous magnetic core of the present invention and a coil wound around the amorphous magnetic core and is incorporated in an electronic device circuit.
An enameled wire can be used as the winding forming the coil, and types thereof are urethane wire (UEW), formal wire (PVF), polyester wire (PEW), polyesterimide wire (EIW), polyamideimide wire ( AIW), polyimide wire (PIW), a double coated wire combining these, or a self-bonding wire, a litz wire, or the like can be used. A round wire or a square wire can be used as the cross-sectional shape of the enameled wire. As the conductor, a metal having excellent electrical conductivity such as copper, aluminum, gold, silver or the like can be used.
As a coil winding method, helical winding or toroidal winding can be adopted. In the case of an ultra-small magnetic core, a cylindrical core, a square-shaped core, or a plate-shaped core that is not a donut core used for a toroidal coil core can be used.

The amorphous magnetic core and / or magnetic element of the present invention is a core component of a soft magnetic material used for power circuits, filter circuits, switching circuits, etc. of automobiles including motorcycles, industrial equipment, and medical equipment, such as inductors and transformers. Can be used as core parts such as antennas, choke coils, filters, and magnetic elements Moreover, it can be used as a magnetic core and a magnetic element for surface mounting components.
In particular, it is suitable as a magnetic core and a magnetic element used for applications involving vibrations and shocks in transportation equipment such as motorcycles and automobiles and industrial equipment.

The amorphous magnetic core can be manufactured by compression molding and thermosetting a mixture of an amorphous metal powder and an epoxy resin containing a curing agent.
A method of manufacturing the magnetic core will be described with reference to FIG. FIG. 2 is a manufacturing process diagram.
The above-described amorphous metal powder, which is a magnetic material with an inorganic insulating coating, and an epoxy resin in which the above-described latent curing agent is already blended are prepared. The amorphous metal powder is preliminarily adjusted to a particle that does not pass through a sieve of 150 mesh (a sieve opening of 106 μm) and a sieve of 500 mesh (a sieve opening of 25 μm) by a classifier.

  In the mixing step, the amorphous metal powder and the epoxy resin are dry-mixed at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature. In this mixing step, first, the amorphous metal powder and the epoxy resin are sufficiently mixed at room temperature using a blender or the like. Next, the mixed mixture is put into a mixer such as a kneader and heated and mixed at the softening temperature (100 to 120 ° C.) of the epoxy resin. By this heating and mixing process, an insulating film of epoxy resin is formed on the surface of the amorphous metal powder. At this stage, the epoxy resin is uncured.

  The contents heated and mixed using a mixer such as a kneader are agglomerated cakes. The pulverization step is a step of obtaining amorphous metal powder having an epoxy resin insulating film formed on the surface thereof by pulverizing and sieving the agglomerated cake at room temperature. For the pulverization, a Henschel mixer is preferable, and the particle size is preferably 500 μm or less.

The compression molding step is a step of compression molding a magnetic core using a predetermined mold, and in the method of the present invention, the magnetic core is molded by a primary compression molding step and a secondary compression molding step.
The primary compression molding step is a step of converting the pulverized powder into a primary compression molded body at room temperature using a mold at a pressure of 190 to 400 MPa, preferably 196 to 392 MPa. FIG. 3 shows a cross-sectional structure of the primary compression molded body.
The magnetic core 1 ′ is a compression molded body of amorphous metal powder 2 having an inorganic insulating coating 3 and a thermosetting binder resin coating 4 on the surface. The magnetic core 1 ′ can reduce the pressure during compression molding by the thermosetting binder resin film 4, and has a cross-sectional structure having the internal pores 5 without destroying the electrical insulation of the inorganic insulating film 3. Become. Due to the fluidity of the epoxy resin film which is a thermosetting binder resin, the moldability is remarkably improved as compared with the case of the amorphous metal powder alone, and the molded article can be easily handled.

  The secondary compression molding process is a process in which the primary compression molded body is compression molded at a pressure of 190 to 400 MPa at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature. After the primary compression molded body is preheated to 80 to 120 ° C., it is quickly inserted into a mold that is also kept warm at 80 to 120 ° C. and recompressed at a pressure of 190 to 400 MPa, preferably 196 to 392 MPa. To do. By this secondary compression molding, the epoxy resin film layer flows, and the amorphous metal powder can be brought into close contact and densified. By forming an epoxy resin film and recompressing warmly, the reduction of the filling rate of the amorphous metal magnetic powder is suppressed and the magnetic properties are not impaired. An excellent magnetic core can be obtained.

The curing step is a step in which the magnetic core taken out from the mold is heated and cured at a temperature of 170 to 190 ° C. in air for 45 to 80 minutes. This is because if it is less than 170 ° C., it takes a long time to cure, and if it exceeds 190 ° C., deterioration starts. Heat curing is preferably performed in a nitrogen atmosphere.
After heat curing, an amorphous magnetic core is obtained by performing cutting, barrel processing, rust prevention treatment, etc. as necessary.

Example 1
Room temperature in a blender at a ratio of 98.0 g of amorphous metal magnetic powder (Fe-Si-B amorphous metal) whose particle surface is covered with an inorganic insulating coating and 2.0 g of epoxy resin powder containing dicyandiamide as a curing agent For 10 minutes. The amorphous metal magnetic powder used was a powder that passed through a 150 μm sieve and did not pass through a 25 μm sieve. The mixture was put into a kneader and heated and kneaded at 110 ° C. for 15 minutes. The cake agglomerated from the kneader was taken out and cooled, and then pulverized with a pulverizer. Next, compression molding was performed using a mold at a molding pressure of 294 MPa at room temperature to obtain a primary compression molded body. The primary compression molded body was preheated at 100 ° C. in air. The primary compression-molded body was quickly inserted into a mold heated to 100 ° C. in advance, and compression-molded at a molding pressure of 294 MPa while maintaining a temperature of 100 ° C. The compression molded product was taken out from the mold and cured in a nitrogen atmosphere at a temperature of 180 ° C. for 1 hour. Furthermore, an amorphous magnetic core was manufactured by cutting. The shape of the amorphous magnetic core is a flat cylindrical shape having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm.

  The crushing strength of the obtained magnetic core was measured. The measurement was performed in accordance with JIS Z 2507-2000 by continuously applying a diametrical load to the amorphous magnetic core until breakage occurred, and the load at the time of breakage was measured.

  Further, a toroidal test piece for measuring magnetic properties was produced under the above conditions, and the magnetic properties were measured. The test piece is a flat cylindrical magnetic core having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm. The number of windings is adjusted so that the inductance of the magnetic core is 10 μH. The inductance when the frequency was changed was measured with the inductance at 100% being 100%. Further, the iron loss ratio and the DC superposition characteristics were measured using the inductors under the conditions shown in Table 1. As for the iron loss ratio, the dimensions, current, and inductance of the inductor were measured under the same conditions as in each of the comparative examples. Moreover, the moldability was evaluated by a surface photograph. The results are shown in Table 1 and FIG.

Example 2
Same as Example 1 except that 97.0 g of amorphous metal magnetic powder (Fe-Si-B amorphous metal) whose particle surface is covered with an inorganic insulating coating and 3.0 g of epoxy resin powder containing dicyandiamide as a curing agent. A flat cylindrical amorphous magnetic core having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm was manufactured under the conditions described above. The crushing strength and magnetic properties were measured under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 1
Example 1 using the amorphous metal magnetic powder used in Example 1 except that compression molding is performed at a molding pressure of 1764 MPa without blending an epoxy resin and without performing secondary compression molding in warm. A flat cylindrical amorphous magnetic core having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm was manufactured in the same manner. The crushing strength and magnetic properties were measured under the same conditions as in Example 1. Moreover, the moldability was evaluated by a surface photograph. The results are shown in Table 1 and FIG.

Comparative Example 2
The internal pores of the magnetic core produced in Comparative Example 1 were sealed with acrylic resin. The crushing strength and magnetic properties were measured under the same conditions as in Example 1. The results are shown in Table 1.

Comparative Example 3
A flat cylindrical magnetic core having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm was produced in the same manner as in Comparative Example 2 except that the amorphous metal powder was replaced with Sendust powder. The crushing strength and magnetic properties were measured under the same conditions as in Example 1. The results are shown in Table 1.

Examples 3-8
A flat cylindrical amorphous magnetic core having an inner diameter of 7.6 mmφ, an outer diameter of 12.6 mmφ, and a thickness of 5.7 mm is manufactured in the same manner as in Example 1 using the amorphous metal magnetic powder and epoxy resin used in Example 1. did. The theoretical density ratio (%) was calculated by measuring the density of the magnetic core by the method described above. The results are shown in Table 2 together with the results of Comparative Example 1.

  Since the magnetic core of the present invention uses amorphous metal powder and a thermosetting binder resin, the compressibility and formability are remarkably improved and the mechanical strength is excellent. As a result, it can be used for electronic devices that will be reduced in size and weight in the future.

DESCRIPTION OF SYMBOLS 1 Magnetic core 2 Amorphous metal powder 3 Inorganic insulating coating 4 Thermosetting binder resin coating 5 Internal void | hole

Claims (6)

A magnetic core comprising a thermosetting molded body of magnetic material,
The magnetic material is a mixture of magnetic powder and thermosetting binder resin;
The magnetic powder is an amorphous metal powder coated with an inorganic insulating material,
The thermosetting binder resin is an epoxy resin containing a latent curing agent,
Internal vacancies when the magnetic powder is closely packed are filled with the thermosetting binder resin,
An amorphous magnetic core having a crushing strength of 70 MPa or more.   97 mass% or more and 98 mass% or less of said magnetic powder, and 2 mass% or more and 3 mass% or less of said thermosetting binder resin with respect to the total amount of said magnetic powder and said thermosetting binder resin, respectively. The amorphous magnetic core according to claim 1, wherein the amorphous magnetic core is formed.   The amorphous magnetic core according to claim 1 or 2, wherein a theoretical density ratio of the magnetic core is 84 to 95%.   4. The amorphous magnetic core according to claim 1, wherein the magnetic powder is a particle that passes through a sieve having a sieve opening of 150 μm and does not pass through a sieve having a sieve opening of 25 μm. A magnetic element including an amorphous magnetic core and a coil wound around the amorphous magnetic core, and incorporated in an electronic device circuit,
The magnetic element according to any one of claims 1 to 4, wherein the magnetic core is the amorphous magnetic core. A method for producing an amorphous magnetic core according to any one of claims 1 to 4,
A mixing step of dry-mixing the magnetic material at a temperature equal to or higher than the softening temperature of the epoxy resin and lower than the thermosetting start temperature;
A pulverizing step of pulverizing the agglomerated cake produced by the mixing step to a particle size of 500 μm or less at room temperature;
A primary compression molding step in which the pulverized powder is made into a primary compression molded body at a pressure of 190 to 400 MPa at room temperature using a mold;
A secondary compression molding step in which the primary compression molded body is a secondary compression molded body at a pressure of 190 to 400 MPa at a temperature not lower than the softening temperature of the epoxy resin and lower than the thermosetting start temperature;
The manufacturing method of the amorphous magnetic core characterized by including the hardening process which thermosets the said secondary compression molding at 170-190 degreeC in the air.