JP2015043375A - Soft magnetic material composition, manufacturing method thereof, magnetic core, and coil-type electronic component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a soft magnetic material composition excellent in strength, a method for producing the same, a magnetic core, and a coil-type electronic component. A soft magnetic composition according to the present invention is a soft magnetic composition having a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles, the soft magnetic composition comprising: The alloy particles are made of Fe-Si-M soft magnetic alloy or Fe-Ni-Si-M soft magnetic alloy, and the M is at least one selected from Cr, Al, Ti, Co and Ni. The grain boundary is characterized in that at least one of Bi and V is present. [Selection figure] None

Description

  The present invention relates to a soft magnetic composition, a method for producing the same, a magnetic core, and a coil-type electronic component.

  The metal magnetic body has an advantage that a high saturation magnetic flux density can be obtained as compared with ferrite. As such a metal magnetic material, a magnetic material using a soft magnetic alloy or the like is known.

  Such a soft magnetic alloy has been desired to be improved in mechanical strength when formed into a molded body in order to expand the application range as a magnetic material. Patent Document 1 proposes a magnetic material having high strength using a Fe—Si—M soft magnetic alloy (where M is a metal element that is more easily oxidized than iron).

  However, as the electronic components are further downsized and thinned, the aspect proposed in Patent Document 1 is still insufficient in strength, and further improvement in mechanical strength has been desired.

Japanese Patent No. 5082002

  The present invention has been made in view of such circumstances, and an object thereof is to provide a soft magnetic composition having excellent strength, a method for producing the same, a magnetic core, and a coil-type electronic component.

In order to achieve the above object, the soft magnetic composition according to the present invention comprises:
A soft magnetic composition having a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles,
The soft magnetic alloy particles are composed of Fe-Si-M soft magnetic alloy or Fe-Ni-Si-M soft magnetic alloy;
M is at least one selected from Cr, Al, Ti, Co and Ni;
At least one of Bi and V exists in the grain boundary.

  The soft magnetic composition according to the present invention exhibits excellent strength due to the presence of at least one of Bi and V at the grain boundaries of the soft magnetic alloy particles.

Preferably, the contents of Bi and V are 0.1 to 5.0% by mass in terms of Bi ₂ O ₃ or V ₂ O ₅ with respect to 100% by mass of the soft magnetic alloy.

  Preferably, Si further exists in the grain boundary.

  The magnetic core according to the present invention is composed of the soft magnetic material composition described above.

Furthermore, the coil-type electronic component according to the present invention has the magnetic core.
Although it does not specifically limit as a coil type electronic component, Electronic components, such as an inductor component, the coil component for EMC, a transformer component, are illustrated. In particular, it can be suitably used for DC-DC converters such as mobile phones.

FIG. 1 shows a magnetic core according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a main part of the magnetic core shown in FIG. FIG. 3 is an enlarged cross-sectional view of the main part of the magnetic core shown in FIG.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  The magnetic core for coil-type electronic components according to the present embodiment is a dust core formed by dust molding. The compacting is a method for obtaining a compact by filling a material containing a soft magnetic alloy powder in a die of a press machine and pressurizing the material with a predetermined pressure.

  As the shape of the magnetic core according to the present embodiment, in addition to the toroidal type shown in FIG. 1, FT type, ET type, EI type, UU type, EE type, EER type, UI type, drum type, pot type, cup Examples include molds. A desired coil-type electronic component can be obtained by winding a predetermined number of turns around the magnetic core.

  The magnetic core for coil-type electronic components according to this embodiment is composed of the soft magnetic material composition according to this embodiment.

The soft magnetic composition according to the present embodiment is a soft magnetic composition having a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles,
The soft magnetic alloy particles are composed of Fe-Si-M soft magnetic alloy or Fe-Ni-Si-M soft magnetic alloy;
M is at least one selected from Cr, Al, Ti, Co and Ni;
At least one of Bi and V exists in the grain boundary.

  According to the soft magnetic composition according to the present embodiment, by satisfying the above configuration, the strength can be improved while maintaining good magnetic characteristics (such as initial permeability μi) or specific resistance.

  As shown in FIG. 2, the soft magnetic composition according to the present embodiment includes a plurality of soft magnetic alloy particles 21 and grain boundaries 30 existing between the soft magnetic alloy particles.

  As shown in FIG. 3, in this embodiment, the region 40 of bismuth (Bi) and / or vanadium (V) exists between the grain boundary 30 formed between two particles or between three or more particles. It exists in the grain boundary 31 (3 points etc.). Due to the presence of Bi and / or V, the magnetic core according to the present embodiment exhibits excellent strength.

  In particular, in the case of the soft magnetic composition according to the present embodiment in which any one of Bi and V exists at the grain boundary, compared to the case of the soft magnetic composition in which neither Bi nor V exists at the grain boundary. Thus, the strength improvement rate is preferably 3% or more, more preferably 5% or more, and further preferably 10% or more.

  In the soft magnetic composition according to this embodiment, preferably, the concentration of Bi and / or V at the grain boundary is higher than that in the soft magnetic alloy particles, and more preferably, Bi and / or V is soft. It is not substantially contained inside the magnetic alloy particles.

  In the soft magnetic composition according to the present embodiment, at least one of Bi and V is present at the grain boundary, and more preferably, at least Bi is present at the grain boundary. The presence of Bi at the grain boundary makes it possible to maintain high magnetic properties while improving strength.

  Bi and V are not necessarily present so as to cover the entire surface of the soft magnetic alloy particles, and may be formed on a part of the surface of the soft magnetic alloy particles.

  In the present embodiment, the form of bismuth (Bi) and vanadium (V) present at the grain boundaries is not particularly limited. For example, Bi and V metals, Bi and V oxides, or It may exist as a composite oxide of Bi and V, etc., with components constituting the soft magnetic alloy and other components (such as binders and additives).

  In FIG. 3, for convenience, the Bi and / or V regions 40 are shown in the form of particles, but are not necessarily in the form of particles. For example, as the phase containing Bi or V, the soft magnetic alloy particles 21 and the particles It may be formed near the interface with the boundary 30. Examples of such a phase containing Bi or V include an oxide phase containing a part of components constituting the soft magnetic alloy particles described later.

  In the present invention, the oxide phase and the composite oxide phase are broad concepts including an amorphous phase, a crystal phase, and a mixed phase thereof.

  In the present embodiment, the method for determining whether or not at least one of Bi and V is present on the surface and grain boundary of the soft magnetic alloy particles is not particularly limited. For example, a mapping image of Bi or V is analyzed. You may judge by doing.

  The distinction between soft magnetic alloy particles and grain boundaries can be made by observing the magnetic core using a scanning transmission electron microscope (STEM). Specifically, a cross section of the dielectric layer is photographed with a STEM to obtain a bright field (BF) image. In this bright field image, a region present between the soft magnetic alloy particles and the soft magnetic alloy particles and having a contrast different from that of the soft magnetic alloy particles is defined as a grain boundary. The determination of whether or not the contrast is different may be made by visual observation, or may be made by software or the like that performs image processing.

  In addition, by defining an observation point from an arbitrary cross section of the magnetic core and performing EDS analysis or EPMA analysis, a location where Bi and V are present can be observed. Specifically, a mapping image can be obtained using the qualitative analysis function of these analyses. In the mapping image, it is possible to distinguish a portion where there are many elements to be observed by color. Whether Bi or V is present at the grain boundary 30 can be determined by visual observation or analysis software. Furthermore, according to these analyses, it is possible to confirm the concentration distribution of various components inside the alloy particles and on the surface thereof. Further, according to STEM analysis, it is possible to specify whether the phase formed on the surface of the alloy particle is amorphous or crystalline.

  In addition, in the soft magnetic composition according to the present embodiment, elements other than Bi and V (Fe, Si, M, etc.) can be obtained by the same method as in the case of Bi and V, and the surface of the soft magnetic alloy particles. It can be determined whether or not various elements are present at the grain boundaries.

In the soft magnetic composition according to this embodiment, the content of bismuth (Bi) and vanadium (V) is 0 in terms of Bi ₂ O ₃ or V ₂ O _{5 with} respect to 100% by mass of the soft magnetic alloy. 0.1 to 10% by mass, more preferably 0.1 to 5.0% by mass. By satisfying the above ranges, in the magnetic core according to the present embodiment, the magnetic properties (particularly the initial magnetic permeability μi) or the specific resistance are maintained well, and the moldability (particularly the bending strength) is improved. Can be made.

More preferably, the soft magnetic composition according to this embodiment contains at least Bi. In the soft magnetic composition according to this embodiment, the content of bismuth (Bi) is preferably 0.1 to 5.0% by mass in terms of Bi ₂ O _{3 with} respect to 100% by mass of the soft magnetic alloy. More preferably, the content is 0.1 to 1.0% by mass. By satisfying the above range, the magnetic properties (particularly, the initial magnetic permeability μi) can be kept high while improving the strength.

  In the soft magnetic composition according to this embodiment, when neither bismuth (Bi) nor vanadium (V) is present at the grain boundaries, sufficient strength tends not to be obtained. Further, as the content of bismuth (Bi) and / or vanadium (V) increases, the strength tends to improve. However, when the content is too large, the magnetic properties (particularly, the initial magnetic permeability μi) tend to decrease. is there.

The soft magnetic alloy particles according to the present embodiment are composed of an Fe—Si—M based soft magnetic alloy or an Fe—Ni—Si—M based soft magnetic alloy.
Here, M is at least one selected from chromium (Cr), aluminum (Al), titanium (Ti), cobalt (Co), and nickel (Ni).

  Among them, in the present embodiment, the soft magnetic alloy particles are Fe-Si-Cr soft magnetic alloy, Fe-Si-Al soft magnetic alloy, Fe-Ni-Si-Co soft magnetic alloy, Fe-Ni-Si. -Co-M type soft magnetic alloy is preferable, and Fe-Si-Cr type soft magnetic alloy is more preferable.

  By using such soft magnetic alloy particles, the soft magnetic composition according to the present embodiment has excellent formability (particularly bending strength) while maintaining good magnetic properties (initial permeability μi, etc.) or specific resistance. ) Can be improved. Moreover, since it can shape | mold with a comparatively low shaping pressure in the case of pressure molding, the burden on a metal mold | die can further be aimed at and productivity can be improved.

  When M is chromium (Cr), the Fe—Si—Cr soft magnetic alloy contains 0.1 to 9% by mass of silicon in terms of Si and 0.1 to 15% by mass of chromium in terms of Cr. And it is preferable that the remainder is comprised with iron (Fe). More preferably, silicon is 1.4 to 9% by mass in terms of Si, particularly preferably 4.5 to 8.5% by mass, and chromium is 1.5 to 8% by mass in terms of Cr, particularly preferably 3 to 3. It is preferable that the content is 7% by mass and the balance is composed of iron (Fe).

  When M is aluminum (Al), the Fe-Si-Al soft magnetic alloy contains silicon in an amount of 0.1 to 15% by mass in terms of Si and aluminum in an amount of 0.1 to 10% by mass in terms of Al. And it is preferable that the remainder is comprised with iron (Fe).

  When M is cobalt (Co), in the Fe—Ni—Si—Co based soft magnetic alloy, silicon is 0.1 to 3.0% by mass in terms of Si and nickel is 40.0 to in terms of Ni. It is preferable that 50.0% by mass, cobalt is contained in an amount of 0.1 to 5.0% by mass in terms of Co, and the balance is composed of iron (Fe).

  The average crystal particle diameter of the soft magnetic alloy particles according to this embodiment is preferably 30 to 60 μm. By making the average crystal particle diameter within the above range, it is possible to easily realize a thin magnetic core.

  In the soft magnetic composition according to the present embodiment, an oxide phase including a part of the components constituting the soft magnetic alloy particles is formed on the surface of the soft magnetic alloy particles 21 (interface with the grain boundaries 30). May be.

  Such an oxide phase is not particularly limited, and may be an oxide phase containing oxygen and an element other than oxygen, and may be a composite oxide phase containing two or more elements other than oxygen. . Examples of such an oxide phase and a composite oxide phase include an amorphous phase containing a part of components constituting the soft magnetic alloy particles.

  Here, when the soft magnetic alloy particles are Fe—Si—Cr based soft magnetic alloys, the oxide phase is a Si—Cr composite oxide phase in which there is more Cr than in the soft magnetic alloy particles 21. There may be. The Si—Cr composite oxide phase is not particularly limited, and examples thereof include an amorphous phase containing Si and Cr.

  In the soft magnetic composition according to the present embodiment, the oxide phase may further contain one or both of Bi and V. As such an oxide phase containing Bi and V, for example, an oxide phase in which Bi oxide, V oxide, or the like is dispersed, or a part of components in which Bi or V constitutes soft magnetic alloy particles And a complex oxide phase formed by chemically bonding to the compound.

  In the present embodiment, the oxide phase is not necessarily formed so as to cover the entire surface of the soft magnetic alloy particles, and may be formed on a part of the surface of the soft magnetic alloy particles. . The thickness of the oxide phase may not be uniform, and the composition may not be uniform.

  Further, on the surface of the soft magnetic alloy particles according to the present embodiment, the presence or absence of the oxide phase and the thickness thereof are determined by the alloy composition of the soft magnetic alloy particles and the binder in the method of manufacturing a magnetic core (molded body) described later. It can be adjusted by controlling the type, the amount added, other added components, the heat treatment temperature and atmosphere of the molded body, and the like.

  In the soft magnetic composition according to this embodiment, the soft magnetic alloy particles 21 may be directly connected to the adjacent soft magnetic alloy particles 21 via the oxide phase.

The soft magnetic composition according to this embodiment may contain components such as carbon (C) and zinc (Zn) in addition to the constituent components of the soft magnetic alloy particles.
Note that C is considered to be derived from an organic compound component used in the process of producing the soft magnetic composition. Further, it is considered that Zn is derived from zinc stearate added to the mold in order to reduce the punching pressure of the apparatus when the soft magnetic composition is obtained by compacting.

  The content of carbon (C) in the soft magnetic composition according to the present embodiment is preferably less than 0.05% by mass, and more preferably 0.01 to 0.04% by mass. If the C content is too large, sufficient strength as a magnetic core tends to be not obtained.

  The content of zinc (Zn) in the soft magnetic composition according to this embodiment is preferably 0.004 to 0.2% by mass, more preferably 0.01 to 0.2% by mass. Even if the Zn content is too large or conversely too small, there is a tendency that sufficient strength as a magnetic core cannot be obtained.

  The soft magnetic composition according to the present embodiment may contain inevitable impurities in addition to the above components.

  In still another embodiment, it is preferable that Si is further present at the grain boundary of the soft magnetic composition. Thereby, intensity | strength can be improved further, maintaining a high magnetic characteristic. In particular, even when molded at a relatively low molding pressure, sufficient strength as a magnetic core can be obtained, so that the burden on the mold is reduced and productivity is improved.

  In the soft magnetic composition according to the present embodiment, Si contains Si at a grain boundary 30 formed between two particles or a grain boundary 31 (such as a triple point) existing between three or more particles. It is considered that the phase 50 exists.

  Thus, since the phase 50 containing Si exists at the grain boundary, the magnetic core according to the present embodiment has sufficient strength as the magnetic core even when it is molded at a relatively low molding pressure. be able to. Further, such a phase 50 containing Si plays a role of an insulator by being present at the grain boundary.

  The Si-containing phase 50 according to the present embodiment is preferably a Si oxide phase or a Si composite oxide phase. The Si oxide phase and the Si composite oxide phase are not particularly limited, and examples thereof include an amorphous phase containing Si, amorphous silicon, silica, and an Si-M composite oxide.

  In the soft magnetic composition according to the present embodiment, it is preferable that the Si-containing phase 50 is also present on the surface of the soft magnetic alloy particle 21 (interface with the grain boundary 30).

  For example, when the soft magnetic alloy particles are Fe—Si—Cr soft magnetic alloy, the Si-containing phase is preferably a Si—Cr composite oxide phase. The Si—Cr composite oxide phase is not particularly limited, but contains more Cr than the soft magnetic alloy particles 21.

  The Si-containing phase 50 according to the present embodiment is preferably made of an amorphous material. Note that a part thereof may be made of a crystalline material.

The thickness of the phase containing Si according to the present embodiment is preferably 0.01 to 0.2 μm, more preferably 0.01 to 0.1 μm.
The Si-containing phase 50 does not necessarily have to be formed so as to cover the entire surface of the soft magnetic alloy particles, and may be formed on a part of the surface of the soft magnetic alloy particles. Further, the thickness of the phase 50 containing Si may not be uniform, and the composition may not be uniform.

  The presence / absence and thickness of the Si-containing phase 50 according to the present embodiment depends on the type and amount of the binder, other additive components, the heat treatment temperature and atmosphere of the molded body, etc. in the magnetic core manufacturing method described later. Can be controlled.

Next, an example of a method for manufacturing a magnetic core according to the present embodiment will be described.
The magnetic core of the present embodiment can be produced by heat-treating a molded body containing soft magnetic alloy powder and a binder (binder resin). Hereinafter, the preferable manufacturing method of the magnetic core of this embodiment will be described in detail.

The manufacturing method according to this embodiment is preferably
A step of mixing a soft magnetic alloy powder, a low melting point oxide, and a binder to obtain a mixture;
After the mixture is dried to obtain a lump-shaped dried body, the dried body is pulverized to form granulated powder,
Molding the mixture or granulated powder into the shape of the powder magnetic core to be produced, and obtaining a molded body;
And heating the obtained molded body to cure the binder and obtain a dust core.

  The dust core obtained by the manufacturing method according to the present embodiment can particularly improve the bending strength.

The reason why such an effect is obtained is not clear, but the following mechanism is conceivable.
In the step of heating the molded body, the low melting point oxide becomes a high temperature state and becomes a liquid phase in the gap (grain boundary region) of the soft magnetic alloy particles, thereby strengthening the bond between the metal particles and It is thought that the strength is improved.

  As the soft magnetic alloy powder, a powder containing alloy particles composed of an Fe-Si-M soft magnetic alloy or an Fe-Ni-Si-M soft magnetic alloy can be used.

  The shape of the soft magnetic alloy powder is not particularly limited, but is preferably spherical or elliptical from the viewpoint of maintaining inductance up to a high magnetic field range. Among these, an elliptical shape is desirable from the viewpoint of increasing the strength of the dust core. The average particle size of the soft magnetic alloy powder is preferably 10 to 80 μm, more preferably 30 to 60 μm. If the average particle size is too small, the magnetic permeability tends to be low, the magnetic properties as a soft magnetic material tend to be lowered, and handling becomes difficult. On the other hand, if the average particle size is too large, eddy current loss tends to increase and abnormal loss tends to increase.

  The soft magnetic alloy powder can be obtained by a method similar to a known method for preparing a soft magnetic alloy powder. At this time, it can be prepared using a gas atomizing method, a water atomizing method, a rotating disk method or the like. Among these, the water atomization method is preferable in order to easily produce a soft magnetic alloy powder having desired magnetic characteristics.

  The low melting point oxide preferably contains at least one of Bi and V. Thereby, at least one of Bi and V can be efficiently formed at the grain boundary of the obtained soft magnetic composition. Examples of such a low melting point oxide include bismuth oxide and vanadium oxide.

The addition amount of such a low melting point oxide is preferably 0.1 to 5.0 parts by mass in terms of Bi ₂ O ₃ or V ₂ O _{5 with} respect to 100 parts by weight of the soft magnetic alloy powder. By satisfy | filling the said range, Bi and V can be formed efficiently in the grain boundary of a soft-magnetic composition, and the intensity | strength of a magnetic core can be improved.

More preferably, the low melting point oxide contains at least Bi. The amount of the low melting point oxide contained in such bismuth (Bi) is preferably 0.1 to 5.0% by mass in terms of Bi ₂ O _{3 with} respect to 100% by mass of the soft magnetic alloy. Preferably it is 0.1-1.0 mass%. By satisfying the above range, the magnetic properties (particularly, the initial magnetic permeability μi) can be kept high while improving the strength.

  As the binder, known resins can be used, and examples thereof include various organic polymer resins, silicone resins, phenol resins, epoxy resins, and water glass.

  Especially, in this embodiment, Preferably, what contains a silicone resin as a binder is used. By using silicone as the binder, a Si-containing phase is effectively formed at the grain boundary of the soft magnetic composition. A magnetic core composed of such a soft magnetic composition exhibits a sufficient strength even when molded with a relatively low molding pressure.

  In this case, the binder can be used alone or in combination with other binders. From the viewpoint of preferably limiting the carbon (C) content in the soft magnetic composition to less than 0.05% by mass, it is preferable to use a binder mainly composed of a silicone resin. When the content of C in the soft magnetic composition is too large, the strength of the obtained magnetic core tends to decrease.

  The amount of the binder added varies depending on the required characteristics of the magnetic core, but preferably 1 to 10 parts by weight can be added, more preferably 100 parts by weight of the soft magnetic alloy powder. 3 to 9 parts by weight with respect to 100 parts by weight of the soft magnetic alloy powder. When the amount of the binder added is too large, the magnetic permeability tends to decrease and the loss tends to increase. On the other hand, if the amount of the binder added is too small, it tends to be difficult to ensure insulation.

  The addition amount of the silicone resin is preferably 3 to 9 parts by weight with respect to 100 parts by weight of the soft magnetic alloy powder. When the addition amount of the silicone resin is too small, a phase containing Si is hardly formed at the grain boundary of the soft magnetic composition, and the strength as a molded product tends to be lowered.

Moreover, you may add an organic solvent to the said mixture or granulated powder as needed in the range which does not inhibit the effect of this invention.
The organic solvent is not particularly limited as long as it can dissolve the binder, and examples thereof include various solvents such as toluene, isopropyl alcohol, acetone, methyl ethyl ketone, chloroform, and ethyl acetate.

  In addition, various additives, lubricants, plasticizers, thixotropic agents, and the like may be added to the mixture or the granulated powder as necessary, as long as the effects of the present invention are not hindered.

  Examples of the lubricant include aluminum stearate, barium stearate, magnesium stearate, calcium stearate, zinc stearate and strontium stearate. These are used singly or in combination of two or more. Among these, it is preferable to use zinc stearate as a lubricant from the viewpoint that so-called spring back is small.

  When a lubricant is used, the amount added is preferably 0.1 to 0.9 parts by weight, more preferably 100 parts by weight of soft magnetic alloy powder, with respect to 100 parts by weight of soft magnetic alloy powder. Is 0.3 to 0.7 parts by weight. If the amount of the lubricant is too small, it is difficult to remove the mold after molding, and molding cracks tend to occur. On the other hand, when there is too much lubricant, the molding density is lowered and the magnetic permeability is reduced.

  In particular, when zinc stearate is used as a lubricant, the amount of zinc (Zn) contained in the obtained soft magnetic composition is in the range of 0.004 to 0.2% by mass. Is preferably adjusted. When there is too much content of Zn, there exists a tendency which sufficient intensity | strength as a magnetic core cannot be acquired.

The method for obtaining the mixture is not particularly limited, and can be obtained by mixing soft magnetic alloy powder, binder and organic solvent by a conventionally known method. In addition, you may add various additives as needed.
In mixing, for example, a mixer such as a pressure kneader, an attawriter, a vibration mill, a ball mill, or a V mixer, or a granulator such as a fluid granulator or a rolling granulator can be used.
Moreover, as temperature and time of a mixing process, Preferably it is about 1 to 30 minutes at room temperature.

Although it does not specifically limit as a method to obtain granulated powder, After drying a mixture by a conventionally well-known method, it obtains by crushing the dried mixture.
The temperature and time for the drying treatment are preferably about room temperature to 200 ° C. and 5 to 60 minutes.

  If necessary, a lubricant can be added to the granulated powder. After adding the lubricant to the granulated powder, it is desirable to mix for 5 to 60 minutes.

  The method for obtaining the molded body is not particularly limited, but a conventionally known method is used to form a mold having a cavity having a desired shape, and the mixture or granulated powder is filled into the cavity. The mixture is preferably compression-molded at a molding temperature and a predetermined molding pressure.

  The molding conditions in the compression molding are not particularly limited, and may be appropriately determined according to the shape and size of the soft magnetic alloy powder, the shape, size, and density of the dust core. For example, the maximum pressure is usually about 100 to 1000 MPa, preferably about 400 to 800 MPa, and the time for maintaining the maximum pressure is about 0.5 seconds to 1 minute.

  If the molding pressure is too low, it is difficult to achieve high density and high permeability by molding, and it is difficult to obtain sufficient mechanical strength. On the other hand, if the molding pressure at the time of molding is too high, the pressure application effect tends to saturate, the manufacturing cost tends to increase, and the productivity and economy may tend to be impaired, and the molding die deteriorates. It tends to be easy and the durability tends to decrease.

  The molding temperature is not particularly limited, but is usually preferably about room temperature to 200 ° C. In addition, the density of the compact tends to increase as the molding temperature at the time of molding increases, but if it is too high, the oxidation of the soft magnetic alloy particles is promoted, and the performance of the resulting dust core tends to deteriorate, In addition, the production cost may increase and productivity and economy may be impaired.

  The method of heat-treating the molded body obtained after molding may be carried out by a known method, and is not particularly limited. Generally, a molded body molded into an arbitrary shape by molding is subjected to a predetermined process using an annealing furnace. It is preferable to perform the heat treatment at a temperature.

  Although the processing temperature at the time of heat processing is not specifically limited, Usually, about 600-900 degreeC is preferable, More preferably, it is 700-850 degreeC. Even if the treatment temperature during heat treatment is too high or too low, sufficient strength as a magnetic core tends not to be obtained.

  The heat treatment step is preferably performed in an oxygen-containing atmosphere. Here, the oxygen-containing atmosphere is not particularly limited, and examples thereof include an air atmosphere (usually containing 20.95% oxygen) or a mixed atmosphere with an inert gas such as argon or nitrogen. It is done. Preferably, it is under atmospheric atmosphere. By performing heat treatment in an oxygen-containing atmosphere, a phase containing Si can be effectively formed at the grain boundary of the soft magnetic composition.

The dust core thus obtained preferably has a molding density of 5.50 g / cm ³ or more. A dust core that has been densified to a molding density of 5.50 g / cm ³ or more tends to be excellent in various performances such as high magnetic permeability, high strength, high core resistance, and low core loss.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to such embodiment at all, Of course, it can implement with a various aspect in the range which does not deviate from the summary of this invention. .

  For example, in the above-described embodiment, a magnetic core (powder magnetic core) is manufactured by compacting a mixture or granulated powder, but the magnetic core is formed by stacking the mixture into a sheet shape. It may be manufactured. In addition to dry molding, a molded body may be obtained by wet molding, extrusion molding, or the like.

  In the embodiment described above, a silicone resin is used as a binder in order to form a phase containing Si at the grain boundary of the soft magnetic composition, but silica gel or silica is used as an additive instead of the silicone resin. Si-containing components such as particles may be used.

  In addition, the molded body can be impregnated with a glass coat or a resin as necessary. Thereby, the intensity | strength of a magnetic core can further be improved.

  In the above-described embodiment, the magnetic core according to this embodiment is used as a coil-type electronic component. However, the magnetic core is not particularly limited, and various types such as a motor, a switching power supply, a DC-DC converter, a transformer, and a choke coil are used. It can also be suitably used as a magnetic core for electronic components. Especially, it is more suitable as a portable DC-DC converter.

  Furthermore, in the above-described embodiment, the magnetic core is composed of the soft magnetic composition according to the present invention. However, in addition to the magnetic core, an element body body of an electronic component and other molded bodies are included in the present invention. You may comprise with such a soft-magnetic-material composition.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Example 1
Sample 1 [Preparation of soft magnetic alloy powder]
First, ingots, chunks, or shots (particles) of simple Fe, simple Cr, and simple Si were prepared. Next, they were mixed so as to have a composition of 89.5 mass% Fe, 6.5 mass% Si, and 4.0 mass% Cr, and accommodated in a crucible disposed in a water atomizer. Next, using a work coil provided outside the crucible in an inert atmosphere, the crucible was heated to 1600 ° C. or higher by high frequency induction, and the ingot, chunk or shot in the crucible was melted and mixed to obtain a melt.

  Next, the melt in the crucible is ejected from a nozzle provided in the crucible, and at the same time, a high-pressure (50 MPa) water flow is collided with the melt and rapidly cooled, thereby soft magnets composed of Fe-Si-Cr-based particles. Alloy powder (average particle size: 50 μm) was prepared.

  As a result of analyzing the composition of the obtained soft magnetic alloy powder by fluorescent X-ray analysis, it was confirmed that it was consistent with the charged composition.

[Production of dust core]
6 parts by weight of a silicone resin (manufactured by Toray Dow Corning Silicon Co., Ltd .: SR2414LV) was added to 100 parts by weight of the obtained soft magnetic alloy powder, and these were mixed with a pressure kneader at room temperature for 30 minutes. The mixture was then dried in air at 150 ° C. for 20 minutes. To 100 parts by weight of the soft magnetic alloy powder, 0.5 parts by weight of zinc stearate (manufactured by Nitto Kasei: zinc stearate) as a lubricant was added to the dried magnetic powder and mixed for 10 minutes by a V mixer. .

  Then, the obtained mixture was shape | molded to the square sample of 5 mm x 5 mm x 10 mm, and the molded object was produced. The molding pressure was 600 MPa. The pressed body was heat-treated at 750 ° C. for 60 minutes in the atmosphere to cure the silicone resin and obtain a dust core.

[Various evaluations]
<Observation of grain boundaries>
First, the dust core was cut. The cut surface was observed with a scanning transmission electron microscope (STEM) to distinguish soft magnetic alloy particles from grain boundaries. In addition, Bi, V, and Si were confirmed to exist at grain boundaries by EDS analysis.

<3-point bending strength test (bending strength)>
A three-point bending strength test was performed on the dust core sample in accordance with JIS R1601.
The three-point bending strength is the maximum bending stress (kg / mm ² ) when a test piece is placed on two fulcrums arranged at a certain distance and bent by applying a load to one central point between the branches.

<Initial permeability (μi)>
A copper wire was wound around the dust core sample for 10 turns, and an initial magnetic permeability μi was measured using an LCR meter (Hewlett Packard 4284A). The measurement conditions were a measurement frequency of 1 MHz, a measurement temperature of 23 ° C., and a measurement level of 0.4 A / m.

Regarding Samples 2 to 7, Samples 2 to 7 are bismuth oxide so as to have the values shown in Table 1 in terms of Bi ₂ O ₃ with respect to 100 parts by weight of the soft magnetic alloy powder in the production of the dust core. A dust core sample was prepared in the same manner as Sample 1 except that was added, and the same evaluation was performed. Table 1 shows the results.

Sample 8 was prepared by adding vanadium oxide to 100 parts by weight of the soft magnetic alloy powder in addition to vanadium oxide so as to have the values shown in Table 1 in terms of V ₂ O _{5 in} the production of the dust core. A dust core sample was prepared by the same method as Sample 1, and the same evaluation was performed. Table 1 shows the results.

Sample 9 was prepared in the same manner as Sample 1 except that molybdenum oxide was added to 100 parts by weight of the soft magnetic alloy powder in addition to molybdenum oxide so as to obtain the values shown in Table 1 in terms of MoO _3. A dust core sample was prepared by the same method as described above, and the same evaluation was performed. Table 1 shows the results.

In addition, since the bending strength differs depending on the types of metals and binders constituting the magnetic core, 12 kg / mm ² or more is considered good in this example.

  As a result of STEM observation and EDS analysis, either Bi or V is present at the grain boundaries of Samples 2 to 8, and Bi and V are not present at the grain boundaries of Sample 1 and Sample 9. Was confirmed.

  As shown in Table 1, the strength of Sample 2 to Sample 8 in which at least one of Bi and V is present at the grain boundary is significantly improved as compared to Sample 1 and Sample 9 in which neither Bi or V is present. It was confirmed. The improvement rate (the improvement rate with respect to the sample 1) was confirmed to be about 5 to 10% at a high level.

(Example 2)
Samples 21 to 23 are samples 1, 5 and 8 except that non-silicone resin (manufactured by Nagase ChemteX Corp .: DENATEITE XNR 4338) was used as the binder resin. A dust core sample was prepared by the same method and evaluated in the same manner. The results are shown in Table 2.

In addition, since the bending strength differs depending on the types of metals and binders constituting the magnetic core, 10 kg / mm ² is considered good in this example.

  As a result of STEM observation and EDS analysis, it was confirmed that either Bi or V was present at the grain boundaries of Samples 22 and 23, and that Bi and V were not present at the grain boundaries of Sample 21. It was.

  As shown in Table 2, it is confirmed that the strength of the sample 22 and the sample 23 in which at least one of Bi and V is present at the grain boundary is significantly improved as compared with the sample 21 in which neither Bi nor V is present. It was done. In particular, it was confirmed that the improvement rate (the improvement rate with respect to the sample 21) was close to 20%.

Example 3
Samples 31 to 33 Samples 31 to 33 are soft magnetic alloy powders except that soft magnetic alloy powders composed of a composition of Fe 84.7% by mass, Si 9.7% by mass, and Al 5.6% by mass were used. Made a dust core sample by the same method as Sample 1, Sample 5 and Sample 8 of Example 1, and performed the same evaluation. Table 3 shows the results.

About Sample 34 to Sample 36 Sample 34 to Sample 36 are soft magnetic alloys composed of 49.2 mass% Fe, 44.0 mass% Ni, 2.3 mass% Si, and 4.5 mass% Co as soft magnetic alloy powder. A dust core sample was prepared in the same manner as Sample 1, Sample 5 and Sample 8 in Example 1 except that the alloy powder was used, and the same evaluation was performed. Table 3 shows the results.

In addition, since the bending strength differs depending on the type of metal and binder constituting the magnetic core, in this embodiment, the bending strength is the case of the magnetic core made of Fe-Si-Al soft magnetic alloy. Is 7.0 kg / mm ² or more, and in the case of a magnetic core made of a Fe—Ni—Si—Co based soft magnetic alloy, the bending strength is 11.0 kg / mm ² or more.

  As a result of STEM observation and EDS analysis, at least one of Bi and V is present at the grain boundaries of Sample 32, Sample 33, Sample 35, and Sample 36, and Bi and V are present at the grain boundaries of Sample 31 and Sample 34. None of these were confirmed.

  As shown in Table 3, in Sample 32, Sample 33, Sample 35, and Sample 36 in which at least one of Bi and V is present at the grain boundary, compared to Sample 31 and Sample 34 in which both Bi and V are not present, It was confirmed that the strength was greatly improved.

  From these results, according to the present invention, it was confirmed that the strength can be greatly improved even when the alloy type constituting the soft magnetic alloy composition is changed.

21, 22 ... Soft magnetic alloy particles 30, 31 ... Grain boundary 40 ... Bi and / or V region

Claims (5)

A soft magnetic composition having a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles,
The soft magnetic alloy particles are composed of Fe-Si-M soft magnetic alloy or Fe-Ni-Si-M soft magnetic alloy;
M is at least one selected from Cr, Al, Ti, Co and Ni;
A soft magnetic composition, wherein at least one of Bi and V is present in the grain boundary. The content of the Bi and / or V is, with respect to 100 wt% soft magnetic alloy, each in terms _{of Bi} 2 _{O 3} or terms _{of V} 2 _{O 5,} characterized in that 0.1 to 5.0 wt% The soft magnetic composition according to claim 1.   The soft magnetic composition according to claim 1, wherein Si further exists in the grain boundary.   A magnetic core comprising the soft magnetic composition according to claim 1.   A coil-type electronic component comprising the magnetic core according to claim 4.

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