JP6382487B2 - Magnetic core and coil type electronic components - Google Patents

Description

  The present invention relates to 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 compared to ferrite. As such a metal magnetic body, an Fe—Si—Al alloy, an Fe—Si—Cr alloy, or the like is known.

  Patent Document 1 proposes a coil-type electronic component that includes a magnetic material that has both high permeability and magnetic flux density at low cost.

  Examples of such coil-type electronic components include inductor components, EMC coil components, transformer components, and the like. Recently, as a magnetic core of these electronic components, Fe-Si-Al alloys and Fe-Si-Cr alloys are used. The metal magnetic material is becoming widely used.

  In particular, a metal magnetic material made of such an Fe-Si-Al alloy or Fe-Si-Cr alloy is used as a magnetic core of a miniaturized coil-type electronic component that can be surface-mounted on a circuit board. In some cases, high strength as a magnetic core is required.

JP 2011-249774 A

  This invention is made | formed in view of such a situation, and it aims at providing the magnetic core and coil type electronic component which have the outstanding intensity | strength.

In order to achieve the above object, the magnetic core according to the present invention comprises:
A core part composed of a soft magnetic composition, and a coating layer formed on at least a part of the surface of the core part,
The soft magnetic composition has a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles,
The soft magnetic alloy particles are Fe-Si-Al alloy particles or Fe-Si-Cr alloy particles,
A layer containing Si exists in the grain boundary.

  In the magnetic core according to the present invention, the soft magnetic composition constituting the core portion has a layer containing Si at the grain boundary of the soft magnetic alloy particles, and further, on at least a part of the surface of the core portion. By forming the coating layer, excellent strength as a magnetic core can be exhibited.

  Preferably, the Si-containing layer is a Si oxide layer or a Si complex oxide layer.

  Preferably, the Si-containing layer is further present on the surface of the soft magnetic alloy particle.

  Preferably, the Si-containing layer present on the surface of the soft magnetic alloy particles is a Si—Cr composite oxide layer.

  Furthermore, the coil 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 is suitable for a miniaturized coil-type electronic component that can be surface-mounted on a circuit board.

FIG. 1 is a schematic cross-sectional view of a magnetic core according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a barrel device used for manufacturing a magnetic core according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of the magnetic core after winding the coil. 4 is an enlarged cross-sectional view of a main part of the core portion shown in FIG. FIG. 5 is an enlarged cross-sectional view of a main part of the core portion showing observation points when performing EDS analysis. FIG. 6 shows the result of EDS analysis performed at the observation point shown in FIG. (A) is an analysis result of samples 1 and 2 according to an example of the present invention, and (b) is an analysis result of samples 3 and 4 according to a comparative example of the present invention. The vertical axis is the intensity ratio, and the horizontal axis is the depth.

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

Magnetic core The shape of the magnetic core according to the present invention is not only the drum type shown in FIG. 1, but also FT type, ET type, EI type, UU type, EE type, EER type, UI type, toroidal type, pot type, cup Examples include molds. In this embodiment, as shown in FIG. 1, the magnetic core 1 has a drum core shape, and has a configuration in which a coating layer 10 is formed on the entire surface of the core portion 2.

The core part core part 2 has a cylindrical or prismatic core part 4 and a pair of flange parts 5 integrally formed on both sides along the axial direction of the core part 4. The outer diameter of the flange portion 5 is larger than the outer diameter of the core portion 4, and a recess 6 surrounded by the flange portion 5 is formed on the outer periphery of the core portion 4. The coil 30 is formed by winding the wire 30 around the recess 6.

  Although the dimension of the core part 2 is not particularly limited, in the present embodiment, the outer diameter of the core part 4 is 0.6 to 1.2 mm, and the axial width of the core part 4 is 0.3 to 1. 0 mm, the outer diameter of the flange part 5 is 2.0 to 3.0 mm, the thickness of the flange part 5 is 0.2 to 0.3 mm, and the depth from the outer peripheral surface of the flange part 5 to the outer peripheral surface of the core part 4 The thickness is 0.5 to 1.0 mm. In addition, the shape of the collar part 5 may be a square, an octagon, etc. other than a circle.

  The core part 2 is comprised with the soft-magnetic-material composition which concerns on this embodiment.

The soft magnetic composition according to the present embodiment has a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles.
The soft magnetic alloy particles are Fe-Si-Al alloy particles or Fe-Si-Cr alloy particles,
A layer containing Si exists in the grain boundary.

  The soft magnetic composition according to the present embodiment can provide excellent magnetic properties by satisfying the above configuration, and has sufficient strength as a magnetic core even when molded with a relatively low molding pressure. Can be obtained. Moreover, since it can shape | mold by a comparatively low shaping | molding pressure in the case of pressure molding, the burden on a metal mold | die can be further reduced and productivity can be improved.

  As shown in FIG. 4, 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.

  The Si-containing layer according to this embodiment is present 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. Due to the presence of such a Si-containing layer, the magnetic core according to the present embodiment can obtain sufficient strength as a magnetic core even when formed with a relatively low molding pressure. Further, such a Si-containing layer serves as an insulator by being present at the grain boundary.

  The Si-containing layer according to this embodiment is preferably a Si oxide layer or a Si composite oxide layer.

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

  The Si oxide layer and the Si composite oxide layer according to the present embodiment are not particularly limited, and examples thereof include an amorphous layer containing Si, amorphous silicon, silica, and a Si—Cr composite oxide. .

  The Si-containing layer according to the present embodiment is preferably further present on the surface of the soft magnetic alloy particles. The Si-containing layer present on the surface of the soft magnetic alloy particles is preferably a Si—Cr composite oxide layer. The Si—Cr composite oxide layer is not particularly limited, and examples thereof include an amorphous layer containing Si and Cr.

  The layer containing Si 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 layer 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 layer 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. Moreover, the thickness of the layer containing Si may not be uniform, and the composition may not be uniform.

  The presence or absence and thickness of the Si-containing layer according to the present embodiment is controlled by the type and amount of the binder, other additive components, the heat treatment temperature and atmosphere of the molded body, etc. can do.

  In the present embodiment, the method for determining whether or not the Si-containing layer is present on the surface and grain boundary of the soft magnetic alloy particles is not particularly limited. For example, by analyzing a mapping image of Si. You may judge. A specific method is shown below.

  First, the magnetic core is observed using a scanning transmission electron microscope (STEM) to distinguish soft magnetic alloy particles from grain boundaries. 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.

  A mapping image can be created and observed for other elements such as Cr by the same method.

  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.

  The soft magnetic alloy particles according to the present embodiment are Fe—Si—Al alloy particles or Fe—Si—Cr alloy particles.

  When the soft magnetic alloy particles satisfy the above composition, the soft magnetic composition according to the present embodiment can obtain excellent magnetic characteristics, and even when it is molded at a relatively low molding pressure, A sufficient strength as a core can be obtained. Moreover, since it can shape | mold by a comparatively low shaping | molding pressure in the case of pressure molding, the burden on a metal mold | die can be further reduced and productivity can be improved. Further, when the soft magnetic alloy particles satisfy the above composition, a layer containing Si is easily formed at the interface 30.

  The composition of the Fe—Si—Al-based alloy particles is not particularly limited, but preferably 0.5 to 10.5 mass% of aluminum (Al) in terms of Al and silicon (Si) in terms of Si. It contains 4.5-14.5 mass%, and the remainder is composed of iron (Fe).

  The balance of the soft magnetic alloy particles may be composed only of iron (Fe).

  The composition of the Fe—Si—Cr alloy particles is not particularly limited, but preferably 1.5 to 8% by mass of chromium (Cr) in terms of Cr and silicon (Si) in terms of Si of 1. 4-9 mass% is contained, and the balance is composed of iron (Fe).

  The content of chromium (Cr) in the soft magnetic alloy particles is preferably 1.5 to 8% by mass, more preferably 3 to 7% by mass in terms of Cr. If the Cr content is too small, the strength and magnetic properties tend to decrease, and if it is too large, the strength tends to decrease.

  The content of silicon (Si) in the soft magnetic alloy particles is preferably 1.4 to 9% by mass, more preferably 4.5 to 8.5% by mass in terms of Si. If the Si content is too low or too high, the strength and magnetic properties tend to be reduced.

  The balance of the soft magnetic alloy particles may be composed only of iron (Fe).

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.

Moreover, although the thermal expansion coefficient of the core part 2 changes with compositions of a soft-magnetic-material composition, it is about 9 * 10 < ^-6 > / degreeC-10 * 10 < ^-6 > / degreeC in general.

The material of the coating layer coating layer 10 is not particularly limited as long as it has a thermal expansion coefficient that is equal to or lower than the thermal expansion coefficient of the core portion 2. For example, glass composition, SiO ₂ , B ₂ O ₃ , ZrO ₂ etc. are illustrated. The covering layer 10 may be composed of a plurality of materials, or may have a laminated structure composed of a plurality of layers.

  In this embodiment, it is preferable that the coating layer 10 is comprised from a glass composition. The glass composition is not particularly limited as long as it is formed in an amorphous state on the surface of the core portion 2 or formed as crystallized glass. For example, Si-B glass (borosilicate) Glass), alkali-free glass, lead-based glass and the like.

  The thermal expansion coefficient of the glass composition varies depending on the composition of components contained in the glass composition, the content of each component, and the like. Therefore, it is necessary to appropriately set the composition and content of the components so that the thermal expansion coefficient of the glass composition is equal to or less than the thermal expansion coefficient of the core portion 2.

  The coating layer 10 is not particularly limited as long as the coating layer 10 is coated to such an extent that an effect of improving power loss is obtained. The ratio (coverage) at which the coating layer is formed is preferably 50 to 100%, more preferably 90 to 100%. The higher the coverage, the greater the role as a protective layer for preventing the core portion 2 from being chipped.

  FIG. 1 shows a case where the coverage is 100%. Moreover, if the coating layer 10 is formed in the core portion 2 in the vicinity of a portion where the wire or the like is wound (in the present embodiment, the recess 6), a higher effect is easily obtained.

  The thickness of the coating layer 10 is not particularly limited as long as the effect of improving the power loss is obtained, but is preferably more than 0 μm and 50 μm or less, more preferably 5 μm or more and 25 μm or less. If the coating layer 10 is formed, the power loss is improved. However, if the coating layer is too thick, the contribution to the improvement effect of the power loss is small and the manufacturing cost increases, which is not preferable. Moreover, when the coating layer has a certain thickness, it can also serve as a protective layer for the core portion. Therefore, the thickness of the coating layer 10 is preferably within the above range.

  Furthermore, if the coating layer 10 has an insulating property, it is possible to ensure insulation from the wound wire even if the core portion 2 is conductive.

  Next, an example of a method for manufacturing a magnetic core in which the coating layer 10 is made of a glass composition will be described as the magnetic core according to the present embodiment.

The manufacturing method according to this embodiment is preferably
Mixing a soft magnetic alloy powder 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;
A step of curing the binder by heating the obtained molded body to obtain the core portion 2;
Forming a pre-firing coating layer on the obtained core 2;
And heat-treating the core portion 2 on which the pre-firing coating layer is formed to form the coating layer 10 to obtain a magnetic core.

  The magnetic core obtained by the manufacturing method according to the present embodiment is composed of the soft magnetic composition according to the present embodiment.

  As the soft magnetic alloy powder, Fe—Si—Al alloy particles or Fe—Si—Cr alloy particles 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.

  As the binding material, a material containing silicon resin is used. By using a silicon resin as the binder, a Si-containing layer is effectively formed at the grain boundary of the soft magnetic composition. A magnetic core composed of such a soft magnetic composition has sufficient strength even when molded with a relatively low molding pressure.

  In addition, the other binder may be contained in the range which does not prevent the effect of this invention. Examples of other binders include various organic polymer resins, phenol resins, epoxy resins, and water glass.

  As the binder, a silicon resin 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 mainly use a silicon resin as the binder. 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 amount of silicon resin added 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 silicon resin is too small, it becomes difficult to form a layer containing Si at the grain boundary of the soft magnetic composition, and the strength as a molded product tends to decrease.

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.

  In the manufacturing method according to the present embodiment, the molding pressure can be reduced to the maximum pressure because the binding material contains a silicon-based resin. Further, even when the molding pressure is reduced in this way, a layer containing Si is formed at the grain boundary of the soft magnetic composition constituting the magnetic core, so that the magnetic core has sufficient strength. It will have. As a result, manufacturing cost can be reduced, and productivity and economy can be improved.

  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. The density of the molded body 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 obtained magnetic core tends to deteriorate, Manufacturing costs 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 layer containing Si can be effectively formed at the grain boundary of the soft magnetic composition.

The core part 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.

  Next, with respect to the obtained core part 2, the coating layer 10a before heat processing comprised from a glass composition, binder resin, etc. is formed in the surface of the core part 2 using the barrel apparatus shown in FIG.

  The barrel apparatus 20 shown in FIG. 2 has a cylindrical or prismatic cylinder casing 20a, and a barrel container 22 is rotatable in the direction of arrow A (or the opposite direction) around its axis in the hollow interior. Is housed.

  An inlet pipe 23 and an outlet pipe 24 are formed in the casing 20a. The drying gas can enter the casing 20 a from the inlet pipe 23, and the air inside the casing can be discharged from the outlet pipe 24.

  A spray nozzle 25 is arranged along the axial direction at the axial center position in the barrel container 22, and the slurry 26 is directed from the nozzle 25 toward a number of core portions 2 stored in the barrel container 22. Can be sprayed. Since the barrel container 22 rotates in the direction of arrow A, the core portion 2 exists in the state shown in FIG. 2 and is agitated by the rotation of the barrel container 22.

  The nozzle 25 can spray the slurry 26 toward the assembly of the core portions 2. Note that the direction in which the slurry is sprayed from the nozzle 25 may be freely changed. Further, a discharge pipe (not shown) is connected to the casing 20a so that excess slurry 26 can be discharged.

  The wall of the barrel container 22 is formed with a large number of holes communicating with the outside and the inside, and the slurry 26 stored below the casing 20 a also enters the inside of the barrel container 22, and the slurry 26 The core part 2 can be immersed in Further, when the drying gas flows from the inlet pipe 23 through the casing 20 a to the outlet pipe 24, the drying gas also flows inside the barrel container 22.

  In order to form the coating layer 10a before the heat treatment, first, a large number of core portions 2 are accommodated in the barrel container 22 shown in FIG. Then, the barrel container 22 is rotated, and the slurry 26 is sprayed from the nozzle 25 while stirring the assembly of the core portions 2 to form the coating layer 10a before the heat treatment.

  The slurry 26 includes glass powder obtained by pulverizing the glass composition described above, a binder resin, and a solvent. Furthermore, other additives may be included. The glass composition may be made amorphous by mixing, melting, and rapidly cooling raw materials such as non-oxides such as oxides and halides constituting the composition. Moreover, you may use crystallized glass as a glass composition. In this embodiment, Si-B glass is used as the glass powder. The average particle diameter (median diameter) of the glass powder is not particularly limited, but is preferably in the range of 0.1 μm to 10 μm.

  The binder resin contained in the slurry 26 is preferably polyvinyl alcohol (PVA), a modified polyvinyl alcohol resin, or a mixture thereof. By doing in this way, the coating layer 10a before heat processing formed is excellent in adhesiveness with the core part 2. FIG.

  The solvent preferably contains water. The solvent may be water only, but when the contact angle between the surface of the glass powder and water is large, water-soluble alcohol such as ethanol, isopropyl alcohol (IPA), isobutyl alcohol (IBA), etc. is mixed at a certain ratio. It is preferable to suppress aggregation and sedimentation of the glass powder.

  The slurry 26 sprayed on the core part 2 covers the surface of each core part 2, and forms the coating layer 10a before baking. At this time, excess slurry 26 is discharged through a discharge pipe (not shown). Although the processing time which sprays the slurry 26 from the nozzle 25 is not specifically limited, For example, it is about 30 to 180 minutes. The temperature of the slurry 26 at the time of spraying is preferably 40 ° C. or more and 100 ° C. or less although it depends on the composition of the solvent. When using a solvent having a low boiling point, it is preferable to lower the temperature within the above temperature range.

  Next, while the slurry 26 is sprayed, the coating layer 10a before the heat treatment is simultaneously dried. In the drying process, a drying gas is poured into the casing 20 a from the inlet pipe 23 and discharged from the outlet pipe 24. The drying gas used for this drying treatment is, for example, air having a temperature of 50 to 100 ° C. After the spray treatment, a drying treatment may be further performed, for example, for 5 to 30 minutes.

  After the drying process, the core part 2 on which the coating layer 10a before the heat treatment is formed is taken out of the barrel container 22 and subjected to a heat softening process. The heat treatment conditions are determined according to the softening point of the glass powder contained in the coating layer 10a before the heat treatment. Specifically, the heat treatment temperature is preferably 600 to 800 ° C., and the heat treatment time is 5 to 120 minutes.

  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.

  After the heat treatment, a vitrified coating layer 10 is formed on the surface of the core portion 2, and the ferrite core 1 shown in FIG. 1 is obtained. In the present embodiment, vitrification is defined as a continuous amorphous solid film having a rigidity comparable to that of crystals.

  Thereafter, as shown in FIG. 3, a pair of terminal electrodes 32 made of silver, titanium, nickel, chromium, copper, or the like is printed, transferred, or immersed on the end face of one flange 5 in each core 2. It is formed by sputtering, plating or the like. The terminal electrode 32 is insulated because the covering layer 10 exists even if the core 2 is conductive.

  Thereafter, the wire 30 is wound around the core 4 and both ends of the wire are respectively connected to the terminal electrode 32 by thermocompression bonding, welding by ultrasonic waves or lasers, a soldering method, and the like. The coil component according to the form is completed.

  The magnetic core according to the present embodiment can exhibit excellent strength as a magnetic core. Moreover, especially a coating layer can be easily formed in the surface of a core part by comprising a coating layer with a glass composition. Moreover, the strength as a magnetic core can be improved by forming a coating layer made of a glass composition on the surface of the core. Further, when the glass composition is insulative, it is possible to ensure insulation with a wound wire or the like even if the core part is electrically conductive.

  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 silicon resin is used as a binder in order to form a layer containing Si at the grain boundary of the soft magnetic composition, but silica gel, silica particles, or the like can be used as an additive instead of the silicon resin. Si-containing components may be used.

  In the above-described embodiment, the coating layer before heat treatment is formed on the fired core portion, and this is heat-treated to form the coating layer. However, the firing of the core portion and the heat treatment of the coating layer are performed. You may do it at the same time. By doing so, the process can be simplified.

  The heat treatment conditions for simultaneously performing the firing of the core part and the heat treatment of the coating layer may be the same as the firing conditions of the core part alone or the same as the heat treatment conditions of the coating layer.

  In addition, the molded body can be impregnated with 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.

  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 88.5% by mass of Fe, 5% by mass of Cr and 6.5% by mass of Si, and accommodated in a crucible arranged 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 core part]
6 parts by weight of a silicon 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. 0.5 parts by weight of zinc stearate (manufactured by Nitto Kasei: zinc stearate) as a lubricant to 100 parts by weight of these soft magnetic alloy powders was added to the magnetic powder after drying, 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 in the atmosphere at 750 ° C. for 60 minutes to cure the silicone resin and obtain a magnetic core sample.

[Various evaluations]

<Confirmation of Si-containing layer at grain boundary>
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.
Next, as shown in FIG. 5, EDS analysis was performed at an arbitrarily selected observation point using an EDS apparatus attached to the STEM. The result of the EDS analysis is shown as a schematic diagram in FIG. In addition, the vertical axis | shaft of FIG. 6 is an intensity | strength ratio of the characteristic X-ray obtained by measurement.

<3-point bending strength test (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 fixed distance and bent by applying a load to one central point between the fulcrums.
Furthermore, from the result of the obtained maximum bending stress, the improvement rate of the strength by forming the coating layer was calculated by the following formula.
Strength improvement rate (%)
= 100 × (sample with coating layer−sample without coating layer) / (sample without coating layer)
In this example, an improvement rate of 24% or more was considered good. The results are shown in Table 1.

Sample 2 For sample 2, a magnetic core sample was prepared in the same manner as for sample 1 except that a coating layer before heat treatment was formed on the molded body obtained in the same manner as for sample 1 by the following method. Was evaluated. The results are shown in Table 1 and FIG.

  First, a glass composition powder for forming a coating layer was prepared. Si-B glass was used as the glass composition. The Si-B glass was prepared by mixing and melting raw materials such as oxides constituting the glass component and then rapidly cooling.

The thermal expansion coefficient of the Si—B glass composition used as the coating layer was 6 × 10 ⁻⁶ / ° C. The thermal expansion coefficient of the core part and the glass composition was measured by TMA.

  Next, a slurry used to form a coating layer was prepared. First, the obtained glass composition powder and PVA were mixed at a predetermined weight ratio. Furthermore, the obtained solid component (a mixture of glass powder and PVA) and a solvent were mixed at a predetermined weight ratio, and mixed by a ball mill to prepare a slurry. As the solvent, a mixture of water and ethanol at 8: 2 was used. The content of the binder resin with respect to the glass powder in the slurry was 10% by weight.

  Next, the compact was put into a barrel container of a barrel device, and a coating layer before heat treatment was formed on the entire surface of the compact by spraying using the slurry described above. At the same time as the spraying, drying was performed at a hot air temperature of 70 ° C.

  Thereafter, the molded body on which the coating layer before the heat treatment is formed is taken out from the barrel container, and the molded body is heat-treated at 750 ° C. for 1 hour to form a vitrified coating layer on the entire surface of the molded body. A wick sample was obtained.

  The thickness of the coating layer was about 3 to 25 μm. The thickness of the coating layer was calculated from the dimensions before and after the coating layer was formed.

  Moreover, the coverage was about 98 to 100%. The covering rate was calculated by observing 20 samples visually and measuring the covering area of the sample in which the formation of the coating layer was incomplete.

About sample 3, sample 3 is a non-silicone resin (Nagase ChemteX Corporation manufactured: DENATEITE XNR 4338) as a binder resin, and a magnetic core sample is prepared in the same manner as sample 1, Similar evaluations were made. The results are shown in Table 1 and FIG.
Sample 4 Sample 4 is a non-silicone resin (Nagase Chemtex Co., Ltd .: DENATEITE XNR 4338) as a binder resin, and a magnetic core sample is prepared in the same manner as Sample 2, Similar evaluations were made. The results are shown in Table 1 and FIG.

  In Samples 1 and 2, as a result of STEM observation and EDS analysis, it was confirmed that a layer containing Si was formed at the grain boundary of the soft magnetic composition constituting the core portion.

  The major difference between Samples 1 and 2 is whether or not a coating layer made of glass is formed on the surface of the core portion. In Sample 2 where the coating layer is formed, the coating layer is formed. It was confirmed that the improvement rate of strength exceeded 24% compared to the sample 1 that was not.

  On the other hand, as a result of STEM observation and EDS analysis, the samples 3 and 4 in which the Si-containing layer is not formed at the grain boundary of the soft magnetic material composition constituting the core part are stronger than the samples 1 and 2. Was confirmed to be low.

  Furthermore, even when the coating layer was formed on the surface of the core part (sample 4), the rapid strength improvement as in sample 2 was not confirmed.

  From these results, in the magnetic core according to the present invention, the strength when the coating layer is formed on the surface of the core portion due to the presence of the Si-containing layer at the grain boundary of the soft magnetic composition constituting the core portion. It was confirmed that the improvement rate of was increased.

  In particular, as a result of EDS analysis, in Samples 1 and 2, an amorphous layer containing Si at the grain boundary of the soft magnetic composition was confirmed. Further, an amorphous layer containing Si and Cr was confirmed on the particle surface (see FIG. 6A). On the other hand, in Samples 3 and 4, a layer containing Si at the grain boundary of the soft magnetic composition was not observed (see FIG. 6B). Such a difference is considered to affect the difference in strength improvement rate when the coating layer is formed on the surface of the core portion.

  The thickness of the layer containing Si at the observation points of Samples 1 and 2 was about 0.1 μm.

(Example 2)
Samples 5 to 8 Sample 5 was the same as Sample 1 except that soft magnetic alloy powder composed of a composition of Fe 85% by mass, Al 5.5% by mass and Si 9.5% by mass was used as the soft magnetic alloy powder. A magnetic core sample was prepared by the same method and evaluated in the same manner. Table 1 shows the results.

  Sample 6 was prepared in the same manner as Sample 2 except that soft magnetic alloy powder composed of Fe 85% by mass, Al 5.5% by mass and Si 9.5% by mass was used. Samples were prepared and evaluated in the same manner. Table 1 shows the results.

  Sample 7 was prepared in the same manner as Sample 3 except that the soft magnetic alloy powder was composed of a composition of 85 mass% Fe, 5.5 mass% Al, and 9.5 mass% Si. A core sample was prepared and evaluated in the same manner. Table 1 shows the results.

  Sample 8 was prepared in the same manner as Sample 4 except that soft magnetic alloy powder composed of 85 mass% Fe, 5.5 mass% Al, and 9.5 mass% Si was used as the soft magnetic alloy powder. A core sample was prepared and evaluated in the same manner. Table 1 shows the results.

  As shown in Table 1, in Samples 5 and 6, it was confirmed that a layer containing Si was formed at the grain boundary. Therefore, in Sample 6 in which the coating layer was formed on the surface of the core part, an improvement in strength exceeding 24% was confirmed compared to Sample 5 in which the coating layer was not formed.

  On the other hand, in Samples 7 and 8, the layer containing Si is not formed at the grain boundary, and even when the coating layer is formed on the surface of the core part (Sample 8), No significant improvement in strength was confirmed.

  The magnetic core according to the present invention has a core portion made of a soft magnetic composition having a layer containing Si at the grain boundary, and a coating layer is formed on the surface of the core portion. Demonstrate. In particular, when the core part is a green compact, a magnetic core having sufficient strength can be obtained even at a relatively low molding pressure, so that deterioration of the mold can be reduced and production can be achieved. It is possible to improve the performance. As a result, the manufacturing cost of the coil-type electronic component can be reduced by using the magnetic core manufactured in this way.

DESCRIPTION OF SYMBOLS 1 ... Magnetic core 2 ... Core part 10 ... Coating layer 10a ... Coating layer 20 before heat processing ... Barrel apparatus 21, 22 ... Soft magnetic alloy particle 30, 31 ... Grain boundary

Claims (2)

A magnetic core having a core part made of a soft magnetic composition, and a coating layer formed on at least a part of the surface of the core part,
The coating layer is composed of a glass composition having a thermal expansion coefficient that is equal to or lower than the thermal expansion coefficient of the core part,
The soft magnetic composition has a plurality of soft magnetic alloy particles and a grain boundary existing between the soft magnetic alloy particles,
The soft magnetic alloy particles are Fe-Si-Cr alloy particles,
The grain boundary and the surface of the soft magnetic alloy particles have a layer containing Si,
The Si-containing layer present at the grain boundary is a Si oxide layer or a Si composite oxide layer,
Layer containing the Si existing on the surface of the soft magnetic alloy particles, Ri Si-Cr composite oxide layer der,
The magnetic core according to claim 1, wherein a region having a higher Si concentration than the Si concentration in the Si—Cr composite oxide layer exists at the grain boundary . A coil-type electronic component comprising the magnetic core according to claim 1 .

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