JP2018137349A - Magnetic core and coil component - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic core which allows a high initial effective magnetic permeability and a small magnetic core loss to be achieved, and which is superior in DC superposing characteristics, and a coil component with the magnetic core.SOLUTION: A magnetic core comprises Fe-based soft magnetic alloy particles which bind to each other through a layer of oxide of an element making a constituent of the alloy. The magnetic core is magnetically excited by an AC current with a DC current superposed thereon. The magnetic core is superior in DC superposing characteristics; the space factor is over 85%, the initial value of an effective magnetic permeability μe at a frequency of 100 kHz is 34 or more; the DC magnetic field Hsat is 5.6 kA/m or more when the effective magnetic permeability μe is 80% of the initial value, and the magnetic flux density Bsat on an initial magnetization curve at the DC magnetic field Hsat is 400 mT or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic core having a structure mainly composed of Fe-based soft magnetic alloy particles, and a coil component using the same.

  Conventionally, coil parts such as inductors, transformers, chokes, and motors have been used in various applications such as home appliances, industrial equipment, and vehicles. A general coil component is often composed of a magnetic core (magnetic core) and a coil wound around the magnetic core. For such a magnetic core, ferrite having excellent magnetic properties, flexibility in shape, and cost is widely used.

In recent years, as power supply devices such as electronic devices have been downsized, the demand for coil parts that are small and low in profile and can be used for large currents has become stronger, and the saturation magnetic flux density is higher than that of ferrite. Adoption of magnetic cores using metallic magnetic powder is progressing.
As the metal-based magnetic powder, Fe-based soft magnetic alloy powders such as Fe-Si, Fe-Ni, Fe-Si-Cr, and Fe-Si-Al are used, for example. The magnetic core obtained from a compact of the Fe-based soft magnetic alloy powder has a high saturation magnetic flux density, but has a low electrical resistivity because it is an alloy powder, and magnetic alloy powder using water glass or thermosetting resin in advance. Are often covered with insulation.

  On the other hand, in Patent Document 1, after forming Fe-based soft magnetic alloy powder containing Al and Cr together with Fe, heat treatment is performed in an atmosphere containing oxygen, and the surface of the alloy particles is oxidized by oxidation of the particles. There has also been proposed a technique for forming an obtained oxide layer, bonding particles of a soft magnetic alloy through the oxide layer, and providing insulation to the magnetic core.

International Publication No. 2014/1122483

  By the way, the magnetic core used for the coil component has a small magnetic core loss, a large magnetic permeability, and excellent superposition characteristics, i.e., the inductance of the magnetic core excited by the alternating current superimposed with the direct current has an initial value up to a high current value. It is required to maintain and suppress the decrease.

  In a magnetic core using Fe-based soft magnetic alloy particles, the space density between the particles is increased by increasing the density of the compact to increase the space factor of the magnetic core, increasing the initial effective magnetic permeability described later, and the magnetic core. Loss can be reduced. However, on the other hand, there is a problem that the direct current superimposition characteristics deteriorate and the maximum current value that can be used as a coil component is reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic core having high initial effective magnetic permeability and small magnetic core loss and excellent in DC superposition characteristics and a coil component using the same. To do.

  The first invention is a magnetic core in which particles of an Fe-based soft magnetic alloy are bonded via an oxide layer of an element constituting the alloy, and is excited by an alternating current on which a direct current is superimposed, and has a space factor of 85. %, The initial value of the effective permeability μe at a frequency of 100 kHz is 34 or more, the DC magnetic field Hsat at which the effective permeability μe is 80% of the initial value is 5.6 kA / m or more, and A magnetic core excellent in DC superposition characteristics in which the magnetic flux density Bsat on the initial magnetization curve in the DC magnetic field Hsat is 400 mT or more.

  In the present invention, it is preferable that the Fe-based soft magnetic alloy contains Fe as a main component and an element M (M is at least one of Si, Cr, and Al) that is more easily oxidized than Fe.

  In the present invention, the Fe-based soft magnetic alloy is represented by the composition formula: aFebAlcCrdSi, and by mass%, a + b + c + d = 100, 75 ≦ a <100, 0 ≦ b <13.8, 0 ≦ c ≦ 7, 0 It is preferable that ≦ d ≦ 5.

  2nd invention is a coil component provided with the magnetic core of 1st invention, and the coil wound around the said magnetic core.

    According to the present invention, a high initial effective magnetic permeability and a small core loss can be obtained, and a magnetic core excellent in DC superposition characteristics and a coil component using the same can be provided.

It is a graph which shows the direct current superimposition characteristic of the coil components using the magnetic core containing one Embodiment of this invention. It is a figure for demonstrating the direct-current magnetic field Hsat from which the effective magnetic permeability microe becomes 80% with respect to an initial value. It is a figure for demonstrating the magnetic flux density Bsat calculated | required on the initial magnetization curve in DC magnetic field Hsat. It is a graph which shows the relationship between DC magnetic field Hsat of a magnetic core containing one Embodiment of this invention, and magnetic flux density Bsat.

  Hereinafter, a magnetic core according to an embodiment of the present invention and a coil component using the magnetic core will be specifically described. However, the present invention is not limited to this.

  The magnetic core according to the present invention is a magnetic core in which particles of an Fe-based soft magnetic alloy are bonded through an oxide layer of an element constituting the alloy. That is, the Fe-based soft magnetic alloy particles have a structure connected through grain boundaries, and an oxide layer derived from the alloy is formed at the grain boundaries connecting adjacent Fe-based soft magnetic alloy particles. Yes.

In the present invention, the elements constituting the Fe-based soft magnetic alloy together with Fe can be appropriately selected according to the required magnetic properties and the ability to form an oxide layer. However, the elements M (M is Si, Cr , At least one of Al), FeSi alloy, FeSiCr alloy, FeSiAl alloy, FeAlCr alloy, and FeAlCrSi alloy are preferable. Nonferrous metals Si, Al, and Cr have a greater affinity with O than Fe. Therefore, when the Fe-based soft magnetic alloy particles are oxidized at a high temperature in an atmosphere containing oxygen or an atmosphere containing water vapor, oxides of these non-ferrous metals having a high affinity for O are formed on the surface. The oxide layer is grown by reacting Fe-based soft magnetic alloy particles and oxygen by heat treatment, and is formed by an oxidation reaction exceeding the natural oxidation of Fe-based soft magnetic alloy particles. The oxide layer may contain hematite (Fe ₂ O ₃ ), wustite (FeO), or magnetite (Fe ₃ O ₄ ).

  When the particles of Fe-based soft magnetic alloy before high-temperature oxidation are formed into a predetermined shape and the formed body is annealed at a predetermined temperature in a predetermined atmosphere, oxidation of these non-ferrous metals and Fe having a large affinity for O An object is formed to cover the surface of the Fe-based soft magnetic alloy particles, and further, the voids between the particles are filled. The formed oxide layer forms a grain boundary and bonds the alloy particles.

  Alternatively, Fe-based soft magnetic alloy particles having an oxide layer formed on the surface thereof may be formed into a predetermined shape and heat-treated in a reducing atmosphere at a temperature at which the oxide layer is sintered. In this case as well, the oxide layer forms a grain boundary and bonds the alloy particles.

Among the elements M, Al has a higher affinity with O than other non-ferrous metals, and Al ₂ O ₃ which is chemically stable by high-temperature oxidation or composite oxides with other non-ferrous metals are used as alloy particles. Form on the surface. Since the oxide containing Al is excellent in corrosion resistance and stability, the formation of an Al oxide layer on the surface of the Fe-based soft magnetic alloy particles increases the insulation between the particles and reduces the eddy current loss of the magnetic core. Can be reduced. It also reduces the magnetocrystalline anisotropy and improves the core loss.

Cr has the highest affinity with O next to Al, and combines with oxygen in the same manner as Al to produce chemically stable Cr ₂ O ₃ and composite oxides with other non-ferrous metals. Since the oxide containing Cr is also excellent in corrosion resistance and stability, it is possible to increase the insulation between the particles and reduce the eddy current loss of the magnetic core.

Si forms chemically stable SiO ₂ and composite oxides with other non-ferrous metals on the surface of the alloy particles. SiO ₂ can also increase the insulation between the particles and reduce the eddy current loss of the magnetic core. It also has the effect of increasing the magnetic permeability. Further, when a large amount of Si is contained, the particles become hard.

  In consideration of the influence of the element M on the oxide forming ability and the magnetic characteristics, the Fe-based soft magnetic alloy is represented by a composition formula: aFebAlcCrdSi, contains at least one of Si, Cr, and Al, and is expressed in mass% as a + b + c + d = Preferably, 100, 75 ≦ a <100, 0 ≦ b <13.8, 0 ≦ c ≦ 10, 0 ≦ d ≦ 5. More preferably, in the composition formula, a + b + c + d = 100, 4 ≦ b <13.8, 3 ≦ c ≦ 7, and 0 ≦ d ≦ 1. When Cr is included together with Al, Cr also functions to assist the oxidation of Al, and in the heat treatment, the Fe-based soft magnetic alloy particles are combined through an oxide layer enriched in Al. To help.

  As inevitable impurities, for example, Mn ≦ 1 mass%, C ≦ 0.05 mass%, Ni ≦ 0.5 mass%, N ≦ 0.1 mass%, P ≦ 0.02 mass%, S ≦ 0.02 It may be contained in mass%. Further, the smaller the amount of O contained in the alloy, the better and it is preferable that O ≦ 0.5% by mass. Any composition amount is a value of the outer number when the main component is 100 mass%.

  The oxide layer can be easily confirmed by observing the cross-section of the magnetic core using a scanning electron microscope (SEM / EDX: Scanning Electron Microscope / energy dispersive X-ray spectroscopy) and examining the distribution of each constituent element. I can do it. When an oxide layer formed as a grain boundary between two particles is observed using a transmission electron microscope (TEM), it can be confirmed to have a thickness of, for example, 10 nm to 200 nm.

Although the average particle diameter of the alloy particles (here, the median diameter d50 in the cumulative particle size distribution is used) is not particularly limited, the strength of the magnetic core and high frequency characteristics are improved by reducing the average particle diameter. For example, in applications where high frequency characteristics are required, particles having an average particle size of 20 μm or less can be suitably used. The median diameter d50 is more preferably 18 μm or less, and further preferably 16 μm or less. On the other hand, when the average particle size is small, the specific surface area is large and oxidation is easy, so the median diameter d50 is more preferably 3 μm or more. It is more preferable to remove coarse particles from the particles using a sieve or the like. In this case, it is preferable to use alloy particles that are at least under 32 μm (that is, passed through a sieve having an opening of 32 μm).
The form of the Fe-based soft magnetic alloy particles is not particularly limited, but it is preferable to use a granular powder represented by atomized powder as a raw material powder from the viewpoint of fluidity and the like. Atomization methods such as gas atomization and water atomization are suitable for producing powders of alloys that have high malleability and ductility and are difficult to grind. The atomization method is also suitable for obtaining a substantially spherical soft magnetic alloy powder.

Hereinafter, a manufacturing method employing pressure molding will be described as an example of a method for manufacturing a magnetic core.
When forming the Fe-based soft magnetic alloy particles, it is preferable to add a binder in order to bind the particles and give the molded body strength to withstand handling after forming. Although the kind of binder is not specifically limited, For example, various organic binders, such as polyethylene, polyvinyl alcohol, an acrylic resin, can be used. The organic binder is thermally decomposed by heat treatment after molding. An inorganic binder such as a silicone resin that solidifies and remains after the heat treatment or binds the powder together with the oxide of the M element of the alloy as a Si oxide may be used in combination.

  The amount of the binder added may be an amount that can sufficiently reach between the particles of the alloy or ensure a sufficient compact strength. On the other hand, if the amount is too large, the density and strength are lowered. From this viewpoint, the amount of binder added is preferably 0.8 to 3.0 parts by mass with respect to 100 parts by mass of alloy particles having an average particle diameter (d50) of 10 μm, for example.

  The mixing method of the alloy particles and the binder is not particularly limited, and conventionally known mixing methods and mixers can be used. In a state where the binder is mixed, the mixed powder is an agglomerated powder having a wide particle size distribution due to its binding action. By passing the mixed powder through a sieve using, for example, a vibration sieve or the like, a granulated powder having a desired secondary particle size suitable for molding can be obtained. Further, in order to reduce the friction between the powder and the mold during pressure molding, it is preferable to add a lubricant such as stearic acid or stearate. The addition amount of the lubricant is preferably 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the alloy particles. The lubricant can be applied to the mold. The total amount of lubricant and binder added is preferably 3.5 parts by mass or less.

  Next, the obtained mixed powder is pressure-molded to obtain a molded body. The mixed powder obtained by the above procedure is preferably granulated as described above and subjected to a pressure forming step. The granulated mixed powder is pressure-molded into various shapes such as a toroidal shape, a rectangular parallelepiped shape, a cylindrical shape, a drum shape, and a push pin shape using a molding die. The pressure molding may be room temperature molding or warm molding performed by heating to such an extent that the binder does not disappear. The molding pressure during pressure molding is preferably 0.8 GPa or more. As the molding pressure at the time of pressure molding becomes higher, the mold is more likely to be damaged. Therefore, it is preferable to suppress the molding pressure to 1.8 GPa or less. In addition, the molding method is not limited to the above-described pressure molding, and may be a method of stacking and heating and pressure-bonding sheet-like molded bodies obtained by a known sheet molding method such as a doctor blade method, As a method for preparing the mixed powder, a known method can be adopted depending on the molding method.

  Next, a heat treatment process for heat-treating the molded body obtained through the molding process will be described. In order to form an alloy-derived oxide layer between the alloy particles, the molded body is subjected to heat treatment (high temperature oxidation). Such heat treatment can further alleviate stress strain introduced by molding or the like. This oxide layer is grown by a reaction between alloy particles and oxygen (O) by heat treatment, and is formed by an oxidation reaction exceeding the natural oxidation of the alloy. Such heat treatment can be performed in an atmosphere in which oxygen exists, such as in the air or in a mixed gas of oxygen and an inert gas. Further, the heat treatment can be performed in an atmosphere in which water vapor exists, such as in a mixed gas of water vapor and inert gas. Of these, heat treatment in the air is simple and preferable.

  The heat treatment in this step may be performed at a temperature at which the oxide layer or the like is formed. Although depending on the alloy composition, at temperatures exceeding 850 ° C., the alloy particles begin to sinter and the magnetic core loss also increases. In addition, since the oxide layer formed by heat treatment is also affected by the heat treatment temperature, the specific heat treatment temperature is preferably in the range of 650 to 850 ° C. The holding time in the above temperature range is appropriately set according to the size of the magnetic core, the processing amount, the allowable range of characteristic variation, and the like, and is set to 0.5 to 3 hours, for example.

  The space factor in the heat-treated magnetic core is preferably more than 85%. As a result, the space factor can be increased and the magnetic characteristics can be improved while suppressing the equipment and cost load.

The alloy composition, manufacturing conditions, or alloy particle size is selected, Fe-based soft magnetic alloy particles are bonded through an oxide layer, the space factor is greater than 85%, and the effective permeability μe at a frequency of 100 kHz is When the initial value (DC magnetic field 0.4 A / m) is 34 or more and the effective magnetic permeability μe is 80% of the initial value, the DC magnetic field Hsat is 5.6 kA / m or more, and the initial magnetization in the DC magnetic field Hsat It is assumed that the magnetic flux density Bsat on the curve is 400 mT or more. A coil component in which a coil is provided on such a magnetic core has excellent direct current superposition characteristics.

  A DC magnetic field Hsat having an effective permeability μe of 80% with respect to the initial value will be described with reference to FIG. In FIG. 2, μe80 is a value at a point where the effective permeability μe of a magnetic core excited by an alternating current superimposed with a direct current is 80% with respect to its initial value, and a direct current magnetic field Hsat is a value of the direct current magnetic field at that point. Represents. In evaluating the superimposition characteristics, it is important to reduce the effective permeability μe with respect to the DC magnetic field to be superimposed. In general, a DC magnetic field Hsat having an effective magnetic permeability μe of 70 to 80% with respect to its initial value may be evaluated as a threshold value for determining that it can be used as a coil component. In the present invention, the effective magnetic permeability μe is an initial value. A direct current magnetic field that drops to 80% of the value was used as a threshold value. Here, the initial value of the effective permeability μe is a value in a DC magnetic field in which the DC magnetic field is sufficiently smaller than the DC magnetic field Hsat, and the change in the effective permeability μe does not substantially occur as the DC magnetic field increases. Any value in a DC magnetic field may be used. In the present invention, the case where the DC magnetic field is 0.4 A / m is set as the initial value of the effective permeability μe. When the magnetic cores have the same shape, it is preferable that the DC current Hsat that is μe80 is large because the maximum current that can be passed through the coil component is large. Furthermore, it is preferable that the initial value of the effective magnetic permeability μe is larger because the number of windings is reduced and the shape of the magnetic core can be reduced.

Next, the magnetic flux density Bsat on the initial magnetization curve in the DC magnetic field Hsat will be described with reference to FIG.
In the major loop of the initial magnetization curve from the initial magnetization state of the magnetic core to the saturation magnetization, the magnetic flux density corresponding to the DC magnetic field Hsat is defined as Bsat.

  The magnetic core is manufactured in the form of a single magnetic core obtained by press-molding only a soft magnetic alloy powder mixed with a binder or the like as described above, and may be wound as a coil component, or a coil is disposed inside. It is good also as a coil component manufactured with a form. The latter configuration is not particularly limited. For example, a magnetic core of a coil encapsulating structure using a method in which soft magnetic alloy powder and a coil are integrally formed by pressure, or a lamination process such as a sheet lamination method or a printing method is used. It can be manufactured in the form. A coil component having a magnetic core and a coil is used as, for example, a choke, an inductor, a reactor, a transformer, or the like.

  Hereinafter, preferred embodiments of the present invention will be described in detail by way of example. In the description, an FeAlCr alloy is used as the Fe-based soft magnetic alloy. However, the materials, blending amounts, and the like described in this example are not intended to limit the scope of the present invention only to those unless otherwise specified.

(1) Preparation of raw material powder A raw material powder of 5 mass% Al, 4 mass% Cr, and the balance substantially Fe was prepared by an atomization method.

  The average particle diameter (median diameter d50) of the raw material powder was obtained using a laser diffraction / scattering particle size distribution analyzer (LA-920, manufactured by Horiba, Ltd.). Saturation magnetization Ms, coercive force Hc, and saturation magnetic flux density Bs of each obtained raw material powder were obtained by a VSM magnetic property measuring apparatus (VSM-5-20 manufactured by Toei Industry Co., Ltd.). As a result, the saturation magnetization Ms was 180 emu / g, and the coercive force Hc was 1200 A / m.

(2) Production of magnetic core A magnetic core was produced as follows. First, the raw material powder was further classified with a sieve to prepare two raw material powders having different average particle diameters d50. For each raw material powder, PVA (Poval PVA-205 manufactured by Kuraray Co., Ltd .; solid content: 10%) was used as a binder, ion-exchanged water was added as a solvent, and the mixture was stirred and mixed to form a slurry. The slurry concentration is 80% by mass. The amount of binder added was changed to 0.75 to 1.66 parts by weight with respect to 100 parts by weight of the raw material powder. It was dried at 120 ° C. for 10 hours, and the dried mixed powder was passed through a sieve to obtain granulated powder having different average particle diameter and binder amount. To this granulated powder, zinc stearate was added and mixed at a ratio of 0.4 parts by weight with respect to 100 parts by weight of the raw material powder.

The obtained granulated powder was subjected to pressure molding at room temperature using a press machine to obtain molded bodies having a toroidal (annular) shape and a disk shape. The pressure during molding was 490 MPa (5 ton / cm ² ) to 1453 MPa (14.8 ton / cm ² ). This molded body was put into a heat treatment furnace, subjected to heat treatment by holding it in the atmosphere at a heat treatment temperature of 740 ° C. for 2 minutes. 1 to 9 magnetic cores were obtained. The outer dimensions of the magnetic core were an outer diameter of 13.4 mm, an inner diameter of 7.7 mm, a height of 2.0 mm, an outer diameter of 13.5 mm, and a height of 2.0 mm.

(3) Evaluation method and result The following AG was evaluated about the magnetic core produced by the above process. The evaluation results are shown in Table 1. In Table 1, Sample No. Are distinguished by adding *. FIG. 4 is a graph showing the relationship between the DC magnetic field Hsat including the magnetic core of the present invention and the magnetic flux density Bsat.

A. Space factor Pf (relative density)
The density (kg / m ³ ) was calculated from the dimensions and mass of the annular magnetic core by the volume weight method, and was defined as the density ds. The density ds was divided by the true density of the Fe-based soft magnetic alloy to calculate the space factor (relative density) [%] of the magnetic core.

B. Specific resistance ρv
A disk-shaped magnetic core is used as an object to be measured, and a conductive adhesive is applied to two opposing flat surfaces, dried and solidified, and then the object to be measured is set between the electrodes. A resistance value R (Ω) is measured by applying a DC voltage of 100 V using an electrical resistance measuring device (5451 manufactured by ADC Corporation). The planar area A (m2) and thickness t (m) of the object to be measured were measured, and the specific resistance ρv (Ωm) was calculated by the following equation.
Specific resistance ρv (Ωm) = R × (A / t)

C. Magnetic core loss Pcv
The magnetic core of the annular body is the object to be measured, and the primary side winding and the secondary side winding are wound by 15 turns, respectively, and the maximum magnetic flux density is 30 mT and the frequency is 300 kHz by BH analyzer SY-8218 manufactured by Iwatatsu Measurement Co., Ltd. Under these conditions, the core loss Pcv (kW / m ³ ) was measured at room temperature.

D. Effective permeability μe
Using the magnetic core of the annular body as the object to be measured, the conducting wire was wound for 30 turns, and the inductance was measured at room temperature using a LCR meter (Agilent Technology Co., Ltd., 4284A) at a frequency of 100 kHz. The value obtained under the condition that the DC magnetic field was 0.4 A / m was used as the initial value of the effective permeability μe.
Initial permeability μe = (le × L) / (μ ₀ × Ae × N ² )
(Le: magnetic path length, L: sample inductance (H), μ ₀ : vacuum permeability = 4π × 10 ⁻⁷ (H / m), Ae: cross-sectional area of magnetic core, N: number of turns of coil)

E. DC superimposition characteristics An annular magnetic core is the object to be measured, and a conducting wire is wound 30 turns to form a coil component, and a DC magnetic field is applied in steps of 1 kA / m up to 20 kA / m with a DC application device (42841A: manufactured by Hewlett Packard). In this state, the inductance L was measured at room temperature with a frequency of 100 kHz using an LCR meter (4284A manufactured by Agilent Technologies). A DC superposition characteristic was obtained from the effective permeability μe in a DC magnetic field obtained from the obtained inductance.

  The above-mentioned FIG. * 2 shows the DC superimposition characteristics, and the DC superimposition characteristics were similarly obtained for each sample. Μe80 was calculated from the initial value of the effective permeability μe of each sample, and a DC magnetic field Hsat at which the effective permeability μe decreased from the initial value to 80% was determined from the DC superposition characteristics. Specifically, it can be calculated by primary approximation from the relationship between the DC magnetic field and μe in the measurement steps before and after μe80.

F. Initial magnetization curve The magnetic core of the demagnetized annular body is the object to be measured, the primary winding is wound 30 turns, the secondary winding is wound 10 turns, and the applied magnetic field is measured by a DCT magnetic property test apparatus (SK110) manufactured by Metron Engineering Co., Ltd. The initial magnetization curve was measured at room temperature under the condition of 10 kA / m. The number of turns can be appropriately increased or decreased depending on the permeability and dimensions of the toroidal core.

  The above-mentioned FIG. * 2 shows the initial magnetization curve, and the initial magnetization curve was similarly obtained for each sample. The magnetic flux density Bsat corresponding to the DC magnetic field Hsat of each sample was obtained from the initial magnetization curve. Specifically, it can be calculated by primary approximation from the relationship between the DC magnetic field and the magnetic flux density in the measurement steps before and after the DC magnetic field Hsat.

G (structure observation, composition distribution)
The toroidal magnetic core was cut and the cut surface was observed with a scanning electron microscope (SEM / EDX).

About the magnetic core of the obtained sample, as a result of evaluation by cross-sectional observation using a scanning electron microscope (SEM), alloy particles were bonded by grain boundaries in any sample. In addition, evaluation by composition mapping (SEM / EDX) confirmed that oxides having a higher Al ratio than the alloy phase inside the grains were formed at the grain boundaries. In addition, the specific resistance ρv of the magnetic core was as high as 1 × 10 ⁵ Ωm or more.

In addition, sample No. 5 to 7 and 9, the initial value (DC magnetic field 0.4 A / m) of the effective permeability μe at a frequency of 100 kHz is 34 or more, and the DC magnetic field Hsat at which the effective permeability μe is 80% with respect to the initial value. The magnetic flux density Bsat on the initial magnetization curve in the DC magnetic field Hsat was 400 mT or more at 5.6 kA / m or more. As shown in Table 1, sample no. 6, 7, and 9, the average particle size of the alloy particles is small, and the core loss Pcv is smaller when the amount of binder at the time of molding is larger, and as shown in FIG. The magnetic flux density Bsat with respect to Hsat could be increased. However, sample No. In No. 8, since the binder amount (PVA amount) is large and the average particle diameter of the alloy is small, the space factor of the magnetic core does not exceed 85% at the set molding pressure, and the initial value of the effective permeability μe is 34 or more. There wasn't. Moreover, in the sample obtained with the same average particle size raw material powder and the same binder amount, the DC magnetic field Hsat decreases as the space factor increases, but the initial effective magnetic permeability μe can be increased to increase the magnetic flux density Bsat. It was big. Further, in the magnetic cores of the examples (sample Nos. 5, 7, and 9), the initial value of the effective magnetic permeability μe and the DC magnetic field Hsat are larger than those of the comparative example (sample No. 2) as shown in FIG. Compared with the comparative example (sample No. 3), the DC magnetic field Hsat is large and excellent DC superimposition characteristics can be obtained, and the magnetic core obtained by the present invention is advantageous in obtaining excellent DC superimposition characteristics as a coil component. I understood.

Claims (4)

A magnetic core in which particles of an Fe-based soft magnetic alloy are bonded through an oxide layer of an element constituting the alloy,
Excited by alternating current superimposed with direct current,
The space factor exceeds 85%, and the initial value of the effective permeability μe at a frequency of 100 kHz is 34 or more,
The DC magnetic field Hsat at which the effective permeability μe is 80% of the initial value is 5.6 kA / m or more,
In addition, the magnetic core having excellent DC superposition characteristics in which the magnetic flux density Bsat on the initial magnetization curve in the DC magnetic field Hsat is 400 mT or more. The magnetic core according to claim 1,
The Fe-based soft magnetic alloy is a magnetic core containing Fe as a main component and containing an element M (M is at least one of Si, Cr, and Al) that is easier to oxidize than Fe. The magnetic core according to claim 2,
The Fe-based soft magnetic alloy is represented by a composition formula: aFebAlcCrdSi, and by mass%, a + b + c + d = 100, 75 ≦ a <100, 0 ≦ b <13.8, 0 ≦ c ≦ 7, 0 ≦ d ≦ 5 A magnetic core. The coil component provided with the magnetic core as described in any one of Claims 1-3, and the coil wound around the said magnetic core.

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