JP2008181923A - Magnetic component and manufacturing method thereof - Google Patents

Description

  The present invention relates to a magnetic component and a manufacturing method thereof. This magnetic component is useful for a transformer for a switching power supply, a reactor, and the like.

  In recent years, various electronic devices have been reduced in size and weight, and accordingly, switching power supplies mounted on the electronic devices are also required to be reduced in size. In particular, switching power supplies used for notebook personal computers, small portable devices, thin CRTs, and flat display panels of televisions are strongly required to be small and thin. However, in conventional switching power supplies, magnetic components such as transformers and reactors, which are main components, occupy a large volume, and thus there is a limit to miniaturization and thinning. Unless the volume of these magnetic components is reduced in size and thickness, it is difficult to reduce the size and thickness of the switching power supply.

  Conventionally, metal magnetic materials such as Sendust and Permalloy and oxide magnetic materials such as ferrite have been used for magnetic parts such as transformers and reactors used in such switching power supplies.

  These metal magnetic materials have high saturation magnetic density and magnetic permeability. However, since the electrical resistivity is low, eddy current loss increases particularly in the high frequency region. Therefore, it is impossible to reduce the size of the magnetic component by lowering the required inductance value by high-speed operation or high-frequency driving, which is a recent trend.

On the other hand, an oxide magnetic material has a higher electrical resistivity than a metal magnetic material, and hence eddy current loss generated in a high frequency region is small. However, since the saturation magnetic flux density is low, magnetic saturation is likely to occur, so that the volume cannot be reduced. That is, in any case, the volume of the magnetic core is the biggest factor determining the inductance, and it is difficult to reduce the size and thickness of the magnetic material unless the magnetic properties of the magnetic material are improved.
As described above, the conventional magnetic parts have a limit in miniaturization, and cannot sufficiently meet the demand for miniaturization and thinning of electronic devices.

As a method for solving this problem, a metal oxide magnetic material having a spinel composition represented by M-Fe _x O ₄ (M = Ni, Mn, Zn, x ≦ 2) is formed on the surface of a metal magnetic material composed of particles of 1 to 10 μm. A high-density sintered magnetic body coated with a material has been proposed (for example, see Patent Document 1).

  Further, a ferromagnetic fine particle powder of metal or metal oxide having a ferrite layer coating formed by ultrasonic excitation ferrite plating on the surface is compression-molded, and a magnetic path is formed between the ferromagnetic particles via the ferrite layer. There is also a proposal of a composite magnetic particle that forms (see, for example, Patent Document 2).

  Further, as a method for obtaining a soft magnetic molded body having a high density and a high specific resistance, soft magnetic metal particles, a high resistance material coated on the surface thereof, and phosphoric acid coated on the surface of the high resistance material There is also a proposal of soft magnetic particles characterized by comprising a system chemical conversion coating (see, for example, Patent Document 3).

In recent years, in order to improve resistivity, which is a drawback of metal magnetic materials, a magnetic material in which a nonmagnetic insulating oxide film with high electrical resistivity is formed on the surface of a metal material with high saturation magnetic flux density and high magnetic permeability. (For example, refer to Patent Document 4).
According to this method, the eddy current can be suppressed by increasing the electrical resistivity due to the effect of the nonmagnetic insulating film. That is, it can be used even at a high frequency such as MHz band.

  The magnetic material described above basically uses spherical particles or irregularly shaped particles pulverized by a ball mill or the like. Apart from this, as a method to improve the performance of magnetic materials by utilizing the shape anisotropy of particles, there is also a proposal to increase the magnetic permeability by reducing the influence of the demagnetizing field using flattened particles. (For example, refer to Patent Documents 5, 6, and 7).

In Patent Document 5, flat magnetic particles are filled in a mold slower than a predetermined speed, so that the main surface is oriented so as to be perpendicular to the direction of gravity. In patent document 6, it compacts in the state which orientated with the magnetic field of the direction perpendicular | vertical with respect to the direction of a magnetic path. In Patent Document 7 Examples 3 and 9, acicular powder or flat magnetic particles are put into a magnetic field press device and pressed in a direction perpendicular to the direction in which the magnetic field is applied. Magnetic components are obtained in which the axes are arranged in a certain direction, or the flat surfaces of the flat particles are arranged in the direction of the easy magnetization axis.
JP-A-56-38402 WO03 / 015109 pamphlet JP 2001-85211 A JP-A-53-91397 JP-A-6-267723 JP 2001-68365 A JP-A-3-278407

  For any of the methods described in Patent Documents 1 to 4, there is a trade-off relationship between magnetic permeability improvement and electrical resistivity improvement, and a material with a large magnetic permeability cannot be used at high frequencies because the resistivity is low. A high material has a magnetic permeability of about several tens to 100, and there is a problem that a high magnetic permeability cannot be obtained.

  For example, when Fe-Ni-based metal particles (untreated state, hereinafter referred to as bare particles) are press-molded at a filling rate of 95% or more, the magnetic permeability is about 100 in the state after pressing. By heat-treating this material, the magnetic permeability can be improved up to about 1000. However, with bare particles, the resistivity decreases to almost the metal crystal level due to diffusion bonding at the interface between the particles, up to several tens of kHz level. Can only be used in the frequency band.

When using the particles form an electrically insulating film such as SiO ₂ in the bare particles, resistivity after press molding and 1～100Omucm, exhibit greater resistivity, magnetic permeability is about 30 to 100, high Magnetic permeability cannot be obtained. When heat treatment at 500 to 900 ° C. is performed in order to increase the magnetic permeability, the magnetic permeability is increased, but there is a problem that the resistivity is lowered. This is due to the fact that the metal magnetic particles and the insulating film are interdiffused and the insulating properties of the insulating film are significantly reduced. On the other hand, the permeability does not increase without mutual diffusion. In other words, since the particles are spherical, the demagnetizing field between the particles is large, so that the magnetic permeability does not increase, or when the heat treatment is performed to reduce the demagnetizing field and the particles are mutually diffused, the resistivity decreases. End up.

  Further, when flat particles are used as in Patent Documents 5 and 6, the demagnetizing field increases in the direction perpendicular to the flat surface and decreases in the horizontal direction, so that the magnetic permeability is increased without mutual diffusion. Could be possible. However, these flat particles are present at random, and they are oriented in various directions when placed in a press mold. When pressed as it is, the flat surface is made horizontal or vertical in the direction of the magnetic field. Thus, since it cannot be controlled to align in a certain direction, in the end, only the same level of characteristics as when spherical particles are used can be obtained. Patent Document 5 discloses a method of aligning the orientation of flat particles by slowing the filling rate into the mold, but in reality, the effect on controllability is not great. Further, in the method described in Patent Document 7, the direction in which the easy axis is oriented is left to the control when the magnetic particles are produced, and is not controlled. The present invention improves the magnetic permeability without lowering the electrical resistivity by controlling the direction of the metal magnetic particles in which the magnetization facilitating axis is induced in the plane direction of the flat particles or the length direction of the acicular particles. With the goal.

The present invention has been made in order to solve the above-mentioned problems in view of such circumstances, and the gist of the present invention is in a method of manufacturing a magnetic component using a magnetic material formed by press-molding metal magnetic particles. The metal magnetic particles are flattened or needle-like particles, and the magnetization easy axis is induced in the plane direction of the flat particles or the length direction of the needle-like particles by heat treatment in a magnetic field. The metal magnetic particles are obtained by press-molding the metal magnetic particles with a magnetic field applied in a desired direction to induce an easy magnetization axis in the plane direction of the flat particles or in the length direction of the needle-like particles. The method of manufacturing a magnetic component is characterized in that the direction of the magnetic field is controlled.
The magnetic component of the present invention is manufactured by the above manufacturing method.

  According to the method for manufacturing a magnetic component of the present invention, the direction of the easy magnetization axis of the magnetic particles can be controlled. In addition, a high magnetic permeability can be obtained as compared with conventional spherical particles, flat particles or needle-like particles that are not processed at all. The magnetic component obtained by the manufacturing method of the present invention can be used as a core material of an inductor or a transformer. Compared to a conventional ferrite core material, the volume can be small to obtain the same inductance value. Miniaturization and thinning are possible.

  The metal magnetic particles used in the method for producing a magnetic component of the present invention are flattened or needle-like particles. Here, the needle shape refers to those having an aspect ratio (particle length / particle cross-sectional diameter) of 2 or more, and may have a spheroid structure. Moreover, a rod-shaped thing may be sufficient. As shown in FIG. 1, the flat particles 12 can be obtained by flattening the substantially spherical magnetic particles 11 with a press. The acicular particles can be obtained by a technique such as crystallization in an inert gas or heat treatment. Those having a spheroid structure can be formed by appropriately selecting a spraying pressure or the like at the time of water atomization or gas atomization. As the metal magnetic particles, pure iron may be used, and any Fe-Ni alloy, Co-Fe alloy, Fe-Si-Al alloy amorphous alloy or the like showing soft magnetic properties can be used.

  The flattened metal magnetic particles have a large demagnetizing factor in the thickness direction and a small demagnetizing factor in the in-plane direction. This depends on the shape, and in the case of a spherical shape, the demagnetizing factor is 0.33 in all directions, but the flattened particles have a thickness and an in-plane length (longitudinal length), It is determined by the width (the length in the direction orthogonal to the longitudinal direction), and the length direction is the smallest. The aspect ratio, which is the ratio of length to thickness, is preferably as large as possible in order to reduce the demagnetizing factor as long as crystal distortion does not occur in the particles. This aspect ratio can be adjusted by pressing pressure and pressing time during flattening by pressing.

  Also in the case of acicular particles, the demagnetizing factor in the cross-sectional direction is large and the demagnetizing factor in the length direction is small. Also in this case, depending on the shape, it is determined by the cross-sectional diameter of the acicular particle and the length of the particle, and the demagnetizing factor in the length direction is determined by the ratio of the length and the cross-sectional diameter (aspect ratio). The aspect ratio is preferably as large as possible for reducing the demagnetizing factor as long as no crystal distortion occurs in the grains.

  In the present invention, flattened or acicular metal magnetic particles are press-molded in a state where a magnetic field is applied in a desired direction, so that the axis of easy magnetization in the plane direction of the flat particles or the length direction of the acicular particles is obtained. Control the direction of the metal magnetic particles that induced When the particles are flat particles or acicular particles, if the metal magnetic particles are heat-treated in a rotating magnetic field with a magnetic field applied in a desired direction, the surface direction of the flat particles or the acicular particles An easy axis of magnetization can be induced in the length direction. Needle-like particles originally tend to be easily magnetized in the length direction due to shape anisotropy, but the difference in characteristics between the length direction and the cross-sectional direction can be further increased by heat treatment in a rotating magnetic field.

In this heat treatment in the rotating magnetic field, the magnetic field itself does not necessarily need to be rotated, and the relationship between the magnetic field and the metal magnetic particles may be as if the metal magnetic particles are in the rotating magnetic field. As shown in 2 (a), when the metal magnetic particles are placed in a container such as quartz and the container is placed in a magnetic field and rotated, the metal magnetic particles are placed in a rotating magnetic field when viewed from the metal magnetic particle side, If heat treatment is performed in this state, heat treatment is performed in a rotating magnetic field. The rotational speed of the rotating magnetic field is preferably 1 to 300 rpm, and in the case of flat particles, the applied magnetic field strength requires a magnetic field strength that saturates the easy axis of magnetization in the flat direction, and depends on the shape of the core to be created. 1000 kA / m is preferable, and the heat treatment temperature and time have different optimum ranges depending on the material, and therefore need to be determined according to the material composition. When the metal magnetic particles are crystalline, it is preferable to perform heat treatment at 400 to 900 ° C., and when the metal magnetic particles are amorphous materials, it is necessary to perform treatment at a temperature not exceeding the crystallization temperature, and heat treatment is performed at 250 to 450 ° C. Is common. The heat treatment time is preferably 1 to 100 hours.
The heat treatment atmosphere may be in a vacuum or an inert gas atmosphere such as nitrogen or argon. Further, when the metal magnetic particles are a material that is not easily oxidized, or a material that may be oxidized, an oxygen-containing atmosphere such as the air is preferable. Further, when there is no oxide film on the surface of the metal magnetic particles or when the oxide film is removed, the process may be performed in a water vapor atmosphere.

  In this heat treatment, the magnetic field is applied in all directions of the particles, but because of the shape magnetic anisotropy, in the case of flat particles, the particles are easily magnetized in the flat plane direction and difficult to magnetize in the thickness direction. The flat plane direction becomes anisotropic, and a hard magnetization axis is induced in the thickness direction. When the particles can move by applying vibrations to the particles during the heat treatment, the directions can be further aligned. As this vibration, the container in which the particles are placed may be vibrated, or the particles may be vibrated using ultrasonic waves. Also, as shown in FIG. 4, the direction may be aligned by allowing the particles to move by stirring the particles during the heat treatment. In FIG. 4, the stirring bar 18 is fixed, and the sample stage 14 that supports the container 13 containing the particles 12 rotates around the support bar 15 to stir the particles.

  Further, the flattened or needle-like metal magnetic particles to be subjected to press molding in a state where a magnetic field is applied in a desired direction may remain dry, or may be in a state dispersed in a liquid. . When the particles are dry, the degree of freedom is limited even if the particles are moved by applying vibration, etc., whereas when the particles are dispersed in the liquid phase, the degree of freedom of movement of the particles is high and the direction Control becomes easy. Accordingly, the direction can be easily controlled even with a magnetic field having a smaller magnetic field strength than when a magnetic field is applied during drying. Examples of the liquid used for the dispersion include organic solvents such as acetone, ethanol, methanol, methyl ethyl ketone, and water, and any other liquid that can disperse the particles can be used. However, in consideration of drying in a subsequent process, a liquid having high volatility is preferable, and an organic solvent having a boiling point lower than that of water is preferable.

Further, the flattened or needle-like metal magnetic particles used for press molding in a state where a magnetic field is applied in a desired direction may be made of only a magnetic material, but an insulating material may be formed on the surface of the metal magnetic particles. It is preferable from the viewpoint of improving the resistivity of the material.
Examples of the insulating material include insulating metal oxides such as silicon oxide, ferrite, and MFe _x O ₄ (M = Ni, Mn, Zn, etc., x ≦ 2).

Metal fine particles in a state where an easy axis of magnetization is induced in the plane direction of flat particles or the length direction of needle-like particles by applying a magnetic field in a desired direction are press-molded.
When the metal magnetic particles are flat particles, the magnetic field applied during press molding may be a rotating magnetic field. This rotating magnetic field is the same as the rotating magnetic field at the time of heat treatment, and it is sufficient that the relationship between the particles and the magnetic field is relatively rotated even if the magnetic field itself is not rotating. In this case, a ring core mold can be used as the press mold. As shown in FIG. 2B, when a particle is placed in a pressing mold as shown in FIG. 2B and a magnetic field is applied in a direction perpendicular to the pressing direction, the plane direction of the flat particle is oriented in a direction parallel to the applied magnetic field, and the direction of the particle Can be controlled. That is, the flat surfaces of the flat particles are aligned in a direction perpendicular to the thickness of the ring core, the direction of the flat surfaces is isotropic, and a hard axis is induced in the thickness direction. Next, as shown in FIG. 2 (c), when press molding is performed with this magnetic field applied, the thickness direction of the created ring core is the thickness direction of the flat particles. The permeability in the vertical direction can be increased.

  When the metal magnetic particles are acicular particles, the acicular particles have a shape magnetic anisotropy when the magnetic field for applying the metal magnetic particles to the molding die is applied during press molding. The particles are aligned in one direction according to the magnetic field. If the metal magnetic particles are heat-treated in advance in a rotating magnetic field, the direction of the acicular particles is more uniform in one direction, and the inductance value after molding can be further increased.

  The magnetic component of the present invention is manufactured by the above-described method for manufacturing a magnetic component, and the press-molded magnetic component has an easy axis of magnetization oriented in a predetermined direction, and achieves both high magnetic permeability and high resistivity. This magnetic component can be used as a core material for inductors and transformers. Compared to conventional ferrite core materials, the volume can be reduced to achieve the same inductance value, and the size and thickness can be reduced. It becomes possible. As a result, an unprecedented small and thin inductor or transformer and a switching power supply using them can be used as a power source for a notebook personal computer, a small portable device, a thin CRT, a television, or the like.

The present invention will be further described below using examples.
[Example 1]
1 and 2 show a schematic process flow of this embodiment. First, as shown in FIG. 1, the substantially spherical metal magnetic particles 11 were flattened by a press to produce flat metal magnetic particles 12. As the metal magnetic particles, super-malloy (Fe, Ni, Mo alloy, weight ratio 17: 78: 5), which is an Fe—Ni alloy, formed by a water atomization method and having an average particle diameter of 8 μm was used. The average thickness of the particles flattened by pressing was 1 μm. The flattened particles had a substantially circular flat surface, the diameter was 14 μm, and the aspect ratio was 14.

  Next, as shown in FIG. 2A, the flattened particles were placed in a quartz container 13 and heat-treated in a heat treatment furnace in a rotating magnetic field. That is, the quartz container 13 containing the flattened particles 12 was placed in the sample table 14 and heat-treated while rotating the sample table 14 around the support rod 15 in a magnetic field applied in a certain direction. The heat treatment conditions were a rotation speed of 100 rpm, an applied magnetic field of 400 kA / m, a heat treatment temperature of 650 ° C., and a heat treatment time of 2 hours. The heat treatment atmosphere was performed in a vacuum (degree of vacuum 0.001 Pa) in order to prevent oxidation of the particles. During the heat treatment in this magnetic field application state, the magnetic field is applied in all directions of the particles, but because of the shape magnetic anisotropy, it is easy to be magnetized in the flat direction and difficult to magnetize in the thickness direction. The flat plane direction is isotropic, and a hard axis is induced in the thickness direction.

Next, a ring core die is used as the die 16 for pressing, and as shown in FIG. 2B, a magnetic field is applied in a direction perpendicular to the pressing direction after the flat particles are placed in the die 16. did. The magnetic field strength was 800 kA / m.
The application of this magnetic field and the addition of vibrations to the particles facilitated the movement of the particles, so that the flat surface was oriented in a direction parallel to the magnetic field. Next, press molding was performed at a press pressure of 1960 MPa (20 ton / cm ² ) as shown in FIG. The frequency characteristic 23 of the magnetic permeability of the obtained ring core is shown in FIG.

[Comparative Example 1]
A ring core was produced in the same manner as in Example 1 except that the spherical particles 11 used in Example 1 were used as they were instead of the flat particles 12. The frequency characteristics 21 of the magnetic permeability of the obtained ring core are shown in FIG. The permeability of the ring core obtained in Example 1 at a frequency of 100 kHz was 120, whereas the permeability of the ring core obtained in this comparative example was as low as about 90.

[Comparative Example 2]
The flat particles 12 were put into a ring core forming mold 16 without performing heat treatment, and press-molded at a press pressure of 1960 MPa (20 ton / cm ² ) without applying a magnetic field. The frequency characteristics 22 of the magnetic permeability of the obtained ring core are shown in FIG. The permeability of the ring core obtained in this comparative example was also as low as about 90.

[Example 2]
A ring core was formed in the same manner as in Example 1 except that during the heat treatment in the rotating magnetic field, the particles were vibrated by vibrating the support rod 15 of the apparatus shown in FIG. The vibration was carried out by installing a vibration motor on the support rod 15 for rotating the sample stage and vibrating the support rod 15 at a vibration frequency of 50 Hz and a vibration stroke of 0.1 mm. By applying vibration in this manner, the particles move in the container, and a magnetic field is applied in the flat plane direction of all the particles. The permeability of the ring core obtained in Example 1 was 120 at a frequency of 100 kHz, whereas the permeability of the ring core obtained in this example was improved to about 130.

[Example 3]
As shown in FIG. 4, a stirring bar 18 is installed beside the support bar 15 of the sample stage 14 so that the stirring bar 18 remains in that position even if the sample stage 14 rotates around the support bar 15. Accordingly, a ring core was formed in the same manner as in Example 1 except that the particles were vibrated. The permeability of the obtained ring core at a frequency of 100 kHz was 125.

[Example 4]
A ring core was formed in the same manner as in Example 1 except that the magnetic field applied during molding was a rotating magnetic field rotating at 100 rpm. The permeability of the obtained ring core at a frequency of 100 kHz was 140.

[Example 5]
A ring core was formed in the same manner as in Example 1 except that the particles were placed in a press mold and press-molded while applying vibration to the particles. That is, flat particles heat-treated in a state where a magnetic field was applied were placed in a press mold and vibrated for 20 minutes with a vibrator while applying a magnetic field of 800 kA / m (frequency 50 Hz, vibration stroke 0.1 mm). . Thereafter, the vibrator was removed, and press molding was performed while applying a fine vibration by applying ultrasonic waves to the mold. The ultrasonic frequency was 25 kHz and the output was 1200 W. The permeability of the obtained ring core at a frequency of 100 kHz was 145.

[Example 6]
Instead of putting flat particles in which magnetic anisotropy is induced by heat treatment into a mold as they are, they are dispersed in a solvent 20 made of acetone, and this dispersion is put into a ring core forming mold as shown in FIG. A magnetic field of 400 kA / m was applied. Next, the solvent is spontaneously volatilized while applying a magnetic field to the dispersion, and the flat particles dried by solvent volatilization are pressed under the same conditions as in Example 1 as shown in FIGS. A ring core was formed in the same manner as in Example 1 except that. By applying a magnetic field to the dispersion, the direction of the particles could be controlled in the solvent, and the particles were adsorbed by the surface tension of the solvent during natural volatilization of the solvent. The magnetic permeability of the obtained ring core at a frequency of 100 kHz was 150.

[Example 7]
As the flat particles, the same flat particles as in Example 1 were used, and the surfaces of the flat particles that had been heat-treated in a magnetic field applied state as in Example 1 were coated with SiO ₂ using the water glass method. A ring core was formed in the same manner as in Example 1 except that it was used.
That is, flat particles were produced in the same manner as in Example 1, and heat treatment in a rotating magnetic field was performed on the flat particles under the same conditions as in Example 1 to induce magnetic anisotropy. The flat soft magnetic particles were placed in an alkaline aqueous solution in which water glass having a composition of Na ₂ O.xSiO ₂ .nH ₂ O (x = 2 to 4) was dissolved in water and dispersed. Hydrochloric acid is added to this dispersion to control pH to hydrolyze water glass to precipitate gel-like silicic acid (H ₂ SiO ₃ ) on the surface of the flat particles, and the silica-coated flat particles are dried to dry the SiO ₂ Was formed. The thickness of the coating was 10 nm. The thickness of the coating was controlled by the water glass concentration of the aqueous solution. The obtained ring core had a resistivity of 10 Ωcm and a magnetic permeability of about 120 as indicated by 32 in FIG.

[Comparative Example 3]
Instead of the flat particles heat-treated in the magnetic field application state, a 10 nm thick SiO ₂ film was formed in the same manner as in Example 7 except that spherical particles heat-treated in the magnetic field application state were used under the same conditions. This was used to form a ring core. The resistivity of the obtained ring core was 10 Ωcm. The magnetic permeability is shown at 31 in FIG.

[Comparative Example 4]
As needle-like particles, pure Fe (purity 99.999%) having a radial thickness of 2 μm, a length of 20 μm, and an aspect ratio of 10 is used. As shown in FIG. It put into the press die 16 and applied the magnetic field of one direction of 800 kA / m. As the mold 16, a mold having a shape in which an E-type core and an I-type core are connected without a gap as shown in FIG. 7 was used. When the magnetic field was applied, the particle length direction was parallel to the magnetic field, so the direction of the needle-like particles could be controlled by applying the magnetic field. Next, as shown in FIG. 2C, press molding was performed with a magnetic field applied, and molding was performed with the particles aligned. The press pressure was 1960 MPa (20 ton / cm ² ). The thickness direction of the core thus obtained was the cross-sectional direction of the acicular particles and became the hard axis of magnetization. In addition, the magnetic anisotropy in the plane of the core was such that the direction parallel to the magnetic field during pressing was the easy axis of magnetization, and the perpendicular direction was the hard axis of magnetization. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Example 8]
As shown in FIG. 2A, the same acicular particles 12 as used in Comparative Example 4 were heat-treated in a heat treatment furnace in a rotating magnetic field. That is, the quartz container 13 containing the needle-like particles 12 was placed in the sample table 14 and heat-treated while rotating the sample table 14 around the support bar 15 in a magnetic field applied in a certain direction. The heat treatment conditions were a rotation speed of 100 rpm, an applied magnetic field of 400 kA / m, a heat treatment temperature of 650 ° C., and a heat treatment time of 2 hours. The heat treatment atmosphere was performed in a vacuum (degree of vacuum 0.001 Pa) in order to prevent oxidation of the particles. A magnetic core was obtained in the same manner as in Comparative Example 4 except that the heat-treated acicular particles thus obtained were used. The thickness direction of the obtained core was the cross-sectional direction of the acicular particles, and became the hard axis of magnetization. In addition, the magnetic anisotropy in the plane of the core was such that the direction parallel to the magnetic field during pressing was the easy axis of magnetization, and the perpendicular direction was the hard axis of magnetization. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Comparative Example 5]
A magnetic core was prepared in the same manner as in Example 9 except that the spherical particles 11 used in Example 1 were used as they were instead of the acicular particles 12, and the resulting magnetic core was formed by winding 11 turns of the coil winding. The inductance value of the inductor at a frequency of 100 kHz was measured. The results are shown in Table 1.

[Example 9]
A magnetic core was obtained in the same manner as in Example 2 except that needle-like particles similar to those used in Example 8 were used instead of the flat particles, and a magnetic core having the shape shown in FIG. 7 was formed instead of the ring core. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Example 10]
A magnetic core was obtained in the same manner as in Example 3 except that needle-like particles similar to those used in Example 8 were used in place of the flat particles and a magnetic core having the shape shown in FIG. 7 was formed in place of the ring core. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Example 11]
A magnetic core was obtained in the same manner as in Example 5 except that needle-like particles similar to those used in Example 8 were used instead of the flat particles, and a magnetic core having the shape shown in FIG. 7 was formed instead of the ring core. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Example 12]
A magnetic core was obtained in the same manner as in Example 6 except that the same acicular particles as used in Example 8 were used instead of the flat particles, and a magnetic core having the shape shown in FIG. 7 was formed instead of the ring core. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The results are shown in Table 1.

[Example 13]
The needle-like particles similar to those used in Example 8 were heat-treated in a magnetic field applied state as in Example 1, and then the composition was Na ₂ O.xSiO ₂ .nH ₂ O (x = 2 to 4). The acicular particles were placed in an alkaline aqueous solution in which water glass was dissolved in water and dispersed. Hydrochloric acid is added to this dispersion to control pH to hydrolyze the water glass to deposit gel-like silicic acid (H ₂ SiO ₃ ) on the surface of the acicular particles, and then drying the silicic acid-coated acicular particles. A film of SiO ₂ was formed. The thickness of the coating was 10 nm. The thickness of the coating was controlled by the water glass concentration of the aqueous solution. A magnetic core was produced by performing press molding in the same manner as in Example 12 except that the silicic acid-coated needle-like particles were used. Usually when using spherical particles. Although only a magnetic permeability of about 60 was obtained, the average magnetic permeability of the magnetic core obtained in this example sufficiently exceeded 100. The resistivity at this time was 10 Ωm. The inductance value at a frequency of 100 kHz of an inductor formed by winding 11 turns of the coil winding on the obtained magnetic core was measured. The result is shown at 42 in FIG.

[Comparative Example 6]
A magnetic core similar to that obtained in Example 14 was prepared except that spherical particles formed with a 10 nm thick SiO ₂ film obtained in the same manner as in Comparative Example 3 were used, and a coil winding was formed on the obtained magnetic core. The inductance value of the inductor formed by winding 11 turns at a frequency of 100 kHz was measured. The result is shown at 41 in FIG.

  As is clear from Examples 1 to 7 and Comparative Examples 1 to 3, the magnetic component of the present invention formed by flattened metal magnetic particles in a state where the magnetization easy axis (flat direction) is aligned by a magnetic field, It turns out that it has both high magnetic permeability and high resistivity. On the other hand, magnetic parts using spherical particles and magnetic parts manufactured using flat particles without adopting the manufacturing method of the present invention cannot be said to have sufficiently high permeability. . Further, as is apparent from Examples 8 to 13 and Comparative Examples 4 to 6, the present invention was manufactured in a state in which the easy axis of magnetization was properly controlled in the length direction of the needle-like metal magnetic particles and the directions thereof were aligned. It can be seen that the magnetic component exhibits a higher inductance than the conventional magnetic component.

  The magnetic component obtained by the manufacturing method of the present invention can obtain higher magnetic permeability and higher resistivity than conventional magnetic components, and can be used as a core material for inductors and transformers. Compared to the material, the same inductance value can be obtained by using a small volume, and the size and thickness can be reduced. This makes it possible to produce an unprecedented small and thin inductor and transformer and a switching power supply using them as a power source for a notebook personal computer, a small portable device, a thin CRT, a television and the like.

It is a figure which shows the manufacturing method of a flat particle. It is process drawing which shows one embodiment of the manufacturing method of the magnetic component of this invention. Frequency characteristic diagram of magnetic permeability of magnetic component obtained in Example 1 Schematic diagram of heat treatment equipment with stir bar Process schematic diagram showing molding process of magnetic parts of Examples 6 and 12 The figure which shows the magnetic permeability characteristic of the magnetic component obtained in Example 7 Planar schematic diagram of magnetic core formed using acicular metal magnetic particles and schematic diagram showing direction of induced magnetic anisotropy The figure which shows the magnetic permeability characteristic of the magnetic component obtained in Example 13

Explanation of symbols

11: Spherical magnetic particles 12: Flat particles or needle-shaped particles 13: Quartz container 14: Sample stage 15: Support rod 16: Mold 20: Solvent 21: Comparative example 1
22: Comparative example 2
23: Example 1
24: Magnetic core 25: Easy magnetization axis direction 26: Hard magnetization axis direction 31: Comparative example 1
32: Example 7
41: Comparative example 6
42: Example 13

Claims (11)

  In a magnetic part manufacturing method using a magnetic material formed by press-molding metal magnetic particles, the metal magnetic particles are flattened or needle-shaped particles, and are easily magnetized by heat treatment in a magnetic field. It is a particle whose axis is guided in the plane direction of the flat particle or the length direction of the acicular particle, and the metal magnetic particle is press-molded in a state where a magnetic field is applied in a desired direction, whereby the plane direction of the flat particle Alternatively, a method of manufacturing a magnetic component, comprising: controlling a direction of the metal magnetic particle in which an easy magnetization axis is induced in a length direction of the acicular particle.   2. The method of manufacturing a magnetic component according to claim 1, wherein the magnetic field when the metal magnetic particles are heat-treated is a rotating magnetic field.   3. The method of manufacturing a magnetic component according to claim 2, wherein the direction of the particles is changed while applying vibration to the particles during the heat treatment in the rotating magnetic field.   3. The method of manufacturing a magnetic component according to claim 2, wherein the direction of the particles is changed by stirring the aggregate of particles with a stirring rod during the heat treatment in the rotating magnetic field.   The magnetic part manufacturing method according to any one of claims 1 to 4, wherein the magnetic field applied during press molding is a rotating magnetic field.   6. The method of manufacturing a magnetic component according to claim 5, wherein the metal magnetic particles are press-molded while applying mechanical vibration.   The magnetic component according to any one of claims 1 to 6, wherein the metal magnetic particles to be subjected to press molding are dried in advance by applying a magnetic field in a state of being dispersed in a liquid solvent. Production method.   The method of manufacturing a magnetic component according to claim 1, wherein the metal magnetic particles have an insulating film formed on the surface thereof.   The method of manufacturing a magnetic component according to claim 1, wherein the metal magnetic particles are flattened magnetic particles.   The method of manufacturing a magnetic component according to claim 1, wherein the metal magnetic particles are acicular magnetic particles.   A magnetic component manufactured by the method for manufacturing a magnetic component according to claim 1.

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