JP4097160B2 - Method for manufacturing electromagnetic interference suppressor - Google Patents

Description

  The present invention relates to a composite magnetic material having excellent complex permeability characteristics in a high frequency region and an electromagnetic wave absorber as one application example thereof, and more specifically, effective in suppressing electromagnetic interference that is a problem in high frequency electronic circuits / devices. The present invention relates to an electromagnetic interference suppressor made of a composite magnetic material having excellent complex permeability characteristics and a method for manufacturing the same.

  In recent years, digital electronic devices and other electronic devices that use high frequencies have spread, and in particular, mobile communication devices that use a quasi-microwave band are remarkable. Accordingly, soft magnetic materials used for inductance components and radio wave absorbers are also required to cope with higher frequencies.

  In addition, when the application is a small and light communication device such as a mobile phone, lightness, thinness, and robustness are added to the required characteristics of the soft magnetic material.

  One of the main factors hindering the increase in the frequency of soft magnetic materials is eddy current loss. As a means for reducing the loss, thinning and high electrical resistance in consideration of the skin depth can be mentioned. One obtained by alternately laminating a magnetic layer and a dielectric layer can be cited, and a representative example of the latter is Ni-Zn ferrite having high electrical resistance.

The demand for miniaturization and weight reduction is particularly remarkable for mobile communication devices typified by mobile phones , and high-density mounting of electronic components is the biggest technical issue. Accordingly, electronic components mounted overly densely, printed wiring, inter-module wiring, and the like are extremely close to each other, and further, the signal processing speed is increased, so that electrostatic coupling and / or electromagnetic Increasing the line-to-line coupling due to coupling, interference due to radiation noise, and the like have occurred, and there are not a few situations that hinder the normal operation of equipment.

  Conventionally, countermeasures have been mainly taken against such so-called electromagnetic interference by providing a conductor shield.

Japanese Patent Laid-Open No. 7-212079

  However, since the conductor shield is a countermeasure against electromagnetic interference using reflection of electromagnetic waves caused by impedance mismatch with space, even if a shielding effect is obtained, electromagnetic coupling by reflection from unwanted radiation sources is promoted. As a result, there are many cases that cause secondary electromagnetic interference. As a countermeasure, it is effective to suppress unnecessary radiation using the magnetic loss of the magnetic material, that is, the imaginary part permeability μ ″.

  That is, unnecessary radiation can be suppressed by disposing a magnetic body having a large magnetic loss between the shield body and the unnecessary radiation source.

  Here, since the thickness d of the magnetic material is inversely proportional to μ ″ in a frequency band satisfying the relationship of μ ″> μ ′, thin electromagnetic interference suppression that meets the above-described requirements for downsizing and weight reduction of electronic devices. In order to obtain a body, that is, a composite composed of a shield body and an absorber, a magnetic body having a large imaginary part permeability μ ″ is required. In addition, the above-described unwanted radiation often has a wide frequency component. Therefore, it is often difficult to specify the frequency component related to electromagnetic interference, and therefore, it is desired that the electromagnetic interference suppressor can cope with unnecessary radiation having a wider frequency.

  In order to meet such demands, the magnetic material is excellent in permeability high frequency characteristics and functions as a magnetic loss body in an arbitrary wide frequency range, that is, the value of μ ′ is large in the low frequency range, and μ ″> In the frequency region of μ ′, a magnetic material was studied in which μ ″ exhibits a large value over an arbitrary wide frequency range.

  As a result, the present inventors have previously proposed an electromagnetic interference suppressor that utilizes magnetic loss ranging from several tens of MHz to several GHz, which is thought to be manifested by magnetic resonance in soft magnetic powder having shape anisotropy (see above). Patent Document 1).

  Furthermore, the present inventors have developed a plurality of magnetic resonances having different frequencies so that individual magnetic losses appearing in different frequency regions corresponding to each magnetic resonance are superimposed, and the resulting broadband In addition, an electromagnetic interference suppressor (Japanese Patent Application No. 7-183911) utilizing a unique μ ″ dispersion characteristic is provided.

Flat soft magnetic metal powder used in these inventions has a higher anisotropy field H _k in comparison with a spherical metal powder of the same composition, which is the contribution of the shape anisotropy by flattened , that is, due to demagnetization factor N _d. Here, the demagnetizing factor _Nd is given by the shape of the powder and the aspect ratio. However, when the aspect ratio exceeds 10, it almost saturates, and even if a larger aspect ratio is given, the amount of change is small thereafter. Therefore, there is a problem that the range in which the magnetic resonance frequency can be varied is relatively limited.

  As a result of careful consideration from the various experiences and the above-mentioned viewpoints, the present inventors pay attention to stress strain generated when flattening a powder having a small shape anisotropy such as a spherical powder. The magnetostriction constant λ, which was considered to be a value close to 0, was set to λ ≠ 0, and the sign, that is, the direction of anisotropy due to strain was also actively used, and the residual strain was further reduced by annealing. It was expected that a wider range of magnetic resonance frequencies could be given in combination with the shape anisotropy.

  On the other hand, in order to obtain a desired frequency characteristic of the magnetic permeability, it is necessary to take measures to prevent the magnetic permeability from being deteriorated due to the eddy current at a frequency lower than that at which magnetic resonance occurs.

  As described above, as one effective eddy current countermeasure, a laminated structure in which a magnetic layer and a dielectric layer are alternately laminated has been proposed and partially put into practical use. A feature of the composite magnetic body having this laminated structure is that the thickness of the magnetic layer is equal to or less than the skin depth determined by the electric resistance, the magnetic permeability and the frequency. However, this laminated structure magnetic material has a problem that the permeability characteristic deteriorates because a displacement current flows through the dielectric layer. Here, the displacement current depends on the size of the laminated magnetic body (that is, the direction perpendicular to the laminating direction), so the influence can be eliminated by subdividing the laminated magnetic body into a column structure. Is possible. Although it is not easy to realize such a laminated structure magnetic body by a so-called thin film forming process such as sputtering, practical application is facilitated by applying a soft magnetic powder to the magnetic layer.

That is, 1) the soft magnetic powder corresponding to the magnetic layer is thinner than the skin depth, and 2) the soft magnetic powder is sufficient to make the demagnetizing factor _Nd approximately 1. 3) By providing a dielectric layer obtained by oxidizing the surface of the soft magnetic powder as an equivalent to the dielectric layer, a composite magnetic body with extremely small eddy current loss can be obtained. Expected to be able to get.

  Realization of such a composite magnetic material will not only give excellent high-frequency permeability characteristics, but also provide electrical non-conductivity, so it will be extremely effective for matching impedance against space as a radio wave absorber. Is also expected.

  That is, the magnetostriction constant λ (λ ≠ 0) is actively used to realize a wide range of magnetic resonance frequencies, the thickness of the soft magnetic powder is specified, and a dielectric layer is provided on the surface of the soft magnetic powder. As a result, the inventors have invented a composite magnetic material that has low eddy current loss and is less likely to cause impedance mismatch with space.

  That is, according to the present invention, there can be obtained a composite magnetic body comprising a soft magnetic powder having a positive magnetostriction constant λ and processed into a flat shape, and an organic binder.

  In addition, according to the present invention, there can be obtained a composite magnetic body comprising a soft magnetic powder having a negative composition of magnetostriction constant λ and processed into a flat shape, and an organic binder.

  Further, according to the present invention, in the composite magnetic body, the soft magnetic powder is processed into the flat shape and then subjected to an annealing process for reducing residual strain generated by the processing. A composite magnetic body characterized by the following is obtained.

  According to the present invention, in any one of the composite magnetic bodies, the average thickness of the soft magnetic powder processed into the flat shape is smaller than the skin depth δ at the use frequency of the composite magnetic body. A composite magnetic body characterized by the following is obtained.

  According to the present invention, in any one of the above composite magnetic bodies, the soft magnetic powder processed into a flat shape is oriented and arranged in the composite magnetic body. Is obtained.

  According to the present invention, in any one of the above composite magnetic bodies, the soft magnetic powder has a composite magnetic body having an oxide layer at least on the surface thereof.

  Further, according to the present invention, in the composite magnetic body, the soft magnetic powder having an oxide layer on at least the surface thereof may be obtained using an oxygen-containing mixed gas by a slow acid method in a gas phase or a slow acid method in a liquid phase. A magnetic composite characterized in that the surface is formed by oxidizing the surface is obtained.

  According to the present invention, any one of the composite magnetic bodies comprises the soft magnetic powder and the organic binder, and is electrically non-conductive. The body is obtained.

  Moreover, according to the present invention, a composite magnetic body comprising at least two flat soft magnetic powders having different sizes and / or different signs of magnetostriction constant λ and an organic binder can be obtained.

  In addition, according to the present invention, a composite magnetic body comprising at least two flat soft magnetic powders having different annealing conditions and an organic binder can be obtained.

  The present invention also relates to a method for producing a composite magnetic body comprising a soft magnetic powder and an organic binder, wherein the soft magnetic powder is processed into a flat shape, and residual strain generated in the soft magnetic powder by the processing. An annealing treatment for relaxation is performed, and an oxide layer is formed with an oxygen-containing gas by a slow acid method in a gas phase or a slow acid method in a liquid phase on at least the surface of the annealed soft magnetic powder. A method of producing a composite magnetic material characterized by forming the magnetic material can be obtained.

  The present invention also relates to a method for producing a composite magnetic body comprising a soft magnetic powder and an organic binder, wherein the soft magnetic powder is processed into a flat shape, and a gas phase is formed on at least the surface of the soft magnetic powder. Residual strain generated by forming an oxide layer with an oxygen-containing gas by a medium-gradient acid method or a liquid-phase slow acid method and processing the soft magnetic powder with the oxide layer into the flat shape. A method for producing a composite magnetic body characterized by performing an annealing treatment for relaxation can be obtained.

  The present invention also relates to a method for producing a composite magnetic body comprising a soft magnetic powder and an organic binder, wherein the soft magnetic powder is processed into a flat shape, and the processed soft magnetic powder is subjected to the process described above. An annealing process for alleviating residual strain generated in the soft magnetic powder by processing, and a process of forming an oxide layer with an oxygen-containing gas by a slow acid method in a gas phase on at least the surface of the soft magnetic powder. Are obtained simultaneously, and a method for producing a composite magnetic body is obtained.

  In addition, according to the present invention, any one of the above-described methods for producing a composite magnetic body, when the soft magnetic powder is processed into a flat shape, the strain applied to the soft magnetic powder, or the conditions for the annealing treatment By changing the frequency, the frequency characteristics of the complex magnetic permeability of the composite magnetic body can be controlled to obtain a method of manufacturing the composite magnetic body.

  Furthermore, according to the present invention, there is provided an electromagnetic interference suppressor including any one of the composite magnetic bodies as a component thereof, wherein the composite magnetic bodies have different frequency regions corresponding to residual strains of different sizes. An electromagnetic interference suppressor characterized in that magnetic resonance appearing in the lowest frequency region among the plurality of appearing magnetic resonances is in a frequency region lower than the lower limit of the desired electromagnetic interference suppression frequency band is obtained.

  According to the present invention, in a composite magnetic body composed of soft magnetic powder and an organic binder, the magnetostriction constant λ is not zero while realizing a high real part permeability with a configuration capable of suppressing deterioration of the permeability characteristics due to eddy current. By using a soft magnetic powder of a value and further combining an annealing treatment, it is possible to change the residual strain amount and control the high-frequency permeability characteristics in a wide range.

  In addition, in the electromagnetic interference suppressor using the composite magnetic material composed of a plurality of soft magnetic powders having different residual strain amounts, which is an embodiment of the present invention, a wide μ ″ dispersion due to the appearance of a plurality of different magnetic resonances. Therefore, according to the present invention, a thin electromagnetic wave effective for suppressing interference of electromagnetic waves inside high-frequency electronic devices such as mobile communication devices can be obtained. An interference suppressor can be obtained.

  The composite magnetic body and electromagnetic interference suppressor of the present invention can be easily provided with flexibility as can be seen from its constituent elements, and can cope with complicated shapes, severe vibration resistance, and impact requirements. Is possible.

  In the present invention, a metal soft magnetic material such as iron aluminum silicon alloy (Sendust), iron nickel alloy (Permalloy), or amorphous alloy having a high high frequency magnetic permeability can be used as a raw material.

In the present invention, these raw materials are flattened by pulverization, stretching, tearing, etc., and the thickness thereof is made equal to or less than the skin depth, and the soft magnetic material is flattened so that the demagnetizing factor _Nd is approximately 1. The aspect ratio of the body powder needs to be approximately 10 or more. Here, the skin depth δ is given by the following equation.

δ = (ρ / πμf) ^1/2
In the above equation, ρ is specific resistance, μ is magnetic permeability, and f is frequency. Therefore, the value of the skin depth δ varies depending on the target frequency. To obtain the desired skin depth and aspect ratio, it is one of the simplest means to specify the average particle diameter of the starting raw material powder. One. Typical pulverizing means that can be used for this pulverization, stretching, and tearing process include a ball mill, an attritor, and a pin mill. The thickness and aspect ratio of the soft magnetic powder satisfying the above-described conditions can be obtained. If it is possible, there is no limitation on the pulverizing means, but it is necessary to set the processing means and the processing conditions in consideration of the magnitude of the residual strain generated by the stretching / tearing process closely related to the effect of the present invention.

  In the present invention, when a raw material magnetic material having a positive magnetostriction constant λ is used, shape magnetic anisotropy occurs due to stretching and tearing, and magnetostriction anisotropy (magnetoelastic effect) due to residual strain occurs, Since both directions are the same, the anisotropic magnetic field is the sum of both. Therefore, the anisotropic magnetic field has a larger value and the magnetic resonance frequency is higher than when a raw material having a magnetostriction constant λ of zero is used.

  By the way, the residual strain generated by the flattening process is alleviated by applying an appropriate annealing process. Therefore, in the composite magnetic body using the raw material powder that has been subjected to the annealing process after the flattening process, it depends on the annealing process conditions. Magnetic resonance appears at the frequency fr. This magnetic resonance frequency fr is lower than that of a composite magnetic body using magnetic powder that has not been annealed, and higher than that of a composite magnetic body using magnetic powder having a magnetostriction constant λ of zero, thereby controlling the annealing conditions. Thus, the magnetic resonance frequency can be arbitrarily set within the range. On the other hand, when a raw material magnetic material having a negative magnetostriction constant λ is used, the direction of strain magnetic anisotropy (magnetoelastic effect) caused by residual strain is orthogonal to the direction of shape magnetic anisotropy. The isotropic magnetic field becomes smaller and the magnetic resonance frequency becomes lower than that in the case of a zero magnetostrictive material.

  Thus, by combining the shape anisotropy, the sign of the magnetostriction constant λ, and the annealing treatment conditions, the magnetic resonance frequency fr can be significantly changed.

Further, in the present invention, the soft magnetic powder has a dielectric on the surface so that the individual magnetic powders can be electrically isolated from each other, that is, the non-conductivity of the composite magnetic material can be ensured even in a highly filled state of the magnetic powder. A body layer must be formed. This dielectric layer is a metal oxide layer composed of constituent elements obtained by oxidizing the surface of the metal magnetic powder and oxygen. For example, in the case of an iron aluminum silicon alloy (Sendust), mainly AlO _x And SiO _x . As an example of means for oxidizing the surface of the metal powder, the oxygen partial pressure is controlled in a hydrocarbon-based organic solvent or in an inert gas atmosphere especially for a powder having a relatively small size and high activity. In view of ease of control, stability, and safety, it is preferable to carry out an oxidation treatment by a slow acid method in a liquid phase or a gas phase slow acid method in which a nitrogen-oxygen mixed gas is introduced.

  Note that either the gradual acid treatment for surface oxidation or the annealing treatment for reducing the residual strain described above may be performed first or in the same process.

  Examples of the organic binder used as one component of the present invention include polyester resins, polyethylene resins, polyvinyl chloride resins, polyvinyl butyral resins, polyurethane resins, cellulose resins, ABS resins, nitrile-butadiene rubbers, styrene- Examples thereof include butadiene rubber, epoxy resin, phenol resin, amide resin, imide resin, and copolymers thereof.

  The means described above for kneading and dispersing the constituent elements of the present invention to obtain a composite magnetic material is not particularly limited, and a preferred method may be selected based on the properties of the binder used and the ease of the process.

  Means for orienting and arranging the magnetic particles in the magnetic material mixture thus kneaded and dispersed includes a method using shear stress and a method using magnetic field orientation, and either method may be used.

  Next, an experiment was conducted to verify the effect of the present invention, which will be described in detail below as an example.

First, prepare multiple iron-nickel alloy powders and iron-aluminum-silicon alloy powders with different magnetostriction constants λ produced by water atomization method, and crush, stretch, and tear under various conditions using an attritor and pin mill. Further, the mixture is stirred for 8 hours while introducing a nitrogen-oxygen mixed gas having an oxygen partial pressure of 35% in a hydrocarbon-based organic solvent, subjected to a gradual acid treatment in the liquid phase, and then subjected to a classification treatment to provide an anisotropic magnetic field (H _k ). A plurality of powder samples having different values were obtained. As a result of surface analysis of the obtained powder, the formation of metal oxide was clearly confirmed, and the presence of an oxide film on the surface of the sample powder was recognized.

  Incidentally, a sample obtained by drying a pulverized, stretched / tear-processed iron-nickel alloy powder and iron aluminum silicon alloy powder under reduced pressure, and gas-phase gradual acid in a nitrogen-oxygen mixed gas atmosphere having an oxygen partial pressure of 20%. In addition, a metal oxide is detected on the surface, and at least the surface of the soft magnetic powder that can be used in the composite magnetic material of the present invention is oxidized by a slow acid method in a liquid phase or a slow acid method in a gas phase It was confirmed that it could be created.

  In verifying the effect of the present invention, a composite magnetic body described below was prepared using these powder samples, and the μ-f characteristic and the electromagnetic interference suppression effect were examined.

  For measuring the μ-f characteristic, a composite magnetic material sample processed into a toroidal shape was used. This was inserted into a test fixture forming a one-turn coil, and the impedance was measured to obtain μ ′ and μ ″.

  On the other hand, the electromagnetic interference suppression effect is verified by the evaluation system shown in FIG. 1. As the electromagnetic interference suppression body sample 10, a composite magnetic body 2 having a thickness of 2 mm and a side length of 20 cm with a copper plate 8 lined is used. Using. Here, a micro loop antenna 4 and 5 having a loop diameter of 1.5 mm is used for the wave source element and the receiving element, and a sweep generator (electromagnetic wave source oscillator) 6 is used for the signal source connected to the receiving element. A network analyzer (electromagnetic field strength measuring device) 7 was used for measuring the coupling level.

[Verification sample 1]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 1 shown in Table 1 below. Obtained.

  When the obtained sample 1 was analyzed using a scanning electron microscope, the particle arrangement direction was the in-plane direction of the sample film.

Here, the magnitude of the magnetostriction is a value of a strain amount dl / l × 10 ⁻⁶ at H = 200 oersted, which is a verification sample 2 to a verification sample 4 described later, a comparative sample 5 and a comparative sample. The same applies to Sample 6.

[Verification sample 2]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 2 shown in Table 2 below. Obtained.

  When the obtained sample 2 was analyzed using a scanning electron microscope, the particle arrangement direction was the in-plane direction of the sample film.

[Verification sample 3]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 3 shown in Table 3 below. Obtained.

  When the obtained sample 3 was analyzed using a scanning electron microscope, the particle arrangement direction was the in-plane direction of the sample film.

[Verification sample 4]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours, and a verification sample 4 shown in Table 4 below was obtained. Obtained.

  When the obtained sample 4 was analyzed using a scanning electron microscope, the particle arrangement direction was the in-plane direction of the sample film.

[Comparative Sample 5]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 5 shown in Table 5 below. Obtained.

  In addition, when the obtained sample 5 was analyzed using the scanning electron microscope, it was a substantially isotropic arrangement | sequence.

[Comparative Sample 6]
A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 6 shown in Table 6 below. Obtained.

  In addition, when the obtained sample 6 was analyzed using the scanning electron microscope, the particle arrangement direction was the sample film in-plane direction.

  Table 7 below shows the real permeability μ ′ and the magnetic resonance frequency fr of each of the obtained samples.

  FIG. 2 shows μ-f characteristics of Sample 1 to Sample 2 as a verification example of the present invention and Sample 6 as a comparative example, and magnetic resonance frequency fr is a magnetic powder having a positive magnetostriction constant λ. The value of the real part permeability μ ′ is the highest, and the value of the real part permeability μ ′ is the highest in the sample 6 in which the magnetostriction constant λ is almost zero. Sample 2 was obtained by subjecting the magnetic powder used in Sample 1 to the raw material powder that was annealed. As apparent from FIG. 2, the value of the magnetic resonance frequency fr and the real part permeability μ ′ Both values are located between the sample 1 and the sample 6.

  On the other hand, as can be seen from Table 7, in the sample 3 having the negative magnetostriction constant λ, the magnetic resonance frequency fr is lower than that of the sample 6 in which the magnetostriction constant λ is substantially zero, and the real part transmission The value of magnetic permeability μ ′ is also larger than that of sample 6. In any case, the difference in the real part permeability μ ′ is obvious as compared with the sample 5 which is a comparative sample using the substantially spherical raw magnetic powder.

  From these results, by setting the magnetostriction constant λ to a non-zero value and further changing the residual strain amount by annealing, the frequency characteristics of the magnetic permeability can be controlled in a wide range, and in addition, the thickness of the magnetic powder It is clear that high permeability can be obtained in a high frequency range by specifying the thickness and providing a dielectric layer on the surface.

  Table 8 below shows the results of comparing the powder filling rate, the surface resistance, the μ ″ distribution, and the electromagnetic interference suppression effect for the verification sample 4 and the comparative sample 5.

  Here, the surface resistance is a value measured by the ASTM-D-257 method, the μ ″ distribution is a relative comparison with each other, and the value of the electromagnetic interference suppression effect is based on a copper plate as a reference (0 dB) Is the amount of signal attenuation.

  From Table 8, the effects described below are clear.

That is, in both the verification sample and the comparative sample of the present invention, the surface resistance value is 10 ⁷ to 10 ⁸ Ω, and at least the surface is oxidized, so that the composite magnetic material can be made non-conducting. The surface reflection of electromagnetic waves due to impedance mismatching as seen in conductors and bulk metallic magnetic materials can be suppressed.

  Furthermore, the verification sample of the present invention shows a good electromagnetic interference suppression effect even though the powder filling rate is lower than that of the comparative sample, and the expansion effect of the μ ″ distribution according to the present invention suppresses the electromagnetic interference. It can be understood that it is effective.

In the Example of this invention, it is the schematic which shows the evaluation system used for the characteristic evaluation of the electromagnetic interference suppression body. In the Example of this invention, it is a figure which shows the μ-f characteristic of each sample produced on the conditions of the sample 1 for verification, the sample 2 for verification, and the sample 6 for a comparison.

Explanation of symbols

2 Composite magnetic material 4, 5 Micro loop antenna 6 Electromagnetic wave source transmitter 7 Electromagnetic field strength measuring device 8 Copper plate 10 Electromagnetic interference suppressor

Claims (3)

In a method of manufacturing an electromagnetic interference suppressor comprising a composite magnetic body comprising a soft magnetic powder and an organic binder, and suppressing unwanted radiation using the imaginary part permeability μ ″ of the composite magnetic body,
The magnetostriction constant is positive in order to increase the magnetic resonance frequency of the imaginary part permeability μ ″ as compared with the case where the soft magnetic material raw material magnetic material having zero magnetostriction constant is used. Using raw magnetic material,
The magnetostriction constant is negative in order to lower the magnetic resonance frequency of the imaginary part permeability μ ″ as compared with the case where the raw magnetic material of the soft magnetic powder has a magnetostriction constant of zero. By using raw material magnetic material,
A method of manufacturing an electromagnetic interference suppressor, wherein the magnetic resonance frequency of the imaginary part permeability μ ″ is controlled. In the manufacturing method of the electromagnetic interference suppressor according to claim 1,
The magnetic resonance frequency of the imaginary part permeability μ ″ is higher than that in the case of using a raw magnetic material having a magnetostriction constant of zero, and the imaginary part permeability is higher than in the case of using a raw magnetic material having a positive magnetostriction constant. In order to lower the magnetic resonance frequency of the magnetic susceptibility μ ″, the raw material magnetic material having a positive magnetostriction constant is processed into a flat powder, and then the powder is subjected to an annealing treatment to alleviate residual strain due to the processing. Apply
A method of manufacturing an electromagnetic interference suppressor characterized by that. In the manufacturing method of the electromagnetic interference suppression body of Claim 1 or Claim 2,
The dispersion characteristics of the imaginary part permeability μ ″ obtained by developing a plurality of magnetic resonances having different frequencies are made wider by using the control of the magnetic resonance frequency.
A method of manufacturing an electromagnetic interference suppressor characterized by that.

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