JP2002075785A - Feedthrough emi filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a feedthrough EMI filter, having, proper high-frequency characteristics, a high withstand voltage and hence high reliability and capable of being reduced in size. SOLUTION: A composite magnetic material, containing a mixture of magnetic particles in which surfaces of spherical magnetic metal particles to substantially become a single crystal are entirely or partly covered with a dielectric layer and having a mean particle size of 0.1 to 10 μm and a resin material, is used. A cylindrical composite magnetic material 13, made of the composite magnetic material, is provided around a central conductor 16. The feedthrough EMI filter is realized by a laminated structure, by using the composite magnetic material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a tri-plate structure in which a conductor penetrates through the center of a cylindrical magnetic body having an external conductor, or a laminated structure in which external conductors are opposed above and below a central conductor. The present invention relates to a feed-through EMI filter. More specifically, a high-frequency feed-through EMI filter that is inserted into a power supply line in a high-speed digital circuit and has a performance suitable for suppressing electromagnetic interference noise transmitted through the line and has a simple structure and excellent reliability. About.

[0002]

2. Description of the Related Art A conventional through-type EMI filter is disclosed in, for example, Japanese Patent No. 2884512.
This EMI filter uses a composite material composed of a Si-Fe magnetic powder and a resin, and embeds the composite material between a cylindrical outer conductor and a central inner conductor. Japanese Patent Application Laid-Open No. 8-204486 discloses an EMI filter using a composite material composed of a resin and metal magnetic powder.

[0003] Japanese Utility Model Publication No. 57-40512 and Japanese Utility Model Publication No. 57-40515 disclose an EMI filter in which a cylindrical through capacitor and a ferrite chip bead are combined.

[0004] The attenuation amount α of the feed-through EMI filter
(dB / cm) is represented by the following equation. α ≒ 3 × f × (μ_r´ ・ ε_r´) × [{(tan²δ_M+
1) (tan²δ_D+1)}^1/2+ Tanδ_M・ Tanδ_D-1]
^1/2  tanδ_M= Μ_r"/ Μ_r´ tanδ_D= Ε_r"/ Ε_r´ In the above equation, in order to obtain a large attenuation, the magnetic permeability
Real part μ of_r´ and the real part ε of the permittivity_r´ is GH
It is desirable to have a high value even in the high frequency part exceeding z
You.

[0005]

The above-mentioned Patent No. 28845
The coaxial type EMI filter described in Japanese Patent Publication No. 12 has the following problems. (A) To increase the magnetic permeability of the composite material, flaky Si
-Since the Fe-based magnetic powder is used, the high-frequency characteristics are poor, and it is difficult to cope with further higher frequencies in the future. (B) The Si-Fe-based magnetic powder has low insulation properties, and an insulating resin or the like is essential for the exterior of the composite magnetic body, and the shape becomes large. (C) Since the Si-Fe-based magnetic powder is used, a high dielectric constant cannot be obtained, and therefore, it is difficult to obtain an attenuation amount as a filter.

On the other hand, as described in JP-B-57-40512 and JP-B-57-40515,
An EMI filter using a cylindrical feedthrough capacitor and a ferrite chip bead has the following problems. (A) Since the feedthrough capacitor and the chip beads are manufactured and combined as individual components, miniaturization is difficult. (B) Since chip beads using sintered ferrite are used, high-frequency characteristics are deteriorated. That is,
In the case of ferrite, as the frequency increases, the loss due to domain wall resonance or natural resonance becomes remarkable, and the function as an impedance element also decreases, so that a high-frequency noise removal effect cannot be expected.

Further, as described in JP-A-8-204486, in an EMI filter using a composite material composed of a resin and a metal magnetic powder, the withstand voltage must be ensured because the magnetic powder is a metal powder. Is difficult, which leads to a decrease in reliability.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a feed-through EMI filter which has good high-frequency characteristics and can be configured in a small size.

Another object of the present invention is to provide a penetration type EMI filter having a high withstand voltage and a high reliability.

[0010]

According to a first aspect of the present invention, there is provided a through-type EMI filter in which the whole or a part of the surface of a spherical magnetic metal particle which is substantially a single crystal is covered with a dielectric layer. A composite magnetic material composed of a mixture of magnetic particles having a particle size of 0.1 to 10 μm and a resin material, comprising a cylindrical composite magnetic body made of the composite magnetic material around a central conductor, Is characterized by having an external conductor on the outer periphery.

As described above, small-diameter spherical particles in which all or part of the surface of metal particles are covered with a dielectric layer can be obtained by a spray pyrolysis method as described in Japanese Patent Publication No. 3-68484. Can be. In the spray pyrolysis method, a solution containing a metal salt as a magnetic substance is sprayed into droplets, and the droplets are heated in the air at a temperature higher than the decomposition temperature of the metal salt and higher than the melting point of the metal. Is a method of producing a metal powder. When a dielectric layer is formed on the surface of the metal powder, for example, when a barium titanate layer is formed, a solution in which a compound such as a barium salt or a titanyl salt is dissolved together with the nickel salt is spray-heated, and these dielectric materials are sprayed. Heat at a temperature higher than the decomposition temperature of the body salt. Thereby, a dielectric layer is formed on the surface of the substantially single-crystal spherical magnetic metal particles.

Such a dielectric-coated metal particle is dispersed and mixed in a resin, so that the sintered dielectric is crushed into a powder as in the prior art, and is compared with a flake or a block with irregularities. Because of its spherical shape and small diameter, it is mixed with the resin with good dispersibility. When the particles are dispersed in a resin, the dielectric layer is, for example, 1 wt.
Even with the addition amount of%, the insulation resistance and withstand voltage of the composite magnetic material can be improved.

Further, also in the composite magnetic material, the shape of the coated metal particles retains the shape before being mixed as the composite magnetic material, and the coated dielectric layer is held without being destroyed. I have. This contributes to the improvement of the withstand voltage described above.

Since the surface of the metal particles is covered with the dielectric layer, there is no problem of corrosion such as rust.

As described above, when the magnetic metal particles are generated by the spray pyrolysis method, the lower limit of the particle size is 0.05 μm,
The upper limit is about 20 μm. Actually the particle size is 0.05 ~
It is an aggregate of particles in which 20 μm particles occupy 95 wt%. Practically, preferably, the average particle size is 0.1 to
It is about 10 μm.

As described above, since the metal particles have a small diameter and the surface is covered with the dielectric layer, the Si-Fe-based magnetic powder described above is used while being a composite magnetic material using the metal particles. The eddy current loss, which is one of the losses as a magnetic material, is smaller than that of the magnetic material, and the high-frequency characteristics are improved. In addition, since the surface of the metal particles is covered with the dielectric layer, GH
In a high frequency band exceeding z, a desired amount of attenuation can be easily obtained, and a noise removing effect can be obtained.

According to a second aspect of the present invention, there is provided a penetration type EMI filter, wherein the entire surface or a part of the surface of the substantially single crystal spherical magnetic metal particles is covered with a dielectric layer and has an average particle diameter of 0.1 to 10 μm.
using a glass cloth-containing metal-clad substrate and a prepreg made of a composite magnetic material of m magnetic particles and a resin material,
The laminated structure of the glass cloth-containing metal-clad substrate and the prepreg is characterized in that external electrodes are formed above and below the center conductor with a composite magnetic body interposed therebetween.

With such a configuration, a through-type structure in which an inductance component is formed by the center conductor and the composite magnetic material covering the periphery thereof, and a capacitance is formed between the center conductor and the upper and lower conductors in a distributed capacity. Is obtained. Here, since the composite magnetic material according to the present invention covers small-diameter magnetic metal particles with a dielectric layer, it can have high insulation and dielectric constant, and is a thin surface-mount type suitable for use. A through-type EMI filter can be realized.

According to a third aspect of the invention, there is provided a feed-through EMI filter in which a layer made of a material having a higher dielectric constant than resin is formed as the dielectric layer. By using metal particles having such a dielectric layer formed thereon, the dielectric constant of the composite magnetic material can be increased. Therefore, a noise removing effect as an EMI filter can be obtained.

According to a fourth aspect of the present invention, the thickness of the dielectric layer on the surface of the metal particles is 0.005 μm to 5 μm.
It is characterized by being. Here, if the thickness of the dielectric layer is 0.005 μm or more, it can contribute to the improvement of the dielectric constant or withstand voltage. Further, when the thickness of the dielectric layer is 5
If it exceeds μm, it becomes difficult to produce particles.

The thickness in this case means the maximum thickness of the coating, and the coating does not necessarily cover the entire surface of the metal particle, and may occupy about 50% of the surface of the metal particle. I just need.

A fifth aspect of the present invention is characterized in that the coated metal particles are mixed in a resin of 30 to 98 wt%.

When the amount of the coated metal particles is less than 30% by weight, the magnetic properties are insufficient. On the other hand, when the amount is more than 98% by weight, the molding becomes difficult in any case, which makes practical use difficult.

[0024]

FIG. 1A is a sectional view showing a metal particle used in the present invention. 1 is a metal particle,
2 is a dielectric layer formed on the surface. The coated metal particles are produced by a spray pyrolysis method. The spray pyrolysis method is performed using an apparatus as shown in FIG. That is, a spray nozzle 6 connected to the introduction pipe 5 of the solution to be sprayed is arranged at the upper end of the furnace tube 4 having the heating device 3 outside. A guide cylinder 8 connected to a carrier gas introduction pipe 7 is concentrically arranged around the nozzle 6.
At the lower end of the furnace core tube 4, a storage unit 9 for manufacturing particles is provided.

In this apparatus, a solution containing a metal salt and a salt for forming a dielectric substance is sprayed from the nozzle 6, and at the same time, a carrier gas having characteristics such as oxidizing or reducing properties flows out of the guide cylinder 8. While forming, the coated metal particles are formed in the furnace tube 4.

As the material of the metal particles, nickel, iron, or iron and another metal (nickel, molybdenum, silicon, aluminum, cobalt,
Neodymium, platinum, samarium, zinc, boron, copper, bismuth, chromium, and the like) are used. In the case of making this alloy,
Each metal salt is introduced into the furnace tube 4.

As a material for forming the dielectric layer 2, for example, silicon, boron, phosphorus,
Tin, zinc, bismuth, alkali metal, alkaline earth metal, germanium, copper, zinc, aluminum, titanium,
Zirconium, vanadium, niobium, tantalum, chromium, manganese, tungsten, iron, chromium, cobalt,
There is an oxide containing at least one kind of element such as a rare earth metal and molybdenum.

The dielectric layer 2 may be formed of a ceramic material having dielectric properties as described below.
That is, titanium-barium-neodymium, titanium-
Barium-tin, lead-calcium, titanium dioxide,
Examples include barium titanate-based, lead titanate-based, strontium titanate-based, calcium titanate-based, bismuth titanate-based, and magnesium titanate-based ceramics. Furthermore, CaWO ₄ system, Ba (Mg, Nb) O
₃ system, Ba (Mg, Ta) O ₃ system, Ba (Co, Mg,
Nb) O ₃ system, Ba (Co, Mg, Ta) O ₃ system and the like.

These ceramics can be used alone or
Alternatively, two or more kinds may be used in combination. The titanium dioxide-based ceramic m is a composition containing only titanium dioxide or a composition containing a small amount of other additives in titanium dioxide, and retains the crystal structure of titanium dioxide as a main component. Is what is being done. The same can be said for other types of ceramics. Titanium dioxide
In substance represented by TiO _2, but those having various crystal structures, those used as the dielectric ceramics,
It has a rutile structure.

The types of salts for forming the metal particles 1 and the dielectric layer 2 include nitrates, sulfates, oxynitrates, and the like.
Oxysulfate, chloride, ammonium complex, phosphate,
Carboxylate, metal alcoholate, resinate, boric acid,
One or more kinds of thermally decomposable compounds such as silicic acid are used.

These compounds such as salts are dissolved in water, an organic solvent such as alcohol, acetone and ether, or a mixture thereof. The heating temperature set by the heating device 3 is higher than the melting temperature of the metal particles 1.

FIG. 2 is a process chart showing an example of a method for manufacturing a feed-through EMI filter according to the present invention. As shown in FIG. 2 (A), the dielectric coated metal particles 1 produced by the spray pyrolysis method are mixed with a resin 1 by using a twin screw extruder or the like.
The composite magnetic material 11 shown in FIG. Here, as the resin 10, both a thermosetting resin and a thermoplastic resin can be used, and an epoxy resin, a phenol resin, a polyolefin resin, a polyimide resin, a polyester resin, a polyphenylene oxide resin, a melamine resin, and a cyanate ester-based resin are used. , At least one of diallyl phthalate resin, polyvinyl benzyl ether resin, liquid crystal polymer, fluororesin, polyvinyl butyral resin, polyvinyl alcohol resin, ethyl cellulose resin, nitrocellulose resin, and acrylic resin used alone or in combination it can.

Next, the composite magnetic material 11 is shown in FIG.
Into pellets 12 as shown in FIG. Subsequently, as shown in FIG. 2D, the composite magnetic body 13 is molded into a predetermined cylindrical shape by various molding methods such as injection molding. Thereafter, the inner and outer peripheries and the end faces of the cylinder are plated and cut so that both end faces are removed by cutting.
As shown in (E), a conductor 1 such as copper by plating on the inner and outer circumferences
A composite magnetic body 13 having 4 and 15 is obtained. Next, FIG.
As shown in (F), a metal rod 16 as a central conductor made of solder-plated brass or the like that matches the inner diameter of the composite magnetic body 13 is inserted, the solder is melted, and connected to the conductor 14 on the inner wall by the solder. And complete it.

FIG. 3A is a cross-sectional view showing a through-type EMI filter manufactured as described above, FIG. 3B is a perspective view thereof, and FIG. 3C is an equivalent circuit diagram thereof. FIG. 3 (A),
As shown in (B), the metal rod 16 is fixed as a center conductor to the metal 14 on the inner periphery of the cylindrical composite magnetic body 13 by soldering, and the conductor 15 on the outer periphery of the composite magnetic body 13 is configured as an external conductor. . As shown in FIG.
The I filter is represented as a T-type filter circuit including an inductor L and a capacitor C.

As described above, the structure in which the cylindrical composite magnetic body 13 is provided on the outer periphery of the center conductor 16 and the outer conductor 15 is provided on the outer periphery is obtained by coating or molding around the center conductor 16. By forming the composite magnetic body 13 and forming the external conductor 15 around the composite magnetic body 13 by coating or the like.

The composite magnetic material used in the present invention is:
It is made by dispersing and mixing circular magnetic metal particles covered with a dielectric layer in a resin, and is a piece of flakes or a block with irregularities, which is made by crushing a sintered dielectric as in the past. Because it is spherical and small in diameter compared to
Good dispersibility when mixed into resin. In addition, the composite magnetic material disperses the coated magnetic metal particles in a resin, maintains a circular shape even in a state where the composite magnetic material is formed, and holds the dielectric layer. Thus, even with an addition amount of, for example, 1 wt%, the insulation resistance and withstand voltage of the composite magnetic material can be improved. Therefore, a highly reliable filter having high insulation resistance and withstand voltage can be provided. Further, since the surface of the metal particles is covered with the dielectric layer, there is no problem of corrosion such as rust.

Since the metal particles 1 have a small diameter and the surface is covered with a dielectric layer, the eddy current loss, which is one of the losses as a magnetic material, is a composite magnetic material using metal particles. And high-frequency characteristics are improved. Also,
Since the surface of the metal particles 1 is covered by the dielectric layer 2, a desired attenuation can be easily obtained in a high frequency band exceeding GHz, and a noise removing effect can be obtained.

FIG. 4 is a view showing an example of a manufacturing process of a prepreg used for manufacturing a penetration type EMI filter according to the present invention. The method of FIG. 4 is relatively suitable for mass production, and the method of FIG. 4 has features that the film thickness can be easily controlled and the characteristics can be adjusted relatively easily. In FIG.
As shown in (A), the coated metal particles 1, resin 17 and solvent 18 such as toluene and benzene are mixed in a stirrer 19 to prepare a slurry. On the other hand, as shown in FIG. 4 (B), the glass cloth 20 wound in a roll shape is unwound from the roll, and is conveyed to a coating tank 22 via a guide roller 21. The slurry is filled in the coating tank 22, and when the glass cloth passes through the coating tank 22, the glass cloth is immersed in the slurry, coated on the glass cloth, and filled in the gap. Will be done.

The glass cloth that has passed through the coating tank 22 is introduced into a drying furnace 25 via a guide roller 23. The glass cloth impregnated with the composite dielectric material or the composite magnetic material introduced into the drying oven is dried at a predetermined temperature and for a predetermined time, and is wound around the winding roller 26.

Then, as shown in FIG. 4C, when cut into a predetermined size by the cutter 27, a prepreg in which the composite magnetic material is disposed on both surfaces of the glass cloth is obtained.

Further, as shown in FIG. 4 (D), a metal foil 30 such as a copper foil is placed on the upper and lower surfaces of one or more of the obtained prepregs 29, and this is heated and pressed.
A substrate 31 with double-sided metal foil 30 as shown in FIG.

Here, in the heating and pressurizing of FIG. 4D, the heating and pressurizing conditions are a temperature of 100 to 200 ° C., 9.8 ×
The pressure may be set to 10 ^{5 to} 7.84 × 10 ⁶ Pa (10 to 80 kgf / cm ² ), and it is preferable to perform molding under such conditions for about 0.5 to 20 hours. The molding can be performed in a plurality of stages under different conditions. In the case where no metal foil is provided, heating and pressing may be performed without disposing the metal foil.

Next, an example of a process for obtaining a through-type EMI filter with a laminated structure from a substrate 31 with a metal foil made of the above-mentioned composite magnetic material containing glass cloth and a prepreg will be described with reference to FIG. From the substrate 31 shown in FIG. 5 (A), the central conductor 3 is formed on a metal foil on one side by patterning comprising photolithography and etching.
2 is formed. FIG. 6A shows the pattern of the center conductor 32. At both ends of the central conductor 32, lead portions 32a are formed. Also, a pattern to be the external conductor 33 (see FIG. 6C) is formed on the other surface side. The thickness of the substrate 31 in FIGS. 5A and 5B is about 400 μm.
m.

Next, as shown in FIG. 5C, a prepreg 29 having a thickness of about 400 μm made of a composite magnetic material containing glass cloth is superimposed on the surface on which the central conductor 32 is formed.
Further, a metal foil such as copper serving as the external conductor 34 is laminated thereon and thermocompression-bonded. Further, patterning of the external conductor 34 is performed.

Thereafter, as shown in FIG. 5D, a through-hole 36 is formed in a portion sandwiched between the center conductors 32, and a plating 37 is formed in the through-hole 36 as shown in FIG.
Is applied. The plating 37 is performed, for example, by forming a nickel layer on a copper layer and then forming a gold layer on the nickel layer. By cutting into individual chips along the center of the through hole 36, the upper and lower external conductors 34, 33 are connected to the through hole 36 as shown in FIG.
It is connected by the inner plating conductor 37. As shown in FIG. 6C, the composite magnetic body 29A (a prepreg heating and pressing body)
Are provided with terminal electrodes 40 connected to both ends of the central conductor 32.

As shown in FIG. 6B, in the filter, a composite magnetic body 29 covering the center conductor 32 and its periphery is provided.
A constitutes an inductance component L shown in FIG. 3C, and a through-type low-profile EMI filter in which a capacitance is formed between the center conductor 32 and the upper and lower conductors 34 and 33 in a distributed capacitance manner. Is obtained.

Since the composite magnetic material according to the present invention covers the small-diameter magnetic metal particles 1 with the dielectric layer 2, it can have high insulation properties and a high dielectric constant, and can be used in a thin surface mount suitable for use. A type of feed-through EMI filter can be realized.

(Example 1: Through-type EMI filter 1) In order to obtain metal particles coated with a dielectric layer, a spray pyrolysis method was used to deposit BaTiO ₃ on the surface using iron as an internal metal. The deposited BaTiO ₃ layer was blended so that the weight ratio of BaTiO ₃ to iron was 10 wt%. X-ray diffraction confirmed that the completed metal particles were iron and BaTiO ₃ . The particle size distribution is 0.1 to 1.3 μm, and the average particle size is 0.1 to 1.3 μm.
It was 6 μm.

As shown in FIG. 2, the barium titanate-coated iron powder 1 and the liquid crystal polymer 10 were extruded by a twin screw extruder.
(Toray's Siveras) was kneaded to obtain a kneaded material 11,
The kneaded product 12 in the form of a pellet was finely pulverized, and the kneaded product 12 was subjected to an injection molding machine to obtain a molded product 13 formed into a pipe shape by using a mold that was processed into a cylindrical shape. The relative permittivity of the molded product 13 was 15.5. The relative permittivity of the composite magnetic body 13 is about 30% higher than that of a composite magnetic body made of resin and iron particles having no dielectric layer as in a comparative example described later. . The composite magnetic body 1
The size of 3 is outer diameter 7mm, inner diameter 3mm, length 20mm
And

Next, metal plating was applied to the entire surface of the pipe-shaped composite magnetic body 13. The plating at this time was a three-layer plating of copper, nickel and gold. This is 5m
m, and the inner circumference, as shown in FIG.
A composite magnetic body 13 having conductors 14 and 15 on the outer periphery was obtained.

Next, as shown in FIG. 2 (F), a brass metal rod 16 plated with solder was inserted, and the solder was melted to fix the metal rod 16 serving as a central conductor to the conductor 14. As described above, the finished product has the structure shown in FIGS. The attenuation characteristics of the completed product were measured by a network analyzer HP8510.

(Comparative Example 1: Through-type EMI filter) A through-type EMI filter was manufactured in the same manner as in Example 1 above using iron powder (carbonyl iron: SQ manufactured by BASF) whose surface was not coated, and the attenuation was obtained. Characteristics were measured with a network analyzer as described above. The relative dielectric constant of the composite magnetic body using the iron powder without the dielectric layer coating was 12.

(Comparison of Characteristics) FIG. 3 (D) shows the frequency characteristics of the attenuation (insertion loss) of Example 1 and Comparative Example 1 in comparison. As can be seen from FIG. 3D, in the case of Example 1, a higher dielectric constant than that of Comparative Example 1 is obtained as the composite magnetic body 13, so that a higher attenuation than that of Comparative Example 1 is obtained in a high frequency band exceeding 1 GHz. Can be

(Embodiment 2: Surface mount type penetration type EMI)
Filter) The same metal particles 1 as in Example 1 were used for the dielectric layer-coated metal particles, and an epoxy resin was used as the resin, the iron powder content was 80 wt%, and a slurry was prepared using toluene as a solvent. The slurry was applied to a glass cloth by the process shown in FIG. 4 to produce a prepreg.

The epoxy resin used for preparing the slurry contained 26.9% by weight of an epibis epoxy resin (Epicoat 1001 and Epicoat 1007 manufactured by Yuka Shell Epoxy Co., Ltd.) as a polyfunctional epoxy resin. A type polymer epoxy resin (Epicoat 1225 manufactured by Yuka Shell Epoxy)
As an epoxy resin having a special skeleton, 23.1% by weight of a tetraphenylolethane type epoxy resin (Epicoat 1031S manufactured by Yuka Shell Epoxy Co., Ltd.) as a main component, and a bisphenol A type novolak resin as a curing agent ( Yuka Shell Epoxy YLH129
B65) and an imidazole compound (2E4MZ manufactured by Shikoku Chemicals) as a curing accelerator were dissolved in toluene and methyl ethyl ketone, and the dielectric-coated iron particles were dispersed and mixed by a ball mill.

The heat treatment conditions until the prepreg was semi-cured were 100 ° C. for 2 hours. Further, the glass cloth may be any of H glass, E glass, and D glass, and may be properly used depending on required characteristics.
In the examples, E glass was used. In addition, the thickness may be appropriately determined according to the request, and in the examples, the thickness is 100 μm.

A predetermined number of the semi-cured products obtained by the above steps were stacked, and a composite magnetic substrate having a thickness of about 0.4 mm was formed by applying copper foil on both sides by pressing and heating. This substrate was patterned using a photolithography technique as performed on a normal printed circuit board, as shown in FIG. Thereafter, the thickness of the prepreg was adjusted to about 400 μm, and the prepreg was adhered to the upper surface of the pattern together with the copper foil by pressing and heating, and was cured. Thereafter, connection and terminal electrode formation were performed by through-hole processing and plating. Further, upper and lower ground electrodes were formed by the same photolithography technique as described above. Thus, a chip as shown in FIGS. 6B and 6C was manufactured.
In this case, the shape of the chip is 2.0 mm long and 1.times.
The pattern was formed and processed to have a height of 25 mm and a height of 0.85 mm.

The attenuation characteristics of the filter thus manufactured were measured using the same network analyzer as described above. FIG. 7A shows the measurement results.

(Comparative Example 2: Laminated sintered type penetration type EM)
I filter) Using a conventional green sheet method, disperse the calcined ferrite particles with a predetermined resin and solvent.
After mixing, molded into a sheet by the doctor blade method, after printing the electrode pattern with silver paste, the number, order is set and laminated so that the target structure is obtained, then, by heating, pressure press Crimped. Furthermore, the product was cut into product dimensions by cutting, then fired, provided with external electrodes, and plated to obtain a finished product.

FIGS. 6D and 6F show the cross-sectional structure and appearance of Comparative Example 2. In the figures, reference numeral 41 denotes a sintered body made of ferrite, 42 denotes a center conductor, and 43 and 44 sandwich a center conductor. The external conductor provided as described above. Both ends of the central conductor 42 are connected to terminal electrodes 46, 46, and the outer conductors 43, 44 are connected to terminal electrodes 45, 45 on the side surfaces.

(Characteristic Comparison) FIG. 7A shows the frequency characteristic of the attenuation in the second embodiment, and FIG. 7B shows the frequency characteristic of the attenuation in the second embodiment. As can be seen from FIGS. 7A and 7B, according to the present invention, a large amount of attenuation can be obtained up to a high frequency band.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of particles used in the present invention,
(B) is a configuration diagram showing an example of an apparatus used for generating particles by spray pyrolysis in the present invention.

FIG. 2 is a diagram illustrating an outline of an example of a manufacturing process according to the first embodiment of the present invention.

3A is a sectional view of Example 1 of the present invention, FIG. 3B is its perspective view, FIG. 3C is its equivalent circuit diagram, and FIG. 3D is the insertion loss of Example 1 and Comparative Example 1. It is a frequency characteristic figure.

FIG. 4 is a diagram showing an outline of an example of a manufacturing process of a material of Example 2 of the present invention.

FIG. 5 is a diagram illustrating an outline of an example of a manufacturing process according to a second embodiment of the present invention.

6A is a plan view showing a pattern of a center conductor according to a second embodiment of the present invention, FIG. 6B is a cross-sectional view thereof, and FIG. 6C is a perspective view thereof.

FIGS. 7A and 7B are Example 2 and Comparative Example 2, respectively.
FIG. 4 is a frequency characteristic diagram of the attenuation amount of FIG.

[Explanation of symbols]

1: metal particles, 2: dielectric layer, 3: heating device, 4: furnace tube, 5: solution introduction tube, 6: spray nozzle, 7: carrier gas introduction tube, 8: guide tube, 9: production particles Accommodation section, 1
0: resin, 11: composite magnetic material, 12: pellet, 1
3: composite magnetic material, 14: inner conductor, 15: outer conductor, 1
6: metal rod (center conductor), 17: resin, 18: solvent, 1
9: stirrer, 20: glass cloth, 22: coating tank, 2
5: drying oven, 26: winding roller, 27: cutter, 29:
Prepreg, 29A: composite magnetic material, 30: metal foil, 3
1: substrate, 32: center conductor, 33, 34: outer conductor, 3
6: through hole, 37: plated conductor, 40: terminal electrode

Continuation of front page (72) Inventor Heng Kosara 1-13-1, Nihonbashi, Chuo-ku, Tokyo T-D Corporation F-term (reference) AB01 BA12 BA16 CB03 CB12 EA01 EA05 5E082 AB08 BB01 BB05 BC14 BC39 DD07 DD08 EE05 EE11 EE23 EE39 FF05 FF13 FG13 FG22 FG25 FG26 FG52 FG56 GG10 GG28 KK08 LL15 PP03 PP09

Claims (5)

[Claims] 1. A mixture of magnetic particles having an average particle diameter of 0.1 to 10 μm, in which all or a part of the surface of spherical magnetic metal particles which become substantially a single crystal are coated with a dielectric layer, and a resin material. A through-type EMI filter, comprising: a composite magnetic material comprising: a cylindrical composite magnetic body made of the composite magnetic material around a central conductor; and an external conductor on an outer peripheral portion of the composite magnetic material. 2. A composite of a resin material and a magnetic particle having an average particle diameter of 0.1 to 10 μm, in which all or a part of the surface of a substantially single crystal spherical magnetic metal particle is coated with a dielectric layer. Using a glass cloth-clad metal-clad substrate and a prepreg made of a magnetic material, the laminated structure of the glass-cloth-clad metal-clad substrate and the prepreg is formed so that external electrodes face each other above and below the center conductor via a composite magnetic material. A piercing type EMI filter characterized by the above-mentioned. 3. The penetration type EMI filter according to claim 1, wherein a dielectric constant of a dielectric layer on a surface of said magnetic metal particles is higher than a dielectric constant of said resin. 4. A penetration type E according to any one of claims 1 to 3.
In the MI filter, the thickness of the dielectric layer is 0.005 μm to 5 μm. 5. A penetration type E according to any one of claims 1 to 4.
A penetration type EMI filter, wherein the coated metal particles are mixed in a resin of 30 to 98 wt% in an MI filter.