JPH11261270A - Shielding case - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shielding case that can respond to higher frequency of electronic appliances, and prevent radiation of electromagnetic noise to the outside and impact of reflected waves to internal parts. SOLUTION: This shielding case has a double structure of an internal layer 5 containing a magnetic body 7 to damp noise and an external layer 6 comprising a conductive body to block and reflect noise. Electromagnetic wave noise radiated from electronic parts inside the shielding case receives noise damping action in the internal layer 5, reflection action toward inside in the external layer 6, and resumed damping action of reflected waves in the internal layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shield case for preventing the occurrence of noise in a high-density mounting board circuit, and more particularly to a shield case capable of coping with a high frequency in a computer, a portable information device, a mobile communication device and the like. The present invention relates to a shield case having an occurrence preventing function.

[0002]

2. Description of the Related Art As a conventional noise countermeasure in electronic equipment, the following (1) and (2) have been used. (1) A ferrite bead or core having a large impedance effect in a high-frequency region is generally used as a noise absorbing element, and is used by, for example, attaching it to a terminal of an electronic component. (2) As a case that covers the electronic circuit, a case having conductivity such as metal is used to prevent radiation of electromagnetic noise generated in the electronic component to the outside. (3) Ferrite powder is mixed into a mold resin of an electronic circuit (Japanese Patent Laid-Open No. 2-109352, Japanese Patent Laid-Open No. 2-23)
No. 0675) or a case in which a resin is mixed is put on an electronic component (Japanese Patent Application Laid-Open No. 61-163611).

[0003]

The operating frequency of a personal computer or the like is remarkably increased to 300 MHz.
Operating frequency exceeding 1 GHz
Operating frequencies up to z are also planned. By increasing the operating frequency, electromagnetic noise is more likely to occur in the CPU and the like than in the conventional case. In addition, the number of bits that can be processed in one clock is also increasing.
Further, electromagnetic wave noise is easily generated.

The electromagnetic noise generated by the CPU IC is
Leakage to the outside may cause other electronic components to malfunction. It is also planned to mount a memory element on the same substrate as the CPU for miniaturization.

[0005] When a conventional noise suppression component is examined against such a background, no satisfactory product can be obtained with the conventional product for the following reasons. First, since the ferrite beads and the like described in the above (1) do not cover the entire electronic circuit, an effect of reducing electromagnetic wave noise to space due to recent digitization cannot be expected. Further, it is known that a material using a magnetic material such as ferrite cannot obtain a sufficient noise removing effect exceeding 1 GHz or several GHz.

On the other hand, when the case made of metal or the like described in (2) is placed over the electronic circuit, the radiation of electromagnetic wave noise to the external circuit can be prevented, but the reflected wave reflected on the inner surface of the case does not. This may affect other elements housed in the device and cause the elements to malfunction. In particular, as described above, when a CPU and another functional element such as a memory element are mounted on the same substrate, electromagnetic wave noise generated by the CPU may be reflected on a metal case and cause other functional elements on the substrate to malfunction.

Further, in the case of (3) in which ferrite powder is mixed into the mold resin or in the case where a shield case is formed by mixing ferrite powder, it is difficult to completely attenuate the noise. In order to prevent complete radiation to the outside, the weight and size of the mold resin and the case must be increased, which is not practical. Therefore, there is a possibility that electromagnetic wave noise leaking to the outside may affect other electronic circuits and electronic devices.

In view of the above-mentioned problems, the present invention can cope with the recent increase in the frequency of electronic equipment, can sufficiently prevent the radiation of electromagnetic wave noise to the outside, and can reduce the noise from the source of electromagnetic wave noise. It is an object of the present invention to provide a shield case having a structure in which the electromagnetic wave noise is not reflected on the inner surface of the case and adversely affects other elements housed in the same case.

[0009]

According to a first aspect of the present invention, there is provided a shield case having a double structure of an inner layer containing a magnetic material for attenuating noise and an outer layer made of a conductor for blocking and reflecting noise. I do.

According to a second aspect of the present invention, in the shield case, the inner layer is formed by mixing magnetic metal powder or ferrite powder in a resin.

According to a third aspect of the present invention, the inner layer is formed of a resin molded body, and the outer layer is formed of a metal film formed on the surface of the resin molded body.

[0012]

In the shield case of the present invention, when the electromagnetic noise passes through the inner layer, the electromagnetic noise is attenuated by the magnetic loss due to the magnetic material. In addition, since the electromagnetic wave noise is reflected by the outer layer, leakage of the electromagnetic wave noise to the outside is prevented. The electromagnetic wave noise reflected by the outer layer is attenuated again when passing through the magnetic body again, so that the intensity of the electromagnetic wave noise with respect to the electronic components housed in the shield case is reduced, and malfunction does not occur.

[0013]

FIG. 1 is an exploded perspective view showing an embodiment of a shield case according to the present invention, FIG. 2A is a sectional view of this embodiment, and FIG. FIG. 3 is an EE cross-sectional view, and FIG.

In these figures, 1 is a shield case main body, 2 is a lid thereof, and 3 is a mounting board on which electronic components 4 are mounted. The shield case main body 1 includes an inner layer 5 and an outer layer 6. The inner layer 5 serves as a noise attenuation layer, and is a molded body made of a mixture of the magnetic body 7 and the resin 8 (see FIG. 3).

The outer layer 6 is provided on the outer surface of the inner layer 5 made of a molded body and serves as a noise blocking layer. The outer layer 6 is a film made of a conductive material.
It is integrally fixed to the inner layer by coating or the like.

The mounting substrate 3 is inserted into the shield case main body 1 by fitting both sides into grooves 9 provided on two opposing surfaces of the inner layer 5, and the end face opening of the shield case main body 1 is closed with the lid 2. Is stopped by.

The lid 2 constitutes a noise blocking layer similarly to the outer layer 6, and is made of a conductor such as a metal. The lid 2 is fixed to the shield case body 1 by fitting, bonding, welding or the like. A terminal connection hole 10 for a connector or the like of the mounting board 3 is provided substantially at the center of the lid 2. Around the hole 10, a noise attenuating layer 11 made of a mixture of a resin and a magnetic material is provided to form an electrically insulating structure.

The magnetic material 7 constituting the inner layer 5 includes:
Metal powder or ferrite powder is used. As the metal powder, permalloy, carbonyl iron, or Fe—Si alloy powder is preferable, and as the ferrite powder, spinel-type or magnetoplumbite-type ferrite powder is preferable.
Since these have high magnetic permeability and can generate a large magnetic loss, a high electromagnetic wave noise absorbing effect can be obtained.

The resin 8 constituting the inner layer 5 includes:
A thermosetting resin such as an epoxy-based, phenol-based, or urethane-based resin is desirable. The reason is that when the magnetic material mixed in these resins attenuates noise, it converts this into heat as magnetic loss, so that a thermosetting resin that is highly reliable against heat is suitable. Because.

The inner layer 5 is formed by kneading a mixture having undergone a step of uniformly mixing a resin and a magnetic material with a mixing device by a kneader or the like, and then performing a general molding method such as injection molding or compression molding.

The outer layer 6 and the lid 2 need only have a property of preventing electromagnetic noise from leaking to the outside and reflecting inward, that is, have conductivity, and are not particularly limited in material.
For example, metals such as iron, cobalt, aluminum, nickel, and lead, or general alloys thereof can be used. Further, the thickness of the outer layer 6 may be determined by the skin depth formula if the operating frequency of the electronic device is known.

Next, the operation of the shield case will be described with reference to FIG. Electromagnetic noise A generated in the electronic component 4 of the mounting board 3 is absorbed and attenuated by the magnetic body 7 of the inner layer 5.
Next, the remaining noise B that could not be absorbed is reflected by the outer layer 6 made of a conductive layer, and the reflected noise C is again absorbed by the magnetic body 7 and is attenuated again. By such an action,
Although the noise D toward the electronic component 4 remains, it is almost attenuated, so that the electronic component 4 of the mounting board 3 does not cause a noise disturbance and does not malfunction.

The magnetic material 7 converts the noise into heat as magnetic loss when attenuating the noise. Regarding the influence of the heat on the electronic component 4, the metal is used as the outer layer 6 so that the metal can be used. Since the heat conductivity is high, the heat generated in the inner layer 5 is efficiently released to the outside, so that the electronic component 4 is not adversely affected thermally.

When implementing the present invention, the configuration of the shield case is not limited to the above embodiment. For example, a structure in which resin is integrally molded in a case as the outer layer 6 is also possible. However, as described above, by forming the outer layer 6 as a metal film on the outer surface of the molded body by the above-described means, the outer layer 6 can be formed to a necessary minimum thickness, and the structure can be reduced in weight.

[0025]

The shield case according to the first and second aspects has a double structure of an inner layer containing a magnetic material for attenuating noise and an outer layer made of a conductor for blocking and reflecting noise, so that electromagnetic waves to the outside can be prevented. The radiation of noise can be blocked, and the influence on external electronic components and devices can be eliminated. In addition, the electromagnetic wave noise reflected by the outer layer is attenuated again when passing through the magnetic material again, so that the intensity of the electromagnetic wave noise with respect to the electronic components housed in the shield case is reduced, and the electronic components in the shield case are not affected. No adverse effects. Therefore, even in an electronic device in which electromagnetic noise of a high frequency exceeding 1 GHz is generated, there is no adverse effect on electronic components inside and outside the shield case,
Malfunction can be prevented. Further, the electronic component can be configured to be lighter than a case where the electronic component is molded with resin.

In the shield case according to the third aspect, by using a metal for the outer layer, heat generated by the magnetic material can be effectively radiated to the outside, and there is a possibility that the electronic components in the shield case may be thermally affected. The effect of not being obtained is further obtained. In addition, since the outer layer is integrally formed as a metal film on the outer surface of the molded body, the outer layer can be formed to a necessary minimum thickness, and the shield case can be made lighter.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a shield case according to the present invention.

2A is a cross-sectional view of the present embodiment, and FIG. 2B is a cross-sectional view taken along line EE of FIG.

FIG. 3 is an operation explanatory view of the present embodiment.

[Explanation of symbols]

1: shield case body, 2: lid, 3: mounting board, 4:
Electronic components, 5: inner layer, 6: outer layer, 7: magnetic material, 8: resin, 9: groove, 10: terminal connection hole, 11: noise attenuation layer

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[Procedure amendment]

[Submission date] March 8, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

The shield case according to claim 1 SUMMARY OF THE INVENTION, comprising an inner layer comprising a magnetic material for attenuating noise, the double structure of the outer layer made of a conductor for reflecting blocking noise, the inner layer Means that magnetic metal powder or ferrite powder
A resin molded body mixed in a fat, wherein the outer layer is
It is characterized by being formed of a metal film formed on the surface of the fat molding .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Deleted

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Deleted

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

As described above , by forming the outer layer 6 as a metal film on the outer surface of the molded body by the aforementioned means,
The outer layer 6 can be formed to a minimum necessary thickness, and can be made lightweight.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

[0025]

The shield case according to the present invention has a dual structure of an inner layer containing a magnetic material for attenuating noise and an outer layer made of a conductor for blocking and reflecting noise.
The radiation of electromagnetic wave noise to the outside can be blocked, and the influence on external electronic components and devices can be eliminated. In addition, the electromagnetic wave noise reflected by the outer layer is attenuated again when passing through the magnetic material again, so that the intensity of the electromagnetic wave noise with respect to the electronic components housed in the shield case is reduced, and the electronic components in the shield case are not affected. No adverse effects. Therefore, even in an electronic device in which electromagnetic wave noise of a high frequency exceeding 1 GHz is generated, it is possible to prevent adverse effects on electronic components inside and outside the shield case and prevent malfunction. Further, the electronic component can be configured to be lighter than a case where the electronic component is molded with resin.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction contents]

In the shield case according to the present invention, by using metal for the outer layer, the heat generated by the magnetic material can be effectively radiated to the outside, and the electronic components in the shield case may be thermally affected. The effect that there is no is further obtained. In addition, since the outer layer is integrally formed as a metal film on the outer surface of the molded body, the outer layer can be formed to a necessary minimum thickness, and the shield case can be made lighter.

Claims (3)

[Claims] 1. An inner layer containing a magnetic material for attenuating noise,
A shield case having a double structure with an outer layer made of a conductor that blocks and reflects noise. 2. The shield case according to claim 1, wherein said inner layer is formed by mixing magnetic metal powder or ferrite powder into a resin. 3. The shield case according to claim 1, wherein the inner layer is formed of a resin molded body, and the outer layer is formed of a metal film formed on a surface of the resin molded body.