JP2002076667A - Electromagnetic wave shielding structure and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding structure which is excellent in electromagnetic wave shielding property and durability, can be mass-produced, and can obtain a degree of freedom for design and to provide a method of manufacturing the structure. SOLUTION: In the electromagnetic wave shielding structure which shields the electromagnetic waves generated from electronic equipment by using shielding cases, wiring boards 3, etc., a plurality of discontinuous rubber-made elastic members 6 is formed on at least one joint surface of combined shielding cases or wiring boards 3 and conductive films 7 are formed on the joint surfaces of the shielding cases or wiring boards 3 including the elastic members 6. Then the shielding cases, shielding cases and wiring boards 3, or wiring boards 3 are joined to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shield structure of an electronic circuit element or an electronic device such as a computer using the same, and a method of manufacturing the same. In particular, the present invention is effective as an electromagnetic wave shield structure of a small communication device such as a portable telephone. is there.

[0002]

2. Description of the Related Art A high-frequency circuit portion and a logic circuit portion of a printed wiring board on which electronic circuits such as semiconductor chips such as ICs and LSI chips are mounted require an electromagnetic wave shield, and the printed wiring board is stored in a conductive shield case. And
The electronic circuit device is mounted on various electronic devices such as a small portable communication device while containing the electronic circuit element.

[0003] As a conventional shield case, one having a structure combining two upper and lower cases is well known. For example, a conductive solid gasket is mounted between the upper and lower case joints and fixed with screws, or a plate spring is soldered to the ground pattern on the printed circuit board, and the case and the printed circuit board are fitted. Fixing had been done. Further, Japanese Patent Application Laid-Open No. Hei 9-13076 discloses an example in which conductive ink is used instead of the solid gasket to electrically connect the cases. The electrical connection between the upper and lower cases prevents leakage of electromagnetic waves from inside the case and entry from outside.

[0004]

However, when the above-described solid gasket is used, the material cost is high, it is difficult to cope with a complicated shape, and it is difficult to automatically load the material. There was a problem. If the leaf spring is soldered, the cost of the spring material is high,
Also, increasing the number of installations to obtain a sufficient shielding effect will increase weight and cost, and when it is necessary to change the installation interval according to the frequency to be shielded, the installation space is relatively large. It was necessary to redo the design because it was necessary, and it was difficult to respond.

In order to solve these problems, as described in Japanese Patent Application Laid-Open No. Hei 9-13076, a conductive ink is applied in a bead shape and cured to form a contact, and the case is fixed by a minimum number of joints. It has been proposed to use screws, but in this case, unevenness is likely to occur on the surface of the formed continuous bead-shaped conductive material. There is a problem that a portion is easily generated, and the electromagnetic wave shielding performance deteriorates.

Accordingly, an object of the present invention is to solve the above-mentioned problems, and in particular, to provide an electromagnetic wave shielding structure which is excellent in electromagnetic wave shielding performance and durability, maintains mass productivity, and has a degree of design freedom, and a method of manufacturing the same. The purpose is to provide.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an electromagnetic wave shielding structure for shielding an electronic device that generates electromagnetic waves from electromagnetic waves by using a shield case, a wiring board, or the like. Forming a plurality of discontinuous rubber elastic members, and then forming a conductive film on the joint surface of the shield case or the wiring board including the rubber elastic member, between the shield cases, or between the shield case and the wiring board, Alternatively, the above-mentioned problem is solved by joining the wiring boards.

With the above-described structure, the present invention provides a rubber elastic member and a conductive film with an appropriate gap between the joint surface between the shield case and the wiring board, the joint surface between the shield cases, or the joint surface between the wiring boards. Since they are electrically connected via the connection surface, leakage of electromagnetic waves from inside the joint surface can be prevented, and the electronic circuit elements housed in the case are effectively shielded from harmful electromagnetic waves from outside. In addition, when a rubber elastic body is formed, if a liquid curable resin composition or a liquid rubber composition is used, automatic application using a dispenser is also possible, which is excellent in mass productivity, reduced in cost, and reduced in weight and thickness. It is extremely effective and can easily respond to design changes.

According to the present invention, a conductive film formed on a shield case or the like including a rubber elastic member is formed on a mating joint surface (shield case or wiring board) by utilizing a repulsive force generated by deformation of the rubber elastic body. The bonding surfaces are electrically connected to each other by being pressed against the conductor. The rubber elastic member used here may have rubber elasticity when formed on the bonding surface of the shield case or the wiring board. The material of the material itself is not particularly limited. The rubber elasticity as referred to herein is desirably 60 or less, preferably 40 or less as measured by a Shore A hardness meter. The rubber elastic member of the present invention is a synthetic rubber,
A rubber elastic material such as a natural rubber, an acrylic resin, an epoxy resin, a urethane resin, a silicone resin, a modified silicone resin, or a butadiene resin may be bonded to the bonding surface with an adhesive or the like. Alternatively, a liquid, putty-like or grease-like composition may be applied to the bonding surface and solidified or cured to directly form a rubber elastic material. In consideration of easiness of operation and mass productivity, it is preferable to use the latter, that is, a liquid that can be used for an automatic coating apparatus or a composition having properties similar to the liquid. Examples of the liquid or a composition having properties similar thereto include an epoxy resin, a urethane resin, a silicone resin, a modified silicone resin, an acrylic resin, and a butadiene resin, which are polymerized and cured by exposure to moisture, heat, ultraviolet light, or the like. And the like, or a solvent-evaporable liquid composition in which a synthetic resin or synthetic rubber is dissolved or dispersed in an organic solvent. In consideration of workability and environmental issues among these, a polymer-curable composition containing almost no solvent is preferable, and particularly, a urethane-based composition that shows good rubber elasticity and has little outgas and little influence on electronic components, Modified silicone and butadiene resins and rubbers are particularly preferred.

Further, this rubber elastic composition is usually non-conductive, but a conductive or semi-conductive rubber elastic material can be obtained by mixing a conductive filler into the rubber elastic composition. Specifically, for example, gold, silver, copper, nickel, or the like is added to the above-described liquid or a composition having properties similar thereto (epoxy resin, urethane resin, silicone resin, modified silicone resin, acrylic resin, etc.). It can be obtained by adding a metal or a metal alloy thereof into fine powder, or adding a conductive filler coated with metal plating or the like to carbon powder or fine plastic particles. In addition,
Providing the rubber elastic member with conductivity is advantageous in terms of conductivity, but since the rubber elastic member becomes hard or loses its elasticity with the passage of time, the resin component to be mixed and the conductive material are not conductive. It is preferable to check compatibility with the filler in advance.

Further, the formed rubber elastic member can be formed in an arbitrary shape, an arbitrary number, and an arbitrary thickness on the joint surface of the shield case or the wiring board, and there is no particular range. However, in general, the shape is 0.5 to 5 m in diameter.
m, it is preferably a dot having a height of 0.1 to 2 mm, but it is also possible to partially combine a beat-shaped rubber elastic member having a width of 3 mm or less, a length of 1 to 20 mm, and a height of 0.1 to 2 mm. it can. Further, it is preferable that the interval (discontinuous portion) between the rubber elastic members is 1.0 to 20 mm. However, the wavelength of the electromagnetic wave to be shielded by the object to be manufactured, its intensity, and the type of the electronic component incorporated therein Since they are different from each other, they can be set arbitrarily by designing according to this.

Next, the conductive film formed on the shield case and the wiring board will be described. The conductive film is formed on the joint surface including the rubber elastic member after the rubber elastic member described above is formed on the joint surface of the shield case or the wiring board. It may be formed by a plating method, a method of applying a conductive paint, or a vapor deposition method, and is not limited to these methods. For example, in the case of forming a conductive film by a plating method, after masking a portion other than a necessary portion where the conductive film is formed on the bonding surface, the surface is roughened, and then a catalyst for bonding the plating is applied. Thereafter, it can be formed by a method of performing metal plating such as electroless copper, electroless nickel, and electroless tin. At this time, it is preferable to use electroless copper for the lower layer and electroless nickel for the surface layer. In addition, in order to form by a method of applying a conductive paint (conductive ink), a conductive paint obtained by dispersing a conductive filler in an epoxy resin, a silicone resin, a urethane resin, or the like is used. The conductive film may be formed by applying and curing after application. Further, in the formation method by vapor deposition, the mask can be formed by masking portions other than necessary portions in the same manner as the plating method, and then performing vapor deposition of copper or nickel by PVD.

Since the conductive film also needs to expand and contract in accordance with the deformation of the rubber elastic member, it is preferable to use a conductive paint which easily imparts elasticity to the conductive film among the above-mentioned methods. Among the conductive paints, particularly preferred are conductive paints which use a silicone resin, a modified silicone resin, or a urethane resin as a binder resin, and to which a conductive filler such as silver, copper, nickel, or carbon is added.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to embodiments. The following embodiments are merely illustrative of one embodiment of the present invention and are not intended to be limiting. FIG. 1 shows an electromagnetic wave shield structure of the present invention, which is composed of an electronic circuit board 1 on which electronic circuit elements are mounted and a pair of upper and lower plastic cases 2a and 2b for housing the circuit board, which are disassembled into components. Have been. First, the plastic cases 2a, 2a
After forming a plurality of point-like rubber elastic bodies 6 on a part of the joint surface between the electronic circuit board 1 and the electronic circuit board 1, all the opposing inner surfaces of the plastic cases 2 a and 2 b including the rubber elastic bodies are electrically conductive paint or non-conductive. It is formed as an electromagnetic wave shielding layer (conductive film) 7 by coating with electrolytic metal plating or the like. The electronic circuit board 1 is composed of a circuit board 3 on which a conductive pattern is formed and an electronic circuit element 4 such as an IC or an LSI. A conductive ground pattern 5 for shielding from the ground is formed. Then, the partition plate 8 (projection-like body) inside the case on which the electromagnetic wave shielding layer 7 is formed, the rubber elastic member 6 of the conductive flange portion 10 and the ground pattern 5 of the electronic circuit board 1 are brought into contact with each other to establish conduction. It has become. At this time, the pair of plastic cases 2a and 2b are locked by a plurality of screws, the rubber elastic body 6 is deformed by the tightening pressure, and the repulsive force causes conduction between the plastic case and the electronic circuit board (wiring board). To take.

[0015]

Examples 1 to 9 and Comparative Example 1 Under the conditions shown in Table 1, 3006 manufactured by Three Bond Co., Ltd. was used as the rubber elastic member 6.
B (polybutadiene-modified photocurable resin), 3014 manufactured by Three Bond Co., Ltd. (urethane-modified photocurable resin),
And about 3 mm in diameter and about 0.5 m in height and about 3 mm in diameter using three types of 33A-519 (composition of metal powder as a conductive material in a urethane-based thermosetting resin) manufactured by Three Bond Co., Ltd.
An m-point rubber elastic member was formed on each of the flange portions and the partition plate of the pair of upper and lower plastic cases by light curing or heat curing. Next, an electromagnetic wave shielding layer (conductive film) was formed on the entire inner surface of the upper and lower plastic cases (including the surface of the rubber elastic member) by conductive paint or electroless metal plating.

Next, the pair of upper and lower plastic cases are assembled at intervals shown in Table 1 so as to sandwich the electronic circuit board on which the conductive ground pattern 5 is formed on the front and back sides, and this is formed between the shield cases. To create an electromagnetic shielding structure. Table 2 shows the results obtained by measuring the electromagnetic wave shielding performance. In addition, a comparative example was used when a metal spring was used.

[0017]

[Table 1]

The following symbols in the table mean the following. * 1: 3006B manufactured by ThreeBond (a photocurable acrylic resin having a polybutadiene structure in the main chain and having a reactive (meth) acrylate group at the terminal or side chain) * 2: 3014 (manufactured by ThreeBond) Photocurable acrylic resin having a urethane structure and having a reactive (meth) acrylate group at a terminal or a side chain) * 3: 33A-519 manufactured by ThreeBond Co., Ltd. (metal powder as conductive material for urethane-based thermosetting resin) * 4: 3350 (those obtained by dissolving an acrylic thermoplastic resin in a solvent and blending silver powder as a conductive material) made by Three Bond Co., Ltd. was formed by spray coating. * 5: Approximately 2 μm after catalyzing the inner surface of the shield case
And electroless nickel plating of about 0.2 μm were sequentially laminated.

Table 2

From the results shown in Table 2, it can be seen that the present invention has performance equal to or higher than that of the conventional electromagnetic wave shielding structure using a metal spring. Further, it can be seen that both conductive paint and electroless plating can be sufficiently used as an electromagnetic wave shielding material.

[0021]

As described above, the joint surface between the shield case and the wiring board (circuit board), the shield cases,
Alternatively, since the joining surfaces of the wiring boards are joined at an appropriate interval via the rubber elastic member and the conductive film, leakage of the electromagnetic wave from the joining surface can be prevented, and the electronic components housed in the case can be prevented. The circuit elements are effectively shielded from the electromagnetic waves. Further, since the rubber elastic member can be formed by automatic coating using a dispenser, it is excellent in mass productivity, and is extremely effective in cost reduction, weight reduction and thickness reduction. further,
The rubber elastic member formed on the joint surface can be freely set by the dispenser application, such as its application position and application amount.
For example, it is possible to easily arrange the shape of the joint surface or change the electronic components to be arranged easily by changing the design, for example, by placing the electromagnetic wave shield in a place where the electromagnetic wave shield is required.

Further, when the rubber elastic member formed on the joint surface has a point shape, the contact area is small, and even when the pressing load is small, the rubber elastic member is easily deformed and the contact ratio of the conductive member is kept high. An electromagnetic wave shielding effect can be effectively exhibited.

[Brief description of the drawings]

FIG. 1 is an overall exploded view showing a shield structure of the present invention.

FIG. 2 is an exploded view and a sectional view showing a shield structure of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electronic circuit board 2a, b Shield case 3 Circuit board 4 Electronic circuit element 5 Ground pattern 6 Conductive elastic body 7 Electromagnetic wave shielding layer 8 Conductive partition plate 9 Screw 10 Flange part

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Atsutoshi Tanaka 306 Higashisakayacho, Miyoshi-shi, Hiroshima F-term (reference) 4F006 AA04 AA22 AA37 AA42 AB73 BA07 DA01 5E321 AA02 AA03 AA14 AA17 BB23 BB24 BB25 CC03 CC09 CC22 GG05

Claims (10)

[Claims] An electromagnetic wave shielding structure for shielding an electronic device that generates an electromagnetic wave from electromagnetic waves using a shield case or a wiring board or the like, wherein a plurality of discontinuous rubber elastic members are provided on at least one joint surface of the combined shield case or wiring board. After forming a member and then forming a conductive film on the joint surface of the shield case or wiring board including the rubber elastic member, joining the shield cases, or the shield case and the wiring board, or the wiring boards together Electromagnetic wave shield structure characterized by the following. 2. The electromagnetic wave shielding structure according to claim 1, wherein said rubber elastic member has a Shore A hardness of 60 or less. 3. The electromagnetic wave shielding structure according to claim 1, wherein the rubber elastic member is a synthetic rubber, an acrylic resin or a rubber, a urethane resin or a rubber, a modified silicone resin or a rubber, a silicone resin or a rubber, or a mixture thereof. . 4. The electromagnetic wave shielding structure according to claim 2, wherein the rubber elastic member is formed of a thermosetting and / or photocurable resin or rubber. 5. An interval between said rubber elastic members is provided at an interval of 1/1000 to 1/10 with respect to a wavelength of an electromagnetic wave,
Also, the compressibility of the conductive member is 1 /
2. The electromagnetic wave shielding structure according to claim 1, wherein the number is 2 or less. 6. The electromagnetic wave shielding structure according to claim 1, wherein the conductive film is formed by plating, painting, vapor deposition, or a combination thereof. 7. The electromagnetic wave shielding structure according to claim 6, wherein the conductive film is nickel plating, copper plating, or a laminate thereof. 8. The electromagnetic wave shielding structure according to claim 6, wherein the conductive film is formed of a conductive paint in which conductive particles such as nickel powder, copper powder, and carbon powder are dispersed or dissolved in a paint composition. . 9. The electromagnetic wave shielding structure according to claim 6, wherein said conductive film is formed by vacuum deposition of copper, nickel, aluminum or a mixture thereof. 10. An electromagnetic wave shielding structure for shielding an electronic device that generates an electromagnetic wave from electromagnetic waves using a shield case, a wiring board, or the like, wherein a plurality of discontinuous rubber elastic members are provided on at least one joint surface of the combined shield case or wiring board. After forming a member and then forming a conductive film on the joint surface of the shield case or wiring board including the rubber elastic member, joining the shield cases, or the shield case and the wiring board, or the wiring boards together A method for manufacturing an electromagnetic wave shield, comprising: