JPH0758474A - Grounding structure of circuit board in electronic equipment case body - Google Patents

Abstract

PURPOSE:To facilitate grounding of a circuit board equipment mounted to a resin internal mechanism part in an electronic equipment case body, which has a metal outer shell and the resin internal mechanism part formed integrally with this metal outer shell. CONSTITUTION:A circuit board 4 is mounted on a projected stand 3b using a screw 7 for circuit board mounting, which is longer than the distance between the end surface of the projected stand 3b for circuit board 4 mounting of an internal mechanism part 3 formed integrally with a metal outer shell 1 by adhesion via a bonding agent layer 2 and the outer surface of the layer 2 and is shorter by a nominal length than the distance between the end surface of the projected stand 3b and the inner surface of the shell 1. A conductive elastomer layer 9 is previously provided at a screw 7 drive-in position on the shell 1. An acute conical part 7a to penetrate the layer 2 is provided on the point of the screw 7 and when the board 4 is mounted, the part 7a thrusts through the layer 2 to come into contact directly with the layer 9, is electrically jointed with the shell 1 via the layer 9 and grounding of the board 4 is made to complete.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grounding structure for a circuit board in an electronic equipment casing.

[0002]

2. Description of the Related Art Conventionally, a housing for housing electronic equipment such as a semiconductor device has a design appearance and an internal structure portion for mounting an electronic circuit board and the like, which is formed by injection molding of a thermoplastic resin. A molded body with a fitting is used. However, in recent years, the density of electronic devices has been remarkably increased, and the housing for housing these electronic devices is also required to be small in thickness, small in size, and lightweight. In addition, since various electronic devices have been widely used, electromagnetic waves emitted from the electronic devices may interfere with other electronic devices in the vicinity, such as a television, or conversely, other electronic devices in the vicinity. There is a risk of being disturbed by electromagnetic waves generated by and causing malfunctions.

In order to prevent the above electromagnetic waves from interfering with other electronic devices and malfunctioning due to the electromagnetic waves of other electronic devices, as shown in FIG. 2, the mechanical strength is higher than that of resin and the electromagnetic wave shielding property is provided. The metal outer shell 1 and the internal mechanism portion 3 made of a thermoplastic resin are combined with the synthetic resin adhesive layer 2
The use of a housing that is lightweight and has an electromagnetic wave shielding property has been started. The housing is up and down 2
This is a division structure of division. In addition, in FIG.
Reference numeral a is a spacer for connecting the divided pieces, 3b is a protruding base for mounting the circuit board 4, 4 is a circuit board mounted on the internal mechanism portion 5,
Is a circuit component mounted on the circuit board 4, 6 is a screw for connecting the divided pieces, and 7 is a screw for mounting the circuit board.

[0004]

However, in the case of the housing having the shielding property of the above-mentioned configuration, if the electronic circuit is grounded to the metal outer shell 1 in order to reduce the noise of the electronic equipment, Since the adhesive layer, which is an insulator, is interposed between the mechanism section and the metal shell, it is necessary to scrape off the adhesive layer in order to expose the surface of the metal shell. Further, in order to avoid the above-mentioned shaving process, it is conceivable to connect the ground lead wire 8 to the outer surface of the metal outer shell 1 as shown in FIG. Extending to the outer surface of the metal outer shell 1 is not preferable in appearance. Further, as shown in FIG. 4, in the divided surface of the two-divided structure, an inner flange is provided at the opening edge of each divided piece, the metal outer shell is positioned on the upper surface of the inner flange, and the ground lead wire 8 is provided on the upper surface. Figure 3
The problem of the outer shell of the one shown in is solved. However, in this case, since the inner flange portion is undercut, the machining is troublesome, and another problem of high cost occurs.

A method is also conceivable in which the tip of the circuit board mounting screw is formed so as to penetrate the adhesive layer, and the tip of the screw is brought into direct contact with the metal outer shell to be grounded when the circuit board is mounted. Since the force for tightening the screw is directly applied to the metal outer shell, a convex portion may be formed on the outer surface of the outer shell metal at the contact portion.

The present invention has been made based on the above circumstances, and a special processing is applied to a housing in which a metal outer shell and an internal mechanical portion made of synthetic resin are integrated through an adhesive layer. Provided is a grounding structure for a circuit board in an electronic device housing, which can ground the circuit board mounted in the housing without any damage and without impairing the design.

[0007]

A grounding structure of a circuit board in an electronic equipment casing according to the present invention comprises a metal outer shell and a resin internal mechanism portion adhered to the metal outer shell via an adhesive layer. In the electronic device housing having the above, a cushion layer made of a conductive elastomer is interposed between the metal outer shell and the adhesive layer at a position where a screw for mounting a circuit board is inserted, and The length under the neck is larger than the distance from the end surface of the protruding base to the outer surface of the adhesive layer, and the length under the neck is smaller than the distance to the inner surface of the metal shell, and the tip has a shape penetrating the adhesive layer. With the circuit board mounting screws,
By mounting the circuit board on the protrusion base, the circuit board and the outer shell metal are electrically connected to each other via a mounting screw and a conductive elastomer to be grounded.

[0008]

In the grounding structure of the circuit board in the electronic equipment casing of the present invention having the above-described structure, when the circuit board is mounted by the circuit board mounting screw, the tip of the screw penetrates through the adhesive layer to form a metal shell. By contacting the conductive elastomer layer bonded to the screw, the screw is electrically bonded to the metal outer shell through the conductive elastomer layer, and the grounding can be performed simultaneously with the mounting of the circuit board.

[0009]

1 is a front view of an example of a screw used in an embodiment of the present invention. In the present invention, for example, an aluminum outer shell is used as the metal outer shell, and a polypropylene outer shell is used as the internal mechanism portion.
Then, Novatec AP-, which is an ethylene-pinyl acetate copolymer (hereinafter EVA) having good adhesion to aluminum,
270L1 [Mitsubishi Kasei Co., Ltd. product name] and Novatec AP-19, which is EVA with good adhesion to polypropylene
6P2 [trade name of Mitsubishi Kasei Co., Ltd.] and polypropylene P
F250 [Mitsubishi Kasei Co., Ltd. product name] and 3 in the above order
Extruded into a film to form layers, total thickness 7
A resin film of 0 μm is formed to obtain an adhesive film.

With the surface of the polypropylene PF250 of the adhesive film having the above-mentioned structure as the outside, the conductive elastomer Emiculin S [trade name of Cemedine Co., Ltd.] is applied to the portion where the screw 7 for attaching the internal mechanism portion 3 is driven. hand,
An aluminum-resin laminate plate is formed by thermocompression bonding to a 0.6 mm-thick aluminum plate used as the cushion layer 9. This laminated plate is put into a press die and subjected to press working, and is formed into a required shape so that the adhesive film is on the inside, to obtain the metal outer shell 1 with the adhesive layer.

The internal mechanism section 3 is formed by injection molding of glass reinforced polypropylene G5830 [trade name of Mitsubishi Kasei Co., Ltd.], for example. That is, the metal outer shell 1 with the adhesive layer is inserted into an injection molding die having a cavity for forming the internal mechanism portion 3, and the glass reinforced polypropylene is injection molded to obtain the metal outer shell 1 and The internal mechanism section 3 is integrated.

In the housing constructed as described above, as shown in FIG.
The circuit board 4 is attached to the protruding table 3b by using the circuit board attaching screw 7 shown in FIG. The screw 7 has a length under the neck that is larger than the distance from the end surface of the protruding base 3b to the outer surface of the adhesive layer 2 and smaller than the distance to the inner surface of the metal outer shell 1, and its tip has a sharp conical tip. 7a is provided. When the circuit board 4 is attached to the protruding base 3b by the screw 7 having the above-described configuration, the conical tip portion 7a at the tip of the screw 7 breaks through the adhesive layer 2 and directly contacts the conductive elastomer layer 9, and the conductive elastomer layer 9 is contacted. It is electrically joined to the metal shell 1 which is joined to the layer 9. That is, according to the above-described embodiment, the grounding of the circuit board can be completed by simply attaching the circuit board without performing any processing on the housing.
The grounded portion has a resistance value of about 0.2Ω, the electric coupling between the metal shell 1 and the circuit board 4 is sufficient, and the grounded state is good.

The present invention is not limited to the above embodiment. For example, as the material of the metal outer shell, in addition to the exemplified aluminum plate, a plate material having a thickness of 0.2 to 2.0 mm made of a light and workable material such as a zinc alloy or a magnesium alloy can be used.

Further, as a means for laminating the metal outer shell and the adhesive film for adhering the internal mechanism portion, silver powder,
Conductive elastomer mixed with copper powder, stainless steel powder, etc., and filled with a conductive elastomer that has been applied in advance on the metal shell that is to be screwed in for mounting the circuit board, and then laminated with an adhesive film by means such as hot pressing. It is conceivable that a conductive elastomer is applied to the screw driving position of the adhesive film and then laminated with a metal shell.

Although the shape of the screw for mounting the circuit board can be arbitrarily selected, it is recommended to use the exemplified conical tip as the one that easily penetrates the adhesive layer. Furthermore, the adhesive and the material of the internal mechanism can be appropriately selected.

[0016]

According to the above-described circuit board grounding structure of the present invention, the grounding can be completed at the same time as the mounting of the circuit board without performing any special processing on the housing. It is possible to reduce the man-hours required to reduce the cost.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an electronic device casing including a metal outer shell and a resin internal mechanism portion.

FIG. 3 is a schematic cross-sectional view of an example of a circuit board grounding mode in the housing.

FIG. 4 is a schematic cross-sectional view of another example of the circuit board grounding mode in the housing.

[Explanation of symbols]

 1 ... Metal outer shell 2 ... Adhesive layer 3 ... Internal mechanism 3a ... Spacer 3b ... Projection stand 4 ... Circuit board 5 ... Circuit component 6 ... Divided piece connection Screw 7 ......... Circuit board mounting screw 7a ... Conical tip 8 .... Grounding lead wire 9 .... Cushion layer

Claims (1)

[Claims] 1. An electronic device housing having a metal outer shell and a resin internal mechanism portion adhered to the metal outer shell via an adhesive layer, wherein the metal outer shell and the adhesive layer are between the metal outer shell and the adhesive layer. A cushion layer made of a conductive elastomer is interposed at the driving position of the screw for mounting the circuit board, and the length under the neck is longer than the distance from the end surface of the protruding stand for mounting the circuit board of the internal mechanism section to the outer surface of the adhesive layer. The circuit board is attached to the projecting stand by a screw for mounting the circuit board, which is large and has a length under the neck smaller than the distance to the inner surface of the metal outer shell and has a tip penetrating the adhesive layer. A grounding structure for a circuit board in an electronic device housing, wherein the board is grounded.