GB2301944A

GB2301944A - Shield case having protrusions supporting a circuit board

Info

Publication number: GB2301944A
Application number: GB9608621A
Authority: GB
Inventors: Hideki Watanabe
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1995-06-08
Filing date: 1996-04-24
Publication date: 1996-12-18
Anticipated expiration: 2016-04-24
Also published as: KR970004998A; CN1145571A; JPH08335794A; MY115798A; DE19622837A1; GB2301944B; GB9608621D0; DE19622837C2

Description

2301944 SHIELD CASE The present invention relates to a shield case mounted

to cover major portions or the whole body of an electronic circuit board.

In an electronic circuit device a shield case produced of a conductive metal is mounted for the purpose of decreasing unnecessary radiation to the outside (particularly when an oscillation circuit is mounted), or preventing the effect of noise from outside or from other circuits (particularly noise from a highgain high-frequency amplifier etc.). Especially, to enhance shielding effect, a closed type shield case is employed, housing a printed circuit board in a metal frame body and covering the top and bottom of the frame body with metal plates.

Fig. 4 is a perspective view showing the constitution of major portions of a prior art shield case. As shown in this drawing, a frame body 1 is formed of four side plates la, lb, lc and ld connected or pressed into a configuration of square frame. insice

1 - this frame body 1 is disposed a printed circuit board 2. When the printed circuit board 2 measures a x b, the inner size of the frame body 1 is set to [a + a] x [b + a] so that the printed circuit board may easily be assembled in the frame body 1. Also, in Fig. 4, unillustrated metal covers are installed on the top and bottom of the frame body 1 after mounting the printed circuit board 2 to the frame body 1. The frame body 1 and the covers are jointed elastically with a grasping force.

In the above-described prior art, however, the frame body covered with the covers as shown in Fig. 4 receives an inward deflecting force caused by an external force 3 as shown in Fig. 5 which is applied by a grasping force of pawls provided on two opposite sides of the covers 4a and 4b. Since a spacing a is provided as shown in Fig. 6 between the peripheral surface of the printed circuit board 2 and the inside wall surface of the frame body 1, the external force 3 is applied to solder 5 which bridges the inner surface of the side plate and a ground conductor provided on the printed circuit board 2 through the frame body 1. Therefore, the solder 5 will be cracked with use and age, resulting in a defective connection.

it is, therefore, an object of the present invention to provide a shield case wherein a stress from a frame body acts only on a printed circuit board and not on solder on the board.

To accomplish the above-mentioned object, the present invention provides a shield case which comprises a metal frame having four sides, a printed circuit board disposed in the frame body, and metal covers mounted to cover the top and bottom sides of the frame body; the frame body being provided with a plurality of rib-like projections extending vertically on inside wall surfaces of the frame body.

In this case, a spacing between a pair of the projections provided on mutually facing ones of the inside wall surfaces can be made approximately equal to the size of the printed circuit board.

Furthermore, it is possible to provide an inclined surface on at least one of the end portions of the projections.

According to the above-described means, an external force exerted to the frame body will be added to the end surface of the printed circuit board via the rib-like projections vertically extending on the inner 3 - wall surface of the frame body, but not the solder connecting the frame body and the board. Therefore the solder will not be cracked during long- time use and no troubles will be caused to occur by the external force applied to the frame body.

Since the spacing between a pair of projections provided on the mutually opposite inner walls of the frame body is nearly equal to the size of the printed circuit board, the printed circuit board is held in a grasped state in contact with the rib-like projections until soldered to the frame body. Therefore the printed circuit board will require no position correction prior to the soldering, ensuring smooth installation work.

Furthermore, because the end portion of the riblike projections is provided with an inclined surface, the printed circuit board will not be caused by the end portion of the projections when the board is inserted into the frame body through one opening. Accordingly the installation can be accomplished in a short time.

In addition, it is possible to acquire such an effect that the provision of the rib-like projections increases the strength of the frame body, to thereby reduce deformation of the frame body, thus lessening the external force applied from the frame body to the printed circuit board if the covers which elastically hold the frame body are mounted at the openings of the frame body.

The above and other objects, features and advantages of the present invention will become clear from the following description with reference to the accompanying drawings., is\ WL 1 c;

Fig. 1 is a perspective view showing one preferred embodiment of a shield case of the present invention; Fig. 2 is a sectional view of the shield case shown in Fig. 1 mounted with a printed circuit board; Fig. 3 is a sectional view taken on line Fig. 3Fig. 3 of Fig. 2; Fig. 4 is a perspective view showing the constitution of major portions of a prior art shield case;

Fig. 5 is plan view showing the prior art shield case applied with an external force; and

Fig. 6 is a sectional view showing the prior art shield case of such a construction that a stress is applied to solder.

- Hereinafter a preferred embodiment of a shield case according to the present invention will be explained with reference to the aCCOMDanying drawings.

Fig. 1 is a perspective view showing one embodiment of the shield case according to the present invention; Fig. 2 is a sectional view showing the shield case shown in Fig. 1 mounted with a printed circuit board; and Fig. 3 is a sectional view taken along line Fig. 3-Fig. 3 of Fig. 2.

As shown in Fig. 1, a frame body 6 used in the present invention is produced by connecting or pressing four conductive metal side plates 6a, 6b, 6c and 6d into a shape of square frame. The side plates 6a and 6c have two ribs 7a as projections on the inner wall, while the side plates 6b and 6d have one rib 7b, respectively. As shown in Fig. 2, these ribs 7a and 7b are vertically formed bulging inward by means of a half punch or other; a spacing between opposite ribs is set nearly to the outside dimensions of a printed circuit board 8 disposed in the frame body 6.

As shown in Figs. 2 and 3, the printed circuit board 8 is positioned so as to be grasped between the ribs 7a and 7a and between the ribs 7b and 7b in the 6 - frame body 6; in this state, the ground conductor on the board and the inner surface of the side plate are jointed by solder 9, thereby securing and grounding the printed circuit board 8 to the frame body 6. Thereafter a cover 10a is attached to the top surface of the frame body 6 and a cover 10b to the bottom surface.

Soldering to the frame body 6 may be done in the positions of the ribs 7a and 7b, and also in the positions in which the ribs 7a and 7b are not provided and the frame body 6 and the printed circuit board 8 may be bridged.

Having described a preferred embodiment of the invention with reference to the accompanying drawings, it will be appreciated that the present invention is not limited to the precise embodiment, and that various changes and modifications can be effected therein by one of ordinary skill in the art without departing from the scope of the invention as defined by the appended claims.

Claims

1. A shield case, comprising: a metal frame having four sides, a printed circuit board disposed in said frame body, and metal covers mounted to cover the top and bottom sides of said frame body; said frame body being provided on the inner wall surfaces with a plurality of rib-like projections extending vertically.

2. A shield case according to Claim 1, wherein a spacing between a pair of said projections provided on mutually facing ones of said inner wall surfaces is equal to the size of said printed circuit board, and a ground conductor provided on said printed circuit board is soldered to said inner wall surface of said frame body.

3. A shield case according to Claim 1, wherein said projections are provided on each of said four sides.

4. A shield case according to Claim 1, wherein said projections are formed by half-punching in said frame body and provided with an inclined surface at least on one end portions thereof.

5. A shield case substantially as hereinbefore described, with reference to, and as illustrated by, the accompanying drawings.

Amendments to the claims have been f lied as follows 1. A shield case, comprising: a metal frame having four sides, a printed circuit board disposed horizontally in said frame body, and metal covers mounted to cover the top and bottom sides of said frame body; said frame body being provided on the inner wall surface of each of the four sides with rib-like projections extending vertically, wherein at least one of the metal covers is sized to cover the top or bottom sides of the metal frame, said metal covers having pawls on at least one corresponding pair of parallel edges so as to joint elastically to the frame body with a grasping force, and clamping elastically at least one corresponding pair of parallel side plates of the metal frame with said pawls. 2. A shield case according to Claim 1, wherein a spacing between a pair of said projections provided on mutually facing ones of said inner wall surfaces is equal to the size of said printed circuit board, and a ground conductor provided on said printed circuit board is soldered to said inner wall surface of said frame body. 3. A shield case according to Claim 1, wherein said projections are provided on each of said four sides. 4. A shield case according to Claim 1, wherein said projections are formed by half-punching in said frame body and provided with an inclined surface at least on one end portions thereof. 5. A shield case substantially as hereinbefore described, with reference to, and as illustrated by, the accompanying drawings.

9