JPH0923083A - Connecting structure of circuit board and cabinet and cabinet structure, for restraining unnecessary radiation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain unnecessary radiation by restraining a high frequency noise current flowing into a cabinet from a circuit board generating the noise. SOLUTION: This cabinet structure consists of the following; a circuit board 1 having a signal ground, a cabinet 2 forming a frame ground, a metal spacer 3 which connects the signal ground and the cabinet, and a magnetic core 4 which is formed in an unified body with the metal spacer 3 and restrains high frequency current flowing from the signal ground to the cabinet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connection structure and a housing structure for a circuit board and its housing related to an electronic circuit device.

[0002]

2. Description of the Related Art The prior art is, for example, IEE transaction on electromagnetic compatibility, October 1992, G.I. Seri, "Theoretical and Experimental Evaluation of the Electro Magnetic Radiation from Aperture in Shielded Enclosures" (G. Ceri,
Theoretical and Experimen
tal Evaluation of the Elec
tromagnetic Radiation Fro
m Apertures in Shielded E
nclosures "IEEE Trnansacti
on on Electro Magnetic Co
mpatability, vol. 34, no. 4, N
As described in "Ovenber 1992", the ground (signal ground) of the circuit board and the casing (frame ground) are connected by a conductor such as a spacer.

[0003]

In the prior art, a circuit board mounted inside the housing operates to generate a high frequency noise voltage in the signal ground, and a spacer, which is a connection point with the frame ground of the housing, is used. A noise current flows through the entire housing via the housing to drive an electric resonance system formed in the entire housing to generate radiation. That is, the high frequency noise of the circuit board is transmitted to the entire housing, which causes a large radiation.

[0004]

[Means for Solving the Problems] By providing a connection conductor for keeping the circuit board and its housing at the same potential with a function of suppressing high-frequency current, a high-frequency current flowing from a circuit board that generates noise into the housing Unnecessary radiation is suppressed by suppressing noise current.

[0005]

The magnetic flux generated by the high-frequency current passing through the connecting conductor passes through the ferrite core mounted around the connecting conductor. The inductance and resistance components generated by the concentration of magnetic flux in the ferrite core and the loss inside the ferrite core act to suppress the high-frequency current penetrating therethrough.

[0006]

EXAMPLE A first example according to the present invention will be described with reference to FIG. Reference numeral 1 is a circuit board, 2 is a housing, 3 is a metal spacer, and 4 is a magnetic core integrated with the metal spacer 3. The electronic device includes a circuit board 1 and a housing 2,
The signal ground of the circuit board and the frame ground of the housing are electrically and mechanically connected by the metal spacer 3,
The circuit board is mechanically fixed to the housing, and electrostatic discharge is generated in both grounds so that both grounds have the same potential. The present invention intends to improve workability when the circuit board is attached to the housing by integrally forming the metal spacer and the magnetic core.

In the present invention, the magnetic core 4 is mounted around the metal spacer 3 to form an integral structure, and the inductance and resistance components of the magnetic core 4 cause a large loss to the high frequency current flowing through the metal spacer. To

FIG. 3 shows an actual electronic device having the dimensions shown in FIG. 2 as an example to show the effect of the present invention.
The experimental results are shown. The conventional technology is a radiated electromagnetic field when the housing and the circuit board are connected only by a metal spacer,
An increase in radiation due to the resonance of the housing is observed near 150 MHz. On the other hand, in the case of the present embodiment in which the magnetic core is attached to the metal spacer, the radiation in the vicinity of 150 MHz can be suppressed by about 25 dB as compared with the conventional technique. Thus, the effects of the present invention are clearly shown by the experimental results.

A second embodiment will be described with reference to FIG. The electronic device is composed of a circuit board 1 and a housing 2, and the signal ground and the frame ground are connected by a metal spacer 3 to fix the board. In the second embodiment, the resistance sheet 5 is mounted between the metal spacer 3 and the housing to suppress the noise current flowing through the metal spacer. At this time, the resistance sheet 5
Is such that the circuit board 1 has a resistance value capable of electrostatic discharge to the housing 2 and has a resistance value that suppresses a high-frequency current from the circuit board 1 to the housing 2. The second embodiment also achieves the same effect as the first embodiment.

A third embodiment will be described with reference to FIG. In large electronic devices, in order to mount multiple circuit boards,
A conductor frame 6 as shown in FIG. 5 is often used. When the high frequency noise current from the circuit board flows through the conductor frame 6, the radiation increases.
Therefore, in the present embodiment, as shown in the drawing, the magnetic body 7 is attached to the periphery of the conductor frame 6 to form an integral structure, and high frequency current flowing in the conductor frame 6 is suppressed, whereby unnecessary electromagnetic radiation can be reduced. Become. Further, although not shown, the magnetic body 4 may not be surrounded by the conductor frame 6, but the magnetic body 4 may be attached along the longitudinal direction of the conductor frame 6 to form an integrated structure. A similar effect can be expected.

[0011]

The high frequency current flows from the signal ground of the circuit board to the frame ground of the housing through the connecting conductor between the circuit board and the housing, which causes unnecessary radiation. As a result, unnecessary radiation can be suppressed by the reduction. This means
By mounting the magnetic core in the path, magnetic flux concentration in the magnetic core and loss inside the core occur, so that the high-frequency current can be suppressed and unnecessary radiation can be suppressed.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment.

FIG. 2 is an example of an actual electronic device for which experimental results are obtained.

FIG. 3 is an experimental result for demonstrating the effect of the present invention using the example of FIG.

FIG. 4 is an explanatory diagram of a second embodiment.

FIG. 5 is an explanatory diagram of a third embodiment.

[Explanation of symbols]

 1 Circuit Board 2 Housing 3 Metal Spacer 4 Magnetic Core 5 Resistive Sheet 6 Conductor Frame

Claims (6)

[Claims] 1. A circuit board having a signal ground,
The signal ground includes a casing forming a frame ground, a connection conductor connecting the signal ground and the casing, and a magnetic core surrounding the connection conductor and integrally structured with the connection conductor. An electronic circuit device which suppresses a high-frequency current flowing from the housing to the housing. 2. A circuit board having a signal ground,
A casing that forms a frame ground, a connection conductor that connects the signal ground and the casing, and a resistance sheet that is interposed between the connection conductor and the signal ground or the casing. An electronic circuit device which suppresses a high-frequency current flowing in the housing. 3. A circuit board having a signal ground,
A casing that forms a frame ground and is composed of a plurality of conductor frames, a connection conductor that connects the signal ground and the casing, and a magnetic core that surrounds the periphery of the conductor frame and is integrally structured with the conductor frame. And suppressing a high frequency current flowing from the signal ground to the housing. 4. A circuit board having a signal ground,
A housing that forms a frame ground and is composed of a plurality of conductor frames, a connection conductor that connects the signal ground and the housing, and a magnetic core that is attached along the conductor frame and is integrated with the conductor frame. And an electronic circuit device for suppressing high-frequency current flowing from the signal ground to the housing. 5. A connection structure between a circuit board and a housing, which is an integrated structure of a central electrical and mechanical connection conductor and a magnetic core surrounding the conductor. 6. A case for suppressing high-frequency current, which is obtained by integrally forming a conductor frame of the case and a magnetic body arranged around the conductor frame or attached to the conductor frame.