JPH11284291A - Circuit board and liquid crystal display device with the circuit board mounted - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure for connecting a circuit board by which generation of EMI(electromagnetic interference) can be reduced, and to reduce EMI in a liquid crystal display device by mounting this circuit board. SOLUTION: GND pads 1 for shielding are electrically connected to a shield conductor of a connector formed on a circuit board. The GND pads 1 are not electrically connected to a GND pattern 4 on the circuit board but are connected to a pad 2 through a wide conductor patterns which is electrically connected. In this structure, since the GND pads 1 which are electrically connected to the shield conductor of the connector are not electrically connected to the GND pattern of the circuit board, the ground bouncing produced on the GND pattern of the circuit board does not affect adversely the GND shield of the connector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a circuit board on which a connector is installed and a liquid crystal display device having the circuit board.

[0002]

2. Description of the Related Art FIG. 5 shows an LV in a conventional liquid crystal display device.
FIG. 2 is a schematic diagram illustrating an example of a connector with a GND shield (manufactured by Japan Aviation Electronics, FI-WE-21P-HF) used for a DS (Low Voltage Differential Signaling) interface. In the figure, 13 is a shield conductor in a connector outer shell portion, 14 is a terminal, 15 is an insulating portion made of resin, 16
Indicates claw portions which are hook portions with other connectors forming a pair with the connector shown in FIG. FIG. 6 is a view showing an example of component pads for mounting the connector shown in FIG. 5 on a circuit board. In the figure, reference numeral 1 denotes a shielding GND pad, to which a shield conductor 13 in a connector outer skin portion shown in FIG. 5 is electrically connected. Reference numeral 6 denotes a terminal pad.

FIG. 7 is a plan view showing a circuit board on which a conventional connector is mounted. In the figure, 1 is a shielding GND pad to which a shield conductor of a connector mounted on a circuit board is electrically connected, and 2 is a housing of a device on which the circuit board is mounted (for example, a housing of a liquid crystal display device).
3 is a wide conductor pattern for electrically connecting the shielding GND pad 1 to the electrical connection pad 2 for the housing, and 4 is a conductor pattern formed on the surface of the circuit board. GND pattern of circuit board, 5 is G
Via holes for electrical connection between the ND pattern 4 and an inner layer GND pattern formed in an inner layer (a layer other than the surface layer) of the circuit board, 6 is a terminal pad of a connector terminal mounted on the circuit board, and 17 is a shield pad. This is a conductor pattern for connecting the GND pad 1 and the GND pattern 4 of the circuit board.

In the GND pattern 4 of the circuit board, potential fluctuations (ground bowing) due to current at the time of IC switching, stray capacitance and stray inductive noise in the circuit board, and the like occur. Is transmitted to the casing or the shield conductor of the cable, the casing or the cable itself becomes an antenna, and unnecessary radiation noise (hereinafter referred to as EMI: Electro-Magnetic Interference) may increase. The interface cable connecting the liquid crystal display device and the system side that emits the display signal has a resonance frequency (for example, 25 c
Assuming that m, λ / 4 = 300 MHz) often enters a frequency band (several tens of MHz to several hundred MHz) which is a problem and becomes a noise source. Has become.

[0005]

The connection between the conventional liquid crystal display device and the circuit board is constituted as described above, and is provided on the outer surface of the interface cable for connecting the liquid crystal display device to the system which emits the display signal. If the GND of the shield conductor is stable in terms of potential, a shielding effect can be expected. However, as shown in FIG. 7, the shield GND pad 1 to which the shield conductor of the connector is connected and the GND pattern of the circuit board are provided. In the case where the wires 4 are electrically connected, there is a problem that the ground vowing generated in the GND pattern 4 of the circuit board adversely affects the shield GND of the connector and the cable, and increases EMI.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and provides a connection structure for a circuit board capable of reducing the generation of EMI. An object is to reduce EMI.

[0007]

According to the present invention, there is provided a circuit board on which a connector having a GND shield is mounted, wherein a shielding GND pad on the circuit board electrically connected to the GND shield of the connector is provided. Is connected via a conductor pattern to a portion of the circuit board that is electrically connected to the housing of the device on which the circuit board is mounted, and is electrically insulated from the GND pattern of the circuit board. Is what is being done. A screw hole, which is used for a GND connection between the circuit board and the housing and has a conductor formed therein, and an inner layer G formed on an inner layer of the circuit board.
An inner layer GN around the screw hole, comprising an ND pattern
By removing the D pattern, the conductor of the screw hole and the inner layer GND pattern are insulated. Also, an inner layer GN formed on an inner layer of the circuit board
D pattern is provided, and the inner layer GND pattern is formed excluding a region overlapping with a region where the shielding GND pad and the conductor pattern are formed.
Further, a liquid crystal display device according to the present invention has the circuit board configured as described above mounted thereon.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a circuit board connection structure and a liquid crystal display device on which the circuit board is mounted according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view showing a circuit board according to Embodiment 1 of the present invention. In the figure, reference numeral 1 denotes a shielding GN to which a shield conductor of a connector mounted on a circuit board is electrically connected.
D pad 2 is a pad for electrical connection with a housing of a device on which a circuit board is mounted (for example, a housing of a liquid crystal display device). It is electrically connected to the housing via the surface mount components. Reference numeral 3 denotes a wide conductor pattern for electrically connecting the shield GND pad 1 to the pad 2 for electrical connection to the housing. Pattern 4
Via holes for electrical connection between the substrate and an inner layer GND pattern formed in an inner layer (a layer other than the surface layer) of the circuit board; 6
Is a terminal pad of a connector terminal mounted on the circuit board. In the circuit board according to the present embodiment, the shield GND pad 1 electrically connected to the shield conductor of the connector is not electrically connected to the GND pattern 4 formed on the circuit board.

According to the present invention, the shield GND pad 1, which is electrically connected to the shield conductor of the connector,
Since it is not electrically connected to the GND pattern 4 of the circuit board, ground voicing generated in the GND pattern 4 of the circuit board does not adversely affect the GND shield of the connector.

Embodiment 2 FIG. 2 is a plan view showing a circuit board according to Embodiment 2 of the present invention, and FIG. 3 is a plan view showing a conductor pattern of an inner layer (a layer other than the surface) of the circuit board shown in FIG. In the figure, 7 is a GN for the circuit board and the housing.
A conductor is formed inside the screw hole 7 and the land 8 on the surface layer of the circuit board in a screw hole for D connection. 9
Is a clearance portion provided to insulate the conductor formed in the screw hole 7 and the inner layer GND pattern 10 formed of a conductor solid pattern formed widely in the inner layer of the circuit board. The land 8 is electrically connected to the shield GND pad 1 by the wide conductor pattern 3.
Further, the other configuration is the same as that of the first embodiment, and the description is omitted.

In this embodiment, the housing and the circuit board are connected to GND by the screw holes 7 in which the conductors are formed, and the shielding GN is electrically connected to the shield conductor of the connector.
Since the D pad 1 is electrically connected to the land 8 of the screw hole 7 and is electrically insulated from the GND pattern 4 formed on the circuit board, the same effect as in the first embodiment can be obtained.

Embodiment 3 FIG. 4 is a plan view showing a conductor pattern of an inner layer (a layer other than the surface) of a circuit board according to Embodiment 3 of the present invention. The surface layer of the circuit board according to the present embodiment is the same as the plan view of the circuit board shown in FIG. In the figure, reference numeral 11 denotes a region on the surface layer of the circuit board corresponding to the region where the shielding GND pad 1 and the conductor pattern 3 are formed, in which the inner layer GND pattern 10 is not formed. The other configuration is the same as that of the second embodiment, and the description is omitted.

According to the present embodiment, the inner-layer GND pattern 10 is not formed in the region 11 below the region where the shielding GND pad 1 and the conductor pattern 3 are formed in the surface layer of the circuit board. Overlap of the conductor patterns between the layers can be eliminated, and crosstalk (crosstalk) noise caused by the capacitance component can be reduced. Note that the same effect can be obtained even when applied to the inner layer of the circuit board shown in the first embodiment.

[0014]

As described above, according to the present invention, the shielding G electrically connected to the shield conductor of the connector is provided.
The ND pad is not electrically connected to the GND pattern of the circuit board on which ground bowing occurs, but is connected to a portion electrically connected to the housing by a conductor pattern, so that the shielding effect is ensured. Obtained and E
MI can be reduced. Further, according to the present invention, it is possible to reduce the crosstalk noise generated when the conductor patterns overlap between the layers of the circuit board. Further, according to the present invention, a liquid crystal display device with reduced EMI can be obtained by mounting the circuit board having the above structure on the liquid crystal display device.

[Brief description of the drawings]

FIG. 1 is a plan view showing a circuit board according to Embodiment 1 of the present invention.

FIG. 2 is a plan view showing a circuit board according to Embodiment 2 of the present invention.

FIG. 3 is a plan view showing an inner layer of a circuit board according to Embodiment 2 of the present invention.

FIG. 4 is a plan view showing an inner layer of a circuit board according to Embodiment 3 of the present invention.

FIG. 5 is a perspective view showing a connector with a shield GND.

FIG. 6 is a diagram showing a component pad on which a connector is mounted.

FIG. 7 is a plan view showing a conventional circuit board of this type.

[Explanation of symbols]

1 GND pad for shield, 2 pad, 3 conductor pattern, 4 GND pattern of circuit board, 5 via hole, 6 terminal pad, 7 screw hole, 8 land, 9
Clearance, 10 inner layer GND pattern, 11 areas.

Claims (4)

[Claims] 1. A circuit board on which a connector having a GND shield is mounted, wherein a GND pad for shielding on the circuit board which is electrically connected to a GND shield of the connector is formed on the circuit board on the circuit board. It is connected to a portion electrically connected to the housing of the device to be mounted via a conductor pattern, and is configured to be electrically insulated from the GND pattern of the circuit board. Circuit board. 2. A circuit board comprising: a screw hole in which a conductor is formed therein; and an inner layer GND pattern formed in an inner layer of the circuit board. 2. The circuit board according to claim 1, wherein the conductor of the screw hole is insulated from the inner layer GND pattern by removing the inner layer GND pattern. 3. An inner layer GND formed on an inner layer of a circuit board.
3. The circuit board according to claim 1, further comprising a pattern, wherein the inner-layer GND pattern is formed except for a region overlapping a region where the shield GND pad and the conductor pattern are formed. 4. A liquid crystal display device comprising the circuit board according to claim 1.