JPH0992941A - Printed wiring board for preventing crosstalk and circuit unit using the board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a printed wiring board which prevents mutual interference between adjacent signal lines and dispenses with feed-through capacitors. SOLUTION: Ground lines 2 are formed on both sides of signal lines, together with the signal lines, by using a board wherein copper foil layers are formed on both surfaces of a synthetic resin laminated substratum layer 5. The signal lines are coated with a dielectric covering layer 3, and the upper parts of the ground lines 2 and the dielectric covering layer 3 are coated with a conductor covering layer 4 in which synthetic resin and metal powder are mixed. Penetrating holes 8 are formed on a part of the ground lines 2, electrically connected with a copper foil layer 6 of the back via the ground lines 2 of the surface and the conductor covering layer 4, and dropped to a ground voltage. Thereby feed-through capacitors are equivalently formed in the signal lines, and interference between the signal lines is excluded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board used for a tuner of a television receiver, a high-speed digital signal processing circuit, etc., and more particularly to a printed wiring board for crosstalk prevention in which signal crosstalk is reduced. The present invention relates to a circuit unit using a substrate.

[0002]

2. Description of the Related Art A conventional crosstalk preventing means for a printed wiring board will be described. For example, a high-frequency signal flows between circuit blocks that constitute a tuner of a television receiver, a high-speed digital signal processing circuit, or the like. Therefore, mutual interference (crosstalk) occurs between adjacent circuit blocks. In order to prevent this, a feedthrough capacitor is often used in the signal line. These circuit blocks are often shielded by a shield case. A circuit block and another block are coupled to each other via a feedthrough capacitor. In general, at least each lead portion through which a signal passes is surrounded by a component of earth potential having a predetermined capacitance with respect to the lead portion.

[0003]

In such a case, the feedthrough capacitor must be provided as a new component, the cost thereof cannot be ignored, and the mounting structure becomes complicated.

The present invention has been made in view of such conventional problems, and the printed wiring board is provided with a function similar to that of a feedthrough capacitor so that circuit blocks and adjacent signal lines are mutually connected. It is an object of the present invention to provide a printed wiring board for crosstalk prevention which prevents interference and to realize a circuit unit using these printed wiring boards.

[0005]

According to a first aspect of the present invention, a synthetic resin base material layer 5 serving as a base material of a printed wiring board is provided.
A signal line 1 formed of a conductor foil on a part of the surface of the synthetic resin base material layer for transmitting an electric signal; a synthetic resin dielectric coating layer 3 covering the signal line; Is formed on the synthetic resin base material layer with a space of
One of the ground line 2 connected to the ground potential, the ground potential conductor layer 6 formed on the back surface of the synthetic resin base layer having the signal line, and the synthetic resin base layer having the ground line formed thereon. Part of the through hole 8 and a synthetic resin conductor film for connecting the ground potential conductor layer and the earth line through the through hole and for shielding the signal line with the synthetic resin dielectric film layer interposed therebetween. Layer 4
And are provided.

In the invention of claim 2 of the present application, the through hole is a conductive through hole in which a conductive film is formed on the wall surface in place of the synthetic resin conductive film layer. .

The invention of claim 3 of the present application is the same as that of claim 1 or 2.
While covering the printed wiring board for crosstalk prevention according to the description, it has a side wall that is connected to at least one of the synthetic resin conductor film layer and the ground potential conductor layer and that crosses the signal line, and outside the side wall. Shield case 1 with the connection end of the signal line and the earth line pulled out
It is characterized by having 1.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) A printed wiring board according to an embodiment of the present invention will be described with reference to FIGS. 1 is a partial plan view of a printed wiring board for crosstalk prevention of the present embodiment, FIG. 2 is a vertical cross-sectional view taken along the line BB 'of FIG. 1, and FIG. 3 is a main view taken along the line AA' of FIG. FIG. As shown in FIG. 2, the printed wiring board has a signal line copper foil pattern layer (signal line) 1 and a ground potential copper foil pattern layer (earth line) 2 formed on both sides thereof. Resin dielectric film layer (dielectric film layer) 3
Signal line 1 and ground line 2 by shielding with
An equivalent feedthrough capacitor is provided between them in a distributed constant manner.

These signal line 1 and earth line 2
Like a conventional printed wiring board, is based on a synthetic resin laminated base material layer (laminated base material layer) 5. The ground potential copper foil layer (copper foil layer) is formed on most of the back surface of the laminated base material layer 5. 6) is formed as a ground potential conductor layer. Since the signal line 1 and the ground line 2 are connected to other circuit blocks as shown in FIG. 1, the patterns are alternately formed so as to be parallel to each other at the edge of the printed wiring board itself.

Before these patterns are formed, that is, the original structure of the printed wiring board is such that a copper foil having a thickness of, for example, about 17 to 35 μm is laminated on both sides of a synthetic resin laminated plate mixed with glass fibers. The conductor film layer 4 is a mixture of a synthetic resin liquid and metal powder such as copper powder in a predetermined ratio, and the ground line 2 provided on the surface of the laminated substrate layer 5 and the copper foil layer 6 provided on the back surface are electrically connected to each other. And has a function of shielding the signal line 1 from other signal lines through the dielectric film layer 3 while being electrically connected.

The dielectric coating layer 3 and the conductor coating layer 4 are layers which are coated by screen printing or the like and cured by heating and drying. The laminated base material layer 5 is an insulative plate-like member made of synthetic resin containing glass fiber or the like, and is formed by thermocompression lamination molding.

Next, as shown in FIGS. 1 and 2, through holes 8 are provided in a part of the earth line 2, respectively. The through hole 8 is formed by penetrating the printed wiring board by drilling, and the wall surface of the through hole 8 is coated with the conductor film layer 4. Instead of forming the conductor coating layer 4 in the through hole 8, copper plating may be coated in a separate step (through hole). Next, the laminated base material layer 5 is formed by using materials and processes that are generally commonly used.
A protective solder resist film 10 is formed on the uppermost surface of the.

Then, each signal line 1 is electromagnetically shielded by the ground line 2 on the upper surface of the laminated base material layer 5 through the dielectric coating layer 3 and the conductive coating layer 4, so that the laminated base material layer 5 has The back surface is electromagnetically shielded by the copper foil layer 6 connected to the ground potential. In manufacturing the above-mentioned printed wiring board for crosstalk prevention, an additive method can be used as a method of omitting the etching step. In this case, a copper plating pattern can be formed on both surfaces of the laminated base material layer 5 to form a copper foil pattern for wiring.

(Embodiment 2) A circuit unit using the above-described printed wiring board for crosstalk prevention will be described with reference to FIGS. For example, in a tuner of a television receiver, a printed wiring board that constitutes the circuit is often shielded by a shield case. As shown in FIG. 6, the circuit unit has a structure in which a printed wiring board is housed while being shielded in a box-shaped shield case 11, and a connection portion between the signal line 1 and the ground line 2 is exposed on the side surface thereof. Laminated substrate layer 5 having such a conductor pattern at the end
Is used for connection with the other party's circuit.

In the case of such a structure, as shown in FIGS. 4 and 5, a part of the metal plate forming the shield case 11 is provided on the upper surface of the laminated base material layer 5, the conductor film layer 4 and the ground potential. It is electrically connected to at least one of the copper foil layers 6. In this case, the protective solder resist film 10 at the portion connected to the shield case 11 is removed in advance, and the conductive adhesive 12 or the like is used to connect to this portion or by soldering. By doing so, the shield case 11 is held at the ground potential, and a further shielding effect can be obtained for the built-in circuit block and the signal line. When the shield case 11 is connected to the ground potential, the conductive adhesive 12
Instead of using, the shield case 11 itself may be provided with a leaf-shaped spring having elasticity, and the spring may be used to connect to the conductor film layer 4.

[0016]

As described above in detail, according to the present invention, the signal line is coated with the synthetic resin dielectric coating layer and the outside is shielded with the synthetic resin conductive coating layer through which the ground potential is passed. This makes it possible to eliminate interference between signal lines due to electromagnetic waves. Further, since the feedthrough capacitor which has been conventionally interposed between the circuit blocks is unnecessary, the effect of reducing the material and the processing cost for the printed wiring board can be obtained. Furthermore, by attaching a shield case so that it is connected to the synthetic resin conductor film layer or the ground potential conductor layer,
It is possible to realize a used circuit unit in which the influence of external unwanted radiation is prevented on the entire circuit block.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of a crosstalk preventing printed wiring board according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the structure of a printed wiring board for crosstalk prevention of the present embodiment.

FIG. 3 is a partial cross-sectional view showing the main part structure of the printed wiring board for crosstalk prevention of the present embodiment.

FIG. 4 is a partial plan view showing a main part structure of a used circuit unit in one embodiment of the present invention.

FIG. 5 is a partial plan view showing a main part structure of a used circuit unit of the present embodiment.

FIG. 6 is a perspective view showing an appearance of a circuit unit used in the present embodiment.

[Explanation of symbols]

 1 Signal Line Copper Foil Pattern Layer (Signal Line) 2 Earth Potential Amount Copper Foil Pattern Layer (Earth Line) 3 Synthetic Resin Dielectric Film Layer (Dielectric Film Layer) 4 Synthetic Resin Conductor Film Layer (Conductor Film Layer) 5 Synthetic resin laminated base material layer (laminated base material layer) 6 Earth potential copper foil layer (copper foil layer) 8 Through hole 10 Solder resist film for protection 11 Shield case 12 Conductive adhesive

Claims (3)

[Claims] 1. A synthetic resin base material layer as a base material of a printed wiring board, and a conductive foil formed on a part of the surface of the synthetic resin base material layer,
A signal line for transmitting an electric signal, a synthetic resin dielectric film layer covering the signal line, and a signal line formed on the synthetic resin base material layer at a predetermined distance, and connected to a ground potential. An earth line, an earth potential conductor layer formed on the back surface of the synthetic resin base layer having the signal line, and a through hole provided in a part of the synthetic resin base layer on which the earth line is formed, A synthetic resin conductor film layer for connecting the earth potential conductor layer and the earth line through the through hole and for shielding the signal line with the synthetic resin dielectric film layer interposed therebetween. A printed wiring board for crosstalk prevention. 2. The crosstalk preventing print according to claim 1, wherein the through hole is a conductive through hole having a wall surface on which a conductive film is formed instead of the synthetic resin conductor film layer. Wiring board. 3. A side wall that covers the printed wiring board for crosstalk prevention according to claim 1 and is connected to at least one of the synthetic resin conductor film layer and the ground potential conductor layer and crosses the signal line. And a shield case having a connection end of the signal line and the ground line drawn out of the side wall of the circuit unit.