JPH11298097A - Printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board which has great effect of decreasing electromagnetic waves and the small bottom area for a guard conductor. SOLUTION: A base member 11 of a printed wiring board is glass epoxy material. A guard conductors 13 are formed so that the guard conductors 13 are larger than a high frequency wiring 12 in height, above 3 the surface of the base member 11. The guard conductor 13 is formed by coating a metallic conductor 14 which is typically a copper foil with a conductive paste and curing it. Thus, the guard conductors 13 are formed with larger height, which enables electrode areas to be larger even through the bottom areas are the same, which increases a coupling capacitor due to the difference in electrode area and enhancing the effect of shielding due to the differences in height.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printed wiring board, and more particularly to a printed wiring board capable of reducing radiation noise of electronic equipment.

[0002]

2. Description of the Related Art In recent years, the frequency components of clocks used have been increasing due to the speeding up of digital electronic devices, and electromagnetic waves generated thereby have been strictly regulated in various countries. In order to reduce noise radiated in such an environment, a method of providing a guard conductor as shown in FIGS. 6 and 7 has conventionally been adopted. FIG. 6 is a schematic perspective view showing a conventional method for reducing electromagnetic waves in a printed wiring board.
FIG. 7 is a sectional view taken along line YY of FIG.

Conventionally, as shown in FIGS. 6 and 7, along a high-frequency wiring 62 provided on a substrate 61 of a printed wiring board,
A method of reducing the current loop area by arranging a return current wiring such as the guard conductor 65 and setting the potential of the guard conductor 65 to GND or the power supply potential has been adopted.

[0004]

However, as the signal frequency of the electronic equipment is further increased, the effect of reducing the radiated electromagnetic wave is reduced by using the conventional guard conductor alone. Therefore, it is desirable to increase the electrode area. However, on the other hand, as the density of the wirings increases, the guard conductor is required to be more compact, and there is a strong demand for a method for achieving the object without increasing the bottom surface area of the guard conductor.

An object of the present invention is to provide a printed wiring board having a large effect of reducing electromagnetic waves and a small bottom surface area of a guard conductor.

[0006]

According to the printed wiring board of the present invention, a guard conductor for returning a high-frequency current is laid along at least one side of the high-frequency wiring along a high-frequency wiring through which a high-frequency signal flows. In the printed wiring board, the guard conductor is formed such that the height from the substrate surface of the printed wiring board to the top surface of the guard conductor is higher than the height from the top surface of the high-frequency wiring. .

The printed wiring board may be a multilayer printed wiring board having two or more layers, and the top surface of the guard conductor may be electrically connected to a conductor of an adjacent upper wiring layer. May be electrically connected to a top surface of a guard conductor provided in a lower wiring layer adjacent to a wiring layer in which a high-frequency wiring is present.

[0008] The guard conductor may be formed of only a conductive paste on the surface of the substrate of the printed wiring board, and may be formed on the metal conductor provided on the surface of the substrate of the printed wiring board. It may be formed of a conductive paste.

Preferably, the potential of the guard conductor is at least one of a GND potential and a power supply potential.

In the printed wiring board of the present invention, a guard conductor having a height higher than the wiring conductor is laid in the vicinity of the high-frequency wiring on the base material of the printed wiring board, so that the area of the bottom surface of the guard conductor is increased. Without the need to increase the capacitive or inductive electrical coupling between the high-frequency wiring and the guard conductor, reducing the high-frequency current flowing through the electrical coupling between the high-frequency wiring and the conductor other than the guard conductor. Because
By reducing the loop of the high-frequency current, electromagnetic wave noise radiated from the printed wiring board is reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the printed wiring board of the present invention will be described with reference to the drawings. FIG. 1 is a schematic perspective view of a printed wiring board according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line XX of FIG.

In FIGS. 1 and 2 showing a printed wiring board according to a first embodiment of the present invention, reference numeral 11 denotes a substrate of the printed wiring board, which is a glass epoxy material here. Reference numeral 12 denotes a conductor of the high-frequency wiring, reference numeral 13 denotes a guard conductor according to the present invention, and the height of the guard conductor 13 from the surface of the substrate 11 of the printed wiring board is guarded. It is formed to be higher than the height. The guard conductor 13 is 1 here.
The conductive paste is formed by applying and curing a conductive paste on a metal conductor represented by a copper foil indicated by reference numeral 4, and the guard conductor 13 has a GND potential here.

Here, the guard conductor 13 is a metal conductor 14
The substrate 1 of the printed wiring board
1 may be directly formed on the surface of the substrate 1 and the material is not limited to the conductive paste, but may be any conductive material.
Although the guard conductor is set at the GND potential here, it may be set at the power supply potential.

FIG. 3 is a schematic diagram for explaining the effect of reducing the electromagnetic noise of the printed wiring board according to the first embodiment of the present invention. In the figure, Cl represents the capacitive coupling between the high-frequency wiring 32 and the guard conductor 33 according to the present invention, and C2 represents the capacitive coupling between the high-frequency wiring 32 and the conventional guard conductor 35. C3 represents a capacitive coupling between the high-frequency wiring 32 when the present invention is implemented and the other conductor 36 adjacent to the guard conductor, and C4 is a high-frequency wiring 32 when the conventional guard conductor 35 is used. And the other conductor 36 adjacent to the guard conductor. The reference numeral 31 indicates a substrate of a printed wiring board.

Here, in the first embodiment of the present invention, since the height of the guard conductor 33 is formed higher than the height of the guard conductor 35 of the conventional example, the electrode area is reduced even if the bottom area is the same. The coupling capacity becomes Cl> C2 due to the difference in electrode area, and C3 <C4 due to the shielding effect due to the difference in height.

Therefore, the guard conductor 33 according to the present invention can be used.
It can be understood that, by providing, the high-frequency current flows more intensively in the guard conductor 33 than in the conventional guard conductor 35, so that the current loop area is reduced and the radiation of electromagnetic waves is reduced.

Next, a second embodiment of the present invention will be described. FIG. 4 is a schematic sectional view of a printed wiring board according to a second embodiment of the present invention, in which the present invention is applied to a printed wiring board having a multilayer structure.

In the second embodiment, a high-frequency wiring 42 is provided in addition to the structure of the first embodiment including a printed wiring board substrate 41, a high-frequency wiring 42, a metal conductor 44, and a guide conductor 43. Material 47 laminated from the layers
The shield effect is further enhanced by making electrical connection between the conductor 48 provided in the layer above and the guard conductor 43. Here, the guard conductor 4 according to the present invention
3 contacts the metal conductor 48 provided on the laminated substrate material 47 under the pressure for laminating and pressing the laminated substrate material 47, thereby achieving electrical conduction.

With this structure, the shielding effect on the upper side is further enhanced, and the guard conductor 43 and the upper conductor 4
Since the high-frequency current to 8 is further concentrated and the current loop is reduced, the radiation of electromagnetic waves is reduced.

Next, a third embodiment of the present invention will be described. FIG. 5 is a schematic sectional view of a printed wiring board according to the third embodiment of the present invention, which is another example applied to a printed wiring board having a multilayer structure.

In the third embodiment, in addition to the structure of the second embodiment, the high-frequency wiring 52 is provided in a layer below the laminated substrate material 57 from the layer in which the high-frequency wiring 52 is provided. By forming the guard conductor 56 according to the present invention on the conductor 59 and connecting the top surface and the bottom surface of the guard conductor 53 via the metal conductor 54, the high-frequency wiring 52 has the same potential as the guard conductor 53 around the periphery. The guard conductor 53, the metal conductor 54, the guard conductor 56, the conductor 58, and the conductor 59 are completely covered. With this structure, the shielding effect is further strengthened, so that the high-frequency current can be further transmitted to the guard conductor 5.
3. Concentration on the metal conductor 54, the guard conductor 56, the conductor 58, and the conductor 59, further reducing the radiation of electromagnetic waves.

[0022]

As described above, in the printed wiring board of the present invention, by arranging a guard conductor having a height higher than the high-frequency wiring conductor near the high-frequency wiring, the guard conductor is provided with the high-frequency wiring. Since the return current can be concentrated and the loop of the high-frequency current is reduced, there is an effect that the electromagnetic noise radiated from the printed wiring board can be reduced without increasing the projected area of the guard conductor.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along line XX of FIG.

FIG. 3 is a schematic diagram for explaining an electromagnetic noise reduction effect of the printed wiring board according to the first embodiment of the present invention.

FIG. 4 is a schematic sectional view of a printed wiring board according to a second embodiment of the present invention.

FIG. 5 is a schematic sectional view of a printed wiring board according to a third embodiment of the present invention.

FIG. 6 is a schematic perspective view showing a conventional method for reducing electromagnetic waves in a printed wiring board.

FIG. 7 is a sectional view taken along the line YY of FIG. 6;

[Explanation of symbols]

11, 31, 41, 51, 61 Printed wiring board base material 12, 32, 42, 52, 62 High frequency wiring 13, 33, 43, 53 Guard conductor according to the present invention 14, 44, 54 Metal conductor 35, 65 Conventional Guard conductor 36 Other conductor 47, 57 adjacent to guard conductor 47, 57 Stacked substrate material 48, 58 Conductor of layer adjacent above layer where high-frequency wiring is present 56 of layer adjacent below layer where high-frequency wiring is present Guard conductor according to the present invention formed on a conductor 59 Conductor in layer adjacent below layer where high-frequency wiring is present

Claims (6)

[Claims] 1. A printed wiring board in which a guard conductor for returning a high-frequency current is laid on at least one side of the high-frequency wiring along a high-frequency wiring through which a high-frequency signal flows. A printed wiring board, wherein the guard conductor is formed such that a height from a surface to a top surface of the guard conductor is higher than a height from the top surface of the high-frequency wiring. 2. The printed wiring board is a printed wiring board having a multilayer structure of two or more layers, and a top surface of the guard conductor is electrically connected to a conductor provided on an adjacent upper wiring layer. The printed wiring board according to claim 1. 3. The printed wiring board is a printed wiring board having a multilayer structure of two or more layers, wherein a bottom surface of the guard conductor is provided in a lower wiring layer adjacent to a wiring layer in which the high-frequency wiring is present. The printed wiring board according to claim 1, wherein the printed wiring board is electrically connected to a top surface of the guard conductor. 4. The printed wiring board according to claim 1, wherein the guard conductor is formed on the surface of the substrate of the printed wiring board using only a conductive paste. 5. The printed wiring board according to claim 1, wherein said guard conductor is formed of a conductive paste applied on a metal conductor provided on a surface of a substrate of said printed wiring board. 6. A printed wiring board, wherein the potential of the guard conductor is at least one of a GND potential and a power supply potential.