JP2785502B2 - Printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed circuit board used for various electronic devices.

[0002]

2. Description of the Related Art In recent years, digital circuits have been widely used in electronic equipment. In digital circuits, since a pulse signal is handled, a harmonic component contained in the pulse signal is radiated out of the equipment, and a television or other device is used. An obstacle is given to radio equipment by radio wave interference (hereinafter referred to as interference). Conventionally, in order to reduce this interference, the entire printed circuit board incorporating a digital circuit is stored in a shield case (metal case for shielding), and a through capacitor is used to connect the internal circuit of the printed circuit board to an external circuit (FIG. 6). The structure as shown in FIG. 7 is used. As shown in these figures, the printed circuit board 14 is electromagnetically shielded from the outside by the shield case body 12 and the lids 13a and 13b. A through capacitor for electrical connection of circuits inside and outside the shield case and electromagnetic shielding is attached to the shield case by soldering, and printed circuit boards 15 and 16 are soldered to lead wires of the capacitor. These substrates are connected to the lead wire 17 and the connector 1
7 connects to an external circuit of the shield case.

[0003]

As described above, in the conventional method, a relatively expensive feedthrough capacitor is required for connecting circuits inside and outside the shield case, and the mounting structure and the connection method with the lead wire are required. There was a problem that the cost was high due to the complexity and poor workability.

The present invention solves the above-mentioned problem by electrically connecting a circuit on a printed circuit board housed in a shield case and a circuit outside the shield case without using a feedthrough capacitor. An object of the present invention is to provide a printed circuit board that reduces the emission of interference from internal circuits and leads connected to the circuits.

[0005]

Means for Solving the Problems The circuit inside and outside of the shield covering the printed circuit board is connected by an inner foil sandwiched between outer foils, and the periphery of the connection foil is surrounded by the same inner foil, and the surroundings are surrounded by the same inner foil. The present invention is characterized in that the inner foil and the outer foil are connected by a large number of through holes, and a part of the solder resist of the outer foil is deleted.

[0006]

According to the multilayer printed circuit board of the present invention, the connection between the circuit inside and outside the shield case covering the printed circuit board is realized without using a feedthrough capacitor and without impairing the shielding effect of the shield case. As a result, there is no need for the members and the cost for assembling work associated with the use of the feedthrough capacitor.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In the figure, the outer foil 2a connected to the internal circuit of the printed circuit board is connected to the inner foil 2 by a through hole 3a.
b, and further connected to an outer foil 2c to which a lead wire to an external circuit of the printed board is connected by a through hole 3b. The inner layer foil 2b, the upper and lower and left and right foils surrounding the same and connected to the ground of the circuit (hereinafter, the foil connected to the ground is referred to as a ground foil), and are arranged at an interval of about 2 mm connecting these ground foils. The through-capacitor having a small capacity is equivalently formed with the large number of through holes 3c to prevent the radiation of interference from the inner layer foil 2b.
Also, a part of the solder resist 5 of the upper and lower ground foils sandwiching the inner layer foil 2b is removed according to the shape of the end face of the shield case 6 which sandwiches the printed circuit board, and the ground foil and the shield case are brought into contact with a large area. This can prevent radiation of interference from the gap. This state is shown in FIG. Upper shield case 6
a and the lower shield case 6b sandwich the printed circuit board 4 and contact the ground foil of the board. The internal circuit of the shield case is connected to the external circuit via the inner layer foil and the connector 7. With such a structure, the radiation of interference from the internal circuit of the printed circuit board and the connection circuit to the external circuit can be significantly reduced without using a feedthrough capacitor.

[0008]

As described above, according to the printed circuit board of the present invention, the feedthrough capacitor and its mounting plate required for preventing the radiation of interference from the printed board, and the printed circuit board for connecting the feedthrough capacitor and an external circuit are provided. It can be eliminated, the number of members can be reduced, the assembling workability is improved, and the cost is significantly reduced.

[Brief description of the drawings]

FIG. 1 is a plan view of a foil and a through hole of each layer of a printed circuit board of the present invention (upper outer foil, inner foil, lower outer foil from above).

FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 of the printed circuit board.

FIG. 3 is a cross-sectional view showing a portion of the printed circuit board from which solder resist has been removed.

FIG. 4 is a plan view showing a portion where the solder resist is removed from the printed circuit board.

FIG. 5 is a partial perspective view of an assembly structure of a printed circuit board and a shield case in one embodiment of the present invention.

FIG. 6 is a top view of an assembly structure of a conventional printed circuit board and a shield case.

FIG. 7 is a cross-sectional side view of a conventional printed circuit board and shield case assembly structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printed board ground foil 2 Printed board circuit connection foil 3 Printed board through hole 5 Printed board solder resist

Claims (1)

(57) [Claims] 1. A first layer in which a printed wiring pattern of an electronic circuit and a first connection foil are formed inside a first ground foil of a printed board, and a first layer connected to the first connection foil by a through hole. Wherein the second circuit connection foil is formed of at least three layers, a second layer formed inside the second ground foil and a third layer having a third ground foil on the outside. The first ground foil is electrically connected to the second ground foil and the third ground foil through a large number of through holes provided around the connection foil, and the first ground foil is connected to the first ground foil.
Remove the solder resist according to the shape of the end face of the shield case to electrically connected to the shield case for shielding the electronic circuit portion to the first and third ground foil layer and an outer third layer, said first Cover the entire outer surface of the layer
The shield case is removed by the solder resist.
Soldered to the removed first ground, and
In front of the shield case that shields the entire area outside the third layer
Solder to the third ground where the solder resist was removed
A printed circuit board characterized by being attached .