JPH05315790A - Shield structure for printed circuit board - Google Patents

Abstract

PURPOSE:To protect noise generated by a part of a circuit installed on a printed circuit board from negatively affectiang a circuit installed on another printed circuit board by fixing the open edge of a shield case to the peripheral section of the metal plate protruded from the periphery of the printed circuit board on the surface of which the part of the circuit which generates the noise is installed and by electromagnetically sealing the circuit which generates the noise in the shield case. CONSTITUTION:In a circuit unit for a telecommunication apparatus, in which the first prianted circuit board 4 is loaded with a logic circuit, while the lower surface of the second printed circuit board is loaded with a telecommunication circuit, open edge 7a of a shield case 7 is fixed to the peripheral section of a metal plate 6 in order to cover the whole lower surface of the second printed circuit board 5. Namely, the open edge 7a of the shield case 7 is airtightly fixed onto the peripheral section of the metal plate 6 by soldering, screw fastening, or the like manner. By this, a shield room is formed inside the shield case 7, a noise generated by the telecommunication circuit installed in the shield room can be protected from influencing the logic circuit on the first printed circuit board 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention shields noise emitted from various electronic parts on a printed circuit board to prevent interference with other circuits, or prevents external noise from entering the circuit on the printed circuit board. To improve the shield structure.

[0002]

2. Description of the Related Art Conventionally, a printed board having a joining structure in which two printed boards are joined together at their back surfaces to have circuits on both front and back surfaces has been widely used. FIG. 2 shows a conventional printed circuit board unit having a joint structure. The printed circuit board unit has a circuit pattern on one side and a conductor layer such as copper foil on the other side. It has a configuration in which the copper foil surfaces 3 are joined and integrated.
When a printed circuit board unit having such a joint structure is used as a circuit unit of a communication device, for example, a logic circuit is formed on one substrate 1 and a wireless circuit is formed on the other substrate 2, respectively. Is done.

By the way, the radio circuit includes an electronic component and a circuit which generate a high frequency, and when the generated high frequency noise enters the logic circuit side, it causes a malfunction. Conversely, if pulse noise or the like generated from the logic circuit mixes into the high frequency circuit, the S / N of the high frequency signal deteriorates. For this reason, a ground pattern has been conventionally formed around the high frequency generating part in the circuit, and this ground pattern is connected to the copper foil 3 through a through hole penetrating the substrate, and a shield case is provided at a required part. The method of shielding noise by covering is adopted.

However, according to such a conventional shielding method, it is necessary to previously form a ground pattern around the high frequency generating portion, which complicates the pattern configuration and reduces the mounting density of electronic components. Cause. Further, since it is only partially grounded to the copper foil having a small thickness through the through hole, the shield effect is often insufficient.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in a printed circuit board unit in which a plurality of printed circuit boards are joined back to back, noise generated by a mounting component on one substrate is generated on the other substrate. It is an object of the present invention to provide a shield structure for a printed circuit board, which can prevent a bad influence on a circuit and can obtain a high shield effect by a relatively simple structure.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a wide area metal plate having rigidity and a shield effect on the other surfaces of two printed boards each having a circuit pattern on one surface. By sandwiching and integrating, and by protruding part of the metal plate from the peripheral edge of the printed circuit board and fixing the opening edge of the shield case to this part, the circuit on the board is sealed in the shield case and noise is emitted to the outside. It is characterized by preventing this.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. 1 (a) and 1 (b) are an exploded sectional view showing an example of the structure of a printed board unit of the present invention and a sectional view showing a state in which a shield case is mounted. This printed board unit has a circuit pattern on an upper surface 4a. First
The non-patterned surface 4b of the printed circuit board 4 and the non-patterned surface 5b of the second printed circuit board 5 having the circuit pattern on the lower surface 5a are bonded by an adhesive or the like via a metal plate 6 having a high shield effect and rigidity. It is one that is joined and integrated.

The metal plate 6 has the first and second upper and lower surfaces joined together.
And has a larger area than the second printed circuit boards 4 and 5,
The peripheral portion 6a is configured to protrude like a flange with a predetermined width from the entire peripheral edge of each printed circuit board 4, 5. As the material of the metal plate 6, copper, aluminum or the like has a high shielding effect against high frequency signals, and iron, phosphor bronze or the like has a high electromagnetic shielding effect. Therefore, both of them may be used as necessary, but they may be laminated. When laminating the two, for example, iron-based chrome plating is applied to a copper plate,
On the contrary, it is conceivable to plate an iron plate with copper.

In this embodiment, the logic circuit is mounted on the first printed circuit board 4 and the second printed circuit board 5 is used.
2 illustrates an example of a circuit unit for communication equipment in which a wireless circuit is mounted on the lower surface of the second printed circuit board 5. The opening edge 7a of the shield case 7 is fixed to the peripheral edge portion 6a of the metal plate 6 to cover the entire lower surface of the second printed circuit board 5. Then, the entire lower surface of the substrate 5 is completely sealed. That is, the shield case 7 is hermetically fixed on the peripheral edge 6a of the metal plate 6 by the fixing method such as soldering or screwing to form a shield room inside the shield case 7. The noise generated by the wireless circuit in the room is prevented from reaching the outside, particularly the logic circuit on the first printed board.

In the above embodiment, each printed circuit board 4,
Although a single-layer structure is illustrated as 5, the printed circuit board itself may be composed of a plurality of layers. As described above, in the shield structure of the present invention, the back surfaces (pattern non-formation surfaces) of the two printed circuit boards are connected and integrated via the metal plate 6 having rigidity and the shield effect, By fixing the shield case using the peripheral portion of the metal plate protruding from the substrate, noise generated by the circuit sealed in the shield case is prevented from being emitted to the outside. Therefore, it is not necessary to previously form a ground pattern around the high frequency generating portion as in the conventional case, so that the pattern configuration can be simplified and the mounting density of electronic components can be improved. Furthermore,
Since the shield case is tightly fixed to the metal plate at the entire peripheral portion of the opening, the shield effect becomes sufficient.

Further, since the two substrates are joined together with the metal plate sandwiched therebetween, the strength of the entire substrate is improved and warpage and the like can be prevented, and the metal plate is heated by the heat-generating components on the substrate. Has the effect of radiating heat.

[0012]

As described above, according to the present invention, in a printed circuit board unit in which a plurality of printed circuit boards are joined back to back, noise generated by a mounting component on one of the substrates adversely affects a circuit on the other substrate. It is possible to obtain a high shielding effect with a relatively simple structure that can prevent the influence.

[Brief description of drawings]

1A and 1B are an exploded sectional view showing a configuration of an example of a printed board unit of the present invention and a sectional view showing a shield case mounted state.

FIG. 2 is an explanatory diagram of a conventional example.

[Explanation of symbols]

1, 4 First substrate, 2, 5 Second substrate, 3 Copper foil surface, 4a, 5a Circuit pattern surface, 4b, 5b Non-pattern surface, 6 Metal plate, 6a Peripheral part, 7 Shield case

Claims (2)

[Claims] 1. Two printed circuit boards having a circuit pattern on at least one side are attached to both sides of a metal plate, and
A part of the metal plate protrudes from the peripheral edge of the printed circuit board, and by fixing the opening edge of the shield case to the peripheral edge of the metal plate protruding from the peripheral edge of the printed circuit board, the circuit on the circuit board can be installed in the shield case. A shielded structure for printed circuit boards that is hermetically sealed. 2. The shield structure for a printed circuit board according to claim 1, wherein the metal plate is a copper plate plated with chromium, or an iron-based metal plate plated with copper or aluminum.