JPH05335771A - Electromangetic wave shielding structure - Google Patents

Abstract

PURPOSE:To simplify the constitution of an electromagnetic wave shielding structure for an electronic circuit constituted of a printed board. CONSTITUTION:The part of a multilayer printed board 21 is electromagnetically shielded by metal cases 32 and 33 mounted on the multilayer printed board 21 and by a metal layer 30, which makes conductive the metal cases 32 and 33 and is uniformly formed in the multilayer printed board 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave shielding structure in an electronic circuit constructed by using a printed wiring board.

In an electronic circuit including a high frequency circuit constructed by using a printed wiring board, an electromagnetic wave shielding structure is adopted in order to electromagnetically shield the high frequency circuit part from other electronic circuit parts. There is a demand for simplification of the configuration.

[0003]

2. Description of the Related Art FIG. 5 is a sectional view for explaining a conventional structure. In FIG. 1, reference numeral 1 denotes a main printed wiring board, and various electronic components for constituting a high frequency circuit unit 2 and other circuits 3 such as a power supply circuit, a control circuit, an IF circuit, etc. are provided on the main printed wiring board 1. It is implemented.

The high-frequency circuit unit 2 includes a sub-printed wiring board 4 on which high-frequency components are mounted, a shield case (metal case) including a front cover 5, a back cover 6 and a frame 7.
It is housed inside and is fixed to the main printed wiring board 1 by screws 8 or the like. Electrical connection between the sub printed wiring board 4 and the main printed wiring board 1 is made via a connecting cable 9.

FIG. 6 is a cross-sectional view for explaining another conventional structure, which is different from the conventional structure shown in FIG. 5 in the following points. That is, a high frequency component is directly mounted on the main printed wiring board 1 to form a high frequency circuit without providing a sub printed wiring board, and electromagnetic shielding of the high frequency circuit portion prevents the front cover 5 and the frame body 7 from being mounted on the high frequency component mounting surface. It is made by attaching the back cover 10 to the main printed wiring board 1 from the side and attaching the back cover 10 from the side opposite to this side.

The back cover 10 has a plurality of protruding legs 11, and these legs 11 are in pressure contact with the frame body 7 in a state of penetrating a square hole or the like formed in the main printed wiring board 1. ..

[0007]

However, according to the above conventional structure, the high frequency circuit section is electromagnetically shielded from the low frequency circuit section by the shield case (metal case) including the front cover, the back cover and the frame. However, since the structure is complicated and the number of constituent parts is large, there are problems such as high cost, a large number of assembling steps, and a large occupied space.

The present invention has been made in view of the above points, and an object thereof is to provide an electromagnetic wave shielding structure having a simple structure.

[0009]

In order to solve the above problems, the following structure is provided. That is, a part of the multilayer printed wiring board is electromagnetically electromagnetically formed by a metal case attached to the multilayer printed wiring board and a metal layer electrically connected to the metal case and uniformly formed inside the multilayer printed wiring board. It is a structure that is shielded.

[0010]

According to the present invention, in order to electromagnetically shield a part (high-frequency circuit portion) of the multilayer printed wiring board, a part of the metal case is substituted with a metal layer formed inside the multilayer printed wiring board. .. Therefore, the structure is simpler than that of the conventional structure (a back cover of the conventional structure is unnecessary).
As a result, the cost can be reduced, the number of assembly steps can be reduced, and the occupied space can be reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of the essential part of an embodiment of the present invention.

The multilayer printed wiring board 21 has six pattern layers (L1 layer to L6 layer). The L1 layer and the L2 layer are used for low frequency circuits such as power supply circuits, control circuits and IF circuits.
The L3 layer is assigned to the shield, and the L4 layer, the L5 layer, and the L6 layer are assigned to the high frequency circuit.

A plurality of low frequency components 22 are mounted on the L1 layer, and the low frequency components 22 are connected by wiring patterns 23 formed on the L1 layer and the L2 layer and via holes 24 connecting these.

A plurality of high frequency components 25 are mounted on the L6 layer, and these high frequency circuit components 25 are connected by wiring patterns 26 formed on the L6 layer and the L5 layer and via holes 27 connecting them. ..

A ground pattern 28 for a high frequency circuit is formed on the L4 layer, and the ground pattern 28 is connected to the high frequency component 25 by a via hole 29 and other wiring patterns.

The L3 layer has a metal pattern 3 for shielding.
0 is formed uniformly over a relatively wide range. 31
Is a shield case (metal case) for electromagnetically shielding the high-frequency circuit section from the low-frequency circuit section. The shield case 31 includes a front cover 32 and a frame body 33. The front cover 32 is configured to fit into the upper portion of the frame body 33, and a plurality of protruding legs 34 are integrally formed on the lower side of the frame body 33.

On the other hand, the printed wiring board 21 is formed with a plurality of through holes, and the frame 33 has the legs 34 of the frame body inserted in these through holes. It is fixed to.

These through holes formed in the multilayer printed wiring board 21 are electrically connected to the metal pattern 30 of the L3 layer. The high frequency circuit section and the low frequency circuit section are connected by a wiring pattern 35 formed so as not to contact the frame body 33 and a through via 36 formed outside the shield case 31.

According to this embodiment, the high frequency circuit section is electromagnetically shielded from the low frequency circuit section by the front cover 32, the frame 33 and the metal pattern 30 formed on the L3 layer of the multilayer printed wiring board 21. Therefore, the structure is simpler than the conventional structure because there is no back cover.

Further, one side of the multilayer printed wiring board 21 in the stacking direction is a high-frequency circuit section and the other side is a low-frequency circuit section, so that the electronic circuit as a whole can be made compact.
FIG. 2 is a sectional view showing the structure of another embodiment of the present invention. In this embodiment, two layers 42 and 43 of the inner layers of the multilayer printed wiring board 41 are used as a metal layer for shielding, and the electromagnetic wave shielding effect can be improved by such a configuration. it can. Others are shown in Figure 1.
Since it is the same as the above-mentioned embodiment shown in FIG.

FIG. 3 is a sectional view showing the structure of still another embodiment of the present invention, and FIG. 4 is a plan view of the same. In this embodiment, metal layers 52, 53, 54 for shielding are formed on three layers of the inner layers of the multilayer printed wiring board 51, and three frame bodies 55, 56, 57 and these are fitted respectively. The front covers 58, 59, 60 are provided, and the legs of the frame body 55 are electrically connected to the metal layer 52, the legs of the frame body 56 are electrically connected to the metal layer 53, and the legs of the frame body 57 are electrically connected to the metal layer 54, respectively. However, such a structure can be adopted depending on the circuit configuration.

[0022]

Since the present invention is configured as described above, it has an effect of providing an electromagnetic wave shielding structure having a simple configuration.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of another embodiment of the present invention.

FIG. 3 is a sectional view of still another embodiment of the present invention.

FIG. 4 is a plan view of still another embodiment of the present invention.

FIG. 5 is a cross-sectional view of the prior art.

FIG. 6 is a cross-sectional view of another prior art.

[Explanation of symbols]

 21 multilayer printed wiring board 22 low frequency component 25 high frequency component 30 metal pattern (metal layer) 31 shield case 32 table cover 33 frame 34 leg

Claims (3)

[Claims] 1. A metal case (32, 32) for attaching a part of a multilayer printed wiring board (21) to the multilayer printed wiring board (21).
33) and a metal layer (30) electrically connected to the metal case (32, 33) and uniformly formed inside the multilayer printed wiring board (21)
The electromagnetic wave shielding structure is characterized by being electromagnetically shielded by. 2. The electromagnetic wave shielding structure according to claim 1, wherein the number of the metal layers is plural. 3. The electromagnetic wave shielding structure according to claim 1, wherein a plurality of the metal layers and the metal cases are provided, and the metal layers and the metal cases are independently conducted.