JPH10294588A - Shielding structure for high frequency circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new shielding structure in which a shielding case and a piece sub-substrate are disused by a method wherein an enclosing earth pattern is provided on the circumference of the high frequency circuit formed on the first layer of a multilayer printed substrate, and the protruding type rib, which is formed on the chassis main body, is pressed and fixed to the pattern. SOLUTION: The entire necessary circuit is formed without using the separate piece substrate such as a sub-substrate, etc., in this structure. Besides, by having the earth enclosing pattern part 4 provided on a substrate 2 and a partitioning protruding type rib 5 to come in contact by pressing using a chassis main body 1, on which the partitioning protruding type rib 5 is provided, without using a shielding case and a shielding plate, the unnecessary radiation from a high frequency circuit 3, the mutal interference between the high frequency circuit 3 and other circuit and the interference when a strong, electric field is exposed can be suppressed. At this time, it is important that the through holes 9, which are vertically formed from an enclosing earth pattern part 4, and the earthing point of one-point earth of a circuit 1 are separated between layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shield structure for a high-frequency circuit.

[0002]

2. Description of the Related Art Conventionally, when a high-frequency circuit is formed on a printed circuit board, as shown in FIG. 6, unnecessary radiation from the circuit section is suppressed, mutual interference with other circuit sections is suppressed, In order to obtain the effect of suppressing interference, etc., the VCO (Vo
The high-frequency circuit part that requires the above-mentioned effect, such as a stage controlled led oscillator, is separated from the mother board 21 provided with another high-frequency circuit part into a separate piece of substrate such as the child substrate 22 and the circuit is formed by the shield case 23. Even when a portion is shielded or the entire high-frequency circuit is formed on the same substrate, there is a need to shield the entire circuit around with a shield case or a shield plate.

[0003]

However, in such a configuration, the cost and the number of assembling steps required for the shield case or the shield plate are increased, the same disadvantages as described above by dividing into separate piece substrates, and the space factor are deteriorated (the connection factor is deteriorated). (For example, a space for soldering a connector and a shield case), and deteriorating the serviceability (the solder of the shield case must be removed and the child board must be removed).

An object of the present invention is to solve the above-mentioned problems of the conventional structure and to provide a new high-frequency circuit shield structure in which a shield case and a separate piece substrate are eliminated.

[0005]

According to the present invention, there is provided a shield structure for a high-frequency circuit according to the present invention, wherein a surrounding earth pattern is provided around a high-frequency circuit formed on a first layer of a multilayer printed circuit board, and a convex type formed on a chassis body. The rib is pressed against the pattern and fixed.

In the shield structure of a high-frequency circuit according to the present invention, the multilayer printed circuit board has a second layer having an earth pattern portion larger than at least the area of the high-frequency circuit, and a surrounding earth pattern of the first layer is provided. The ground pattern portion of the second layer is electrically connected to the first through-hole portion.

In a shield structure of a high-frequency circuit according to the present invention, a multilayer printed board is provided between a first layer and a second layer, and includes a third layer having an earth pattern portion. The ground point and the third layer are electrically connected by a second through hole.

[0008]

The surrounding earth pattern is provided around the high-frequency circuit formed on the first layer of the multilayer printed circuit board, and the convex rib formed on the chassis body is pressed against the pattern and fixed. Further, the multilayer printed board has a second layer having an earth pattern portion larger than at least the area of the high-frequency circuit, and the surrounding earth pattern of the first layer and the earth pattern portion of the second layer are formed in the first through hole. Electrical connection at the unit. The multilayer printed circuit board further includes a third layer disposed between the first and second layers and having a ground pattern including at least a projection surface of the high-frequency circuit. Are electrically connected at the second through-hole portion. As a result, a structurally closed ground loop is formed, and unnecessary radiation from the high-frequency circuit unit, mutual interference between the high-frequency circuit and other circuit units, interference when exposed to a strong electric field, and the like can be suppressed.

[0009]

FIG. 1 is an exploded partial perspective view showing an embodiment of a shield structure of a high-frequency circuit according to the present invention.
In FIG. 1, reference numeral 1 denotes a chassis main body (for example, aluminum die-cast) of a portable wireless device, and reference numeral 2 denotes a multilayer printed board fixed to the chassis main body 1 by fixing means such as screws. A circuit such as a high-frequency circuit 3 necessary for the function of the portable wireless device is mounted on the multilayer printed board 2, and a surrounding earth pattern 4 is formed around the high-frequency circuit 3. On the other hand, a convex rib 5 is integrally formed on the chassis body 1 at a position corresponding to the surrounding ground pattern 4 formed on the multilayer printed board 2.

FIG. 2 shows an example of the structure of the multilayer printed circuit board 2, in which a part of a four-layer printed circuit board is shown. In FIG. 2, the multilayer printed circuit board 2 includes a first layer L1 and a second layer L1.
It comprises a layer L2, a third layer L3, and a fourth layer L4, and each layer is electrically connected via a through hole. First layer L1
A circuit pattern (including the high-frequency circuit 3) required for the function of the portable wireless device is formed, and electric components such as chip resistors are mounted by soldering or the like. An auxiliary circuit pattern 6 is formed on the second layer L2, and an earth pattern 7 including at least a vertical projection surface of the entire circuit pattern of the high-frequency circuit 3 on the first layer L1 is formed on the third layer L3. 4 layers L4
Similarly, the high-frequency circuit 3 of at least the first layer L1
The earth pattern having an area larger than the area of the circuit pattern is formed.

The surrounding earth pattern 4 of the first layer L1
Is electrically connected to the ground pattern in the circuit pattern 6 of the second layer L2 and the ground pattern portion 8 of the fourth layer L4 through a plurality of through-hole portions 9, but is electrically connected to the ground pattern of the third layer L3. 7 is not connected at a high frequency.
(In FIG. 2, although the electrical connection by the through-hole portions 9 between the respective layers is on four sides of the surrounding ground pattern 4, only one side is shown and the other three sides are omitted.

In addition, a single earth point 10 having no change in potential is found in the earth pattern in the high-frequency circuit 3.
This one-point ground point 10 is electrically connected to the ground pattern 7 of the third layer L3 via the through-hole portion 11, but is not connected to the ground pattern 8 of the fourth layer L4 at a high frequency. . The ground pattern 7 of the third layer L3 and the ground pattern 8 of the fourth layer L4 are
2 (or an inductor (for example, a (copper foil) pattern that generates inductance)) through the through-hole portion 1
1, the third layer L3 and the fourth layer L4 have the same potential in DC but float in high frequency.

FIG. 3 is a schematic partial side view when the chassis main body 1 and the multilayer printed circuit board 2 are fixed.
2 shows a state in which the convex rib 5 formed in FIG.

FIG. 4 is a conceptual view of the structure of FIG. 1 as viewed from the side. The grounds of the circuits 3a and 3b constituting the high-frequency circuit 3 are used to obtain the required high-frequency reference potential of the circuit.
A side A is a chassis body (die-cast portion) 1, sides B and D are through holes 9, and a side C is a ground pattern portion 8 of the fourth layer L4 of the multilayer printed circuit board 2. Is shown. The side A (the chassis body 1) and the side C (the ground pattern portion 8 of the fourth layer L4) are electrically connected by the through-hole portion 9 to form the ground G2. The third layer L3 and the fourth layer L4 are connected by a high-frequency coil 12 and the like, and the ground pattern portion 7 of the third layer L3 is connected to a single ground point 10, so that the ground G1 is separated from the ground G2 by a high frequency. Float.

As can be seen from FIGS. 3 and 4, the high-frequency circuit 3 on the multilayer printed circuit board 2 is
The periphery is completely surrounded by the convex rib 5, the through-hole portion 9, and the ground pattern portion 8 of the fourth layer L4, and a structurally closed ground loop is formed.

As described above, in the above-described structure, the whole required circuit is formed on the multilayer printed circuit board without using a separate piece substrate such as a daughter board. Furthermore, without using a shield case or shield plate, the chassis body (rear die casting) provided with convex ribs for partitioning is used, and the ground surrounding pattern part and convex ribs for partitioning provided on the board are machined. When a contact is made with a specific pressure, a structurally closed ground loop is formed, the high-frequency circuit 3 can be floated from the ground loop at a high frequency, unnecessary radiation from the high-frequency circuit 3 and the high-frequency circuit 3 and other circuit parts Interference and interference during exposure to a strong electric field can be suppressed.
At this time, it is important to separate a through hole vertically lowered from the surrounding ground pattern portion and a ground point of one point ground of the circuit between layers.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiment shown in FIGS. 1 to 4 uses a multilayer printed circuit board having a four-layer structure. The first to fourth layers have the same structure, and the fifth layer L
5, a separate circuit wiring pattern or component mounting can be performed on the sixth and sixth layers L6, and the size and thickness of the device can be further reduced.

As described above, since the shield case can be eliminated, the following advantages can be obtained. 1. Reduction of material costs and man-hours. 2. Equipment downsizing due to space advantage,
Realization of thinner. Similarly, there is the following advantage in addition to the above advantage by eliminating the separate piece child substrate. 3. Improved reliability by reducing the number of connection points (connectors, soldering). 4. Improved serviceability due to simple structure. 5. Since the number of connection points is reduced and the signal flow approaches a closed signal flow on the entire board, unnecessary radiation of the entire device can be reduced.

[0019]

According to the present invention, a novel shield structure in which the shield case and the separate piece substrate required for the conventional shield structure are eliminated can be obtained.

[Brief description of the drawings]

FIG. 1 is an exploded partial perspective view showing an embodiment of a shield structure of a high-frequency circuit according to the present invention.

FIG. 2 is a structural example of a multilayer printed circuit board, showing a part of a four-layer printed circuit board;

FIG. 3 is a schematic partial side view when the chassis body and the multilayer printed circuit board of FIG. 1 are fixed.

FIG. 4 is a conceptual view of the structure of FIG. 1 as viewed from the side.

FIG. 5 shows another embodiment of the shield structure of the high-frequency circuit according to the present invention, showing a structural example of a six-layer printed circuit board.

FIG. 6 is a schematic configuration diagram showing an example of a shield structure of a conventional high-frequency circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Chassis main body 2 Multilayer printed circuit board 3 High frequency circuit 4 Surrounding earth pattern 5 Convex rib 6 Circuit pattern 7 Earth pattern 8 Earth pattern 9 Through hole 10 1 point earth point 11 Through hole

Claims (3)

[Claims] An enclosure ground pattern is provided around a high-frequency circuit formed on a first layer of a multilayer printed circuit board.
A shield structure for a high-frequency circuit, wherein a convex rib formed on a chassis body is pressed against the pattern and fixed. 2. The shield structure for a high-frequency circuit according to claim 1, wherein the multilayer printed circuit board has a second layer having an earth pattern portion larger than at least the area of the high-frequency circuit, and the surrounding earth pattern of the first layer. And a ground pattern portion of the second layer is electrically connected by a first through-hole portion. 3. The shield structure for a high-frequency circuit according to claim 2, wherein the multilayer printed circuit board includes a third layer having an earth pattern portion disposed between the first and second layers. Point ground point and the third layer
A shield structure for a high-frequency circuit, wherein the shield structure is electrically connected through a through hole.