JPH0897578A - Print-wiring device - Google Patents

Abstract

PURPOSE: To obtain a print-wiring device which does not malfunction even when the capacitance of a capacitor formed between printed wiring and shielding member is reduced and the shielding member is provided adjacently to the printed wiring. CONSTITUTION: After a shielding member 2 is formed of a conductive metallic material and a printed board 4 equipped with printed wiring 6 in parallel with the member 2 is provided, the board 4 and member 2 are united in one body by making the distance between the wiring 6 and the part of the member,2 corresponding to the wiring 6 larger or making the capacitance between the wiring 6 and member 2 substantially smaller by forming a through hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring device which reduces the influence of capacitance.

[0002]

2. Description of the Related Art In a printed wiring device, a printed wiring made of the same thin foil is formed on a flat surface portion of an insulating plate to form a printed circuit board, and components for forming a circuit and external wiring are soldered to the printed circuit board. Attached and fixed in place. Such a printed wiring device is often shielded so as not to interfere with other circuits, in which case a shielding member such as an iron plate parallel to the printed circuit board is often interposed. However, the printed wiring device mounts the component on one side of the printed circuit board where the printed wiring is not applied, and penetrates the printed circuit board to extend the connection line of the component and the pin for connection to the other side to connect to the printed wiring. ing.
For this reason, since the printed wiring is uniformly applied to the other surface of the insulating plate, the surface of the printed wiring and the shielding member come close to each other in parallel, and a capacitor is formed between them. It will have a constant capacitance. When such a capacitor is configured, a circuit on the printed wiring may be short-circuited via the capacitor, or a malfunction may occur in combination with the stray capacitance. Then, when the impedance of the circuit becomes higher, such a malfunction tends to occur. Further, since the printed wiring is composed of a foil film, it is necessary to increase the width in the portion where the cross-sectional area is small and the current capacity is large. In such a configuration, the facing area with the shielding member is small. Since it becomes larger, the capacitance becomes larger.

Further, when such a shielding member is adjacent to the printed wiring, when a withstand voltage test or the like is performed between the circuit of the printed wiring and the shielding member, the shielding member and the tip of a pin or the like are attached. During that time, a breakdown voltage will occur. Pins such as parts mounted on the printed circuit board are projected irregularly, which results in irregular breakdown voltage resistance, which is not easy to manage in manufacturing. Of course, in order to prevent such a breakdown voltage defect, it is possible to prevent the breakdown voltage defect by interposing an insulating member between the shielding member and the printed wiring, but the weight and size increase,
In addition, the material is required, and the labor for assembling and assembling is required, which is a factor of increasing the manufacturing cost.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and reduces the capacitance of a capacitor formed between a printed wiring and a shielding member to reduce the printed wiring. An object of the present invention is to provide a printed wiring device that does not cause a malfunction due to electrostatic capacitance even if a shielding member is provided adjacently.

[0005]

According to the present invention, a shield member is formed of a conductive metal material, a printed circuit board having a printed wiring parallel to the shield member is provided, and a portion of the shield member facing the printed wiring is provided. The problem is solved by increasing the distance between the two or by forming a through hole to substantially reduce the capacitance between the printed wiring and the printed wiring board and the shielding member. are doing.

[0006]

With the through hole formed in the shielding member, the area facing the printed wiring is reduced, and the electrostatic capacitance of the capacitor formed between the printed wiring and the printed wiring is substantially reduced. The formation of unnecessary capacitors is substantially eliminated. In forming the capacitor, the electrostatic capacitance is determined by the distance or the area of the space in the portion where the printed wiring and the shielding member face each other.
Realized by reducing the area where the shielding member and the printed wiring are facing each other substantially by the through hole,
In addition, the electrostatic capacitance can be reduced by increasing the distance between the shield member and the printed wiring only in the portion facing the printed wiring, and regarding the portion where the capacitor is not formed between the shield and the printed wiring, The distance between the printed circuit board and the mounting portion can be reduced, and the printed circuit board can be easily mounted.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the embodiments shown in the drawings. FIG. FIG. 2 is a perspective view showing an embodiment of the shielding member. FIG. 3 is a perspective view showing another embodiment of the shielding member. FIG. 4 is a perspective view showing another embodiment of the shielding member. FIG. 5 is a vertical cross-sectional view of a main part showing another embodiment. FIG. 6 is a circuit diagram of a main part showing the circuit configuration of the printed wiring.

In FIG. 1, the printed wiring device is constructed by attaching a printed circuit board 4 to a shielding member 2 fixed inside a case 1 via a leg portion 3. The shielding member 2 is formed in a plate shape with a conductive metal material such as a copper plate, an iron plate, or aluminum, and is fixed to the case 1. Such a shielding member 2 is a printed circuit board 4
And a partition inside the case 1 is formed. Further, a large number of components 5 such as ICs, capacitors or resistors are mounted on one surface of the printed circuit board 4, and printed wiring 6 is provided on the other surface of the printed circuit board 4 and the components 5 are mounted on the other surface. The pin 7 and so on are protruding. Such a printed circuit board 4 is connected to another device (not shown), and the shielding member 2 is fixed to the case 1 and grounded.

In FIG. 2, the shield member 2 of the printed wiring device is provided with screw holes 8 at its four corners so that the printed circuit board 4 can be supported on the outer peripheral portion through the legs 3. The portion facing the printed wiring 6 is formed of a large through hole 9.

In FIG. 3, the shielding member 2a is provided with screw holes 8a at its four corners, and a large number of through holes 10 are formed in a portion of the printed circuit board 4 which faces the printed wiring 6, which is substantially formed. The area is small. Such a large number of through holes 10 may be formed by bending a member, which is generally called a punch metal, in which a large number of small through holes are formed in advance.

In FIG. 4, the shielding member 2b is provided with screw holes 8b at its four corners, and a large recess 11 is formed in a portion of the printed board 4 facing the portion of the printed wiring 6 and the screw hole 8b is formed. When the leg portion 3 is attached and the printed circuit board 4 is attached, the distance between the facing portion of the printed wiring 6 and the shielding member 2b is increased.

In FIG. 5, the shielding member 2a is attached to the case 1a.
The printed circuit board 4 is attached to the shielding member 2a so as to face both sides of the shielding member 2a. The shielding member 2a has a large number of through holes 10 in a portion facing the printed wiring 6. Has been formed.

In FIG. 6, wiring 12 is provided on a circuit component 5 such as an IC or a resistor, and the wiring 12 is formed by the printed wiring 6 on the printed board 4. Since the wiring 12 is composed of the printed wiring 6 having a constant width, the shielding member 2
A capacitor 13 is formed between

In such a structure, in the printed wiring device, the shield member 2 is attached to the case 1, and the shield member 2 is attached.
The printed circuit board 4 is attached to the through the leg portion 3. The printed circuit board 4 thus mounted has a predetermined distance from the shield member 2, and the capacitor 13 is formed between the printed circuit board 6 and the printed wiring 6 as shown in FIG. However, since the through hole 9 is formed in the portion of the shielding member 2 that faces the printed wiring 6, the capacitance thereof is negligible, and the capacitor 1 is substantially disposed.
3 is not formed. Such a shielding member 2 is convenient for supporting the printed circuit board 4 via the leg portions 3 because the through hole 9 can be formed in the portion formed by leaving the outer periphery, but it is electromagnetically shielded. Therefore, when electromagnetic shielding is required, a large number of small through holes are formed as in the shielding member 2a according to another embodiment, or the recess 11 is formed to form the printed wiring 6 and the shielding member 2b. It is preferable that the capacitance of the capacitor 13 formed between them is substantially reduced.

By forming a small through hole 10 in the shielding members 2a, 2b or by forming a recess 11 to increase the distance from the printed wiring 6, the electrostatic capacitance is substantially reduced by the nature of the capacitor 13. This is the effect obtained above, and the capacitance of the capacitor 13 between the printed wiring 6 and the shielding member 2 can be surely reduced.

That is, the capacitance of the capacitor 13 is
This is because they are inversely proportional to the mutual distance between the facing conductive metal members and directly proportional to the facing area.
3 The theory of formation is used.

Further, when the two printed circuit boards 4 shown in FIG. 5 are provided in parallel, the two printed circuit boards 4 can be configured so as not to interfere with each other through the shield member 2a. , The shielding member 2a in common, the shielding member 2
The printed circuit boards 4 may be attached to both surfaces of a via the leg portions 3, respectively. In such a configuration, the shielding member 2a shields the mutual interference of the two printed circuit boards 4 by shielding them from each other, and as shown in FIG. In the case of the shield member 2 to be provided, since the distance between the two printed circuit boards 4 is twice the distance to the shield member 2, the shield members 2a and 2b according to the other embodiments are particularly used when electromagnetic shielding is not required. Can be used similarly to.

Since the shielding members 2, 2a, 2b as described above can surely hold the printed circuit board 4 and partition the inside of the case 1, a preferable structure for a printed wiring device is obtained. be able to.

[0019]

According to the present invention, by reducing or eliminating the electrostatic capacitance formed between the shielding member and the shielding member formed on the printed wiring of the printed circuit board, troubles such as malfunction of the printed wiring can be avoided. Since the distance between the shielding member and the printed circuit board can be reduced, the entire printed wiring device can be downsized, and its effect is remarkable.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a main part showing an embodiment of a printed wiring device according to the present invention.

FIG. 2 is a perspective view showing an embodiment of a shielding member.

FIG. 3 is a perspective view showing another embodiment of the shielding member.

FIG. 4 is a perspective view showing another embodiment of the shielding member.

FIG. 5 is a vertical cross-sectional view of a main part showing another embodiment.

FIG. 6 is a circuit diagram of a main part showing a circuit configuration of a printed wiring.

[Explanation of symbols] 1 ………… Case 2 ………… Shielding member 3 ………… Legs 4 ………… Printed circuit board 6 ………… Printed wiring 7 ……… Pin 8 ……… Screw hole 9 ……… Transparent Hole 10 ………… Through hole 11 ………… Recessed portion 13 ……… Capacitor

Claims (1)

[Claims] 1. A shield member is formed of a conductive metal material, a printed circuit board having a printed wiring parallel to the shield member is provided, and a distance of a portion of the shield member facing the printed wiring is increased, or A printed wiring device comprising a through hole formed so as to substantially reduce electrostatic capacitance between the printed wiring and the printed circuit board and the shielding member.