JPH0728146B2 - Mounting structure of printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Of an electronic unit in which a printed wiring board is housed in a metal casing,
The present invention relates to a mounting structure of a printed wiring board, and particularly to improvement of a ground connection. An object of the present invention is to provide a mounting structure of a printed wiring board in which the printed wiring board is reliably grounded to the housing and has high reliability for a long period of time. In an electronic unit in which a printed wiring board is housed in a metal casing, a through hole with a desired hole diameter for allowing a small screw to penetrate and a ground land is formed on the mounting surface side, and the lower end surface of the pipe body are opened. Each of the lower tongue pieces has an upper tongue piece opened on the upper end surface of the pipe body, and the pipe body is provided with an earth pipe fitted into the through hole, and the shaft portion of the machine screw is attached to the pipe body. The lower tongue piece is fitted and soldered to the step end surface of the stepped through hole provided on the bottom plate of the housing, the upper tongue piece is soldered to the earth land, and the head of the machine screw or A nut screwed to the machine screw , The small screw that is tightened in contact with the upper surface of the upper tongue, the printed wiring board through the spacer, and fixed configurations in the bottom plate.

[Industrial application field]

The present invention relates to a printed wiring board mounting structure of an electronic unit in which a printed wiring board is housed in a metal housing, and more particularly to improvement of ground connection.

As shown in FIG. 3, an electronic unit in which a printed wiring board 1 is housed and fixed in a shallow box-shaped housing 2 made of metal is often used for communication equipment and the like.

The printed wiring board 1 has the mounting surface 1A facing upwards,
It is housed in parallel with the bottom plate 2A of the housing 2, and a spacing pipe 6 is interposed between the back surface 1B of the printed wiring board 1 and the front surface of the bottom plate 2A so that four screws are provided at the four corners. Using bottom plate
It is fixed in the housing 2 by being fixed to 2A.

A lid 3 is attached to the opening of the housing 2. Further, such a signal circuit of the printed wiring board 1 is connected to the outside through a connector 4 provided on the side wall of the housing 2.

At this time, along with demands for downsizing of electronic units and speeding up of signals, there is a strong demand for stabilization of grounding of printed wiring boards and high-density mounting of circuit components.

[Conventional technology]

FIG. 3 is a sectional view showing a conventional printed wiring board mounting structure.

In FIG. 3, reference numeral 1 indicates that a circuit component (not shown) is mounted on the mounting surface 1A, a ground pattern 9 or the like is formed on the back surface 1B, and a desired gap is provided between the back surface 1B and the surface of the bottom plate 2A. The printed wiring board is fixed to the housing.

A through hole 10 having an inner diameter sufficiently larger than the outer diameter of the small screw 5 and connected to the ground pattern 9 is provided at a desired position of the printed wiring board 1. Then, each through hole 10 is provided with an earth land 11 on the mounting surface 1A.

Reference numeral 15 denotes a flanged pipe 15 made of copper-based metal that fits into the through hole 10. The height of the tubular portion of the pipe 15 is slightly larger than the thickness of the printed wiring board 1 (for example, 0.5 mm).

With the flanged pipe 15 inserted into the through hole 10, the lower end surface of the flange 15A is brought into close contact with the earth land 11, and the tip end surface of the flange 15A is brought into contact with the surface of the bottom plate 2A. The printed wiring board 1 is fixed to the housing by penetrating the hollow hole of the pipe 15 and screwing it into the screw hole of the bottom plate 2A.

Further, the earth land 11 and the flange 15A are soldered.

In addition, between the head of the machine screw 5 and the flange 15A, a washer 1
6 and the spring washer 17 are interposed, the flange 15A is plated with solder, and the washer 16 and the inner surface of the housing 2 are plated with gold.

As described above, by using the flanged pipe 15 whose height is larger than the plate thickness of the printed wiring board 1, the printed wiring board 1 is fixed to the housing by pressing the flange 15A of the flanged pipe 15 with the machine screw 5. is doing. Therefore, the pipe with flange
The tip surface of 15 is pressed against the surface of the bottom plate 2A, and an earth circuit consisting of the earth pattern 9-through hole 10, earth land 11, flanged pipe 15 and housing 2 is formed.

That is, the ground pattern and the housing are directly connected to each other using an L-shaped metal fitting or the like to form a ground circuit, while the spacing tubes 6 are used to mechanically fix the four corners of the printed wiring board to the housing. Compared to other means, in the mounting structure shown in FIG. 3, the printed wiring board 1 is fixed with machine screws 5, and a ground circuit is formed at each of the fixing points.

Therefore, not only is the number of ground circuits increased and grounding is more reliable, but also high-density mounting of circuit components is promoted.

Furthermore, there is an advantage that the small screws 5 are not limited to the four corners of the printed wiring board 1 and can be provided at desired positions where grounding is desired.

[Problems to be Solved by the Invention]

However, in the above conventional structure, since the tip of the flanged pipe is only pressed against the surface of the bottom plate, if the tightening force of the screw is loosened, the resistance of the ground circuit may increase, and after a long period of time. However, there is a possibility that the tip end surface of the flanged pipe may be oxidized and contact may be poor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a printed wiring board mounting structure in which the printed wiring board is reliably grounded to the housing and has high reliability over a long period of time. I am trying.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention, as shown in FIG. 1, has an electronic unit in which the printed wiring board 1 is housed in a metal casing 2 with a desired hole diameter through which the machine screw 5 is loosely inserted. The printed wiring board 1 is provided with a through hole 10 in which an earth land 11 is formed on the mounting surface 1A side.

Further, there is provided an earth pipe 30 having a lower tongue piece opened on the lower end surface of the pipe body and an upper tongue piece opened on the upper end surface of the pipe body, respectively, into which the pipe body portion can be fitted into the through hole 10.

Then, the shaft portion of the machine screw 5 is fitted into the pipe body, the lower tongue piece is soldered to the step end surface 21 of the stepped through hole 20 provided in the bottom plate 2A of the housing 2, and the upper tongue piece is attached to the earth land 11. The nut 25 soldered and screwed to the machine screw 5 contacts the upper surface of the upper tongue of the earth pipe 30, the machine screw 5 is tightened, and the printed wiring board 1 is fixed to the bottom plate 2A via the spacer 40. Shall be.

[Action]

As described above, the ground pipe 30 is fitted into the through hole 10, the machine screw 5 is fitted into the pipe body of the ground pipe 30 to fix the printed wiring board 1 to the housing 2, and the lower tongue piece of the ground pipe 30 is further fixed. Is soldered to the bottom plate 2A of the housing 2 and the upper tongue is soldered to the earth land 11 of the printed wiring board 1. Therefore, an earth circuit is formed for each fixed portion of the printed wiring board 1, and the number of earth circuits is increased to ensure earthing.

Further, even if the tightening of the small screw may be loosened or the ground pipe may be oxidized, the resistance value is stable without increasing the ground resistance.

〔Example〕

The present invention will be specifically described below with reference to the drawings. The same reference numerals denote the same objects throughout the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention, and FIG. 2 is a perspective view showing details of an earth pipe.

In Fig. 1, circuit parts are mounted on the mounting surface 1A
Printed wiring board 1 with ground pattern 9 formed on 1B
However, the electronic unit is configured by being housed and fixed in the shallow box-shaped housing 2 made of metal.

Reference numeral 10 is a through hole having an inner diameter into which the earth pipe 30 can be inserted and is arranged at a desired position on the printed wiring board 1.

Each through hole 10 is connected to the ground pattern 9 on the back surface 1B side, and an earth land 11 connected to the through hole conductor is provided on the mounting surface 1A side.

As shown in detail in FIG. 2, the thin earth pipe 30 made of copper-based metal is provided with a plurality of lower tongue pieces 32 that are horizontally opened by cutting the lower portion of the pipe body 31. Further, the upper part of the pipe main body 31 is dissected and several upper tongue pieces 33 opened horizontally are provided. Further, the ground pipe 30 is plated with solder.

The earth pipe 30 is made by pressing a copper-based metal plate,
The upper tongue piece may be arranged on one side edge and the lower tongue piece may be arranged on the other opposite side edge, and then the upper tongue piece may be wound into a pipe shape to be manufactured.

Returning to FIG. 1, the printed wiring board 1 is attached to the bottom plate 2A of the housing 2.
Corresponding to the through hole 10, a stepped through hole 20 is provided.

In addition, in the upper part of the stepped through hole 20, there is provided a counterbore recess into which a hollow disc-shaped spacer 40 made of copper-based metal is inserted and seated. There is a counterbore recess where the head is inserted and seated.

On the other hand, the spacer 40, the inner surface of the housing 2, and the washer 16 described later.
Are gold-plated.

To fix the printed wiring board 1 to the housing 2, the lower tongue piece 32 is used.
Insert the ground pipe 30 into the stepped through hole 20 with
The lower tongue piece 32 is seated on the stepped end face 21 of the stepped through hole 20, a solder ring is fitted to the pipe main body 31 and heated, and the lower tongue piece 32 is soldered to the bottom plate 2A by the solder reflow means.

At this time, the upper tongue piece 33 is assumed to be extended parallel to the axis of the pipe body 31 without being bent.

Then, the spacer 40 is externally fitted to the pipe main body 31, and the lower surface thereof is seated in the recessed portion, and the through hole 10 is attached to the pipe main body 31.
Then, the printed wiring board 1 is placed above the bottom plate 2A, and the lower end surface of the through hole 10, that is, the land of the end of the ground pattern 9 is brought into contact with the upper end surface of the spacer 40.

The shaft part of the machine screw 5 is fitted into the stepped through hole 20 with the head part facing downward, and the shaft part pipe main body 31 is further penetrated to form the earth pipe.
After opening the upper tongue piece 33 of the leg 30, the nut 25 is screwed to the threaded portion to fix the printed wiring board 1 to the bottom plate 2A.

Then, the upper tongue piece 33 is soldered to the earth land 11.

A washer 16 and a spring washer 17 are used on the head side of the machine screw 5 and the nut 25 side, respectively.

As described above, since the through holes are arranged at desired places on the printed wiring board and the printed wiring board is fixed by using the small screws, the printed wiring board is securely fixed, and the grounding circuit is fixed at each fixing portion. The number of grounding circuits is increased and the grounding is reliable.

Even if the earth pipe is oxidized, the earth resistance does not increase and the reliability of earthing is high.

Furthermore, the positions of the machine screws are not limited to the four corners of the printed wiring board, but can be provided at any desired position where the ground can be dropped, and the ground pattern and the housing can be formed using L-shaped metal fittings. Compared to other means of directly connecting to form a ground circuit, the mounting area of circuit components is large.

The printed wiring board may be fixed to the housing by screwing the threaded portion of the small screw into the screw hole of the bottom plate of the housing without using the nut.

〔The invention's effect〕

As described above, in the present invention, the lower portion of the earth pipe is soldered to the housing, and the upper portion is soldered to the earth land of the printed wiring board, respectively, and by using a small screw penetrating the earth pipe,
This is a printed wiring board mounting structure in which the printed wiring board is fixed to the housing. The printed wiring board is reliably grounded to the housing, has high reliability over a long period of time, and has high-density mounting of circuit components. It has a practically excellent effect in that it is promoted.

[Brief description of drawings]

1 is a sectional view of an embodiment of the present invention, FIG. 2 is a perspective view of an earth pipe, FIG. 3 is a sectional view of an electronic unit, and FIG. 4 is a sectional view of a conventional example. In the figure, 1 is a printed wiring board, 2 is a housing, 5 is a small screw, 9 is an earth pattern, 10 is a through hole, 11 is an earth land, and 15
Is a pipe with a flange, 15A is a flange, 16 is a washer, 17 is a spring washer, 20 is a stepped through hole, 21 is a step end surface, 25 is a nut,
30 is an earth pipe, 31 is a pipe body, 32 is a lower tongue piece, 33
Is an upper tongue, and 40 is a spacer, respectively.

Claims (1)

[Claims] 1. An electronic unit, in which a printed wiring board (1) is housed in a metal casing (2), has a desired hole diameter through which a machine screw (5) freely penetrates, and has an earth land (11) on the mounting surface (1A) side. ) Through hole (10)
And a lower tongue piece opened on the lower end surface of the pipe body, and an upper tongue piece opened on the upper end surface of the pipe body, and the pipe body is fitted into the through hole (10). (30), the shaft portion of the machine screw (5) is fitted in the pipe body, and the lower tongue piece is provided with a stepped through hole (2A) provided in the bottom plate (2A) of the casing (2). 20) is soldered to the step end face (21), the upper tongue is soldered to the earth land (11), and is screwed to the head of the machine screw (5) or the machine screw (5). The nut (25) that contacts the upper tongue is brought into contact with the upper surface of the upper tongue, and the machine screw (5) is tightened, so that the printed wiring board (1) is attached to the bottom plate (2A) through the spacer (40). A printed wiring board mounting structure characterized by being fixed.