JPH0372696A - Structure for mounting printed circuit board - Google Patents

Abstract

PURPOSE:To secure a printed circuit board to a bottom plate through a spacer by fastening the board with a small screw and a nut to be screwed to the head of a small screw or the screw in contact with the upper face of an upper tongue piece provided at a pipe body. CONSTITUTION:A ground pipe 30 having a lower tongue piece opened at its legs to the lower end face of a pipe body and an upper tongue piece opened at its legs to the upper end face of the body whose pipe body is inserted in a through hole 10 is provided. The shaft of a small screw 5 is inserted in the pipe body, the lower tongue piece is soldered to the stepped end face 21 of a stepped through hole 20 formed at the bottom plate 2A of a housing 2, the upper tongue piece is soldered to a ground land 11, a nut 25 to be screwed to the screw 5 is brought into contact with the upper face of the upper tongue piece of the pipe 30 to clamp the screw 5, and a printed circuit board 1 is secured to the bottom plate 2A through a spacer 40. Even if the screw is loosened or the ground pipe is oxidized, ground resistance is not increased, thus, its resistance value is stabilized.

Description

[Detailed Description of the Invention] [Summary] An electronic unit that houses a printed wiring board in a metal casing.
The purpose of the present invention is to provide a printed wiring board mounting structure that ensures reliable grounding of the printed wiring board to the casing and is highly reliable over a long period of time, especially with regard to improving the ground connection. In an electronic unit in which a printed wiring board is housed in a metal casing, a through hole with a desired hole diameter through which a machine screw loosely passes, with a ground land formed on the mounting surface side, and an open leg on the lower end surface of the pipe body. Each of the lower tongue pieces has an upper tongue piece spread on the upper end surface of the pipe body, and the pipe body is provided with an earth pipe that is fitted into the through hole, and the shaft of the machine screw is attached to the pipe body. When inserted, the lower tongue piece is soldered to the stepped end surface of the stepped through hole provided in the bottom plate of the housing, the upper tongue piece is soldered to the ground land, and the head of the machine screw or The nut screwed into the machine screw comes into contact with the upper surface of the upper tongue piece and the machine screw is tightened, thereby fixing the printed wiring board to the bottom plate via the spacer.

(Industrial Application Field) The present invention relates to a printed wiring board mounting structure of an electronic unit that houses a printed wiring board in a metal casing, and particularly relates to an improvement in ground connection.

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

The printed wiring board l is housed in parallel to the bottom plate 2A of the housing 2 with the mounting surface IA facing upward, and has a desired gap between the back surface IB of the printed wiring board 1 and the surface of the bottom plate 2A. It is fixed within the housing 2 by interposing the spacer tube 6 and fixing the four corners to the bottom plate 2A using machine screws 5.

Then, the lid 3 is attached to the opening of the housing 2.

Further, the signal circuits and the like of such a printed wiring board 1 are connected to the outside via a connector 4 provided on a side wall of the casing 2.

At this time, with the demand for smaller electronic units and higher signal speeds, there is a strong demand for more stable grounding of printed wiring boards and higher density packaging of circuit components.

[Conventional technology]

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

In FIG. 3, 1 is such that a circuit component (not shown) is mounted on the mounting surface IA, a ground pattern 9 etc. is formed on the back surface 1B, and a desired gap is formed between the back surface IB and the surface of the bottom plate 2A. This is a printed wiring board that is fixed to the housing.

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

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

Insert the flanged pipe 15 into the through hole 10, bring the lower end surface of the flange 15A into close contact with the earth land 11,
With its tip end in contact with the surface of the bottom plate 2A, the shaft of the machine screw 5 is passed through the hollow hole of the flanged pipe 15 and screwed into the threaded hole of the bottom plate 2A. l is fixed to the casing.

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

Note that a washer 16 and a spring washer 17 are interposed between the head of the machine screw 5 and the flange 15^, and the flange 1
5A is solder plated, and the inner surfaces of the washer 16 and the housing 2 are plated with gold.

As mentioned above, using the flanged pipe 15 whose height is larger than the 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. are doing.

Therefore, the end surface of the flanged pipe 15 is pressed against the surface of the bottom plate 2A, and the ground pattern 9 - through hole 10
- Earth land 11 - flanged pipe 15 casing 2 constitutes a ground circuit.

That is, the grounding circuit is constructed by directly connecting the grounding pattern and the casing using type 17 metal fittings, while the four corners of the printed wiring board are mechanically fixed to the casing using spacer tubes 6. Compared to other means, the mounting structure shown in FIG. 3 has a printed wiring board 1 fixed with a small screw 5, and a ground circuit is constructed at each fixed location.

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

Furthermore, there is an advantage in that the position where the small screws 5 are arranged is not limited to the four corners of the prehent wiring board 1, but can be provided at any desired position where it is desired to be grounded.

[Problem to be solved by the invention]

However, in the above conventional structure, only the tip of the flanged pipe is pressed against the surface of the bottom plate, so if the tightening force of the screw becomes loose, there is a risk that the resistance of the earth circuit will increase, and it will not last for a long time. Over time, the tip surface of the flanged pipe may become oxidized, leading to poor contact.

The present invention was created in view of the above points, and an object of the present invention is to provide a mounting structure for a printed wiring board that ensures reliable grounding of the printed wiring board to the casing and is highly reliable over a long period of time. It is said that

A through hole 10 having a desired hole diameter through which the through hole 5 freely passes and has an earth land 11 formed on the mounting surface IA side is provided in the printed wiring board l.

Further, an earth pipe 30 is provided, which has a lower tongue piece opened at the lower end surface of the pipe body and an upper tongue piece opened at the upper end surface of the pipe body, and the pipe body portion can be inserted into the through hole 10.

Then, the shaft portion of the machine screw 5 is inserted into the pipe body, the lower tongue piece is soldered to the stepped end surface 21 of the stepped through hole 20 provided in the bottom plate 2^ of the housing 2, and the upper tongue piece is soldered to the stepped end surface 21 of the stepped through hole 20 provided in the bottom plate 2^ of the housing 2. The nut 25 that is soldered to the machine screw 5 and screwed onto the machine screw 5 comes into contact with the upper surface of the upper tongue piece of the earth pipe 30, and 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 carried out.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an electronic unit in which a printed wiring board l is housed in a metal housing 2, as illustrated in FIG. , insert the earth pipe 30 into the through hole 10, insert the small screw 5 into the pipe body of the earth pipe 30 to secure the printed wiring board l to the housing 2, and then attach the lower tongue piece of the earth pipe 30 to the housing 2. The upper tongue piece is soldered to the ground land 11 of the printed wiring board 1 on the bottom plate 2A of the board. Therefore, a grounding circuit is constructed at each fixed location on the printed wiring board 1, increasing the number of grounding circuits and ensuring reliable grounding.

Further, even if the tightening of the small screw loosens or the earth pipe becomes oxidized, the earth resistance does not increase and its resistance value remains stable.

(Example) The present invention will be specifically described below with reference to the drawings.The same reference numerals indicate 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 the earth pipe.

In FIG. 1, a printed wiring board 1 on which circuit components are mounted on a mounting surface IA and a ground pattern 9 formed on a back surface IB is housed and fixed in a shallow box-shaped casing 2 made of metal. unit is configured.

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

Each through hole 10 is connected to the ground pattern 9 on the back surface IB side, and a ground land 11 connected to the through hole conductor is provided on the mounting surface IA side.

As shown in detail in FIG. 2, the thin-walled earth pipe 30 made of copper-based metal is constructed by cutting off the lower part of the pipe body 31 and providing several lower tongue pieces 32 with legs spread horizontally. Furthermore, the upper part of the pipe body 31 is cut to provide several upper tongue pieces 33 whose legs are spread horizontally. Further, the earth pipe 30 is solder plated.

The earth pipe 30 is made by pressing a copper metal plate, arranging an upper tongue piece on one side edge and arranging a lower tongue piece on the opposite side edge, and then winding it into a pipe shape. It can also be manufactured.

Returning to FIG. 1, the bottom plate 2A of the housing 2 has stepped through holes 2 corresponding to the through holes 10 of the printed circuit board 1.
0 is set.

Note that, 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, and furthermore, in the lower part of the stepped through hole 20, a small hole 5 is provided.
A countersunk recess is provided for the head to be inserted and seated.

On the other hand, the spacer 40. The inner surface of the casing 2 and a washer 16, which will be described later, are each plated with gold.

To fix the printed wiring board 1 to the housing 2, use the lower tongue piece 3.
Insert the earth pipe 30 into the stepped through hole 20 with the earthing pipe 30 facing downward, the lower tongue piece 32 is seated on the stepped end surface 21 of the stepped through hole 20, and a solder ring is fitted into the pipe body 31 and heated to produce solder reflow means. The lower tongue piece 32 is soldered to the bottom plate 2A.

At this time, the upper tongue piece 33 is not bent but is extended parallel to the axis of the pipe body 31.

Then, by fitting the spacer 40 onto the pipe main body 31 and seating the spacer 40 in the hollowed-out recess, and fitting the through hole 10 into the pipe main body 31, the printed wiring Fi1 is connected to the bottom F.
i. Place the upper part of 2A, and bring the lower end surface of the through hole 10, that is, the land at the end of the ground pattern 9, into contact with the upper end surface of the spacer 40.

With the head facing down, insert the shaft of the rice cooker 5 into the stepped through hole 20, and then pass it through the shaft pipe body 31. After opening the upper tongue piece 33 of the earth pipe 30, The printed wiring board 1 is fixed to the bottom plate 2A by screwing a nut 25 into the bottom part.

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

Note that 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 mentioned above, through-holes are provided at desired locations on the printed wiring board and the printed wiring board is fixed using small screws, so the printed wiring board is securely fixed, and the ground circuit is connected to each fixed location. , the number of grounding circuits increases and grounding is reliable.

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

Furthermore, the machine screws can be installed not only at the four corners of the printed wiring board, but also at any desired position where you want to drop the ground, and by connecting the earth pattern and the casing using L-shaped fittings, etc. Compared to other means of configuring a ground circuit by direct connection, the mounting area for circuit components is large.

Note that the printed wiring board may be fixed to the casing by screwing the threaded portion of the machine screw into the threaded hole in the bottom plate of the casing, without using nuts.

〔Effect of the invention〕

As explained above, in the present invention, the lower part of the earth pipe is soldered to the casing, the upper part is soldered to the earth land of the printed wiring board, and a small screw is used to penetrate the earth pipe.
This is a printed wiring board mounting structure in which the printed wiring board is fixed to the housing, ensuring reliable grounding of the printed wiring board to the housing, high reliability over a long period of time, and high density mounting of circuit components. This has an excellent practical effect in that it promotes innovation.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention; Figure 2 is a perspective view of the earth pipe. Figure 3 is a cross-sectional view of the electronic unit. FIG. 4 is a sectional view of a conventional example. In the figure, 1 is a printed wiring board, 2 is the housing, 5 is a machine screw, 9 is an earth pattern, 10 is a through hole, 11 is Earthland, 15 is a pipe with flanges, 15A is a flange, 16 is a washer; 17 spring washer, 20 is a stepped through hole; 3 4 21 is the step end surface; 25 is Natsuto, 30 is the earth pipe, 31 is the pipe body, 32 is the lower tongue piece; 33 is the upper tongue piece; 40 each indicates a spacer. 863

Claims (1)

[Claims] In an electronic unit in which a printed wiring board (1) is housed in a metal casing (2), a mounting surface (1A) is provided with a desired hole diameter through which a machine screw (5) passes loosely.
A through hole with an earth land (11) formed on the side (
10), a lower tongue piece with open legs on the lower end face of the pipe body, and an upper tongue piece with open legs on the upper end face of the pipe body, and the pipe body is fitted into the through hole (10). an earth pipe (30), the shaft of the machine screw (5) is fitted into the pipe body, and the lower tongue piece is inserted into the stepped penetration provided in the bottom plate (2A) of the housing (2). It is soldered to the step end surface (21) of the hole (20), the upper tongue piece is soldered to the ground land (11), and the head of the machine screw (5) or the machine screw (5) is soldered. The nut (25) to be screwed is in contact with the upper surface of the upper tongue piece and the machine screw (
5) is tightened, the printed wiring board (1)
is fixed to the bottom plate (2A) via a spacer (40).