JP2001230504A - Flexible wiring board and its connection structure to circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detection of disconnections in a flexible wiring board, using a simple construction in a connection structure of the flexible wiring board to a circuit board. SOLUTION: In a connection structure, the flexible wiring board 10, where a wiring part 12 for a signal is formed on an insulating main board 11 having flexibility, is connected with a printed board 20 as a circuit board. A wiring part 13 for detection, which is independent of the wiring part 12, is formed on the main board 11, and a disconnection detecting circuit 22, which generates a signal when the wiring part 13 is disconnected, is formed on the printed board 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible wiring board used for connecting a circuit board, and a structure for connecting the flexible wiring board to the circuit board.

[0002]

2. Description of the Related Art A flexible wiring board (FPC) is formed by forming signal wiring on a flexible and insulating main body substrate such as polyimide or the like, and is used for connecting circuit boards. This flexible wiring board may be disconnected due to vibration or the like, and it is necessary for a high-quality electronic device to detect an abnormality by a self-diagnosis function.

Conventionally, there is an electronic device having a self-diagnosis function for detecting disconnection of a flexible wiring board. This is realized by detecting that a specific signal output (voltage or frequency) changes when each signal wiring is disconnected.

[0004]

However, in the above-described conventional disconnection detecting method, a circuit scale for detecting a change in a specific signal output becomes large, sufficient detection accuracy is not obtained, or a disconnection cannot be detected. It has been difficult to detect disconnection efficiently, for example, when there is a signal.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a structure for connecting a flexible wiring board to a circuit board, which makes it possible to detect disconnection of the flexible wiring board with a simple structure.
It is another object of the present invention to provide a flexible wiring board suitable for such a connection structure.

[0006]

According to the present invention, since a disconnection of a signal wiring portion in a flexible wiring substrate occurs from an end portion, a wiring reflecting a crack in the main substrate to an electric signal is provided on the main substrate as a dummy. It is made by paying attention to performing disconnection detection of the flexible wiring board by forming the dummy wiring and detecting the disconnection of the dummy wiring.

That is, according to the first aspect of the present invention, the signal wiring portion (1) is provided on the flexible insulating main body substrate (11).
The flexible wiring board (10) formed by 2) is
In the connection structure connected to the circuit board (20), the detection wiring portion (1
3) forming a disconnection signal generating circuit means (22) for generating a signal when the detection wiring section is disconnected on the circuit board;
Is formed.

According to this, a detection wiring portion as a dummy wiring is formed on the main substrate of the flexible wiring substrate, and a disconnection signal generating circuit means for generating a signal when the detection wiring portion is disconnected is formed on the circuit board. With this simple configuration, the disconnection of the flexible wiring board can be simulated by utilizing the disconnection of the detection wiring portion.

In particular, it is preferable that the detection wiring portion (13) is formed so as to surround the signal wiring portion (12) around the main body substrate (11).
According to the present invention, when the disconnection of the flexible wiring board occurs due to vibration or the like, the disconnection occurs first from the detection wiring portion located in the peripheral portion, so that the disconnection can be detected more reliably.

According to a third aspect of the present invention, there is provided a flexible wiring board, wherein a detection wiring section (13) independent of a signal wiring section (12) is formed on a main board (11). And a flexible wiring board suitable for the connection structure of claim 1 can be provided. Further, according to the fourth aspect of the invention, it is possible to provide a flexible wiring board suitable for the connection structure of the second aspect.

Note that the reference numerals in parentheses of the above means are examples showing the correspondence with specific means described in the embodiments described later.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is an explanatory diagram schematically showing a connection structure of a flexible wiring board to a circuit board according to an embodiment of the present invention. In the present connection structure, a printed circuit board (circuit board) 20 is circuit-connected to another printed board (not shown) via a flexible wiring board 10.

The flexible wiring board 10 includes a main board (base film) 11 made of a flexible insulating polyimide resin or the like, and a printed circuit board 20 formed on the main board 11 and the other printed board. And a signal wiring portion 12 made of Cu or the like for transmitting a signal.

A detection wiring portion 13 for disconnection detection, which is electrically independent of the signal wiring portion, is provided around the main body substrate 11.
Are formed of Cu or the like so as to surround the signal wiring portion 12. That is, the signal wiring section 12 is arranged so as to be located inside the detection wiring section 13.

On one end side of the flexible wiring board 10, the signal wiring section 12 and the detection wiring section 13 are connected to a printed board 20 via terminals 21, respectively. Although not shown, the flexible wiring board 1
On the other end side of the signal line 0, the signal wiring section 12 is electrically connected to the above-mentioned other printed circuit board via a terminal or the like. Thus, the two printed boards are circuit-connected via the signal wiring section 12.

The printed circuit board 20 has a disconnection detection circuit 2 as a disconnection signal generating circuit for generating a signal (disconnection detection signal S1) when the detection wiring section 13 is disconnected.
2 are provided. The disconnection detection circuit 22 is connected to the detection wiring section 13 of the flexible wiring board 10 and is a circuit including a pull-up resistor 23 and a buffer circuit 24 for amplifying a signal.

Here, one end of the pull-up resistor 23 is electrically connected between the detection wiring section 13 and the input side of the buffer circuit 24, and the other end is connected to a power supply (not shown). . The input side of the buffer circuit 24 is
It is grounded via the detection wiring section 13, and the output side outputs the disconnection detection signal S1.

The operation of this embodiment based on the above configuration will be described. FIG. 2 is a diagram when the flexible wiring board 10 is disconnected. FIGS. 3A and 3B are explanatory diagrams showing the operation of the present embodiment. FIG. 3A shows the state of the disconnection detecting circuit 22 before the disconnection occurs, and FIG. 3B shows the state of the disconnection detecting circuit after the disconnection occurs. FIG. 2C is a diagram showing a state of FIG. 22, and FIG. 2C is a diagram showing a state of a signal change of the disconnection detection circuit 22 due to the occurrence of disconnection.

As described above, since the disconnection of the flexible wiring board 10 is likely to occur from the end of the main board due to vibration or the like, the flexible wiring board 10 is cracked from the outside and proceeds, as shown in FIG. Then, a disconnection portion K1 occurs. Therefore, due to the cracks in the flexible wiring board 10,
The first disconnection is the detection wiring portion 13 located at the end of the main body substrate 11.

Disconnection detecting circuit 2 before disconnection K1 occurs
In the state 2 (normal state), as shown in FIG. 3A, the buffer circuit 24 is grounded via the detection wiring section 13, so that the disconnection detection signal S1 is "low level (L level). ) "(See FIG. 3C).

When a disconnection occurs (at the time of disconnection),
As shown in FIG. 3B, the buffer circuit 24 is no longer grounded, and the buffer circuit 24 includes a pull-up resistor 23.
Via the power supply (not shown).
Accordingly, the disconnection detection signal S1 becomes a "high level (H level)" having a value higher than the normal L level, and the disconnection can be detected by the generation of the H level signal.

As described above, according to the present embodiment, the detection wiring section 13 as a dummy wiring is formed on the main board 11 of the flexible wiring board 10, and the detection wiring section 13 is formed on the printed board (circuit board) 20. With the simple structure of simply forming a disconnection detection circuit (disconnection signal generation circuit means) 22 that generates a signal when a disconnection occurs, the disconnection of the flexible wiring board 10 is detected using the disconnection of the detection wiring unit 13. be able to.

The formation position of the detection wiring portion 13 on the flexible wiring board 10 may be formed at a position where disconnection is likely to occur, and in particular, it does not have to be formed anywhere on the main body substrate 11. However, usually, the disconnection is likely to occur from the peripheral portion (edge) of the main body substrate 11. Therefore, as in the present embodiment, the detection wiring portion 13 is connected to the signal It is preferable to form so as to surround the portion 12. Thereby, reliable disconnection detection becomes possible.

Further, in the present embodiment, there is provided a flexible wiring board 10 characterized in that a detection wiring section 13 independent of a signal wiring section 12 is formed on a main board 11. Is suitable for use in the connection structure shown in FIG. Note that the disconnection detection circuit 22 includes:
The configuration is not limited to the above example as long as it can electrically detect signals when the detection wiring section 13 is normal and when it is disconnected.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a connection structure of a flexible wiring board to a circuit board according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a state in which a flexible wiring board is disconnected.

FIG. 3 is an explanatory diagram showing an operation of the embodiment.

[Explanation of symbols]

10: flexible wiring board, 11: body board, 12 ...
Signal wiring section, 13: detection wiring section, 20: printed circuit board, 22: disconnection detection circuit.

Claims (4)

[Claims] An insulative body substrate (1) having flexibility.
1) and the signal wiring portion (1) formed on the main body substrate.
In the connection structure in which the flexible wiring board (10) having the configuration (2) is connected to the circuit board (20), the detection wiring part (13) independent of the signal wiring part is formed on the main body substrate. Connecting the flexible wiring board to the circuit board, wherein the circuit board is provided with a disconnection signal generation circuit means (22) for generating a signal when the detection wiring section is disconnected. Construction. 2. The detection wiring portion (13) is formed so as to surround the signal wiring portion (12) at a peripheral portion of the main body substrate (11). Connection structure for connecting a flexible wiring board to a circuit board according to the above. 3. A flexible wiring board which is used for connecting circuit boards and has a flexible insulating main body substrate (11) and a signal wiring portion (12) formed on the main body substrate. A flexible wiring board, wherein a detection wiring part (13) independent of the signal wiring part is formed on the main body substrate. 4. The detection wiring section (13) is formed so as to surround the signal wiring section (12) at a peripheral portion of the main body substrate (11). The flexible wiring board according to the above.