JP2003124583A - Flexible circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flexible circuit board which can prevent a crack from occurring in a conductor pattern and which has high reliability. SOLUTION: The flexible circuit board comprises an insulating resin film 2 having the conductor pattern 3 with a connecting terminal 3a formed to connect to a connector 10, and a reinforcing plate 6 fixed to correspond to the terminal 3a and provided on the rear surface of the forming surface of the pattern 3 of the film 2. The board further comprises a lining material 5 more flexible than the plate 6 and interposed between the film 2 and the plate 6 in such a manner that the material 5 protrudes in the opposite direction to the connector inserting direction (the direction of an arrow A) from the edge 5a of the plate 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible board, and more particularly to a flexible board with a reinforcing plate.

[0002]

2. Description of the Related Art FIG. 10 is a sectional view of a conventional flexible substrate of this type. As shown in the figure, in this flexible substrate 41, a conductor pattern 43 is formed on one surface of a strip-shaped insulating resin film 42, and a resist layer 44 is provided so as to cover the conductor pattern 43. The end portion is exposed from the resist layer 44 and the connector 50
And a connection terminal portion 43a for connecting with.

A reinforcing plate 45 is fixed to the back surface of the surface of the insulating resin film 42 on which the conductor pattern 43 is formed so as to correspond to the connection terminal portion 43a.

The flexible board 41 is electrically connected to the connector 50 by inserting the flexible board 41 into the connector 50 from the connector insertion direction (arrow A direction) by gripping the vicinity of the connection terminal portion 43a with a finger or the like. Used in the connected state. At the time of this insertion work, since the insulating resin film 42 is reinforced by the reinforcing plate 45 and the rigidity of the flexible substrate 41 is increased, the insertion work into the connector 50 is smoothly performed.

[0005]

However, in the above-mentioned conventional flexible substrate 41, the connector 5 is used.
As shown in FIG. 11, when the insulating resin film 42 is inserted into the edge portion 4 of the reinforcing plate 45, the insulating resin film 42 is inserted into the edge portion 4 of the reinforcing plate 45.
5a is used as a fulcrum, and at this time, the insulating resin film 4
2, the conductor pattern 43 is stretched,
As shown in FIG. 2, a crack C may occur in the conductor pattern 43.

When static electricity charged by a worker or the like is discharged to the flexible substrate 41 with the crack C thus generated, the crack C portion of the conductor pattern 43 is burned and the conductor pattern 43 is broken. It will be.

The present invention has been made in view of the above-mentioned circumstances of the prior art, and an object thereof is to provide a highly reliable flexible substrate capable of preventing the occurrence of cracks in a conductor pattern. .

[0008]

In order to achieve the above object, the flexible substrate of the present invention comprises an insulating resin film on which a conductor pattern having a connection terminal portion for connection to a connector is formed, and the insulating resin. A reinforcing plate fixed so as to correspond to the connection terminal portion is provided on the back surface of the conductive pattern forming surface of the film, and is flexible between the insulating resin film and the reinforcing plate than the reinforcing plate. The most main feature is that a backing material is provided, and the backing material projects from the edge portion of the reinforcing plate in the direction opposite to the connector insertion direction.

The flexible substrate of the present invention is characterized in that the backing material is composed of an insulating layer formed by printing on the insulating resin film.

Further, the flexible substrate of the present invention is characterized in that the insulating layer has a multi-layer structure.

Further, the flexible substrate of the present invention is characterized in that the insulating layer has a multi-layer structure.

Further, in the flexible substrate of the present invention, a contact portion that constitutes a sheet-like switch is formed on at least one surface of the insulating resin film, and the back surface of the insulating resin film on which the conductor pattern is formed is A wiring pattern connected to the contact portion is provided, and an overcoat layer that covers the wiring pattern is formed by printing using the same material as the insulating layer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the flexible substrate of the present invention will be described below with reference to the drawings. 1 to 4 illustrate an embodiment of the present invention. FIG. 1 is a plan view of a flexible substrate according to an embodiment of the present invention, FIG. 2 is a bottom view of the flexible substrate, and FIG. FIG. 4 is a side sectional view of the substrate, and FIG. 4 is a side sectional view of the flexible substrate in a curved state.

As shown in FIGS. 1 to 3, in the flexible substrate 1 according to this embodiment, a conductor pattern 3 is formed on one surface of an insulating resin film 2, and a resist layer 4 is formed so as to cover the conductor pattern 3. The reinforcing plate 6 is provided on the rear surface of the surface of the insulating resin film 2 on which the conductor pattern 3 is formed, and is fixed through the insulating layer 5 as a backing material.

Next, the concrete constitution of each member constituting the flexible substrate 1 will be sequentially described.

The insulating resin film 2 is made of a polyethylene terephthalate (PET) film, and is formed in a strip shape so as to extend in the connector insertion direction (arrow A direction).

The conductor pattern 3 is formed by printing using a conductive paste-like ink prepared by mixing and stirring silver powder with a binder resin, and the end portion is the connector 10.
It is a connection terminal portion 3a for connecting with.

The resist layer 4 is formed by printing an insulating paste-like ink containing vinyl chloride, epoxy resin or the like on one side of the insulating resin film 2.
The conductor pattern 3 is covered with the terminal connecting portion 3a exposed.

The insulating layer 5 is formed by printing using an insulating paste-like ink containing vinyl chloride, epoxy resin or the like, and has a sufficiently higher flexibility than the reinforcing plate 6. have.

The reinforcing plate 6 is made of a polyethylene terephthalate film plate thicker than the insulating resin film 2, and is fixed to the insulating layer 5 by adhesion.
The resist layer 4 is projected from the end portion 6a in the direction opposite to the connector insertion direction (direction of arrow A) (note that the hatched band is attached to the insulating layer 4 in FIG. 2).

The flexible board 1 according to this embodiment is constructed as described above, and next, the insertion into the connector 10 will be described.

This flexible substrate 1 has a connection terminal portion 3
An operator grips the vicinity of a with fingers or the like and inserts the connector 10 into the connector 10 in the connector insertion direction (direction of arrow A), so that the connector 10 is used while being electrically connected to the connector 10. At the time of this inserting work, since the insulating resin film 2 is reinforced by the reinforcing plate 6 to increase the rigidity of the flexible substrate 1, the inserting work into the connector 10 is smoothly performed.

When the flexible board 1 is inserted into the connector 10 by prying or is attached in a bent state in a product in which the flexible board 1 is incorporated, as shown in FIG. Although the film 2 is curved with the edge portion 6a of the reinforcing plate 6 as a fulcrum, the insulating layer 5 interposed between the insulating resin film 2 and the reinforcing plate 6
Since the bending radius R of the insulating resin film 2 becomes larger than that of the conventional technique by the amount of, the bending stress acting on the conductor pattern 3 becomes small and the conductive pattern 3 is not stretched as compared with the conventional technique. It is possible to prevent the crack C from being generated in the conductor pattern 3.

In this embodiment, the backing material is composed of the insulating layer 5 formed by printing in order to simplify the manufacturing process, but the present invention is not limited to this. Alternatively, the backing material can be replaced with a sheet-like adhesive material such as an insulating double-sided adhesive sheet or an insulating rubber sheet.

If the thickness of the insertion portion of the flexible substrate 1 to be inserted into the connector 10 is limited, printing is repeated a plurality of times to form the insulating layer 5 as a multilayer structure having two or more layers to increase the thickness. By doing so, the bending radius R can be made larger, so that the conductor pattern 3
It is possible to more reliably prevent the crack C from being generated.

5 to 9 show a sheet-like switch to which the flexible substrate 1 is applied, and the same structural parts as those in the above-mentioned embodiment are designated by the same reference numerals.

FIG. 5 is a plan view of a sheet-like switch provided with a flexible substrate according to an embodiment of the present invention, FIG. 6 is a bottom view of the sheet-like switch, and FIG. 7 is a side sectional view of the sheet-like switch. 8 is a plan view showing the holding sheet and the click spring removed from FIG. 5, and FIG. 9 is a bottom view showing the overcoat layer, the insulating layer, and the reinforcing plate removed from FIG.

The sheet-shaped switch 21 has a rectangular wide end formed on the end opposite to the connection terminal 3a of the insulating resin film 2, and a resist layer 4 is formed to cover one side of the wide rectangular part. The insulating resin film 2 has a structure in which the switch elements 23 are arranged in the three circular holes 22, respectively.
A wiring pattern 24 is formed by printing on the back surface of the surface on which the conductor pattern 3 is formed.

The switch element 23 has a central contact portion 25 and an outer contact portion 26 formed by printing in the circular hole 22.
And a contact portion formed by and an outer peripheral portion of the pressure-sensitive adhesive sheet 2 superposed on the contact portion so as to contact the outer contact portion 26.
7 includes a click spring 28 made of a dome-shaped conductive metal thin plate capable of reversing operation, which is attached by 7. Each wiring pattern 24 and the central contact portion 25 are connected via a through hole (not shown). There is.

One of the outer contact portions 26 is connected to the wiring pattern 3 and the other two are connected to each other by the conductive pattern 29, and the outer contact portion 26 is also connected.
Each of the conductor patterns 3 other than that connected to the wiring pattern 24 is connected to the wiring pattern 24 via a through hole (not shown), and the wiring pattern 24 is formed by printing using the same material as the insulating layer 5 by the overcoat layer 30. The coating is protected (in FIG. 6, the insulating layer 5 and the overcoat layer 30 are shaded).

As described above, since the overcoat layer 30 is formed by printing using the same material as the insulating layer 5, the overcoat layer 30 can be formed in the same step as the insulating layer 5, so that the manufacturing process is simplified. Can be achieved.

In the sheet-shaped switch 21 having the above-described structure, when the operator presses the undulating portion of the adhesive sheet 27 corresponding to the dome shape of the click spring 28 through the pressing member (not shown), the click spring 28 is pressed. Causes a click feeling, the click spring 28 abuts the central contact portion 25, and the central contact portion 25 and the outer contact portion 26 are electrically connected to each other to be in a switch-on state.

Further, when the pressing operation force on the undulating portion of the adhesive sheet 27 is released in this state, the inverted click spring 28 automatically returns to its original shape due to its elasticity, so that the click spring 28 is turned on. Is separated from the central contact portion 25 and the conduction between both contact portions 25 and 26 is released to be in a switch-off state.

[0034]

The present invention is carried out in the form as described above, and has the following effects.

The flexible substrate of the present invention has an insulating resin film on which a conductor pattern having a connecting terminal portion for connecting to a connector is formed, and the connecting terminal portion on the back surface of the insulating resin film on which the conductive pattern is formed. A reinforcing plate fixed so as to correspond thereto, and a backing material more flexible than the reinforcing plate is interposed between the insulating resin film and the reinforcing plate, and the backing material is provided on the reinforcing plate. Since it is made to project from the edge portion in the direction opposite to the connector insertion direction, the bending radius of the insulating resin film can be increased by the amount of the backing material, and the bending stress acting on the conductor pattern can be minimized. It is possible to suppress the occurrence of cracks.

Further, since the backing material is composed of the insulating layer formed by printing on the insulating resin film, the backing material can be easily formed and the manufacturing process can be simplified.

Since the insulating layer has a multi-layer structure,
The bending radius of the insulating resin film can be increased, and cracks in the conductor pattern can be prevented more reliably.

Furthermore, a wiring pattern for connecting to a contact portion constituting a sheet-shaped switch is provided on the back surface of the insulating resin film on which the conductive pattern is formed, and an overcoat layer for covering the wiring pattern is provided on the insulating layer. Since the same material is used for printing, the overcoat layer and the insulating layer can be formed in the same step, so that the manufacturing process can be simplified.

[Brief description of drawings]

FIG. 1 is a plan view of a flexible substrate according to an exemplary embodiment of the present invention.

FIG. 2 is a bottom view of the flexible substrate.

FIG. 3 is a side sectional view of the flexible substrate.

FIG. 4 is a side sectional view of the flexible substrate in a curved state.

FIG. 5 is a plan view of a sheet-like switch including a flexible substrate according to an exemplary embodiment of the present invention.

FIG. 6 is a bottom view of the sheet-shaped switch.

FIG. 7 is a side sectional view of the sheet-shaped switch.

FIG. 8 is a plan view showing a holding sheet and a click spring removed from FIG.

FIG. 9 is a bottom view showing an overcoat layer, an insulating layer, and a reinforcing plate removed from FIG.

FIG. 10 is a cross-sectional view of a conventional flexible substrate.

FIG. 11 is a side sectional view of a conventional flexible substrate in a curved state.

12 is an enlarged cross-sectional view of a main part of FIG.

[Explanation of symbols]

1 Flexible substrate 2 Insulating resin film 3 conductor pattern 3a Connection terminal part 4 Resist layer 5 insulating layers 6 Reinforcement plate 6a end 10 connectors 21 sheet switch 22 circular hole 23 Switch element 24 wiring pattern 25 Central contact point 26 Outside contact part 27 Adhesive sheet 28 click springs 29 Conductive pattern 30 Overcoat layer R bending radius

Claims (4)

[Claims] 1. An insulating resin film on which a conductor pattern having a connection terminal portion for connecting to a connector is formed, and fixed on the back surface of the surface of the insulating resin film on which a conductor pattern is formed so as to correspond to the connection terminal portion. A reinforcing plate provided between the insulating resin film and the reinforcing plate, and a backing material that is more flexible than the reinforcing plate is interposed between the insulating resin film and the reinforcing plate. A flexible substrate characterized in that it projects in a direction opposite to the insertion direction. 2. The flexible substrate according to claim 1, wherein the backing material is composed of an insulating layer formed by printing on the insulating resin film. 3. The flexible substrate according to claim 2, wherein the insulating layer has a multi-layer structure. 4. A contact portion forming a sheet-like switch is formed on at least one surface of the insulating resin film, and a wiring pattern connected to the contact portion is formed on the back surface of the conductor pattern forming surface of the insulating resin film. The flexible substrate according to claim 2 or 3, characterized in that an overcoat layer that covers the wiring pattern is formed by printing using the same material as the insulating layer.