JPH066003A - Flexible circuit and manufacture thereof - Google Patents

Abstract

PURPOSE:To secure the insulating property between the adjacent pads, and to improve the peeling strength of a connection pad by a method wherein the tip part to be inserted into a connector is insulated. CONSTITUTION:When a plurality of conductors 20 are formed in parallel on an insulated substrate 1 by etching, the coupling conductor parts 8, with which all the adjacent conductors 20 will be connected to arbitrary positions, are etched in such a manner that the dimension a-component is masked so that the tip of the conductors 20 is not exposed as far as to the circuit end part. Then, after the electrode 7 for electroplating has been connected to one end of the coupling conductors 8, an over-coating 30 is provided in such a manner that the coupling positions of connection pads 50 and the coupling conductors 8 will be opened. In this state, after the prescribed plating has been conducted on the connection pads 50 by applying a current to the electrode 7 of the coupling conductors 8, the coupling conductor pads 8 only, with which the connection pads 5 are connected, is removed by etching. In this case, the plating formed on the connection pads 5 functions as an etching resist. Lastly, the electrode 7, which is used for plating, is cut from the edge face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible circuit and a method for manufacturing the same, and more particularly, to a flexible circuit which can secure insulation between adjacent pads and improve mechanical strength of the pads when mounted on a connector. The present invention relates to a circuit and a manufacturing method thereof.

[0002]

2. Description of the Related Art Generally, a connector for connecting a flexible printed circuit board and a flexible flat cable (collectively referred to as a flexible circuit) to a connector is disclosed in, for example, Japanese Patent Publication No. 60-13274. Proposals have been made in which a conductive reinforcing portion that protrudes at the end of the flexible circuit is provided and this reinforcing portion is attached to the connector for connecting to the printed circuit board, or one in which the end of the flexible circuit is simply exposed for connector connection. ing.

However, although such a connecting means is a simple and inexpensive method, as the pitch between the conductors of the plugging portion becomes narrower due to the higher density, the creeping distance between the adjacent conductor portions becomes smaller and the connecting means becomes flexible. Insulation deterioration between adjacent conductors in the circuit becomes a problem.

The disadvantages of this prior art are shown in FIGS.
Will be explained. First, in the flexible circuit, as shown in FIG. 5, a plurality of conductors 2 are formed in parallel on an insulating substrate 1 by etching, and an overcoat 3 is coated on the plurality of conductors 2 to insulate the conductors 2 from each other. Then, the overcoat 3 at the end of the flexible circuit is peeled off to form the plug portion 4 including the plurality of connection pads 5. Since the plug portion 4 has low mechanical strength and maintains an electrical connection with the connector, electrodes 7 for electroplating are connected to a plurality of connection pads 5 and plating such as tin, gold or solder is performed. The electrode 7 is cut at the position of the cut line 10 after the plating process. Therefore, the end surface of the flexible circuit according to the conventional technique (the tip of the plug portion) always exposes the end surface of the conductor. The flexible flat cable also has the same configuration of the plug portion, although the manufacturing method is different.

A state in which the flexible circuit thus configured is inserted into the connector will be described with reference to FIGS. 6 and 7. First, the connector 11 includes a terminal 13 inside which is elastically contacted with the connector 4 of the circuit, and the connector 1
1 is provided with a protrusion 11a for preventing adhesion of dust 12 accumulated therein, and the inserted flexible circuit has the end portion riding on the protrusion 11a and the plug portion 4
Are connected so as to come into contact with the terminals 13 of the connector 11.

[0006]

However, in the connection of the flexible circuit and the connector, as the pitch between the connection pads 5 of the circuit becomes narrower, dew condensation or metal wear due to insertion / extraction at the contact portion with the protrusion 11a occurs. There is a problem that the dust 12 is accumulated and the insulation between the adjacent connection pads 5 is significantly reduced, which may cause a short circuit. It is possible to use the shoulder of the connector without inserting the plug of the circuit to the bottom of the connector, but in the case of a flexible circuit, the strength of the material is insufficient and it can not be applied, and it is flexible. It is difficult to process a tape-shaped material such as a flat cable manufactured by cutting a tape-shaped material into an arbitrary shape.

Further, since the area of the connection pad is reduced due to the high density, the adhesive strength between the insulating base material and the conductor is reduced, and the pad peeling may easily occur due to the frictional force applied to the connection pad when the connector is inserted and removed. It was

An object of the present invention is to eliminate the above-mentioned problems caused by the prior art, and to provide a flexible circuit capable of ensuring insulation between adjacent pads and improving peel strength of connection pads, and a manufacturing method thereof. Is to provide.

[0009]

In order to achieve the above-mentioned object, the flexible circuit according to the present invention is characterized in that the tip portion inserted into the connector is insulated, except for the connection pad positions arranged in a staggered manner. The second characteristic is to insulate all the conductors.

Further, in the method for manufacturing a flexible circuit according to the present invention, a plurality of conductors are arranged in parallel on the insulating base material so that some of the conductors are electrically connected by the connecting conductor portion and the end portions of the plurality of conductors are not exposed at the end portion of the insulating substrate. After arranging, applying an overcoat to expose a part of the plurality of conductors and the connecting conductor portion, and supplying electric power for electroplating to the connecting conductor portion to form a connection pad by plating part of the plurality of conductors. A third feature is that the tip portion inserted into the connector is insulated by removing the connecting conductor portion.

[0011]

In the flexible circuit according to the first aspect of the present invention, by electrically insulating the tip portion inserted into the connector, the short circuit caused by the metal abrasion powder or the like accumulated between the plurality of conductors due to dew condensation or insertion / removal is prevented. In addition, the peel strength of the connection pad can be improved. The flexible circuit according to the second aspect of the present invention can prevent short-circuiting between the conductors as in the first aspect, and can reduce the conductor pitch to arrange the connection pads at a high density.

In the method for manufacturing a flexible circuit, which is the third feature, the plurality of conductors are arranged in parallel so that the ends thereof are not exposed at the end of the insulating substrate, and the conductors other than the connection pad portions are overcoated. Thus, short circuit can be prevented and the peel strength of the connection pad can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A flexible circuit and a method of manufacturing the same according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a diagram showing the structure of a plug portion of a flexible circuit manufactured by the manufacturing method according to this embodiment. This flexible circuit is formed on an insulating base material 1 as shown in FIG. 4 (a). When the plurality of conductors 20 are formed in parallel by etching, the connecting conductor portions 8 that connect all the conductors 20 adjacent to each other at arbitrary positions are also etched, and the tips of the plurality of conductors 20 are not exposed to the circuit end portion. Similarly, etching is performed with the mask for the dimension a. That is, the conductor in this state is etched into a substantially "king" shape in which the tips are not exposed and some are connected.

Next, the flexible circuit is shown in FIG.
After connecting the electrode 7 for electroplating to one end of the connecting conductor 8 as shown in (b), an overcoat 30 is applied so that the connecting position of the connecting pad 50 and the connecting conductor 8 is opened. In this state, the electrodes 7 of the connecting conductors 8 are energized to predetermined plating on the connection pads 50, and then only the connecting conductor portions 8 connecting the conductors 20 are removed by etching. In this case, the plating applied to the connection pad 5 acts as an etching resist, and finally the electrode 7 used for plating is cut from the end face.

In the flexible circuit thus manufactured, the connection pads 50 for contacting the contacts of the connector are arranged in a zigzag pattern at the ends thereof, and the conductors 20 are formed.
The end portion of the plug is formed as a plug 40 that is not exposed to the outside. The tip end side of the connection pad 50 of the conductor 2 stops at a position inside the end surface of the insulating base material 1 (dimension a) and at a tip end side of the connection pad 50 (dimension b; extra length dimension). It has a structure. By arranging the connection pads 50 in a zigzag pattern, the flexible circuit according to the present embodiment can reduce the creepage distance between the adjacent pads and can arrange the connection pads 50 at high density. Needless to say, the arrangement of the pad portions 5 is matched with the contact contact position on the connector side. Further, the dimension a from the tip and the extra length dimension b of the conductor are determined from the insertion depth of the connector. With the above configuration, the insulation between the conductors depends only on the distance between the pads on the plane, and the peel strength of the conductor can be improved against the external force applied to the pads.

FIG. 2 is a diagram showing a second embodiment of the flexible circuit according to the present invention. The flexible circuit according to the present embodiment is provided with the overcoat 31 and the end overcoat 3a so that the overcoat is opened in a rectangular shape when the conductor 21 is overcoated in the above-described manufacturing method. The flexible circuit according to the present embodiment can secure the insulation between the conductors and improve the peel strength of the conductor against an external force applied to the pad, as in the above embodiments. In this embodiment, the example in which the overcoat is opened in a rectangular shape is shown, but only the connection pad 51 may be exposed in parallel.

FIG. 3 is a perspective view showing a flexible circuit according to another embodiment. In the flexible circuit according to the present embodiment, when the conductor 22 is overcoated in the conventional manufacturing method, the flexible circuit is overcoated so that the entire end of the flexible circuit is exposed, and then the end is bent. By forming the bent portion 6, the insulation of the end portion is secured. In the flexible circuit according to the present embodiment, the insulation between the conductors can be ensured as in the above embodiments, and the strength can be further improved by bending.

As described above, in the flexible circuit according to the present embodiment, since the conductor is not exposed at the tip of the plugging portion, the uncertainty of the creepage distance generated when the connector is connected is eliminated, and the insulation between adjacent conductors is secured. It is possible and reliability is improved. Further, since the peeling strength of the connection pad is increased, the area of the connection pad can be reduced, and the pitch of the contact plugs can be narrowed as a whole.

[0020]

As described above, the flexible circuit according to the present invention is caused by metal abrasion powder or the like accumulated between the plurality of conductors due to dew condensation or insertion and removal by electrically insulating the tip end portion inserted into the connector. It is possible to prevent a short circuit and improve the peel strength of the connection pad. The method for manufacturing a flexible circuit according to the present invention is
Short-circuiting can be prevented and peeling strength of the connection pad can be improved by arranging the end portions of the plurality of conductors in parallel so as not to be exposed at the end portion of the insulating substrate and overcoating the conductors other than the connection pad portion. .

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of a flexible circuit according to the present invention.

FIG. 2 is a diagram showing a second embodiment of the flexible circuit according to the present invention.

FIG. 3 is a diagram showing a third embodiment of a flexible circuit according to the present invention.

FIG. 4 is a diagram for explaining a method of manufacturing a flexible circuit according to the present invention.

FIG. 5 is a diagram for explaining a method for manufacturing a flexible circuit according to a conventional technique.

FIG. 6 is a view showing a connector connection state of a flexible circuit according to a conventional technique.

FIG. 7 is a view showing a connector connection state of a flexible circuit according to a conventional technique.

[Explanation of symbols]

1: Insulating substrate, 2: Conductor, 3: Overcoat, 4: Plug part, 5: Connection pad, 6: Bent part, 7: Plating electrode, 8: Conductor connecting part, 9: Clear pad for etching, 10 : Cut line, 11: Connector, 11a: Mold protrusion, 12: Dust.

Claims (3)

[Claims] 1. A flexible circuit, which comprises a connection pad exposing a part of a plurality of conductors arranged in parallel, and which is electrically connected when the connection pad comes into contact with a terminal of the connector, insulates a tip portion inserted into the connector. A flexible circuit characterized by that. 2. In a flexible circuit, which is provided with connection pads exposing a part of a plurality of conductors arranged in parallel, and which conducts when the connection pads come into contact with the terminals of the connector, the connection pads arranged in a staggered pattern are excluded. A flexible circuit characterized by insulating all conductors. 3. A method for manufacturing a flexible circuit, comprising a connection pad exposing a part of a plurality of conductors arranged in parallel, wherein the plurality of conductors are partially conducted by a connecting conductor portion on an insulating base material. Are arranged in parallel so as not to expose the end portions of the insulating substrate to the end portions of the insulating substrate, and an overcoat is applied to expose a part of the plurality of conductors and the connecting conductor portion, and electric power for electroplating is supplied to the connecting conductor portion. A method for manufacturing a flexible circuit, characterized in that, after forming a connection pad by plating a part of the plurality of conductors, the connecting conductor portion is removed to insulate a tip portion inserted into a connector.