JP2005116300A - Flexible flat cable - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to give flexibility in width direction of a flexible flat cable ( herein after FFC). <P>SOLUTION: A cutting slit which penetrates an insulator is provided between conductors constituted by a printing technology on the pasting face of two insulators forming a FFC. The lateral width of the individual portions of the FFC divided by the slit becomes narrower and the insulator of each portions can be easily distorted and deformed, and the internal stress in the width direction of the insulator generated inside the insulator of the FFC by shifting of mutual position relations between the FFC end part and a connector is alleviated by the distortion deformation owing to installation of the slit, and as a result, flexibility in width direction of the FFC can be given. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention replaces a conventional insulated wire for connection within a printed circuit board, between printed circuit boards, and between a printed circuit board and another electronic circuit unit for the purpose of reducing the size of electronic equipment and reducing the cost of connecting an electric circuit. This is a technique relating to a flexible flat cable (hereinafter abbreviated as FFC) in which a conductor is disposed on a bonding surface of two flexible film-shaped resin material insulators by a printing technique.

Even when the positional relationship between a pair of connectors to which both ends of the FFC are to be connected is close and a connection between a pair of connectors can be made by a short FFC, an FFC longer than the distance between the connectors is applied, By utilizing the bending caused by the length margin of the FFC, improvement in connection workability and prevention of malfunctions caused by displacement of the positional relationship between the connectors are realized. However, the application of an FFC longer than the length necessary for connection between the connectors hinders downsizing of the equipment and economical configuration.

Japanese Patent Laid-Open No. 2002-18496 JP 2003-168509 A

The FFC is flexible and easily bent in a direction perpendicular to the surface. However, in order to prevent the peeling and disconnection accident of the conductors arranged by the printing technology on the two insulator bonding surfaces constituting the FFC, the polyester material has high rigidity and therefore low flexibility as an insulator material. A synthetic resin material is used and does not exhibit flexibility in a direction parallel to the FFC surface.

Normally, connectors for connecting the FFC conductor and the electric circuit on the printed circuit board are arranged at both terminal positions of the FFC, and a large number of conductive elements at both ends of the FFC arranged at high density by printing technology. Similarly, a large number of terminals arranged at high density in the body and the connector realize an electrical connection function by applying appropriate pressure to each conductor surface while maintaining a pair relationship with each other. However, if there is even a slight shift in the lateral positional relationship between the connectors arranged at both terminal positions of the FFC, the FFC will not bend in the horizontal direction and cannot absorb the positional shift. A large stress is applied to.

Due to the stress described above, it becomes difficult to insert the FFC terminal into the connector, or even after insertion, the printed circuit board support mechanism where the connector is assembled is displaced due to impact or changes in device temperature during use. As a result of the deterioration, an electrical short circuit or a contact failure accident is caused between the conductor of the FFC terminal portion and the terminal portion of the connector, which strictly require a mutual dimensional accuracy relationship.

In order to address the above-described problems, the present invention provides a means for imparting flexibility in the width direction B of the FFC surface shown in FIG. A notch 4 having a length that does not reach the reinforcing plates 3 of the FFC end portions 5 is provided at a position between the FFC conductors 2. The notches 4 are cut between the conductors 2, in the case of drilling every several conductors 2, or farther from the both end portions 5 in the width direction B of the FFC and toward the center. It is also possible to increase the arrangement density of 4.

In addition to being able to process the cut 4 with a cutter having a thin cutting edge, the conductor 2 adjacent to the cut 4 as shown in FIGS. 3 (b), 3 (c) and 3 (e). It is also possible to form a perforated shape having a certain width in a range not in contact with.

As described above, according to the present invention, the following effects can be obtained by providing the notches 4 between the plurality of conductors 2 disposed on the bonding surface of the two insulators 1 constituting the FFC. It is done. When stress occurs in the FFC due to the positional relationship between the FFC and the connector, each FFC divided by the cuts 4 is formed by drilling n cuts parallel to the conductors 2 on the surface of the insulator 1. Since the lateral width of the FFC insulator 1 becomes narrow, the torsional deformation becomes easy, and the positional deviation between the FFC and the connector can be absorbed by the torsional deformation of the FFC insulator 1.

Flexibility in the width direction B of the FFC can be effectively imparted by arranging the cuts 4 between all the conductors 2, but the length of the FFC is sufficiently larger than the width. In the case of a long length, the notch 4 is not necessarily required between all the conductors 2, and it is possible to arrange the notch 4 for each of the plurality of conductors 2 in consideration of the ratio of the length and width of the FFC. Moreover, since the latent stress is released on both sides in the width direction B of the FFC, the central portion in the width direction B of the insulator 1 has a larger potential stress, so the arrangement density of the cuts 4 is increased, It is also possible to facilitate the relaxation of the latent stress due to the torsional deformation of the insulator 1.

The incision 4 can be processed by a cutter having a thin cutting edge as shown in FIG. 3 (a) or a method of perforating in a strip shape as shown in FIG. 3 (b). ) At both ends of the incision 4 and at the corners at the four corners of the strip-shaped perforations in FIG. 3 (b) due to the concentration of latent stress in the insulator 1 A crack-like damage may occur, causing a disconnection accident of the conductor 2. The shapes shown in FIGS. 3 (c) to 3 (e) are applied to both ends of the notch 4, and the occurrence of the above-described problems can be prevented by distributing the stress in the portions.

An embodiment of imparting flexibility in the width direction B of the FFC according to the present invention will be described below with reference to FIGS. The FFC insulator 1 shown in FIGS. 1 and 2 is soft and flexible in the direction A perpendicular to the surface, but does not show flexibility in the width direction B of the FFC, and both end portions of the FFC. When the positional relationship between the FFC and the connector is shifted in the width direction B of the FFC when the 5 is fitted to the connector, the positional shift cannot be absorbed by the flexibility of the FFC.

For this reason, in the example shown in FIG. 1 and FIG. 2, by disposing the notch 4 between the plurality of conductors 2 disposed by the printing technique on the bonding surface of the two insulators 1 constituting the FFC, The entire width of the FFC is divided into three. Since each divided part is narrow in width, it can be easily torsionally deformed and can absorb the positional displacement between the connector and the FFC in the width direction B, and the connection workability between the connector and the FFC can be improved. It is possible to cope with the improvement and the change in the dimensional accuracy of the mutual positional relationship due to the vibration shock and thermal change during use.

Flexibility in the width direction B of the FFC can be effectively imparted by arranging the cuts 4 between all the conductors 2, but the length of the FFC is sufficiently larger than the width. In the case of a long length, the notch 4 is not necessarily required between all the conductors 2, and it is possible to arrange the notch 4 for each of the plurality of conductors 2 in consideration of the ratio of the length and width of the FFC. Moreover, since the latent stress is released on both sides in the width direction B of the FFC, the central portion in the width direction B of the insulator 1 has a larger potential stress, so the arrangement density of the cuts 4 is increased, It is also possible to facilitate the relaxation of the latent stress due to the torsional deformation of the insulator 1.

The incision 4 can be processed by a cutter having a thin cutting edge as shown in FIG. 3 (a) or a method of perforating in a strip shape as shown in FIG. 3 (b). The stress concentration points 6 at both ends of the notch) and the stress concentration points 6 at the four corners of the strip-shaped perforations in FIG. In some cases, crack-like damages starting from the above-mentioned part may occur, causing a disconnection accident of the conductor 2.

For this reason, as shown in FIG. 3C, both corners of the notch 4 are rounded at the corners of both ends of the notch 4, or as shown in FIG. 3D and FIG. 3E. Both ends of the cut 4 have a circular shape with a diameter larger than the width of the cut 4, the concentrated stress generated at both ends of the cut 4 is dispersed and relaxed, and the stress concentration point 6 is the starting point to prevent the occurrence of crack-like damage. Is possible.

As an application example of the present invention, for the purpose of reducing the size of electronic equipment and reducing the cost of connecting electric circuits, between printed circuit boards, between printed circuit boards, and between connectors arranged between printed circuit boards and other electronic circuit units. It can be applied to other connection applications.

It is a perspective view of the flexible flat cable by this invention. It is an exploded view of the flexible flat cable by this invention. It is detail drawing of the example of a cut shape.

Explanation of symbols

1: Insulator 2: Conductor 3: Reinforcing plate 4: Notch 5: End portion 6: Stress concentration point

Claims (6)

A flexible flat cable comprising a plurality of conductors cut in parallel with a conductor. 2. The flexible flat cable according to claim 1, wherein a notch penetrating the insulator is provided between all conductors. The flexible flat cable according to claim 1, wherein a notch is provided for each of a plurality of conductors. The flexible flat cable according to claim 1, wherein the penetration density of the cut is increased from both ends in the width direction of the cable toward the center. 5. The flexible flat cable according to claim 1, wherein the notch itself has a width. 6. The flexible flat cable according to claim 5, wherein corners of both ends of the cut are rounded, or both ends of the cut are circular with a diameter larger than the width of the cut. cable.