Flexible flat cable and connector for connecting the same

Abstract: The flexible flat cable has an insulating base film, at least two sets of conductor groups and an insulating cover layer for covering the conductor groups. An end of the cable has, on one surface thereof, conductor contact areas formed by directly and partially exposing conductors of the conductor groups or partially exposing conductor area electrically connected to the conductors. The conductor contact areas are aligned along the width of the cable for each conductor group. The connector for connecting the cable has a connector body and a retainer plate and pinches the cable between the connector body and the retainer plate and contacts the conductor contact areas of the cable to the corresponding contacts on the opposite sides of the connector body to make electrical connection therebetween.

Description: The present invention relates to a flexible flat cable (for example, flexible printed circuit board (FPC)) and a connector for connecting the same. Cable and connector of this type adopt a construction of inserting an exposed portion of leads (or electrodes) at an end of the cable into a housing groove formed in the connector to make contact with contacts accommodated therein. In this case, as the number of leads of the cable increases, the arrangement of the contacts of the receiving connector becomes narrower and a higher manufacturing accuracy is required and it becomes harder to attain a necessary strength. Further, a contact area between the lead of the cable and the contact reduces and failure of the contact is apt to occur. Proposals have been made for flat cable connector assemblies in which connector contacts make contact with cable conductors, with the flat cable flexed to have the conductors on the outside of the cable flex, and with the contacts pushed over the conductors. For example:- US-A-4902236 discloses a flexible circuit and cable assembly for interconnecting printed circuit boards, including a flexible insulating substrate having a conductive ground plane on one side and first and second sets of longitudinally extending and interdigitated conductive traces on the other side. Connection pads are provided on the conductive traces, and a connector is provided having first and second sets of contacts. The flexible circuit is folded and held between tails of the first and second sets of contacts. There is no additional mechanical provision for retaining the connector on the flexible circuit, and this creates a problem for mechanical integrity of the assembly. US-A-3923364 discloses a shielded, flat, flexible conductor cable, and an assembly for mechanically establishing electrical connections between the cable and circuit boards. A connector is disclosed in which conductors on the flat cable are connected electrically to contacts in the connector, the flat cable being flexed over an anvil member so that the cable conductors are exposed on the outward convex surface of the flexed cable, the connector contacts being pushed over the flexed cable to make contact with the cable conductors. In this arrangement, the connector contacts are thus pushed over the flexed cable. According to the invention, there is provided an electrical cable assembly comprising: a flat flexible cable including; an insulating base film; at least two sets of conductor groups each having a plurality of parallel arranged conductors provided in one or both surfaces of said base film; and an insulating cover layer for covering said conductor groups; wherein a location adjacent an end of said cable has on one surface thereof spaced apart conductor contact areas formed by directly exposing the conductors of said conductor groups or partially exposing conductor areas electrically connected to said conductors, and the conductor contact areas are aligned along the width of the cable for each conductor group; and in case of conductor groups being provided an opposite sides on said base film contact areas are formed for one conductor group by partially exposing the conductor areas electrically connected to said connector group via holes; an elongate cable connector body; and a retainer plate for supporting said cable and providing insertable positioning of said cable over said connector body; wherein said cable connector body is provided with a plurality of contacts on opposite longitudinal sides of said connector body, said flexible flat cable being pinched between each of said longitudinal sides of said cable connector body and said retainer plate by a spring force applied by said retainer plate and, contacting said spaced apart conductor contact areas of said cable to the corresponding contacts on said opposite longitudinal sides of said connector body to make electrical connection therebetween. BRIEF DESCRIPTION OF THE DRAWING FIGURES Figure 1 shows a perspective view showing a status before connection in one embodiment of a cable and a connector of the present invention. Figure 2 shows a perspective view showing a status of completion of connection of the connector and the cable of figure 1. Figure 3 shows a sectional view of the cable and the connector in the completion status of connection. Figure 4 shows a plan view of detail of the cable of figure 1. Figure 5 shows a longitudinal sectional view of the cable of figure 4. Figure 6 shows a developed view of another embodiment of a cable. Figure 7 shows a plan view showing a status before folding back a shield area in still another embodiment of a cable. Figure 8 shows a plan view showing a folded back status of the shield area in the cable of figure 7. Figure 9 shows a longitudinal sectional view of the cable of figure 8. Figure 10 shows a sectional view showing a connection status of still another embodiment of the cable assembly of the present invention with a connector. Figure 11 shows a perspective view showing a status before connection of still another embodiment of the cable assembly of the present invention. Figure 12 shows a plan view of a retainer plate in the embodiment of figure 11. Figure 13 shows a sectional view showing a connection status of a contact piece of the retainer plate and a contact in the embodiment of figure 11. Figure 14 shows a sectional view showing a status in which a retainer plate of a cable assembly of still another embodiment of the present invention is mounted to a connector body, and Figure 15 shows a sectional view showing a status of detaching the retainer plate in the embodiment of figure 14. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Figures 1-3 show one embodiment of a cable connector assembly comprising a flexible flat cable and a connector for connecting the same in accordance with the present invention. Figure 1 shows a status before the connection of the cable and the connector. Figure 2 shows a status of completion of connection and figure 3 shows a sectional view of the connector in that status. The cable in figure 1 is shown with an end thereof curved to allow the observation of a pattern plane of the cable. The cable in the illustrated embodiment comprises an FPC having conductor groups 20 and 30 each comprising a plurality of parallel conductors arranged on a surface of an insulating base film 10 and having insulating cover layers 40 and 50 formed on the conductor groups to cover them. Conductor contact areas 21 and 31 formed by directly and partially exposing the conductors of the conductor groups or partially exposing the conductor areas electrically connected to the conductors are provided at one end 60 of the cable to align in along the width of the cable. In the embodiment shown in figures 1-3, two sets of conductor groups are provided although the conductor group may be provided on only one surface thereof. In the illustrated embodiment, a number of electrodes are provided at the other end of the cable to allow the connection with an electronic element (for example, a display). Detail of the cable will be discussed below in conjunction with other embodiments. In figures 1-3, the connector for connecting the flexible flat cable comprises a connector body 100 and a retainer plate 110. The connector body is provided with a plurality of contacts 130 and 140 on both sides along the longitudinal direction. The flexible flat cable is pinched between the connector body and the retainer plate. The contacts provided on both sides of the connector body contact to the exposed conductor contacts 21 and 31 of the cable to make electrical connection. Each contact of the connector has a contact 131 or 141 extending from the connector body to pinch the exposed conductor contact 21 or 31 of the cable between the retainer plate and the contact area to secure the electrical connection of the contact area and the conductor contact area of the cable. In the illustrated embodiment, the contact areas are located at opposing and parallel corners (upper edge of a side) of the connector body. The retainer plate has a generally U-shaped lateral section and pinches the cable with the connector. Specifically, it has a pair of opposing plate pieces 111 and 112 (which act as leaf springs) to hold the exposed conductor contact areas of the cable in contact with the contact areas. The connector body and the retainer plate have engagement means 150 for engaging with each other with the cable being pinched therebetween. Specifically, the engagement means comprises a projection 151 provided at each of both shorter sides of the connector body and an engagement hole 152 formed at a position of the retainer plate corresponding to the projection. A guide post 101 is provided on a top plane of the connector body and when the connector and the cable are connected, guide holes formed in the retainer plate and the cable respectively are extended through by the guide post. Figures 4 and S show details of the cable of figures 1-3. As shown, the two sets of conductor groups 20 and 30 are provided on the both surfaces of the base film 10 and the respective conductor groups are covered by the cover layers 40 and 50. On one surface at the end 60 of the cable, the conductors of one of the conductor groups provided on that surface are directly and partially exposed to form the conductor contact areas 31. For the other conductor group, the conductor areas electrically connected to the conductor group through via holes 22 are exposed to form the conductor contact areas 21. As seen from figure 5, a gap is formed in the cable to prevent the conductor areas connected to one conductor group through the via holes (exposed areas of which forms the conductor contact areas 21) from being contacted to the other conductor group (a portion of which is exposed to form the conductor contact areas 31). Figure 6 shows another embodiment of the cable of the present invention (shown in a developed form). In the present cable, two sets of conductor groups 20 and 30 are arranged to oppose to each other with a predetermined spacing 70 therebetween on one surface of the insulating base film. The conductor groups are covered by the insulating cover layer 40. Each of the conductor groups comprises a plurality of parallel conductors. An end 60' of the cable is bent at a position close to a spacing between the two sets of conductor groups. The end has areas 21 and 31 on the opposite side of the spacing in which the conductors of the conductor groups are partially exposed and the exposed areas are aligned along the width of the cable. Figures 7-9 show other embodiment of the cable of the present invention. The present embodiment relates to a cable having shield means. The construction of the cable is basically identical to the cable of figures 4 and 5 except that at least one of the shield area 80 and 90 which integrally extend along the width of the cable is provided. (In the illustrated embodiment, the shield areas are provided on the front and rear surfaces of the cable). The shield areas are foldable so that they may be laid on the cable and the shield areas are provided with conductor planes 81 and 91 connected with one of the conductors of the conductor groups of the cable. (In the illustrated embodiment, they are connected to portions of the conductor groups provided on the front and rear surfaces of the cable). Figure 7 shows a status before the fold-back of shield areas and figure 8 shows a status after the fold-back of the shield areas onto the cable body. Figure 9 shows a sectional view thereof. In the illustrated embodiment, a pair of shield areas are provided and they may be folded on both the front and rear surfaces of the cable although only one shield area may be used with the shield area being capable of folding back to one of the surfaces of the cable. Figure 10 shows an embodiment in which the retainer plate (made of a conductive material) and the shield area of the cable are electrically connected and grounded. Conductor contact areas (21, 31) are provided on one surface of the flexible flat cable as they are in the above embodiments, and grounding conductor areas (23, 33) are provided on the opposite surface by directly and partially exposing the conductor planes of the shield areas or partially exposing the conductor areas electrically connected to the conductor planes. when the cable is pinched between the retainer plate and the connector body by the retainer plate, the retainer plate and the grounding conductor contact areas contact to make electrical connection. Figures 11-13 show other embodiment of the present invention. In the present embodiment, contact pieces 113 provided at the opposite ends (four corners) of the retainer plate directly press and contact grounding/fixing contact (two contacts for each of the four corners of the connector body or total of eight in the illustrated embodiment) mounted at the both ends of the connector body without intervening the flexible flat cable (see figure 13). As a result, the grounding of the retainer plate is secured through the grounding/fixing contact. Further, when the connector body is mounted on the printed circuit board, the contact piece of the retainer plate directly presses the contact so that the connector body is fixed without floating from the printed circuit board. (Namely, the soldering of the contact to the printed circuit board is secured.) In the illustrated embodiment, the contact piece is formed separately from the retainer plate body by a split groove 114 formed along the minor direction of the retainer plate. As a result, the grounding/fixing contact may be pressed by a portion of the retainer plate without providing a fixing pad separately from the retainer plate. In the present embodiment, the retainer plate is provided with window holes 116 at an appropriate interval along the longitudinal direction as shown in figure 12. In respective embodiments of the present invention including the present embodiment, the numbers of electrodes (leads and contacts) of the cable and the connector are appropriately shown and the numbers may not necessarily match. The retainer plate of the present embodiment is provided with engagement pieces 115 extending longitudinally at both ends thereof. On the other hand, the connector body is provided with recesses 102 for engaging with the engagement pieces of the retainer plate. Figures 14 and 15 shows another embodiment of the contact pieces and engagement pieces of the retainer plate. The engagement piece of the retainer plate is shaped such that it extends with downward inclination and has a side of the contact piece cut away so that the outer area of the split groove is wider than the inner area (which is closer to the center axis of the retainer plate). By extending the engagement piece of the retainer plate with the downward inclination, a support point when the retainer plate is to be removed from the connector body is farther than that when the plane of the engagement piece of the retainer plate is planar as shown in figure 15. Accordingly, an open angle of the retainer plate to the connector body is small and the removal of the retainer plate from the connector body is eased accordingly. By making the split groove of the contact piece wider in the outer area than in the inner area, even if the retainer plate is inclined with respect to the connector body as shown in figure 15 when the retainer plate is removed from the connector body, the retainer plate may escape the cable because the contact piece of the retainer plate is cut so that the damage of the cable by the contact piece is prevented. The flexible flat cable forming part of the cable assembly of the present invention is provided with the two sets of conductor groups on one or both surfaces of the base film to improve the integrity of the conductors. Further, since the partially exposed areas of the conductors (which serve as the leads or electrodes) are aligned for each conductor group, the access to the respective conductor groups is facilitated. In the embodiment having the shield area integrally extended along the width of the cable, the cable may be shielded by connecting the conductor plane of the shield area to the grounding conductor of the cable. The connector forming part of the cable assembly of the present invention is provided with a plurality of contacts on each of the opposite sides along the longitudinal side of the connector body and pinches the flexible flat cable by the connector body and the retainer plate to electrically connect the contacts of the connector and the exposed areas of the conductors. Accordingly, even if the number of leads (electrodes) of the cable increases, the arrangement pitch of the contacts of the corresponding connector need not be unduly reduced and sufficient mechanical strength is maintained. Further, sufficient contact area of the leads of the cable and contacts is secured and the cable and the contacts can be connected without failure of contact. It will of course be understood that the present invention has been described above purely by way of example, and that modifications of detail can be made within the scope of the invention.

Claims: An electrical cable assembly comprising: a flat flexible cable including; an insulating base film (10); at least two sets of conductor groups (20, 30) each having a plurality of parallel arranged conductors provided in one or both surfaces of said base film (10); and an insulating cover layer (40, 50) for covering said conductor groups (20,30); wherein a location adjacent an end (60, 60') of said cable has on one surface thereof spaced apart conductor contact areas (21, 31) formed by directly exposing the conductors of said conductor groups (20,30) or partially exposing conductor areas electrically connected to said conductors, and the conductor contact areas (21,31) are aligned along the width of the cable for each conductor group (20,30); and in case of conductor groups (20,30) being provided on opposite sides of said base film (10) contact areas are formed for one conductor group (20) by partially exposing the conductor areas (21) electrically connected to said connector group (20) via holes (22); an elongate cable connector body (100); and a retainer plate (110) for supporting said cable and providing insertable positioning of said cable over said connector body (100); wherein said cable connector body (100) is provided with a plurality of contacts (130, 140) on opposite longitudinal sides of said connector body, said flexible flat cable being pinched between each of said longitudinal sides of said cable connector body (100) and said retainer plate (110) by a spring force applied by said retainer plate (110) and, contacting said spaced apart conductor contact areas (21, 31) of said cable to the corresponding contacts on said opposite longitudinal sides of said connector body (100) to make electrical connection therebetween. A cable assembly according to claim 1 wherein each of said plurality of contacts (130,140) has a contact area (131, 141) extending from the cable connector body (100) at a position corresponding to said conductor contact area (21,31). A cable assembly according to claim 2 wherein said cable connector body and said retainer plate (110) have engagement means (150) for engaging with each other with said flexible flat cable being pinched therebetween. A connector according to claim 3 wherein said engagement means (150) comprises a projection (151) provided at each of the opposite side along a minor direction of said connector body and an engagement hole (152) of the retainer plate for engaging with said projection.

Inventors: KOISO MASAKAZU, OSHITANI AKIYOSI, SONOBE TOSHIMITU, KOISO, MASAKAZU, OSHITANI, AKIYOSI, SONOBE, TOSHIMITU
Applicants: THOMAS & BETTS CORP, THOMAS & BETTS CORPORATION
Application year: 1996
Main classification: H01R12
IPC codes: H01B7, H01R12