Flexible flat cable

Tuesday, 16 January 2007

Flat flexible cables (FFC), or ribbon cables and other flat cabling technologies are well known in the electronics industry as a means of electrical systems interconnection. Flexible flat cables have gained widespread acceptance and are gaining prevalence over conventional round wire systems because of their compact design, low cost, and ability to bend. Flexible flat cable is commonly used in electrical and electronic equipment such as business machines, industrial controls, telecommunication systems, and computers. Flat cables have advantages including the elimination of the need to provide bundle wires and easy wiring due to high flexibility. Flat cables are of structure in which plural conductive wires arranged on the same plane are put between two insulating tapes. Since such flat cables are flat and have bending ability, there are merits that it is easy to carry out wiring work and/or wiring can be made also at narrow portion, etc. By virtue of these advantageous, flat cables are utilized in internal wiring of electronic equipment such as personal computers and communication equipment. Flexible flat cables, for example, are used for electrical connection to components in many consumer electronic applications, such as digital and analog tape heads, inkjet and dot matrix printer heads, mobile phones, the connection between the body of a laptop computer and its lid, and other consumer electronics requiring small and lightweight flexible cables. Flat cables are mainly used in integrated circuit boards to connect different circuits. In the electronic packaging industry, there are provided operatively joined wherein pluralities of rigid printed circuit board (PCB) sections which are essentially interconnected through the intermediary of flexible printed circuit board sections. Flat flexible cables are used to connect printed circuit boards arranged in a confined space inside an electronic device, such as a computer, for reducing the overall size of the electronic device. Flexible flat cables enable the rigid printed circuit boards to be folded and unfolded relative to each other through predetermined angular displacements in order to form a three-dimensional printed circuit board structure. An FFC may be directly connected to a circuit board by soldering. Alternatively, an FFC connector may be used to connect an FFC to a circuit board.

Flat flexible cable (FFC) is typically made of a plastic substrate having a plurality of electrical conductors or the like mounted or attached to the plastic substrate. Flexible flat cables have a plurality of electrical conductors that are molded inside a flexible, electrically insulative material or conduit. The conductors, which may be round or flat in cross-section, typically have very small dimensions and are spaced apart in a parallel configuration on narrow center-to-center spacings. The conductors can vary in width and thickness depending on the current carrying capacity requirements. The number of conductors can vary from 3 to 4 up to 60 or more. Commonly, the distance between the axial centers of adjacent conductors, or the pitch of the cable, is equal to 0.050 inches. The plastic substrate and conductor assembly is flat and flexible. Many types of plastic have been used to form the plastic substrate such as polyester, polyvinyl, polyimide, polyetherimide, polyethylene naphthalate, or polycarbonate insulating films. These films are lightweight, flexible, and thin. At the connection termination of the flat cable, the two insulating covering layers are removed to expose the terminations of the conductors. The exposed terminations of the conductors are connected, for example, to the core conductors of other cables etc. Flat cables for electrically connecting circuit boards are formed by arranging a plurality of wires in parallel with each other in a flexible base member of an electrically insulating material and adapted to be effectively used for wiring and electrically connecting circuit boards with or without movable parts interposed between them. In general, two types of flat flexible cables must be distinguished, the laminated and the extruded ones. Laminated flat flexible cables consist of electrical conductor traces, generally of copper, which are adhered in parallel between two films and are thus insulated against the outside and from one another. Under certain circumstances, the films can be of multiple construction or more than two films can be used. Extruded flat flexible cables consist of conductor traces that are fed through special extruding machines, wherein an electrically insulating extrudate is molded or injected around them, so that the individual conductor traces are insulated against the outside and from one another by the extrudate. As a flat cable used for connecting computers and communication devices which require resistance to noise, a shielded flat cable comprising an electromagnetic wave shielding layer for preventing malfunctioning caused by the EMI disturbance is widely used. A flexible flat cable usually is covered with a conductive meshed layer made of silver for reduction of EMI disturbances by being in electric contact with the metallic upper plate or base plate.

Flat flexible cables are typically terminated using connectors to form cable assemblies suitable for interconnecting printed circuit boards, circuit modules and other electrical and electronic devices. A flat flexible cable connector generally includes a dielectric housing having a plurality of terminals arranged at regular intervals across a mouth of the housing. The terminals have contact portions for electrically engaging conductors on the flat flexible cable inserted into the mouth. An actuator is slidably mounted on the housing for biasing the flat flexible cable against the contact portions of the terminals. An electrical connector assembly for flexible flat cable used to electrically connect a flexible printed wiring board is called an FFC or FPC connector. It typically comprises a housing having an opening and contacts engaged in the opening and a rotary portion designed to freely open and close the opening of the housing by its rotational motion and hold the flexible flat cable in a sandwich relation when it is in its dosed position. Often a connector, mounted to one or both ends of the FFC, has typically been used with a set of electrical receptacles or sockets which are designed to receive terminal posts or contact pads on the printed circuit board. There are many relatively small insertion sockets provided on the circuit boards for flat cables to insert thereinto. To enable effective contact with bare ends of the flat cable, the insertion socket is normally designed in two ways, namely, a bottom-contacting type and a top contacting type. Use of low insertion force (LIF) and zero insertion force (ZIF) connectors on printed circuit boards for receiving a flexible printed circuit (FPC) or a flexible flat cable (FFC) is well known in the field. Such connectors are typically soldered or otherwise affixed to an internal circuit board of an electrical device. An FFC is inserted into the connector and held in place to ensure positive electrical contact between the conductors of the FFC and the terminals of the connector.

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