A flexible circuit board is comprised of a flexible board, wirings provided on the flexible board and connection pads to be conductive through wirings, which are provided on the edge of the flexible board. The printed wiring boards used for flexible printed circuits are fabricated by laminating a copper foil to a resin substrate and joining the layers with adhesive or with the application of heat and pressure into an integral board. The circuits may have one or more conductive layers as well as circuitry on one of the major surfaces or on both major surfaces. The circuits often include additional functional layers, e.g., insulative layers, adhesive layers, encapsulating layers, stiffening layers and the like. The plastic substrate of  a flexible optical circuit typically formed of a polyimide or similar types of engineering thermoplastic materials, such as polyetherimide or polybutylene terphthalate. The substrate is coated with an adhesive, such as a silicone adhesive, and a plurality of optical fibers are placed upon the adhesive-coated substrate. A flexible optical circuit can include another layer of the plastic material that forms a substrate in order to effectively sandwich the optical fibers between the layers of plastic. A flexible printed circuit typically includes a strip or cable with a plurality of embedded electrically conductive lines. The conductive lines are covered by an overlying layer of insulative material to form an elongated and relatively flexible circuit structure. Apertures may be formed in one of the insulation layers to expose portions of the conductive lines for electrical connection to other electronic components. Electronic devices, such as an IC, a photo sensor and so on, are placed at suitable positions on the flexible circuit board and are connected to each other. In general, the front and rear surfaces of the flexible circuit board are covered with insulating layers for preventing a wiring pattern from being conducted to other wiring pattern formed on other circuit board.

The use of flexible printed circuits has become quite widespread because of their low cost, ease of assembly in interconnection systems, and the low volumes that they occupy. Flexible circuits are most commonly used in board-to-board, board-to-chip, and chip-to-chip connections in packages having limited space and stacked rigid boards, thus requiring three-dimensional connections. Flexible circuits are largely used in portable electronic products, such as notebook (NB), mobile phone, personal digital assistant (PDA) and information appliance (IA). For example, the flexible printed circuit board can be used as a connection between a liquid crystal display (LCD), a floppy disk driver (FDD), a hard disk driver (HDD) or a compact disc read only memory driver (CD-ROM) to a motherboard. A hard disk drive (HDD) comprises magnetic disks housed in a casing, a spindle motor for supporting and rotating the magnetic disks, a head actuator supporting magnetic heads, a voice coil motor for driving the head actuator, a substrate unit, etc. Each magnetic head is connected to one end of a relay flexible printed circuit board (hereinafter referred to as relay FPC) on each arm, and the other end portion of the relay FPC is connected to the main FPC. Flexible circuits that incorporate optical and electrical components have become increasingly necessary, as the field of optoelectronics has spread into more and more applications. Generally, flexible circuits incorporating optical components are assembled with prefabricated optical fibers. Flexible optical circuits are utilized in a wide variety of applications in which fiber management is desirable. For example, flexible optical circuits are commonly utilized as optical backplanes to interconnect a number of printed circuit boards or the like. Flexible optical circuits can serve as ribbons of optical fibers in order to route the optical fibers in an organized fashion. Flexible circuit boards have been used to form an extended bus for supporting multiplexed communications among remotely located electronic modules.

The flexible printed circuit board can be divided into four sorts according to functions: lead line, printed circuit, connector, and integration function system. Due to the thin nature of high performance flexible circuits, it is often necessary to adhesively bond such circuits to a support substrate, such as a carrier frame, to ensure that the circuits are not damaged during manufacture and/or use of the appliance. Flexible circuits commonly have a terminal portion where the plastic insulation is removed to expose at least one surface of the flat flexible conductors so that the flat flexible conductors can be connected to other conductors electrically. When a flexible printed circuit board is placed upon and soldered to a hard printed circuit board, connection terminals of the respective printed circuit boards to be soldered together must be properly positioned relative to each other. A flexible printed circuit (FPC) electrical connector is often used to electrically connect electrical circuits of an FPC to electrical circuits of a printed circuit board or to electrical conductors of an electrical cable. An opening is defined in the housing in communication with the slots for receiving an end portion of a flexible circuit whereby conductive traces printed on the flexible circuit board electrically engage the contacts. An actuator is attached to the housing for securing the flexible circuit to the connector. The flexible circuit connector comprises an insulative housing mounted to the rigid circuit board. A plurality of slots is defined in the housing for receiving and retaining conductive contacts electrically connected to the rigid circuit board. A zero insertion force (ZIF) connector typically provides an electrical interface between the flexible printed circuit and a printed circuit board.