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WHAT'S FPC

An introduction to the flexible print circuit board (flexible PCB)
In recent years, there is a significant reduction in size as well as weight of portable electronic products such as mobile phones, digital cameras and camcorders because of the built-in electronic components. Many of these electronic components have the wire and the terminal soldered on the probe inside the zone of a circuit board for electric current connection. Often the use of flexible boards is to have the connection of electric current among various circuit boards. A flexible board is also used for electric current connection between a camera module and other parts of a circuit board.

The structure of flexible circuits has significantly become more important in recent years. It is because the structure, as compared to that of a rigid PCB, offers more advantages. A flexible PCB is lighter by weight and slimmer and smaller by size. It also has characteristics including a better extension and flexibility, and a higher density of the wiring. A flexible PCB can have a 3-dimensional wiring and its appearance can be modified according to the space limitation. Because of its flexibility, a controlled weight and other similar characteristics, a flexible circuit offers a typical efficiency for electronic packaging. For a high quantity of production, the cost of production can be significantly reduced by combining the flexible circuit with a more efficient production procedure.

A description for general flexible PCB
A flexible PCB includes a flexible board that offers the wiring and the connection pad. The conduction was achieved via wirings surrounding the flexible board. The printed circuit board (PCB) used in the flexible PCB is made by brazing the copper clay laminate onto a resin baseboard and then it is fitted into an intact circuit board, either by adhesive agents or thermal pressure, to achieve a multilayer connection. A circuit board may have one or more than one multilayer conduction, and this is similar to having one or two sides of the surface of a main circuit board. A circuit board usually provides many layers of functions in extra, for example, an insulating layer, an adhesive layer, a compressing layer and a hardened layer. A typical plastic baseboard of an optical conduction circuit board is made by polyimide or other similar engineering plastic materials, such as polyether-imides or PBT. Some adhesive agent, e.g., resin adhesive, is applied on the top of the baseboard, and then majority optical fibers are placed on top of it.

A typical flexible PCB includes many tape or linear types of conduction wires. The conduction wires are covered with a layer of some insulating material to form a piece of flexible and relatively soft circuit structure. A hole may be a conduction wire for connecting a part of the circuit that has been exposed from the molded insulating layer to other electronic components. Electronic deigns, such as an integrated circuit, a photo-electric switch, etc., can be placed on a suitable site of the flexible PCB and be connected to each other. In general, the front and the back of a flexible PCB are covered with an insulating layer to prevent the generated wiring to touch wirings of other circuit boards.

A description for the application of flexible PCB
Flexible PCB has been used very commonly because of a low cost, an easy assembly in the interconnecting system, and a minimum occupied space.

Most often, a flexible PCB is used when a 3-dimentional connection is required, for example those connections of between circuit boards, between a circuit board and a wafer, and between wafers that have a limited space, or the connection for packed multilayer rigid circuit boards. Majority flexible circuit is used for portable electronic products such as laptops, mobile phones, PDA and information equipments. For example, a flexible PCB can be used for making connections between the LCD, or between a floppy drive, a hard drive or a main board with the CD-ROM. A hard drive includes a disc that is inside the box, a disc that is supported and rotated by a spindle motor, and a read and write head that is driver-driven, a driver that is voice coil motor driven, a plate unit, and so on. On each component, a read and write head is connected to a relay terminal of the flexible PCB (in the following it will be mentioned as the flexible circuit board relay), and other relay terminals of the flexible PCB are connected to the main soft PCB.

A flexible circuit that is combining with optical fibers and electronic components has become more important nowadays. As the area of optoelectronics expands, more applications are available. A flexible PCB can be used to assemble an extended bus to facilitate multiple communications among remote electronic components. According to the function, flexible PCB can be divided into four categories: the conduction wire, the printed circuit, the connector, and the integrated function system. Because of the light and slim characteristics of a high-functional flexible PCB, the circuit has to be glued onto a carrier-like support plate to prevent damaging the circuit during the assembly. At the terminal part a flexible circuit there is usually a plastic insulator, which when removed, at least one side of the flat and flexible conductor will be exposed to be connected to other electric conductors. When a flexible PCB is placed and soldered onto a rigid PCB, the position of these two boards has to be well-aligned for their connecting terminals to be joined together. A flexible PCB electric connector is often used on electric connection or cable’s electric conduction between a circuit of a flexible PCB and a circuit of a printed circuit board. A closed circuit is defined as what is packed in a connection that accepts the slot of a flexible circuit terminal, and therefore there is a contact point of the switch-off’s conductive trace on the flexible PCB. An actuator is added to a closure that fixes the flexible circuit onto the connector. The connector of a flexible circuit has an insulating package arranged on top of the rigid circuit board.

Majority slots are defined as a package for accepting and maintaining a contact with the electric conductor of a rigid circuit board. A typical connection of “zero inserting force” offers an electric interface between the flexible PCB and the circuit board.

A future for the flexible PCB
A flexible PCB used for transmitting signals among interconnected electronic products, its circuit on the flexible cooper-clad laminate board is developed through exposure, etching and so on. A flexible PCB is mainly applied on the surface assembly of electronic components such as IC, resistors, capacitors, and connectors to implement functions of the electronic product. Because of a growing demand for a smaller and slimmer electronic product, the characteristics of flexible PCB, i.e., thin and soft, is going to make the development of flexible PCB to continue for quite a while. On the other hand, the development of flexible PCB will also facilitate the booming of the market for electronic products.

 
 
   
   
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