Friday, May 06, 2005

What is PCB?

A printed circuit board or PCB interconnects electronic components without discrete wires. Alternative names are printed wiring board or PWB.

A printed circuit board consists of "printed wires" attached to a sheet of insulator. The conductive "printed wires" are called "traces". The insulator is called the substrate, and is made of "Pertinax" (a phenol formaldehyde resin) or a fiberglass-reinforced epoxy composite material.

A few printed circuit boards are made by adding traces to the substrate. The vast majority are manufactured by gluing a layer of copper foil over the entire substrate, sometimes on both sides, (creating a "blank PCB"), then removing unwanted copper, leaving only the copper traces. Some PCBs have a trace layer inside the PCB ("multi layer").

After the circuit board has been manufactured, components are attached to the traces by soldering.

There are three common methods used for the production of printed circuit boards:

1. Photoengraving, the use photomask and chemical etching to remove the copper foil from the substrate. The photomask is usually prepared with a photoplotter from data produced by a technician using computer-aided PCB design software. Some people produce low-resolution photoplots by printing a design to a laser printer, printing on the sheets used to make transparent presentations.
2. PCB Milling, the use of a 2 or 3 axis mechanical milling systems to mill away the copper foil from the substrate. A PCB milling machine (referred to as a 'PCB Prototyper' operates similar to a plotter, it receives commands from the host software package that controls the position of the milling head in the X/Y and sometimes Z axis. Data to drive the Prototyper is extracted from files generated in PCB design software.
3. PCB Printing, the use of conductive ink or epoxy to form traces directly on substrate material. Is similar to PCB milling in terms of hardware and data used.

PCBs are rugged, inexpensive, and can be highly reliable. They are harder to repair than wire wrap boards. They require much more design than either wire-wrapped or point-to-point constructed equipment.

2 comments:

Anonymous said...

Nice Blog

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kelvin said...

Hi,
i m looking for some good printed circuit board manufacturing companies ,can some one please help me out.

Regards

kelvin.