All modern electrical devices require a huge number of connections to join together all the small components for their efficient working.
Earlier, these connections were made by wires that had to be soldered together. The wires have now been replaced by the printed circuit board, which is effectively a picture of the wiring that works equally well. The image is photographed onto a special board covered by a thin copper layer.
Chemicals are used to dissolve the copper and it leaves behind a thin film of metal bands to which all the components can be attached. These circuit boards are very light, compact and cheaper.
Below Circuit Boards info from Wikipedia (Read More):-
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, or traces, etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly (PCBA).
PCBs are rugged, inexpensive, and can be highly reliable. They require much more layout effort and higher initial cost than either wire-wrapped or point-to-point constructed circuits, but are much cheaper and faster for high-volume production. Much of the electronics industry's PCB design, assembly, and quality control needs are set by standards that are published by the IPC organization.
http://en.wikipedia.org/wiki/Printed_circuit_board
