Printed circuit board

A printed circuit board (often abbreviated as PCB) is a technology used for cost-effective production of multiple instances of a module.

A thin fiberglass sheet has holes drilled in it, where the leads from components will be placed. It is then coated with a thin layer of copper; next, a pattern of 'resist' is applied, outlining a series of 'traces' which will connect together the components placed on the board. (This resist is usually printed on the board, hence the name.) The board is then placed in a chemical bath which dissolves the copper where it is not protected by the etch, leaving the traces.

The first PCB's were single or double-sided. Later, techniques for producing so-called 'multi-layered PCBs' were deveioped; a number of thin PCBs were created, and then glued together; this allowed the production of complex circuits which could not be 'routed' with only two surfaces.