Printed
circuit boards, often referred to as PCBs, are self-contained modules of
inter-linked electronic components that are commonly found in basic devices
like radios to more sophisticated computer systems. Circuits are made using
thin layers of conducting material "printed" or deposited on the
surface of a substrate or an insulating board. Once the circuit is laid,
individual electronic components can be placed on or through the surface of the
substrate and then soldered to complete the inter-connecting circuits. Contact
fingers along the edges of the substrate serve as connectors to other printed
circuit boards or some external electrical device, such as an on-off switch. A
PCB may consist of circuits that perform one single function or several
functions.
Printed
circuit boards come in different forms, but the most commonly used types based
on their construction include multi-layered, double-sided, and single-sided
boards. Single-sided boards, as the name suggests, have components on one face
of the substrate. When components are too many for a single-sided board,
double-sided boards may be considered. With double-sided boards, electrical
connections are made by drilling holes all the way through the substrate so
that each side can be inter-linked in appropriate locations. The inside of the
holes are plated with a conducting material. A multi-layered board, on the
other hand, features a substrate that contains several
layers of printed circuits, which are carefully separated by insulating
layers. Components on the surface are connected using plated holes drilled down
to the proper circuit layer, effectively simplifying the device's circuit
pattern.
Printed
circuit board components can be electrically connected to their proper circuits
using two methods, namely, through-hole technology, and the more recent
surface-mount technology. Through hole technology requires thin wires and
leads, pushed through the small plated holes in the substrate and they soldered
to connection pads on opposite sides of the board. Surface mount technology, on
the other hand, eliminates the time-consuming process of drilling holes into
boards as well as the space-consuming connection pads that are inherent with
through-hole applications.
