Printed Circuit Boards

Published:2011/3/11 2:58:00 Author:LiuQiaoyan From:SeekIC

A printed circuit board, is an independent unit of interconnecting electronic components that can support and connect components by using conductive pathways, signal traces etched from copper sheets laminated onto a non-conductive substrate. PCBs are used in almost all the devices produced for commercial purposes in our daily life.

The circuit is formed by a thin layer of electroconductive materials that printed on a surface of an insulating board known as the substrate. Every single components neet to be placed on the substrate and soldered to interconnecting the circuits, and at the edge of the board are the contact joints to other PCBs or to external electrical devices. A printed circuit board can provide circuits with single function as well as multiple performances.

The construction of printed circuit board can be divided into three kinds: multi-layered, double-sided, and single-sided. The first type refers to a substrate made up of layers of printed circuits separated by insulations. The components on the surface connected through plated holes drilled down to the appropriate circuit layer. In this way simpify the pattern of the circuit greatly. The second one have components on both side of the board, connections are also made by drilling holes through the substrate. Single-sided boards have the components on one side.

The ties among components are set up in two ways: technology through the hole and technology through the surface mount. With the former, connections built only when the components have been soldered on the substrate. While with the latter, components can contact the printed circuits directly. The surface mount technology requires more care in placing the components, but it take less time and space compared with the hole technology.

PCBs require more effort for layout and are high-cost than wire wraps, but faster for high-volume productions and the process of soldering can be finished all automatically. The conducting layers are typically made of copper foil while the insulating layers are laminated together by epoxy resin prepreg. The board is covered by a solder mask that is green, some in blue, black, white or red.

There are two other circuits related to the printed circuit board: the integrated circuit and the hybrid circuit. Hybrid circuit looks like printed circuit board but contains components that are grown on the surface instead of being placed and soldered. Integrated circuit also known as IC, or microchip, functions similar to PCB, but owns more components that are grown on the surface of a small chip of silicon electrochemically. The related integrated circuit model is SN54LS138J.

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