Printed circuit boards, Physics

 

INTRODUCTION: A printed circuit board (PCB) IS a sheet of insulating material usually Bakelite with metallic circuitry photo chemically formed upon that material or substrate. On this sheet small holes are given for accommodating the diverse components of the circuit to be assembled. Interconnections between components are achieved by means of conducting paths (metallic conductor pattern) running path or through the substrate is called tracks. Tracks meet components to which they are to be linked through a larger conductor area known as land or pad. The electrical connection between a land and component‘s terminal is achieved by means of a solder joint. Every circuit has its own PCB but the process of manufacturing is more or less the same. First of all the Bakelite sheet of the proper size is taken. The whole sheet is covered with a copper strip on it; the circuit lines are drawn and covered with an enamel layer. After the paint is dried up into solution of ferrite chloride with few drops of hydrochloric acid (HCl). The copper (except the painted portion) is dissolved in the solution later on; this paint is cleaned off by petrol or kerosene. On this copper strip, holes are provided to accommodate the components. To protect from dampness, the copper strips are covered with a layer of varnish.

ADVANTAGES OF PCB: The copper strips over the PCB serve the purpose of the wires hence much wire is saved. Circuit charactistics can be maintained without introducing variation in inter-circuit capacitance. Mass production can be attained at lower cost. Inspection time is decreased as probability of error is removed. As the components are tightly fixed and therefore risk of short circuiting is minimised.

 

Posted Date: 7/9/2012 3:17:09 AM | Location : United States







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