Printed circuit boards or PCBs are used to support and connect electronic components via conductive tracks, pathways and signal traces composed of copper sheeting laminated to a non-conductive base.
Printed circuit boards were first developed at the beginning of the 20th century. Albert Hanson, a German scientist and inventor, first described the use of multiple layers of foil conductors laminated to an insulating board in 1903. The renowned inventor Thomas Edison began experimenting with the chemical processes of plating conductive materials to linen paper a year later. It would be just under ten years before a patent was registered by Max Schoop, an American who catalogued the concept of flame-spraying metal onto a board via a patterned mask. Designs continued to evolve, and in 1927 Charles Durcase patented a new method of electroplating circuit patterns.
Paul Eisler invented the first printed circuit in England in 1936 while working on a radio set. Less than a decade later, the USA began to utilise the technology on a considerable scale in order to manufacture proximity fuses for use in the second World War. Three years after World War II ended, the US government made the printed circuit available for commercial use. It would be a further decade until circuit board became commonly used in consumer electronics.
As with many innovative designs, the PCB board was initially manufactured as a military defence solution. The development of anti-aircraft weaponry required electronic circuits able to withstand the vibrations of gunfire which could also be produced quickly. The initial design involved screen-printing a ceramic plate with conductive metallic paint and carbon material for use as resistors, with disc capacitors and sub-miniature vacuum tubes soldered into place. The technique was functional, and the US Army subsequently filed a classified patent. Harry W. Rubenstein, credited with coming up with the world's first printed circuit board, was given the Cledo Brunetti Award for his efforts some 40 years later.
PCB manufacturer will typically build a printed circuit board from four items: laminates, copper-clad laminates, copper foil and resin impregnated B-stage cloth. Most boards nowadays are constructed from laminate material, with copper pre-applied to both sides. Unwanted copper is removed by simple methods, leaving the required traces of copper behind in a technique known as subtracting. In additive methods of PCB manufacturing, copper traces are electroplated onto a substrate, although this process is much more complex.
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