Printed circuit board
Laminated board connecting electronic components via etched copper traces.
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A printed circuit board (PCB), also known as a printed wiring board (PWB), is a laminated sandwich structure composed of conductive and insulating layers. Each layer features a pattern of traces, planes, and other features etched from copper sheets that are laminated onto or between sheets of a non-conductive substrate. PCBs serve to connect or wire electronic components together, with components fixed to conductive pads on the outer layers, typically by soldering, which provides both electrical connection and mechanical fastening.
Layers
For boards with more than one side, vias—metal-lined drilled holes—enable electrical interconnections between the conductive layers. PCBs can be single-sided, with one copper layer; double-sided, with copper on both sides of a single substrate; or multi-layer, consisting of stacked substrate layers with copper plating between each and on the outer surfaces. Multi-layer boards allow for much higher component density, as circuit traces on inner layers free up surface space.
Manufacturing
Their popularity grew alongside the adoption of surface-mount technology, though they make repair, analysis, and field modification far more difficult and often impractical. Today, PCBs are used in nearly all electronic products, having largely replaced earlier methods like wire wrap and point-to-point construction, which are now rarely used. While PCBs require significant design effort to lay out the circuit, manufacturing and assembly can be automated, and mass production is cheaper and faster than alternative wiring methods because components are mounted and wired in a single operation. Large numbers of boards can be fabricated simultaneously, and the layout need only be done once.
Predecessors
Small quantities can also be made manually, though with reduced benefits. The development of modern PCB methods began in the early 20th century, with early work by inventors such as Albert Hanson, who described laminated foil conductors, and Charles Ducas, who patented electroplating of circuit patterns. Austrian engineer Paul Eisler invented the printed circuit as part of a radio set around 1936, and by 1941 multi-layer boards were used in German naval mines.
Quick Facts
- Field
- Electronics manufacturing
- Known for
- Laminated sandwich structure of conductive and insulating layers for connecting electronic components
Facts from the source article.
Lore & Background
The development of methods used in modern printed circuit boards started early in the 20th century. The Centralab Division of Globe Union submitted a proposal using thick-film technology, screenprinting metallic paint for conductors and carbon material for resistors on a ceramic plate, with ceramic disc capacitors and subminiature vacuum tubes soldered in place. The resulting patent was classified by the U.S. Army and assigned to Globe Union. Printed circuits did not become commonplace in consumer electronics until the mid-1950s, after the Auto-Sembly process was developed by the United States Army.
Reader's Guide
Printed circuit boards are fundamental to modern electronics, enabling mass production of circuits cheaper and faster than earlier wiring methods such as point-to-point construction or wire wrap. They require additional design effort to lay out the circuit, but manufacturing and assembly can be automated, and electronic design automation software is available to do much of the layout work. PCBs can be single-sided, double-sided, or multi-layer, with multi-layer boards providing much higher component density. The rise in popularity of multilayer PCBs with more than two, and especially more than four, copper planes was concurrent with the adoption of surface-mount technology.
However, multilayer PCBs make repair, analysis, and field modification of circuits much more difficult and usually impractical. Since the 1980s, surface mount parts have increasingly replaced through-hole components, enabling smaller boards and lower production costs, but making repairs more challenging. Recent advances include 3D printed electronics and HDI technology, which allows for denser designs with blind/buried vias and microvias.
Frequently Asked Questions
How does a PCB connect electronic components together?
Instead of discrete wires, a PCB uses etched copper pathways—called traces—embedded within insulating layers to carry current between parts. Components are fixed to designated pads, generally by soldering, creating a compact and reliable circuit layout.
What did printed circuit boards replace in earlier electronics?
Before PCBs became standard, circuits were often assembled by hand-tying individual wires to component pins, a technique known as wire wrapping. PCBs made assembly far faster, more compact, and dramatically more reliable for large-scale production.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Printed circuit board (CC BY-SA 4.0).
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