Before circuit boards, electronics were hand-wired tangles bolted to metal pans
Old radios were built by soldering each component lead to the next inside a sheet-metal pan, sometimes with a wooden base. The results were heavy, fragile and expensive. The printed circuit board replaced that labour with copper patterns etched onto insulating sheets, and now sits inside nearly every electronic product.
A printed circuit board is a laminated stack of copper and insulating layers, the copper etched into traces and pads that act like flattened wires. Components are soldered onto pads on the surface, which both connects and holds them. Boards with copper on more than one side use vias, drilled holes lined with metal, to link the layers. Designs range from single-sided to double-sided to multilayer stacks with copper between every sheet. Hiding traces inside frees surface space and allows far denser layouts, and boards with more than four copper planes spread alongside surface-mount parts, though they make repair and modification nearly impossible.
The advantages are economic. Laying out a board takes effort, largely handled now by design software, but only once. After that, huge batches can be made at the same time and components mounted and wired in one automated step, far quicker and cheaper than older point-to-point or wire-wrap methods. The global market for bare boards passed 60.2 billion dollars in 2014 and was put at 80.33 billion in 2024.
The idea took decades to mature. In 1903 German inventor Albert Hanson described layered foil conductors on insulating board, and in 1904 Thomas Edison tried chemically plating conductors onto linen paper. Arthur Berry patented a print-and-etch process in Britain in 1913, Max Schoop flame-sprayed metal through masks, and Charles Ducas patented electroplated patterns in 1925. John Sargrove's machine, running from 1936 to 1947, sprayed metal onto Bakelite and turned out three radio boards a minute. The Austrian engineer Paul Eisler, working in Britain, invented the printed circuit as part of a radio around 1936.
War accelerated things. Around 1943 the United States mass-produced proximity fuzes whose circuits had to survive being fired from a gun. The Centralab division of Globe Union screen-printed conductors and carbon resistors onto ceramic plates, a classified process that placed passive components as well as wiring on one substrate, a step towards integrated circuits. Harry Rubinstein received IEEE recognition for that early work only in 1984.
Source: Printed circuit board
