A PCB or printed circuit board connects and supports electrical or electronic components with pads, conductive tracks and layered sheets of copper laminated with a non-conductive substrate. Components are usually soldered directly to the PCB for mechanical fastenings and electrical connectivity. PCB’s are used for everything except extremely basic electronic products. The electrical products they are used for include passive switch boxes.
The first patent for a printed wire PCB was issued in the early 1900’s. This was a new method for creating a direct electrical path by printing with a stencil and electrically conductive inks. This is where the terms printed circuit and printed wiring originated. Bulky radio rube wiring was replaced by the first printed wiring board in 1943. The earlier PCB’s were constructed from Masonite, Bakelite, thin wooden planks and layered cardboard. Flat brass wires were inserted through drilled holes and bolted or riveted onto the board. This style was popular in the 1920’s for gramophones and tube style radios. For additional information please visit here.
Laminates mixed with a wide range of materials became popular during the 1950’s and 1960’s but the PCB’s were still single sided. Once side of the board contained the components and the other the circuitry. This began replacing bulky cables and wiring. The process eventually evolved so the PCB assembly involved plating copper onto the walls made by the drilled holes. This enabled the electrical connection of circuits on both sides of the board. Brass was replaced with copper because it carried the electrical current better, was easy to manufacture and was much cheaper. A patent was issued for the assembly process by the United States Patent Office in 1956.
The new process used a base material such as melamine securely laminated to a layer of copper foil. Additional methods included screening, stencils, rubber stamping and hand printing. Patterns were used to punch the holes to match the position of the terminals or component lead wires. The leads were inserted into the laminate material through non-plated holes. A bath of molten solder was then used to float or dip the card. The solder connected the leads to the traces and coated the traces. Different types of components were attached to the board with washers, rivets and tinned eyelets. This was the first attempt to construct a multi-layer PCB. For more details visit this site.
The process has changed due to new plating processes, double sided boards and surface mount pad technology. The latter was originally explored during the 1960’s but is associated with the 1980’s. Solder masks were applied to reduce the corrosion occurring in the components and traces. Epoxy compounds became known as conformal coating. Screen printing was used to place the inks on the panels prior to assembly. The spacing and circuitry became smaller during the 1970’s and hot air soldering methods were being used. Today, multi-layer circuit boards have been designed to save space. The circuit board and integrated circuits have continued to decrease in size. The circuit boards are also much more flexible.