Printed Circuit Boards: A Brief History and Components

Printed circuit boards, also known as printed wiring boards or printed wiring cards, are parts of an electronic device which connect its internal components together to create a circuit, which makes the whole device function. This is commonly seen in computers but can also be found in any other device that uses electricity. To find out what a circuit board looks like, all you just need to do is look at a computer’s motherboard.

printed circuit boardsWhen printed circuit boards were created, it had solved the issue of complex circuitry with electronic components. To find out when it was first used, it can be stated that it started around the 1900’s. Back in 1925, Charles Ducan was able to submit a patent for an electronic pattern that was printed onto an insulated board. It was in 1943 that Paul Eisler was able to build one of the first circuit boards.

Before printed circuit boards were widely used, “point-to-point construction” was the technology found in contemporary electronic devices. This is where each component of an electronic device was painstakingly connected with wires from one part to another. These devices were bulky and would easily breakdown. When repairing such a device back then, it would call for replacing either the connecting sockets for each component, or replacing the wire connecting them, or both. Wires were sensitive that time and the insulation for each wire was not as sturdy compared to the wires now. Some of the first devices that used circuit boards were the gramophones and radios built during the 1920’s.

Manufacturers would use wood as the board and they would rivet the electronic components in place on one side and then run the wires on the other side of the board. During the 1950’s and 1960’s, the use of was then known and a few patents were filed to further improve their efficiency. With the initial designs, the circuits were placed only on one side of the board, but eventually, multilayer boards, or a board with more than one printed circuit on it, were created.

A typical circuit board would have a hole in it where an electronic component would fit in place. This is called a Plated-Through Hole. Once the component is in place, it is then soldered either by hand or by machine to secure it. Each hole would have a copper ring around it, called an annular ring.

When two circuit boards need to be connected to each other, a section of the board is set where part of the copper pattern is exposed. These are called “fingers” and are always located at the edge of the board. They would then be pushed into connectors that are installed in the other circuit board, just like how components of a computer are attached to a motherboard. If the circuit board needs to be cut in a certain place, manufacturers would place a V-score or a “mouse bite” on the board. These are partial cuts on the board so that anyone can snap off one part of the board cleanly and easily.

A solder mask is placed over the circuit board to protect the copper paths that are already printed onto it. The solder masks are what gives the circuit boards its typical green colour, though some boards may be red. The solder mask also protects the board from accidental solder jumps, or when an extra solder suddenly connect two copper circuits accidentally.

For some components that cannot be installed through holes, some boards would have a slot put on the board itself. This is typically used if the connecting part is not rounded. A silkscreen layer is used to give a label to each part of the board. The labels are usually white so that they can easily be read.