What are PCBs? A Quick History

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Printed circuit boards or PCBs make up the skeleton of any electrical product. They form the foundation for circuits – and of modern electronics as we know it.

They have made electronic products available to the masses and, even today, they are still a driving force behind innovation.

Before the invention of PCBs, circuits were difficult to make as, therefore, were electronic products. Technicians would have to physically wire components together in a very time consuming process.

And even then these circuits were extremely liable to breaking and relied very heavily on the competence of the wiring technician.

Wire-wrapping made the process of connecting components slightly easier.  It involved wrapping small wires around ‘posts’ to form a connection.

These types of circuits often lasted longer and were easier to repair. But they could only fit into very large products and were still relatively difficult to make.

Soldering Printed Circuit BoardAs the electronics industry grew, so too did the pressure on manufacturers to reduce the size and expense of electronic products.

The development of the first PCB kick started a wave of innovation that is still gathering momentum today.

What are PCBs?

Printed circuit boards as we know them today are essentially a series of ‘lines’ or ‘tracks’ which  various ‘holes’ where components can be attached.

PCBs alone are not circuit boards. They are sometimes referred to as dumb technology in that, by themselves, they cannot actually transfer any information and are not ‘live’.

When physical components are inserted into the holes the technology becomes smart as it allows signals and power to travel between the devices creating a live circuit.

What makes up a PCB?

A PCB is made up of several layers laminated on top of each other in a lasagna-like structure. The base layer is designed to give the board some rigidity, so the PCB is not damaged.

Traditionally, this layer is made of fiberglass or “FR4” as it is more commonly known.

An example of the ways in which innovations in PCB design drives innovation in broader electronics is the utilisation of flexible high-temperature plastics as PCB base layers.

By using a flexible plastic, designers have been able to fit circuits in places where they couldn’t previously, for example in items of clothing.

On top of the base material is a layer of copper. This is the conductive layer of our lasagna and is what transports signals and power around the circuit.

If you have heard reference made to ‘multi-layer’ PCBs, this will usually refer to the number of copper layers contained within a PCB. More advanced products usually require several copper layers to function properly.

Finally, the circuit is topped with a layer of soldermask. This is essentially an insulating layer to prevent unintended connections being made between the solder and the copper and is what gives PCBs their distinctive green colour.

Printed circuit boards have allowed our societies to flourish. They have enabled many innovators to achieve their dreams and have become absolutely essential to our everyday lives.

It is worth remembering that almost all of our daily actions have been made possible in some way by printed circuit boards.