What is a PCB?

The team at Macias Sensors is convinced that the future of electrochemical analytical systems is in PCB-based platforms.

But… what are PCBs?

In this post we explain that in detail.

Introduction to PCBs

Every day we interact with multiple electronic devices: smartphones, laptops, TV…. A myriad of inventions that make our lifes easier and keep us entertained.

Nowadays, all these devices are compact and light. But that was not always the case. They used to be rather big and heavy. So… how was this transformation accomplished?

While there have been a lot of advances in microelectronic fabrication that have certainly helped reduce and lighten electronic devices, PCBs have also been a huge contributor. Let’s see how.

How were the first electrical connections?

The arrival of electricity to homes and industries kickstarted the development of new products. But it also brought a new challenge: how do we get electricity to these places?

The initial solution was rather simple. We just needed a cable between the source (electricity generating plants) and the device or building.

This solution is still used for several applications. In fact, the electricity network still uses this approach. Similarly, our home electricity installation also uses cables. While this solution works for certain applications, it is not suitable for absolutely everything.

As electronic devices became more and more complex, cabling became increasingly difficult.

The more components a device had, the more cables were needed. This resulted in two big problems:

  1. Space limitations: cables themselves occupy space. Therefore, the more complex the device, the bigger it became.
  2. Increased weight: due to the large amount of cables, more complex devices were also much heavier.

These two complications eventually led to the development of PCBs.

The rise of the PCBs

Cabling limitations were dramatically reduced with the arrival of PCBs. Thanks to this technology, connections between the different components of an electronic devicce became compact an light. This allowed to reduce the size of these products and made the consumer electronics market boom.

But… what is a PCB, exactly?

What is a PCB?

PCBs, or Printed Circuit Boards, are boards that interconnect electronic devices using thin printed copper tracks instead of bulky cables.

A basic PCB layer is composed of 4 parts or sublayers:

  1. The substrate: this sublayer is foromed by an insulating material. Its function is to support the printed circuit without shorting the different tracks. It is normally made with a mixture of fiberglass and epoxy, such as the FR4, the most common PCB substrate. However, there are other options out there such as ceramic substrates for high temperature applications, polyimide for flexible applications or even PET for cases were transparent PCBs are required.
  2. The printed circuit: this sublayer is formed by a thin copper film. This copper film is treated to generate the different tracks that will connect to the electronic components.
  3. The soldermask: this sublayer is formed by an insulating material. It has been designed to protect the printed circuit during the soldering of the electronic components. While green is the most common colour for the soldermask, it is normally available in other colors as well.
  4. The silkscreen: this last sublayer is optional. Its function is either decorative or informative. It normally contains company logos and information about the components and connections on the PCB. It is normally printed in white or black, depending on the soldermask colour chosen.

One of the big advantages of PCBs is that the sublayers of substrate and printed circuit can be laminated several times to yield multilayer PCBs. Most PCBs have between 1 and 8 layers of printed circuits, but for special applications, more layers can be stacked.

Another interesting characteristic from PCBs are vias. Vias are connections betwen 2 or more circuit boards located in different layers. Thanks to this characteristic, PCBs can hold complex circuits that have connections on both sides of the board.

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