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Basic Knowledge Back to basics: What's a printed circuit board?

| Editor: Erika Granath

Much of the technology we use daily would not be possible without the invention of the printed circuit board (PCB). Not only did the PCB make it possible to downsize electronic equipment, but they also made the manufacture of powerful circuitry more cost effective. Today, PCBs are found everywhere—and while their physical characteristics vary enormously, they still conform to a few basic design principles.

Printed circuit board is the most common name but may also be called "printed wiring boards" or "printed wiring cards".
Printed circuit board is the most common name but may also be called "printed wiring boards" or "printed wiring cards".
(Source: Public Domain / Pixabay )

What is a Printed Circuit Board (PCB)?

Printed circuit boards are used to mechanically support and electrically connect electronic components. PCBs use conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate that does not conduct electricity. Electronic components are then added to the board and etchings are made on its surface, which allow the current to flow through the copper from component to component.

While the PCB is of the key concepts in electronics today, it’s important to remember that this hasn’t always been the case. The PCB revolutionized electrical engineering when it was invented back in 1936. To put it simply, the PCB made it possible to mass-produce electronic devices for the first time.

Printed circuit board is the most common name but may also be called "printed wiring boards" or "printed wiring cards".

PCB: The circuit board that changed the world

Prior to 1936, electronic circuits were wired “point-to-point” onto a chassis (often a wooden box). Each component was connected to the others using copper wire as part of a long, labor-intensive process. PCBs changed all that. Able to be printed in vast numbers using machines, this sped up production massively and made them cheap enough to use in all manner of products.

The first PCBs were used for radios and other military applications. After the end of World War Two, they found their way into industry and ultimately the fledgling market for consumer electronics. Today, PCBs can be found everywhere we look, from PC motherboards and memory sticks to mobile devices and controllers in household appliances. As a basis of modern electronics, they are present in medical devices such as scanning equipment and digital measuring devices. They are used in manufacturing machinery, from switches and controllers to monitoring equipment—and even the ma-chines used to design and make more PCBs. From consumer electronics and home appliances to automotive and aerospace applications, it is impossible to imagine the modern world without PCBs.

Different types of printed circuit boards

The most basic type of PCB is the original single-layer board which, as the name suggests, involves mounting one layer of copper on a substrate. Later developments led to double-layer and multi-layer PCBs, which saw multiple copper layers applied to two or more substrate layers. This made it possible to add a much higher density of components to the board and use them to create more powerful devices. While multi-layer boards did make maintenance more difficult, they soon became so cheap to make that it is now often more cost-effective to replace an entire board than to repair it.

Today, the most common substrate is FR-4 glass epoxy, though new materials have emerged as the popularity of PCBs has grown. Examples of PCB configurations include rigid PCBs, flexible PCBs, rigid-flex PCBs, and high-frequency PCBs. The different con-figurations often use different substrates.

Applications of printed circuit boards

Aluminium is mainly used in boards known as insulated metal substrates (IMS) or aluminum-backed PCBs. These boards are often used in applications where heat dissipation is important, such as in power switches or LED systems. An alternative is to use a more standard substrate and what is known as a heavy copper layer. Increasing the thickness of the copper to more than three ounces per square foot significantly improves heat dissipation, and the circuit is capable of handling higher currents.

Most PCBs are of a rigid construction, but if flexibility is required (e.g. in a wearable device) the copper layer can be mounted on materials such as Pyralux foil or Kapton, a flexible material that is also resistant to high temperatures. In fact, there are now al-most as many substrate materials as there are uses for PCBs.

A market that keeps on growing

It is now more than 80 years since the invention of the PCB, yet the worldwide market is continuing to grow. According to Lucintel’s Printed Circuit Board (PCB) Market Report 2019, the global PCB market is predicted to reach USD 89.7 billion by 2024, driven by a compound annual growth rate (CAGR) of 4.3 percent in the coming years.

As robotics, artificial intelligence, and the internet of things continue to transform our lives, the demand for digital electronic devices will keep growing, which suggests a bright future for PCBs. It seems safe to assume that this venerable technology will be in service for many years yet.

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