What is a Printed Circuit Board (PCB)? Meaning and Types

Estimated reading time: 8 minutes

Currently, PCBs make up nearly all electronic devices. The term printed circuit board (PCB) stands for “printed circuit board.” By serving as a solid foundation for new electronic technologies today, all of the small parts that are able to run a device will attach to this material in some way, and this material will thus create the necessary electrical pathways for those small parts to communicate with each other.

PCB and its uses

PCB is a flat non-conductive board made from a non-conductive material that will physically hold components. On this board, there are a series of thin copper wires called traces that transfer electrical signals from one component to another, similar to how wires transfer signals.

If there were no PCB, connecting all of these individual components together would create thousands of independent wiring harnesses; therefore, large-scale production would be impossible and undependable.

A PCB solves two major problems:

1. The physical mounting of the component will be in a specific location to facilitate the systematic assembly of components and scalability of manufacture.
2. The copper traces provide an established and stable electrical circuit to allow for consistent and reliable electrical transfer.

A completed circuit board with all electronic parts soldered onto it is called a printed circuit board assembly. Therefore, the difference between PCB and PCBA is that PCB is a bare circuit board, and PCBA is the finished, fully functioning circuit board.

How Does a PCB Work?

The job of a PCB, or printed circuit board, is very basic but very important; to direct power out through various parts of the circuit.

The first step in the process is a design; a schematic of the circuit that includes where each piece should go and how the electricity will travel through each of them. The PCB itself is often made from a type of fiberglass composite known as FR-4, which does not conduct electricity to keep electrical signals traveling through each trace from interfering with each other.

Tip: FR-4 is short for “Flame Retardant 4”.

Typically, the PCB will be assembled by connecting components to it by soldering them to their pads. Solder is a metal alloy that melts easily, forming a strong electrical and mechanical connection between the component leads (wires that come out of the component) and the pads on the PCB.

When power is supplied to the device, the PCB sends power to all of the components via its traces, and at the same time sends data signals through different traces to supply the components with the directions to operate. This organization of the flow of electricity is what makes a modern device so reliable and affordable.

What Components Make Up a PCB?

Although PCBs may look identical, they are actually multiple layers, pressed together to create a single panel. The following layers makeup what we call a printed circuit board:

Substrate: This is the main part of a PCB and usually is the largest area of the board. Typically made of FR-4 material, it serves as the structure (providing rigidity to the PCB), provides electrical insulation, and is flame-retardant.

Copper Layer: Each PCB has a copper layer that consists of thin copper foils laminated to the top and/or bottom of the substrate. Multiple layer PCBs will have copper layers separated by substrate layers, with the copper etched away to leave only the circuitry pattern (etched away) used to define circuit paths and points.

Solder Mask: The solder mask (green layer) is applied on top of a layer of copper and made using a polymer coating (hence the solder masks are commonly green, but may be red, blue or black). Solder mask prevents oxidisation of copper and prevents “solder bridges”, an inadvertent electrical connection between the two points.

The Silkscreen. The silkscreen layer is most commonly printed using white ink; it serves as a reference for engineers and assemblers to locate the various components on the PCBs (for example: “R1” for resistor).

What Kinds of PCBs Are There?

PCBs are classified mainly based on their layer count and rigidity.

It is classified by layers.

Single Sided – This is the simplest and most inexpensive type. The components and traces are on one side of the PCB. This type is used in devices like calculators.

Double Sided – This type has copper traces on both sides of the PCB. The two sides are connected together using plated holes called vias. This type is typically used in industrial controls and power supply circuits.

Three Layer – Used in smartphones and laptops. This type is made up of three or more copper layers that have been laminated together to allow for densification and complex signal routing.

It is classified by rigidity.

Rigid – Made from solid materials, such as FR-4. Rigids are unable to bend. Computer motherboards would be a good example of this.

Flex Circuit – Built on a flexible plastic film (such as polyimide). Flex circuits can be folded or bent to fit in places such as cameras and wearables.

Rigid-Flex Circuit – A hybrid combination that has a flexible tail connecting rigid boards. This eliminates the use of heavy connectors and cables and is ideal for aerospace and military applications.

The PCB Design and Manufacturing Process

To create functional PCB’s requires three essential stages: design, manufacturing, and assembly.

During the schematic stage, engineers will design a logic diagram and define how all the circuitry and connections of a PCB work with CAD software.

In the physical layout stage, designers will place the digital footprints on the PCB and then route the traces to connect them together without interfering with each other.

As part of the design process, Design Rule Checks are done to validate that the design meets the manufacturing capabilities required to prevent the PCB from failing due to out-of-spec components (e.g. trace spacing and size of holes).

Gerber files are exported from the CAD software. The Gerber files contain all the data needed by the factory to manufacture a PCB, including the copper layers, the solder mask, etc.

After the factory has received the Gerber files, the factory will begin the fabrication process by cutting a substrate for a PCB, drilling the holes, and etching the copper patterns using photoresist and Ultraviolet light.

Following the making of the bare PCB, assembly will commence. Pick-and-place machines automatically place surface mount devices on the pads. After that, the PCB’s pass through reflow soldering. The heat produced by reflowing melts the solder paste to permanently attach the SMD’s to the PCB.

Finally, prior to shipping to customers, the completed boards will be tested electrically with probes to ensure there are no open or short circuits.

Where Are PCBs Used?

PCBs are present in nearly every modern electronic product, with applications spanning industries and daily life.

• Consumer electronics: Dense multi-layer PCBs power laptops, smartphones and smart home devices; PCB innovation drives smaller, more powerful gadgets.
• Computers & office supplies: Desktop motherboards and office equipment (printers, routers) rely on PCBs.
• Automotive sector: A fast-growing PCB user—modern cars’ ECUs depend on PCBs. Advanced driver-assistance systems and EVs boost demand for robust automotive-grade PCBs.
• Industrial applications: Durable PCBs support manufacturing control systems, robotics, and cross-sector tech (e.g., fertilizer composition detection systems). They withstand harsh conditions.
• Medical field: Specialized PCBs enable reliable devices , often using compact rigid-flex designs.
• Military/aerospace: Cutting-edge PCBs operate flawlessly in extreme environments (radiation, G-forces), representing top-tier PCB tech.

Conclusion

Printed circuit boards are a simple yet incredibly important and powerful piece of technology. The use of printed circuit boards (PCBs) takes many forms from simple, single-sided PCBs to more complex, rigid-flexible PCBs that provide structural support and the electrical pathways that power our world. PCBs are also the foundational building block for much of the technology we have today in computers, mobile devices, and automobiles.