What Are Printed Circuit Boards (PCBs)? Types, Uses & How They're Made

If you have an electronic device, it probably has a printed circuit board (PCB). These boards are responsible for the operation of electronic devices.
So what exactly are PCBs, how are they made, and why are they essential? Read our blog to find out!

Key Takeaways

Printed circuit boards (PCBs) are the backbone of modern electronics, providing the pathways that allow power and signals to move between components.
PCBs evolved from the 1940s to today, shifting from simple wiring replacements to complex boards that support high-density integrated circuits.
Each PCB is built from multiple layers, including a fiberglass base, copper circuits, soldermask, and silkscreen, designed for durability, conductivity, and precision.
High-quality PCB assembly is essential, and ITAR-certified manufacturers ensure reliable, military-grade performance for any electronic device.

What is a Printed Circuit Board?

Printed Circuit Boards are boards that connect various points together through lines and pads. They allow signals and power to connect between two physical devices. While the term “printed circuit board” is typically used, other terms to describe these include “printed wiring board” and “printed wiring card.”

Before PCBs came into existence, circuits were constructed using point-to-point wiring. This led to the failure of wire junctions and short circuits if the insulation aged or cracked. It was because of this that the need arose for a more durable unit.

PCBs also became a need as electronics became more common in consumer goods. To ensure that these everyday electronics had all of the necessary components, the size and manufacturing costs needed to be reduced.

History of the Printed Circuit Board

So how did PCBs come to be and transform over time?

history of pcb

1940s – The Beginning

PCBs were first developed to connect discrete components like resistors and transistors. They replaced fragile point-to-point wiring, offering a more reliable and durable way to build circuits.

1960s – Early Adoption

While electronics still relied on discrete components, PCBs became widely used in consumer, military, and industrial devices, simplifying complex circuits.

1970s-1980s – Integrated Circuits Arrive

The emergence of integrated circuits (ICs) allowed PCBs to hold more components in a smaller space. By the 1980s, PCBs commonly featured numerous chips, improving performance and reducing size.

1990s-Today – Modern PCBs

Modern PCBs connect mostly chips instead of discrete components, supporting electronics with thousands to hundreds of millions of transistors, making them essential in virtually all devices.

What are Printed Circuit Boards Made of?

Printed Circuit Boards are composed of multiple layers, each designed to serve a specific purpose in ensuring the board’s structural integrity, electrical functionality, and durability.

Here’s a closer look at each component.

1. Substrate (Base Material)

The substrate is the foundational layer of a PCB and provides mechanical support to all other layers. The choice of substrate affects the PCB’s durability, heat tolerance, and electrical performance.

FR-4

The most common substrate material is fiberglass, historically designated as FR-4, which stands for “Flame Retardant 4.”

FR-4 is a woven fiberglass that has been treated to resist heat and combustion, making it ideal for electronic applications.

Alternative Materials

Other materials include:

Polyimide for flexible boards
Phenolic resin for lower-cost applications
Ceramic for high-performance and high-temperature environments

2. Copper Layer

Laminated onto the substrate is a thin copper foil, which forms the conductive pathways of the PCB. Copper allows electricity to flow between different components, enabling the board to function as intended.

The copper can be found as a single layer on simpler PCBs or as multiple layers in more complex boards, which are connected via plated-through holes or vias.

The thickness of the copper layer can vary depending on the current requirements, typically ranging from 0.5 oz to 2 oz per square foot.

3. Soldermask Layer

The soldermask layer is applied over the copper to protect it from oxidation and prevent accidental electrical shorts. It is typically made from a polymer-based material and comes in various colors, though green is most common.

This layer ensures that solder adheres only to the intended pads during assembly, reducing the risk of bridging or unwanted connections. In addition to insulation, soldermask adds a degree of physical protection to the delicate copper traces, increasing the PCB’s durability.

4. Silkscreen Layer

The top layer of a PCB is the silkscreen, which provides visual markers such as letters, numbers, symbols, logos, and component identifiers.

Silkscreen is usually printed using epoxy ink and helps technicians and engineers identify where components should be placed or replaced. Beyond assembly guidance, the silkscreen contributes to quality control and maintenance by making boards easier to troubleshoot.

5. Additional Layers (Optional)

Advanced PCBs may include extra layers like:

Prepreg layers (insulating layers that bond copper sheets together)
Copper planes for power or ground distribution
Specialized coatings, like conformal coatings, for added environmental protection.

Flexible and rigid-flex PCBs may also incorporate polyimide or other bendable materials to allow the board to twist or fold without breaking the circuitry.

By carefully combining these layers, PCBs achieve a balance of mechanical strength, electrical conductivity, and resistance to heat, moisture, and mechanical stress, all of which are crucial for modern electronic devices to function reliably.

What are Etched Circuits?

Printed circuits are essentially etched circuits, created by removing unwanted copper to form precise electrical pathways. These circuits can range from simple single-layer designs to complex multi-layer boards.

1. Applying the Copper and Photoresist

Each PCB layer starts with copper foil laminated onto a fiberglass or plastic base.
This copper is then coated with photoresist, a light-sensitive material that becomes resistant to chemicals when exposed to light.

2. Exposing the Circuit Pattern

A negative image of the circuit design is placed over the board. Light shines through this pattern onto the photoresist, hardening the areas that represent the desired circuit paths.

3. Etching the Unwanted Copper

Any photoresist that didn’t harden is removed during an acid bath, which also washes away the exposed copper underneath, creating the finished circuit traces.
The hardened areas remain intact, forming clean, defined copper pathways.

4. Final Layer Bonding

Once each layer is etched, the layers are aligned and glued together to build the final PCB structure, especially in multi-layer board designs.

Why Hallmark Nameplate?

The functionality and construction of electronics have developed dramatically over the years. As technology has advanced, the need for printed circuit boards has increased. Even after PCBs were invented, most electronics featured more discrete components than chips.

However, as manufacturers attempt to make smaller and less expensive devices, chips are more common than discrete components, making PCBs that much more important.

Hallmark Nameplate is a company that features experienced professionals when it comes to assembling PCBs. Our services include PCB assembly, testing, PCB encapsulation, prototype PCB assembly, and PCB engineering.

As an ITAR-certified producer of PCBs and a member of the Special Graphic Imaging Association (SGIA), Hallmark Nameplate holds itself to a high standard, producing military-grade products.

When having PCBs manufactured or assembled, it is imperative that they are done to the highest quality to ensure maximum functionality of electronic devices. If you’re in need of PCB assembly services, get in touch today!

Want to learn more? Read our complete guide to PCBs and electronic assembly.

Related Resources from Hallmark Nameplate

Frequently Asked Questions About Printed Circuit Boards

What is a printed circuit board (PCB)?

A printed circuit board is a laminated board that mechanically supports electronic components and electrically connects them through copper pathways etched onto its layers. The core is typically FR-4 fiberglass laminate, clad with copper foil that is imaged and etched to form the circuit, then protected with a solder mask and marked with a printed silkscreen layer.

What are printed circuit boards used for?

Printed circuit boards are used anywhere electronic components need to be connected reliably and repeatably. In industrial settings that means machine controllers, motor drives, sensor interfaces, instrumentation and control panels. In medical devices it covers diagnostic equipment, monitoring systems and implantable electronics. Aerospace and defense use them in avionics, navigation and communications. Consumer and automotive applications span everything from infotainment to engine management. Any product with a power source and a control function almost certainly contains one.

What is the difference between a printed circuit board and a printed wiring board?

The two terms describe the same physical product. Printed wiring board, or PWB, is the older designation and still appears in legacy drawings and some military specifications where documentation has not been revised. Printed circuit board became the dominant term as boards took on more of the circuit’s function through embedded passives and controlled-impedance routing. For procurement purposes, treat them as interchangeable but confirm the specification being referenced.

What are the different types of printed circuit boards?

Boards divide by layer count and by substrate flexibility. Single-sided boards carry copper on one face and suit simple, cost-sensitive designs. Double-sided boards use both faces with plated through-holes linking them. Multilayer boards stack additional copper layers separated by insulating prepreg, enabling dense routing and dedicated power and ground planes. Rigid boards use FR-4; flexible boards use polyimide and can bend in the final assembly; rigid-flex combines both to eliminate connectors and cable harnesses. HDI boards use microvias and fine-pitch geometry for space-constrained designs.

What industries use printed circuit boards?

Essentially every manufacturing sector that builds powered equipment. The highest-regulation users are medical device manufacturers working to ISO 13485, aerospace and defense suppliers working to ITAR and IPC Class 3, and automotive manufacturers working to IATF 16949. Industrial equipment, telecommunications, instrumentation, food service equipment and energy systems all rely on them as well. Regulated sectors typically specify tighter inspection criteria, documented traceability and higher IPC acceptance classes than commercial work.

What is IPC Class 3 and when do you need it?

IPC-A-610 defines three acceptance classes for electronic assemblies. Class 1 covers general electronic products where function is the only requirement. Class 2 covers dedicated service products where extended life is expected but uninterrupted service is not critical. Class 3 covers high-performance products where continued performance is essential and downtime cannot be tolerated, which is why it is typically specified for medical, aerospace, defense and life-safety equipment. Class 3 imposes tighter tolerances on solder joints, annular rings and defect allowances, and costs more to produce.

How do you choose a PCB manufacturer?

Evaluate certifications against your regulatory requirements first, since ISO 13485 for medical and ITAR registration for defense work are threshold criteria rather than preferences. Then assess whether the supplier handles fabrication only or offers full assembly, testing and box build, because a single-source build removes handoff risk between vendors. Confirm the IPC acceptance class they routinely work to, their inspection methods including AOI and X-ray for hidden joints, their prototype-to-production path, and their domestic versus offshore sourcing, which affects both lead time and supply chain exposure.

What Are Printed Circuit Boards?