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Understanding Rigid PCBs: Definition, Materials and Types

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In the world of electronics, the rigid PCB is the most common type. Made using a single or multiple layers of rigid substrate material, this type of PCB can be found in the circuitry electronic products such as computers, telecommunication systems, automotive electronics, gaming consoles, and medical equipment. But what exactly is a rigid circuit board?

What is a Rigid PCB?

A rigid PCB — or rigid printed circuit board in full — is a type of circuit board that will not bend or flex when placed under pressure. It can be a single layer board for simpler circuits, or multi-layer PCB for complex circuitry. Here is a more detailed look:

Rigid PCB Definition

Rigid means not flexible or bendable, and this describes the most fundamental trait of a rigid circuit board. A PCB, on the other hand, is used to mean any type of printed circuit board. PCBs are used as substrates that are populated with electronic components.

A rigid PCB board is designed to be strong and able to support the load of the external forces, such as those from soldering or electromechanical contact, without bending or flexing. This makes it ideal for many types of electronics applications where the circuit board needs to maintain its shape and form over time.

Rigid PCB Materials

A rigid printed circuit board (PCB) is constructed out of one or more layers of substrate material with copper tracks etched into them to form electrical pathways. Through holes, called vias, are also drilled into the substrate. These serve to connect the various internal layers to one another.

The most commonly used rigid PCB materials for the substrate include FR-4 (fiberglass reinforced epoxy laminate), Aluminum, and even Polyimide. A rigid polyimide PCB, for instance, offers the advantage of higher heat resistance.

For the conductive layers that go in between the substrate layers, copper is typically used. The thicker the copper layer, the more reliable and robust the circuit board will be.

A cover layer called solder mask, which is usually green, is also added to the surface of the PCB as a protective layer. On top of the soldermask, a silkscreen layer is added to identify the components and provide other useful information about the circuit board.

Different types of rigid PCB boards
Different types of rigid PCB boards
Resource: https://hackaday.com

Types of Rigid PCB

PCB manufacturers, depending on the required features, make different types of rigid circuit boards. These are classed according to the number of layers of substrate material and copper tracks in board’s construction. Based on this classification, you have the single-sided, double-sided, and multi-layer rigid PCB.

Single Sided Rigid PCB

This is also called a one-layer rigid PCB. These types of rigid PCBs can be said to be the most basic form of the product. They feature a single layer of substrate material, a copper layer etched onto the surface and soldermask to act as the protective layer.

The single-sided rigid PCB is relatively inexpensive to produce. It’s also best used in applications where space is limited. Other applications of the single-sided rigid PCB include simple electronic experiments or prototypes.

Double Sided Rigid PCB

A double-sided rigid PCB is a printed circuit board that has two layers of substrate material and two copper tracks on its surface. To connect the layers, through-holes drilled through the board and plated with a conductive material.

The design of the double-sided rigid PCB is more complex compared to the single-layer variant, but it offers more features such as greater electrical stability and resistance to physical stress. Application examples include smartphones and tablets.

Multi-Layer Rigid PCB

A multi-layer rigid PCB has more than two layers of substrate material and copper tracks on its surface. The tracks are etched onto each layer, with interconnects drilled through the various layers to form vertical pathways for electronic components and other connections.

These types of rigid printed circuit boards are usually used in higher end electronic devices that require a high degree of complexity, such as computers. They also offer better electrical stability, greater reliability and higher performance compared to single-layer or double-layer rigid PCBs.

Customized rigid printed circuit boards
Customized rigid printed circuit boards
Resource: https://youtu.be/djBMQhjfbys

Rigid PCB vs. Flexible PCB

Rigid PCBs have been around for longer than flexible PCBs. They are also the more common type of circuit board, and used in the widest range of applications. However, they have their limitations when compared to flexible circuit boards.

1. Starting with a comparison of the flex and rigid printed circuit board materials, we can see noticeable differences. Rigid PCB substrates are typically FR4 or metal, while those of flex PCBs are usually polyimide.

2. Rigid PCBs also allow for greater component density and higher board stability than flexible boards (this is necessary when dealing with complex circuits that require many different components).

3. In terms of size and weight, rigid PCB boards are typically much larger and heavier than flexible boards. This makes it less suitable in some electronic devise such as medical implants.

4. Comparing costs, rigid PCBs are usually cheaper to produce than flexible ones. This is because the options for rigid PCB material are generally less expensive. The process to make rigid boards is also simpler.

5. Flex PCBs can withstand vibrations and other movements better than rigid PCBs. This makes them ideal for applications where movement and vibrations are expected, such as in robotics or aircraft.

What is a Rigid PCB Used For?

Rigid PCBs are used in many different types of electric and electronic devices, from simple experimental systems to complex industrial equipment. You’ll also find it widely used in many consumer products today. Here is a list of these uses:

  • Automotive applications – Rigid circuit boards can be found in car audio systems, alarms, airbag sensors and other automotive electronics.
  • Industrial control systems – These circuit boards are used to control industrial automation processes, such as those found in manufacturing plants.
  • Computer systems – Computer systems use rigid PCBs for their mainboards, memory modules, and other components.
  • Medical devices – Rigid PCBs are often used in medical equipment, from imaging machines to blood pressure monitors.
  • Consumer electronics – These circuit boards can be found in many consumer products, gaming consoles, televisions, digital cameras, and other household electronics.
  • Defense applications – Rigid PCBs are used in many military and aerospace applications, including guidance systems and other devices.
  • Scientific research – Rigid PCB boards are often required in the execution of various types of scientific experiments.
  • Telecommunications devices – These boards are commonly installed in different parts of telecommunication systems, like routers and modems.

Conclusion

The rigid PCB is an essential component of many electronic devices, from simple consumer electronics to complex industrial equipment. With several options for the base layer, it offers notable benefits such as greater component density and excellent durability. These PCBs are also designed in single and multi-layer variants, each offering its own unique advantages depending on the requirements of the application.

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