Guideline

What is a PCB and How Does a PCB Work?

What is PCBs

A Printed Circuit Board or a PCB acts as a foundation for connecting or “wiring” different components to one another, thereby enabling smooth flow of electrical signals in a circuit. PCBs are extremely sensitive and are prone to be damaged easily. Therefore, they must be handled carefully to function properly. In this article, you will learn all about printed circuit boards, including what is PCB and how PCB works.

Structure of a PCB

A Printed Circuit Board consists of a non-conductive material with copper traces. The copper traces are etched on the base PCB material, which allows the current to pass through different components present on the board. There different type of PCBs according to their material, technologies and application. But most commonly, we classified PCBs by their copper layer count, such as single-sided PCB, double-sided PCB and multi-layer PCB. A complete PCB includes PCB bare board and electronic components assembly. It is formed by soldering various components such as capacitors, resistors, ICs, transistors, etc., on PCB bare baord.

PCB and Components

Types of PCBs

There are many types of PCBs according to their material, features, technologies and applications. Here, we will talk about some most common types.

1. Single-sided PCB

It is the simplest type of PCB, having one copper layer. The electronic components attached to it are on one side and copper traces are on the other side. Such PCBs are not only inexpensive but also easy to use.

2. Double-sided PCB

These PCBs are used in more complex circuits as they have copper traces and components etched onto them on both sides. The different layers are connected with the help of vias.

3. Multi-layer PCB

In multi-layer PCBs, there are more than two copper layers. And the copper traces are separated by insulating material between them, and vias are used to connect all the layers. They provide benefits such as better component density and signal integrity and are frequently used in electronic devices such as computers, mobile phones, television, etc.

4. Rigid PCB

Such PCBs are inflexible and comprise materials such as fiberglass or epoxy, providing strength and stability. They are best used in conditions where the board must maintain its shape and can tolerate mechanical stress.

5. Flexible PCB

These PCBs are usually made of polyimide, allowing them to bend and mold their shape according to the requirements. They are most used where flexibility of movement or vibration is required.

6. Rigid-Flex PCB

Such PCBs have the combined properties of both flexible and rigid PCBs and are used in complex applications that require stability as well as flexibility.

7. High-Frequency PCB

High-Frequency PCBs are specially made to withstand high-frequency signals without losing signals or interference. They are good at maintaining signal integrity and impedance.

8. HDI PCB

The high-density interconnect PCBs are used to maximize the density of components and reduce the size of the board. They consist of micro vias and fine pitch elements to achieve higher circuit density.

Also read: The Ultimate Guide to Understanding PCB Thickness

Components of a PCB

Questions like “What is PCB board?” are closely related to components. The following are the most used components in a PCB.

  • Resistors: Resistors provide electrical resistance to current flow. Different types of resistors are used for different purposes. The most commonly used resistors are carbon composition resistors (commonly used in various applications), metal film resistors (usually used in precision circuits), and wire wound resistors (used in power circuits and amplifiers).
  • Capacitors: Capacitor is used to store energy in the electronic deivce. Thanks to this feature, the circuit board can be used at all times. A number of capacitors are widely used in electronic products, including ceramic capacitors, electrolytic capacitors, tantalum capacitors, etc.
  • Inductors: Inductors store energy by creating a magnetic field. They help power different equipment, regulate voltage levels, and cancel any undesired noise. One of their important applications is in RF (radio frequency) circuits through which engineers use them in filters or amplifiers, etc.
  • Potentiometers: Potentiometers regulate the amount of current that passes through it. It is commonly found in amplifiers and many audio equipment. They are usually used to control loudness, tone, and brightness of different devices.
  • Transformers: Transformers transfer energy between circuits along with adjusting the voltage in the process. They aid electrical energy in going in different directions and in changing the voltage.
  • Diodes: Current only flows in one direction in diodes. Diodes are usually made of silicon or germanium.
  • Transistors: Transistors are also known as the “gatekeepers” as they regulate electrical power and the passage of current in a circuit. They are made of materials like silicon or germanium. They come in various forms including field-effect transistors (FETs) and bipolar junction transistors (BJTs).
  • Silicon-Controlled Rectifier (SCR): The SCR (known as thyristor) allows a current to flow in a single direction. It is adaptable and can turn on and off at specified points in the circuit. Its main role is to control the power in the circuit.
  • Integrated Circuits: Many electric components such as transistors, resistors, capacitors etc. are attached to a small silicon wafer to create integrated circuits (ICs). They are then joined by engineers to create complex circuits to perform various functions.
  • Oscillators: Crystal oscillators use a crystal’s mechanical movements to create accurate frequency. They are made of an electronic circuit and a crystal (typically quartz). They are an important part of timekeeping equipment such as GPS systems, watches, clocks, etc.
  • Switches and Relays: With the help of switches and relays, the movement of power and the accurate functionality of the devices can be assessed. A switch either allows or hinders the flow of current in a circuit. It also serves as a bridge thereby connecting and disconnecting the electrical channel.
  • Sensors: Sensors work by receiving different types of input, such as sound, pressure, temperature, heat, humidity sensors, position, vibration., etc, and producing an output in the form of a signal. These signals are either passed electronically through a network for further interpretation or can be translated into meaningful information at that very instant.

PCB copper trace

How Does a PCB Work

  • Design of the PCB

The design of the PCB is laid out by using specialized software. The circuit designer places the components, trace routes, and layers according to requirements, functionality, and availability of space.

  • Fabrication Process

The fabrication process starts with the completion and conclusion of the design process. It occurs in the following steps.

  • Fine copper foils are covered on both sides of the substrate material to form a conductive layer.
  • The copper layer is then removed either by etching or printing techniques which leaves behind the needed pattern of traces and pads to form the circuit.
  • The next step involves drilling holes at specific points onto the PCB that lead components and vias to maintain electrical connections between different layers.
  • A solder layer is then applied to the copper traces and pads leaving some areas for soldering components. To identify the components and label them, a silkscreen layer is also added there.
  • To protect the exposed copper and ensure the strength of the board, a solder layer is usually applied at the end.
  • Adding Components to the PCB

After the completion of fabrication process, then comes the turn of adding components to the board which is done in two ways.

By using through-hole technology (THT), components having leads are fixed in the already drilled holes on the board and the leads are soldered on opposite sides.

By using surface-mount technology (SMT), components that do not have leads are directly stuck onto the PCB through soldering.

  • Connection between Components

The connection between the mounted components is carried out through the conductive traces present on the PCB. These traces act as a gateway for the current to pass freely through it, thereby creating a circuit.

  • PCB Testing

After the components have been soldered on the board and the connection has been confirmed between them, the PCB undergoes rigorous and continuous testing to ensure that it is working properly. These tests include continuity checks, signal integrity analysis, and functional testing.

  • Integration

When the PCB functionality is proven successful, it can then be used in the systems or devices for which it was designed. It may be connected to other PCBs or external devices to complete the overall system.

Benefits of PCBs

PCBs are the most fundamental component of any electronic device. PCBs provide benefits such as dependability, flexibility, ease of use, and ability to be produced in larger quantities. They also help in minimizing wiring problems and making assembly time faster along with making the circuit efficient and effective to use.

Conclusion

Printed Circuit Boards have become the backbone of devices in today’s world. They not only prove to be reliable but also aid in the cost-effective, large-scale production of devices that we can make today. After reading this blog post, readers may have a good grasp of questions like “What is PCB?” “How does a PCB board work?”

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