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Circuit Board Components and What They Do

Circuit Board Components and What They Do

Circuit board components form the basis of its operation, enabling the controlled flow of electricity. They are also available in many types, each playing a distinct role in the working of the circuit and, therefore, the application device. Here’s more about these parts, their functions, how to identify them, and more.

What are Circuit Board Components?

Printed circuit board components are electronic or electromechanical PCB parts that allow it to perform its function. They can be power components, signal generators or receivers, signal conveyors, etc.

Some are prominent, while others are small and barely visible. And even though each part has its function, they must work together, interconnected by traces.

A typical PCB will have a few to hundreds of components—or even thousands. It depends on its size and intended purpose. They also come in different shapes, ratings, and more.

What do Circuit Board Components do on a Circuit?

Printed circuit parts generally control the flow of electricity (current). Individually, each part has a specific purpose—some, like ICs, process signals, while others regulate voltage.

Some protect the circuits from electrical faults, ensuring reliability and extending the PCB lifespan. Think of them as sections that make up a more extensive system to make it work as intended.

Soldering PCB parts
Soldering PCB parts

How are Circuit Board Components Connected?

Manufacturers mount PCB components using solder. To connect them electrically, they use pathways called traces and plated holes—called vias—to connect layers. The parts also use through-hole or surface-mount technologies to attach to the board.

Through Hole

Through-hole PCB types, as their name suggests, go through the board. They come with long leads to allow soldering on the opposite side, making them easy to assemble by hand. However, they require more space.

Surface Mount

Surface-mount types have shorter leads or no leads. They attach to the surface using soldering pads. These parts allow automated assembly more than manual and take up less space. On the downside, they do not attach firmly and are mostly small-sized.

Components of a circuit board and their functions
Components of a circuit board and their functions

How to Identify Components on a Circuit Board

You can use various methods to identify PCB parts: by visually inspecting them, using the marking that manufacturers place on the board, and with the help of the specific PCB datasheet.

Visual Matching

PCB parts are visually identifiable based on their shapes and other features. As you can see in the above image, each part has distinct physical characteristics. For example, electrolytic capacitors are cylindrical, while different ICs are blocks with pins on either side.


These are reference designators or codes printed on the silkscreen. They identify each part, allowing anyone working on the PCB to make correct identifications. Example codes are:

  • R – Resistor
  • C – Connector
  • U – Integrated circuit
  • T – Transformer
  • J – Connector
  • L – Inductor

PCB Datasheet

Manufacturers usually provide detailed specifications in a product’s datasheet. For a PCB, this information can be circuitry diagrams, layouts, etc. Referring to it can help you identify the various electronic and electromechanical parts, their interconnections, ratings, and more.

Passive and active PCB parts
Passive and active PCB parts

Types of Circuit Board Components

PCB components are either passive or active. “Passive” means those that do not rely on supplied power to function. Active parts do. The lists below include essential examples in each category.

Passive Components

  • Capacitors – charge storage, signal filtration, and voltage stabilization.
  • Inductors – used with various parts to store energy using magnetic fields
  • Resistors – restrict the flow of current
  • Varistors – offer protection against overvoltage conditions
  • Thermistors – use changes in resistance to measure temperature
  • Fuses – blow when current exceeds a preset value to offer electrical protection
  • Transformers – transfer energy between circuits using electromagnetism
  • Traces – current pathways that serve as electrical interconnections

Active Components

  • Diodes – control current flow direction
  • Transistors – signal switching and amplification
  • Integrated Circuits (ICs) – contain miniature parts that process and control electrical signals
  • Switches – control various circuits by connecting and disconnecting them
  • Voltage regulators – used to maintain constant voltage against a fluctuation

Common Circuit Board Component Problems

PCB parts are supposed to fit their function and location. However, that doesn’t sometimes happen. Reasons can vary based on the failure type. Common reasons for issues include incompatibility, damage to the component, and assembly problems.


A component may not fit your PCB due to its height or other physical properties and power rating. It could also be that it uses a different communication protocol than what you designed your board for.


Your PCB components may get physically damaged. That mainly occurs if you transport or store them without proper care. For example, a dusty or heat-damaged part may not work in the circuit, leading to partial or entire board failure.

Assembly Issues

Assembly problems include soldering defects and incorrect part placement. To avoid all these, follow proper design and assembly rules. Testing the PCB after mounting it with components also helps identify errors and correct them.

Common Circuit Board Component

How to Choose Circuit Board Components

The wrong choice of components could end up causing issues or cost more than necessary, among other problems. Consider the following factors when choosing the parts to use on your PCB.


A part can only serve its purpose. Functions vary from signal processing to current limitation and voltage regulation. Your selection should match the application requirement to ensure the board’s proper function.


PCB parts have different ratings for power resistance and other specifications. These are critical when selecting them, as the wrong rating could lead to a malfunction or damage. During the design phase, determine every requirement and choose your components based on that.


Only use what you can obtain quickly. Hard-to-find parts cause preparing your BOM to take longer than anticipated. In the event of damage, you won’t rework or repair the PCB on time. Be sure to contact your supplier early enough and note what’s available and what you need more time to obtain.


You want the parts reasonably priced and in line with your budget. That said, there may be better choices than inexpensive parts. Sometimes, they offer low quality and may only last for a while. Therefore, weigh your options and go for what fits your project needs.

The Future of Circuit Board Components

Electronic technology is a rapidly evolving field. Today, the PCB is growing smaller in size. That calls for miniaturization of its components. It also requires them to become more efficient in their power usage and heat dissipation capabilities.

With these developments, you can expect PCB components to become even smaller, multi-chipped, and more powerful. They will also become less costly and usable in many applications with new manufacturing technologies and materials.

It’s also possible that the parts will be high-speed and able to support ultra-high data speeds, given the advancement of 5G technology. With all these changes, future components will improve electronic devices and systems.


Circuit board components are critical parts that ensure its proper operation. The parts can be passive or active and serve various functions to operate the board in its end-use device or system. As we have seen, their proper selection is paramount, or your PCB could experience performance problems.


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