The Most Comprehensive Guide to Choosing Circuit Board Components

Circuit board components are the parts that make the Printed Circuit Boards (PCBs) work better than they could have without these components. If you are looking to buy a circuit board, important considerations must be made about the parts therein.

In this article, we make a comprehensive review of the different electronic circuits that go into making the PCB.

What are PCB Components?

Before we make a PCB components list, let us understand what these components. Put simply, these are the different electronic components mounted or inserted into the circuit board. Without these parts, it might be impossible for the PCB to actualize the full potential.

The choice of a PCB component to go for depends on the target applications, as these parts have specific functions. Your PCB manufacturer can offer better guidance on how to choose the best parts.

Handpicking Your PCB Components: How to Identify the Parts

One of the challenges to choosing a circuit board component is to understand how the parts are labelled. When you understand that, it becomes a lot easier to figure out the type of component it is and where it is required.

Several parameters go into the identification of these parts, but we have made a list of some of the pointers to these parts.

Below are some of the parameters that should help you understand how the components function:

Electrical vs. Mechanical

This is one of the parameters for identifying the PCB components. These parts can either use a mechanized process or toe the electrical line.

The electrical PCB parts are those that leverage electrical power or electrical energy. They can also be placed or used on the PCB, via either the Through-Hole Technology (THT) or the Surface Mount Technology (SMT).

On the other hand, the mechanical PCB parts are the ones that use a mechanized process, typically involving the use of metals, like bronze, aluminum (the most-used), copper and steel.

Passive vs. Active Circuit Board Components

Another way to pinpoint the type of PCB component you have is to check the functions. These functions can either be passive or active.

The passive or active components are peculiar to the circuit boards using the mechanized process.

On the one hand, we have the passive components as the parts that do not allow for the transfer of electrical energy through them. Since they are passive, these parts tend to have some of the following features:

  • Passive PCB components have a silk screen printing atop the circuit board.
  • You can also identify the passive PCB components via the two (2) leads.

Examples of the passive PCB components are:

  • Batteries
  • Connectors
  • Inductors
  • Resistors
  • Capacitors and
  • Fuses

On the other hand, we have the active circuit board components. As the name suggests, these are the PCB parts that have an active usage. You can be sure that these components allow the transfer or electric current or current flows.

One of the major reasons for the use of active PCB components is because of the versatility, allowing for the usage with both the SMT and the through hole mounting process technologies.

Integrated Circuits (ICs) and diodes are some of the examples of active PCB components.

Using Reference Designators as PCB Components’ Identifier

You can also use the reference designators of the parts to identify them. While this might be a bit of leaning to the technical side, it can be easier if you paid attention to the guides or the corresponding alphabets and codes.

Below is a tabular representation of some of the reference designators for some of the popular PCB components:

Reference DesignatorsPCB Components Denoted
ICIntegrated Circuit
LEDLight Emitting Diode
CBCircuit Breaker
TBTerminal Block
JJack or Jumper
ZDZener Diode
VRVariable Resistor
KContractor or Relay
MOVMetal Oxide Varistor

Identify the Board’s Usage

The PCB components used in a circuit board may differ by the usage of the board. The more complex the PCB is to be, the higher the types of components to be used for that purpose.

For perspective, there are two major board uses of these parts. They can be used with either the motherboard or the daughterboard.

Here is the difference between the two;

  • Motherboard: this is the major or the primary circuit board. It typically includes the connectors and the major components for other circuit boards to be mounted.
  • Daughterboard: this is the alternative circuit board that serves as an expansion of the motherboard. The daughterboard typically needs components to aid the attachment to the motherboard, from where it would get access to the memory and the Central Processing Unit (CPU).

PCB Components List

Now that we have discovered some of the best ways to identify the common components, let us now look deeper into the parts.

Here is a breakdown of the different parts that go into the manufacturing process of Printed Circuit Boards (PCBs):

1. Resistors

This has to be one of the simplest PCB components to understand. As the name suggests, resistors are meant to “resist,” to “stop” or to “prevent something.”

It is imperative to also mention that the function of resistors as a two-way passive PCB part is to keep the other circuit boards’ components safe.

How does the Resistor Work?

The first thing that the resistor does is to control the current flows or the electric current that flows through it.

The second thing it does is to restrict current flows or divide the voltages. That way, it would be terminally impossible for excessive electrical signal to flow into the board.

The third function of the resistor is to make an excellent dissipation or removal of the excess current. To do this, the resistor first convert the excessive electric current into heat. This would then be dissipated or passed out of the circuit board.

2. Capacitors

Denoted by the reference designator (C), capacitors are the second most important PCB components after resistors.

It is also pertinent to mention that the capacitors are the opposite of the resistors, in the sense that these components help to hold electric current. With the intent to enable stored energy, capacitors are designed to keep as much electrical charge as possible.

How Capacitors Work

In addition to holding electrical charge, capacitors can also function in the following ways:

  • Current Restriction: no doubt that capacitors aid electrical current storage, but they can also restrict the same. For context, capacitors can block Direct Current (DC) and at the same time, allow the Alternative Current (AC) to pass.
  • Power Conservation: this is the primary function of the capacitor. It first collects and holds the electrical energy. It would then release this energy or current whenever more power or electric current is needed in the Printed Circuit Board (PCB).

Although capacitors can store energy, they also have some downsides. Here are some of the flaws of the capacitors:

  • Limited Stored Energy: the capacitors only store energy minimally and that is because of the tiny battery capacity and the limited storage capacity. To that end, you can be sure that the energy or electric current stored in a capacitor wouldn’t last long.
  • Capacitors have Limited Functions: due to the minimal energy stored, capacitors are not used for major functions. For example, they are used as a form of “backup power” or “filtering,” which involves the usage of the stored energy to replace the main power as a way of preventing the data from resetting or getting lost.

3. Diodes

If you are looking for a PCB component that doesn’t make an excessive restriction of current flows, but does it in a way that it is balanced, it has to be the diode.

Best described as an “energy redirector,” the work of the diode includes the following:

  • One-Way Current Flow: diodes allow electric current to only flow in one direction. That way, you can be sure to identify if the pathway is the wrong direction or not. Typically, it works by allowing the current to flow from the anode (+) to the cathode (-).
  • Current Regulation: the main reason for the use of diodes in electronic circuits is to prevent current flows in the wrong direction. For this to work effectively, the diode first places a zero resistance in one direction and a high resistance in the other direction. That way, it would be easier to identify and block the current from flowing in the wrong direction.

There are different kinds of diodes you can choose from, but the Light Emitting Diodes (LEDs) are the most popular. LEDs are the type of diodes that emit light.

You can also choose from a handful of other diodes, including:

  • High-speed switching diodes
  • Zener diodes and;
  • Photodiodes: this type of diodes work by capturing energy from the photons of light.

4. Integrated Circuits

Denoted by either ‘IC” or “U,” the Integrated Circuits are one of the core components used in Printed Circuit Boards (PCBs).

What makes them unique is the fact that they serve as a “multi-function powerhouse” for the circuit boards, in the sense that they house most of the important components.

An IC typically includes the following:

  • Capacitors
  • Resistors and
  • Transistors

One would expect that a circuit board component with such voluminous components would be larger, but the reversal is the case with the IC. It is usually in the form of a wafer of semiconductor material, and that is because of the shrinking in size.

Types of ICs

There are two major types of Integrated Circuits (ICs), and these are the digital and the analog. The choice of which to go for depends on the purpose.

On the one hand, you can use digital ICs for consumer electronics and selected computers. On the other hand, analog ICs are best used for radio and audio frequency amplification purposes.

5. Sensors

As the name implies, the function of the sensors is to “sense” or “sniff out” the changes in the environmental conditions. For this to work, the sensors have to detect the changes first before generating the corresponding electrical signals.

The following is a detailed breakdown of how the sensors work in a Printed Circuit Board:

Environmental Change Detection

The first thing the sensors do is to detect or find out the physical changes in the environment. These changes can range from:

  • Motion
  • Heat
  • Noise
  • Moisture to pressure and;
  • Light

Signal Distribution

In addition to detecting the physical changes in the environment, the sensors also generate the response for the same in the form of electronic signals. These signals are then sent to the other electronic components mounted on the PCB.

6. Silicon-Controlled Rectifier (SCR)

Shortened to SCR and also known as Thyristors, the Silicon-Controlled Rectifier is a type of circuit board component that is composed of four silicon layers, which are higher than the PNP compositions found in transistors.

SCR as Transistors

Essentially, the Silicon-Controlled Rectifier (SCR) can be best described as “two transistors working together” because of the collaborated functions of regulating higher amounts of power and voltage.

Difference between SCR and Regular Transistors

The most obvious difference between the SCR and the transistors is that the former only uses a single pulse to activate the switch, unlike the consistent application of current in bipolar transistors.

7. Transformers (T)

Transformers are mostly used to enable energy transfer in circuit boards. The process of transferring this energy is called “induction” and it does that by first transferring the electrical energy from one circuit to another. Afterward, it makes a real-time conversion of the electrical energy by either increasing or decreasing the voltage.

Transformers vs. Resistors

One may want to compare the functions of the transformer to that of the resistor, as they appear to have similar functions.

The big difference between the two is that the transformer helps to “transform” the voltage via the provision of more electrical isolation than the controlled resistance obtainable in resistors.

Properties of Transformers

If you are to identify a transformer in an electronic circuit, here are some of the pointers to look for:

  • Windings: these are also called the “inductive circuits.” The function of these windings is to server as energy reception and delivery points. The inductive circuits comprise of the primary winding, which is for the source circuit (where the energy comes from). It also comprises of the secondary winding, which is where the energy goes to.
  • Soft Iron Core: the soft iron core on the transformer typically has two (2) coils of wire wound around it. These are the primary coil, which is used with the source circuit, and the secondary coil used with the secondary winding – which is where the energy is being transferred.

Benefits of Transformers in PCBs

The obvious reason for having a transformer in an electronic circuit is to streamline the energy transfer process, but there is more to it.

The transformer also helps to break down the larger or higher amounts of power and voltage into smaller and manageable electric currents.

That way, the current would be maximized in the circuit board, while reducing the chances of overloading the equipment.

8. Fuses

While most of the PCB components work to regulate current and transfer electrical energy if required, the fuses help to do much more.

The function of a fuse in a PCB is to provide overcurrent protection, whereby it protects the board from getting damaged when there is a current surge or excessive current supply.

Fuses also help to protect the traces and PCB wires from catching fire or melting.

9. Inductors

Inductors, denoted by the reference designator (L), are the PCB components used for energy storage. They are also one of the passive circuit board components, similar to capacitors and resistors.

It is worthy of mentioning that the Inductors share a similar design and function as the capacitors, in the sense that they are used to energy storage. However, there is a slight difference between the two.

Unlike the capacitors that store energy electrostatically, the inductors use the magnetic field process of storing energy.

The major benefit of the magnetic field energy storage design is that it allows the inductors to allow for energy generation when current flows through the magnetic field.

10. Switches

Switches (S) do what just their names imply – they enable you to switch things on and off. It is imperative to mention that the switch is more of the “power button” of the electronic circuit, in the sense that it controls the flow of current in the circuit.

How the Switch Works

The switch works by switching or interfacing between the open and closed circuit, which signals opening or closing the circuit.


There are different types of electronic switches in terms of the appearance or physical construction. You can find them in the following variants:

  • Rotary switches
  • Push buttons
  • Push-button switches
  • Slider switches
  • Toggle switches
  • Micro switches
  • Levers and;
  • Key switches

11. Battery (BT)

Batteries are no doubt, one of the commonly-used PCB components and you don’t want to miss having one in your circuit board.

With the primary function as providing backup stored power, the battery helps the different Integrated Circuits (ICs) to keep functioning.

The Power Storage Option

Batteries are able to store and provide backup power because of the flexible storage of chemical energy and the conversion of the same into usable electronic energy.

How to Maximize Batteries in PCBs

If you are looking to maximize batteries in your circuit board, there are a couple of things you must do.

The first is to ensure that the battery uses an external circuit that allows for the electrons to flow from one electrode to the other.

How do I Choose the Right PCB Components?

Certain factors must be considered if you must pick the best PCB components. Below is a list of some of the important factors to look into before you settle for a PCB component:

Choose the Process Technology

The Through Hole Technology (THT) and the Surface Mount Technology (SMT) are two of the popular process technologies used when placing semiconductor materials on modern electronics. While the former involves making holes on the bare board, the latter has to do with using surface mount devices to make these placements.

You should discuss extensively with your PCB manufacturer to know the pros and cons of the two and pick the one that delivers the best results for your electronics project.

Go for Flexibility

The manufacturing process of circuit boards can include PCB assembly, fabrication and prototyping.

Your goal is to choose the PCB components that would allow for flexible configuration of the board.

Generally, the Surface Mount Technology (SMT) appears to offer more flexible usages and you may want to go for that.

Consider the PCB Footprints

The footprints of these PCB components are as important as where they would be placed on the circuit board. The footprints range from the land pattern, the design technology and the dimensions.

One thing you must have in mind is that there may be a need to make custom footprints for these components, especially when the footprint is not available on the database.

The Height Limitations

Some PCB components have height limitations, in the sense that they may be oversized or not fit into the board.

For that reason, it is imperative to consider the height or space on the circuit board and use that as a basis for choosing the components that correspond.

Make a Design Outline

Whether you are looking to make a prototype or fabrication of the PCB, one thing you must do is to have the design outline readied.

The basic design outline serves as a basis for getting an overview of the different positions of the components.

Ideally, you are to use this outline to determine the required height and positioning of the components on the circuit board.

Wrapping Up

PCB components are very vital for the successful design of the boards. Your PCB designer will help you make a better choice. At the end of the day, the choice of circuit board components will determine whether the electronics project will be successful or not.