PCB relay-the ultimate guide

PCB relay – the ultimate guide

Table of Contents

If you’re looking for an introduction to PCB relay, you’ve come to the right place. This guide will provide everything you need to know about these essential components, from their basics to more advanced applications. 

By the end of this article, you’ll have a clear understanding of what PCB relays are and how they can benefit your designs. So let’s get started!

What is a PCB relay?

PCB Relay

A PCB relay is a type of relay that uses printed circuit board (PCB) technology to form its electrical contacts.

This makes it an attractive option for applications where reliability and compact size are important factors, such as industrial control systems and telecommunications equipment.

PCB relay can also be manufactured using automated assembly processes, which helps to keep costs down.

Function of PCB relay

A PCB relay is a form of electrically-actuated switch used to turn ON or OFF an electrical circuit. It consists of a coil of wire that creates a magnetic field when energized with the current.

This magnetic field then operates a mechanical switch, which can be used to control the flow of electricity in the circuit. PCB relay is often used in industrial applications where high currents, such as motors and heating elements, need to be controlled.

They are also helpful when it is essential to isolate different parts of an electrical circuit, such as in computer systems where sensitive components must be protected from voltage spikes.

How does a PCB power relay work?

How does a PCB power relay work

A PCB power relay works using an electromagnet to control the opening and closing of a set of electrical contacts.

The circuit is activated when current flows through the electromagnet, which in turn pulls the metal armature towards it, making contact with the other set of contacts and completing the circuit.

When current is no longer flowing through the electromagnet, it loses its magnetic field, and the armature is released, breaking the circuit.

Types of PCB relays

There are many different types of PCB relays available on the market today.

Electromagnetic relays

Electromagnetic relays

An electromagnetic relay is a type of electrical relay that uses an electromagnet to open or close a switch. The switch may be either normally open (NO) or normally closed (NC), depending on the design of the relay. When the electromagnet is energized, it creates a magnetic field that either opens or closes the switch, depending on the type of relay.

Electromagnetic relays are the most common type of relay and are used in a wide variety of applications, such as safety circuits, logic circuits, and light dimmers.

Reed relays

A reed relay is a type of electromagnetic relay that uses an enclosed switch, called a reed switch, to open or close the circuit. Reed switches are made from two thin strips of metal, called reeds, that are hermetically sealed inside a glass or plastic envelope. When the magnetic field from the coil is applied, it causes the reeds to move and make contact with each other, thus completing the circuit. Reed relays are used in applications where space is limited, such as in computer memory circuits.

Solid-state relays

A solid-state relay (SSR) is an electrical relay that uses semiconductor devices, instead of electromagnets, to open or close the switch. This makes them more resistant to shock and vibration than other relays. Solid-state relays are used in a variety of applications, such as motor control, process control, and lighting control.

Hybrid relays

Hybrid relays

A hybrid relay is a type of electrical relay that uses a combination of electromechanical and solid-state components to open or close the switch. Hybrid relays are used in applications where the advantages of both types of relays are needed, such as in high-current applications where the reliability of an electromechanical relay is important, but the solid-state components are needed for resistance to shock and vibration.

Thermal relays

A thermal relay is a type of electrical relay that uses a bimetallic strip to open or close the switch. The bimetallic strip is made from two different metals that have different coefficients of expansion. When the strip is heated, one metal expands more than the other, causing the strip to bend and make or break contact with the other set of contacts. Thermal relays are used in applications where current needs to be controlled, such as in motors and heating elements.

PCB design requirements for electromagnetic relays

PCB design requirements for electromagnetic relays

For an electromagnetic relay to function properly, the PCB it is mounted on must meet certain requirements.

  • First, the PCB must be made of a material that will not distort easily, such as fiberglass resin.
  • In addition, the PCB must be thick enough to support the relay – a thickness of 1.6mm is generally considered sufficient.
  • Finally, the PCB must have conductors with the appropriate thickness – typically, 35µm for signal paths and 70µm for power paths.
By following these guidelines, a PCBA manufacturer can help ensure that electromagnetic relays perform as intended.

Common precautions for PCB relay mounting

A few common precautions should be taken when mounting PCB relay.

  • It is important to ensure that the PCB relay is mounted in the correct orientation – the coil should be horizontal, and the contacts should be vertical.
  • In addition, it is important to avoid placing the relay too close to other components, as this could cause interference.
  • Also, ensure the PCB relay is mounted on a firm and level surface to avoid any potential issues.
  • Finally, it is important to ensure that the PCB is properly grounded – this will help protect the relay from electrical surges.

How do you test a PCB relay?

How do you test a PCB relay

You’ll need a multimeter and a power supply to test a PCB relay.
1. First, connect the power supply to the relay.
2. Then, use the multimeter to measure the resistance between the relay’s terminals.
3. If the resistance is infinite, then the relay is open and needs to be replaced.
4. If the resistance is low, the relay is closed and working properly.
5. Finally, the relay is likely defective and needs to be replaced if the resistance is somewhere in between.

How to solder a relay on a circuit board?

There are a few things you’ll need to solder a PCB relay onto a circuit board:

1. Soldering iron

Soldering Iron
This heating element will apply heat to the solder and create the joint between the relay and the circuit board. There are different wattages available, so ensure you get one that’s powerful enough for your project.

2. Solder
This material will be melted to create the joint between the relay and the circuit board. It comes in either lead or lead-free varieties, so ensure you get the right type for your soldering iron.

3. Wire cutters
You’ll need these to cut the wire leading to the relay so you can access the terminals.

4. Flux

This material helps the solder flow and adheres to the surfaces being joined. It’s important to use flux when soldering electronic components, as it helps to prevent oxidation and ensure a strong connection.

5. De-soldering braid
This is optional, but it can be helpful to have on hand if you need to remove any excess solder from the joint.

  • To start, use the wire cutters to cut the wire leading to the relay. Then, apply flux to the exposed terminals on the relay and the circuit board.
  • Next, heat your soldering iron and apply solder to the joint. Be sure to apply enough heat so that the solder flows evenly.
  • Finally, use the wire cutters to trim any excess wire, and you’re done!


PCB relay is a vital component in many electronic devices. They are responsible for controlling the flow of electricity in various applications. It is important to follow certain guidelines when designing and manufacturing circuit boards to ensure they function properly.

For more information about PCB components, just visit IBE website to read more posts!

Sign up for newsletter

Get latest news and update

Newsletter BG