What is PCB Relay in PCB Board?

Have you ever wondered how the tiny components on your electronics boards control and transfer power? If so, then you’ve come to the right place! PCB relays are an essential part of circuit board assembly, allowing for the efficient operation of a wide range of electronic devices.

In this article, we will explore what a PCB relay is, its function and different kinds of relays used in PCB assembly, as well as the design requirements for electromagnetic relays and how to solder and test them. So let’s dive in and learn more about these powerful yet tiny pieces of technology!

What is a PCB Relay?

PCB relay

A Printed Circuit Board (PCB) Relay is an electrical switch used for power management in a circuit board. It operates like a regular relay, but is much smaller and lighter, allowing it to be placed directly on the board via through-hole technology. PCB Relays are commonly found alongside transistors, as they offer galvanic isolation which can help reduce interference between parts of the circuit. They are also suitable for high voltage applications due to their robust construction.

PCB relays come in various sizes and shapes, each with its own unique set of features and design requirements. The most common type is the electromagnetic relay, which requires careful consideration when soldering and testing due to their delicate nature. Furthermore, PCB relays must be designed with adequate spacing between components to prevent short circuits or overheating.

PCB Relays Function

PCB Relays are incredibly versatile and have many functions depending on their type. They can be used for high voltage switching, overcurrent protection and thermal protection. High voltage switching allows them to switch to high-frequency applications and high voltage signals, while overcurrent protection prevents the flow of dangerously high currents in the wrong direction. Thermal protection trips if the temperature exceeds a certain preset threshold.

These miniature switches make managing power efficiently much easier while maintaining a compact size. With proper design practices and testing procedures, PCB relays are an invaluable component in many circuits that can help ensure your electronics project runs smoothly!

What are the Different Kinds of Relays Used in PCB Assembly?

PCB relays are one of the most common components used in PCB assembly. They provide an efficient, cost-effective way to manage power and switch high voltage signals. There are several types of relays available for use in PCBs, each with its own advantages and drawbacks.

Electromagnetic Relay

Electromagnetic relays are one of the most commonly used components in PCB assembly due to their flexibility and cost-effectiveness. An electromagnetic relay contains an electromagnet that creates a magnetic field when activated, which then opens or closes the contact sets within the relay. This type of relay can be used with both AC and DC current and is typically used for high frequency switching applications or for controlling large currents.

Electromagnetic relays require only low power consumption and offer reliable operation under shock and vibration conditions. Ultimately, electromagnetic relays are a great choice for circuit board assembly due to their versatility and reliable performance.

Solid State Relay

Solid state relays (SSRs) are electronic switching devices that use semiconductors instead of electromechanical parts such as coils and contacts. They offer a number of advantages over traditional electromagnetic relays, including faster switching speeds, increased power gain, lower power consumption and improved reliability under shock and vibration conditions.

SSRs can be used to control both AC and DC circuits, making them highly versatile and ideal for controlling large currents or high frequency switching applications. They are also more cost effective than other types of relays as they require fewer parts and can be programmed with various functions. In addition, their solid-state construction makes them more reliable and durable than their electromechanical counterparts. 

Hybrid Relay

Hybrid Relays are electronic switching devices that combine the best of both electromechanical and solid-state technologies. They offer the same high-performance capabilities as SSRs while also providing the same durability and reliability features of traditional relays. Hybrid relays can be used to control both AC and DC circuits, making them suitable for a variety of applications, including HVAC systems, motor control systems, power supplies and more.

In addition to their versatility and dependability, hybrid relays provide several other benefits over traditional relays. For example, they are much more energy efficient than standard electromechanical relays due to their low power consumption, meaning they won’t significantly impact your electricity bill. Furthermore, they require fewer components in comparison to other types of relays, resulting in both reduced costs and improved PCB assembly times.

Thermal Relay

Thermal relays are electromechanical switching devices used to control circuits and protect motors, temperature sensors and other components from overheating. They provide reliable performance, fast switching speeds and extended durability in comparison to standard relays. For example, thermal relays can offer higher precision than their traditional counterparts due to their bimetallic features. This makes them an excellent choice for critical applications such as HVAC systems or motor control systems where accuracy is paramount.

Thermal relays also consume less power than other types of relays, resulting in improved energy efficiency. Furthermore, they require fewer components than standard electromechanical relays which can reduce both costs and assembly times during PCB fabrication. As a result, thermal relays are often the preferred solution for many industrial applications such as power supplies or high-voltage equipment.

PCB Design Requirements for Electromagnetic Relay

PCB design requirements for electromagnetic relays are essential when ensuring reliable performance and extended durability. The main considerations include the substrate material, board thickness, conductor thickness and soldering methods used.

For the substrate material, PCBs made with paper-epoxy or glass-epoxy provide superior reliability and temperature resistance compared to other materials. In terms of board thickness, 1.6mm is recommended for through-hole mounting; however, other dimensions may also be used depending on the size of the relay. The standard conductor thickness should be 35 and 70µm to ensure optimal connectivity between components on the PCB.

Good soldering practices are also needed to ensure a secure connection between the relay and its components. It’s important to avoid excessive heat application that could damage internal mechanisms or connections; instead, manufacturers recommend using low-temperature soldering processes such as wave soldering or reflow ovens. Additionally, it’s important to take steps to avoid contamination from flux residues during soldering by washing the boards after assembly is complete.

How to Solder a Relay on a Circuit Board

Soldering a relay onto a circuit board is an important step in ensuring proper connectivity and performance. The process involves several steps, including flux application, preheating, and soldering. To ensure success, it’s essential to use the correct tools and techniques while following safety protocols.

It’s important to begin by applying flux to the area of the PCB where the relay will be soldered. This helps create a strong bond between the solder and the board’s components. After that, preheating should be done using an appropriate temperature setting for the specific type of board being used. This helps ensure that all components reach their optimal soldering temperature before actual soldering begins.

The next step is to solder the leads of the relay onto their respective pads on the PCB. Soldering can be done either manually or with an automatic soldering machine such as a wave solder machine or reflow oven. It’s important to keep in mind that too much heat may damage internal mechanisms or connections so manual soldering should only be used when absolutely necessary.

Finally, it’s critical to clean any flux residue from the board with an appropriate cleaning solution after soldering is complete. This helps ensure that no contaminants remain which could potentially cause electrical malfunctions or short circuits down the road. With these precautions taken into consideration, engineers can rest assured that their relays will offer reliable performance and extended durability in any industrial setting.

How to Test a Circuit Board Relay

Testing a circuit board relay is an important step in ensuring that it will provide reliable performance and extended durability in any industrial setting. To test a PCB relay, the following steps should be taken: first, connect the multimeter to the relay’s pole and NC contacts. If there is continuity between these two points, then the NO contacts should remain open when unpowered. Next, energize the relay by supplying power to it; if done properly, this should result in a clicking sound as well as engagement of the contacts. Finally, use the multimeter to check for continuity between the pole and NO contacts; if present, then the circuit board relay is functioning correctly.

It’s also important to keep safety protocols in mind while testing a PCB relay. To avoid any potential electrical malfunctions or short circuits, it’s essential to make sure that all components have been properly preheated before soldering begins. In addition, any flux residue must be cleaned from the board with an appropriate cleaning solution after soldering is complete. By following these steps and utilizing proper tools and techniques while testing a circuit board relay, engineers can rest assured that their relays will offer reliable performance for years to come.


PCB relay is a small yet essential safety device for circuit boards. It functions similarly to larger relays but requires special care when mounting onto the circuit board.

To ensure its functionality, it’s important to consider the design requirements and preheating of components before soldering begins. Testing the PCB relay is an essential step to guarantee its reliability in any industrial setting. 


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