PCB Blog - Know about printed wiring assembly

Printed wiring assembly also known as printed circuit board assembly(PCBA), is an electronic or electromechanical component that enables a PCB to perform its functions. These components can be power devices, signal generators or receivers, signal transmitters, and more. Some are prominent, while others are small and barely visible. Though each part has its function, they must work together through trace interconnections. A typical PCB may contain anywhere from several to hundreds, or even thousands, of components, depending on its size and intended use. They also come in different shapes, grades, etc.

Printed wiring assembly typically control the flow of current. Each component has a specific purpose, with some components (such as ICs) handling signals, while others regulate voltage. Some can protect circuits from electrical faults, ensuring reliability and extending the PCB's lifespan. Consider them as parts of a broader system, working together to make it function as intended.

Manufacturers use solder to install PCB components. To electrically connect them, they use pathways called traces and electroplated holes called vias to connect layers. These components are also attached to the circuit board using through-hole or surface-mount technology.

Through-Hole: These holes go through the circuit board. They come with long leads for easy soldering on the other side, making them suitable for manual assembly. However, they require more space.

Surface Mount Technology (SMT): Surface-mount components have shorter or no leads. They attach to the surface using solder pads. These parts are more suitable for automated assembly and take up less space. The downside is that they are less secure and mostly smaller in size.

printed wiring assembly

How to Identify PCB Components?

You can use various methods to identify PCB components: through visual inspection, using markings placed by the manufacturer on the circuit board, and referring to specific PCB datasheets.

Visual Matching: PCB components can be visually identified based on their shapes and other characteristics. Each part has different physical features, as seen in the image above. For example, electrolytic capacitors are cylindrical, while different ICs are blocks with pins on both sides.

Abbreviations: These are reference indicators or codes printed on the silk screen. They can identify each component, allowing anyone working on the PCB to make the correct identification. Examples of codes are:

R – Resistor

C – Capacitor

U – Integrated Circuit

T – Transformer

J – Connector

L – Inductor

PCB Datasheets: Manufacturers often provide detailed specifications in product datasheets. For PCBs, this information can include circuit diagrams, layouts, etc. Referencing it can help you identify various electronic and electromechanical components, their interconnections, rated values, etc.

Types of printed wiring assembly

PCB components can be passive or active. "Passive" refers to those devices that do not rely on power to operate. Active ones do. Below is a list of important examples in each category.

Passive Components:

Capacitors – Store charge, filter signals, and stabilize voltage.

Inductors – Used with various components to store energy in a magnetic field.

Resistors – Limit the flow of current.

Varistors – Provide overvoltage protection.

Thermistors – Measure temperature by utilizing resistance change.

Fuses – Blow when the current exceeds a preset value to provide electrical protection.

Transformers – Transfer energy between circuits using electromagnetic means.

Traces – Serve as current paths for electrical interconnections.

Active Components:

Light-Emitting Diodes (LEDs) – Control the direction of current flow.

Transistors – Switch and amplify signals.

Integrated Circuits (ICs) – Microcomponents containing processing and control elements for electrical signals.

Switches – Control various circuits by connecting and disconnecting them.

Voltage Regulators – Maintain a constant voltage to prevent fluctuations.

Common printed wiring assembly Issues

PCB components should fit their function and position. However, sometimes this does not happen. The reasons may vary depending on the type of fault. Common causes of problems include incompatibility, component damage, and assembly issues.

Incompatibility: Components may not fit your PCB due to their height or other physical characteristics and rated power. It may also be because it uses different communication protocols than the ones you designed the circuit board for.

Damage: PCB components may suffer physical damage. This mainly happens when you transport or store them without proper care. For example, parts damaged by dust or heat may not function in the circuit, leading to partial or complete PCB failure.

Assembly Issues: Assembly issues include soldering defects and incorrect component placement. To avoid all of these, follow proper design and assembly rules. Testing the PCB after component installation also helps identify mistakes and correct them.

Electronics is a rapidly evolving field. Nowadays, PCBs are getting smaller in size. This requires their components to shrink as well. It also demands them to become more efficient in power usage and heat dissipation.

With these developments, PCB components will become smaller, multicore, and more powerful. Their cost will also decrease with the use of new manufacturing technologies and materials, making them available for many applications.

Given the advancements in technology, these components may also become high-speed and capable of supporting ultra-high data speeds, such as 5G technology. Through all these changes, future components will enhance electronic devices and systems.

Conclusion

Printed wiring assembly is a crucial component to ensure its proper functioning. These components can be passive or active, providing various functions to operate the board in its final use device or system. As we have seen, selecting them correctly is essential; otherwise, your PCB may encounter performance issues.