Essential Components Found on Every PCBA

Printed Circuit Board Assembly (PCBA) is the heart of modern electronic devices, facilitating the seamless function of various systems by connecting multiple electronic components on a board. While the design and complexity of PCBAs vary based on the application ranging from consumer electronics to industrial systems. But some common core components are consistently found across virtually every assembly. With the evolution of components used in circuit boards over several years, it is essential for everyone involved in PCB design, manufacturing and the assembly process to understand the characteristics of the components better. In this article, let us understand a few of commonly used components found on a circuit board assembly and their applications, functions and the importance of using those in electronic devices.

The Evolution of Electronics in Past Few Decades:

The history of components used in the circuit goes back to the late 1900s where PCBs were made from materials like Bakelite, Masonite, cardboard sheets and thin wooden planks in olden days. The invention of passive components like resistor, capacitor and inductor were done during the 19th century. Later on in the 20th century vacuum tubes were introduced and after some time transistors replaced these bulky vacuum tubes.

Then integrated circuit technology revolutionized the world and in the 1980s surface mount technology (SMT) was introduced which further reduced the circuit board components size and made assembly process easier. Over the several years, evolution of components has enabled the PCB to bring down the size to miniature level without losing the electrical performance and has helped to develop more efficient and powerful devices that are used worldwide. To know more, see our comprehensive guide on PCB assembly process.

Identification of Various Components and their Values:

Visual identification: It is the first step in recognizing circuit board components. By examining the size, shape, color, and markings on the components, you can often determine what they are and what they do. Key points to consider include:

Shapes and Sizes: Components like resistors, capacitors, and inductors have distinctive shapes. For example, resistors are cylindrical with color bands, while electrolytic capacitors are typically cylindrical with one flat end.

Component Labels: Most circuit boards have printed labels or symbols next to components, such as "R" for resistors, "C" for capacitors, "L" for inductors, "Q" for transistors, and "U" for integrated circuits.

Color Codes: Resistors often use color bands to indicate their resistance values. Capacitors may have printed numbers indicating their capacitance.

List of Essential Components Found on Every PCBA:

Building a circuit without the complete understanding of the theory behind it seems unthinkable. But in reality, it is possible to build projects with little understanding of the theory behind it. While knowledge of electronics theory will prove itself to be more than helpful, it is not an essential part of building simple yet useful projects. A good way to get started is to first familiarize with the components used on a circuit board and their functions. Here is the list of 10 very common components found on every PCB board assembly nowadays:

1. Resistors

Resistors are one of the most fundamental components found in nearly every PCBA. Their primary function is to limit the flow of electrical current and reduce voltage levels within the circuit. Resistors help protect sensitive components from damage due to excessive current, maintaining stable circuit operation. Resistors come in various values, measured in ohms, and are critical in controlling power distribution throughout the circuit.

2. Capacitors

Capacitors store and release electrical energy as needed, playing a crucial role in filtering signals, stabilizing voltage, and managing power supply fluctuations. They can smooth out voltage spikes or dips, which are common in high-frequency applications, protecting the overall system from damage. Capacitors are also essential in timing circuits, signal coupling, and noise suppression, making them a key component in both analog and digital circuits.

3. Inductors

Inductors are components that store electrical energy in a magnetic field when current flows through them. They are commonly used in power supplies, filtering circuits, and signal processing. Inductors help maintain stable current flow and filter out high-frequency noise, ensuring that only clean signals pass through the circuit. In power applications, inductors can be combined with capacitors to create tuned circuits that allow specific frequencies to pass while blocking others.

4. Diodes

Diodes allow current to flow in only one direction, acting as a gatekeeper in electronic circuits. One of the most common types of diodes is the rectifier diode, which converts alternating current (AC) into direct current (DC). Light Emitting Diodes (LEDs) are another form of diode found on many PCBAs, commonly used as indicators or lighting elements. Diodes are also used for voltage regulation and signal demodulation, protecting the circuit from reverse current that could cause damage.

5. Transistors

Transistors are key components that act as amplifiers and switches in modern electronics. A transistor can control high current or high voltage with a low-power signal, making it essential for managing the flow of electricity in circuits. They are widely used in digital logic circuits, signal modulation, and switching applications. When we are discussing Bipolar Transistors these are of two types: NPN and PNP, depending on how the current flows through the component. Advanced transistors like MOSFET, MESET, JFET and FINFET are introduced later in electronics as the device power/speed increases.

6. Thyristors

Thyristors are semiconductor devices that act as switches or rectifiers. Like transistors, thyristors can control high currents with small signals, but they are typically used in high-power applications. They are commonly employed in circuits that require the control of large voltages and currents, such as motor control systems, light dimmers, and power conversion systems. Thyristors have an "on" state, where they allow current to flow, and an "off" state, where current is blocked, making them ideal for controlling power in industrial and consumer electronics. Some of the basic types are SCR (silicon controlled rectifier) and TRIAC (Triode for alternating current).

7. Integrated Circuits (ICs)

Integrated Circuits (ICs) are complex assemblies of multiple electronic components like transistors, diodes, and resistors within a single chip. ICs perform a wide range of functions, from processing signals and managing power distribution to enabling complex logic operations in microprocessors and memory modules. Modern PCBAs often have multiple ICs to handle the diverse tasks required in devices like smartphones, computers, and industrial machinery. For example: OPAMPs, Logic ICs, Power Delivery ICs and RF integrated circuits.

8. Connectors

Connectors serve as the interface between the PCBA and external components, such as sensors, displays, or power sources. Connectors come in various shapes and sizes, including headers, sockets, and pin arrays, depending on the type of connection required. They ensure that data, power, and signals are transmitted reliably between the board and other elements of the electronic system. In complex assemblies, connectors facilitate modular designs where different PCBAs can be easily replaced or upgraded. Some of the basic connector types are shown below in the figure:

9. Crystals and Oscillators

Crystals and oscillators are timing devices used to generate precise frequency signals. They are essential for synchronizing the operation of microprocessors, communication circuits, and other timing-sensitive components. The frequency generated by these components is critical for maintaining accurate data transmission rates in systems like computer networks, mobile devices, and embedded systems.

10. Switches and Relays

Switches and relays are used to control the flow of current within the circuit. Switches are manual or automated components that either allow or stop current flow when actuated. Relays, on the other hand, are electrically operated switches that allow a low-power signal to control a higher-power circuit, often used in automation and control systems. Some of the basic switches are relay types are shown below in the figure:

11. Fuses and Circuit Protection Components

Fuses and other protection devices like TVS diodes and PTC thermistors are critical in safeguarding the PCBA from overcurrent, voltage surges, or thermal overload. Fuses break the circuit when the current exceeds a predefined level, protecting sensitive components from damage. Circuit protection devices ensure the long-term reliability of the PCBA by preventing catastrophic failures in high-power or sensitive systems.

12. Heat Sinks and Thermal Management Components

With the growing demand for more power in compact spaces, heat sinks and other thermal management components have become vital in ensuring the safe and efficient operation of the PCBA. Heat sinks dissipate heat generated by components like power transistors, ICs, and regulators, preventing overheating and maintaining optimal performance. Proper thermal management is crucial for the longevity and stability of the entire assembly, especially in high-performance or industrial-grade systems.

Where to Get Every Single Detail About a Component?

When visual identification and multimeter testing are not enough, reference materials such as datasheets, circuit diagrams, and online databases can be invaluable. These resources provide detailed information on component specifications, pin configurations, and how they are used in circuits:

• Datasheets: Available from manufacturers, datasheets provide detailed technical information about specific components, including electrical characteristics, pin layouts, and recommended usage.

• Circuit Diagrams: Schematics and diagrams help you understand how components are connected within a circuit, aiding in identification and troubleshooting.

• Online Resources: Websites and databases dedicated to electronics offer searchable catalogs of components, cross-reference tools, and forums for discussing identification challenges.

Conclusion

Understanding the essential components of a PCBA is key to grasping how modern electronics function. From resistors that regulate current flow to ICs that perform complex logic operations, each component plays a specific role in creating a functional, efficient, and reliable circuit. Whether you're designing a simple consumer gadget or a high-performance aerospace system, mastering the selection and placement of these components is essential for achieving the desired performance and reliability of your PCBA.

By recognizing the function of each element and incorporating the best design practices, engineers can optimize the layout, functionality, and durability of their PCBAs, ensuring they meet the demands of the application at hand.