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What Is a Printed Circuit Board?
Before diving into the common circuit board components, it’s important to understand what a printed circuit board (PCB) is and how it functions. A PCB is a glass-reinforced plastic board that contains and connects the electrical components of the board. Copper traces guide the electrical charge to the right destination. Circuit boards are essential to ensure modern electronics, such as mobile phones and computers, function as intended. Printed circuit boards can be single-sided, double-sided, or multi-layer.
Before the advent of circuit boards, the wires and other components of electronic devices were loosely scattered throughout the device’s housing. With PCBs, these components can be organized and put on a single board, simplifying the design of consumer electronics.
Common PCB Components
The components on a circuit board vary depending on the device or electronic item a PCB is designed for because different PCB components are required for different circuits. Each circuit board component is vital to the device’s functionality, and if one component fails, it will result in the failure of the entire PCB. Here are the common components found in PCBs.
Resistors
Resistors are vital PCB components that can be made of various materials and color-coded according to their resistance value. PCB resistors use the electric current received to produce a voltage and dissipate the electricity as heat.
Capacitors
Capacitors are the second most common PCB components, holding an electrical charge in the circuit board and releasing it when the circuit needs power elsewhere. Usually, capacitors work by collecting opposite charges from two conductive PCB layers that are separated by insulating material.
Transistors
Transistors amplify the charge on a circuit board to switch or control the PCB’s electrical signals. The most common transistor is the bipolar transistor, consisting of three pins: the base, the emitter, and the collector.
Inductors
Similar to capacitors, inductors store electric power or energy as a magnetic field when electric current flows through them. Inductors are often used to change current or block signals within the board from other electronic devices.
Transformers
Transformers are circuit board components that increase or decrease voltage to transfer electrical energy from one circuit to another.
Diodes
Diodes installed on circuit boards allow electrical current to pass in one direction and block it from passing in the opposite direction. Therefore, diodes can prevent currents from flowing in the wrong direction, thus preventing damage to the circuit board.
LED
Light-emitting diodes (LEDs) are the most common diodes. The LED will light up when current flows through it and will only allow current to flow unidirectionally.
Sensors
Sensors convert physical elements—like sound, motion, air quality, or light—into electrical energy. Sensors can detect environmental changes to create an electrical signal that corresponds to the detected change. The signal is sent to other circuit board components to take necessary action and ensure the proper function of the device.
Battery
As a passive electrical component on a circuit board, the battery provides power to the PCB. It stores energy to provide power backup to the board.
Potentiometer
Potentiometers measure electrical voltage or the board’s voltage potential. They are typically marked in ohms using three digits. The first two numbers represent the significant figures, and the last number indicates the power of 10 multipliers.
Switches
Switches are circuit board components that work similarly to a light switch, allowing or blocking electrical current. When a switch is open, it allows the current to pass through, and when it’s closed, it will stop the current from passing.
How Are PCB Components Identified?
With a PCB often featuring multiple components, you may wonder how to identify them. A closer look at the circuit board’s designators will reveal clues to figuring out the different electronic components of circuit boards. Here is a table defining common PCB component designators, which are letters usually printed on the circuit board’s surface.
| Designators | Full Name |
| ATT | Attenuator |
| BT | Battery |
| CB | Circuit Breaker |
| BR | Bridge Rectifier |
| D | Diode |
| C | Capacitor |
| G | Oscillator |
| DC | Directional Coupler |
| F | Fuse |
| IC | Integrated Circuit |
| J | Jack or Jumper |
| L | Inductor |
| K | Contractor/Relay |
| P | Plug |
| LED | Light Emitting Diode |
| PS | Power Supply |
| LS | Loudspeaker |
| MOV | Metal Oxide Varistor |
| SW | Switch |
| Q | Transistor |
| TB | Terminal Block |
| POT | Potentiometer |
| TP | Test Point |
| R | Resistor |
| TR | Transistor |
| T | Transformer |
| X | Transducer |
| TC | Thermocouple |
| U | Integrated Circuit |
| Z/ZD | Zener Diode |
| VR | Variable Resistor |
| XTAL | Crystal |
How Are Components Connected in a PCB?
There are various ways to connect circuit board components within PCBs. The two most commonly used methods are Through Hole Technology (THT) and Surface Mount Technology (SMT). With either method, PCB assembly requires the engineer to follow the schematic pattern and numbers on the silkscreen to correctly install PCB components in the right locations.
Surface Mount Technology (SMT) involves mounting the PCB components on top of the circuit board. With SMT, parts are soldered on the board’s surface via the copper pads atop the PCB.
Through Hole Technology (THT) requires circuit board components to have long leads to pass through the pre-drilled holes on the PCB and attach to the board with solder. Looking for holes in a PCB is a simple way to identify THT components.
Contact PGF Technology Group
PCBs are essential to modern electronic technology and rely on various circuit board components. Understanding the different PCB components can help you make the right decision with your PCB assembly needs. In addition to the components, the mounting technology can ensure your circuit boards run optimally and perform the necessary functionality for your device or equipment. At PGF Technology Group, we specialize in PCB manufacturing and assembly. We conduct comprehensive testing on all PCB assemblies to ensure every product shipped is of premium quality to fit a wide range of industry needs. Contact us to learn more about our PCB assembly services, or request a quote for your printed circuit board solution.
