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How to Identify Common PCB Components
When you switch on a computer, radio, or any other electronic device, you will find a printed circuit board (PCB) with many small components. All of these components have a specific function, and it is important to know how to identify them before learning electronics.
This FS Technology tutorial lists the most common PCB components. It talks about their function, look, and how to recognize them. After reading this, you can recognize the major components on a PCB with more confidence.
Common electronic components in PCBA board
Without any respect of any type of circuit board, electronic components can only be placed on either the top layer or the bottom layer of PCBA. These parts that make up the PCBA board are considered important, and before starting PCB component identification, we have to know about the components. Electronic Components are meant to be interlinked through tracks on PCBs’ conductive layer to develop electronic circuit which performs desired function for example oscillator, amplifier, transmitter, receiver, and wireless.
Following are the main electronic components used more frequently from the simplest single layer PCB to complex multilayer PCB.
Resistor
One of the most common components, resistors slow down the flow of electric current. Think of them like a narrow section of pipe slowing the flow of water. They are used to reduce current, divide voltages, and protect sensitive components like LEDs from burning out.
How to Identify:
- Through-Hole (THT) Resistors: These are the simplest for a beginner. They are small, cylindrical devices with wire leads coming out of each end. They have colored bands on them. This color code is a digit. You can use online calculators or charts to decipher it for you (e.g., Brown-Black-Red = 1,000 Ohms or 1kΩ).
- Surface-Mount (SMD) Resistors: Little, flat, rectangular ceramic chips. They are typically black with a white digit imprinted on the top. The digit is a code. For example, “103” is 10 followed by 3 zeros, and that is 10,000 Ohms or 10kΩ.
The picture below shows Resistor symbols:
Capacitor
When mentioning the application of capacitors, the first thing people think of is charging and discharging. The capacitor is like a small rechargeable battery that is able to be charged and discharged quickly. It is only its most basic function, yet based on the basic function, different circuit phenomena can be realized, for instance: in a motor, it can produce intense vibration; in a camera, a capacitor can be discharged instantly with energy. A few of the most commonly used capacitors in our lives include phase-shift capacitors, electric heating capacitors, coupling capacitors, etc. They are used for smoothing power supplies, filtering a signal, and timing circuits.
How to Identify: Capacitors come in a myriad of shapes and sizes that can be confusing. We’ll talk about the two most common ones:
- Electrolytic Capacitors: Larger, barrel-like components, usually aluminum-colored with a black or grey sleeve. They have a clear polarity: a stripe on the sleeve marks the negative (-) lead. They are always marked with their value (e.g., 100µF) and voltage rating (e.g., 16V).
- Ceramic Capacitors: Much smaller. Through-hole versions look like tiny, flat disks. SMD versions are small, yellow or tan, rectangular chips. They are non-polarized and typically have a numeric code marking (e.g., “104” = 100,000 pF or 0.1µF).
The symbol for a capacitor is provided by the following figure:
Transistor
Transistors are indispensable PCB components in the electronics manufacturing industry, and their numbers are very large. We can simply divide it into triode, diode, thyristor, etc. It has a variety of functions such as detection, rectification, amplification, switching, voltage regulation, signal modulation and so on.
How to Identify: Through-hole transistors are typically in a small black plastic package with three metal leads. They will also have a part number printed on them (e.g., BC547, 2N3904) which you can look up online to know its details. SMD transistors are extremely small, black, flat chips with three leads.
The transistor symbol is illustrated in the figure below:
Inductors
Inductors store energy in a magnetic field when current is sent through them. They resist changes in current and see significant use in power supplies and radio circuits to reject high-frequency signals.
How to Identify: They might look like resistors but tend to be one color like green, blue, or beige with no bands of color. Sometimes you can see the coiled wire inside them. SMD types are tiny, black, rectangular chips. They can have a plain number stamp.
Integrated Circuits (ICs) / Microchips
An IC is not a single device but a vast collection of tiny transistors, resistors, and other components built onto a single piece of silicon. They perform complex functions as a complete circuit (e.g., a microcontroller, amplifier, or logic chip).
How to Identify: They are the “black rectangles” with a lot of legs (pins). They cannot be overlooked. They always have a part number engraved on top (e.g., “ATMega328,” “LM358,” “74HC00”). The key to recognizing an IC is to look up this number on the internet to find its datasheet.
How to Classify PCB Components
Method 1: Active vs. Passive Components
In order to facilitate management, we generally further classify electronic components into two types based on various factors like power gain, functions, nature of the source, and controlling the flow of current.
Active Components
These components provide power to the circuit instead of utilizing it that’s why they are called active components and the energy produced is in the form of voltage and current. Active components are also called energy donors. They utilize energy from an external source to perform their function,
Examples of active components include transistors, Diodes, and Integrated circuits (IC).
Passive Components
Passive electronic components utilize the energy that active components provide to the circuit. These components just store energy and are unable to provide energy like active components. Passive Components are also called Energy acceptors.
Examples include resistors, Capacitor, and Inductor.
| Feature | Active Components | Passive Components |
|---|---|---|
| Power | Can control and amplify power. They often require a power source to function. | Cannot control or amplify power. They can only absorb or store it. |
| Function | Act as switches, amplifiers, oscillators. | Resist, store, or filter energy. |
| Examples | Transistors, ICs, Diodes, LEDs | Resistors, Capacitors, Inductors |
Method 2: Through-Hole (THT) vs. Surface-Mount (SMD)
If you carefully observe the PCBA board in your hand, you can find that the electronic components on the same circuit board use different packaging processes. In simple terms, one is directly inserted into the hole in the PCB board, and the other is soldered to the PCB board. Therefore, PCB components can be divided into two categories according to their packaging methods.
Through-Hole Component
Through-hole components refer to a type of component that is soldered on the surface of a PCBA through plug-in and wave soldering, and usually we also call it a DIP component. Almost every component in electronics has a through-hole package. These packages have long enough pins to get passed from the top layer to the bottom and get soldered on the bottom layer with PCB. They are also called multilayer packages or DIP assembly. For such a package, routing can be done on either the top layer or bottom layer, or other multi-layers of PCB.
Surface Mount Device (SMD)
As the name suggests these are SMD components mounted on only one side of the PCB, due to this reason their routing is also done on that same side or can be shifted to another layer using vias in the PCB. Almost every electronic component also comes in this package.
Electronic component either through-hole or SMD is used according to need. Their working principle and function resemble but differ in size and soldering methodology.
| Feature | Through-Hole (THT) | Surface-Mount (SMD) |
|---|---|---|
| Mounting | Leads are inserted into holes drilled in the PCB and soldered on the other side. | Soldered directly onto pads on the surface of the PCB. |
| Board Space | Larger, uses more space on both sides of the board. | Much smaller, allows for incredibly dense and compact modern devices. |
| Assembly | Easier for hand-soldering and prototyping. | Requires precise automated machines for assembly, but is faster for mass production. |
Practical PCB Component Identification Tips
- Get Your Hands On Old Electronics: The best way to learn is to get a broken radio, DVD player, or old computer motherboard (just be sure it’s not plugged in!). With a screwdriver, break it down and try to identify each component on the board.
- Use the Right Tools:
- A magnifying glass or jeweler’s loupe is necessary for reading the tiny codes on SMD components.
- Your friend is a multimeter. You can use it to measure resistor values, check if a diode works, and check for continuity (no gaps in the connections).
- Decode Part Numbers: For any transistor or IC, type the number on the part into a search engine and the term “datasheet” (e.g., “NE555 datasheet”). This document tells you everything about the part.
- Trace the Traces: Look at the thin copper lines (traces) between components. This may enable you to notice that components are grouped into functional blocks (e.g., power section, audio output section).
Conclusion
Proficiency in the art of PCB component identification will take your repair, troubleshooting, and even design skills to electronic components to greater heights. Once you’ve mastered the art of component identification and are set to bring your circuit concepts to life, you would require a trustable manufacturing partner. FS Technology offers an entire range of PCB fabrication and assembly services, including component procurement, from simple single-board prototypes to complex multi-layered projects. Contact us today for a quick quote and let us help you create your electronic innovations.
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