PCB components are the parts making up a Printed Circuit Board (PCB). Without these parts, the circuit board might not be fully optimized to attain all the potentials. In this article, we explain what these components have to contribute to the PCB.
What is a PCB?
The full name is Printed Circuit Board. It is a centralized or mono-circuit-board “warehouse” designed to accommodate most of the components used in consumer electronics. PCBs are in high-demand because of the less complicated process they bring when designing modern electronics.
Before the introduction, consumer electronics were mainly designed with different components and wires all scattered inside the product. But with the introduction and the continuous innovations in PCB designs, these parts can now be housed or placed inside one place – the circuit board.
Wikipedia defined PCB as one of the core engineering concepts and processes that allow for the “connection of electronic components to one another in a controlled manner.”
Today, PCBs can be manufactured with different process technologies, such as the Surface Mount Technology (SMT) and the Through Hole Technology (THT). PCBs have also been optimized to work with and accept the integration of different parts, including Integrated Circuits (ICs).
How Do You Identify PCB Components?
If a Printed Circuit Board (PCB) is placed in front of you, how are you going to identify it? What are some of the clues to look out for when checking for the components on the board?
The first thing to have in mind is that identifying the electronic components might be difficult, but luckily, there are some clues to figure it all out.
Thus, below is a table showing some of the designators – the letters or alphabets likely to be printed on the PCB’s surface. Beside each of those designators is the full meaning. So, the next time you see the letters or alphabets marked on the PCB, you know what they mean.
| 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 |
Understand the General Classifications of the Components
One of the best ways of identifying the components mounted or placed on a Printed Circuit Board (PCB) is by understanding the general classifications.
Generally, the components are classified into the mechanical and electrical components. Each of the two works in different ways and understanding these processes will help you figure out the PCB components faster.
How the Electrical Components Work
As the name signifies, these are the components that rely on electrical energy. They are usually placed on the PCB using either of the Surface Mount Technology (SMT) or Through Hole Technology (THT). Both are process technologies used in the design and configuration of Printed Circuit Boards (PCBs).
The electrical components are either soldered directly to the PCB or passed into the circuit board, using wires.
Mechanical Components
These types of PCB components use a “mechanized” process, which has to do with the type of metal used in them. Typically, the mechanical PCB components are made of aluminum, but there are a couple of others made from steel, copper and bronze.
The difference between the mechanical and the electrical components is that unlike the electrical that provide electrical functions, the mechanical components don’t. Instead, the primary function of mechanical components is to provide additional or secondary support to the PCB.
How to Identify the Through Hole Components
The Through Hole Technology (THT) is one of the process technologies used to manufacture Printed Circuit Boards (PCBs).
The components placed on the board via this technology are typically large-sized and have long leads. These leads have openings for holes to be passed through them to enable the placement on the PCB.
So, if you see a PCB component that has is attached to a pad with solder, it is likely to be a THT component.
While it is easy to identify a Through Hole Technology (THT) component, it is not always the case with a Surface Mount Technology (SMT) component.
What are SMT Components?
These are the PCB components “mounted” or “placed atop” the Printed Circuit Board (PCB). Unlike the THT components, they do not use holes for the mounting process.
While these components can be identified because of the shorter leads and absence of holes, there are a couple of other important factors to have in mind.
Below are some of them:
- These components have shorter leads.
- They do not have holes.
- These components rely on soldering of the surfaces to the coppers pads atop the Printed Circuit Board (PCB).
The Broader Division of Electrical PCB Components
Printed Circuit Boards (PCBs), which are classified under the electrical components, are furthered divided into the passive and the active electrical components.
Remember that the electrical PCB components are the circuit board parts, which are acting as secondary materials. Thus, all they do most of the time is to provide electrical connection of the components/parts to the PCB, either in the form of direct soldering or through wired connections.
Now, most of the electronic power configurations of a PCB are delivered via these electrical components. These parts are also further broken down into the passive and the active components, depending on how they transmit the electrical signal.
The Passive Electrical Components
Being “passive” implies that these parts do not directly transfer electrical energy or control the flow or passage of energy through them. Most of the passive electrical components have two (2) leads.
While the easiest way to identify a passive electrical component is via the silk screen printing atop the Printed Circuit Board (PCB), there can be other ways to identify it.
Below are some of the popular linear passive components you can find as a way of identifying the passive electrical parts on a PCB.
1. Capacitors (C)
Capacitors are one of the popular through hole components. They are identified with the Capacitance Value or “C.” So, if you see a component or circuit part marked as “C” or starting the alphabet “C,” there is a chance that it is a capacitor.
Now that we know how to identify a capacitor, let us understand how it works. It is used to store energy in an “electric field” and is usually rated in Farads. The rating can either be written in Millifarads (mF) or in Microfarads (µF).
2. Fuse (F)
Denoted by the alphabet “F,” the Fuse is one of the most outstanding components used in PCB manufacturing. It is also easy-to-identify. You can recognize it because of the typical glass body, through which a fuse wire can be seen. The Fuse also has metal caps, which protect both ends of the fuse.
Note that it is common for the fuse to have the above characteristics if it is a through hole component. However, if you are working with a surface mount fuse, the properties typically include a semi-clear tube axial leaded slightly above the fuse’s surface.
3. Resistors
As the name signifies, the resistors are used for “resistance” – but the question is, what are the resistors resisting?
Resistors are one of the passive electrical PCB components, because they are designed in the form of passive two-terminal components. At the core of the operation is the “resistance,” “restriction” or “prevention” of electric currents to pass through them.
Resistors can also be used to “wedge” or stop the passage of the voltage in each of the connected components.
Since the function of a resistor is “current or voltage restriction,” how then can one tell if it is a resistor or not? We have an idea on how to identify it faster.
First, check if the component has a longish body or structure and if green or blue bands of different colors are imprinted on it. If it does, it means that it is a resistor, because those varying colors highlight the important elements, such as the tolerance and value.
The second way to identify a resistor is by checking the alphabets. Resistors typically start with the alphabet “R.”
The third and most difficult way to identify this component is by considering the body size. Although the ideal size is longish, there are some that could be smaller, especially if these resistors are manufactured with the Surface Mount Technology (SMT). For this type of resistors, the body size is smaller and might not any marking or color to signify them. But if you are able to pick out the alphabet “R,” it will be a lot easier for you.
4. Connectors
These are also one of the passive PCB components. Ideally, connectors are used for “connecting,” “attaching” or “integrating” multiple components. The ideal design is the attachment of the circuit board to a larger component. It can also be used to connect the attach one circuit board to another.
The simplest way to identify a connector in a PCB is to look out for the initial alphabet “K.” It is also possible to make the identification by:
- They can integrate with jumpers. In this instance, the jumper wires will have connector pins at each end of the wires.
- The sizes of the connectors also vary. They can either be slim or large. If they are slim, it means that the connectors are optimized for the flat cables to connect to them. But, if they are larger, it implies that other connectors can connect or be plugged into them.
5. Inductors
Inductors are easily denoted by the alphabet “L.” They are also a two-terminal component, primarily used for storing the electric power or store energy in a magnetic field. The energy storage happens when electric current passes through the inductors.
Note that the inductors are easily identified with the initial alphabet “L,” but there could be some other technicalities making it impossible to identify the component. Due to these, you want to pay more attention to the values or markings imprinted on it.
Inductors can be identified with any of the following markings or values:
- H
- µH
- mH
6. Battery
We will not complete the list of electronic components mounted or “passed through” a circuit board without mentioning the battery.
The commonest way to identify a battery is to look out for the alphabets “BT” on the body. The battery is one of the passive electrical components and is used for storing energy and providing backup power for the Printed Circuit Board (PCB).
Aside from the imprinting of either “BT” or “B” on the body, the battery can also be identified with any of the following:
- Check if it has either a blue or a green shrink-wrapping.
- The shape can be in any of the following forms: coin-shaped, rectangular-shaped or cylindrical-shaped.
The Active PCB Components
Now that we understand some of the small electronic devices or components used in the passive states, let us look at the active ones.
The following are some of the active PCB components, all generally classified under electric current PCB component.
First, let us understand why they are called active components. They are so-called, because these are the components that help facilitate the electric signal passage in the PCB. These components are also available in both the Surface Mount and Through Hole process technologies.
Besides, you can use the active PCB components to enable electrical signal passage in different ways.
With that said, here are some of the popular active components in today’s PCB assembly process:
7. Integrated Circuits
Denoted by either the alphabet “U” or the alphabets “IC,” the Integrated Circuit is one of the easiest PCB components to identify. It has been in use for over 6 decades now, but the modern electronics spot new features, such as microcontrollers and microprocessors.
It is pertinent to mention here that the IC is the “powerhouse” of the Printed Circuit Board (PCB), as the absence can hamper the board’s further configuration. It attained that status because of the following factors:
- Integrated Circuits (ICs) hold the major “building blocks” of a PCB. These blocks include but are not limited to oscillator, amplifier (especially the Operational Amplifier), microprocessor, memory and timer devices.
- Because of the optimization as a microchip, the ICs help to save circuit board space.
Integrated Circuits (ICs) are also known by other names, such as Microchip, Chip and IC.
While you can identify the IC with the alphabets “U” or “IC” imprinted on the silk screen next to the circuit board, it can also be identified some other way.
An alternative identification method is by checking the size of the body and the number of lads. That brings us to the different classifications of the IC. It can be broadly classified into the through-hole and the surface-mount variants.
If you are working with the through-hole IC, the identification metrics are:
- The ICs can come either in form of dual-in-line or single-in-line packages.
- The through-hole chips have several leads on either one side or on both the long sides.
- You can also identify a through-hole IC because of the longish body.
On the other hand, the surface-mount Integrated Circuit (IC) offers more package options than the through-hole chips do. In addition to supporting the dual-inline and the single-inline packages, the surface-mount ICs also support the following:
- Ball Grid Array (BGA)
- Quad chip packaging
We want to mention that before an IC is made, it has to be processed via a wafer or wafers of semiconductor materials. Despite housing multiple components, on a standalone basis, ICs are small electronic devices, which have been “united” or “integrated” in the same footprint to offer multiple functionalities at once, while saving circuit board space.
8. Diodes
Denoted by the alphabet “D,” Diodes are one of the PCB components you can easily identify. Note that these components typically regulate voltages, most times, doing so in a one-way model. It means that the diodes act as a one-way switch for currents or voltages in a Printed Circuit Board (PCB).
How Diodes Work
As a one-way switch for currents or voltages, diodes help to pass “one current at a time.” Thus, it allows currents or voltages from one direction to pass, while preventing the same coming from a different direction from passing.
Aside from the current or the voltage restriction capabilities, the diodes also help to rectify the Alternating Current (AC) into the Direct Current (DC).
Here are some clues on how to identify if the component you find on circuit boards are diodes:
- The through-hole diodes are identified by the transparent glass cylinders, small cylindrical shapes with protruding leads, and black opaque bodies.
- For the surface-mount diodes, they can be identified by the following: polarity marking and denoting with either the alphabets “Z” or “ZD” – for the Zener Diodes.
Classifications of Diodes for Easy Identification
You may have seen diodes, but you didn’t know what they are. Well, there are several types of diodes and understanding these can help you in placing a hand on them when you see one.
First, you want to understand that the diodes are made of semiconductors and typically have the P-N junction. With that being said, here are some of the types of diodes:
- Tunnel diode
- Zener diode
- Rectifier diode
- Silicon-Controlled Rectifier (SCR)
- Photodiode
- Bridge rectifier
- Varicap diode
- Schottky diode
- Constant-current diode
- Shockley diode
- Light-Emitting Diode (LED): The Light-Emitting Diode, also called the LED, is one of the popular diodes. It is generally known to be used to emit light. The process of emitting the light involves the use of the LED to convert the electrical energy into light.
9. Transistors
Transistors are a part of semiconductor devices. It plays an important role in the electrical connections of PCBs, especially those requiring mass production.
Transistors work by amplifying and rectifying electrical signals inside Integrated Circuits (ICs). Transistors also perform several other functions, such as:
- Conducting and insulating electrical signals
- Acting as amplifiers
- Transistors also act as switches for these electrical signals
The following are some ideas on how to identify a transistor inside a Printed Circuit Board (PCB):
- Check for the marking. Transistors typically start with the alphabet “Q.”
- Transistors can operate at lower voltages, even when they don’t use a filament current.
- These components are smaller in size
- There are several variants of transistors, ranging from Field Effect Transistors (FETs), PNP Darlington Transistors, Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs), PNP Bipolar Junction Transistors (BJTs) and N-Channel MOSFETs.
What are the 3 Types of PCB?
There are several types of Printed Circuit Boards (PCBs), but three (3) of them are outstanding. Here are the 3 and how they work:
Single-Sided PCB
Also called the single sided boards, these are the Printed Circuit Boards (PCBs) that don’t use multiple conductive layers. Instead, it uses just one conductive copper layer, which is placed above the substrate.
The general specifications include:
- The placement of one layer of the base substrate and one single, conductive layer, which make up the fiberglass and copper, respectively.
- The single-sided boards also have the electrical components placed on one side and the conductive circuit placed on the other side.
Double-Sided Boards
The double-sided PCBs are the opposite of the single sided boards in the sense that they use one layer or conductive material (preferably copper) on both the top and bottom sides of the circuit board (the two sides of the substrate).
The double-sided PCBs can be connected on either side using either the Through-Hole Technology (THT) or Surface Mount Technology (SMT). If the through-hole is to be used, the through-hole components or the lead components must be installed into the pre-drilled holes on the Printed Circuit Board, before using a soldering iron to apply a solder mask to the pads on both sides of the circuit board.
If you are to use the surface-mount process, the process simply involves mounting the electrical connections on the circuit board’s surface.
Multi-Layer Boards
If you are looking for a PCB manufacturing process that uses several copper layers, it has to be the multi-layer PCB.
As the name suggests, it supports the use of multiple conductive layers, usually exceeding two (2).
The minimum number of supported copper layers is 3 and it can be as high as 40. The configuration process involves interconnecting the conductive layers with copper plated holes.
How are Components Connected in a PCB?
Proto Electronics highlighted some of the relevance of electronic component placement on a PCB to include:
- Helping the electrical engineers to make an accurate positioning of the electronic components mounted or drilled into the circuit board. That way, the circuit’s operation will be improved, while the signal paths will be clearer.
- Aiding the separation of the analog components from the digital components or parts.
Then, when it comes to how electronic or electrical components are connected in the Printed Circuit Board (PCB); it all boils down to two (2) process technologies.
The first process technology is the Surface Mount Technology (SMT), which involves mounting or placing the PCB components atop the circuit board.
The second is the Through Hole Technology (THT), which allows for the components with leads to be “drilled” or “passed through” the pre-drilled holes before the components are added to the circuit board.
Conclusion
We hope that you now understand most of the technicalities involved in mounting or adding PCB components to circuit boards. You also understood the different processes used to do that, how they differ and the best ways to identify some of the popular PCB components.
Finally, the Surface Mount Technology (SMT) and the Through Hole Technology (THT) may be the major processes to connecting components to Printed Circuit Boards (PCBs). However, you also want to double-check the component’s orientation/placement, positioning the components before wiring and soldering the parts into place.
