An Engineer’s Perspective: How To Read A PCB Board?

PCB Board with Components

PCBs are generally considered the backbone of electronic devices. Almost all electronic devices have PCBs as major parts like smartphones, laptops, gaming consoles, washing machines, and other everyday electronic appliances. One of the key attributes of an electronic engineer is to understand the sophisticated and complex layouts of PCB, which can only be done with fundamental knowledge of basic electronics components, circuit theory, and circuit troubleshooting and debugging. Knowing basic electronic components and their configuration techniques in circuits helps in circuit analysis and effective troubleshooting. This guide covers everything from what PCB is, how to know the components of PCB, and how to read a PCB board.

Printed Circuit Board (PCB):

PCB is a board with conductive copper traces and various electronic components. These electronic components are interconnected with the help of copper traces to create a complete closed-loop circuit to flow current through the circuit, that’s why PCBs are considered the backbone of electronic devices. It is important to know what types of different electronic components are used in PCBs and what they are meant to do. Also, it is important to know which composition of electronic components must be used to achieve the required electrical target. This is very important to know how to read a PCB board.

Generally, electronic components are divided into two types based on their functionality.

  1. Passive Components
  2. Active Components

PCB Board Components

1. Passive Components:

As the name suggests, passive components are not meant to regulate or enhance the electrical signal transmitted to such components, these components only save energy or react. Following is the list of passive components with a brief introduction.

  • Resistor: This component is used to resist electric current, and its value is measured in ohms. Resistors are one of the most commonly used electronic components. There is a color code on its body from which one can calculate its value. Resistors have versatile kinds like variable resistors, thermistors, and potentiometers, with different wattage ratings like quarter watt, half watt, and one watt, which are used according to requirements. Generally, “R” is used as a designator on the PCB’s silkscreen, symbolizing the resistor.
  • Capacitors: A passive component that is used to save energy in an electric field is a capacitor, commonly found on PCB with designator “C”. Capacitors are measured in Farads, such as Millifarads, Microfarad, Nano-farads, Picofarad, and vice versa. Different types of capacitors are used for different purposes in PCB designs like electrolytic capacitors are used in designs where very high capacitance is required, to block DC electric signal paper capacitors are used which permits AC electric signal, and vice versa.
  • Inductors: This passive component stores energy in the form of a magnetic field. Inductors, in contrary to capacitors, store energy til the close-loop electronic circuit is intact. In PCBs, “L” is used as a designator for inductors and is rated in Henry.

2. Active Components:

These components can regulate or enhance electrical signals, unlike passive components as discussed earlier. Some of the major active components commonly used in PCBs are jotted down.

  • Diodes: A semiconductor device primarily used to control voltages in one direction, restricting electrical signal flow in the incorrect direction where it causes damage to the circuit, so acts as protection diodes. Diodes are usually symbolized with the letter “D” in PCBs. Its applications include signal processing, power control, and light emission.
  • Transistors: In modern electronics, transistors are considered as most significant component in design. It can act as an electronic switch and as an amplifier. Transistors are three-legged electronic components namely collector, base, and emitter. There are billions of transistors in a single IC. PCB designers give random designators to transistors according to their will, but generally “Q” or “VT” is used in PCB. Different kinds are used in PCB designs like MOSFET, FETs, JFETs, and bipolar.

PCB with Electronic Components

Also read: What are the Steps of Making a PCB Circuit Board? Ultimate Guide

How to Read a PCB?

At first glance, a PCB seems like a very complex board with a lot of electronic components connected with a maze of lines. An engineer needs to read the PCB efficiently and effectively to reverse it or debug it. The following steps must be followed to know how to read PCB board correctly.

  • Identify Components: Reading a PCB starts with the visual inspection of the PCB to observe resistors, capacitors, ICs, transistors, and other electronic components. Different designators are used for different components. Generally, these designators are fixed for specific components as discussed earlier, like “R” is for resistors, “L” is for inductors, and vice versa.
  • Decipher Marking on components: This involves decoding alphanumeric coding on electronic components or resistor color coding, to know their ratings. Mostly capacitors have alphanumeric codes from which one can find their rating in capacitance, and resistors have color codes representing their resistance in ohm.
  • Understand Component Placement: This step is also very important to read the PCB board. This step involves understanding why and how different components are placed in such a pattern. Usually, those components that emit heat energy in the surrounding environment are meant to be placed away from heat-sensitive components or circuits. In this way, this step helps to understand the PCB design limitations to read the PCB more efficiently.
  • Understand PCB Routing: Identifies conductive copper pathways that connect components in the PCB. Through these traces different components communicate and perform required functions like an amplification of voltage signal, providing power and ground signals to different ICs, and vice versa. This step also helps to understand and analyze the signal flow in the circuit. By paying attention to PCB at the signal propagation level, circuit troubleshooting and its optimization become easier.
  • Defect and Error Inspection: It is important to perform PCB inspection regarding damaged traces, lifted pads, and misalignment of components that lead to PCB malfunctioning.
  • Documenting Findings and observations: It is good practice to create a document of findings and observations while reading the PCB. This document may include component ratings, and designators, which also helps in creating BOM. This document will be helpful in future troubleshooting and debugging, modifications, and revising the PCB version.


Reading a PCB is an art and for electronic design engineers mastering this fundamental skill is very important which enhances related skills like troubleshooting, testing, and enhancing the design of PCB. How to how to read a PCB? Simply by following above mentioned steps electronics engineers can improve PCB reading proficiency and literacy to tackle modern challenges and increase engineer’s precision, accuracy, and confidence with complex PCBs.

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