How to Reverse Engineer a PCB?

Table of Contents

pcb sample

Are you new to reverse engineering PCBs and wondering how exactly it is done? Do you want to learn some new tricks in your design process and discover more ways of optimizing your work? This detailed article explains how to reverse engineer a PCB that can be used by any electronics engineer to understand the logic of a circuit. Read on to find out more…

What is PCB Reverse Engineering?

When it comes to PCBs, reverse engineering means taking a finished PCB and breaking it down into its components so that a schematic diagram can be created, and the function of each component can be understood. When a PCB is first built, a schematic is also created at the same time. The schematic is a visual diagram that shows the layout of components, and the electrical connections between them.

Which Tools Can You Use for PCB Reverse Engineering?

In last post, we talk about pcb reverse engineering tools including hardware and software. Below are the common tools that electronic engineers usually use.

Automatic Test Equipment (ATE)

Automatic test equipment (ATE) can be used to identify the components on a PCB by giving the readings for their voltages. The voltages present on a component indicate the type of component it is. ATEs are relatively expensive pieces of equipment, but they can be an extremely useful tool for reverse engineering PCBs. Many companies produce ATEs.

Digital Multimeter

The digital multimeter can be used to identify the components on a PCB by reading their voltages and resistors. Then you can find out the identification of those components according to the readings.

Digital multimeter

Notes:

  • The identification of electrolytic capacitors, transistors, and diodes is almost impossible with a multimeter.
  • Only very basic component identification such as resistors, capacitors, inductors, and semiconductors can be done with a multimeter.

Magnifying glass

The magnifying glass can be used to identify components with printed symbols on them. These symbols are usually coded, but they usually correspond to the component’s function. The symbols can usually be found in a component’s datasheet, and they are usually denoted with a “dot” or “bar” symbol. The component can then be identified according to the printed symbol.

5 Steps to reverse engineering a pcb

Different from PCB design, PCB reverse engineering is a reverse research method. Through a series of reverse technology research such as professional PCB reverse schematic software, a full set of production materials such as product PCB files, BOM list, and SCH schematic files are derived, which is then used in the process of product upgrading and secondary development.

There is no fixed procedure for reverse engineering a pcb, but here are some general steps you can take:

Step 1 - Decipher Electronic Schematic Diagrams

You can get the schematics of the pcb from our tutorial or an online pcb database.

PCB schematic of polarity switching circuit

Tips:

– 1. Remove the components from the board.
– 2. Find the component markings and take down their values.
– 3. Mark the important connections on the board using a pencil or a pen.
– 4. Create the schematic diagram based on the markings and connections.

Step 2 - Generating PCB Design Files

Look for patterns in the schematic and convert the symbols into PCB design files using a standalone converter like pad circuit generator or a software tool like FreePCB.

Step 3 - create circuit boards

Use PCB design files to create boards using PCB design tools like Altium Designer or ISE circuit designer. In another post, we’ve provided a list of 43 Best PCB Design Software for you.

Step 4 - Electronic Test

Test boards using protoboards, breadboards or paper circuits.

Step 5 - Modify and refine design

Because PCB design is an art, no one can provide you a perfect solution. However, you can follow some guidelines to refine your design.

  1. Design for functions and not for product look;
  2.  Avoid overlapping components’ pads;
  3. Use thin traces and wide spaces between components;
  4. Add component pins at an angle close to PCB surface to reduce bending stress on the component pins. This will result in more reliable connections.

Tips for Decipher Electronic Schematic Diagrams

1. the rational division of functional areas

In the reverse design of the schematic diagram of a complete PCB circuit board, the reasonable division of functional areas can help engineers reduce some unnecessary troubles and improve the efficiency of drawing.

Generally speaking, components with the same function on a PCB will be centrally arranged, and the functional division of the area can provide a convenient and accurate basis for inferring the schematic diagram. However, the division of this functional area is not arbitrary. It requires engineers to have a certain understanding of electronic circuit related knowledge.

First, find out the core components in a functional unit, and then find out other components of the same functional unit according to the wiring connections to form a functional partition. The formation of functional partitions is the basis for schematic drawing. In addition, clever use of the component serial numbers on the circuit board in the process of functional partitioning is conducive to faster functional partitioning.

2. finding the reference parts

The reference parts can be said to be the main components to be used at the beginning of the schematic drawing. After the reference parts are determined, they are drawn according to the pins of these reference parts, which can ensure the accuracy of the schematic to the greatest extent. For engineers, the determination of reference parts is not very complicated. In general, the components that play a major role in the circuit can be selected as reference parts. They are generally larger in size and have more pins, which are convenient for drawing. Such as integrated circuits, pcb transformers, transistors, etc., can be used as a suitable reference.

3. correctly distinguish the lines and draw the wiring reasonably

For the distinction between ground wires, power wires, and signal wires, engineers also need to have relevant power supply knowledge, circuit connection knowledge, PCB wiring knowledge, and so on. The distinction of these circuits can be analyzed from the connection of components, the width of the copper foil of the circuit, and the characteristics of the electronic product itself. In wiring drawing, in order to avoid line crossing and interspersed, a large number of grounding symbols can be used for grounding lines, different lines of different colors can be used for various lines to ensure clear and distinguishable lines, and special signs can also be used for various components. The unit circuits are drawn separately and combined at the end.

4. master the basic framework and learn from similar schematic diagrams

Engineers need to be proficient in the frame composition and schematic drawing of basic electronic circuits, not only to be able to directly draw some simple and classic basic unit circuits, but also to be able to form the overall framework of electronic circuits. In addition, the same type of electronic products have certain similarities in the schematic diagrams, and engineers can fully refer to similar circuit diagrams to reverse the new product schematics based on the accumulation of experience.

5. checking and optimizing schematic diagram

After the schematic diagram is drawn, the reverse design of the PCB schematic diagram can only be said to be completed after a test and verification process. The nominal values ​​of components that are sensitive to PCB distribution parameters need to be checked and optimized. According to the PCB file diagram, the schematic diagram is compared, analyzed and checked to ensure that the schematic diagram and the file diagram are completely consistent. If it is found in the check that the layout of the schematic diagram does not meet the requirements, the schematic diagram will be adjusted until it is completely reasonable and standardized, accurate and clear.

PCB Reverse Engineering Services

In the practice of PCB reverse engineering for many years, we have accumulated rich experience and mastered hundreds of reverse push methods. Combined with the latest PCB reverse schematic software, we can provide customers with a variety of high-frequency board reverse drawing schematics and modification. Furthermore, reverse design of schematic diagram of multi-layer blind buried hole board, 8-layer server computer motherboard, etc.

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About Author

Aidan Taylor
Aidan Taylor

I am Aidan Taylor and I have over 10 years of experience in the field of PCB Reverse Engineering, PCB design and IC Unlock.

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