Detailed explanation of the principle of reverse deduction of PCB copy board

In PCB reverse technology research, reverse deduction of schematic diagram refers to the reverse deduction of PCB circuit diagram based on PCB file diagram or direct drawing of PCB circuit diagram based on the actual product, aiming to explain the principle and working condition of the circuit board. In addition, this circuit diagram is also used to analyze the functional characteristics of the product itself. In forward design, the development of general products must first carry out schematic design, and then carry out PCB design based on the schematic diagram.

Whether it is used to analyze the principle of circuit board and product working characteristics in reverse research, or is reused as the basis and basis of PCB design in forward design, PCB schematic diagram has a special role. So, according to the file diagram or the actual object, how to reverse the PCB schematic diagram, and what details should be paid attention to in the reverse deduction process?

1.Reasonable division of functional areas

When reverse designing the schematic diagram of a complete PCB circuit board, 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 board will be arranged in a concentrated manner, and dividing the area by function can provide a convenient and accurate basis for reverse deduction of 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 certain functional unit, and then according to the wiring connection, you can find out other components of the same functional unit to form a functional partition. The formation of functional partitions is the basis for schematic drawing. In addition, in this process, don’t forget to cleverly use the serial numbers of components on the circuit board, which can help you to perform functional partitions faster.

2.Correctly distinguish the lines and draw the wiring reasonably

For the distinction between ground wires, power lines, and signal lines, engineers also need to have relevant power supply knowledge, circuit connection knowledge, PCB wiring knowledge, etc. The distinction between these lines can be analyzed from the connection of components, the width of the copper foil of the line, and the characteristics of the electronic product itself.

In wiring drawing, in order to avoid crossing and interlacing of lines, a large number of grounding symbols can be used for ground wires, and different lines of different colors can be used for various lines to ensure clarity. Special signs can also be used for various components, and even unit circuits can be drawn separately and then combined.

3.Find the right reference parts

This reference part can also be said to be the main component used at the beginning of schematic drawing. After determining the reference parts, drawing according to the pins of these reference parts can ensure the accuracy of the schematic diagram to a greater extent.

For engineers, the determination of reference parts is not a very complicated matter. Generally, components that play a major role in the circuit can be selected as reference parts. They are generally large in size and have more pins, which is convenient for drawing. For example, integrated circuits, transformers, transistors, etc. can all be used as suitable reference parts.

4.Master the basic framework and learn from similar schematics

For some basic electronic circuit frameworks and schematic drawing techniques, engineers need to master them proficiently. They should not only be able to directly draw the basic components of some simple and classic unit circuits, but also be able to form the overall framework of electronic circuits.

On the other hand, don’t ignore that the same type of electronic products have certain similarities in the schematic diagram. Engineers can use their experience to fully learn from similar circuit diagrams to reverse the schematic diagram of new products.

5.Verification and optimization

After the schematic diagram is drawn, it must go through the testing and verification process before the reverse design of the PCB schematic diagram can be said to be over. The nominal values ​​of components that are sensitive to PCB distributed 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.