PCB News - Teach you to understand the whole process of reverse pushing of PCB circuit board schematic diagram

Teach you to understand the whole process of reverse pushing of PCB circuit board schematic diagram

PCB circuit board copying is often called circuit board copying, circuit board copying, PCB cloning, circuit board cloning, circuit board cloning, PCB reverse design or reverse development of PCB circuit board in the circuit board industry.

That is, on the premise that there are physical objects of electronic products and circuit boards, reverse analysis of circuit boards using reverse research and development techniques, and the original product PCB circuit board files, bill of materials (BOM) files, schematic files and other technologies Documents and PCB circuit board silk screen production documents are restored 1:1.

Then use these technical documents and production documents for PCB circuit board production, component welding, flying probe testing, circuit board debugging, and complete the complete copy of the original circuit board template.

Many people don't know what PCB copy board is. Some people even think that PCB copy board is a copycat.

In everyone’s understanding, copycat means imitate, but PCB copy board is definitely not imitation. The purpose of PCB copy board is to learn the latest foreign electronic circuit design technology, and then absorb excellent design solutions, and then use it for development. Design better products.

With the continuous development and deepening of the circuit board copy board industry, today's PCB circuit board copy board concept has been extended to a wider range. It is no longer limited to simple copying and cloning of circuit boards, but also involves the secondary development of products. And the research and development of new products.

For example, through the analysis and discussion of existing product technical documents, design ideas, structural features, process technology, etc., it can provide feasibility analysis and competitive reference for the development and design of new products, and assist R&D and design units to follow up the latest updates in time Technological development trends, timely adjustment and improvement of product design plans, and research and development of the most competitive new products in the market.

The process of PCB copying can realize the rapid update, upgrade and secondary development of various types of electronic products through the extraction and partial modification of technical data files. Willing to optimize the design and modification of PCB circuit boards.

It is also possible to add new functions to the product or redesign the functional features on this basis, so that products with new functions will be unveiled at the fastest speed and with a new attitude, not only having their own intellectual property rights, but also in the market It has won the first opportunity and brought double benefits to customers.

Whether it is used to analyze circuit board principles and product operating characteristics in reverse research, or is reused as the basis and basis of PCB design in forward design, PCB schematics have a special role.

So, how to reverse the schematic diagram of the PCB circuit board according to the file diagram or the actual object, and what is the reverse pushing process? What are the details to pay attention to?

1. Reverse steps:

1. Record the relevant details of the PCB circuit board

Get a PCB board, first record the model, parameters, and positions of all components on the paper, especially the direction of the diode, the triode, and the direction of the IC gap. It is best to use a digital camera to take two photos of the location of the components. Many PCB circuit boards are becoming more and more advanced. Some of the diode transistors on the above are not noticed at all.

2. Scanned image

Remove all components and remove the tin in the PAD hole. Clean the PCB with alcohol and put it into the scanner. When the scanner scans, you need to raise the scanned pixels slightly to get a clearer image. Then lightly polish the top and bottom layers with water gauze until the copper film is shiny, put them in the scanner, start PHOTOSHOP, and scan the two layers in separately in color.

Note that the PCB circuit board must be placed horizontally and vertically in the scanner, otherwise the scanned image cannot be used.

3. Adjust and correct the image

Adjust the contrast and brightness of the canvas to make the part with copper film and the part without copper film have a strong contrast, then turn the second image into black and white, and check whether the lines are clear. If not, repeat this step. If it is clear, save the picture as black-and-white BMP format files TOPBMP and BOTBMP. If there is a problem with the picture, you can use PHOTOSHOP to repair and correct it.

4. Verify the positional coincidence of PAD and VIA

Convert the two BMP format files to PROTEL format files, and transfer them into two layers in PROTEL. For example, the positions of PAD and VIA that have passed through the two layers basically coincide, indicating that the previous steps have been done well. If there is a deviation, then Repeat the third step. Therefore, PCB copying is a work that requires patience, because a small problem will affect the quality and the degree of matching after copying.

5. The drawing layer of the circuit board

Convert the BMP of the TOP layer to TOPPCB, pay attention to the conversion to the SILK layer, which is the yellow layer, and then you can trace the line on the TOP layer, and place the device according to the drawing in the second step. Delete the SILK layer after drawing. Repeat until all the layers are drawn.

6. TOPPCB and BOTPCB combined picture

Import TOPPCB and BOTPCB in PROTEL and combine them into one picture and it will be OK.

7. Laser printing TOPLAYER, BOTTOMLAYER

Use a laser printer to print TOPLAYER and BOTTOMLAYER on transparencies (1:1 ratio), put the film on the PCB, and compare whether there are errors. If they are correct, you are done.

8. Copy board test of circuit board

Test whether the electronic technical performance of the copy board is the same as the original board. If it is the same, it is really done.

2. Pay attention to details

1. Reasonably divide functional areas

When performing the reverse design of the schematic diagram of a good PCB circuit board, a 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 are arranged in a concentrated manner, and the division of areas by function can have a convenient and accurate basis when inverting 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 the core component in a certain functional unit, and then according to the wiring connection, you can find other components of the same functional unit along the way to form a functional partition.

The formation of functional partitions is the basis of schematic drawing. In addition, in this process, don't forget to use the serial numbers of the components on the circuit board cleverly, they can help you partition the functions faster.

2. Find the right reference parts

This reference part can also be said to be the main component PCB net city used at the beginning of the schematic drawing. After the reference part is determined, it is drawn according to the pins of these reference parts, which can ensure the accuracy of the schematic drawing to a greater extent. sex.

For engineers, the determination of reference parts is not very complicated. Under normal circumstances, 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 is convenient for drawing. Such as integrated circuits, transformers, transistors, etc., can all be used as suitable reference components.

3. Correctly distinguish lines and draw 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 lines can be analyzed in terms of the connection of components, the width of the copper foil of the line, and the characteristics of the electronic product itself.

In the wiring drawing, in order to avoid the crossing and interpenetration of lines, a large number of grounding symbols can be used for the grounding line. Various lines can use different colors and different lines to ensure that they are clear and identifiable. For various components, special signs can be used, or even Draw the unit circuits separately, and finally combine them.