PCB Technical - Detailed explanation of PCB copy and anti-copy countermeasures

The specific steps of PCB copy board:

The first step is to get a PCB. First, record the model, parameters, and positions of all vital parts on the paper, especially the direction of the diode, the tertiary tube, and the direction of the IC gap. It is best to use a digital camera to take two photos of the location of the vital parts. The current PCB circuit boards are getting more and more advanced. Some of the diode transistors above are not noticed at all.

The second step is to remove all the multi-layer boards and copy the boards, 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 must be placed horizontally and vertically in the scanner, otherwise the scanned image cannot be used.

The third step is to adjust the contrast, brightness and darkness 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 TOP.BMP and BOT.BMP. If you find any problems with the graphics, you can also use PHOTOSHOP to repair and correct them.

The fourth step is to convert the two BMP format files to PROTEL format files, and transfer 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 are well done. If If there is a deviation, 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.

The fifth step is to convert the BMP of the TOP layer to TOP.PCB, 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. Keep repeating until all the layers are drawn.

The sixth step is to import TOP.PCB and BOT.PCB in PROTEL, and it is OK to combine them into one picture.

The seventh step, use a laser printer to print TOP LAYER and BOTTOM LAYER on transparent film (1:1 ratio), put the film on that PCB, and compare whether there are errors. If they are correct, you are done. .

A copy board that is the same as the original board was born, but this is only half done. It is also necessary to 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.

Remarks: If it is a multilayer board, you need to carefully polish to the inner layer, and repeat the copying steps from the third to the fifth step. Of course, the naming of the graphics is also different. It depends on the number of layers. Generally, double-sided copying requires It is much simpler than multi-layer boards. Multi-layer copy boards are prone to misalignment. Therefore, multi-layer board copy boards must be especially careful and careful (wherein the internal vias and non-vias are prone to problems).

Double-sided copy board method:

1. Scan the upper and lower layers of the circuit board and save two BMP pictures.

2. Open the copy board software Quickpcb2005, click "File" and "Open Base Map" to open a scanned picture. Use PAGEUP to zoom in on the screen, see the pad, press PP to place a pad, see the line and follow the PT to route... Just like a child drawing, draw it in this software, click "save" to generate a B2P file.

3. Click "File" and "Open Base Image" to open another layer of scanned color image;

4. Click "File" and "Open" again to open the B2P file saved earlier. We see the newly copied board, stacked on top of this picture-the same PCB board, the holes are in the same position, but the circuit connections are different . So we press "Options"-"Layer Settings", turn off the top-level line and silk screen display here, leaving only multi-layer vias.

5. The vias on the top layer are in the same position as the vias on the bottom picture. Now we can trace the lines on the bottom layer as we did in childhood. Click "Save" again-the B2P file now has two layers of information on the top and bottom layers.

6. Click "File" and "Export as PCB File", and you can get a PCB file with two layers of data. You can change the board or reproduce the schematic diagram or send it directly to the PCB plate factory to produce multi-layer board copying methods:

In fact, the four-layer board copying is repeated copying two double-sided boards, and the sixth layer is repeated copying three double-sided boards... The reason why the multi-layer board is daunting is because we cannot see the internal wiring. How do we see the inner layers of a precision multilayer board? -Layering.

There are many methods of layering, such as potion corrosion, tool stripping, etc., but it is easy to separate the layers and lose data. Experience tells us that sandpaper polishing is the most accurate.

When we finish copying the top and bottom layers of the PCB, we usually use sandpaper to polish the surface layer to show the inner layer; sandpaper is ordinary sandpaper sold in hardware stores, generally flat PCB, and then hold the sandpaper and rub evenly on the PCB (If the board is small, you can also flatten the sandpaper, and rub the sandpaper while pressing the PCB with one finger). The main point is to pave it flat so that it can be ground evenly.

The silk screen and green oil are generally wiped off, and the copper wire and copper skin should be wiped a few times. Generally speaking, the Bluetooth board can be wiped in a few minutes, and the memory stick will take about ten minutes; of course, if you have more energy, it will take less time; if you have less energy, it will take more time.

Grinding board is currently the most common solution used for layering, and it is also the most economical. We can find a discarded PCB and try it. In fact, it is not technically difficult to grind the board. It is just a bit boring.

PCB drawing effect review

During the PCB layout process, after the system layout is completed, the PCB diagram should be reviewed to see whether the system layout is reasonable and whether the optimal effect can be achieved. It can usually be investigated from the following aspects:

1. Whether the system layout guarantees reasonable or optimal wiring, whether the wiring can be carried out reliably, and whether the reliability of the circuit operation can be guaranteed. In the layout, it is necessary to have an overall understanding and planning of the direction of the signal, as well as the power supply and ground wire network.

2. Whether the size of the printed board is consistent with the size of the processing drawing, whether it can meet the requirements of the PCB manufacturing process, and whether there is a behavior mark. This point requires special attention. The circuit layout and wiring of many PCB boards are designed very beautifully and reasonably, but the precise positioning of the positioning connector is neglected, resulting in the design of the circuit cannot be docked with other circuits.

3. Whether the components conflict in two-dimensional and three-dimensional space. Pay attention to the actual size of the device, especially the height of the device. When welding components that are free of layout, the height should generally not exceed 3mm.

4. Whether the layout of components is dense and orderly, neatly arranged, and whether they are all laid out. In the layout of components, not only the direction of the signal, the type of signal, and the places that need attention or protection must be considered, but also the overall density of the device layout must be considered to achieve uniform density.

5. Whether the components that need to be replaced frequently can be easily replaced, and whether the plug-in board can be easily inserted into the equipment. The convenience and reliability of replacement and connection of frequently replaced components should be ensured.