sales@ipcb.com
In simple terms, the technical implementation process of PCBA copy board is to scan the circuit board to be copied first, record the detailed location of components, then remove the components to make a bill of materials (BOM list) and arrange material procurement. The empty board is scanned into a picture and processed by the copy board software to restore it to a PCB board file, and then the PCB gerber file is sent to the SMT factory for board making. After the board is made, the purchased components are soldered to the made PCBA copy board, and then the circuit board is tested and debugged.
1. Specific steps of PCBA copy board
(1) Get a PCB, first record the model, parameters, and position of all components on paper, especially the direction of diodes, triodes, and the direction of IC gaps. It is best to take two photos of the position of components with a digital camera. Nowadays, PCB circuit boards are becoming more and more advanced, and some diodes and triodes on them are not visible at all if you don't pay attention.
(2) Remove all multilayer board copy board components and remove the tin in the PAD hole. Clean the PCB with alcohol and put it in the scanner. When scanning, the scanner needs to slightly increase the scanning pixels to get a clearer image. Then use water gauze paper to lightly polish the top and bottom layers until the copper film is shiny, put them into the scanner, start PHOTOSHOP, and scan the two layers separately in color. Note that the PCB must be placed horizontally and vertically in the scanner, otherwise the scanned image cannot be used.
(3) Adjust the contrast and brightness of the canvas to make the contrast between the part with copper film and the part without copper film strong, then convert the secondary image to black and white, check whether the lines are clear, if not, repeat this step. If it is clear, save the image as black and white BMP format files TOP.BMP and BOT.BMP. If you find that there is a problem with the graphics, you can use PHOTOSHOP to repair and correct it.
(4) Convert the two BMP format files to PROTEL format files respectively, and call the two layers in PROTEL. If the positions of the PAD and VIA of the two layers are basically overlapped, it means that the previous steps are done well. If there is a deviation, repeat the third step. Therefore, PCB copying is a very patient job, because a small problem will affect the quality and the matching degree after copying.
(5) Convert the BMP of the TOP layer to TOP.PCB. Note that it should be converted to the SILK layer, which is the yellow layer. Then draw the lines on the TOP layer and place the components according to the drawing in the second step. Delete the SILK layer after drawing. Repeat until all layers are drawn.
(6) Import TOP.PCB and BOT.PCB into PROTEL and combine them into one drawing.
(7) Use a laser printer to print TOP LAYER and BOTTOM LAYER on transparent film (1:1 ratio), put the film on the PCB, and compare whether there is any error. If there is no error, you are done. A copy board that is the same as the original board is 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. Note: If it is a multi-layer board, you need to carefully polish the inner layer, and repeat the third to fifth steps of copying. Of course, the naming of the graphics is different, depending on the number of layers. Generally, double-sided board copying is much simpler than multi-layer board. Multi-layer board copying is prone to misalignment, so multi-layer board copying should be particularly careful and careful (internal vias and non-vias are prone to problems).
2. Double-sided board copying method
(1) Scan the upper and lower surfaces of the circuit board and save two BMP images.
(2) Open the copying software Quickpcb2005, click "File" "Open Base Map", and open a scanned image. Use PAGEUP to enlarge the screen, see the pad, press PP to place a pad, see the line and press PT to route... Just like a child tracing, trace it in this software, click "Save" to generate a B2P file.
(3) Click "File" and "Open Base Map" to open the scanned color image of another layer;
(4) Click "File" and "Open" to open the B2P file saved earlier. We can see that the board we just copied is superimposed on 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" to turn off the display of the top-layer circuits and silk screens here, leaving only the multi-layer vias.
(5) The vias on the top layer are in the same position as the vias on the bottom layer picture. Now we can trace the bottom layer circuits like we did in childhood. Click "Save" again - the B2P file now has data for the top and bottom layers.
(6) Click "File" and "Export to PCB File" to get a PCB file with two layers of data. You can modify the board or generate a schematic diagram or send it directly to the PCB plate-making factory for production.
3. Multi-layer board copying method
In fact, copying a four-layer board is to copy two double-sided boards repeatedly, and copying a six-layer board is to copy three double-sided boards repeatedly... The reason why multi-layer boards are daunting is that we cannot see the internal routing. How can we see the inner layer of a precise multilayer board? - Layering.
There are many ways to layer now, such as chemical corrosion and tool stripping, but it is easy to over-layer and lose data. Experience tells us that sandpaper polishing is the most accurate.
After we copy the top and bottom layers of the PCB, we usually use sandpaper to polish it, grinding off the surface layer to show the inner layer; sandpaper is the ordinary sandpaper sold in hardware stores. Generally, the PCB is laid flat, and then the sandpaper is pressed and rubbed evenly on the PCB (if the board is very small, the sandpaper can also be laid flat, and one finger is pressed on the PCB and rubbed on the sandpaper). The key point is to lay it flat so that it can be polished evenly.
Silk screen and green oil usually fall off with one wipe, and copper wire and copper skin need to be wiped several times. Generally speaking, the Bluetooth board can be wiped in a few minutes, and the memory stick takes about ten minutes; of course, if you have more strength, it will take less time; if you have less strength, it will take more time.
Grinding the board is currently the most common solution for layering, and it is also the most economical. We can try to find a discarded PCB. In fact, grinding the board is not technically difficult, but it is a bit boring and takes some effort. Don't worry about grinding the board through or grinding your fingers.
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 it can achieve the best effect.
Usually, it can be examined from the following aspects:
(1) Whether the system layout ensures the rationality or optimality of the wiring, whether it can ensure the reliable wiring, and whether it can ensure the reliability of the circuit operation. When laying out, it is necessary to have an overall understanding and planning of the signal direction and the power and ground network.
(2) Whether the size of the printed circuit board is consistent with the size of the processing drawing, whether it can meet the PCB manufacturing process requirements, and whether there are behavioral marks. This needs special attention. The circuit layout and wiring of many PCBA copy boards are designed beautifully and reasonably, but the precise positioning of the positioning connector is neglected, resulting in the designed circuit being unable to connect with other circuits.
(3) Whether there is any conflict between components in two-dimensional and three-dimensional space. Pay attention to the actual size of the device, especially the height of the device. When welding layout-free components, the height should generally not exceed 3mm.
(4) Whether the layout of components is orderly and neatly arranged, and whether all layouts are completed. When laying out components, not only the direction and type of signals, places that need attention or protection should be considered, but also the overall density of the device layout should be considered to achieve uniform density.
(5) Whether components that need to be replaced frequently can be replaced conveniently, and whether the plug-in board can be inserted into the device conveniently. The replacement and plug-in of components that are frequently replaced should be convenient and reliable.
The process of PCBA copy board mainly includes: scanning the original circuit board, disassembling and recording component information, cleaning and polishing the board surface, using professional software to draw PCB diagrams, making bills of materials and purchasing, and finally welding components and conducting circuit testing and debugging. There are detailed differences in the copying methods of double-sided boards and multi-layer boards, especially multi-layer boards need to be polished and layered to observe the internal routing. The whole process requires high precision and patience to ensure that the performance of the copied circuit board is consistent with the original board.