Step 1: Preparation First, examine the circuit board to identify any high-position components and record their location number, package, temperature value, etc. Take a backup scan of the board before removing any components. After removing the high-position components, scan the board again and record the image at a resolution of 600dpi. Make sure to clean the surface of the PCB before scanning to ensure that the IC model and the characters on the PCB are clearly visible in the picture.
Step 2: Disassemble components and create BOM Use a small air gun to heat and remove components, starting with resistors, then capacitors, and finally ICs. Record all components on a table, including the number, package, model, value, and other relevant information. Then, paste double-sided tape on the component record column and attach the removed components to the corresponding position of the position number. Use a bridge to measure the value of all components, and input the data into the computer for archiving.
Step 3: Remove surface tin Use flux to remove the remaining tin dross from the PCB surface where the components were removed with a tin suction wire. Adjust the temperature of the soldering iron appropriately according to the number of PCB layers. Wash the board with board washing water or thinner water, and then dry it.
Step 4: Real-time operation in the copy board software After scanning the surface image, set them as the top and bottom layers respectively, and convert them into bottom images that can be recognized by various copying software. According to the bottom images, first package the components, including small silkscreen, pad aperture, positioning holes, etc. After all the components are completed, put them in the corresponding position, adjust the characters to make the font, font size, and position consistent with the original board. Then proceed to the next step.
Use sandpaper to remove the silkscreen, ink, and characters on the PCB surface, exposing bright copper. Sand the pad perpendicular to the scanner’s scanning direction. For multi-layer boards, remove the first and eighth layers of ink, copy the first and eighth layers, and polish off the first and eighth layers of copper. Then copy the second and seventh layers, the third and sixth layers, and finally, copy the fourth and fifth layers. Make sure the scanned image size and direction are consistent with the real board. Adjust the position of the PCB components one by one to make them coincide entirely with the base map for the next step to place vias, trace wires, and lay copper.
Step 5: Check Use image processing software, PCB drawing software, and the physical connection of the circuit to make a 100% accurate judgment. Test the impedance of the high-frequency board or measure the copper thickness and layer spacing with a metallurgical microscope. Analyze the dielectric of the substrate constant to ensure that the PCB indicators are consistent with the original board.
Precision adjustment correction The accuracy of the copy board depends on the accuracy of the original image. The higher the DPI, the clearer the picture and the higher the accuracy. Scanners on the market can meet high DPI requirements. The DPI should be set based on the precision required for the actual board. For general precision boards, 400 DPI is sufficient, while mobile phone boards require above 1000 DPI.