Coating three anti-paint is generally the last process in PCB assembly. However, in the final inspection, electronic components may have defects, and the three anti-paint coatings are required to be repaired.

    For electronic components used in harsh environments, the application of three anti-paint can provide various protections for the circuit board: moisture, mildew, dust, insulation, minimize dendrite growth, release stress and so on. Three anti-paints make electronic components more durable, improve the reliability of electronic equipment, and reduce the cost of warranty.

    When the board needs to be reworked, the expensive components on the board can be removed separately and the rest can be discarded. But the more common method is to remove the protective film at all or part of the board and replace the damaged components one by one. When removing the three anti-paint protective film, make sure that the substrate, other electronic components, and the structure near the repair position are not damaged. The protective film removal method mainly includes: using chemical solvent, micro-grinding, mechanical method and desoldering through a protective film.

    The use of chemical solvents is the most common method of removing the three anti-paint protective film, and its key is the chemical nature of the protective film to be removed and the chemical nature of the specific solvent. Micro-grinding is the use of high-speed particles ejected from a nozzle to "grind" the three anti-paint protective film on the board. The mechanical method is the easiest way to remove the three anti-paint protective film. De-soldering through the protective film is to first open a discharge hole in the protective film to allow the molten solder to be discharged.