Introduction to circuit board conformal coating rework

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Introduction to circuit board conformal coating rework [Copy link]

Conformal coating is usually the last process in PCB assembly. However, during the final inspection, electronic components may have defects, which requires the conformal coating to be repairable. For electronic components used in harsh environments, conformal coating can provide various protections for circuit boards: moisture-proof, mildew-proof, dust-proof, insulation, minimize dendrite growth, release stress, etc. Conformal coating makes electronic components more durable, improves the reliability of electronic equipment, and reduces warranty costs. When a circuit board needs to be repaired, the expensive components on the circuit board can be taken out separately and the rest can be discarded. However, the more common method is to remove the protective film from all or part of the circuit board and replace the damaged components one by one. When removing the conformal coating protective film, make sure that the substrate under the component, other electronic components, and the structure near the repair location will not be damaged. The methods for removing the protective film mainly include: using chemical solvents, micro-grinding, mechanical methods, and desoldering through the protective film. Using chemical solvents is the most common method for removing conformal coating protective films. The key lies in the chemical properties of the protective film to be removed and the chemical properties of the specific solvent. Micro-grinding uses high-speed particles ejected from a nozzle to "grind" away the conformal coating on the circuit board. Mechanical methods are the easiest way to remove the conformal coating. To remove solder through the protective film, first open a drain hole on the protective film to allow the molten solder to drain.

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Conformal coating is usually the last process in PCB assembly. However, during the final inspection, electronic components may have defects, which requires the conformal coating to be repairable.