How to Repair PCB Conformal Coating
PCB conformal coating is generally the last step of PCB assembly process, however, in the final test, the electronic components may be defective, then PCB conformal coating is required to be repaired.
For electronic components using in harsh environments, conformal coating can provide a variety of protections to PCB board, such as anti-moisture, anti-leakage, anti-shock, anti-dust, anti-corrosion, anti-aging, corona resistance, minimize the growth of dendrites, etc. Conformal coating makes electronic components more durable, improves the reliability of electronic equipment and reduces warranty costs.
When a PCB board needs to be repaired, you can take the expensive components out of the board separately and discard the rest. However, the more common method is to remove all or part of the circuit board conformal coating, and replace the damaged components one by one. When remove the conformal coating, ensure that will not damage electronic components, the substrate under the components, structures near the repair location, etc. The conformal coating removal methods includes: the use of chemical solvents, micro-grinding, mechanical method and desoldering through the coating.
The use of chemical solvents is the most commonly used method of removing PCB conformal coating, the key of which is to remove the chemical properties of the coating and the specific solvent chemistry. Micro-grinding is the use of high-speed particles jet nozzle, grinding off the coating on the printed circuit board. Mechanical method is the easiest way to remove conformal coating. Desoldering through the coating is to open a vent hole in the coating, so that the molten solder can be discharged.