The circuit board after the curing of the three proofing paint may still be repaired, which requires removing the paint film before replacing the components. Here are several common methods for removing three proofing paint.
1、 Heating method is not recommended as a last resort. The specific operation of the heating method is to generally use an electric soldering iron to directly heat to a certain temperature to burn through the three prevention paint film. However, most cured three proof paint films can withstand high temperatures, so temperature control during heating is very important, as it is necessary to burn the paint film thoroughly without damaging the product. Some temperature sensitive components are not suitable for this method, and this method can cause discoloration or aging of the paint film next to the heating zone, leaving some residues, and even some types of three proofing paint may release toxic gases after heating. Therefore, it is necessary to be cautious before use.
2、 Micro grinding method, which uses a special instrument to polish off local paint films without damaging the product, but requires high operating skills from the operator.
3、 Chemical method, which uses specific chemical solvents to dissolve and solidify the three prevention paint film, is the most commonly used method because it is simple and easy to operate without causing damage to the product. Different solvents need to be selected based on different types of three proofing paints (usually recommended stripping agents are provided by reputable manufacturers):
1. Polyurethane: Methanol and alkaline activator solution, ethylene glycol ether and alkaline activator solution, or toluene xylene can also be used;
2. Acrylic acid: dichloromethane, chloroform, ketones, butyrolactone, butyl acetate;
3. Silicone: dichloromethane, and some hydrocarbons;
4. Epoxy resin: It is almost impossible to completely remove, and small areas can be wiped with dichloromethane and acidic activator, combined with medicinal cotton swabs.
Regarding UV adhesive, it is quite special because it is a cross-linking reaction and has a high degree of curing after reacting with moisture. It has high hardness and adhesion, making it difficult to dissolve with solvents. Although most manufacturers also provide matching stripping agents, they are usually within 24 or 12 hours. Once fully cured, they cannot produce any effect. For this situation, we generally recommend using the first two methods, namely heating method or micro grinding method.