1. Chemical Solvent Method
Principle:Uses specific solvents to dissolve or swell the conformal coating before scraping. The solvent must exhibit good solubility for the coating material while causing no damage to the object being cleaned.
Advantages:
- Simple operation; currently the most commonly used method;
- Suitable for acrylic, polyurethane, and similar coatings.
Disadvantages:
- Time-consuming;
- Relies on solvent compatibility; changing conformal coating types requires solvent changes, and some coating types are difficult to dissolve and remove;
- Some solvents may corrode or damage PCBs or components while dissolving the conformal coating;
- Residual solvents may corrode the substrate;
- May involve chemical cleaning, increasing process costs;
- Involves potential hazards in chemical storage and handling;
- May involve pollution and emission issues; some solvents are toxic and require strict ventilation, posing potential health risks to operators.
2. Thermal Decomposition Method
Principle:Uses high temperatures from soldering irons, heat guns, or ovens to soften or decompose the coating before peeling.
Advantages:
- Suitable for small-scale, localized treatment;
- No chemical reagents required.
Disadvantages:
- Difficult temperature control;
- High temperatures can easily cause substrate warping, discoloration, and solder joint oxidation;
- Not suitable for multilayer boards;
- Coating decomposition may release toxic gases;
- Only applicable to certain coating materials;
- May adversely affect heat-sensitive components.
3. Mechanical Scraping Method
Principle:Uses tools such as scrapers, sandpaper, or wire brushes to physically abrade and remove the coating.
Advantages:Low cost; suitable for simple applications.
Disadvantages:
- High risk of damaging circuit traces;
- Residual coating films may affect subsequent soldering;
- Not suitable for precision devices or high-reliability products;
- Low rework pass rate.
4. Micro-Blasting Method
Principle:Uses compressed air to drive specially formulated micron-grade abrasive media to impact and remove the coating.
Advantages:
- Capable of both selective localized removal and full-board removal with high efficiency and precision;
- Adjustable blasting pressure accommodates different materials and coating thicknesses without damaging substrates;
- Suitable for precision electronic products.
Disadvantages:
- Higher equipment cost compared to other methods;
- Requires operator proficiency to avoid damaging unrelated areas.
