How to apply conformal coating using spray/aerosol?
Conformal coating is a protective material applied to electronic circuitry to protect it from environmental factors such as moisture, dust, chemicals, and temperature extremes. Applying conformal coating by spray and aerosol methods is a common practice in the electronics industry. Here's an overview of the process for both methods:
1. Surface Preparation:
  • Before applying conformal coating, it's crucial to ensure that the surfaces to be coated are clean and free from contaminants such as dust, oils, and residues.
  • Cleaning methods may include using solvents, brushes, or specialized cleaning equipment.
2. Masking:
  • Components that should not be coated, such as connectors, switches, and certain areas of the board, are often masked using tapes or liquid masking materials.
3. Selection of Conformal Coating:
  • Choose the appropriate conformal coating material based on the specific requirements of the application and the environmental conditions the electronics will be exposed to.
  • Common types include acrylics, urethanes, silicones, and epoxies.
4. Mixing (if required):
  • Some conformal coatings come as a two-part system that needs to be mixed before application. Follow the manufacturer's instructions for proper mixing ratios and procedures.
5. Application by Spray:
  • Using a spray gun or automated spray system, the conformal coating is evenly applied to the surface of the PCB (Printed Circuit Board).
  • The spray gun should be held at an optimal distance and moved at a consistent speed to ensure uniform coverage.
6. Application by Aerosol:
  • Conformal coating in aerosol form is available in cans with a nozzle for direct application.
  • Ensure the aerosol is shaken well before use to mix the coating material properly.
7. Curing:
  • Allow the conformal coating to cure or dry based on the manufacturer's recommendations. This may involve air drying, heat curing, or UV curing depending on the type of coating used.
8. Inspection:
  • After the conformal coating has cured, inspect the coated surface for uniformity, coverage, and the absence of defects.
  • Special attention should be given to areas near masked components to ensure there are no coating bridges or voids.
9. Testing:
  • Perform electrical testing to ensure that the conformal coating has not adversely affected the functionality of the electronic components.
10. De-masking (if applied):
  • Remove any masking materials that were applied before coating.
11. Final Inspection:
  • Conduct a final inspection to ensure that the conformal coating meets the desired standards and provides the necessary protection.

As this is a semi-skilled process, training is vital for a consistent process.  Following proper procedures and guidelines from the conformal coating material manufacturer is essential to achieve optimal results and ensure the reliability of the coated electronic assemblies.