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How to apply conformal coating by brushing?

Applying conformal coating by brushing is a manual method that involves using a brush to coat the surface of electronic assemblies with a protective material. This straightforward, yet delicate process offers various benefits for applications where automated processes may not be practical. However, while the simplicity of manual brushing is evident, neglecting some essential considerations can lead to significant issues. This guide will review everything you need to know to ensure you achieve the best results when applying conformal coating by hand.


The Benefits of Manual Hand Brushing Application

Manual hand brushing of conformal coating provides a number of benefits in specific contexts. The main ones are:

  • Precision: It allows for precise application on small or hard-to-reach areas that automated systems may miss.
  • Cost-Effective: It’s ideal for low-volume production or prototype development, reducing the need for expensive automated equipment.
  • Flexibility: It’s suitable for rework and repairs, where specific areas need additional coating without disturbing the entire assembly.


Equipment Needed for Brushing Application

To apply conformal coating by brushing, you will need:

  • Conformal coating material
  • High-quality, clean brushes compatible with the coating material
  • Small glass or chemically resistant container to pour the coating in
  • Cleaning solvents or agents for surface preparation (if required)
  • Masking tape or other masking materials (if required)


Applying Conformal Coating by Brushing, Step-by-Step:


  1. Preparation: Ensure that the electronic assembly is clean and free from contaminants and residues. Use appropriate solvents or cleaning agents if necessary. This step is crucial for the adhesion and effectiveness of the conformal coating.
  2. Masking: Use masking tapes or other protective materials to cover any components or areas that should not be coated, such as connectors, switches, or sensitive devices.
  3. Material Selection: Select your conformal coating material based on the specific requirements of the application. Common types include acrylics, urethanes, silicones, and epoxy-based coatings. Manufacturers such as Humiseal offer various options, suitable for different environmental conditions and performance needs.
  4. Viscosity Check: Ensure that the viscosity of the conformal coating material is suitable for brushing. We recommend a thinning ratio ranging from 5:1 to 2:1.
  5. Brush Selection: Select a high-quality, clean brush suitable for the application. Most 6-12mm, horse-hair paint brushes work fine for conformal coating.
  6. Coating Application: Pour a small amount of the conformal coating material into a small container. Dip the brush into the material and apply an even coat to the surface. Avoid applying too much pressure, to prevent an uneven spread of material.
  7. Drying Time: Allow the coated assembly to air dry or follow the drying or curing time specifications provided by the coating manufacturer.
  8. Inspection: After the coating has dried or cured, examine the assembly for defects such as bubbles, runs, or uneven coating.
  9. Masking Removal: Carefully remove the masking materials to expose the protected areas.


Best Practices


  • Always use a new brush for each application.
  • Pour the coating material into a small container rather than using it directly from the original container. This will reduce the risk of contamination.
  • Use smooth, controlled brush strokes to ensure uniform coverage.
  • Apply the coating in a well-ventilated area.
  • Ensure the coating material is at the right viscosity for brushing. Viscosity has a relevant impact on both ease of application and coating thickness.


At Conro Electronics, we’ll show you how to improve product reliability while increasing performance and lowering costs. Our team of technical support specialists will provide your company with dependable global supply, unrivalled efficiency, and superior technical support.

Feel free to contact us on 0208 953 1211 or send us an email to

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