Covering electronic printed circuit boards (PCBs) with protective coatings or silicones is a critical process in electronics manufacturing. It serves to protect sensitive electronic components from environmental factors such as moisture, dust, chemical vapors, or mechanical stress.
Types of coatings
Two common types of coatings are:
- Lacquer-based coatings (Conformal Coating)
These are often made of acrylic, polyurethane, or epoxy resins. They are applied in a thin layer (typically 25–250 µm) to the printed circuit board and provide a good barrier against moisture and contaminants. They are applied by spraying, dipping, or selective coating. Curing can be achieved thermally, via UV light, or chemically. - Silicone-based coatings
Silicones offer excellent flexibility, high temperature resistance (up to >200 °C), and good electrical insulation. They are particularly suitable for applications involving extreme temperature fluctuations or vibrations. Silicone coatings are usually thicker (up to 1 mm) and can also be sprayed or casting.
Advantages of the coating
- Protection against moisture, corrosion, and chemical exposure
- Improved electrical insulation
- Improved mechanical stability
- Extending the product’s service life
Challenges
- Selecting the appropriate coating material based on the application and environmental conditions
- Ensuring complete curing
- Ensuring rework capability
- Covering sensitive components or connectors before coating
Conclusion
Coating with lacquer or silicone is a critical step in protecting and ensuring the quality of electronic circuit boards. Choosing the right materials and applying them precisely are essential for the long-term functionality and reliability of the electronic assembly.
The example illustrates our Rehm Protecto XP V3 system, which is designed to dispense potting materials such as silicones as well as various coating materials. Fluorescent coatings are also used to enable visual inspection of the coated areas under UV light.
