Conformal coating is a protective coating or polymer film that “conforms” to the circuit board’s inherent irregularities to protect electronic circuits from harsh environments. Conformal coatings are a breathable protective layer that protects a printed circuit assembly from its exposed environment by filtering out airborne contaminants and maintaining long-term surface insulation resistance. Entrapped moisture, however, is allowed to escape.
With the wide range of coating chemistries and equipment options available, your application may seem hard to define. Clearly defining answers to the four key points listed below will help start the process of creating your solution.
Understand the Coating Chemistry
The first step to defining your solution is to understand the properties of your chemistry such as:
- Base chemistry
- Composition – solvent based or 100% solids
- Viscosity
- Thickness limitations
- Material reservoir options
- Dilution requirements and/or curing requirements, if necessary
Define Coating Requirements
Clearly define the requirements of your coating application by outlining key factors such as must coat/no coat areas, target thickness, distance from keep out zones, throughput requirements, and if coating will be required on both sides of the substrate.
Choose Application Method
To choose the best application method for your solution, confirm that the applicator can reach all areas (spray valves are best for a thin film whereas needle or jet valves are best for detail or hard to reach areas) and if a gel or masking step is required.
Define Automation Required
The final step to creating your conformal coating solution is to define your automation requirements. This can be achieved by answering the following:
- What is the required number of robot axes?
- How large is the required work area?
- What type of handling is needed – manual or conveyorized?
- Are carrier pallets required?
- Are there any additional process control options required (flow monitor, pumps, etc.)?
- What is the target throughput?
Examples of PVA’s common conformal coating line configurations are listed below.
