Which Conformal Coating Should You Use?
PCB assembly customers often ask us which conformal coating we recommend for their product.
I understand the question. You may assume that Henway keeps one preferred coating in stock, or that we have a standard chemistry we use on every assembly.
We don’t. And that is intentional.
The right conformal coating depends on the product, the environment in which it will operate, the expected temperature range, chemical exposure, moisture, required certifications, serviceability, and the manufacturing process used to apply and cure it. Conformal coatings are available in several chemistries, including acrylic, silicone, polyurethane, and epoxy, and the choice should be driven by the application rather than convenience.
For example, an acrylic coating may be a good fit when fast drying and future repair or rework are important. Acrylic coatings can be comparatively easy to remove, and some are designed specifically as fast-drying, reworkable protection for circuit boards.
A silicone coating may make more sense for a product that will experience a wider temperature range or needs a more flexible coating system. Depending on the specific product, silicone coatings may also use specialized curing processes.
Even two coatings from the same general chemistry family may perform differently. One acrylic may be selected because it is easy to repair, while another may be chosen for chemical resistance, abrasion resistance, optical clarity, etc. That is why choosing “an acrylic” is not quite enough. You still need to choose the right acrylic.
What I normally recommend
Rather than pretending that we are the chemical experts, I usually recommend that the customer speak directly with a conformal-coating manufacturer or application scientist at MG Chemicals or Ellsworth Adhesives.
These are people who spend their careers studying coating chemistry. They can ask the right questions about:
Operating temperature
Moisture and condensation
Salt spray or corrosive environments
Fuels, oils, cleaning agents, and other chemicals
Required coating thickness
Repair and rework
Production volume
Cure time and available equipment
Regulatory or UL requirements
A Henway engineer will often participate in that conversation to make sure the recommended material is practical for us to apply and cure.
So, what should you do?
If your PCB assembly needs conformal coating, send me a message.
Tell me a little about the product and where it will be used. I’ll recommend a few knowledgeable people to speak with, and someone from Henway can join the conversation to make sure the final recommendation works for both your application and our production process.
The idea is not to use whatever coating happens to be sitting on a shelf.
The goal is to set you up with the right coating for your product.