What is Conformal Coating and Do I Need It?

FAQs about conformal coating

What is Conformal Coating?

Conformal coating is a non-conductive material that is typically sprayed onto a circuit board so that it covers electrical components, conforming to their shape and protecting them from harsh environments where water, humidity, and dust may be present.  Conformal coating is also used on circuit boards that, while may not be used in a harsh environment, do generate high voltages.  High-voltages on a circuit board are prone to generating arcs.  Arcs will damage a circuit board.  Conformal coating helps to suppress arcs.


Why is Conformal Coating needed?

Conformal coating is needed to protect electrical components from shorting out due to a buildup of moisture, dust, and other contaminants that would cause a conductive path to be created from one area of the circuit board to another.

You may have wondered why water can cause so much damage to electronics.  We need water to live.  Water is safe for the human body, so why is it so dangerous to electronics?  Electronics is damaged by water because it creates shorts on the board.  Just like you would never touch a powered circuit board with a steel wire, you should never expose a circuit board to moisture.


What are the types of conformal coating?

There are currently 5 kinds of conformal coating:

  • Acrylic
  • Silicone
  • Urethane
  • Epoxy
  • Paralyene

The most popular type of conformal coating is acrylic, followed by silicone.  There are advantages and disadvantages for each type of conformal coating.  Some conformal coatings are more easily applied than others; some are more water-resistant, others less so.  One type of conformal coating can be removed easily in case rework is needed; other types are very difficult to remove.

Silicone conformal coating is solventless, acrylic is not..  Solvents (like those in paint thinners) require special care to extract the fumes while working with it.


Pro and cons for acrylic and silicone conformal coating


Pros: high dielectric strength; easily removed.  An easy-to-remove coating is desirable in case rework needs to be done.

Cons: Not a good choice for applications where the circuit board will be in an environment where solvent vapors are present as the solvent would degrade the coating.


Pros: works very well across a very broad temperature range; due to its rubbery nature, it is a very good choice for high vibrations applications.

Cons: not abrasion resistant; difficult and time-consuming to remove.


Is one type of conformal coating better than another?
Which type of coating is better depends on the application.


Is conformal coating waterproof?
No.  If a circuit board needs to be used in environments where water submersion is possible, then the circuit board should be housed within a water-tight enclosure.


How is conformal coating applied?
Conformal coating can be applied by hand or by machine.  More accurate and consistent results are obtained by using a robotically controlled machine to apply conformal coating.  Here at Futaba we have machines to apply silicone and acrylic conformal coatings.