The alternatives to conformal coating
Co-Authors and contributors
- Dr Lee Hitchens, Nexus
Many resins and coatings are designed to protect a circuit board. Not all of them are conformal coatings or Parylene.
Many coatings can be used to improve electrical insulation, provide environmental protection from moisture, water and chemicals and prevent mechanical damage from thermal shock and vibration.
These coating types can be categorised as follows:
- Conformal coatings
- Potting Compounds
- Casting Compounds
How these names are defined and differentiated in the industry is normally by the thickness of the coating applied and the ability of the coating to perform at that required thickness.
Conformal Coatings generally are applied as thin films.
Typical thicknesses are in the range of 25-150um although this can vary across the circuit board and the material type.
They do not generally perform better when applied at a greater thickness. In fact, performance may deteriorate if applied too thick.
Encapsulation is the application of a thick film coating.
This is where the thick coating completely surrounds the unit and can be in order of 100’s of microns up to a few millimetres of coating.
A moulded device is a normally described as an encapsulated unit.
A potting compound implies an extremely thick coating. The coating tends to be much thicker than a few millimetres.
The potting method uses a “pot” or case or shell to put the device in and then pour the liquid potting compound to the top of the case covering the device and completely encasing it.
The case becomes part of the finished unit. This is the most common method used, especially for high speed and many-units-per-hour production-line conditions.
The casting method is the same idea but instead of a case that stays part of the unit, a mold is use and removed after the potting compound has hardened.
Sometimes this is also referred to as encapsulation. This is used when a moulded unit is desired.