Maintaining proper thickness for silicone conformal coating is critical because it is applied very thick compared to other conformal coatings. If a coating is applied too thick, it may create excessive stresses on solder joints and components (particularly glass-bodied components). If a coating is applied too thin, it may not reach the optimum properties described on the Technical Data Sheet. For this reason, the IPC created the J-STD-001 to regulate and standardize the thickness that coatings are applied at. For silicones, the J-STD-001 calls out 0.00197 to 0.00827 in. Our operators strive to hit between .002” and .008” for silicone applications.
Parylene Coating Blog by Diamond-MT
Technology varies between the platforms and the valves but essentially they achieve the same result. The goal is to deposit coating where you want it, removing the issue of masking which is required in batch processing with dip or spray booths.