Designing for Selective Robotic Conformal Coating Processing: Rule 13 “Sticking coatings to non stick silicones is a pain”
Applying silicone RTVs to circuit boards to provide support to components for long term reliability is fine. Just don’t do it before you apply a conformal coating to the surface unless the conformal coating itself is a silicone. Acrylic and urethane coatings do not stick to silicone. So, don’t try unless you want defects appearing.
If you call out silicone staking materials for ruggedisation purposes, use a silicone conformal coating. If you don’t want to use a silicone conformal coating, then use a urethane or epoxy staking compound.
The Rules for Selective Conformal Coating are straightforward. Follow them and you can save money and time in your application process. However, if the Rules are not followed, the resultant circuit board design can challenge even the most sophisticated conformal coating system and its operator to achieve the finish desired.
Click Designing Circuit Boards for Selective Robotic Conformal Coating for further Rules.