I have designed the layout of a PCB that will have an unique area with crimpage terminal connectors receiving 6KV by an external wire. I have done the shortest polygon (instead traces) for 9 PCB terminal connectors like these:
These 9 points must have the same potential. They (1+8) connect 6KV with 8 wires coming from contact relays (flying lead contacts). So doing this way, coil (low voltage) contacts can be separated from 6kV contacts (and 6 6KV polygon) using bigger distances. Finally, I will have a board with 24 HV relays so, 24 coils pads at 12V by one side of the board (middle), traces will go from them to the left corner of the board. HV polygon will be allocated at the right upper edge, with some slots (air gaps) that I made and adding more than the minimal distance that calculations give me using CTI0, conformal coating, etc.. (i.e.: minimal d + 50%(d))
I have read that using conformal coating distances can be minimized. So I use clearance and creepage at the PCB design that matches with conformal coating usage tables because my idea is to use conformal coating.
But I sincerely have never chosen conformal coatings neither worked with that. After searching I found that there are various types of products for several application cases. I see that acrylic solution has high dielectric. But I can see that there are many type of acrylic comercial solutions too.
The second chance is that there are several ways for applying the coating. From manual way until automatic one, depending on the number of PCB to produce. I think my case could fit with spraying. And it is said that this brings the need of doing kapton masks for the rest of the board.
So the question are two:
1.- Could anyone share with me commercial acryilic conformal coating solution for good isolation (max high voltage 6kV) of this design?
2.- Where exactly may I spray with solution over the board? Maybe over the HV connectors and HV polygon after wire connectors being connected/coupled to the crimpage board terminals? Maybe over the coil contacts, traces and pads? Maybe over the whole board after soldering all the components?
I have seen this one at farnell web that has 40Kv/mm:
Or this other one with 70Kv/mm and liquid (but says something about spray gun):