That screen printable peelable solder mask might work OK. It seems to stay stuck and have few pinholes. When printed in thin layers it is very difficult to remove.

But why not glob some 1-2577 over the area? Not screen printable, but if you were looking at doing a placement of a laser cut isolation then it probably is less overall effort. You don't say why the board didn't have slots cut into the right places, but slots are clearly the cheapest and most reliable solution.

Wayne Thayer

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Robert Kondner
Sent: Friday, March 17, 2017 1:11 PM
To: [log in to unmask]
Subject: [TN] Screen On Insulation

Hi,

 

We have a PCB that turns out to require 2500VAC test for 60 seconds and we had some flash over on pads to vias. We also have a planar ferrite transformer with primary windings on one side.

 

Does anyone know of a screen on insulation material that can be used to increase flash over voltages? I would like to get a 2 or 3 mils of material.
My other option is to have a laser cut layer of isolation but that could leave air paths under the material.

 

Any other ideas welcome. 

 

Thanks,

Bob K.