Wayne,

 Yes, the current plan is to "Glob" something onto the PCBs but if we could get it pre-stenciled on the PCB that would help. I would also like to get the board top side coated before the planar transformer cores are mounts. A "Glob" might get thick at spots, the core needs to go all the way through the PCB holes so it mounds with the ferrite end plate on the other side. A thick glob would screw up the mounting. I would really like to coat top and bottom sides of the PCB. I easily can support 2 or 3 mils on each side but the coating needs to be somewhat consistent. I have about 15mils to play with.

This was a PCB design with two off line supplies crammed into a small space. Then later I find out they need this 2500VAC test. So I cleared around internal traces, those are no problem. But on surfaces the worst case air breakdown is 188 mils. Things are just too crammed. A little insulation would go a long ways!

So I was wondering what other folks might be doing.

Thanks,
Bob K.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Friday, March 17, 2017 5:23 PM
To: [log in to unmask]
Subject: Re: [TN] Screen On Insulation

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.