PCB Insulation

Hi all,

I regularaly design and build my own LED drivers (normally using 7135s for ease of design and common parts). Anyway my latest "batch" have an annoying flaw in which one of the through hole vias for LED- is shorting on the ground trace underneath the AMC chips. It's frustrating because the via is not actually under the chip, but is just large enough to short. There are 2 per board. I could just leave those chips off but the loss in power makes the boards not suitable for my application.

So instead of throwing $30 in PCBs down the drain and waiting another month for reworked boards to arrive, is there anything I can use to "seal" the culprit via? Insulate it from the underside of the AMC chip.

Whatever I use needs to hold together during AMC reflow. I was thinking 2 part arctic silver epoxy (the stuff we use to glue LED MCPCBs down) as this is not conductive and should hold together when I reflow the chip.

Any other/better solutions?

Thanks,

- Matt

You can try solder resist repair varnish, sometimes available on ebay. If it doesn’t need to be pretty you could even cover the via with a capton tape cutout and compensate the height with more soldering paste.

The UV solder mask from ali express works really well. It’s available in a small syringe if don’t need much.

Yeah I think Kapton tape will be the way to go. THat being said I found this:

http://www.jaycar.com.au/productView.asp?ID=NM2832

That might do the trick too....they have smaller tubes for less as well.

I'll check out the UV stuff as well though I'm hoping for a workable solution today lol.