[RE-wrenches] Mouse pee in the SW

[James Jefferson Jarvis]

On 8/16/2013 2:38 AM, Bill Loesch wrote:
>
> Dan, et al,
>
> Once the board has been cleaned sufficiently that the inverter is no
> longer operating intermittently and your "hope" has been realized, when
> would you apply a field conformal coating? Would you choose/recommend
> something better than Krylon clear spray?

While Dan's cleaning advice is good ... I would not bother with 
conformal coating.

In my experience, it is nearly impossible to get a board actually clean 
of mouse urine. It soaks into the fiberglass laminate. If you conformal 
coat it, the traces will be eaten from underneath anyhow.

I would bite the bullet and replace the board or the inverter. Otherwise 
resign yourself for supporting a board that will likely get sicker and 
sicker at the most inopportune times.

I've even run a mouse urine board through a water wash machine, like 
what is used during the assembly of printed wiring board, and it wasn't 
able to get the mouse urine washed away. The water wash machine has 
multiple stages of washing and the appropriate chemicals ... but it 
couldn't get the soaked material out of the fiberglass.

re: conformal

I would use a purpose made conformal coating. McMaster-Carr stocks a 
silicone coating (6801A37) and a acrylic (6801A39) coating. Or Mouser 
carries Tech-Spray brand coatings.

I would further look for a conformal coating that can be removed or 
reworked through. Most conformal coatings cannot. Given he situation, I 
suspect that the board will require future attention and that calls for 
a coating that you can remove or rework through. Especially with the 
silicone conformal coating, it is almost impossible to remove or rework 
through.

For what it is worth and Good luck,


-- 
-James Jefferson Jarvis
APRS World, LLC
+1-507-454-2727
www.aprsworld.com