Good Morning,

We usually require soldermask over bare copper and tented vias (less than 
.020").  This typically means that the soldermask is dry film.  If a tented 
via is not required and liquid soldermask is used, it appears that the 
soldermask is suspect to flake off near the via knee, leaving a small amount 
of exposed copper.

Is liquid solder mask over bare copper compliant with vias when the plating 
is eletroless nickel - immersion gold?

Does the plating type matter?

Is the suspect of exposed copper a non-issue?

Thank you in advance of any comments.

Kevin Thorson
Lockhead Martin
Eagan, Mn