If there is peeling/flaking after they have performed all cure cycles/steps
then I would suspect the reliability of the mask.

Under/over developing in itself is not a major concern in my opinion;
however, if it has removed so much of the mask in fine areas where it
affects adherence of the mask to the board then this leaves the possibility
of mask lifting at some point in the future, this lifting mask may
potentially entrap contaminates thus presenting additional reliability
issues.

Franklin

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kevin Glidden
Sent: Tuesday, September 26, 2006 11:26 AM
To: [log in to unmask]
Subject: [TN] Over-developed Soldermask

Question for the PCB fabricators...

One of our PCB suppliers is asking us to accept PCBs with a "minor" issue.
The problem is described as this: The panels were under-developed and some
residual solder mask was left over.  To eliminate this, the panels were put
through a second pass to ensure all residual solder mask was removed.  The
result is some overdevelopment of the solder mask.  Then, this apparently
resulted in an "undercut" along the demarcation lines.  They say during a
tape test, very small traces of mask from the undercuts comes off.  The mask
is still present between all features and is adhered to the PCB.   But, it
is over-developed and has undercuts.  They say that while it does not pass
the tape adhesion test, it is of no detriment to the PCB quality or
performance.

My question is if over-developed soldermask maintains the same properties as
normally developed soldermask?  When I asked about this, they said the
properties of the mask are determined by the initial (pre-developing) cure
and the final (post-developing cure), and the over-development does not
affect the properties.  True?

In case "it depends", these PCBs are used in avionics power supplies.

Thanks in advance!

Kevin

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