The tin process is aggressive on soldermask and if the surface of a
PCB is not prep'd properly before applying the soldermask, the tin
process will show this. The tin process is not usually the culprit in
this case. It's the soldermask process.

On 10 Mar 2004 at 15:39, Morse, Carrie wrote:

We have some unpopulated bare boards that are white tin plated with
SMOBC.  The boards are exhibiting peeling mask at the interface between
the tin pad (TH and SMT) and the mask along the circuit runs.  Per
IPC
A610 , exposed copper is not acceptable in this case.  Can anyone
provide possible root causes to this phenomena?  The boards are
date
coded from Oct 2003 as well as Feb 2004.  Both lots exhibit the
exposed
copper/missing mask.  These boards were also stored in a
Temp/RH of
about 70F/10-15%RH

TIA
-Carrie

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