Lou;  We don't run a large quantity of cca's through our machine, but with pwb's
solder masked over tin/lead, we don't see much movement in the copper reading.
Always around .075%
I find it wise  every so often to do several tests at an independant lab on the
solder from the bath, and in several cases on the bar stock received, which is
to the QQ-P spec.
One phenon. I find strange is the need to add tin fairly regularly, we can drop
1% in a short time, with very little soldering being processed. Less than 100
6x8 " boards.
Your case may have to do with the use of bare copper runs, even with smobc.
   Ernie Crump

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