Okay brainiac's, here's a stumper.
We are witnessing micro-etch attacking exposed
copper circuitry only on boards with gold tabs.
This occurs right at the copper to gold
demarcation point.
This only just started, within two
days.
No significant process changes have occurred.
(normal replenishments, all data looks nominal)
We first noticed it after we stripped off some
poor white tin for rework. When we inspected the boards before
the second trip through immersion tin, we saw
reduced circuits, some to the point of non-existing, pads etched away far beyond
anything the micro-etch should be capable of in the seconds we keep product in
this bath.
From our supplier, they believe the gold is
reacting with chemistry in the micro-etch bath??????
Has anyone else witnessed this? And how'd you
resolve it?
Thanks,
Franklin