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N_Cook N_Cook is offline
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Default Unusual pcb corrossion problem

Remote control about 5 years old, no spillages or abuse. I don't know how
they make the pcbs , perhaps something like this. Conformal coating over pcb
and tracks, etched back around the button pads or some other process and
then laying down the black resistive-conductive tracks.
1mm or so green/blue lump (copper sulphate/carbonate?) in one of these
"guard" rings around a pad and neat hole in a track under. Another such lump
, similarly placed, but copper not etched through under. Both lumps at the
battery end so perhaps outgasing from batteries rather than air pollution.
But battery box on the other side of pcb