On 1/17/2012 12:46 AM, N_Cook wrote:
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




Five years old would mean it was assembled with lead-free solder. That
requires very active flux to get the solder to stick to the copper. The
board was not properly washed after assembly, so some of the flux is
still on the copper. That causes the "lumps" to form.

Conformal coating merely limits the moisture getting to the traces and
components, doesn't entirely eliminate it. I doubt your remote control
has conformal coating. It's expensive to apply.

I had a similar experience with an electric gate opener. The
antenna/receiver part is connected by wire to the main control box. The
whole system became erratic. I finally looked in the little
receiver/antenna box and found lots of white fuzz on parts of it's
circuit board. Carefully cleaned the board with IPA (isopropal alcohol)
and all worked properly, again. The board had not been cleaned after the
connecting wires were soldered to the board.

Paul