Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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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




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Default Unusual pcb corrossion problem

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
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Default Unusual pcb corrossion problem

Paul Drahn wrote in message
...
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


I didn't think to check for PbF but more than likely. Another factor could
be fibre board pcb and some fibres cross the width of the board and then an
easier path for gas from batteries. Green tint lacquer, if not conformal
coating, over the board


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Default Unusual pcb corrossion problem

On 1/18/2012 1:04 AM, N_Cook wrote:
Paul wrote in message
...
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


I didn't think to check for PbF but more than likely. Another factor could
be fibre board pcb and some fibres cross the width of the board and then an
easier path for gas from batteries. Green tint lacquer, if not conformal
coating, over the board


I hope you meant FR4 fiberglass for the board when you wrote "fibre
board". If not, then I don't have a clue about how the board was
manufactured. Most circuit boards have a green solder mask layer with
writing on it showing, at least, the component id and perhaps a board
name and revision level. The solder mask is a very thin transparent
sheet of fiberglass that is laminated with the board. That is probably
what you are seeing.

Paul
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Default Unusual pcb corrossion problem

On Wed, 18 Jan 2012 09:04:56 -0000, "N_Cook" wrote:

Paul Drahn wrote in message
...
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


I didn't think to check for PbF but more than likely. Another factor could
be fibre board pcb and some fibres cross the width of the board and then an
easier path for gas from batteries. Green tint lacquer, if not conformal
coating, over the board


Sounds like the now common solder mask, far lower cost the older conformal
coating (usually applied after board assembly).

?-)
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