Jeff:
Despite all the advice you may get, there is really only one
proper way to remove excess flux. It is a long, drawn out process
that requires a minimum of the following ingredients:
small horse-hair brush
small wire brush
isopropyl alcohol (100%)
100 proof vodka (any brand)
small turkey baster
little leather pouch
butane lighter
a few toothpicks
several candles
You can find most of these items in your local hardware store and any
friendly kitchen supply store.
Place your PCB down on the counter with the trace side down. Examine
carefully all top-side components to check for those that are open
and could trap liquid. This might include such items as tuning cans,
pots, switches, connectors, and the like. Light one candle (using
the butane lighter), and let the wax drip into all these components.
This will keep the cleaning liquids from entering and possibly
ruining them. Beeswax candles are reputed to be the best for this use.
Now turn the board over and, in your mind, map out a small section
(approximately 1/20th) of the board for initial treatment. Some
experienced techs say that even smaller sections may be better. You
might start with a section that doesn't have too much excess flux,
just to get the procedure in hand in a spot of little consequence.
Using the small leather pouch, soak one corner with the alcohol and
place it into the candle flame (still burning). Let the corner char
slightly before blowing it out. Put a small amount of alcohol on the
horse-hair brush and swipe it back and forth over the burnt area of
the leather pouch to collect some of the carbonized char on its tip.
Brush this mixture onto the selected area, which has the unfortunate
side effect of making it somewhat darker and more difficult to see.
So, using the small wire brush, lightly pass it back and forth over
the area until the darkness is removed. A lighted magnifier is of
help here if you have one. If it doesn't come up right away, you
may rub a little harder. Break a toothpick in half and use the
ragged ends to clear the treated area of all residue to see if the
flux remains. If it does, use more pressure with the wire brush.
You are okay as long as you can still see remnants of the trace and/
or pads being treated.
Take a swig of the vodka and continue by darkening the next section.
Proceed, repeating all of the above steps, section by section, until
you have completed the entire board. Most people feel quite relaxed
about the process after completing five or six sections, and just
about everyone I know who has tried this is thoroughly satisfied when
finished.
I have still never figured out exactly what the Turkey baster is for,
but perhaps it is simply a symbolic souvenir for those who don't
simply leave the excess flux alone.
best wishes,
david belsley, w1euy
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