These water-soluble fluxes MUST be completely removed. The residue itself
is slightly conductive, enough to make analog circuits very unreliable. In
addition, the continued etching action eventually will dissolve any metal
on the board. I have seen boards that looked like Jack Frost made a visit,
covered with metallic oxides where there used to be IC pins and board
traces. The usual way to clean small quantities of these boards is to run
them through several full cycles in a dishwasher (no detergent). Even
then, sensitive analog boards may not be clean enough.
BTW, denatured alcohol is mostly water.
Mike K1MG
> For the past year or so I've been using Kester 63/37 organic core solder
which
> defluxes with water. The flux is more aggressive that the stuff I used
to use
> and it always wets out. On the NC38S, I had to deflux the component side
of
> the board as well as the solder side, especially around the 74HC240. It
cured
> most of the transmit instability that required frequent readjustment of
the
> trimmer cap in the transmit section. Denatured alchohol was used instead
of
> water because I didn't want to put water near the trimmer caps.
Compressed air
> and a hair dryer were used to eliminate the denatured alchohol. Since the
> instability got worse with time, I wonder if the minute amount of water
soluble
> flux on the component side was absorbing moisture from the air. Has
anyone
> else had any experience with this?
>
> 73, Rich, N3SLR, Baltimore, MD
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