Flux removal question

[patchell]

Blandon Ray wrote:

> Actually a few questions, especially for those of you building the Mini Modular:
>
> After last night's round of soldering I sprayed the back of the board with some
> flux remover. When it dried, some of the clear plastic polystyrene capacitors had
> turned white on the outside. My questions are: first, is this likely to damage the
> caps themselves?

    Well, you probably did not damage them, but I would consider that a bad sign.

> Second, what else shouldn't I spray with flux remover?

    Pot's are something I try to avoid getting any sovent in.

> Finally,
> how important is it (generally speaking) to remove flux from analogue circuits?

    In my opinion, a bad cleaning job is worse than no cleaning job.  The flux will
cause leakage currents.  How much it affects the performance of a given circuit
depends on the current levels.  VCO's, VCF's, sample and holds can be canidates that
may require cleaning.  If the solvent ends up just distributing a thin film of flux on
the entire board, this could end up causing more problems than it is worth.

>
> I'm told it can cause problems related to current leaking around the board, but
> that's about all I know.
>
> Thanks in advance,
> blandon

    And if I may, I would like to take the oportunity to push Kester 331 organic flux
core solder.  I clean my boards with ordinary water and a tooth brush.  No nasty
chemicals and the boards come out squeaky clean.  Jameco sells this stuff (P/N 151474)
and I will tell you it is worth it.  However, be forwarned.  Only use this solder on
PC Boards, and clean them whenever you are done for the day.  You do not want to leave
this flux on the board.  And do not use it for point to point wiring.  The flux will
go up under wire insulation where you can't clean and the wires will corrode.  And if
you do have to solder something on the board with Rosin Flux, make sure to clean all
of the organic flux off the board before doing so.  Mixing the Organic Flux with Rosin
Flux will make a big mess that is very difficult to clean up.

-Jim
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