🚀 go-pugleaf

>In article <422@ctycal.UUCP> ingoldsb@ctycal.COM (Terry Ingoldsby) writes:
>Having been an electronics hobbiest for some years, I am going to ask
>what is probably a *dumb* question.  I have seen all the discussion
>about methods of removing rosin from PC boards, but I've never had
>any trouble with leaving it there.  My understanding is that it is
>an insulator.  Is this not true?  Does it have some high frequency
>characteristics that I've never run into?  Do people just dislike
>how it looks?

Terry,

One of the absolute best solvents for most fluxes is 100% ethanol.  This
is available at your friendly liquor store as PGA (pure grain alcohol).
I've found that not only does this stuff remove roson rather well, it
leave no residue.  I've tried other alcohols and dilute ethanol and none
seem to work as well.  The water seems to interefer with the solvent 
effects.  

My procedure is to first, before doing the repair, wash the area in 
Clorothane (1,1,1 tricloroethane) to remove any conformal coating that
may be present.  1,1,1 won't remove the silicone or epoxy conformal
coatings but these are not seen too much in commercial gear.  Next do
the repair work.  Then, with the board horizontal, soak the area in
ethanol and scrub with an acid brush (a cheap organic bristle brush 
so named because it was designed to apply acid for soldering sheet metal.
Obtain at hardware store).  The flux will appear to disappear but will
actually be in solution.  If you stop there, your board will dry with a
white, powdery film.  Hold the board vertical and hose the board thoroughly
with ethanol.  I use a lab wash bottle for the task.  This will flush the
board of the flux-laden fluid.  Dry with a hair dryer or oven.  I suggest
a light conformal coating of Krylon crystal clear spray for non-critical
boards and whatever the mfr. recommends for critical ones.

I've used this technique for years in repairing even very sensitive 
nuclear instrumentation boards where no surface conductance at all is
tolerated (resistors with >10E10 ohms are common).

One final note.  Don't get fooled at the liquor store into getting
196 proof votka.  The 2% water content will foul up the process.  The last
time I bought some, I got the Absolut brand (russian, I think) which was
the only thing they had.

I've found that this works better than any of the freon or freon-alcohol
mixes that are so expensive.  Besides, if you get in a real mess, you
can "deflux" the old stomach :-)

John

-- 
John De Armond, WD4OQC                     | Manual? ... What manual ?!? 
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