Re: Cleaning Solutions for PC Boards Advice

[mjmahon@aol.com (Michael J. Mahon)]

Linards Ticmanis wrote:

>Bryan Villados wrote:
>
>
>> I was reading a guy's technique for cleaning printed circuit boards of old
>> Apple II hardware. What he does is he takes the boards out of its cases,
>> soaks the boards into a solution of de-ionized water and alcohol, then
>blows
>> them dry with an air gun. Is this good advice? If so, what's the formula
>for
>> this (X parts de-ionized water to X parts of alcohol)? And how long do you
>> leave the board sitting?
>
>In my (albeit limited) experience, water is only needed if there is lots 
>of flux leftovers from soldering. For grime and dirt, cheap denatured 
>alcohol, some detergent, and an old toothbrush is the right mixture. 
>You'd want to remove socketed ICs first, especially if they have 
>stickers on them (e.g. EPROMs). This mixture shouldn't harm

All readily available alcohol products contain water--it is difficult and
expensive to remove completely.

Still, used sparingly (brushed on and wiped off) there should be no
problem, as long as only sealed components are involved.  Be very
careful of getting liquid solvents around switches, pots, or variable
capacitors, since they will mobilize contaminants and deposit them
where you don't want them inside the devices.  IC sockets are a
special case, since there is considerable friction when re-socketing
an IC which does a pretty good job of cleaning the contact surfaces.

You must have a different kind of flux where you live.  Here in the
USA virtually all electronic-grade solders use a rosin flux which is
virtually waterproof.  Since there should be no flux residue from a
professional wave-soldering, I assume that we're talking about flux
remaining from some "amateur" after-manufacture soldering, and
it should all be non-conductive rosin.  In the USA, the most common
water-soluble flux is ammonium chloride, which is _absolutely
verboten_ for anything electrical or electronic, since it is hygroscopic,
conductive when moist, and corrosive.  It's fine for gutters.  ;-)

It is unnecessary to remove rosin flux from finished work except
for esthetic considerations.  If it is to be cleaned, a professional
flux solvent should be used, and all the caveats above regarding
solvents and PC boards apply.

If you just want to make the board look better, just brush it with
a soft, dry brush, possibly with the use of air.  If you are trying
to clean off some contaminant, like peanut butter or dried Coke,
you'll have to go the solvent route, with an appropriate solvent
and/or detergent.  When the board appears clean, rinse the area
multiple times finishing with a couple of deionized water rinses.
You can hasten drying times by a final alcohol rinse (but try to
avoid the common "rubbing alcohol", which typically contains
some oil to prevent excessive drying of skin).

Final word:  don't do anything with liquids unless a) it's _really_
a mess and must be cleaned, or b) you are willing to make the
board non-functional or significantly less reliable.  Esthetics
are not a good enough reason to soak a board!  If you just
can't resist, use careful "spot" cleaning.

If it works, don't fix it!

-michael

 Email:  mjmahon@aol.com
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