"Jeff Liebermann" wrote in message
...
"Arfa Daily" hath wroth:

Just as a matter of interest, I always remove rosin flux residues from
boards, using a proprietory flux remover from Electrolube. IMHO, post
soldering residues left on boards make the job look scrappy and
unprofessional.

http://en.wikipedia.org/wiki/Soldering
http://www.finishing.com/Library/flux.html
http://www.worldwideflood.com/ark/pitch/pitch.htm

Ignoring acid flux, the rosin fluxes come in two flavors. Water based
and those that require some solvent to remove. Water based fluxes can
allegedly be left on the board and will not eat the copper traces. The
inspiration for this was not to reduce cleanup costs, but because of
environmental and workplace regulations which proscribed the use of
chlorinated hydrocarbon solvents for board cleaning.

The problem is that water soluble fluxes require rather hot water to
remove properly. They're mostly used wave solder machines and not
hand soldering. However, we were using them on the production in
rework stations and of course, I ended up with a few rolls of the
stuff. That's when I discovered that if you leave the flux on the
board for more than a few days, it turns rock hard and no amount of
hot water will get rid of it. The residue is water soluable, but the
big lumps left in rework are not. I experimented with some household
cleaners and found the ammonia cleaner sorta works. It's often easier
to scrape the ossified flux off the board than to wash it as it's
quite brittle.

Another fun experiment was to make my own flux. I managed to
accidentally purchase a roll of solid core 63/37. No flux inside. I
could purchase a tub of Kester rosin solder paste, but that's too easy
and no fun. Rosin is just tree sap and I live in a forest with pine
trees and lots of sticky gooey sap. I just walk outside, scrape off
some pine sap, and I have instant rosin. I melted a big lump of the
stuff to clean it and boil off the volatiles, and voila, instant
sticky rosin flux.

When testing it, I found that the soldering iron was insufficient to
set the flux on fire, but did an adquate job of converting it into
noxious fumes. Rosin works by vaporizing into a cloud of inert smog,
which protects the tin and lead from oxidation. The soldered
connections were successful, but difficult to see under the carbonized
sticky mess. Removal required trichlorethane (auto brake cleaner) and
some elbow grease. Once cleaned, the connections looked quite shiny
and bright. Obviously, I missed a step in the production process, but
in general, it worked.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Ah ! See ... I knew there'd be someone out there that knew about the
chemistry of fluxes. Thanks for the info. Most interesting.

Arfa