Enlighten a total novice

[Grant Richter]

OK, my $0.02

> 
> 
> I'm with Tony on this one.  I cannot comprehend having to use a solder 
> that MUST have its flux cleaned every 5 minutes or it will start 
> corroding everything it is touching!  Talk about inconvenience!  Like 
> I've mentioned before, I have +15-year-old synths in perfect working 
> condition that have a thick layer or rosin flux on the solder side.

The purpose of removing the flux is so the solder joints can be properly
inspected.

The water based fluxes are more aggressive than rosin. You do not have to
clean them every 5 minutes. If the flux is left on overnight, it will
convert
a bright finish solder joint to a dull finish. Since a dull looking solder
joint
is a clue for a "cold" solder joint, it makes inspecting your work more
difficult. Water alone is all that is required to remove water soluble
fluxes.
Just rinse the board under hot tap water for about 30 seconds.

Rosin fluxes are hydrophilic, that is to say they attract and hold
moisture from humidity in the air. If you do not remove the flux,
over time it will start to act like there is a 10-100 meg resistor between
each pin depending on the humidity.
This is specially true with integrators and sample and holds.

You can remove rosin flux very well with 91% isopropyl alcohol
which you can find at Walgreen's (in US). The danger is that it is
very flammable. Hidden pilot lights such as those on stoves and
water heaters can ignite it. This happened to two friends of mine.
Much hospital time was involved.

Note that rosin fluxed solder is still required for panel and point to
point wiring. The water based fluxes are just for PCB work.
Because they clean up so easily and safely.