wrote in message
ups.com...
I don't do much soldering (obviously) but which is better and is less
prone to cracking in the future? The newer Lead-free rosin core or the
63/37 tin/lead rosin core? A store in my town only stocks these two.
This for a small circuit board repair project.

Also, What can I use to cleanup the dried-up rosin residue on the PCB?

Thanks


Unless you are working with circuits that have known lead-free solder on it,
go with the 63/37 rosin core. Usually it is more common to find a 60/40
rosin core, but either is fine with a slight preference to the 63/37. If
you look at a chart for the melting and cooling of the solder, you will see
that the 63/37 does not go into what is called a plastic state as it cools.
What that is , as the solder cools and if the joint is moved, the solder
will have a frosted look and will not make a very good joint. It will not
be shinny as it should look.

Never use the acid core for electronic work. The acid left behind will
absorb water from the air and eat away at the circuits. The acid flux is
mainly used for copper water pipes.