the iron is on the parts so long that they start to melt
What I don't understand is what exactly is melting here? About the only thing I've seen
that will actually melt is the plastic case of an Led.
I've not used lead-free solder, but here's my 2-cents into the pot.
1. use a damp sponge, and not a wet sponge. Squeeze out the excess water.
2. wipe the tip on the sponge after every few solder joints.
3. use a beveled tip and not a pointy tip, as the former has a nice flat surface and
will apply heat much better.
4. I don't know about heat levels, but my temperature-controlled station has a mark on
the dial that works great for standard 60/40 flux solder. Then I sometimes have to
adjust +/- from there for very small parts or larger parts, pcb-heatsinks, etc.
5. I never use extra flux, as the solder has rosin flux in the core already.
6. some parts, typically TO-220s, have an oxidation on the leads, and I usually scrape
this off with an exacto knife before soldernig.
7. be sure to tin the new solder tip, and also dab some solder on the tip after it's
warmed up at the beginning.
8. apply the tip to one side of the joint for a second or 2, and then touch the solder
to the other side of the joint so it flows across via surface tension. If the heat is
adjusted correctly, it won't take any longer than this.
9. it also helps to again dab a bit of solder on the tip before making a joint, after
the tip has been wiped clean.
10. for some reason, sometimes the pins on some DIP sockets don't take solder well, so
if I happen to have received such sockets, I toss them in the garbage right off.
