I worked on avionics in the Marine Corps and to this day:

1. Use flux.
2. Use silver-bearing solder 62/36/2 being my favorite.
3. Always solder at about 775F, sometimes 800F.
4. Pre-flux all connections, then pre-tin, then dip in flux again and solder the connection with minimal additional solder.
5. Each iron to object connection time is less than 1/2 second.
6. 91% isopropyl alcohol cleans all flux residue squeaky clean.


ALL of my joints are hot (shiny) and ultra-strong.

Note, I use a Weller WES 51D station. Folks do a lot better buying a name-brand station / iron as opposed to re-badged 'RC' products.

http://www.amazon.com/Weller-WESD51-.../dp/B000ARU9PO