We don't want to hype this solder TOO much, but this could possibly be the best solder in the world. There, we've said it. This is a special blend made specifically for Sparkfun and we love it. It all started as a quest to find the best solder to use in the Sparkfun production process and ended up being the best we've tried. The best part is that it's lead free and has a water-soluble flux core.
This package contains ~6m (20 feet) of solder and has a diameter of 0.5mm (0.020").
Mix: 96.35% Sn (Tin), 3.0% Ag (Silver), 0.5% Cu (Copper), 0.15% Sb (Antimony).