Be sure to keep an eye out in low-level areas like in Dromund Kaas for level 13-15 droids who are not red or green, but yellow. They usually are strong droids, and yield Desh/Silica in the first area or two, but soon switch to Aluminium/Laminoid. They're also pretty easy to kill. There are also a few nodes around the dark temple area, too, but it takes a bit of running around to find them all. Hope this helps!