Or if you have good control over the laser wavelength, separate out elements and even isotopes. It's power-intensive, but you could convert an asteroid into amazingly pure ingots all of the same isotope.

Alpha emission from the solder in electronic assemblies is already a source of single-bit errors, now that transistor sizes are getting so small. There's already a market for isotopically-pure laser-separated Pb for electronics assembly (100x the price of regular Pb); future server rooms might have racks and wiring made of isotopically-pure metals, and be surrounded by metres of isotopically-pure shielding.

http://en.wikipedia.org/wiki/Isotope_separation#Laser


Also, refer to "Lead-Free Soldering and Low Alpha Solders for Wafer Level Interconnects", by Dr. Ning-Cheng Lee, Indium Corporation of America.