The copper on the boards I received was too oxidized to accept solder well. You cannot clean them with a Dremel tool as this will remove the solder mask between passes. Also, handling the whole board is more work than I need, so I resorted to ketchup. Ketchup is an old kitchen trick that makes it easy to clean the bottoms of copper-plated pots. No need to lubricate your elbows - just apply, leave on for 15-30 minutes, rinse off. It works on those cheap boards too, although on these I also do aβ¦