I am making a PCB with a subtractive PCB mill, and I am having difficulty soldering some components to the finished copper. The solder isn't flowing onto the traces easily, and by the time it does flow, the pad lifts.
I'm not sure if the boards need to be cleaned more, or if they need to be covered with a tinning solution (or both). What can I do to make the board easier to solder?
When should I clean my boards - just before or after milling?