The problem with routing PCB's is that the router tool itself will be hard pressed to cut .005 wide traces. The most typical bit is a 45 deg V bit. The board you are routing will have to be PERFECTLY level so the depth of the cut does not vary more than .001. Even then you can count on having a furrow of about .010 wide on each side of the runs. You can with the right equipment cut a board that has runs passing between .1 " spaced IC pins. I cut protos all the time but make my runs 20 mils wide and use a 15 mil offset on the cutter. I am careful on the layout not to let a bunch of runs get closer than 20 mils apart.
I fashioned a floating head and a depth controller that works like the nose piece on vinyl cutters. I used the end off a cheap solder sucker and run the V cutter down through it. The nylon nosepiece rides on the material and controls the depth of cut.
Chemical etching is still the most accurate way to go. The CNC machine can save a lot of time by drilling the hundreds of holes in a design.