cnc for PCB work

[threepointone]

I will be needing some sort of automated system for etching PCBs--I've had enough with the toner transfer method, and I really need something more reliable. However, I'm also on a pretty tight budget, so I need a bit of assistance in weighing my options.

First of all, how much would a PCB router capable of routing traces down to maybe about <.005" cost? Would it also be capable of drilling holes in a PCB?

If that turns out to be more than I'm willing to spend, I might also try the direct-to-board etch resist printing method. I'm still trying to find out the trace tolerance using this method, however. The thing is, I'd still like to have some way of drilling the holes into a PCB; what's the are the cheaper CNC solutions for that, and what kind of tolerances should I expect?

Thanks for the help!

[Torchhead]

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.

[pminmo]

While it doesn't need to be big and not much power, tolerances for pcb milling can bite you. For you tolerances you need a good spindle that has very little runout. You also need a tight leadscrew with minimal backlash. 5mils of backlash will kill fine traces. You actually can build a machine with off the shelf stuff, mdf, 1/4-20 screws, drawerslides or rollerbearings, it just needs to have the slop eliminated. Put your money in a spindle motor.

[threepointone]

I had a feeling the mechanical part wasn't so easy with CNC.

Anyway, I came across an amazing project here at cnczone--
http://cnczone.com/forums/showthread...=30951&page=33
direct to pcb etch resist printing! Apparently this can get up to 3mils resolution easy, and is much easier to do than toner transfer (at least imo). I'm almost certain I'm going for this method.

Thanks for the help anyway.

[pminmo]

Yes, that is a good thread. If I didn't have mill capabilities already I might hack one, but not at this point.