I also use a CNC machine to drill holes. I have an old XY stage that
was given to me, and I built a Z stage that drives a Dremel. I'm using
Allegro chips, A3955 and A2919 and running the voltage at ~26V. I get
good torque and speed. I use the microstep feature to drop the current
when not moving, to 10-15%. Even with a light table, I was never able
to get the pattern to line up with the holes anywhere near as well as
you do. I wrote some software that allows me to jog to 3 corners of the
pattern and translate the hole coordinates to match, so now I transfer,
drill and etch. I'm getting much better results. My drills may not be
sharp enough, because if I etch then drill, the pad on the bottom tends
to lift. But they are tough. During debug, signals got mixed up, and
the XY stage took off while the drill was at the bottom, and it milled a
slot in the board rather than break. It was a .035 drill. ;)
I also like your via method. I tried it in a vise on a defective board,
and the first try was perfect! The 2nd and 3rd were less perfect, the
wire tend to push to one side of the board and all of the peening occurs
on one side only. It takes a bit of care to get both sides to peen over
adequately, but it can be done, and the results are worth it.
Kerry
Tolga Abaci wrote:
> Actually, there is another method that I've been experimenting with. It's
> based on toner transfer and a glass paint called Pebeo Vitrea 160.
>
> You can see some of the results I've obtained here:
> http://retromaster.wordpress.com/pcb-making/. Just go down to the soldermask
> section for the details.
>
> Also, be sure to check out the "Remaining Issues" section. The way it was
> applied on the board there, the soldermask is not very strong, as it came
> off in several places (it is still a lot better than a PCB without a
> soldermask). This is how it ended-up:
> http://retromaster.files.wordpress.com/2010/05/ufe-sdram-la.jpg
>
> I've experimented with the two-step cure idea mentioned there, and that
> seems to produce a much stronger soldermask that does not come off easily.
> I'll soon update the PCB with results of the improved process.
>