For the vias, I'd suggest to make the via hole a really tight fit. Then, it
becomes more difficult to put the wire in the hole, but the wire does not
slide all the way to one side, and the results become consistent.
I've experienced the pads lifting issue myself and it's usually because the
drill is not sharp enough, like you said. I've thought about the 3-corner
registration method you've mentioned, but I was not sure I could get it to
work accurately enough. But now suddenly it seems like a good idea... :)
Probably much better than fiddling with printout scale factors to get a good
match. I might try it next time.
On Tue, May 11, 2010 at 4:46 PM, Kerry Wentworth <
kwentworth@...> wrote:
>
>
> 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/.<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.
> >
>
>
>
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