I didn't mean cutting the board was a problem, rather it is cutting
the isolation traces with the router that was the problem. The laser
would solve it. Also, to address your concerns, I could reverse the steps:
paint the board
burn isolation traces with the laser on both sides
etch the board
put it back on the cnc
burn away over the pads, leaving the paint as a solder mask.
drill the board
With a small diode laser cutter you would be able to use a very
lightweight x/y table, no z axis needed, just turn the laser on and off.
I've been looking at diode lasers and appears that focusing them is
not so easily done because they exhibit astigmatism and the beams are
not round. In fact, some of them are square.
Mark
At 09:35 AM 1/1/2011, you wrote:
>There's two minor problems with that workflow from my experience:
>
>- I've found that drilling through the paint tends to drive it into
>the hole, and getting it out is a pain. If you don't/can't the
>paint out, soldering the thru-hole lead then ends up "washing" the
>paint out of the hole with the molten and pollutes the solder joint.
>
>- I'd be concerned, unwarranted or not, that by drilling through the
>mask, you'd risk a little undercutting (during etch) around the hole
>penetration. Probably a non-issue if you've got rings/pads of any
>size around the drill hole.
>
>As far as cutting being your biggest problem -- we just shear
>ours. It's kind of Neanderthal, but it works well enough for us.
>
>It seems like the paint would be a reasonable solder mask, and
>probably an even better surface to print on with, say, an open-faced inkjet.
>
>Our results with alignment are adequate as it stands. Having a
>jig with pegs and pre-drilled/marked boards, all going into the
>laser cutter sounds like a lot more effort than reward. If I were
>trying to push the process down to a primo 8mil/8mil one, then it'd
>probably be necessary though. As it is now, it would seem to at
>least double our workflow effort.
>
>-e
>
>--- In Homebrew_PCBs@yahoogroups.com, mlerman@... wrote:
> >
> > Two sided alignment has been solved by the people who do cnc
> routing of boards. They use aligmnet pins (or optical markings) on
> the Y axis and software to do all the work of alignment and
> isolating the traces. I think Eagle has a ULP for this, too. I have
> a cnc board router, and the biggest problem by far is the cutting -
> you have to change bits, they break, etc. So If I could use a laser
> to do the isolation I could:
> >
> > paint the board
> > burn isolation traces with the laser on both sides
> > drill the boad on the cnc
> > etch the board
> > put it back on the cnc to burn away over the pads, leaving the
> paint as a solder mask.
>
>
>
>
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