Galileo question - laser solder mask?

This is for Paul and the other LAZZOR yodas,

We just got notice that the batch of nine Galileo custom circuit
boards are made and have shipped. We expect to have them in-hand to
bring to the next Tuesday meeting for show-and-tell.

It is time to start thinking about soldering the surface-mount

DaveB mentioned the possibility of laser cutting a solder stencil mask
out of some (?) material. It would be way cool to do that. We would
need to make the DXF file and get the stencil mask material.

Any inputs and interest in making this come together between now and


That’s a good idea. I’ve never tried using a soldermask but it would be cool to see.

Adafruit has a guide for creating laser cut SMT stencils, I have only glanced over it so far.

Ah ha... Adafruit comes through again. Good link!

So we need something like Kapton film, 2 mil thick 1 ft square sheets
from McMaster-Carr
and solder paste such as Kester No-Clean

Did you see the note about shrinking the graphics? If you track the
laser to cut-out a rectangular solder pad in the stencil material, the
laser beam tracks on the center of the rectangular path and leaves a
burned-out "kerf" that is slightly wider outside (and inside) the
rectangular path. The rectangular cutout ends up oversize and the
"chad" is undersize by the laser kerf width.

The pads are pretty small to start with, and the kurf cutting acrylic
is something like .010" wide (I believe) so this is an important step.

Any EagleCAD yodas know how to get a shrunk solder mask laser cutting
file easily?


We have the solder paste…

Just how many parts on these boards, and how many boards? passives as well, or just the controllers?

As I remember, the griddle reflow we did for the stepper drivers didn’t need a mask, we just ran a bead of paste down each side of the part and it came together very nicely.

masks are so nice…

The link Paul sent makes it look like masks are easy to do - sounds like a plan to me.

Do we have a McMaster order going in already?

I’ve used transparencies from office depot previously.

Yeah, I’ll vote for the Office Depot transparencies, the Kapton film is $$$.


I have a nearly-full box of Office Depot transparencies I can offer
for the cause (perhaps I'll restore the balance after all the
transparency sheets I appropriated from Dave Menninger so I could
print negatives to expose cyanotypes with).

awesome, Hodapp!

So how much work is it to make the CAD artwork for the appropriately
shrunk solder pads for the Galileo boards? I still don't have the
boards yet, but they are supposedly in the mail.