How to make an Eagle Solder Mask Stencil for an Laser Cutter

Posted by Ril3y on March 18, 2010

There is a hardware hacking class that qlabs is presenting over at hacdc. My friends over at theQlabs asked if I could whip up a solder mask stencil to aide with soldering the SMD portion of the GoodFet hardware they are using. I went ahead and did so.. I also took some screen shots to demo the process for everyone. So this is how I do this.

Everything you need to create a good solder mask is built right into EAGLE PCB. The first thing we do it download the goodfet21.zip EAGLE files. We open the BRD file (you might be able to use the GERBER files but this is how I do it) and Hide all layers.

Step 1

Hide the all of the layers. Then display only the Dimension and Tcream. (Note: in the screen shot its the document.. it needs to be Dimension). Also change the fill style for the cream layer. It is a “hatch” looking pattern by default. We want a solid color pattern. I left the color Grey. When we print the PDF it will turn it black anyways so it does not matter. Click ok.

Now you need to click Print and then click the PDF button. This is going to get us a vector format of the stencil. However, for some weird reason the PDF writer in EAGLE creates some sort of non-standard PDF (not sure exactly). This does not allow us to just import this into Corel Draw (corel is what the vector cutting drivers work for the epilog laser cutter).

So scroll down to see the next step.

Now you will need to download Ghostscript and Gview for your platform. Here is the windows links.
http://mirror.cs.wisc.edu/pub/mirrors/ghost/GPL/gs864/gs864w32.exe – Ghostview
http://mirror.cs.wisc.edu/pub/mirrors/ghost/ghostgum/gsv49w32.exe – Gview (Windows GUI for Ghost Script)

Ok once those are installed go ahead and open Gview and then open the PDF we created above.

Now click File >> Convert. Select the EPS Write and type in 1200 dpi. Then click OK and save it. You now have the file you will be loading into the epilog laser cutter.

Open up Corel draw… Ungroup everything (if needed) and check the outside lines for duplicates.. Meaning select a outer line and delete it… If you see another line.. Delete that one until the lines are no more.. Then just undo the last delete. Why do we do that? For some reason Ghostscript from time to time adds multiple lines on the outside.. Not sure why. But if we do not delete them we will have the laser cutter going over everything (at least the outter edges) 2x or 3x. Ok so you have removed all duplicated lines and now you are ready to select all and make the line width a “hairline” width. This is something that corel calls it. This is the #1 reason that you can only use Corel draw to do cuts (vector stuff) with the epilog. So anyhow.. Now you should print it out. Setup your desired epilog settings (based on your material) and have at it.

Your done! (DFX is here: Goodget 2.1 stencil dxf)

Tags: laser, Laser Cutter, laser cutting, pcb, smd, smt, solder mask, soldering, stencil

Comments (17)

obscurite

March 18th, 2010 13:26

Will be using this in Q’s class. Awesome results – thanks for working on this and publishing the howto!

Ril3y

March 18th, 2010 13:35

np!

Chris.W.Zeh@gmail.com

March 18th, 2010 15:20

That’s awesome! I’m jealous of your laser cutter. (and your whole workshop as well

(Fyi… it looks like you might have duplicated the first two paragraphs in your post).

March 18th, 2010 22:34

Awesome man! Added to our project page: goodfet.sourceforge.net – thanks again man, will help with the soldering process for my course.

ladyada

March 19th, 2010 14:33

Ril3y

March 19th, 2010 17:41

Cool, thx limor. I will have to check out your method. I know about kapton. However I found that for hardware classes I can use a heavy card stock and pump these out pretty cheap and they work pretty well for about 3 of 4 boards each.

Ril3y

WestfW

March 19th, 2010 18:07

It seems to me that you’re not making full use of the capabilities of EAGLE. For instance, using the CAM processor, you should be able to export tCream directly to EPS (though not in vector form), and EAGLE also has some ability to generate outlines of layers (though perhaps only signal layers.) And then there’s the possibility of creating a custom CAM output device (based on EPS) that would do outlines only. In general, if the goal is EPS or PS that contains only edges of the relevant layers, it seems like it ought to be possible to do it in a lot fewer steps… PM me if you want to experiment (I don’t have access or knowledge of the laser cutter.) (OTOH, you have something that works so perhaps it shouldn’t be messed with…)

DrLabel

March 19th, 2010 18:08

Hi can you send me your drawing in DXF for me to try it in my Watherjet pls..

DrLabel

Ril3y

March 19th, 2010 21:49

I attached the dfx file on the main post in a zip file.

WestfW

March 20th, 2010 03:14

This was bugging me, so I went further with it…
Try putting this at the end of your eagle.def file:

[laserstencil]

@EPS
Long = “Postscript with 0-length lines for laser cutter”
Header3 = “/b { %% draw a bar\n”\
” /an exch def\n”\
” /y2 exch def\n”\
” /x2 exch def\n”\
” /y1 exch def\n”\
” /x1 exch def\n”\
” /w2 x2 x1 sub 2 div EU def\n”\
” /h2 y2 y1 sub 2 div EU def\n”\
” gsave\n”\
” 0 setgray 0 setlinewidth\n”\
” x1 x2 add 2 div EU y1 y2 add 2 div EU translate\n”\
” an rotate\n”\
” newpath\n”\
” w2 h2 moveto\n”\
” w2 neg h2 lineto\n”\
” w2 neg h2 neg lineto\n”\
” w2 h2 neg lineto\n”\
” closepath stroke\n”\
” grestore\n”\
” } def\n”

DrLabel

March 20th, 2010 05:08

Tks

Ril3y

March 20th, 2010 09:17

WestfW I will go ahead and try it out. Once I place that in my def file what is the “action” that I need to do to get this script to execute?

ohararp

March 20th, 2010 09:54

Definitely, use .eps format option. You can use this format for either raster scan or vector cutting.

WestfW

March 20th, 2010 18:09

After patching eagle.def, use the CAM processor. Select tCream and Dimension layers, device “laserstencil”, appropriate output file, and click “process job.”
This of course can be saved as a “cam job” or added as an additional step to an existing cam job. And the CAM processor is EAGLE’s “dimension accurate” output mechanism, with no printer drivers to confuse things.

Scott Gilliland

March 21st, 2010 17:23

I’ve used a similar technique before, but I did one or two things differently:

1: It looks like you’re vector cutting the holes. I found that I had better precision when I raster cut the material. Something about the way that the epilog’s do corners in vector mode… they seem to slow down to take a turn, but don’t lower the laser power to match.

2: I gave up on paper-like material. I found that one or two layers of packing tape worked really well. The trick is that it needs to be stuck to a sheet of metal when you cut it, so that the metal absorbs much of the heat. Otherwise, you end up melting the tape completely. The packing tape was nice, as it stayed ‘stuck’ while you apply paste.

If you want to see pictures of what I did:
http://wiki.cc.gatech.edu/ccg/making/lfbgasolder

Curtis Ruck

March 21st, 2010 21:23

For my epilog laser needs i actually print straight from PDF. Adobe Reader seems to be able to print raw postscript. In my svg files that I use as inputs I just specify the “0.001in” or 0.072 points for line width to do a vector cut.

Ril3y

March 21st, 2010 21:25

@Curtis:
Wow that works? I have yet to be able (granted I tried in inkscape) to get anything to print vector cuts outside of corel. Do you have a blog on how you are doing it? I would love to read it

Ril3y

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