Using a Glowforge to make PCBs

DIY PCB creation usually starts with a piece of copper clad fiberglass or polyboard and the unwanted copper is etched away with a solution like Ferric Chloride.  In order to keep the parts of the copper you want (your circuit!), a "resist" must be applied.  The most common approach for DIYers is to print out a picture of the circuit using a laser printer, and heat transfer the toner to the copper.  Blondihacks has an excellent tutorial to do exactly this.  If you're interested in DIY PCB creation, I highly recommend reading that article.

However, we're going to explore using a way to use a glowforge to create highly detailed and easily repeatable resists.

Copper is effectively a mirror for the glowforge's laser, so we can't just cut away the copper with the glowforge.  Instead, the copper clad board is covered with spray paint and we use the glowforge's engrave setting to burn away the paint from areas we want the copper removed by the etchant.  This creates a very precise, consistent resist.  The steps are shown by the various boards in the picture above.

To do all of this, start with painting your copper clad board.  It usually takes a day or so for the paint to dry.

Most importantly, you need a design.  I did this design in Eagle.  They have a free version that limits the size of the board you can create, but mine fit just fine within the constraints of the free version.  Starting with the schematic:

And then the PCB layout.  There are many excellent tutorials on using Eagle, particularly those by Sparkfun.

Eagle has the ability to export the PCB to an image, but I've found the image resolution is relatively low.  Instead, print the design to pdf.  The image in the pdf will have around 600dpi.

The glowforge interface can take a png file, but for the best results, converting it to vector format as an SVG is preferred. The most difficult part of all this is keeping the correct scale.  The glowforge interface will scale up high dpi image files, apparently assuming 72dpi?  To convert this to SVG, I import it into Inkscape.  In Inkscape, select the imported png, then use Path -> Trace Bitmap to convert the png to svg.  After this is done, you'll have 2 versions of the image on the screen: the png and the svg.  Delete the png, and save the vectorized version as a 'Plain SVG' file.

At this point the resulting SVG file can be uploaded to glowforge.  

Continue to page 2!

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