I’ve been considering the best approach to making my circut boards with the Cricut Expression (aka FreeExpression).
The board design software I use is called Eagle Cad. It is free for small designs and can generate HPGL files that I can send to the Expression via my custom firmware.
First off, I’ll need a suitable pen that will produce ink which can survive the etching bath. The go-to marker for this purpose is the Sharpie ultra fine permanent marker.
However, in my past experience with this marker, the results were less than desirable. The copper under the ink will be pitted and can result in open connections on fine traces.
I’ve had much better luck with the Staedtler Lumocolor Fine Point Permanent Marker
These pens are pretty expensive too..
If you can’t find them at your Office Depot or Staples in the Pen/Markers section, look in the Drafting Supplies section. That’s where I found mine.
Do not buy the Staedtler Fine Pigment Ink Archival pens. They do not work at all. (See below).
I bought two sets of pens. The Staedtler Lumocor set of colored pens, and a set of four Staedtler Pigment Ink Archival pens. As a writing instrument, these archival pens are incredible. They write so fine, and the ink is acid free, waterproof, won’t smear or smudge. It’s awesome. As a PCB writing tool, forget it.
I grabbed a scrap board and used each pen to write the color name. Then I used each of the archival pens to write the point size.
Then I headed to the Ferric Chloride bath.
If you don’t want to use Ferric Chloride, read this article for a home made alternative.
After 45 minutes, had my results.
First observation: 45 minutes was too long 🙂 Probably somewhere between 30 and 45 minutes.
So, ranking the colored pens in order of preference:
The rest were unusable IMHO. Red used to work a few years ago. Seems they changed the formulation. I’m going to repeat this test using Acid/Peroxide mixture. Another alternative is Sodium Persulfate. I have some Ammonium Persulfate on hand, but it is hard to get the mixture right. Problem with both persulfates is that the mixture loses it’s strength over time, so letting it sit on a shelf for a couple of weeks it will be useless. Not as long lived as Ferric Chloride. The Acid/Peroxide mixture etches much faster though.
Be sure if you use acid/peroxide, do it out doors. My workshop is poorly ventilated so I can’t use that stuff indoors.
To be continued…