It seems like Dykem metal marking fluid (aka Machinist's Bluing or layout fluid) would be a better coating as it is meant to be scratched off without coming off in big flakes.
For those who don't know what it is, it is a laquer based blue or black paint in a spray or brush-on form. Painted on metal, then lines to cut and machine may be scratched in very accurately without scratching the metal itself.
This is beginning to sound a lot like the Scratch 'n Etch idea that John Kleinbauer came up with when the list was young.
Here's the thread:
http://tech.groups.yahoo.com/group/Homebrew_PCBs/message/259An early test by Brian Schmalz using Eagle PCB:
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http://tech.groups.yahoo.com/group/Homebrew_PCBs/files/Scratch_And_Etch/>
I did a few tests running an old HP plotter manually, I found it is very important to let the Dykem metal marking fluid dry completely to get a clean scratch line.
There are carbide scribers, and diamond-tipped scribers. This could be done with a very light-duty CNC machine or old flatbed paper/pen plotter. I dumped some lead shot into a pen with a carbide tip mounted in it to get enough pressure, it doesn't take much as the metal marking fluid is designed specifically so you don't have to press very hard.
Steve Greenfield AE7HD
--- In Homebrew_PCBs@yahoogroups.com, "Jeff" <jeff.heiss@...> wrote:
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> To follow up on the "Electrical Discharge Machining plus painted board plus CNC x-y table" discussion, I would like to suggest a similar idea. What do you think of spraying a PCB with automotive spray paint and using a water jet to remove the paint. After removing the paint, the board is etched. Electric pressure washers produce 1800 psi. Hypodermic needles are available in .004". Do you think there would be enough pressure out of a .004" opening to remove the coating on the board?
>
> Jeff
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