Armed with new information gleaned from Mark Johnson of the printmaking studio at Steinhardt I began a new series of tests to determine the best combination of resist material, laser settings, and cleanup process for laser etching copper-clad boards to make circuits directly from digital plan files.
Printmakers use a process that is very similar to that required to etch circuit boards and involves a copper or zinc plate, ground (resist), and an acid etch solution. According to Mark, printmakers who have experimented with laser etching their print plates have settled on using heat-resistant enamel spray-paint to replace the traditional hand-worked ground on zinc and copper plates.
The two spray-paints I purchased for testing are:
- Majic - Rust Kill - Barbeque Black Spray Enamel - 8-2020
- Krylon - High Heat & Radiator - Black - 1614
I sprayed two small 3" x 3" plates with a thin coating of each enamel and let them dry. I then ran each through the laser to test for settings and determined the same value for each plate as follows. I decided to use the higher resolution raster density value of 6 to improve clarity.
| Lens | Image Density | Power | Speed | PPI | |
|---|---|---|---|---|---|
| Raster Etch | 2.0 | 6 | 3.8 | 10 | 1000 |
Each plate was then etched with a portion of a circuit plan file. Both plates looked very good after being etched but reacted very differently to being cleaned.
The Majic plate was easily cleaned using only soapy water, but the finish was very delicate and in some areas was removed even with just a light touch to the surface. Cleaning with alcohol was too strong and dissolved the paint entirely. To be as delicate as possible I soaked the plate in soapy water and then lightly washed the surface using a q-tip.
Here is the result of the cleaned Majic plate.
The Krylon plate however was not as easily cleaned. Below is the result after being washed with alcohol. A more through cleaning or a soaking in alcohol may help lift the fume from the surface of the plate.
And lastly the results after acid etching and removal of the resist using paint thinner. The Majics plate is clearly superior but still there are a few places on the plate where the fume was not entirely removed and the copper channels are crossed. Also, the very it was very hard to remove the material from the very small holes and the end of the channels and thus a few were left filled with copper.
