Negative Laser Etching

[James] has been refining a method of negatively etching metal with a laser. He had been using a product called Thermark which is designed for this process, but it’s quite expensive. He found that paint designed for wood stoves works just as well. To prepare the surface he bead blasted it and then cleaned of the residue and finger prints off with acetone. The board was preheated in an oven before covering it with the spray paint. He ran the laser at 98/100 power and 90/400 speed at a step size of 0.1mm to achieve the results above. This should immediately make you think about making circuit boards. We’d love to ditch the toner transfer and we’re always looking for one more reason to get a laser cutter.

23 thoughts on “Negative Laser Etching

  1. Oi! Don’t give spoilers for my next project! :D Laser etched then chem-etched circuit boards may be right after the shaft encoder.

    Thanks for the feature! I updated the laser cutter speed to 300 after you wrote your post, it gives a shinier result!

  2. I’ve used toner from a copying machine to achieve similar results to Thermark. Simply lift the cover of the machine, hit copy, and it prints out a sheet of toner. Put the paper toner-side-down on the surface to be marked. Then, laser mark the back of the paper at low power levels, and it burns the toner onto the surface. I did this on clear plastics when I ran out of Thermark.

  3. I’ve done this many many times. Standard store bought spray paint doesn’t work very well since it leaves a slight residue that cannot be taken off consistently without damaging traces.

    I have actually experimented with every brand I could get my hands on (something like 10 to 15 separate brands). The one that seems to work the best is “Rustoleum Painters Touch 2xCoverage” brand. You also get far better results if you a) fire the laser when the paint is under water (doesn’t form as much residue) , b) paint two or more coats on the surface (residue can be taken off without damaging the traces).

  4. What about using other materials for coating? Toner was mentioned, but what about, say, the plastic used for powder-coating?

    I’ve even thought about using wax. It’s not as easy to put on, but it might leave less residue. Making a spin-coater like they use in the CD-pressing and semiconductor fabbing industries might be worth a try… And if you did, you could try all manner of liquids, paints, etc.

    I just thought of something crazy: use liquid clay (aka “slip”) and use the laser to form a ceramic resist!

  5. Cermark is expensive. However it does not provide the effect above. What cermark does it is it goes on to your metal (a slight green tint) and then once you laser it it leaves the black on the metal. What he did was spray paint the WHOLE object then remove the paint. Not the best idea say if you wanted to just do a few lines of text on something metal.

    This is what I have been doing for a bit now.
    and here

    Black Car primer works the best for me.


  6. @Renee – The terms make it a little confusing. Laser etching removes the paint and leaves exposed metal. Chemical etching then removes the exposed metal, leaving the metal covered by the paint, which are the PCB tracks. Wash off the paint with acetone and you have a PCB!

  7. @renee and @James
    reneee.. James nailed it. So your exposed metal is then coated in ferric chloride (or whatever) and its removed. I then use a dremmel with a soft wire brush + acetone.

    Here are exact process images:

    1. PCB lasered to reveal metal (black = traces)

    2. Chemically Etched. Paint still on.

    3. A PCB is born.

    Hope that helps.


  8. Just a crazy idea, but once etched…couldn’t you just leave most of the paint in place to protect the traces from corrosion, etc, i.e. just clean the pads you need to solder too? I think cleaning it all would be less time consuming, but if the paint can protect, it’d be an interesting project to etch a non-green PCB if you could find a contrasting paint color that works.

  9. Yup. You could. However I usually am too impatient to hit the 603, 403, smd component pads individually. I also thought about creating a new “mask” that once the board was etched I would place it back in the laser and just remove the pads with the laser. However alignment is hard to get right when you are working with such fine parts.


  10. So dump the TTS method of making PCB’s. I use MG Chemicals pre-sensitized board. They are exposed using regular fluorescent lamps so it’s really easy to make single and double sided boards simply by printing out the patterns on clear transparency sheets. Works great.

    Also, they make a Plated Through Hole kit for hobbyist!! I haven’t tried it out yet, but it’s a kit that sells for just under $200 I think.

    I could NEVER get the TTS method to work. As much as I tried, it’s just one of those things I could just never get quite right.

    Once I found the MG Chemicals boards, I never looked back. Use those, then tin plate the traces. Then spray it with that green acrylic paint. Use the TTS system to lay on a silk screen of components, and you end up with a VERY professional looking board. You can even get a small, cheap gold plate kit to do your own push buttons (like on a TV remote) or edge connectors.

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