Wolfmans Howlings

How to create a PCB with a K40 Laser cutter

Posted by Jim Morris on Thu Aug 30 09:35:20 -0700 2018

I have tried the various techniques for creating PCBs on a laser cutter (both a 3w led and K40 CO2). The issue was the paint would leave a residue on the PCB after being lasered, and removing it proved to be hard to impossible. Using the toothbrush approach it didn't touch it, and using IPA it took off the thinner traces too.

So I came up with an alternative.

Cover the PCB with blue painters tape, create a negative of the PCB using one of the many techniques described by others, I create the PCB in Eagle, then create an image and use Lightburn to create a negative raster.

By negative I mean the traces are lasered and the rest is not, it is the reverse of what you would do if you were to try to laser the painted copper directly.

I am basically creating a stencil of the traces directly on the PCB.

I laser this at 10mA and 100mm/sec feed rate. The blue tape is obliterated and leaves no residue.

Then spray the black paint on the PCB which deposits a nice thick paint layer directly on the traces.

When the paint is dry remove the blue painters tape and etch as normal.

If the traces are close together removing the painters tape can be tricky, so an alternative is instead of spraying the stencil, use a thick etch resist pen and just fill in the traces, this makes it easier to see and remove the painters tape once the resist is dried.

Of course YMMV.