• The Etch

    baaskaas • 04/28/2019 at 15:15 • 1 comment

    Soo here it goes!

    What i basically did was spray painting a normal piece of single side copper pcb. To start etching with it, i tought what if i would burn the spray paint of at the places where i would want the copper removed by the etching chemicals. 

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    Phase 1(Design to Gcode)
    My design i created in kicad, went trough FlatCAM for the GCode, and i replaced all the parts where the laser should go on with that command (basically, when the Z axis goes down, i remove the line and insert a M4 S1000 line) Next when i need the laser to turn off, i replaced the parts where z-axis should go up with M5 S0.

    after some tests on some MDF and plywood i was ready for Phase 2 

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    Phase 2(Laser engraving the spraypaint)

    So the first time i basically placed the pcb with matt black paint directly under the laser, and even though the engraving of the laser on the paint was viewable, it barely reached the copper. I knew this was going to happen, i just wanted to know what was going to happen if i did. So even if the copper is just 35um thick, it is flowing away the heath of the laser easily so the paint can not really burn trough to the copper. 

    After doing a lot of passes and very slow passes which wouldn't work i put the project on hold about 3 months ago. Then i saw on Aliexpress that a 3D printer heath-bed is extremely cheap. I ordered one, and a thermostat as i didn't have a spare Arduino to run marlin on. 

    I turned the heath-bed to 90 Celsius and just before that i mounted to spray-painted PCB on it. 

    Next i started the laser again at some 150mm/min feed rate and that went really well. In total i did 4 passes.

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    Phase 3(Etching)

    In the end i just cleaned the board with some hot water out of my kitchen tap and i could already see the copper slightly. I was already thinking that this would work way better then my attempts before. 

    For my etching solution i used hydrochloric-acid and hydrogen-peroxide, the acid in a 10% solution, and the hydrogen-peroxide in a 3% solution. 

    I went to my bathroom, poured some warm water in the sink, placed a plastic container on/in the warm water and filled that with about 3/4 hydrochloric-acid solution and 1/4 hydrogen-peroxide. I placed the board in the solution, (i turned on the air extraction before) and left the bathroom for about 12 minutes. When i came back it already looked really good when i placed my flashlight behind it. 

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    Phase 4(cleaning)

    I gotten some steel-sponge and cleaned the board and i was even more impressed. The etch went way better then i expected and it worked out way better then the way we do this at school. 

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    Conclusion.

    I am really happy with the results, the chip in the middle is going to be an AS5047 to read the angle of a nema 17 motor. The precision is quite enough for this chip and there was only one short!! I do think i need some improvements in g-code as do want some more copper removed however so far the result is better then i expected!!