• Must change strategy

    Aritz Erkiaga • 03/20/2022 at 12:28 • 1 comment

    The current strategy can only bring resistivity down to about 400 Ω. Which it does in a matter of seconds, by the way, but 400 Ω is not a wire; 400 Ω is a resistor. The reason it can't go any lower is simple: as resistance decreases, heating and electrolysis increase, and the gases created within the channel are forced out, preventing the copper from forming a continuous wire.

    Of course, I could work around this in a later version of the process, but I have a better idea. High voltages can easily fry sensitive components, but there's something that can't: solder! Not your regular solder, of course, but Rose's metal, which melts just below the boiling point of water, that also just happens to be the usual bed temperature for printing ABS...

    Picture this. You start printing the PCB in ABS; the printer creates a small funnel within the piece, then pauses. You put a small bit of the alloy in there, which immediately melts, filling the funnel. The printer then goes on, covering the cavity with more layers of plastic. Without cooling the bed, you put the components in place, and you inject air through a small hole in the print, while removing the same volume through a second hole. The molten metal is forced through tiny channels and wets the components, soldering their pins, possibly to actual wires you have also placed.

  • About to start building third prototype

    Aritz Erkiaga • 02/28/2022 at 14:27 • 0 comments

    Testing of the second prototype didn't go as smooth as planned. While it improved on its predecessor in many ways, it also introduced new design problems. However, my experience with the two makes me confident that this new model will work well enough.

    I've bought new components, new filament for 3d printing a nice case, and am now designing some parts to make usage easier. I'll start building it tomorrow.

  • Initial testing done

    Aritz Erkiaga • 02/09/2022 at 22:38 • 0 comments

    I've tested an early prototype of the equipment to fix a resistor in place on a test circuit. While I haven't managed to, the voltage readings indicated that copper did indeed grow inside the channel, just too slowly for now (I only used a 5V gradient). I also identified other issues:

    • Bath resistance increases over time on narrow channels like this, probably due to anion depletion at the cathode. Periodically replacing the bath there with solution at the anode restores conductivity.
    • Fluid volume at the cathode is too low, a larger reservoir would act as a
      buffer to provide more anions and reduce purge frequency.
    • Copper at the anode eventually chips off, and the small pieces of copper can get into the channel.
    • Capillary forces are important at this scale, must take into account.

    Right now I'm building a better tool, that offers 230 V pulsed electroplating (yes, just some freshly-rectified AC straight out of the wall), smarter monitoring and more control over bath flow, as well as a modular design that can be simply plugged into the piece.