16. Wildcard Week - Electroplating PCBs

I have been seeing a lot of videos on electroplating 3D prints, which seems like a cool process to spice up your final product. I wanted to see what I could accomplish with this method - specifically to see if there was potential to make circuit boards where the traces are created via electroplating. From preliminary research, it seems to be a common methodology for creating/reinforcing through-hole vias. You can read about the process here: Applications of Electrolysis Electroplating Electroforming Electrorefining

Design File Links
LED Laser Engraved PCB Design

The Electroplating Process

Electrolysis is the process in which you suspend electrically charged anodes and cathodes in a metal-saturated electrolyte. For my use case, I used Copper(II) for my process, since it has good conductivity, easy to access and is cheap in comparison to other metals. This can be done with a variety of metals, such as tin, brass, aluminum, gold and silver, to achieve a variety of colorations and conductive properties. Silver can be used to increase conductivity of copper, and be more resistant to oxidizing. Gold can be used to completely prevent oxidization, but comes with slightly lower conductivity when compared to copper. Both of these options are great, but come with a price tag - and while it would be possible to create an electrolytic solution for these two metals, I had access to a pre-made solution of Copper (II) Sulfate from our Chemistry department at Latin.

To create an electrolytic solution, all one needs to do is fill a container with white (DISTILLED) vinegar (for the electrolysis), and distilled water(to help dissolve the metals), and place two cleaned pieces of metal within the solution. Adding a constant current to the metals (one as an anode, and one as a cathode) without them touching will cause a redox reaction which allows for the positively charged metal ions to detach from the source materials, and then dissolve into the solution. Many times this process will cause the solution to change color due to the oxidizing material, and for copper this creates a blue hue. This won't make Copper(II) Sulfate like I used, but it will make Copper(II) Acetate, which can perform a similar process of electroplating. Another option would be to use citric acid, to create Copper(II) Citrate, which can also be used for electroplating.

I would be interested in trying these home-made solutions using less volatile ingredients (Vinegar or citric acid) in the future to see how they compare to the Sulfate solution. This video, by Geoffrey Croker, shows the process of creating your own plating solution, and then electroplating simple objects.

Testing PCB Creation via Electroplating

For this week, I wanted to try creating a circuit on a glass substrate, using electroplating to build the traces and pads. I used glass slides as the substrate since it would be heat proof, rigid, and water proof (which is important for electroplating). I also thought it would just look neat! I designed a simple circuit using a 412, some LEDs and some resistors. I figured this would be a good prototype to test electrical conductivity as a benchmark. My idea is to use the laser cutter to etch into blue tape placed on top of the glass slide. Then, I would use a conductive paint to create areas for the traces to build in the electrolytic solution.		Simple ATtiny412 based LED sample circuit
Applying blue tape to the glass slides	Result of laser engraving of the 412 circuit (multiple times)	The glass slide is covered with conductive ink, then wrapped in a copper wire to help distribute current across the board's face.
I started by etching the glass using the laser cutter, with blue tape so the conductive ink will lay out the traces. After a generous slathering of the ink, I then took some bare-exposed copper wire and wrapped it around the board to distribute conductivity to the different pads and traces. The idea here, is then to have the copper from the copper sulfate to be attracted to the conductive ink, and bind with it to form the traces. It is important to be delicate with the glass, since it breaks easily. To the right you can see what the ink looks like through the other side of a slide I accidentally broke.
For electroplating, it is ideal to use pure metals with little to no impurities or alloys. To source some pure copper, I found some stranded copper wire then removed the insulation. This will provide the extra copper that will dissolve into the sulfate to replace the copper ions that bond with the conductive ink on the board.
Since electroplating can release hydrogen gas, I created a makeshift fume hood using a spare outside-exhausting duct from an old laser cutter we used to have in the lab. The suction of the exhaust was strong enough to steal a pencil from me, so I was not too worried about fumes escaping.
The pcb cathode was connected to the ground of a power supply, and the donor copper was connected to positive supply voltage. The power supply was then turned on. I tried a variety of voltages, but it seems that the higher the voltage - the more prominent the results.

		12 volts	30 volts
Here are the results of 2 tests using the copper(II) sulfate. The first picture shows the results before the removal of the blue painters tape. The 30V powered copper adhered much better to the glass than the 12V. These initial results seem promising, and after coating it in a solder mask I attempted to solder components to the board. The copper however didn't fully bond together, so soldering was not possible.

Here are the results of the final boards:

Some future improvements could involve using a higher voltage, perhaps a deeper engraving to give more adhesion, and including a solid binding ingredient such as resin to the conductive silver paint. Right now, there currently is no possibility for it to work properly due to the "flakiness" of the copper coating. This methodology of using the laser cutter to cut the circuit could however be used to create solder stencil for SMD pcbs.