I wonder if circuits printed on paper would yield themselves to the same specialized applications as flexible PCBs.
For example, there are many variations of custom-made Dactyl keyboards, most of which require hand-wiring to accommodate for the curved shape of the design: https://github.com/adereth/dactyl-keyboard
Could you explain this a bit more - I think I don't quite know enough about electronics to follow the criticism.
Are you saying the traces are too resistive, or not resistive enough? How would that manifest - i.e. I see working circuits on the video, but are there classes of circuits that this would not work for?
Too resistive, or at least, higher than what they were aiming for.
You can compensate by making traces wider to get a lower resistance from the same resistivity, or by running circuits slower (digital circuit speed is often limited by the RC time constant where C is parasitic capacitance of an input somewhere — a higher-resistance trace takes longer to charge up the input gate capacitance). How hard it is to adjust for the higher resistivity will depend on the circuit, of course.
Too resistive. Copper, silver, and gold are used because they have very low resistance. Having high resistance in the traces makes anything more complex than a few low speed components not practical.
There's a ton of stuff I make (especially for hobby projects) where I'm pretty sure it wouldn't really matter. I'd love to fidget with stuff like this, especially since I just acquired a wide-format inkjet printer.
yes that's true, liquid inks usually have more resistance and this is a drawback. This is because the ink contains non-conducting materials which are required for the right viscosity and to prevent the silver to agglomerate.
These can usually be removed by heating.
One can also use high intensity light to "weld" the silver particles together without damaging the plastic substrate. This requires an expensive setup but improves conductivity drastically...
https://en.wikipedia.org/wiki/Photonic_curing
While the idea is amazing, I can't help but think about the environment. Until I'm not good enough at electronics and prototyping I think it's cheaper and safer for the environment if I experiment with a breadboard
The article shows examples of this technology being used to print components, such as temperature and humidity sensors, and antennas. That's more than a breadboard can do, which is designed for building circuits.
That's cool. Punch holes in these printouts, glue different layers together, add some extra ink into the holes for conductive connections between layers ("vias" [0]) and you can make multi-layer boards easily.
FR4 boards are built with woven fibers, and you can get measurable differences depending on how tight the weave pattern is, or the angle of your transmission line relative to the weave pattern. Given that paper is not woven, I’d expect a lot more dispersion than on cheap PCBs.
That said, with a good enough process able to press the paper + resin stack reliably, you could possibly get something usable.
The cost is probably not that bad on a per-unit basis, a 50mL seems like it should last for a pretty large number of PCBs. The problem is that the resulting PCBs are almost completely useless because you can't solder anything to them without melting the substrate.
The ink that works with standard inkjet printers just doesn't stick to materials like FR4 or kapton. There are specialized machines for printing conductive ink onto usable PCB substrates either with an extruder or screenprinting but they are at a minimum several thousand dollars and have extremely expensive consumables.
That explains why all of their examples are things like temperature sensors, humidity sensors, or antennas. I guess you stick wires on the paper using some sort of conductive glue?
There's silver epoxy but that's outrageously expensive.
Googling shows that you can add fine graphite powder to some kind of epoxy, to get something like that maybe.
Still glue is not super easy to control, and can't be used for fine traces. If the glue leaks across two pins, you can't just remelt it with a soldering iron.
Screen printing is a better choice for printing onto PCB surfaces. Copprint (an Israeli startup) has copper inks specificallý for FR4. Soldering is easier there...
Any idea how I could use a similar process to print glue? I would like to print glue in very specific places on a page so I can run sand over it and make a sand portrait.
Not OP, but curious why stencil is not a viable option for mass production? You don't have to roll compound over the stencil manually. Stencils are still used in applications like solder paste.
Yes stencil or screen printing is much faster for mass production. It is faster and you could directly print on a variety of substrates like FR4, plastic, glass and even paper. I'll wirte about that next
You could modify a 3D printer to output glue instead of plastic, a slightly related video I can provide shows how you can print chocolate on to a piece of break[0].
Perhaps, there could be a specialized substrate, that absorbs the ink, makingnit suitable for pasting on a blank PCB board. Say an organic porous film, on which we could print the circuit, then paste it onto a base, heat it and get a working circuit.
We would need to know a price indication (which I guess is impossible at this stage) to know which of the printer and ink make up the largest part of the cost.
For example, there are many variations of custom-made Dactyl keyboards, most of which require hand-wiring to accommodate for the curved shape of the design: https://github.com/adereth/dactyl-keyboard
Innovative designers have come up with alternatives that rely of flexible PCBs. The most recent example I recall is the Bastyl keyboard: https://www.reddit.com/r/mechmarket/comments/jvacs6/gb_basty...
I don't know how to even begin prototyping with flex PCBs, but that barrier to entry may be lessened with paper circuits like these.