Hybrid additive manufacturing of 3D electronic systems:
I've got no idea why so much (additive manufacturing) research is behind an access wall that only university students or those willing to pay ££ per paper, but I was reading
Material issues in additive manufacturing: A review and the last set of images looked very intriguing:
So I looked into this paper and the method they used, which is seen below:
I had a feeling that some kind of dispensing paste was more likely to happen than a decently conductive UV curable resin. If the cleaning roller works as intended, I'd likely be able to have a more streamlined process to what these researchers acheived in 2016. I doubt I'd have to use the oven until the part is finished since they won't be upside down or pushed around by resin in a vat. They use a clear resin with a Tg of 100C. Resistivity
For a reference,
this is the milliohms/sq for copper.
I've highlighted 70um because that is the same thickness stated from Voltera, who sell a PCB that prints in gels.
I feel like I'm coming in, looking at and swiping every additive manufacturer's tech right now. First BCN3D, then trying to replicate Stratasys' Polyjet, continuous fibre reinforcement from Desktop Metal and CF3D, Nano Dimension and now my eyes are on Voltera.
As you can see, the gels are pretty distant from copper (and the other metals, seen below).
For a 1.6mm, 4 layer PCB, there does seem to be enough room to make any 1oz traces (35um) into thicker ones like 80um or 160um, which should help with resistance issues.
.16+.28+.16+.12+.16+.28+.16 = 1.32mm
.16+.32+.16+.12+.16+.32+.16 = 1.40mm
That would leave enough for a 120um thick soldermask each side to acheive a 1.64mm PCB.
Anyway, it seems they're using "silver electrically conductive adhesive" and I was able to dig around and find something:
While technically expensive (£7,866/L), it sounds like the stuff in the paper by the description:
Is it me, or is that resistance really low? Perhaps there's an extra 0?
Why is the resistivity 1/6 of copper? I don't recall silver being that much better than copper in the electrical resistivity table I found a day or two ago.
26th Aug] It's because I didn't notice that the pastes are in ohms/sq not milliohms/sq. The first paste is 20mOhm/sq and the second is 10-50.