I dont get this - you can just print with SMD paste and then reflow the whole thing at once - though you will need high temp materials to do that, but several amateurs have done it.

Afaik there are a lot more high temp UV resins you can print with.

Reflowing smd paste inside print won't work reliably as the solder will tend to form blobs instead of keeping the track shape

I actually tried mixing in fine copper dust with fine SAC305 paste to create a non-liquid amalgam on re-flow, but the void/inclusion problem was worse than conventional SLS processes.

Also looked at RF and metal salt processes, but it had more problems/hazardous-material than traditional laser setups.

The core problem is making these machines safe and cheap to use. =3

Components are pretty easily done via pick-and-place, which was just demonstrated on video:

https://www.youtube.com/watch?v=MGZ0qpPN1uk

once one can make traces in 3D as part of a case/shell/frame/structure things get _very_ interesting --- consider that one electronics designer actually worked up a 3D CAD system:

https://dune3d.org/

just for making 3D printed enclosures:

>My primary use case for 3D CAD is designing 3D-printed enclosures for my electronics projects.

So, imagine what folks like that will make when they are able to 3D print a full circuit board as part of a structure, with components place/oriented in it in novel ways (heat dissipation? LEDs to indicate status?)....

Though, I generally like the idea of circuit traces embedded directly in mechanical design of a product, I suppose this would make devices completely and utterly non-repairable. Not that there's something new in this, but imagine, debugging a 3d volumetric circuit, where chips and discrete components baked solid into medium? And I also wonder, where such super high level of integration would be necessary, other than medical/wearable/implantable devices...

Design the "board" as a central component w/ one or more snap-on ocovers?

The smaller you can make things or more integral the more interesting you can do things - vape carts are a good example where it might actually reduce the total ewaste if the chip and the body were integral (though clearly would still create it)

Who needs repairability when you can just print a new one?

Status LED and button placement, those would be the the major benefits over conventional boards in non-exotic fields like putting circuits on plants. Would be fantastically valuable for the one-off tinkerer. But yeah, substituting home etching or milling and reflow would also be quite a dream come true.

They are produced by companies that specialise in producing ICs.

They can be placed manually or automated.

If you can print small enough with this technology I'm pretty sure you can make transistors - sort of 1980 era transistors, not very dense, but if you are printing bulk materials you can build in 3D rather than 2D, make interesting numbers of transistors, cpus in everything!

Home-printed 80s transistors would unlock a lot of analog-style guitar pedals. :D

A coil by any other name is an inductor, and that is really cool.

I can't imagine it is better than laser processes, but still impressive. =3

I guess they consider that a solved problem: when you can drop arbitrary connections without meaningful heating of stuff outside of the connection, just glue your SMD parts wherever you consider convenient and fuse lines to its connection pads.

But practical application would likely stick to more or less conventional boards (tiny ones for sure) and use those ink lines only for where it's needed. Unless perhaps there's an application where crossing over with simple fused layer printing allows something revolutionary from going 3D? But 2D boards are really, really cheap and multiple layers are already giving ever conceivable advantage 3D could give, outside of stuff like antenna geometries.

For one-off and prototyping, an integrated fused layer + pick&place + circuit fuser machine could be super attractive of course: basically bridging the gap between breadboard and production quality. But I really doubt that this device would be anywhere near hobby workshop tinkering range...

I appreciate all the replies but they all seem to involve making circuit connections by applying heat. If you have to reflow the whole assembly, then you've lost the big advantage they pitch from being able to drop traces on delicate materials without significantly heating them. e.g. If you want to print a circuit on a living bone, you can't reflow that whole creature who the bone belongs to, without killing it.

I'm not clear if their technique works for the junction of one metal trace onto something like a metal pin of an IC? Would heat conduct through to the rest of the pin, potentially damaging the surrounding tissue or whatever it's mounted atop? Did they study heating up highly conductive junctions and how well they can control how far the heat travels while still obtaining a good "weld"? I guess the idea might be they sort of "spot weld" the trace to the pin very quickly with high heat? I don't know, maybe instead of one "weld" they could do clusters of several very small ones at staggered time intervals to limit the maximum heat absorbed by surrounding material?

That's without even getting into adhesives, etc. to hold the components in place against those delicate materials before (and potentially after, depending on trace strength) they are soldered.

They say they built a circuit, but from what I can tell from my brief skim all they really did was lay down traces on exotic substrates, with the real circuitry connected to it but mounted somewhere else. I'm genuinely eager for someone to point out a counterexample.

Thanks!