Making Circuit Boards WITHOUT Solder

I wanted to populate a PCB, and have the LEDs light up AS THE BOARD was being populated. But that won't work with normal solder paste.

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[ardufreak]

You have a dual head on the Lumen. Simply use one head as "paste"/ink dispenser and the other head to place the part!

[DEADBF]

Could a diode laser melt solder paste in a localised area so the PNP can solder basic components as it places them without affecting the paste on adjacent pads?

...maybe would need some kind of dye adding to the paste so it's not as reflective as the laser melts it.

Might also be slow, but for prototyping that shouldn't matter much.

[MarkDurbin]

Doesn't the solder paste conduct before you put it in the oven?

[Magnetic]

11:10 If you want to replace the solder stencil, you can use a solder paste jet printer.

[RoyvanLierop]

Some UV curable conductive glue might be an option, this would give you ample time to place the parts and correct mistakes. Add an UV laser and some custom pathing to cure them instantaneous.

[chrisdixon]

That was really impressive!

I really like the idea of a solder / conductive paint head as part of the PCB placement process, and you're right, it would be a game changer for quickly prototyping.

Good luck!

[eshkrab]

Holy shit those LEDs lighting up on the lumen was the sickest thing ever

[bsc]

Dude. I love watching your videos. I play around with electronics as a novice hobby. But your project and your optimism just make me want to learn more. Keep up the good work bro.

[JoelRehra]

Super useful for fast prototype iteration. The best part of this is that you could reverse the process!
Soak the board in solvent and use the machine to pick the parts off the board again... fully automating the testing of different components on a single proto-board.
And having a paste extruder would allow to print on very precise custom resistor values onto a board just by varying the length and thicknes of the paste...
Exiting to see where this will go :D

[Luzgar]

How conductive is non melted solder paste ?

[excitedbox]

This is what a lot of printed circuit research is doing:
You could try mixing up a really THICK mix of copper sulfate + water (might want to test some solvents) and put small drops on the pads, dip the components into a solution of citric acid (water+ vitamin C powder). This mixture makes copper nano particles BUT copper sulfate is also used for electroplating. My theory is that as the citric acid washes off the component and mixes into the liquid copper sulfate on the board, it will form copper particles AND electroplate copper at the same time, welding the nanoparticles into a solid connection. Nanoparticles of metal have a lower melting point at <10nm and the current might even melt the particles as they form.

You can experiment with the chemicals like using iron/ferrite containing stuff instead or in addition to the citric acid. That should give you a mix of copper + iron nanoparticles and may be able to turn the sulfur residue into a gas.

PS. The fresh copper nanoparticle is OXYGEN FREE meaning they rust within minutes and form nonconductive copper oxide. The oxygen in water is enough to make it rust, which I got around by replacing water with other solvents. Good luck.

PPS. Copper nanoparticles are SALMON pink, copper oxide is rust brown.

[JoelRehra]

Ohh and be carefull with heat emmiting parts... Carbon paint looses resistivity when heated up... Very useful to create e-fuses for firework ignition... but bad when it cooks your circuit because of the runaway effect ;)

[Sam-J_]

I think you would highly benefit from using UV curing adhesives, that way you get the longevity of glue that doen't immediately start to dry as the PNP puts them down, and then when it's finished you can just cure it with an LED, or in the sun quite quickly.

[Daisy_human]

Its so good to see you back on youtube

[insanegammer]

Conductive epoxies are a thing, but they typically need to be cured with heat. Silver Filled epoxies are an industry norm.

[epremeaux]

some ideas:
- overall this process (or variations of it) would benefit greatly from a paste dispenser as the secondary tool on the P&P.
- First step : (especially for components with more than two pads, modules, etc) load the paste dispenser with component glue. This is already a common job in a larger fab houses. Glue dot the center of the component, then pick and place it. Now it wont move no mater what ends up happening with the conductive pasting.
- second step : after all parts glued down, reload the paste tool with conductive paste and dot right up against the corner of the leg-to-pad interface.
OR.. somehow build a head with all three : glue, paste, and pick&place.. pick the part, then while over the footprint, paste all the pads, hit the glue dot and place the part.
- The paste is messy without a stencil. If you want to dispense it by the P&P, you may need a knife or needle to "comb" between legs of SOIC, modules, etc to "cut" shorts.
- some sort of UV/heat curable conductive epoxy would be awesome. Add a sharp UB laser to the head. The laser point should be thinner than the component leg of most SOICs, QFPs, etc. you could even gob the epoxy a bit, provided there is a cleanup step after.. selective laser conductive curing. Just run back and forth across the leg to the pad a few times.

[jasonclark]

Neat idea! Next step is to install a paste/paint extruder onto the lumen, so that you don't need to manually pre-apply the adhesive. That would also eliminate the dry time issue if you can place adhesive then immediately place the part, and repeat. And you conveniently have two toolheads....

[ikocheratcr]

You could increase the viscosity by adding fused silica.
The paint conductivity goes up as it dries because the conducting particles come together and start to form a path for current as solvent goes away.
Long time ago I played with one that is basically nail polish with carbon and metal powder, for EMC shield painting.

[BobHannent]

About 10 years ago I toyed with the idea of using either an inkjet printer or laser printer to print onto laminate film to create multilayer, flexible printed circuits. Conductive inkjet ink was pretty widely available but toner less so. For fast, short run production runs laminate is very interesting to me. But also imagine graphene or carbon nanotube toner ink being fused to PLA based laminate film?
Perhaps I've just given away a billion dollar idea, but an idea is nothing if you can't execute on it.

[AdamDavisEE]

ACF is the film version - Anisotropic Conductive Film. Most of these films require pressure during placement, and heat to cure the adhesive. For the processes I've used it in, it requires 250psi (not a lot, given how small the component being pressed is) and 140C for 25 seconds (which is below solder oven temperature. ACP's downside is that the metal spheres, or metal coated plastic spheres, often don't stay equally distributed in solution, but you can place it with regular paste dispensers, and it can be cured with methods other than heat. You still need to use pressure on initial placement, though, to get the spheres embedded in both sides of the contact.

The conductive solutions you've used should be fine for your purposes. Their high resistance compared to copper, and lower adhesion will pose problems for many uses. I expect that debugging a board with a hundred such connections is not going to be pleasant, and the relatively high pin to pin spacing this would be capable of might limit products that can be used. For instance a 0.5mm pin pitch 32 pin package might have trouble with either shorts with too much paste, or opens with too little.

Unfortunately what that really means is that this is a replacement for simple pcbs that could probably be hand soldered and placed, and probably not a great fit for high speed prototyping.

I'd like to see you succeed, and I certainly don't intend to dissuade you, if you can make this work for even those projects it would be a huge benefit for many.