Desktop PCB production

A project that has bounced around in my head for decades has been a desktop PCB printer. A recent post here has ressurected that project in my mind. I have of course made PCBs before using the toner transfer method, but it is a pain and messy.

What I would ideally want is a finished PCB board to just pop out of the printer. What I could sacrifice for is one that is ready to etch. I know many others have pondered this and I am would like to collect some brainstorming bits and ideas that you have come up with.

I have had several back-of-the-napkin ideas such as: Using a focused UV source to print directly to a photosensitized board (do UV lasers exist?) Using an LCD as a UV mask Using a DLP set up with a UV source Direct milling (with either a micro-engraver pen or an adapted vinyl cutter/plotter) Dye Sublimation printers to print a wax mask (I wish I had kept my old Commodore Okidata Thermal printer!)

What would be ideal is the ability to print accurate and small enough to place SMD parts and tracks between pads. And accurate enough to have perfectly registered double-sided boards. For that later part, I think that could be handled by having some type of system that can measure the inserted board and ensure it is aligned perfectly to one corner.

Some systems I have thought of for that:

An XY movable bracket that will find a corner of the PCB and apply some pressure against an immovable opposite corner. It would then know the distance between those two points and have the dimension of the board. A set of contacts on the print head that would run along the board mesauring continuity. Once the pins dropped off the board, the circuit would be open and it would have found the edge. Also some type of optical system could also detect the size of the board similar to how a scanner does it. Maybe even something that runs along with the printhead and reflects a light on the copper. Have a black background to sense the edges.

For double-sided boards, either the above system would allow accurate registration of the board once it is flipped, or just duplicate the same system used to handle the top for the bottom (added cost, but hey we are brainstorming here!)

The print head could also switch in a drill and possibly different drill bits (easier with the direct milling/micro-engraver) or perhaps even a laser cutter capable of cutting through the board. The cutting laser would also be great for creating a shaped PCB.

Hmm... a laser in general may be able to do all things needed if the amount of cutting can be controlled. Not sure how practical that is since copper would conduct heat really well. Perhaps preheating the board would help?

So, any thoughts?

Nice!

http://www.youtube.com/watch?v=qB0F1yR0LIY

I did pick up a broken Epson C86 printer (and fixed it) for modifying for direct-to-pcb printing. I have managed to modify the printer itself just fine.

But in the end, it still requires etching with messy chemicals, is not going to be 100% registered in a way that double-sided boards will be accurate, and the inks are expensive. And you need to pre-heat the board.

Using photoresist is the most accurate method, but for the cost invested in that, I bet it wouldn't be much more to put something even better together.

Nobody here has ever pondered this and came up with some ideas? Really?

I know having boards made is fairly cheap, but honestly who doesn't want a printer that will spit out finished boards in a few minutes for them right at home?

you could always use a CnC to mill out a PCB board

That is one I definitely considered. Drawback is that the spacing between tracks is very limited. My research says 2mills in ideal cases, realistically 4 mils. Another issue is vibration moving the board during cutting and backlash of the bits. Just some obstacles to overcome, though.

I also just remembered another idea I had at one time: printing with conductive ink. I'm sure that would be more expensive than ordering boards, though. DuPont makes a solderable copper ink designed for this purpose, but I cannot find a supplier or pricing for it. It is CB230.

Interesting... http://arstechnica.com/uncategorized/2004/11/4366-2/

There are also methods for etching that don't use caustic chemicals. I'm not sure how effective conductive ink would be but you could do something like rapid prototyping with copper.

Yeah, like Fused Deposition Modeling using something conductive. Solder is not the greatest conductor, but that would obviously be the cheapest and easiest material to do something like this with.

Wait... that wouldn't really work unless there was some way to raise the melting temperature once it is placed on the board. As soon as you went to solder on your components, the solder would undo itself. So a material with a higher melting temperature would be needed.

You'd want to fuse your conductor to itself first then adhere it to your non-conductive board.

You could go Multiwire Board:

"Multiwire is a patented technique of interconnection which uses machine-routed insulated wires embedded in a non-conducting matrix (often plastic resin). It was used during the 1980s and 1990s."

http://www.pcb-leader.com/whats-multiwire-boards/

I haven't seen these in ages tho. Wirewrap comes close I suppose.

CrossRoads: You could go Multiwire Board:

"Multiwire is a patented technique of interconnection which uses machine-routed insulated wires embedded in a non-conducting matrix (often plastic resin). It was used during the 1980s and 1990s."

http://www.pcb-leader.com/whats-multiwire-boards/

I haven't seen these in ages tho. Wirewrap comes close I suppose.

Essentially machine operated point to point soldering (couldn't see the picture well enough)? Sounds like a fun and challenging project, but not very practical. lol

I like wire wrap and enjoyed using it in the early 80s. I would like to use it presently but have found the cost of sockets steering me back to PCBs. - Scotty

I don't use discrete sockets, I buy strips of pins and cut off the length I need. These guys seem to have good prices, 4.5 to 4.9 cents a pin. Great way to prototype and make changes or try different things while retaining stability. http://www.king-cart.com/phoenixent/product=SOCKETS+WIRE+WRAP+DIP+%2526+SIP/exact_match=exact

Well, looking over all of the different ideas I presented, there is one common thing and that is an X-Y platform that can auto-sense the size/shape of a PCB material inserted into it. Also given that that is probably going to be the most complicated part of all, I think I should focus my immediate efforts on that. Once I have a platform capable of that with positioning and accuracy that meets what I need, it will become a base to experiment with different ideas.

BTW, if you can find dirt cheap Epson C86 printers (which shouldn’t be hard since their waste ink sensors get tripped and becomes unusable to people) there is one part in there that is worth the cost: an optical (magnetic? not sure) linear encoder strip and sensor. That alone is worth more than the cost of the second-hand printer if you were to try to buy one of these strips. I’m sure that lots of modern printers use them now and on the epson at least, it would be very easy to tell if it has one without opening it up since it runs along the backside of the printhead.

Also, I wanted to throw something out there that isn’t ground-breaking but I have not seen anyone posting anything considering it before:

Shapelock makes a great material for creating parts for linear actuators. Attached are pictures of both a threaded rod with shapelock ‘nut’ and a smooth rod with a shapelock platform. Shapelock will take on the threads of the threaded rod when it is pliable, yet it will not stick to the metal. So you are left with a nut with a shaped platform attached. The smooth rod version is the same except no threads. The shapelock material is very similar in properties to acetal/delrin, so it has a self-lubricated feel to it. So it moves very smoothly along the rod. It will be a little tight in the threaded version, but for trying to create a precision positioning system, this is actually desirable to reduce backlash.

Both pics are just quick tests to demonstrate. I simply pressed the shapelock onto wax paper and formed a general flat platform, then folded the edges over the rods. So I am left with a level platform big enough to drill and mount stuff on to. You could certainly make it much more “pretty.”

It is possible to create pretty complex mechanisms with shapelock. I haven't been experimenting with it for long, but I have found a ton of uses for it. It also makes good couplers for motor shafts, though you need to install a set-screw since the material will not adhere to the metal of the shaft. One possibility that I have not tried yet would be to shape it over the motor shaft and then take it off and pinch it just a bit before it fully hardens. This would reduce the diameter some so that it would pressfit onto the shaft. Of course, I would still lock it in place if I expected any durability. What remains to be seen is if it would hold up to the heat generated by a running motor.

For my animatronic creations, I have used this stuff a lot. It makes custom hinges, ball-sockets, shoulders, elbows, jaws, face plates, eyes, eyebrows, eyelids, hands, fingers... you name it. Mechanisms that would normally require some expensive machine tools to create. But it isn't pretty. It is hard to get precision looking shapes by molding it by hand. And it is really NOT so easy to machine afterwards. You can't really sand it or grind it (without cooling fluid) because that generates heat and softens the material. Trying to cut it with a dremel doesn't work well for the same reasons. So it takes some careful planning before you begin.

An example is eyelids. I actually just make a thin sheet of the shapelock and press it into a measuring spoon of the right size, then quickly dunk it in cold water. I can then cut this is in half for eyelids using shop shears. The edge created by the spoon also allows me a surface to mount the lids.

I'll see if I can dig up some of the other parts I have made with it and take pictures if anyone is interested.

Back to your original question - how about a mechanical system that could apply copper tape to a board, with little spots of solder paste at X/Y junctions? When all done run it thru a re-flow oven to join the junctions.

Looks like width would be an issue - I seee plenty of places with 10 mil thick, but not 10 mil wide.

Perhaps some kind of sintered metal that could then be baked/cured, similar to conductive ink, but in a more solid form.

Or! cover a board with a meltable powder, use laser to melt the traces into place, and then gather up the excess for the next application.

Do you have a link to this Shapelock stuff?

CrossRoads: Back to your original question - how about a mechanical system that could apply copper tape to a board, with little spots of solder paste at X/Y junctions? When all done run it thru a re-flow oven to join the junctions.

Actually, I have manually used such a construction method in the past. Using the copper tape and kapton tape, I have made simple flexible circuits.

CrossRoads: Looks like width would be an issue - I seee plenty of places with 10 mil thick, but not 10 mil wide.

Indeed. I got around this somewhat by cutting the tape with a hobby knife into thinner strips. Very time consuming. But the circuits were very simple.

CrossRoads: Perhaps some kind of sintered metal that could then be baked/cured, similar to conductive ink, but in a more solid form.

Or! cover a board with a meltable powder, use laser to melt the traces into place, and then gather up the excess for the next application.

I believe the second idea is the same. Isn't that what sintering is? Or am I mistaken? That definitely does sound like the best approach since a laser could provide very fine detail.

CrossRoads: Do you have a link to this Shapelock stuff?

It is called shapelock, polymorph, or friendly plastic. Polymorph seems to be the cheapest variety, though it is not so easy to get in the U.S. and getting it shipped from the UK makes it more expensive than shapelock.

http://www.instamorph.com/ https://www.inventables.com/technologies/hand-moldable-plastic http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDrillDownView?langId=-1&storeId=10001&catalogId=10001&freeText=shapelock&search_type=jamecoall http://www.kelvin.com/Merchant2/merchant.mv?Screen=PROD&Product_Code=570071

This one is the best offer I have seen. 1Kg for $22 is an awesome price for the stuff: http://letsmakerobots.com/node/11563

And of course the original site: http://shapelock.com/page2.html

Those pieces that I posted pictures of only used about a tablespoon of the stuff and could certainly be made even thinner and better shaped which would use less material. This stuff is extremely strong once it hardens. It is about the strength of an acetal/delrin cutting board.

Here's a neat guide on the stuff: http://www.c-d-c-shop.com/Products/Polymorph/Polymorph.pdf

And this is what the stuff really is (Polycaprolactone): http://en.wikipedia.org/wiki/Shapelock

Cool. Thanks for the data.

Reading the wikipedia page, I found myself thinking "It's a floor wax! It's a dessert topping!"

Some things are confusing - "PCL is degraded by hydrolysis of its ester linkages in physiological conditions (such as in the human body) and has therefore received a great deal of attention for use as an implantable biomaterial."

Wouldn't degraded in the human body make it a poor choice for a long term implantable device?

What "cures" (for lack of a better word) the stuff into hardened material? Just application of heat, then it melts to shape and stays that way?