Printing Printed Circuit Boards

circuit

We really respect the old timers out there and their amazing ways of crafting PCBs; they used black tape on clear acetate sheets to create single layers of PCBs with a photoetching process. Now creating a PCB is a simple matter of opening up a CAD package, but like the old timers we’re still dealing with nasty chemicals or long shipping times from China.

The EX¹, a new robot on Kickstarter - hopes to change that. They’ve created a PCB fabrication process that’s as simple as printing something with an inkjet printer. Just put in a piece of substrate – anything from Kapton to acrylic to fabric – and in a few minutes you have a single-sided PCB in your hands.

The printer dispenses two chemicals, silver nitrate and ascorbic acid, that react and produce traces and pads for the circuit. Right now, the EX¹ is limited to single-side boards, but experiments on creating multi layer boards are ongoing.

In any event, we’re really impressed with how simple the EX¹ setup actually is. Inkjet is a mature, well understood technology with more than enough resolution for simple homebrew circuits, and the AgNO3 + Vitamin C formula could easily be adapted to an inkjet printer modification.

64 thoughts on “Printing Printed Circuit Boards

  1. First of all, let me say this is a really cool idea.

    But I think people may easily overestimate the capabilities of this method. I see some caveats that are not adressed on the kickstarter:

    - Silver is expensive. The market price of silver is approximately 1$ per grams. Silver in the form of AgNO3 will be even more expensive and there probably is some material loss in the process. (Leftover ink in the cardridge etc.)

    - The specific resistivity of a nanoparticle line is much higher than that of bulk silver. To get good conductivity you would have to sinter the lines, which is out of question for maby reasons.

    - Adhesion? I bet it’s not good.

    - Can you solder on it? In the video it looks as if all parts were connected with conductive ink.

    I would like to see the questions addresses. As I said, really cool idea, but I don’t believe this will replace your home-etched PCBs any time soon.

    1. Or durability. guarentee that example will not last more than a week. Good for rapid prototypes that you just need to test a theory or design then send the files out to be fabbed cheapy at sparkfun.

      1. You’re right, I see the big advantage to our printer as being able to test your designs before you send it out and it comes back wrong.

        Although, as far as durability is concerned, our circuits are almost as good as the real deal. We have demos that we printed 12 months ago, and have since been handled by hundreds of people, that still work just as well as when they were printed.

    2. Thanks for the encouragement. Let’s answer some of your questions:

      - Silver is expensive: Ture, silver is more expensive than copper (luckily we didn’t use gold!) with Silver Nitrate costing a little over $1.70/gram. However, there is basically no material loss, both because the cartridges are really reliable and tend to outlast the ink, and because this is an additive process so you only print the silver you use (unlike copper etching where you waste a bunch of copper).

      - Resistance: That’s true, you don’t get the same resistance/volume as you would with either bulk silver or copper, but silver has better conductivity than copper does anyway, so we’re playing a winning game. You can just about infinitely vary (within reason) the resistance of a trace by simply printing fewer or more layers.

      - Adhesion: Adhesion is actually really good. Obviously it depends on which substrate you’re using, but when printing onto paper and soldering a component down, you can easily lift the entire board up by grabbing the component with tweezers. I guess we should do a video on this to demonstrate.

      - Soldering: I guess I already gave away the answer to this one, but I really want to stress just how cool soldering something to paper is. We’ll have an update on our KS page with a video of this very soon. We’re recording it now.

      Hope this answers all your questions.

      1. Thank you for the clarification!

        >Silver Nitrate costing a little over $1.70/gram.
        Just to clarify: Silver nitrate is only 63% silver. You effectively pay $2.7 per gram of silver.

        http://www.convertunits.com/molarmass/AgNO3

        Resistance: Can you give numbers in comparison with a standard 35µ copper line? How this is a normal silver line?

        Adhesion: Great, that is much better than I’d expected. Looking forward to the video.

        Soldering: Sorry, I did not see that. In the video it looked as if the components were attached with conductive epoxy glue. I think it would be great if you made an additional video showing how to build a circuit and so on.

        1. Good points. We’re shooting some stuff right now to cover the topics of cost, resistance, and soldering. When we’re done with the circuits I think we’ll pump some current through them and film how the hold up (read: burst into flames :D). I’ll post back when the video is up.

          1. This is a great concept. If you are concerned about the durability of the trace, you can always electroplate with copper to reinforce the trace and spray with some solder-through lacquer. I have a setup for depositing patterned traces via vacuum sputtering and this is how I reinforce them.

    1. I’ll do you one better, I had my nose cauterized (dry weather here). They use AgNO3 for chemical cauterization, and it really hurts.

      1. We always have little black spots on our hands from refilling the cartridges (we’re too lazy to wear gloves), but we’ve never had anyone get it on themselves once the cartridge is filled. Also, once the silver nitrate has reacted on the print surface it can no longer harm anything.

        We’ll be sending the cartridges out in holders that prevent them from leaking, and you can store the carts in them when you’re not printing.

    1. actually it’s the opposite approach : they use a complex (expensive) ink with existing inkjet printers, EX1 use simple chemicals with a custom 2 pass printer…
      and basically if any patent would be put on any of these it would be stupid as they are both simple combination of existing technology…

      1. > a complex (expensive) ink with existing inkjet printers, EX1 use simple chemicals with a custom 2 pass printer…

        They use exactly the same ink. From the linked article

        “Using silver nitrate solution as the “metal ink” and ascorbic acid (vitamin C) as the reducing agent proved the most successful combination.”

      2. Thanks for being in our corner Olm-e, but we do use the same ink formulations as in the above article. You’re right that many other research articles do use expensive commercial nano particle ink which actually aren’t very conductive and often can’t be soldered to.

        We’ve made a lot of advancements over articles such as the above though. I’m yet to read one where the creators have been able to make a PCB that is actually conductive enough to use, solderable, or that doesn’t require any additional steps, all of which the EX¹ can.

  2. silver nitrate stains O_O

    it’s kinda cool but i don’t think the circuits could hold up for very long
    and that thin amount of silver will tarnish or break connections

    maybe it would last a little longer if it was covered with some sealant

  3. I want to see a movie with these guys. The one who looks like Joseph Gordon-Levitt could totaly be a genius thief together with his muscular friend who was also shown in the video. And of course, there is the girl. She is smart, nerdy and she is (secretly of course) in love with the Levitt-Guy. On they Heist they have to work together and everythings seems fine… until someone in the groups is showing his rela intentions… DUN DUN DUN…

    1. New AND improved! :P

      But seriously, silver nitrate has been used for ages in the photography industry. The great thing about our process is you don’t have to touch any of the chemicals. Everything is inside the cartridges, and once it’s printed it’s not damaging/dirty to touch.

  4. I messed with silver nitrate and ascorbic acid a couple of years ago, just laying down tracks by hand. I found that the resistance was way too high for carrying anything other than TTL or CMOS signalling. After some research I found it was because the silver is colliodal, or ‘lots of microscopic balls’. Current passes only where the balls touch and that’s what makes the resistance high. I had high hopes; now I have a bottle of unused silver nitrage.

  5. Whether somebody knows how the dispencer/injektor is made? Looks like they use not a regular inkjet cartrigde or something else?

    To what the above mentioned other readers, I can add that, silver is corosive(partially) and this may have influence on circuit quality and lifetime, especially if those circuits would have multiply strain, bend deformations, touching with bare hands.

    I had in mind where this type of circuitry i’ve seen. Thus in every computer keybord! Maybey manufacters have already invented this type of printing to mass production much earlier? :)

    1. We do just use standard off-the-shelf inkjet cartridges. Making new ones is a manufacturing feat we’re not quite ready for yet :P

      The silver nitrate used inside the cartridges is corrosive, but once it’s been printed it’s not. The circuits are fine to handle, we’ve had loads of people playing with the ones we’ve made and no stained fingers yet! Also we haven’t had any problems with circuit lifetime. We have demo circuits we made 12 months ago that are still going strong.

      I think this is similar to the contact inside keyboards actually. Clever manufacturers! :)

      1. Thanks for your answer ;) You refused any uncertainties about those type circuits. Its more atractive, but not for most.. Because this is not and OSS project as I understood :/

        If you use a common injekt cartridge how you deal with cartridge dry? Another aspect, how you know, how to controll the cartridge? Probably this requires reverse engineering to control it. Or you just made a contract with company, which sells cartridges? :)

        Yeah, keybord’s flexible plastic sheet with silver traces is the same conception as your ;] But is cool to see, that in market comes those ideas for everyone.

        P.S. About silver corosion I’ve made a negligible statement. Silver is far less corosive, when it is purer. And silver tarnish is mostly from organics like NaCl or other. In air silver is not that corosive as copper and need long time to get tarnish.

        And finally when you need solder a printed circuit.. You use solder with flux? Or pure tin(same as RoHS)? One more question i have: how circuit is resistant to heat from soldering-iron? Thanks for your comprehensive answers! (:

        @hardsoftlucid, thanks for you link, i’ll try to read it.

        1. Ups, sorry, You made updates on KS. About soldering you made short and informative video. Very good! And about OSS You have decided to go on with open source – nice! But I still want to know how you controll the cartridge, of course if that is not a your company secret :)

      1. I’m a bit confused, I’ve read that paper before and don’t remember seeing any part of it saying that the actual silver itself was corrosive in any way. Are you talking about silver nitrate being corrosive? Or possibly that silver can itself corrode/tarnish?

  6. They show a working prototype of the printer AND circuits working which have been printed. This puts the project waaaay ahead of some of the shyte posted on KS.
    Electrical characteristics of the “ink” should be published (and variance on different substrates).

  7. this really looks like a cool approach …

    but
    - the “home-made” printer looks quite expensive, why not sell a modification kit for a regular off-the-shelf printer? swap out the PCB if you need!

    - in the end the technology needs to compete with other approaches like milling a copper PCB – for this I dobut it will be competitive (cost, robustness) for a long time. For currently challenging tasks (printing on flexible surfaces) this could be quite interesting!

    1. We think it’s cool too ^_^

      We thought about making this as an add on to other printers (such as 3D printers) but it would be very difficult. The inkjet cartridges require special circuitry to drive, and that would need to be interfaced with the host printer’s motors, sensors, etc. It would be challenging enough to make this happen for one make and model of printer, but basically impossible to make it work with every one. This means only people with exactly the right printer would be able to use this, and we wanted everyone to be able to. However, we are going to revisit this idea in the future.

      I think we compete with other technologies/techniques pretty well. Milling machines are just as, if not more, expensive than our printer. They’ve also reached maturity as a technology and aren’t really going anywhere new. The way I see it is, if they haven’t taken off already, I doubt they’re going to. Our technology is just at the start of it’s life and it’s got so far it can go.

  8. I’m really impressed. $1499 seems a really high price point, though, for something that’s essentially an XY gantry as found in any number of (significantly cheaper) CNC machines plus inkjet heads.

  9. Sounds fantastic but this is another super hyped stuipd kickstartet projekt as many others.. that even successfully funded…

    Since this device is only for “prototyping” a circut the price per “printed” board can be higher than other methods.
    If ANYONE who is realy into DIY Electronics and homebrew circuts He/she may already have all neccessary tools like a small CNC mill for drill-prototyping circut boards or etching board via oldskool toner transfer or with a classic inkjet printer

    http://hackaday.com/2012/04/24/printing-pcbs-on-a-junked-epson-printer/

    http://hackaday.com/2011/03/18/direct-to-pcb-resist-printing-requires-minimal-additional-components/

    http://hackaday.com/2011/02/28/direct-to-pcb-etch-resist-printing/

    A friend of mine created over 300 small boards for RGB LED drivers purposes with the PCB Etch printing method. This is not “rapid” prototyping anymore he went fully into it and the price per board was fanatastic. I know so many people whom own a Proxxon mill MF70 equiped with DIY CNC parts for RC aircrafts parts, all of these neat cnc could easyily mill a perfect circut board either

    just my two cent
    greetings from germany

  10. It’s definitely a cool project, but my first thoughts were exactly as asked above – resistivity, solderability, cost of consumables.

    Addressing these and giving some numbers and demos on your Kickstarter will really make a difference between seeming like an “all presentation and no substance” con and a viable proposition where you know what you’re getting (and what the limitations are). It sounds like you’re doing exactly this so that’s great.

  11. For me TONER TRANSFER PAPER from ebay works really well and its cheap.
    Just print mirrored curcuit on the paper (only laser) and iron it onto the cupper board. Let it cool, peel of the paper and its ready to be etched. I did 100 pins smd chips with no problem. Unlike other types of paper I’ve seen used (baking paper, magazine paper, etc.) this paper doesnt care of overheating when ironing, the toner stays put and there is not floating. There is no need to use water to get the paper of. I love it!

  12. How about if they made a PCB which drives the cartridges upon commands over any microcontroller drivable interface and published a parametric cartridge holder design (e.g in openscad). I’m sure the 3D printer community would take care of the rest (e.g firmware, slicers, attachments to common printers). I’d be up for doing the marlin changes needed.

    1. That is actually a really good idea. The only problem I can see with it is we’d probably use i2c or something of that nature to connect our board with the host printer’s existing controller, which doesn’t have a very high data rate, and the raw data for printing is really quite large (each cartridge has 100+ nozzles, there’s 2 of them, and they each fire 600 times/inch).

      Although we could probably store the print data itself on an SD card on the cartridge controller and just have the i2c link responsible for syncing up the firings with the host printer’s movements.

      I’ll need to give this more thought.

  13. Congrats on the succesful Kickstarter Campaign! Currently studying software engineering at UQ and it’s great to see inspiring stuff coming out of Brisbane! All the best for the journey ahead.

    1. Thanks Barnes! You have no idea how nice it is to read comments like these. Especially when we’ve spent the last 14 hours straight working on an update/video/demo circuit and just want to collapse.

  14. Is it possible to print with latex/acrylic model paint or, in cases of alergies, liquid bandage fluid as an overlay to allow for multiple layers?

  15. @CartesianCo: I just want to say that it’s very refreshing to see how you’re taking all questions and concerns seriously, answering directly and correctly when possible (including acknowledging limitations when present), looking into unknowns, and adding frequent Q’s and A’s to the Kickstarter page. Plus doing it all with grace and style, even when the typical cynics here (I’m one of them) might not be particularly polite. Those are traits typically absent in the creators of most Kickstarter campaigns featured here.

    1. Thank you for understanding. We are just a group of hobbyists like everyone else here, and we know exactly how annoying it can be when companies aren’t truthful or transparent. Having a large and motivated community behind us is basically the most important thing we can think of. We’ll need those people to help us make the printer better and overcome its limitations. One day we’ll convince even the cynics ;)

  16. Your kick-starter page makes comments about not gouging us for the cost of the AgNO3 (or replacement cartridges.)

    I’ll bet there are a lot of us in the “makers Community” that would love to get just the AgNO3 and Vitamin C and the plans on how to make the carriage parts for the print cartridge that you used. Any possibility of adding that to the list of things to do?

    It looks like you used the HP 51640A cartridge. Good choice …. other cartridges use a foam insert to create the back pressure needed to insure the cartridge won’t leak out of the nozzles. Are you using just one nozzle or have you reverse engineered it enough to use the full cartridge?

    Do you have a way to get slightly used cartridges for this job? Or are you using brand new ones and just emptying out the ink?

    1. Wow Mike, you clearly know your cartridges. I know who I’ll be coming to next time I have a cart. questions ;)

      We’re not 100% sure about being able to provide the raw chemicals (not diluted in solution), simply because of issues with shipping. If it proves not to be a problem then, hell yeah, we’d love to sell anything and everything that can make ‘making’ easier.

      Finding the right cartridge for the job and reverse engineering it has been about 80% of what we’ve done since we started 12 months ago. We have indeed reverse engineered it fully, and we do use all the nozzles (it was crazy slow before). We’ll be releasing the plans for this and everything else when we ship the first units.

      We’ve been getting a supply of used, remanufactured, and new carts. for the job, and we’ve built a refilling jig for them. We are looking at getting remanufactured ones with our chemicals prefilled made for us, but that’s still early days.

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