Print toner directly to a PCB

We use the toner transfer method to fabricate printed circuit boards. The most difficult part of this is printing, ironing, and removing the paper from the toner that is used as an etchant resist material. [Mark Lerman] is developing a method to apply toner directly to the copper clad using a laser printer. Each of the photos in his gallery have comments that take us through his process. A laser printer has been modified to negatively charge the copper plate, thereby attracting the positively charged toner to it. Once the toner has been applied, the board is baked in an oven, then run through a laminator. This process can yield 2 mil traces and it looks like the potential for incredibly clean boards is just around the corner. The question is, will this be easier and take less time than using photo resist?

We’ve contacted [Mark] in hopes of getting more details. If you can’t wait for a follow-up, take a look at this thread concerning his work.

[Thanks Komradbob]

Comments

  1. pascal says:

    Has anybody tried using a cutting plotter (like Silhouette) to cut spaces into the copper?

    My idea was to just cut into the copper, etch shortly to make the spaces broader & deeper, then as for printing apply some etch-resistant to the board, etch again until the spaces are broad enough.

    • Kyle says:

      I have tried cutting foil without success on a KNK Zing (cutter plotter). The foil (aluminum and .001″ copper foil) tends to want to deform or tear instead of cut.

      With the right cutting tool it could be done.

  2. pelrun says:

    I’m more interested in using an inkjet printer to do the job instead. An epson printer (for the non-thermal printhead) and pigment ink seems to do the trick:

    http://techref.massmind.org/techref/pcb/etch/directinkjetresist.htm

  3. Brennan says:

    I built a cheap UV exposure box and I couldn’t be happier using the UV/photoresist method. I get much better results than the toner transfer method, although the positive-resist boards cost a little more.

  4. ClutchDude says:

    UV is-wait…2 mil? DAMN. That is nice. Good job.

    I still with Brennan in that UV photoresist boards are an easy and, for beginners, cheap way to make a prototype board that has really good traces. Not 2mil traces though, as far as I’m aware.

    The neat thing about the UV boards is they only take an hour and half and most of that time is just spent waiting(depending on the etchant).

  5. TheDon125 says:

    I find limited credibility in the claim that it negatively charges the copper plate.

    Well, I take that back, its certainly possible to charge a copper plate. Problem is, the entire surface of the copper gets charged, not just the parts you want. It works on paper because paper is an insulator. Copper is one of the best conductors out there, and so will almost immediately spread any charge throughout its surface.

  6. foo says:

    why not use a thermal transfer printer?

  7. AKA Steve says:

    I’m not sure I understand the use of the laminator. The board is baked in an oven and then put through a laminator multiple times, wouldn’t that simply coat the thing in plastic or am I thinking of the wrong laminator?

  8. TheDon125 says:

    edit:
    /me reads up on how laser printers work
    Yeah…you can delete my prior comment.

  9. rich says:

    How about modding a printer or plotter to use some kind of conductive ink? No etching required.

  10. osgeld says:

    darn it “the don125″ I was going to edumacate you

  11. Adam says:

    @rich: That’s being developed as well: http://hackaday.com/2009/10/28/xerox-ink-will-print-circuits/

  12. tulcod says:

    this is impressive, since copper is usually associated with particularly good conduction, and insulation is exactly what makes a laser printer work, as far as i know.

  13. humble reader says:

    Comparisons/Pros/Cons of this as an alternative ?
    http://techref.massmind.org/techref/pcb/etch/cx4200-vs.htm

  14. James says:

    Has anyone tried refilling an inkjet with standard indelible pen ink? My indelible pens resist etching, so it would seem obvious to negate the laser/toner transfer method and print directly to PCB for etching. I’m sure there are some hurdles though.

  15. komradebob says:

    @Brennan & ClutchDude – The joy of toner xfer and, even better, direct print, is that you get instant gratification. I have turned out boards in 10-15 minutes from the time I finalize a board design. Makes doing prototypes and proof of concept and little things really easy. No intermediate steps.

    Never mind most of the stuff I find myself prototyping now is surface mount, which means no through holes to drill (bonus) and very fine pitch packaging. Not such a big bonus when it comes to photo based processes.

    @AKASteve – The laminator is used to fuse the toner to the copper board. You don’t laminate on a plastic layer.

    @James: – The issue is keeping the ink flowing. indelible inks tend to be much thicker than water based inks.

    I use a plotter based method but I can’t get much below 0.035″ lines without going to toner transfer, which has other issues. Direct printing (which I have also done, he just writes it up far better) works great. If I have time this weekend, I’m going to see if direct print method can be used to create solder masks for surface mount packages using thin brass or aluminum sheet.

  16. ReKlipz says:

    As I don’t have an account on with Yahoo, I can’t post to the group. Subscribing to the mailing list means I need to await moderation from the owner.

    As such, if anyone is sub’d to the list or if Mark reads this comment, please check out this link regarding Humidity.

    http://www.evilmadscientist.com/article.php/laserjet

    This was featured on hackaday a while back, and they found a humidity sensor in the printer. The only documentation they found relevant was a patent, which related the charge of the tonor directly to the humidity.

    I hope this helps!
    -Nate

  17. HasBeen says:

    Been done before, and the fuser peels the toner right back off the PCB.

    I guess this person bypassed the step by fusing in an oven after printing.

  18. Jake says:

    @HasBeen

    You can put something (ie paper) over the board to keep it from peeling, but that also tends to “smush” it a bit, in my experience.

    This project is pretty cool, though. I have about 15 different laser printers sitting around, I might just have to start messing around with this… :D

  19. godard says:

    anyone tried printing directly to a copper clad using an inkjet modified to fit one? I just stripped one and wondering if im fighting an uphill battle.

    So, if i can get the ink to print on to the board properly, will it resist the etchant and not just bleed away?

  20. jproach says:

    @godard: yes, search here or on google. You need to bake the ink on for it to resist etchant. Some colors work better than others, and some might not work at all (I believe it needs to be pigmented ink).

  21. Mudo says:
  22. salec says:

    If only we had supply of flexible copper clads, probably this could be done on any laser printer.

  23. tanjent says:

    Neat stuff! I’ve been tweaking my PCB-making process until I can get 5 mil traces pretty reliably – http://www.flickr.com/photos/26397129@N00/4261186365/

    but 2 mil is well beyond the ability of my printer.

    I’ve got a writeup of my process here – http://tanjent.com/doku.php?id=pcb_fabrication – may be of help to folks who still have a boring cheap unmodified printer. :)

  24. mahoney says:

    This could work, so long as enough tx bias is applied, it will easily penetrate. It is not the copper that will be charged, the insulating layer of the pcb will participate in the transfer process.

  25. Brennan says:

    @komradebob:

    It does NOT take me that long to do a board with the UV method. It takes me a half hour at MOST. It takes about <1 minute to print out the design, <3 minutes to mount it in my UV exposure box and expose to UV. And while it's exposing I pour the developer, and dump the board directly in that for a few minutes. While that's devloping I mix the etchant using HCL and H2O2 and transfer the board to the etchant. That takes about 4 minutes for a 3×5" board and from there I wash it off and remove the photoresist, which takes maybe 5 minutes. I do most of my boards with SMT so I don't have to drill many holes after that. The whole process takes roughly 15-20 minutes to produce a board if you have the process down like do. Obviously this is an oversimplification but my point is that for the time and effort, the UV method is vastly superior to toner transfer, and I can get down to 2mil traces.

  26. Hitek146 says:

    Print directly to this:

    http://www.kitkraft.biz/product.php?productid=3981

    and then peel, stick to fiberglass board, then etch? Just a thought…

  27. DeFex says:

    someone should make “lightscribe” disks which are treated round copper clad boards. there would be size limitations sure, but imagine the convenience.
    put board in optical drive. burn image. etch.

  28. bothersaidpooh says:

    haha…
    i had the same idea a while back.

    interestingly you can “fake” the lightscribe signal using a micro with its clock phase locked to the motor rotation.

    the major annoyance being the cost of LS disks and having a large hole in the middle of the pcb.

  29. zeropointmodule says:

    or better still, use a thin layer of uv setting glue (sold for making optical bonds) and a uv laser diode.
    a bit messier but is very effective and only needs to be initially set then rinsed in solvent then fully set using halogen light minus filter.

    advantage here is that it works with copperclad with no modification and is compatible with the “salt water etch” process.

  30. overlords says:
  31. foxau2 says:

    I modified a laser printer a bit ago and am able to reliably print and etch 2 mil traces with 3 mil spacing every time. It takes less than 15 minutes from the time I click print to to when I can begin placing components. I use almost entirely SMD components so I don’t have many holes to drill except power and other copper wire connections. I’m now almost exlusively using flexible FR4, but I can print rigid boards just as easily.

    I prefer the flexible FR4 because I can get 15 8×10 sheets for about $10 on eBay, and I can cut it to shape with a pair of scissors. The fuser in the printer wasn’t capable of fusing the toner to the board, so I just use a small butane torch or lighter to fuse it. I use the sponge wipe method to etch them, and the toner remains in place perfectly fine without lifting or breaking! I’m going to be doing a write up, and making a video for Youtube as well.

    I did a quick write up for a friend a few months ago when I first started fiddling with it. The page is outdated in that I since discovered that the fuser won’t work. The only picture of a printed board on there was just a test and was never etched. I will make another page on my website in a few days showing some of the capabilities of the printer.

    My last board I etched just last night was a spiral of 3 mil traces with 3 mil spacing. The board is about one inch square. I estimated that the trace is about 11 feet long total, and gives me a resistance of around 10 ohms end to end.

    The link to my outdated page is:

    http://www.foxau2.com/laser.html

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