Toner Transfer PCB Etch Resist

The use of pressure / heat / chemicals to transfer toner printed on various different papers by a laser printer or copier onto the target. This is often used to make PCB's resist layers, however: "I found that toner transfer works on painted surfaces. To improve the appearance of my bots, I give the top side of the finished pcb a light coat of Krylon flat white and then toner transfer. Looks great." Thanks to the Yahoo "Homebrew PCBs" group for much of the information collected here.

ON THIS PAGE:

Media
Methods
Process: Clean, Pre-etch, Pre-heat, Print, Transfer (by Iron, Laminator, Fuser, other), Remove media, Re-Melt, Touch-up, Etch, Remove Toner.
Advantages / Disadvantages
Links

Toner Transfer Media

Glossy Magazine paper (e.g. a page ripped out of Time magazine, etc...) Many people report success with this method but because the paper and coatings can change over time, the results can be inconsistent. The paper can be soaked or brushed off.
Laser (not InkJet) Glossy Papers These seem to work about as well as the magazine paper. The inkjet paper appears to not want to dissolve in water.
- HP Laser Presentation Paper, Glossy, 34lb, 95 Brightness, Q2546A.
  HP Presentation Paper (Laser) CG988A, Presentation Paper, 32lb. "works every time down to 5 mil. traces. Floats off the board after a short soak in hot tap water and leaves behind almost no clay residue."
Gootee paper (available from Staples)
- http://www.fullnet.com/~tomg/gooteepc.htm
  http://www.staples.com/Staples-Photo-Basic-Paper-8-1-2-x-11-Gloss-50-Pack/product_648181 (as of 2010/05/13)
- http://www.staples.com/office/supplies/StaplesProductDisplay?&storeId=10001&catalogId=10051&partNumber=633215 Staples Item# 633215 32# Color Laser Paper 300 sheets $11.49 + tax
Clay Coated InkJet papers. These may or may not be safe for a laser printer, but the advantage is that the clay will disolve in water after the transfer is complete.
- "Glossy Ink Jet Paper" from Royal Brights, 108 Main Street, Norwalk, CT 06851 phone 1-800-526-4280
  http://www.theroyalstore.com/royal-brites®-everyday-glossy-photo-paper-85x11-25pack-p-11807.html
Release paper A paper with a thin coating of dextrin which will disolve in water, releasing the toner printed over the dextrin.
- PCB FAB in a box from Pulsar Pro FX
  http://www.pulsarprofx.com/PCBfx/main_site/pages/direct_etch/how_it_works/how_it_works.html
- Homemade release paper
Dissolvo "Magic" Paper used by magicians for disappearing paper tricks involving water (the water version of flash paper) and said to be used by spys for messages that can quickly be distroyed. Dissolves in seconds. Available from Magic and Novelty/Spy shops. Thanks to Lee Leduc for finding and trying this!
- http://madhattermagicshop.com/magicshop/product_info.php?products_id=6614 $36/100 as of 2011/02/13
- http://www.kleargear.com/1815.html $6.95/25 as of 2011/02/13
Finger Paint Paper (e.g. Melissa and Doug brand, from Amazon) It has a thin plastic coating which adheres with the toner to the board (not to the bare copper) and provides extra protection from the etchant.
Parchment Paper aka Bakers Paper. Dustin reports that standard Renyolds brand Parchment Paper^ works great as a transfer media. A little care is required to prevent the toner from his HP LaserJet P1102w from rubbing off before the transfer, but it is stable enough to move around without flaking off. Because it is very thin and wants to curl, he tapes it to a regular sheet of paper with kapton tape and then uses that as carrier. Since the parchement is almost transparent, it's easy to align with the PCB stock for multi-layer boards.
The silicon coating has the added property of not allowing "super glue" to stick to the paper, which means you can do a chemical transfer without heat or extreme pressure by coating the PCB with "crazy clue" and pressing the transfer down onto the wet glue until it hardens. The toner will be held, and the paper will release. See below for more.
Wax Paper. Not the off the shelf wax paper, but special stock designed for laser printing and toner transfer
- http://www.ebay.com/itm/A4-10Pcs-Sheets-Heat-Toner-Transfer-Paper-For-DIY-PC
Laser transparency film. Some people have reported excellent results with this, other have reported the toner will not release at all. Try 3M #cg5000^, or #CG3300^ or HP brand. One advantage is that you can see the toner through the film as you iron it on. Faber-Castell OH-LUX Transparency film is recommended if you can find it; it doesn't seem to be available. It seperates from the toner automatically when the warm board is cooled in water.
Laser ready Vinyl Sign sheets. Andrew reports fantastic resuts^ with the process listed at:
http://en.electroni-city.com/ They are printing on the self adhesive print screen vinyl foil, not its paper side from the back.
- http://www.specialty-graphics.com/4725_FDC_Sign_Vinyl_8x10.html
- http://www.expressionsvinyl.com/catalog/update/12x24-outdoor-cricut-vinyl.html
Label backing (this is typically TOO slick and the toner will break or fall off before you can get it on the board.)

Toner Transfer Methods

"press and peel" Using special label backing paper
"press and soak" Using release paper or just disolving the paper itself.
Press, re-melt, and peel or soak.
disolve in Acetone, press, and peel. Said to work with Brother toner.

The 'Press-N-Peel' version generally works better, but costs more, than the 'Press-N-Soak' version. You can get both kinds from Electronics Express:
http://www.elexp.com Press and re-melt works very well if you are careful not to smear.
http://www.elexp.com/pro_npb5.htm (as of 2010/05/13)

http://www.youtube.com/watch?v=1mTMsK5qkZ0 complete PCB press and peel, etch, surface mount, reflow process from a hobby level.

Process:

Cleaning the PCB stock is critical. Scrubbing with scotch brite pads, bar keepers friend or other light abrasive cleaners is recommended. Avoid anything with oils, "conditioners", or that leaves any sort of film.

Having said that, it has been reported that CitraSolv cleaner (a very effective degreaser and cleaner based on d-Limonene from citrus rind) is an effective toner solvent and works nicely as an surface prep for PCBs. It does leave a thin film, but that film acts to bind the toner to the PCB. Richard Dheiliger reports that Laquer Thinner also leaves a "haze" that appears to help the transfer process.

Dustin reports that after the main scrub and clean with Glass Cook Top cleaner, a rinse in Tarn-X also helps so that may be a good way to "fix" any otherwise good abrasive cleaners which would otherwise leave behind a film.

Pre-etching the PCB stock can help the toner adhear. Some people wipe the copper with Ferric Chloride to "rust" the surface and then just leave it on, others dip the board and clean it off. This provides a rough surface that improves the toners ability to grab onto the copper.

Pre-heating the PCB stock in an oven (e.g. 350'F for 3 minutes) helps the toner stick. Be careful when laying down the paper as the toner will stick and smear if the paper is moved.

Printing When printing, keep in mind that the printers / software may not produce a printout that is /exactly/ the correct size. The traces may be "stretched" or warped in the x or y axis. It's good to have a PCB program that allows fine scaling of the printed size in either dimension. The alignment of the printer can also be adjusted by a competent service tech. This issue can, in extreme cases, cause individual components to fit poorly but most often the error is small enough that it only becomes apparent when you try to CNC drill the holes; when one side of the board is lined up in the mill, the other side will be off just far enough to cause the machine to drill outside the pad.

If you media is very thin or curly (e.g. magazine or parchment paper) or hugly expensive, you may wish to tape it to a regular sheet of paper with kapton tape along the leading edge. You can print the pattern once on paper, then use that as a guide to tap the media in place over the printed area, and feed the same stock again to ensure it will print exactly where expected.

Transfer

Methods of Transfer by applying Heat and Pressure:

Iron: A standard clothing iron can be used to press and heat transfer the toner to a PCB. Placing a large dowell or rolling pin under the PCB allows the pressure to be "focused" on one area at a time for a more consistent and stronger transfer.
Laminator: Needs to generate enough heat to melt the toner (usually ~300'F) and run slowly enough that the heat actually transfers into the PCB (pre-heating can help). It must pass materal as thick as the stock plus the transfer paper plus any carrier or pouch used to keep them together.
- GBC H-220 (GBC H-65 outside USA) 9" Laminator ~$60 claims 0.19" will run at least 0.032" board and an 0.064" small board with a bit of help pushing and pulling. Runs a bit to fast to really warm up the board, but can be modified to slow it down by swapping the drive gears.^
- "What makes GBC the only laminator manufacturer that works with Pulsar process is because of the way they redesigned the ordinary pouch laminator heaters. The ordinary laminator uses two parallel heating plates after the rollers to seal the pouch. GBC mounted two curved heaters, one above the top roller and one below the bottom roller and radiate heat into the neoprene coated rollers kind of like a rotisserie chicken cooker!"
- Generic LP-120 4.7" pouch laminator. ~$50. Temp control from 100 to 160 C, will run 0.064" board. ^
- Harbor Freight 9" laminator (#92499) $28 claims 300 degrees will run at least a 0.062" board. Transfer is not good as the rollers do not transfer enough heat and the board goes through too quickly.
Fuser: The fuser section of a laser printer can be removed and converted to re-melt and press toner onto the target panel as long as it is very smooth and can be made to pass between the rollers.
Other:
Jim KI6MZ says:
I got a 1 inch thick piece of steel (4x5x1 inch) and lapped it to make a very flat surface, attached a thermo couple to it. Using a hot plate to heat the iron block to to the target temperature [ed: where the toner melts; for this toner: 320'F] then placing this on my PCB/toner image sandwich and clamping it with a toggle clamp with about 400 pounds of pressure for about 1 minute (20 pounds per square inch). This gives me consistent results. ... For very fine pitches, I use a [pre-heat] temp of about 280 degrees (this will just tack the image to the copper) then I take this tacked PCB/toner/paper sandwich and place it on the hot plate and raise it to the toner melting point (without pressure) ... this will cause good adhesion of the toner to the copper with minimum image spreading.

Howard Payne says: "What i did was get an old cloths iron and took out the thermostat and bolted it to the roller casing (same place where a fixed 120c thermostat was mounted) wired it up and set it to about 180c (my toner is HP black)."
Fast Eddy says: "I print out the traces on magazine paper (which will tend to transfer the ink from the page) or glossy inkjet photo paper and tape it to the copper clad board with the blue delicate surface painter's tape and run it through a laminator a couple of times to stick it down to the board. I then pop the board directly into a toaster oven *with the paper still on it) at about 375F for 2 or 3 minutes to melt the toner and heat the board all over, then pass it through the laminator a couple more times before it has time to cool."
Lee Leduc says: "I took a sample of the printed paper and exposed it to acetone fumes for 20 minutes in a sealed plastic food container. The toner became slightly tacky to the touch. I ran the paper and pcb through a GBC laminator 8 times" Lee then soaked and peeled the paper leaving the tonor on the copper board. This was done with a Brother HL-2240 laser printer

Chemical Transfer Methods

Super Glue: If using Parchment Paper or other silicone coated stock (see above) then you can transfer without heat and only moderate pressure by wiping a thin layer of super glue onto the metal, and immediately pressing the baking paper with printed design onto the metal surface. The toner will stick to the wet super glued metal, but the paper will lift off after the glue has dried.
Rod^ says:
"Too much glue, and or too dark a toner printout will cause the toner to muddy up, so use a little glue on a Q Tip cotton swob. If you experiment, within a few minutes you can hit upon the correct, light print, and light coating of glue. I go for more of a grey printout, rather than black. Do not wipe the glue onto the baking paper, wipe it onto the metal....thin wipe with no excess puddles.
Do not wait for the glue to dry, but apply your design immediately. Burnish with the back of the finger nail, or a bone burnisher, etc., and no need to press too hard. Watch the design leave the paper using microscope or magnifier. When you sense the toner has transferred, you may wait a few minutes to ensure the glue has set. If things go wrong, a quick wipe with acetone cleans the metal down for a second try. If you get partial transfer, your glue may have dried too soon, or maybe you need a little more glue. Use the thin watery super glue, and make sure it is like water, it has a shelf life and sometimes it is already hard or thick from too long on the shelf at the store where you bought it. It is about 20 times cheaper by the once compared with 1 gram at the store. Keep it in the freezer for longer shelf life of about 6 months."

Blender Pen: Jesse Willis says: "What I did was swing by my local art store and pick up an Eberhard Faber Design Art Marker, Broad Nib 311 Colorless Blender (only about $2 US). With this, you simply photocopy the circuit you wish, and then lay the photocopy face down on the PCB. Run the marker over the back of the photocopy, and the image transfers to the copper." If anyone has a source for these pens, or has tried another brand of Colorless Blender Pen, please let us know?
Acetone / Alchol mixture: simpletronic documented the use of a mixture of Ethyle Alcohol (96% pure) and Acetone (or Toluene or Xylene) to soften the tonor and allow it to be fully transfered to the blank. He applies a mixture of 3 parts Acetone and 8 parts Ethyl Alcohol , or 4 parts denatured alcohol to 1 part Xylene, to the blank, then drops the paper, toner side down over that. After waiting 5 - 10 seconds, direct pressure is applied and then 2 minutes are allowed for the solvents to be "volatilized". After that the paper is removed by soaking.
http://www.instructables.com/id/Heatless-cold-Toner-Transfer-for-PCB-Making/?ALLSTEPS

Others report success with 70% Isopropyl alcohol with acetone (3/8) or 2/3 methylated spirit and 1/3 of automotive acrylic lacquer thinner (mainly acetone)

Paper Removal:

Soaking in warm water. Some papers seem to just float off the board without effort after about 20 minutes of soaking. Excellent results have been achieved with clay coated inkjet papers. Of course, the best for this is the commercially available "press and soak" systems
Gently scrubbing wet paper with a toothbrush, sponge or your thumbs can help.
Many people have reported that cooling or freezing the board results in a better transfer and easier removal of the paper.

Re-Melt: Re-heating the board after paper removal will allow the toner to re-flow and fill any tiny holes or cracks that would otherwise allow the etchant to penetrate the resist.

Touch-up: Check for traces that are broken or large pads / fills that haven't filled in well. Some laser printers have a difficult time filling in large areas. Using crosshatched fills rather than solid may avoid this issue. Correct these errors with a fine tip Black Sharpie^ (only the black seems to hold up).

Check for smudges, smears, or just places where the toner has spread too much and closed in the gap between traces or pads. Use a needle or narrow tip knife to scrape away the toner and expose the bare copper underneath.

Etching the board is the final step. See: PCB Etch, PCB Echant, Printed Circuit Board fabrication

Removing the toner: Acetone (e.g. Nail Polish remover) seems to be the only thing that takes toner off quickly and cleanly. It's a nasty chemical and shouldn't be used in a closed space. You can put the PCB and some Acetone in a ziploc bag, then soak it while rubbing the board through the plastic to keep your exposure to a minimum.

It has been reported that CitraSolv cleaner (a very effective degreaser and cleaner based on d-Limonene from citrus rind) is an effective toner solvent, but this has not been extensivly tested.

Advantages:

Simple: Print, transfer, remove the media, etch, clean, done. The only thing that might require some tinkering is the transfer step.
Cheap: Assuming you have access to a laser printer, the transfer media is low cost (can be free) and you may get away with just a clothes iron to do the transfer. Even with a laminator, the cost isn't much.

Disadvantages:

The pressure involved often causes the transfer media to stretch or expand, resulting in a small, but sometimes critical enlargement of the resulting pattern. This typically prevents toner transfer PCB's from being CNC drilled. It can also cause alignment problems with larger double sided boards. Direct InkJet, and Hybrid InkJet / Toner offer more repeatability, but the best for this is Optical
The pressure involved often causes the traces to expand, limiting the minimum trace width and space between the traces that can be achieved. In general 10 mil traces and spaces are the limit.
Getting the toner to consistently transfer to the PCB stock can be a "magic" process. Some never have any problems, others can never get it to work consistently.
Most laminators must be modified to allow a full thickness PCB to pass through.

Links: