I’ve “rabbit-holed” on various projects – but I may have spent more time trying to come up with new ways to make circuit boards than any other. Over the last few I’ve months developed several new approaches – this one is my favorite.
When you print on glossy inkjet photo paper with a laser printer – something interesting happens. The toner sticks to the photo paper – but doesn’t really embed itself the way it does into normal paper. Hobbyists have found it’s possible to transfer the toner to PCB blanks – and use it as a “resist” to make etched circuit boards.
What I recently figured out is that certain silver adhesive will stick to the printed toner – but not the photo paper. If you apply a few layers of the adhesive – it’s possible to make circuit boards of useful quality.
Main Stuff You’ll Need
This project utilizes hardware that’s inexpensive – and many people already have access to. Consumables total up to around $50. If I don’t mention specifically where to get something – it’s widely available online.
Recommended Silver Paste: Atom Adhesives AA-DUCT AD1 Silver Adhesive
This is a single-part heat-cure “epoxy.” You can get some for under $20 on Amazon or directly from Atom Adhesives. I think its relatively low viscosity is part of what makes it work (the thicker AA-DUCT 2979 does -not- work well).
Alternate Silver Paste: MG Chemicals 8331S Part A
MG Chemicals 8331S is a two-part silver epoxy (widely available for about $40). I’ve found the “Part A” of the epoxy can be used as a substitute for the AA-DUCT AD1. It produces similar results – but is more expensive – so go with the AA-DUCT AD1 unless you can’t get it for some reason. I was not able to get good results using either the “Part B” or both parts mixed. Applying the MG 8331S requires a few changes to the process (mentioned below).
Glossy Photo Inkjet Photo Paper
I’ve tested Epson “Value Glossy Photo Paper” extensively. It works well – and that’s what I’d recommend using if it’s available.
PrintWorks “Glossy Photo Paper” also works – but it seems to have more issues with toner adhesion than the Epson “Value Glossy Photo Paper” does.
“Epson Premium Photo Paper Glossy” does not produce good results. It’s a resin-coated paper – which I suspect causes problems. If exploring other paper options – cheaper is probably better.
Matte photo-paper I’ve tested did not work.
Other glossy photo papers probably can provide good results – if you test something – let me know how it works – and I’ll list it here!
I’ve had better results with cotton than tissue / paper towels.
I’m using a Brother HL-L2360D – but I don’t think what laser printer you use really matters.
This is to provide temperature-regulated air for curing the adhesive – and soldering components to the boards. If you don’t already have one – decent ones are available for $50 to $100. It may also be possible to use a hot-air gun or other method of heating.
Low Temperature Solder Paste
Low temperature (137c / 278f) solder paste produces best soldering results.
The curing process will make the paper brown and smoke slightly. I have no idea what chemicals are being released from the coating – be sure to have good ventilation. Also – consuming silver is a bad idea – and the adhesive may otherwise be toxic.
1. Layout your board and print it
– Use your favorite PCB design software to design and layout your board (I use Upverter)
– Export gerber files
– Open your “top copper” layer using Gerbv (an open-source Gerber file viewer)
– Set the Gerbv background color to white
– Set the color for the copper layer to black – alpha (transparency) should be set to 255
– Set Gerbv rendering option to “High quality”
– Export from Gerbv into a PNG file / specify 1200 dpi on save dialog
– Open the PNG in Gimp
– Choose “Image” / “Print Size” – and set X/Y both to 1200dpi
– Export the image as a PDF with default settings
– Open the PDF using the viewer of your choice
– Print the PDF onto inkjet photo paper using your laser printer with default settings (if your PCB has fine detail – print at highest DPI)
(if these steps seem over-complicated – they work around some quirks I’ve seen in Gerbv’s print / export functionality)
2. Apply a layer of silver adhesive
Apply a small dab of the silver paste to the paper on top of the circuit traces. Be careful – it has a thin consistency – and is easy to apply too much.
Cut a small piece of the photo paper – and use it to “squeegee” the silver past into a thin layer covering the circuit board.
Tip: Try to avoid letting corners of the “squeegee” paper brush over the circuit surface. This can cause indents / scratches.
3. Wipe away excess silver
Lightly dab up any thicker patches of silver paste. Continue to do so until you can faintly see the circuit traces. (if using MG 8331S skip this step)
4. Heat for 5-10 seconds
Set your reflow station set to 200c / 392f – and about 30-40% air flow. Evenly apply heat to the entire circuit for about 5 to 10 seconds. (if using MG 8331S – heat for 5 seconds max at 100c / 211f)
5. Wipe away remaining silver
Brush the board lightly with a cotton ball. Almost magically – the non-trace silver will flake off the paper.
If any unwanted silver doesn’t brush away easily – repeat step 4. (if using MG 8331S – you will need to repeat steps 4 / 5 several times)
Problematic shorts / bridges can be be scraped away using a toothpick.
6. Cure for 30 seconds
With the same settings as before (200c / 392f) – evenly apply heat to the entire circuit for about 30 seconds. This will help cure the layer.
7. Apply a second layer of silver by repeating steps 2-6
Repeat additional times if desired!
8. Final cure – heat for an additional 60 seconds
Apply heat to the board surface for an additional 60 seconds. (if using MG 8331S – increase heat for final cure to 225c / 437f)
This final step helps fully cure the adhesive to the paper. At this point the paper will definitely smoke / brown a little – so be sure to use good ventilation.
Making Rigid / Durable Boards
While an upside of paper-based boards is that they are flexible – in reality any bending will pop-off soldered components (breaking the silver traces).
If you want to make more durable boards – you’ll need to affix the paper to something rigid. I recommend 1/32″ thick G-10 Garolite – available from mcmcaster.com. This is the same kind of fiberglass used to make most circuit boards. I use Spectape ST501 to stick the paper to the Garolite. It seems adequately heat resistant to stand-up to low-temp soldering. Other double-sided tape / adhesives probably work fine also.
Be sure to attach boards to the rigid surface before soldering. Any cutting / flexing of boards once components have been soldered will likely result in broken traces / pads.
You may also want to pickup some superglue and accelerator to mount larger components / leads. Epoxy should also work. Be sure to secure anything that might come under mechanical stress like battery holders or wire leads.
I’ve had good luck soldering components using low-temp solder paste (137c / 278f) and a reflow station.
I advise setting the reflow air temperature to 150c (302f). Hotter temperatures seem more prone to make the silver peel-up off the toner.
Standard-temp solder paste can also work – but the higher required soldering temperatures are more prone to cause problems with peel-up.
Soldering is also possible using a temperature-regulated soldering iron (but is more problematic). Be careful to contact the silver traces only with melted solder – not the iron tip itself (brushing a trace with the hot soldering iron tip often destroys it). Set your iron to as low a temperature as melts the solder.
If soldering seems to cause the silver to peel from the toner – try curing the silver longer and / or hotter. Extra layers of silver may also help.
If the toner itself seems to peel up off the paper – check if your printer driver has a “thick paper” option (and turn it on). If that doesn’t help – trying a different brand of inkjet paper may help.
Other Ways to Mount Components
My preferred way to mount components is using low-temp solder – but there are some other possible options….
You’ve already purchased the heat-cure silver adhesive. You should be able to use it to mount components – but be aware that the thicker blobs needed will require heat curing for additional time (see documentation on the adhesive). There are also various inexpensive two-part conductive epoxies – that don’t require heat.
I’ve had some luck using nickel circuit repair pens to adhere components. There’s also a silver-version of this product – but the nickel version seems to work better and is cheaper.
Anisotropic conductive tape (aka z-tape) is a magical material that conducts only across the z-axis. Hypothetically – you can just put a piece on top of a pad – then place your component – and everything magically works (connecting all the pins without shorting them). In practice – it can be a little tricky to work with. Too-small pads may not connect – and it’s pretty impossible to re-position if you don’t get it right the first time.
I think this is a potentially useful way to make circuit boards at home. Etched boards are definitely more durable – but this approach is quicker / probably less toxic.
If you have success / failure with making boards using this method – please let me know!