-
We all know that for the time and hassle involved, hiring a company to crank out small batches of boards for you is superior to doing your own production run. Generally speaking, at least.
But I only need one board at a time, and it usually takes me several iterations to get the circuit exactly the way i want it. So I've been playing with doing thermal transfer PCBs, and have finally got to the point that I'm quite pleased with the result. My first results were horrible; but now, the quality of the traces is quite good. I've attached an example. This is how I'm doing it:
I've found that cleanliness is really important, much more so than I would have expected. I cut the board to size, then wash it in acetone, then sand it with 2,000 grit sandpaper to expose raw copper, then wash it in acetone again. I wear nitrile gloves while doing all this; it keeps the acetone off my hands, and skin oil off the board.
For transfer paper, the best thing I've found is the backing paper from peel and stick shelf liner. In my youth, this stuff was called MacTac; now, it's pretty generic. In Canada, you can buy a 5 foot roll of the stuff for $1.25 at the dollar store. Cut a piece of peel and stick the size of the circuit you want to print, remove the backing paper, and throw the self adhesive shelf liner away. Now print the circuit on a sheet of typing paper, using a laser printer - not an inkjet. Position the backing paper on the sheet so that the backing paper covers the image; tape it down and run it through the printer again, so that your image prints on the backing paper.
The next best transfer paper I've found is the yellow stuff that comes out of China; but the backing paper from the peel and stick shelf liner stuff is as good or better, is cheaper, and is probably available locally. I've also experimented with silicone impregnated baking paper, Betty Crocker brand from the dollar store and that also works not badly (but i think the MacTac backing paper is superior).
Once I have the image printed on the backing paper, I place it in contact with the freshly cleaned copper board, fold the edges around to the back of the board and tape it in place. I then run it through my ultra cheap Scotch laminator ($30 at WalMart in Canada). The machine has two choices: 3 mm or 5 mm. I set it to 5mm, and run it through about 24 times. I think that's overkill, but I haven't yet run experiments to determine the minimum number of times necessary for a good transfer.
Having laminated it 24 times, I then roll it flat using a kitchen rolling pin for about 30 seconds. This ensures that i get excellent contact as the ink cools.
When I remove the transfer paper, I find that I have - usually - 100% transfer. The results - I think, anyway - really are good. I then run it through Ferric Chloride, rinse it, dry it, and give it an acetone rubdown to remove the laser image and reveal the copper.
A few notes on printers. First, it has to be a Laser Printer, not an inkjet. Second, most printers have - buried in the settings - a way to increase the toner density. On Hewlett Packard printers, the range is 1 to 5; the default is 3. Set it to 5, and you'll transfer more toner onto the paper, which gives a superior result.
There's a website - pcbfx.com - that sells a commercial kit for making high quality thermal transfers. They sell laminators, and a very expensive - and presumably, a very good - thermal transfer system. I've not used their products, but they do look impressive. They also have a lot to say about printers, but this only relates to usage with their system. They hate Brother printers, but others on the web are getting good results from Brother printers.
I'm now going to experiment with photo-lithography - using Riston film in hopes of getting even superior results. But I'm pleased with how the thermal transfer is working out. Keep rockin, folks! >Charlie
-
Nice work Charlie and almost word for word replicates my ventures into toner transfer.
A word of warning, once you have a recipe that works some small little change in your gear will change the result so always be prepared to tweak methods to maintain a good outcome.
Waxy backings from Avery labels or similar were my fav too until I had porosity issues with a 600dpi printer and moving to our better 1200dpi one stuffed the whole process up with smudging of the transfer so I had to go to a more poros transfer paper in order to oak in some of the excess toner.
Happy transfers ! -
I'm now going to experiment with photo-lithography - using Riston film in hopes of getting even superior results. But I'm pleased with how the thermal transfer is working out. Keep rockin, folks! >Charlie
If you can create accurate and high contrast artwork, then Riston will give amazing results. I've been using some form of dry film resist for decades, and it works very well.
Jon -
Hi, Tautech! Yeah, I think that thermal toner transfer is incredibly sensitive to small changes. I started out by trying to duplicate others results, and got terrible results. But, when it works, it does work well. The trick, I think, is to define all the variables, and make changes in one area only until you arrive at the right mix.
Hi, jmelson! I'm looking forward to working with Riston - had to order washing soda through Amazon, it just isn't sold locally and there isn't a good chemical supply house nearby. I also have to finish my UV exposure box. Many years ago, I worked as a photo lab technician, and quite enjoyed it. So the idea of working with a photo sensitive product holds some real appeal.
Thanks for the encouragement, everybody! I appreciate it. >Charlie -
I've done a lot of toner transfer PCBs over the years. I had quite a good setup using a modified kitchen hot plate with a vacuum compression system for doing the transfer. Best transfer material by far was Press-n-peel Blue. Accurate traces and no pin-holing. As mentioned, keeping everything clean is critical.
Best result: a panel of double-sided Kapton flex circuits, using 5mil/5mil design rules. 23/24 circuits worked (I had hoped for two or three). -
I've done a lot of toner transfer PCBs over the years. I had quite a good setup using a modified kitchen hot plate with a vacuum compression system for doing the transfer. Best transfer material by far was Press-n-peel Blue. Accurate traces and no pin-holing. As mentioned, keeping everything clean is critical.
Best result: a panel of double-sided Kapton flex circuits, using 5mil/5mil design rules. 23/24 circuits worked (I had hoped for two or three).
Impressive !
-
I've done a lot of toner transfer PCBs over the years. I had quite a good setup using a modified kitchen hot plate with a vacuum compression system for doing the transfer. Best transfer material by far was Press-n-peel Blue. Accurate traces and no pin-holing. As mentioned, keeping everything clean is critical.
Best result: a panel of double-sided Kapton flex circuits, using 5mil/5mil design rules. 23/24 circuits worked (I had hoped for two or three).
Where did you get your substrate blanks from? -
Would you mind sharing the Gerber for your test pcb? I want to play at some point etching a pcb - looks quite a good design to try and dial in the process?
Thanks in advance -
The blank double sided Kapton laminate came from a colleague, who had asked for a sample from DuPont I think it was. He thought they might send a small piece, but what he got was 5 large sheets, roughly 400mm square. And for free.
-
Nice job. I did a board (several actually), reproducing an old magazine project:
http://wsudbrink.dyndns.org:8080/cyclops/index.html
http://wsudbrink.dyndns.org:8080/cyclops/pe_circuit_board.html
I used pages from an old National Geographic magazine to transfer the toner, as that was what we used back then. It still works pretty well. -
I use a HP 6L to print to Celcast coated paper. I find that reducing the moisture content by heating the paper prior to printing improves the toner density.
Edit: These are 100 thou tracks I etched on a scrap of PCB. If I had of skipped the step of heating the paper, the copper would have certainly been pitted and possibly perforated.
-
that would probably improve dimensional accuracy too.
One of the things I like about using press'n'peel is its mylar, not paper. So moisture is not an issue. -
How comes your not using a uv box / transparency? I was always under the impression that’s the way to go for accuracy?
-
Here are a couple I have made. The first one is a double-sided board from a long time ago when I drew them by hand with an etch-resist pen. Lovely curvy tracks are possible that way. It is possible to do small SMT components, but not easy.
Then I switched to toner-transfer using glossy paper. That worked, but I almost always had to fix it with the etch-resist pen before etching. Now I use press-n-peel, which comes out nearly perfect if I keep the board clean enough and use the iron right. The second photo is the most recent PCB I made with this method. It has a SOIC chip and some 0805 capacitors on it. I can do smaller, down to 0.5mm tracks and packages like SOT23-6 reliably. Even smaller is possible, with reduced chance of success. I can do double-sided too, with some difficulty.
I don't know why doing this isn't more common. Sure, you can get better quality PCBs with no effort by paying someone to do it, but can they get your boards done in <1 hour like you can if you do it yourself?
-
But I only need one board at a time, and it usually takes me several iterations to get the circuit exactly the way i want it.
Thats just down to experience designing pcb's.
Trying to rush the job will often result in bad results.
1/ Use star grounding for anything carrying more than a little current.
2/ Keep input and output circuits separate.
3/ Be aware of power supplies with charging impulses into smoothing caps.
4/ Keep noisy circuits like clocks away from audio signals.
-
I haven't tried PnP yet and use an old copy of Altium for my artwork and 0.5mm traces and SOT23-6 are close to my limits too. Using SOT23-6 dual mosfets can be fun needing to get a trace to the center pad from each side when only doing single side PCB's.
Then I switched to toner-transfer using glossy paper. That worked, but I almost always had to fix it with the etch-resist pen before etching. Now I use press-n-peel, which comes out nearly perfect if I keep the board clean enough and use the iron right. The second photo is the most recent PCB I made with this method. It has a SOIC chip and some 0805 capacitors on it. I can do smaller, down to 0.5mm tracks and packages like SOT23-6 reliably. Even smaller is possible, with reduced chance of success.QuoteI don't know why doing this isn't more common. Sure, you can get better quality PCBs with no effort by paying someone to do it, but can they get your boards done in <1 hour like you can if you do it yourself?
Yeah this for sure and with the current holdups in PCB production due to the virus outbreak we might see more giving it a go. -
I have also done a few with the toner transfer method. Although I haven't really calibrated my method. Had different irons and different papers.
Tried to look for glossy papers, papers from magazines, gift wrapping papers with various results.
Recently I started to use plain paper and had better results than with some of the glossy and gift wrapping paper methods. Just get the toner to stick, then using a water squirter(ones like hairdressers use), wet the paper, heat it again, a few times like that and then dissolve the paper in water. Clean it with a sponge to ease the paper away until only the toner is left.
Sometimes I still need to scrape some traces because the etchant wasn't biting anymore.
I'd like to make a UV box, to get rid of the toner + paper method. For etchant I use 60% Vinegar(9%) + 40%H2O2(3%) + 1 Tbsp Salt. Works good enough for my prototypes.
The red layer over one board is nail polish. The blue one is a test PCB with UV soldermask.
Pasives are 0805. Tried TQFP32 without problems, SO packages.
-
Back in the day when I made my own PCB's...
I never could get toner transfer to work reliably. What did work is the presentized photo resist copper clad boards.
This process involved printing the artwork using a laser or an inkjet on overhead transparency film, taping the artwork to the board, and then exposing the boards to fluorescent light for 8-10 minues. After they were exposed, you'd rinse them in a developer solution. Once they had been treated correctly with developer, you'd simply wash off the nonexposed (or exposed depending on polarity) resist, and then drop it in etchant.
Worked really well. Plus you could touch up your artwork with a sharpie or similar.
I also wasn't a big fan of ferric chloride after discovering ammonium persulfate... Of course back in the ancient times I laid out a lot of boards directly on the raw bare PCB's using a combination of rub-on-transfers and sharpie pen, and etching them with ferric chloride, since that was what radio shack sold.
The photo resist PCBs are available in the US from circuitspecialists.com, which have been selling this stuff for a long time. -
I have also done a few with the toner transfer method. Although I haven't really calibrated my method. Had different irons and different papers.
Your results indicate good toner density. What model printer is it?
Tried to look for glossy papers, papers from magazines, gift wrapping papers with various results.
Recently I started to use plain paper and had better results than with some of the glossy and gift wrapping paper methods. Just get the toner to stick, then using a water squirter(ones like hairdressers use), wet the paper, heat it again, a few times like that and then dissolve the paper in water. Clean it with a sponge to ease the paper away until only the toner is left.
Sometimes I still need to scrape some traces because the etchant wasn't biting anymore.
I'd like to make a UV box, to get rid of the toner + paper method. For etchant I use 60% Vinegar(9%) + 40%H2O2(3%) + 1 Tbsp Salt. Works good enough for my prototypes.
The red layer over one board is nail polish. The blue one is a test PCB with UV soldermask.
Pasives are 0805. Tried TQFP32 without problems, SO packages. -
Quote
Your results indicate good toner density. What model printer is it?
Samsung Xpress SL-M2026 Laser Printer
I also set it up to not spare the toner, and all sorts of other settings, to make it do the stuff. -
A lot of printers let you tweak toner density - usually its a setting buried in the printer driver. Sometimes you have to mess with the front panel controls. Default density often isn't good enough for TT.
-
I picked up some Press N Peel PCB Film from the local Jaycar store today. It worked near perfectly, just one pin hole and some track fattening.
I cleaned the PCB with stainless steel wool followed by Scotch-Brite with liquid laundry detergent. I used an iron set to 130°C, maybe too high.
Many of the youtube demos are so discouraging. -
Wow! I've been away from the board for a while - my car has decided to not run, and I've been involved in that - but I just got back and read all the fantastic posts everyone has made. How cool! I'm definitely hangin with the right people.
Here's the critical part from another post i made on a YouTube video, having to do with getting the densest possible black from Brother printers:
"In Windows 10: Click on start, click on settings, click on devices, click on printers and scanners, and click on your Brother printer. Three choices appear; open queue, manage, remove device. Select manage, and from the menu on the left, select printing preferences (NOT printer properties). The Brother printing preferences applet appears. Select the advanced tab, and on the right hand side near the bottom, select 'other print options'. This opens the 'other print options' window: select density adjustment, UNCHECK printer default, and slide the tab all the way to the right (maximum density, AKA 6). Click on OK repeatedly to exit the labyrinth.
This buried setting instructs the printer to use all the toner it can possibly pack onto a piece of paper, and hope to make stick. It provides incredibly dense, black blacks which transfer with minimal, or no, pinholing."
Since I've been doing this, I've been able to get blacks so dense that they withstand ferric chloride with ease. I no longer have to go over traces with a magic marker to avoid pinholes.
I did have some luck. I was contemplating the purchase of a new printer, and I found a nearly new Brother HL-L2320D printer for sale on Kijiji.ca for $25 (it needed toner). I offered $20, he accepted, and I spent $69 for a genuine Brother high capacity cartridge. So my total investment was $89; I can buy the printer new for $95, but that's with a 'starter' cartridge which will last barely long enough to get you settled in. FWIW, I can genuinely recommend the Brother printer. It doesn't have wifi or a scanner or document feeder, but for a basic printer that can crank out some incredibly dense blacks, it is definitely the way to go.
The way I make boards seems to be evolving every day. Here's my current approach: print the image on standard magazine page stock, then laminate it with a copper board for about 24 passes worth. Then put the hot board/transfer paper sandwich on a flat surface, and roll it hard using a kitchen roller for about 30 seconds. Then I take the board/transfer paper and soak it for a few minutes... and the paper just falls apart, and doesn't hang onto the image at all. This seems to be a pretty repeatable way to get reliable circuits.
And, in closing, on a COMPLETELY unrelated note...
I just got back from a birthday party. My MOTHERS birthday party... where she celebrated her 97th birthday! Born this day in 1923. She's still doing well; her mind is sharp, her vision keen. She does tire easily, and she does use a walker... but she follows the news and politics avidly. She served in the Canadian Military during World War II, and she's like a walking history book. I feel tremendously blessed.
Take care folks - and keep rockin! >Charlie -
Thanks for the great post and all of the good replies. I checked out the web site you mentioned and they mentioned an obsolete laser jet as the best option. I would like to have a go at this technique however I do not want to shell out for a laser jet that will not work. especially if the newer laser jets are led-jets, that do not do the job. I looked at office works at a few budget laser jet printers but nothing mentioned in the specs about laser or led. Best regards to everyone love this forum, any advice greatly appreciated.
-
I did a 100 TQFP once with press-n-peal blue toner transfer.
It worked but was pushing things to the max.
Side etching was an issue, i put some solder on the narrow tracks too thicken them up a bit.