Help wanted with toner transfer (and perhaps a discovery)

[grumpydoc]

Slightly long post, sorry.

One of the "goals" I set myself when getting back into a bit of electronics was to be able to produce at least single sided and ideally double sided PCBs.

Many years ago I built myself a UV light box and, although I managed a few serviceable PCBs the results were never very good. Unfortunately the light box seems to have fallen victim to my father "tidying up" some of my old stuff so I thought I might try my hand at the "toner transfer" method. I wanted to buy a laser printer even if I wind up using photoresist as it looks like inkjet ink doesn't work terribly well to mask UV in any case.

So, I bought a Brother HL-2250DN, mainly because it was the cheapest networked mono laser I could find. It also works well with Linux which was essential - in fact it looks to be quite a useful little printer which understands PCL6 and even PostScript (much to my surprise).

So, here's my first effort - now don't laugh! I know I'm some way from flodins' double sided, through hole plated, solder masked perfection but we all have to start somewhere. For scale the four pads in a rectangle top left are the corners of a 14 pin DIL OCXO module (oops, I've just spotted my spelling mistake on the board).



Considering it's a first attempt I don't think it's a disaster

OK, first the "discovery".

I've read several sites describing the technique for toner transfer - all mention using glossy paper - either photo paper or even magazines. All talk about soaking the paper off (and how it takes ages). Some mention the special paper you can get which is made of sugar or some such to dissolve easily. To be honest it all seemed like a bit of a faff.

So here's what I did - I took some self adhesive printer labels (2 A5 sized on an A4 sheet) and carefully removed them from the backing paper, then threw them away. I then stuck the backing paper in the printer and printed the foil pattern on the glossy side of the paper - this is the side the labels were stuck to.

Then placed it toner side down over a cleaned PCB and using an iron set to about 200^oC ironed over the pattern for a minute or so, then peeled the paper away leaving the toner on the PCB. No water, no rubbing, no faff

OK, there were a few pin holes in the ground plane but as I said its a first effort and I have to play with the print density and quality to see if I can get more toner on the page. I also need to experiment a little with the iron temperature and pressure. Some of what looks like pinholes in the photo is actually residual toner BTW.

Also its a bit thin and has a tenancy to jam the printer - especially if the edges are curled. This is why you have to remove the label carefully - pull too fast and the backing paper just curls up (it's also best to remove from the edge towards the centre). Initially I tried the single sheet feeder which worked fine the first time, but jammed  the next two - in the end I just put a sheet in the main tray and that was fine.

I suspect that pressing a few sheets flat under a ream of paper would help.

So - questions

Has anyone else tried this type of backing paper? It seems to be ideal for toner transfer as the waxy side will take the toner during printing but it doesn't adhere too well so it transfers pretty well to the PCB. I can't find anyone discussing using it but I can't be the only one to have thought of or tried using it. If you have tried it did you stick with it or abandon it to photo paper or the specialised transfer paper? If you did abandon it what were the problems that couldn't be solved.

What size pads do people use for general through hole components. Sorry, I know this is really basic - I used a 0.1x0.06" pad for the OCXO (and intended to keep with that for DIL packages in general) but it looks too small. The circular pads were 0.08" which is a bit better but still look a bit small. I plan on using an 0.8mm drill for most holes.

What track widths/spacings are achievable with toner transfer? The tracks are 0.02" which is probably fine but the space between them and the ground plane is 0.01" which might be a bit too thin. Surprisingly (since there is an area which looks shorted) none of the tracks did wind up shorted to ground. Possibly I pressed a bit too hard and squidged the toner a bit but I think I need a bit more space here.

What do people use to get the toner off the PCB? I tried IPA, acetone, white spirit, and ethanol. In the end it had to be some 800 grit wet&dry and some Cif - nothing would dissolve it.

[c4757p]

My usual DIP footprint has 1.2mm circular pads, so about 0.05in. I usually keep to 16 mil traces and spacing but can do 8 mil if I pay close attention to that area of the board when doing the transfer (I've got no problem doing finer-pitched chips like SSOP and SOT-23-6). I like to use thin magazine paper - cheap, works really well, and comes off very easily (it's very important that it comes off easily, otherwise it's too easy to rip traces). Usually, I fold it over a piece of standard printer paper to make it thicker and avoid jamming the printer. My toner dissolves in acetone just fine, though I suppose if it didn't I'd probably use steel wool. Try lacquer thinner, maybe?

[Alana]

If thats your first board its good, even very good.

Questions:
1 - no, i use chalk paper recommended on polish EE board elektroda.pl - but not by parameters but by nickname of reseller on allegro.pl web auction service. Since i got it i never had any problems with toner transfer. Paper removal - soak it up in warm water. Sometimes i add vinegar or other weak acid to help remove chalk that may be left on PCB.
2 - all my protel libraries have round pads 80mil in diameter or bigger but sometimes when i have to squeeze track between 2 pads i go to 80x60 ovals, pads smaller than that tend to unstick from pcb while soldering
3 - tried 15mil track, 15mil space - 100% success, i should be able to go down to 10/10 spacing but i haven't had need for this
if you pour ground like this I'd go for bigger spacing between ground plane and tracks - at least 15-20mil
4 - my way to remove toner is to rub it off with some toilet paper soaked in nitro solvent or better acetone. This is basically mechanical removal because toner seems to be poorly soluable and solvents keep it from sticking to copper-free places on the board.

[poorchava]

Even short parts with 8/8 spacing can be done. It's always better to have too small clearance than too smal clearance. If tracks fuse with each other you can always separate them with a scalpel. On the other hand replacing a track of which some part is missing is quite hard.

I also tend to use hatched polygons, because my laser printer tends to "dilute" toner on bigger surfaces which results in porous copper plane. For removing paper I use pure vinegar.

P.S.
I'm currently in process of moving to photoresist method. Just waiting for photolackquer and NaOH to arrive (and one missing potentiometer for a thermostat that I don't have).

[Strada916]

grumpydoc

The waxy paper is called silicon release paper. Its used for most if not all stickers or vinyl printing. You should be able to buy it by the roll from most drawing supply outlets or people who supply or offer services of laminating posters and screan printing, or even some piture framers.
Good luck
Nice job by the way.

[grumpydoc]

The waxy paper is called silicon release paper.

Ah, that's handy to know - I tried looking to see whether it could be bought separately but not knowing what to search for had had no luck. I can now see a few places to get A4 sheets at £0.10-£0.15 per sheet shich isn't too bad (adding postage might well double that figure though). However if using stuff which comes with labels attached works it's essentially free - I wouldn't normally throw the labels away but keep the backing when I use the labels.

If thats your first board its good, even very good.

Well, not my first PCB. As I said as a teenager I did try some photoresist ones with a home made UV lightbox. However I think that the illumination was not that even and I never got anything that was an effective blocker of UV as the results weren't very good - in fact I don't think I ever made a useable PCB that way. I did manage some with resist transfers and managed to do a few recently when I found my old stock of bits. Generally transfer for the pads then permanent marker for the tracks. That has resulted in a few workable boards but it's not terribly neat.

Edit: It is, however, my first attempt at toner transfer

...tried 15mil track, 15mil space - 100% success...
...usually keep to 16 mil traces and spacing but can do 8 mil...
...Even short parts with 8/8 spacing can be done...

I think I'll aim for 20/20 to start with and aim for something a bit smaller with time - perhaps down to 10/10 should be doable without too many problems. If I get good at that I'll try 8/8 The margin around the current traces was 10mil and has mostly worked OK - just the gap around the rightmost trace which has got a bit thin. I think 10mil is too fine for this board, however.

...all my protel libraries have round pads 80mil in diameter...
...My usual DIP footprint has 1.2mm circular pads, so about 0.05in...

OK so the pads are probably about the right size. I'll know better when I try to solder them.

I'm probably not going to drill and populate this board as it stands but will redo it with 20mil gaps around the traces (the gap around the pads is 20mil) and slightly larger pads at the bottom since the strip connector needs to be soldered to the copper side of the board.

[SeanB]

Nice idea. That brother Printer is a rebadged HP/Canon printer, so of course it works well with Linux. HP firmware is good with Linux, Canon can be junk, even on the same print engine. Different design teams and terrible drivers and buggy as anything. With the cartridges check out the price of the Brother, HP and Canon ones, one will be cheaper , and you can get good refills on them as well. Only issue is that the printers come with the "starter" cartridge, which does around 500 pages until it is empty, and then you find out the full fill cartridge actually costs more than the printer.

[grumpydoc]

Printer is a rebadged HP/Canon printer, so of course it works well with Linux

I've no doubt you're right but can't see anything in the Canon or HP stable which looks to definitely be built on the same platform. The Ricoh SP1210N is clearly the same printer without the duplexor and with slightly less memory - 16MB vs 32MB - and consequently slightly cheaper (rats!). It's very possible that there are others which share the same internals but have different cases.

Only issue is that the printers come with the "starter" cartridge, which does around 500 pages until it is empty, and then you find out the full fill cartridge actually costs more than the printer

Yes, that is pretty annoying, but almost all manufacturers do it especially at the cheap end of the market. The 1100 page cartridge is about £34-£40 and the 2600 page cartridge is, indeed, almost the price of a new printer at nearly £60.

The killer will be when the drum reaches the end of its life - it's rated for 12000 pages - at that point drum plus toner will be more than the price of a new printer. This is hugely wasteful of resources because no-one is going to keep one of these going past the need to replace the drum.

[ecat]

I've used silicon backing paper and it works very well, with one caveat.

My method of printing is to place a sheet of ordinary laser copy paper in the manual feed tray and print the pcb image using the straight feed path (it comes out the back of the printer not the top), this is the carrier sheet. Cut a piece of backing paper oversized, align over the printed image glossy side up and use a strip of masking tape (or cut up one of the labels) to hold the leading edge of the backing paper in place. Keep the tape clear of the image of course. Put the sheet back in the manual tray and print the pcb again, job's done.

The caveat? The backing paper is totally non-stick. The masking tape will only just hold it in place during the print and the toner doesn't so much stick to it, it more just sits on the surface staying in place by <shrug> I don't know, static? Force of will? The grace of the Seven Goddesses? Whatever, it is very easy to spoil the print with only the slightest lateral movement on the pcb once the two are pressed together.

Laser printers can be so cheap to run. When I bought mine I picked the cheapest office grade printer with a full, real cartridge I could find. About £120 and after six years of pcb and general printing the toner is still about 80% full!

[grumpydoc]

Quick update on this.

I bought some silicon release paper to try. Pretty much a non starter as it won't feed through the printer, much too thin.

Sadly the label backing paper didn't hold to its initial promise.     It does work well for thicker tracks - 20-30 mil or more but I just tried a "work in progress" with 15mil tracks to see how it printed and I couldn't get a decent print; the tracks are just too thin to stay put when the paper goes through the printer's fuser.

It's a pity because with a good print it transfers well with no need to soak the paper from the PCB - looks like I'll be trying the more traditional glossy magazines or glossy laser photo paper next.

Live & learn

[baljemmett]

I bought some silicon release paper to try. Pretty much a non starter as it won't feed through the printer, much too thin.

Have you tried cutting a section out and then taping the leading edge to some bog-standard printer paper?  That's how I use the blue press'n'peel stuff, to avoid wastage.  Might depend on your printer's feed layout though.

[grumpydoc]

Have you tried cutting a section out and then taping the leading edge to some bog-standard printer paper?  That's how I use the blue press'n'peel stuff, to avoid wastage.  Might depend on your printer's feed layout though.

Even the label backing paper caused problems more times than not - in the end I found leaving a 1.5cm strip of the label at the top helped it feed through pretty much 100% of the time. The same worked for the silicon release paper but there, of course, I had to apply a strip (which didn't stick all that well) which also worked but was much more fiddly.

The result with fine features was much the same.

It probably doesn't help that a couple of paper jams have wrapped sticky label round the fuser roller - I wonder whether there is any adhesive residue that might be causing problems lifting the thin tracks. It still works fine printing onto paper and in any case any technique is only of value if it works with a printer that has bedded in a bit and the odd paper jam is going to be a fact of life.

Not to say the results haven't been encouraging. This is what last night's efforts looked like for the transfer - although I'm not intending to etch it at the moment - I was just playing around with a modified laminator for the transfer.



The border is actually 10mil but when I tried with a PCB using 12.5 mil tracks they didn't stay put on the backing paper - well most did most of the time but I couldn't get a print good enough to transfer and some were complete garbage.

An earlier run of the board above etched, tin plated and populated looks like this:



So there's definite progress being made

[SeanB]

If there is residue on the fuser try using the cleaning mode ( either in the driver or in a menu on the printer) available on many newer HP/Canon printers.

[grumpydoc]

If there is residue on the fuser try using the cleaning mode ( either in the driver or in a menu on the printer) available on many newer HP/Canon printers.

I don't see a specific option, running a few sheets of plain paper through seemed to improve the print on the little OCXO module board.

What i did see on the printer html interface was a media type option which isn't available through CUPS (might be in the Windows driver but I'm normally using a Linux machine). This has "plain paper", "thick paper", "thicker paper", "thin paper" etc. I suspect this will control the fuser temperature so I can try that to see if it makes a difference. I'm assuming that going for "thin paper" will lower the temperature and it does look as though the toner is just melting and being smeared across the page.

[SeanB]

Look for a cleaning option in the menu, normally under service in the menu. If it has a web server in it it has a cleaning mode. The paper option things adjust the fuser temperature and the paper feed speed settings, along with the jam detection.

[grumpydoc]

On the index page I have:

• Home Page
• View Configuration
• Maintenance Information
• Find Device
• Printer Settings
• Administrator Settings
• Reset & Test
• Network Configuration

"View Config" and "Maintenance Information" just show printer info. Not totally clear whet "Find Device" does. "network Config" has some interesting stuff but not cleaning options and "Printer Settings" has paper type, default resolution etc but again no cleaning or service menu. "Administrator Settings" just sets the passwords.

The paper option things adjust the fuser temperature and the paper feed speed settings

Yes - setting "thin" was worse so I tried "thicker" which slowed the feed speed considerably resulting in an almost usable print. Unfortunately I'm now out of labels for playing around with so this will have to wait for a few hours.

[IanB]

I just read this thread, I hadn't clicked on it before. I found it interesting as I recently bought a Brother HL-2270DW. I really like the printer. I got it because Brother have a good reputation for reliable printers.

One thing I wanted to mention though, is that if you value your printer it is not a good idea to feed various random things through it that are not designed for laser printing. Apart from gumming up the works it is possible to get toner, chalk or other stuff in places were it shouldn't be, which will mess up the print quality. For example, it is even not recommended to use inkjet paper in a laser. The inkjet paper may be more subject to curl, and may have chalky filler substance to help absorb the inkjet ink and prevent smudging. Laser paper will have a smoother, less porous surface and no chalk filler.

Even if you don't think you need good print quality, it will affect the circuit boards you try to make if it leads to gaps or shorted tracks.

[grumpydoc]

...if you value your printer it is not a good idea to feed various random things through it that are not designed for laser printing...

Agree but this printer was bought for experiments with toner transfer - I don't especially want to break it but would not loose sleep if I needed to buy a new one once I'd figured out what works and what wrecks the printer