Hey all, Has anyone got any experience using either laser/toner transfer or inkjet transfer film to produce PCBs? I'm looking at the iron-on inkjet ones as they seem to be the cheapest way of producing a board. I'm looking at producing a one off PCB for an up-coming electronics project as point-to-point will just be too painful this time. To save space, the layout is basically 9 small circuits which are to be stacked atop one another with spacers. Each card is fairly fiddly so unfortunately etch-resist pen isn't too feasible either. So, I'm wondering how reliable these methods of PCB production are, as there's no way I can afford to get it made properly! The whole thing fits onto a 220x100mm board, which will then be sliced into 10 sections (one is just an offcut). If they are reliable, it means I can get the board made pretty cheaply... the most expensive thing in the whole project will be the transfer film, in fact. Opinions/experiences? Cheers!
I have not personally done it, but a buddy of mine has. Took him 2 trys and 8 hours to get it right finally. From what i've heard, using UV light on photo resist copper is the better method. You can buy copper with photo resist already on it, or buy spray photo resist to spray on the copper, but from what i've heard the copper with the stuff already on it works better. Again, this isn't first hand experience, only what i've heard from people at school and at work. good luck, and i'd like to see your results.
Photo-resist is the best method, I personally use Iron on toner transfer, using glossy magazine paper with excellent results (Ive been able to do a board with TSSOP packages which are .65 mm in lead pitch) I use cheap copperclad from electronics goldmine, clean it with scotch brite, and then acetone. Tape down my top side, mirrored, drill my index holes, tape on the bottom side, Iron the crap out of it with a iron + ironing board, then soak off the paper. Touch up the board with Sharpie (usually doing the large fills in heavier to make sure they stay nice and heavy) and then etch, using FeCl. However I'm changing over to Ammonium persulfate, but have yet to make a board with it yet. A baking soda solution neutralizes the FeCl quite nicely. (to stop, the reaction and etching the board, not to make it safe for disposal) Soon you'll go from hating SMT stuff to loving it because you dont have to drill holes, and if you can keep it all single sided, no second side to line up either. SOIC, SOT-223, 1206 sized passives, all nice and easy to solder.
I normally develop my PCBs using photo sensitised boards, but the toner transfer method can work quite well. I used to use HP glossy photo paper which seemed to work pretty well, though the effort is so much more compared to what I'm now used to... Ammonium persulfate works very quickly in my experience, and doesn't stain everything orange, although I've gone back to using ferric chloride as my supplier ended up doubling the price.
*nods* I'm sure photo-resist and UV is by far the best way, but a bit out of my price/time range at the moment. Price as the UV exposure boxes are around a ton to buy, and time as I don't have time to build one at the moment . (Actually, I suppose I could enquire if the electronics engineering department at uni here has any facilities I can borrow .. seeing as I may need an oscilloscope too at some point, so would be good to have friends there ). Looks like that toner transfer is promising, all I really need is a pack of paper and some FeCl, might give that a shot (as the inkjet/toner transfer film are hella-spensive!) Cheers
Haven't done it myself. But a friend of mine did a few boards. Just using some photo (glossy) paper he had lying around. The results were extremely good.
i also use the toner transfer method, cheap as hell. i print the artwork on a piece of paper using ink jet printer then make a run to a photocopying store near my house and just photocopy the paper on a sheet of transparency, iron on some copper and it comes out nicely most of the toner is transfered to the board this method saves you the need to soak on water and remove paper sludge since there is no paper!!.
New Trick I do toner transfers with 0.50mm (0.020") traces, from drawings made in MS Paint, printed on ordinary paper. If you think that's bad, I can also do the same thing by hand (see bottom) To the point, this weekend I found an awesome way to fix gaps in bad transfers, which I haven't seen anyone else note. (no sharpie required) Wiggling a clean 15W soldering iron across the gap melts the toner and fills it in. I've recovered transfers that had huge gaps, and in general this trick can improve narrow traces and incomplete/misshappen pads. -It doesn't spread as well to where toner never met the surface of the pcb during ironing, which can be a good thing, but it works like magic for spots where toner rubbed off. -If close traces run together, you could use a needle and straight edge to fix them before or after etching. (if done before etching, reheat with the soldering iron to mend spots where the needle may have "chipped" off toner) -Instead of a spongy ironing board, I use a small wooden panel with an old cotton shirt over it. The firmness makes it easier to apply force evenly, the shirt keeps the wood from burning. -I've got another extra step in my technique. Before applying the transfer, I set the cleaned PCB in FeCL for 5-20 seconds, rinse, dry and then iron it on. I've read that the microscopic pits formed by slight etching can help things stick better, like ink and probably toner. -I clean the toner off with fine grit sandpaper, scotchbrite/brillo-pads and alcohol. This works well enough that I've never needed to use acetone. _____ The method of doing it by hand is the opposite of using a sharpie by itself, for those large DIP parts. Before I knew about toner transfers, this was the only way I could etch boards for SMD parts. I use a sharpie to cover the entire board with ink, which takes a while. Then I carefully lay an SMD part down, scratch just between it's pins, take the part away and then fix up those marks with a straight edge and needle. Because it's a subtractive method, as opposed to additive (adding ink) it can make extremely compact designs with minimal etchant use and maximum trace width. It can work for really small things (below the effective resolution of laser printers) but it's a skill that takes practice. *I've never tried using a sewing needle, per se. There are small fine pointed tools that come with some drill bits, and radiosack sells a generic xacto knife which comes with pointed tips in addition to blades. This method doesn't look very professional, unless you've got great penmanship or a lot of artistic skill. I once did a 144 pin TSOP to DIP adapter board for a Xilinx Coolrunner II, it took six hours for me to notice I cut the PCB too small. I finally ran out of room to run the traces and gave up on it entirely. When in doubt, it's better to waste copperclad material.
I find that the UV method works best. Just get some pre-coated PCBs. And you don't need a UV box to develop the design. Just find a sheet of glass, put the printout on the glass, and the PCB behind that. Then you just put it in the sun for a couple of minutes. I have done this many times and it works great!
The new issue of Nuts & Volts has an article on making SMB with laser printers. If you can't find the article, let me know and I will scan it for you. The boards came out really nice for using the transfer method.
I have had good results using plain paper with the toner transfer method, iirc i got .006" or.007" traces reliably There should be a guide I typed up somewhere on the forum, you could also try searching, there are a few good guides out there
Hmmm, have you tried it with the glossy paper too? That's what all the guides seem to recommend, I suppose there must be a reason (actually I think I read on one of them that the surface coating makes the toner come off at a lower temperature or something)
The aim is that. after ironing, the copper-toner adhesion is better than the paper-toner adhesion, so either glossy paper (with little keying for the ink) or a paper that goes very weak when wet should suit. I've heard the backing sheet from self-adhesive labels also works well. You can buy the Press 'n Peel paper which may be similar, though it's fairly expensive. In the days when I worked for a firm producing copper-plated steel strip (for Bundy brake pipe) we used ammonium persulphate to strip the copper off samples to check the copper thickness - clean and fast.
The nuts and Volts article suggested using transparency film with plain parer to protect it when using the iron to transfer. The toner does not adhere to the film as well as it does to paper and melts very well. Also if your printer has a transparency setting then it should lower the temperature of the fuser slightly to avoid melting the film thus allowing the toner to transfer better. By the way if this is to be front mounted PCB like a SMB don't forget to flip the image horizontal or the transfered image will be backward.
