aLternatives to toner transfer paper?

[sir_modulus]

I've read through the forum and came up with some results for alternatives to toner transfer paper. I am confused. Could someone tell me which ones can be used with Ammonium Pursulfate Etcant (not photo-etching)? Thanks.

P.S. Which ones work the best?

Thanks,

[Paul Perry (Frostwave)]

The object (whether you use PnP, or the backing sheet from sticky lables, or clay coated magazine paper, or transparency paper, or "photograde" printer paper) is just to get the toner (from the photocopier or laser printer) to stick to the copper board and prevent the etchant getting to it.
Once you have the toner stuck to the PCB, it doesn't matter what etchant you use.
I personally prefer persulphate, but it has to be warm to work.

[Mark Hammer]

As Paul points out, as long as the copper surface is covered in a stable waterproof manner in those areas where you want to retain copper, it doesn't matter what etchant you use.  It is a reasonable concern, though, to wonder if there are chemical incompatibilities between some board-coverings and some etchants.  As it turns out, none of the usual stuff we use is problematic.

"Work best" needs to be qualified, and broken down into dimensions.

1) Easy to tell when you've transfered it over.  For a bunch of reasons, things that use a plastic surface are generally good at providing visual cues about what is successfully adhered to the board and what could still use a bit of ironing.  I'm certainly pleased with the pricing of paper transfer methods, and have gotten used to ironing it on, but it is still much harder to judge the status of the transfer when paper is involved than when plastic is.

2) Resolution.  Transfer methods always involve a substrate/backing and a detachable emulsion/coating of some kind.  By this means, when the board has cooled, you can pull off the substrate and some stuff will come with it while other stuff stays behind on the board.  The emulsion (transferable coating on the substrate) varies in its resolution.  As a fibre-based product, the resolution of paper will be poorer than that of plastic-based products.  As the coating tears away from the paper backing, it does not do so crisply, reducing the precision of the traces.  Paper also needs somewhat wider traces for the toner to adhere strongly enough to the copper to be able to pull away.  PnP is not perfect, but the difference between paper and plastic is like 1024x768 vs 640x480.  The latter is absolutely fine for some things but not for others.  My own rule of thumb is that if the layout has traces that run between IC pins, it has to be done with PnP or some non-paper method.  Otherwise, the odds are too high that the edge-fuzziness that comes along with paper-based methods will leave you having to draw in that trace.  For anything that uses discrete transistors, though, I have not personally found any layouts yet where I would be reluctant to use paper-backing methods.

ALL toner-transfer methods benefit from having a clean bright smooth copper surface and a flat, solid, smooth surface underneath when you go to transfer.  The toner needs to adhere strongly to the copper and any grime between the copper and toner (corrosion, dust, "finger juice", etc.) impairs that.  Similarly, the heat needs to be applied as uniformly as possible and smooth supportive surfaces underneath the board assist that.