Title: "Iron-On Patterns"
Published: Jun 1993
Author: Glenn Elmore
After a lot of effort, I had limited luck with the TEK film [TEK-200]. The biggest problem was getting good adhesion of the toner from the copier or laser printer to the film. I tried many different machines but much of the time sections of it would either fall off or smear or else come off when I peeled the film away. Getting the iron-on phase right takes some learning too. I was successful in making some moderately critical circuits, edge-coupled microstrip bandpass filters and such, however I finally gave up when I found a better way.
I got some of the new Pulsar material that is now offered from quite a large number of suppliers. It is basically paper with a transparent water-soluble carrier onto which you copy or print the toner. You then iron it on as with the TEK film, but rather than peel away the film you just put the whole works, PC board and all, into water. The carrier then dissolves and paper backing comes off leaving all the toner on the copper. This works much better than the film and also gets you from design (or scan) to resist with fewer steps much of the time. I can usually go from the PC-board layout tool on the computer to an etched board which is ready to have parts loaded in under an hour. About the most important aspect of this is to have good toner which gives saturated black on paper. I used standard paper toner which came with my HP laser printer - and it isn't even a new cartridge.
I've used the process to generate fairly width-critical circuits, 90-degree microstrip hybrids and complete image-reject mixers at 1200Mhz, with quite good results. I even managed to get reasonable yield on some very narrow lines which happened to be on one design: one pixel wide at 300dpi which amounts to .003 inch. I don't recommend trying to do fine lines this way, but it gives an idea of how well it all works.
I think that the cost/effectiveness ratio is much better with this process than with anything else I've tried. A bunch of people appear to handle [resell] the material.
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