Years ago, while taking a graphic arts course in college, I shot negatives of some printed circuit art (hand-drawn, optimized for broad traces and minimal etchant depletion, and ganged with a class project to avoid wasting film).
At the time, Radio Shack still sold negative-acting photoresist, in a spray can, and I made maybe as many as half a dozen of them (using a simple contact frame under direct sunlight for exposure).
I expect to actually need a bunch of the boards I designed (essentially dirt-cheap signal logic for model trains, on a 2-inch square card, based on 2N2222 transistors), before too much longer.
Looking around online, I find that 2N2222s are not only still readily available, but dirt-cheap. Single-sided PCB stock, and ferric chloride solution, also appear to be readily available.
But I also found that negative-acting photoresist spray seems to have fallen into a black hole.
Any suggestions?
All I see is some sort of adhesive film, on Amazon, with mixed reviews. I admit that the idea of washing soda as a developer (instead of the strong organic solvent that the Radio Shack spray used) is attractive, but some of the negative comments complain about very limited documentation, and the need to heat-set the film before exposure and etching. Anybody have any experience with that stuff?
Or would I be able to get decent results if I scanned my negatives, and then laser printed them onto the toner transfer sheets I've also seen on Amazon?
For that matter, given that I spend my Saturdays docenting at a printing museum, I could probably cut a stencil from my negatives, and silk-screen the trace pattern onto boards, for less than it would cost to convert my art to Gerber format (probably ruining the etchant-optimizations in the process).
But does anybody here have any experience with either the blue plastic photoresist film I've seen on Amazon, or with toner transfer sheets?
