Hi, sorry you downloaded an .exe somehow, the Sendspace link usually just works. Thanks for copying the image files elsewhere, very kind.
The paper is 90gsm as I said, and no it's not crinkling. The crinkly pattern is absolutely a function of how the etch resist is deposited. The issure really seems to be etch resist's own non-uniformity. I tried transparent film before, and the same effect results. The patterning does not tie up with either type of transparent material that I've used.
For now, I'm tightly taping the transparency to the board, with the artwork side against the photo resist side to avoid diffusion. I'm using a Mega LV202E 2-lamp exposure box, I'm pre-heating the lamps for 5 mins before use, and the foam-lined lid squashes the job flat against the glass.
Thanks,
Matt
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---In Homebrew_PCBs@yahoogroups.com, <bitsyboffin@...> wrote :
I put your images on imgur, that sendspace tried to download some exe to me the first time, dodgy as..
http://imgur.com/0kyPB0W
what weight of tracing paper are you using? It looks almost like it's crinkling or non-uniformity in the paper coming through. The heaver weight, the more "stable", I use 110gsm (but I also use Dry Film resist, not pre-coated boards).
Also how are you clamping the artwork to the board, and what sort of light-source are you using.