General purpose photolith

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General purpose photolith

Postby Doug Coulter » Mon Aug 23, 2010 8:30 am

I have some needs for more general purpose photo-lithography than just pre sensitized PC boards. I need to make masks for sputtering and evaporation in vacuum, and for selective electroplating and chemical engraving. I have been playing just a little with a PVA-ammonium dichromate mix, but not getting the world's greatest results -- could be I have the wrong molecular weight PVA - I got the stuff they sell to make "slime" for school children, as it was what I could find. I'm not hooked on making my own, though, I just haven't found a commercial product that I can get that also works.

So, HELP! Anyone have a better clue than I what is good for some of these tasks? Has to be something I can get in less than 55 gal drum lots.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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Re: General purpose photolith

Postby johnf » Mon Aug 23, 2010 2:42 pm

Doug
many years ago when I ran the local university 300 level physics labs we had a thick film experiment for the students.
this involved the students hand cutting rubylith then doing a 10:1 photo reduction using a plate camera with lith film. this was used to expose Blue poly to UV and the blue poly developed in H2O2. The Blue poly was then laid on a silkscreen and allowed to dry. The mylar backing was removed when dry--and voila a very accurite stencil for printing of conductive or dielectric inks. Of course the blue poly could be stuck to anything you like as after developing it was like gelatine held on its mylar backing and dries to a hard layer. I seem to remember making test patterns that proved resolution down to 0.001", we didn't require better but i'm sure the blue poly was at least ten times as good as we needed.
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Re: General purpose photolith

Postby Doug Coulter » Sun Nov 28, 2010 5:57 pm

I think I finally found a source of photolith film, probably overpriced (all their other stuff is) here. I'm going to get some soon, I have a lot of uses for such a thing. Looks like they want to sell you a small heat/pressure laminator with it, but that doesn't seem like a huge obstacle to get going on things what wouldn't have a chance going through that machine. Hopefully the photo film has a light mask on it so you can work with it some in light before taking that off and exposing (like presensitized PCBs have).

I'll have to wait for first of year to do it -- I'm at the point where taking one more nickel out of my retirement fund kicks in a hugely higher tax rate -- not worth it, and I won't have to wait that long.
Posting as just me, not as the forum owner. Everything I say is "in my opinion" and YMMV -- which should go for everyone without saying.
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