Yesterday while I was at the TechShop experimenting with the laser cutter and talking about solder stencils with other folks, this idea came up:
1) Take 3mil brass sheet, and paint both sides with "machinists' blue stuff" -- I'm not sure what it's properly called, but it's a blue paint that they put on metal so that they can scribe layout marks. 2) Slap it in the laser cutter, and print the paste layer on it with just enough laser power to blast away the blue paint. (The CO2 laser is the wrong wavelength for cutting metal, it just reflects off.) 3) FeCl etch. The blue stuff is a resist. You now have a paste stencil. Anyway, DJ, I've looked over your web site where you do basically this with the toner transfer method. Got any comments? Topic two: I've been trying to get a process that makes stencils in 3 mil drafting mylar. I've got a usable stencil with relatively fine-line parts, but it was more than a little tweaky. There is a fine line between cutting through and getting goo because the material is so thin and prone to melt and stick to itself. I ended up printing three the paste layers with 3 different bloat settings, converted all of them to dxf, and merged the drawings and cherry-picked the "best" image for each footprint. I see where Grafix makes essentially the same material as drafting mylar, but coated with a "secret sauce" specifically designed to keep it from sticking to itself when laser cut. I need to get hold of some samples of that. It looks like they have a $100 minimum order on this material. I'm guessing that Pololu and the other places that cut cheap plastic stencils for you are using this stuff. Third wacky idea: TechShop has one of those PCB mils. I suppose you might do a stencil in sheet brass with it, but I'm not sure it can cut a fine enough line. I need to find out the specs. Comments? Ideas? -dave _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
