4 layer board done!
2007-11-26 by DJ Delorie
Got one done: http://www.delorie.com/electronics/usb-gpio/ The inner core is 1/2oz 32 mil DS. The two outer layers are 1/2oz 8 mil SS, taped on with 3M 7953 laminating adhesive. TT (Pulsar), FeCl etch, MG Liquid Tin. Lessons learned: * Keep track of which holes are which sizes on which layers. I got this wrong in a couple of places, and had to use an xacto knife to cut through the outer layers. There were a few places I drilled where I shouldn't have, but those were fixable. * My process "bloats" copper, so I need to print it shrunk to compensate. I had to "edit" the etch resist before etching, and still had some shorts afterwards that I had to fix. * I still can't manually iron on toner with any success. I tried the glossy magazine paper instead of the coated paper, just to see. It seemed like it would have worked, if only the toner had stuck to the board better. There's a fine line between "does stick" and "smears" that I keep passing through. I didn't try it with the laminator, as I was trying to use up some 1/16" stock. * How to do fast vias: Wrap solder around the board, to hold it off the table a bit. Cut off a few inches of bare wire wrap wire. Stick wire through hole, solder, cut, repeat. Flip board, solder all the little bits of wire sticking out. * Pin 4 is not ground on mini-B connectors :-(