On Board Fiducials: Quick guidelines we use - 1. Place them in all four corners of board. At least 2 diagonally. 2. There are light fiducials or dark fiducials - Light fiducial is 50 mil pad (typically used) with a 20 mil min. non-interference area (via and etch keepout) Dark fiducial is a "donut shape" where the "hole" of the donut is 50 mils and the "donut" is 20 mils. 3. Brd Fiducials should be placed on both top and bottom of the board. 4. Fiducials should not be covered with soldermask. ( 100 mil opening min.) *Any circular pads (i.e. vias, component terminals, etc.) that are between .040 - .070 should be kept .200 away from fiducials, OR changed to be a square pad so that the vision system (or the operator - not sure why) doesn't "see" the wrong pad. I haven't connected them to gnd - we leave them as brd symbols. No problems or requests to do that. As a rule, we keep them approx 200 mils in from the edges of the board - or align them with existing mtg. holes. Tom Kavendek Lucent Technologies 700 Mountain Ave. Murray Hill, N.J. 07974 [log in to unmask]