From the fabricators we use, I have been told to make sure the copper is
13-15 mils away from the drill, keeping in mind that the drill is always a
bit bigger than the finished hole size (maybe 5 mils?). So if that increased
drill size is a 2.5 mil annular ring in effect, and I am adding at least 13
to it, I get that my anti-pad has to be a minimum of about 30 mils larger in
diameter than the finished hole size (15-16 mil ring).

I am having trouble relating a "hard requirement" like that (from the
vendor) to the spec, and even more trouble thinking that an unplated hole is
really a board edge.

Do I really need to increase the anti-pads on my padstacks?

Jack

                -----Original Message-----
                From:   Gary Ferrari [mailto:[log in to unmask]]
                Sent:   Tuesday, September 21, 1999 7:53 AM
                Subject:        Re: IPC Specs - Errors?

                Obvious to us is that we require a
                minimum electrical space. We must also prevent the resulting
space from
                getting too small as to create a similar problem with the
AOI systems. We
                attempt to accomplish this by requiring a reasonable
fabrication allowance on
                each side of the hole. Granted, in fine line and space
applications, the
                spacing may become smaller than our 0.010 inch minimum. But
in more case than not, the result will be satisfactory.