No one uses 8 mil traces anymore, especially on a design like that.
You gotta get two traces between pins....

(just one lowly designer's opinion)
Jack

                -----Original Message-----
                From:   John Parsons [mailto:[log in to unmask]]
                Sent:   Friday, December 17, 1999 11:06 AM
                Subject:        Need Design Advice for BGA (?) Socket

                Seasons Greetings!

                We have just received a design from a customer which
utilizes a
                560 pin BGA(?) socket.  Here are the details;

                -6 Layer board, 4 routing layers 2 plane layers
                -Socket is 5 rows deep
                -Current configuration - 23mil hole on 30mil pad on 50mil
grid
                -Routing out with 8mil traces on primary, secondary and two
inner
                layers

                We have told him that his hole to pad ratio is too small for
us to
                manufacture.  Currently our minimum spec is 6mil annular
ring (pad
                dia - finished hole size/2) for outer layers and 7.5mil for
inners
                (although we will do 6mil on inners if we have to).

                He is telling us that he cannot design within these
constraints.

                What are others doing for this design?  Are you routing out
on
                outer layers?  We cannot seem to put our hands on another
                sample design from our files (although I know they are some
in
                there somewhere).

                Regards
                John Parsons
                Circuit Graphics Ltd.

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