Pat,

     We divide the part into the four quadrants, and in each quadrant
     fan toward the corner of the part.  This makes for a horizontal
     and a vertical routing channel (like a plus sign) through the
     center of the part.

     Jon DeGenova
     [log in to unmask]


______________________________ Reply Separator _________________________________
Subject: [DC] Minimum routing layers for a 256 pin BGA part with 1.27
Author:  "DesignerCouncil E-Mail Forum." <[log in to unmask]>,          Pat
Paulson <[log in to unmask]> at Internet
Date:    5/13/98 11:59 AM


I'm working on my first design using a BGA part and I'm looking for any
ideas that would be helpful.  I'm using a 25 mil pad for the solder ball
with pin escapes (through hole vias) for each pad. These pin escapes are
placed in the same direction so the solder side of the pcb looks like the
bga footprint for de-bug purposes.

I guess this means I have to use 4 layers to route away from the part? Are
there any tricks that I'm missing? I'm ready to say the heck with pin
escapes at the part.  What techniques do other people use?  I'm using 6/6
widths/spacing.

Thank you for your ideas/help!

Pat Paulson
VTEL Corp.
[log in to unmask]

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