The  default  via pad and hole size Protel uses is rather large,
a smaller via and hole size should probably be selected.

The  other  major factors would be the routing rules for:
- The spacing between the pins of the PGA socket.
- The trace widths.
- The clearance between the tracks and to the PGA pads.

If you've calculated these and you really are out of
routing channels,  you probably do need to add more layers.

With  200+ I/O  pins,  if even half of those pins are outputs,  and they are
switching all at  the same time,  or switching at high speeds,  you will
benefit  from  having Power and GND planes in other ways.  Less  noise,
less ground bounce,   better EMI,  etc.

Moving  the  GND/PWR  to  the  planes  (and  the  wider tracks probably
supplying them) will make routing it easier.

With a 200+pin PGA,  I'd want (you may even need) the planes.

---Phil

WV> Hello,

WV> I am looking for some info and help on a decent routing
WV> scheme for a 200+ pin PGA socket. I am using only a 2 sided board
WV> right now, but wondering if a 4 layer layout would be best.
WV> Customer wants to go low cost......

WV> Seems you run out of routing room from the inside pins to the
WV> outside ones. Not much room to drop vias in. 

WV> I thought I might have to pull out the center pins to put in
WV> vias, but run into the problems again, no routing room.

WV> Any suggestions or visual aids?

WV> Thanks from a new protel99 user!

WV> Leif
WV> [EMAIL PROTECTED]

WV> Posted from Association web site by: Leif Erickson







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