Brian, I'm currently debugging a 6 layer board with a 676 pin bga. I actually needed only 316 of the i/o pins, and I simply avoided the deep rows of the bga. With only 1 trace between bga pads, I can get the first two rows (counting from the outside in) on the top layer, and using thru vias I can get the next two rows (equivalent, you have to avoid blocking the planes with adjacent clearance around the vias) on the bottom (or any other layer). This is a low volume product, not very (parts) cost sensitive, so I can justify the larger package (It's actually a trade off with a more expensive board). It was my first board with ad2004, and I did make use of the fpga pin swapping (much easier than with 99se, but still not simple)
Richard At 04:14 PM 6/21/2006, you wrote: >Ok, I'm still using P99SE. > > I need to upgrade an existing project with the main IC being a 240 QFP, >going to an Altera 484 pin, 1mm fineline BGA, however, there are some parts >under the chip. > > My PCB is only 6 layers. I've never done blind/buried vias before in >protel. How should I configure protel to handle the blind-buried vias under >the BGA pads. Am I attempting something that shouldn't be done? Can some >BGA pads just be pads with no holes at all without upsetting the mounting? >Is there any good reason to switch to microvias? > > >____________ >Brian G. > > > >____________________________________________________________ >You are subscribed to the PEDA discussion forum > >To Post messages: >mailto:[email protected] > >Unsubscribe and Other Options: >http://techservinc.com/mailman/listinfo/peda_techservinc.com > >Browse or Search Old Archives (2001-2004): >http://www.mail-archive.com/[email protected] > >Browse or Search Current Archives (2004-Current): >http://www.mail-archive.com/[email protected] Cheesecote Mountain CAMAC, 24 Halley Drive; Pomona, NY 10970 voice: 845 364 0211, NEW fax: 877-840-0023, Skype: cmcamac, www.cmcamac.com ____________________________________________________________ You are subscribed to the PEDA discussion forum To Post messages: mailto:[email protected] Unsubscribe and Other Options: http://techservinc.com/mailman/listinfo/peda_techservinc.com Browse or Search Old Archives (2001-2004): http://www.mail-archive.com/[email protected] Browse or Search Current Archives (2004-Current): http://www.mail-archive.com/[email protected]
