Kai-Martin Knaak wrote: > On Tue, 29 Sep 2009 17:01:23 +0000, Michael Sokolov wrote: > > >>> I'm told that the OMAP3430's Package-on-Package configuration requires >>> at least six layers to get all the signals out. Ugh. >>> >> OK, that explains the need for a lot of layers. But how does the need >> for blind/buried vias arise? >> > > The balls of the BGA occupy most of the real estate available on top > layer. If all vias penetrate the hole stack, this occupation maps to all > other layers too. >
... and then you've covered all the area that would otherwise be available to run traces through. With a blind via, you can drop down to the next layer and get a little room to navigate. I haven't come across a situation that required a buried via, so I can't comment on that. Can't even guess, actually. b.g. -- Bill Gatliff b...@billgatliff.com _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user