El mar, 29-09-2009 a las 09:38 -0500, Bill Gatliff escribió: [snip] > The latest generation of BGA parts have so many pins on the package, > packed so tightly together, that it isn't possible to get all the > signals out of the chip in two layers and still have the traces large > enough to meet specs. A sophisticated chip in an 0.5mm-pitch BGA > package, like the OMAP3430, is an example. I have never seen the > underside of one of these guys, but I bet it's pretty scary. > > I haven't had to lay one of these boards out myself yet, thankfully! > :) I'm told that the OMAP3430's Package-on-Package configuration > requires at least six layers to get all the signals out. Ugh. >
Don't know for 0.5mm and 0.4mm pitch packages. For CUS package (0.65mm pitch) it needs just 2 signal and 2 power layers without blind, stacked or buried vias. See: http://focus.ti.com/general/docs/litabsmultiplefilelist.tsp?literatureNumber=sprab13 Regards, Carlos _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user