Re: gEDA-user: Blind and buried vias?

[Carlos Nieves Ónega <cnieves@xxxxxxxxxx>]

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



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