Vasile, 

> This sound interesting. Is not like any standardised 12 layer 
> stack I know (from 12A to 12L standard names).
> Correct me if I understood wrong. Your stack proposal is:
> 
> ------------ start sublamination 1
> 1-top
> 2-signal
> 3-PWR
> 4-GND
> 5-signal
> 6-signal
> ------------ end sublamination 1
> ------------ start sublamination 2
> 7-signal
> 8-signal
> 9-PWR
> 10-GND
> 11-signal
> 12- bottom
> ------------ end sublamination 2

Exactly.
Planes 2,5,8 and 11 are easy to impendance control.
6 and 7 should be carefully used due to EMI issues with 5 and 8.
Typical, we are using 6 or 7 as additional GND Plane and/or only for low
impendance static signals.
 
> What will be hapenning between layer 6 and layer 7 ? There 
> will be a great EMI there even layers 5,6,7 and 8 will be 
> routed using 45 degree and ortogonal schemes with as much 
> ground copper as possible.
> 
> Will be only three types of through vias (through vias per 
> sublamination, through and blind vias per stack) 1-6, 7-12, 1-12.

Yes. But the PCB house do not have to build blind vias (with the extra
costs), they only have to do standard vias, whcih became blind vias
after putting the 2 stacks together.

> I've guess is this one right ?
> http://www.ilfa.de/servicecenter_en/
> Are you with ILFA  ar an ILFA customer ?
> I'll try with my next design, I'm curious about prices.

I am a customer there.
 
> For example how much cost a 12 layer board as follows:
> 2500 routes,
> 2200 microvias/buried vias/through hole vias, min drill size 
> 0.127mm  (5mil), min route/isolation thickness 0.1mm (4 mil), 
> overal board thickness 1mm (~40mil), size 140x50mm ?

Just ask them ;-)
 

Best Jens

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