>I've already done such designs on 12 layers (0.5 and 0.4 mm pitch)
>but the price for PCB manufacturing was huge so my intention
>is to avoid blind microvia and if possible buried too... I'm
>wondering how can be done.

I don't think you can avoid blind and microvias for this number of balls, 
and the potential frequency of operation. PCB cost is something you have to 
have to deal with these. 

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