8 layers:  Core + 3 sequential layers on either side
Overall thickness 0.020"


-----Original Message-----
From: Dwight Mattix [mailto:[log in to unmask]] 
Sent: Thursday, February 14, 2013 10:17 AM
To: TechNet E-Mail Forum; Wayne Thayer; [log in to unmask]
Subject: Re: [TN] Buried/blind/stacked via layups

At 06:44 AM 2/14/2013, Wayne Thayer wrote:
>On high density boards, they are generally built on a "normal" core, 
>then have microvia layers added simultaneously to top and bottom, one 
>layer at a time (also called "sequential layup").
>
>To increase density, microvias can be filled, then outer layer vias can 
>be stacked directly on top.
>
>Is it OK to do the same with the core layer vias?  Fill, overplate, 
>then stack microvias on top of them?

"It depends"

1. on the supplier. Some will no-bid.
2. On Min lines and spaces you expect for those layers. Minimum resolution will increase due to the increased plating and process complexity.
3. The buried via size and core thickness a fab is capable of will vary. Not just what they can accomplish in stack but what they can build that will be reliable in the stacked column of uVia to buried via.

What are particulars of stackup you have in mind?  Layer count, overall thickness, material, copper thicknesses, via/pad sizes 

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