The controlled depth method has the advantages of not needing to plate
multiple sets of panels and you don't need sequential lamination.  

However, it is more difficult in my experience and could wind up costing
more than sequential lam if the processes aren't controlled well.  Is
the drilling equipment accurate enough to control the depth?  There also
cannot be any variation in table height across the panel or you will
drill too deep in some places or not deep enough.  Plating is another
problem.  If the chemicals just sit in that hole you will have a lot
voids.  A lot of banging on the rack and agitation are necessary to keep
the chemicals flowing in and out of the hole.

I'm no expert.  I'm just throwing out my 2¢.

Andrew Buonviri wrote:
> 
>   My company is looking to design a multilayer PCB with blind vias. Another
>   company will do the actual fab. I've heard there's more than one way to
>   do blind vias: either controlled depth drilling or fabbing and drilling
>   two halves of a board separately and sticking them together. Does anyone
>   have any experience with either of these methods, and is there another
>   way I don't know of? Which way is better, what are the risks, etc? Any
>   info would be appreciated. Thanks,
>   Andy Buonviri
>   Ixthos, Inc.
>   [log in to unmask]