Blind/Buried vias:  IPC-RB-276 calls for a minimum of .5 mil, as you stated, so I 
would say that is the norm.  For many in-house designs, we allow the 0.5 min for via 
pairs (vias from layers 1 to layers 2), but require the full 1 mil for other Buried 
vias, such as a via from layers 2 thru 13 on a 14 layer board.

Bab-Hui Lee-CTUA065 wrote:
> 
> Hello all ye experts out there:
> 
> Is there an IPC specs that calls for certain minimum copper thickness in the
> blind & buried vias? Is 0.5 mil the norm, or more is required??
> 
> _____________________________________________________________________________
> __
> To: [log in to unmask]@INTERNET
> From: [log in to unmask]@INTERNET on Wed, Sep 18, 1996 12:54 PM
> Subject: Re: Users/designer of buried via product
> 
> Jenni,
> It is not my experiance or expertise on buried vias (as a designer) you
> should look for, rather the experiance and expertise of your PWB
> manufacturer. Buried via technology has been around for quite some time and
> most Board Houses offering this technology are quite comfotable and
> proficient with it. If you bare board test you should be able to guarantee
> acceptable yields ( I have my board house do this testing to assure I only
> buy usable boards).
> As a designer I always attempt to stay away from this technology as it cost
> considerably more to fabricate and does not usually seem to "buy" me that
> much in added real estate.
>

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