======== Original Message ========
Is it important to make sure that intermediate layups for blind/buried
vias are as symmetric as possible to limit post-lamination warpage?

Thanks,
        Andy

======== Fwd by: Richard MacCu ========
>From a fab standpoint, the easiest/cheapest way to do blind/buried vias
is
to limit the layers they traverse to two if possible.  As you add more
layers you must pay for extra lamination steps to build up the padstacks
you
require.  It is relatively easy to create buried vias.   Blind vias are
more
difficult whether controlled depth drilling or some other blind via
technique is used.  Each subsequent lamination can impact board price as
much as 30%.
As far as definition of vias.  Having separate drill drawings reflecting
the
 via locations and a table showing each drawing's relationship is usually
easy to interpret.  If you use a particular supplier I would suggest
having
one of their Manufacturing Engr. types evaluate the docs on a
preproduction
basis to get their input.

Good Luck
======== Fwd by: Richard MacCu ========
A balanced construction is very important to flatness.  However, if you are
only populating one side of the board in the design, there will be a
tendency to have a lopsided stack-up. The more laminations to be made in an
unbalanced construction, the more likely warpage will occur.

Specifying thinner core material,( higher resin content construction) for
the blind/buried portions of the stack-up may lessen those layer's influence
on the complete board if the balance is off.

Another suggestion for the designer posting the B&B query is to specify a
minimum etchback of between .0003"-.0007" if possible for all plated holes.
Lamination forces on the buried/blind vias can have an influence on
reliability and etchback has proven to be beneficial to reliability.

Adios