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September 1997

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Subject:
From:
"Andrew J. Scholand" <[log in to unmask]>
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Date:
Thu, 4 Sep 1997 11:26:14 -0400
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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


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