Hello

Take a case of a six layer board. Normally a via drilled passes through
all the layers. But in Blind and Buried Via case the following will hold
good.

Blind Via
---------

A Via drilled to route a track from layer 6 to say layer 5. There won't
be any drills at this location in the rest of the layers. The real
estate on these layers is available for tracks/vias.
Thus a via drilled from "top or bottom" layer to any inner layer, that
does not appear on the other side is called a blind via.

Buried Via
----------

A via drilled to route a track say from layer 2 to 5. There wont't be
any drills appearing on either layer 1 or 6. The same could be true for
say vias between layers 3 to 4 and so on. 
Thus the via is completely buried between the top and bottom layers, but
is not visible on either of these two layers.

I really do not know what you mean by "Is there such thing as a via to
the outside that has been filled?". Could someone out there shed some
light on this?.

k.v.raj

---------------------------------------------------
>From : K.Varadaraj@CADET Automation Systems, India.
Phone: 91 80 665 7215
Fax  : 91 80 528 0101
email: [log in to unmask]
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