Can't you simply use a ground plane (usually internal, of course, you 
probably already have one) and tell the pcb house to use it as the top 
and/or bottom too?

Richard

At 04:33 PM 7/30/2002 -0700, you wrote:
>Question to smartest of smartest designers out there:
>
>Here is the delima,   we have a board appox 24 x 30  ( a very large
>backplane) , many thousands of connections, every layer controlled
>impedance.  The boards are used for high speed  tele comminications
>switching and data monitoring.  ( No the the tele com industry is not dead).
>The designs are as many as 28 layers, some approching .250 inch in
>thickness,  a very expensive baord to design and manufacture.
>
>On the outer layers we avoid placing traces, since we embed the entire
>design,  The outer layer are  copper pours tied to gnd  to reduce EMI and to
>maintain controlled Z on the next inner layer.  The copper is poured on both
>the  top and bottom layers.
>
>Copper pours of this size are poured last because they are time consuming.
>The pours can take 4 hours, and even longer if they are not right the first
>time.  Question to any of the best out there.....can we avoid a copper pour
>and merge a gnd layer to the top?  Does anyone have a method or suggestion
>to merge copper to flood the top layer.     Is there a quicker method?   We
>are using 99SE on aa 1 gig cpu with 512 meg.
>
>Mike Reagan
>EDSI
>
>
>************************************************************************
>* Tracking #: C05FC4455FDD074E8E0D19C321C392CAC217810D
>*
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