David - Independent of  whether the resin coated copper is B-stage only
or C-stage/B-stage, you are correct to assume that in order to
encapsulate the innerlayer circuitry - if it's one ounce (35 micron)
copper - you should have two mils (50 microns) of resin.  Less resin is
necessary to cover one-half ounce (18 micron) circuitry.  Several
different thicknesses from 35 microns to 100 microns are currently
commercially  available of both  B-stage only or C-stage/B-stage
materials.

Kevin R. Thomas
MicroVia Materials Product Manager
AlliedSignal Laminate Systems
608.791.2288
 ----------
>>>From: David Arivett
>>>To: [log in to unmask]
>>>Subject: FAB:Laser vias
>>>Date: Saturday, February 15, 1997 12:54PM
>>>
>>>
>>>
>>>
>>>  An article in the February edition of PCFAB talks about laser drilled
>>>micro-vias. It shows a multi-layer stack-up of two cores with pre preg in
>>>the center. The outer layers are formed with resin coated foil. My question
>>>is: how thick is the resin on the foil? I am sure it must be at least 2
>>>mils
>>>in order to have enough resin to encapsulate the inner layer circuitry.
>>>What
>>>is the maximum it might be?
>>>
>>>David Arivett
>>>Cuplex Inc.
>>>
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