Tony, (and Phil)
     
        Cross Plying is something that some <claim to fame> works. Phil's
     comment sounds interesting. I think that to find out that cross plying
     was required for a particular construction would be case-by-case. My 
     thoughts on cross plying is that it would be very labor intensive and 
     require an awful lot of warehousing and training. If a minor mistake 
     was made in lay-up or material issue, it would have a hugh impact on 
     the finished product. Once in a blue moon we see the impact of this 
     when a new trainee in lam or material issue cuts down prepreg or cores 
     from a larger size and rotates the grain direction. (Trust me, it's no 
     fun!)
        I've pretty much stayed away from this practice and focused on 
     taking internal layer movement measurements and compensating artwork
     (scaling) up front. I put all the material(s) used with the grain
     direction one way. (For the record, watch the new innovative materials
     that are starting to be used for sample runs. Such as non-woven/random
     fiber, or Compositec <non-woven straight yarns intentionally cross 
     plied to interlock>. These are showing much less movement on cores
     <.005" thk. <Especially on multi up on a panel>)
     
     Groovy
______________________________ Reply Separator _________________________________
Subject: Fab:Re: Crossplying lamination  
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    6/16/96 5:39 PM


In reference to cross plying lamination of multilayer boards:
     
Crossplying has been used successfully by crossplying the B-stage with the 
internal layers in order to balance out dimensional change in the X and Y 
planes.  Crossplying layers with each other most often leads to warping, 
twisting and misregistration.  With the ability to compensate artwork 
differently in the X and Y directions and each layer independently,  the need 
for crossplying is very limited and probably should only be used where an 
unsymmetrical design may require an unsymmetical crossply construction to 
compensate for a warp that cannot be corrected any other way.
     
Phil Hinton
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