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 [log in to unmask]