On 08:54 PM 1/09/2001 -0400, Mike Reagan said:

> > I suspect that this is overstated. Fabricators may not want to produce
> > copper-heavy layers that are asymmetrical in the stackup, because of
> > potential warping.
> >
>
>
>I have never heard a manufacturing engineer mention this caused warping.
>See my response to AJ

Yes and yes.  I was responsible for a board a long time ago that had four 
layers. 3 trace layers and one plane.  The plane layer was on an outer 
layer.  The other (trace) layers were not particularly densely tracked.  So 
it was about as unbalanced as you could get.

It had heavy warpage.  The PCB makers stated we would and we did and they 
stated the direction it would warp and they were correct.  It was a long 
time ago, so I prefer to forget it.

Ian Wilson

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