A customer of mine feedback to me that they discovered the warpage of FR4
laminate have systematic relationship with the thickness variation in a
panel.  In another word, my customer is saying that the greater the
variation in the laminate thickness the greater will be the warpage.
Example, a piece of 0.062" thickness warped FR4 laminate which has a
thickness variation of range 0.058 - 0.069"(ie some points are higher than
the other), the warpage is found to be high on thickness that higher than
the other. Is it true?

Can someone tell me does the laminate thickness variation have a systematic
relationship with bare board warpage?

Is the z- expansion CTE different between different thicknesses of the same
type of material?

Joseph

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