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 --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------