You might also want to look at the balance of copper on the external layers.
Then, look at the distribution of the plane layers within the stack -- they also
should be symetrical. Do you bake the boards prior to reflow? Do you support the
boards?
______________________________ Reply Separator _________________________________
Subject: [TECHNET] PCB Warpage - Clarification
Author: <[log in to unmask]> at SMTPpost