Greetings DC,
The boards I usually build are precision fit boards and require more
flatness than typical. They have a thickness of 190 mills and have 10 to 20
layers usually FR-4 material and sometimes I use GeTek.
I use two different statements for flatness, depending on who is pushing me
at the time.
Bow and Twist per IPC-650 shall be .5% max.
Board Twist and Warp not to exceed .005 (1%) per linear inch. front to back
registration to be with in .003 in.
The boards are low volume and hand assembled. This issue arose because of a
board set that was completed and now is not mounting properly because of
warpage.
If there are any fabricators reading this, what do you like to see to tell
you of tighter than normal spec for flatness? And what would you expect of
consequences for a board that does not meet the requirements?
Thanks,
Ray


Ray Dwyer
972-371-4046
Maxim
4401 Beltwood Parkway
Dallas, Tx. 75244



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