Our PCA house currently bakes all of our PCBs before assy.  Our boards are
typically 16" X 13".  The boards are placed vertically in a
rack that holds them by just the bottom edge that has a V-score breakaway.  They
are in there for 2.5 hours @ 200-210 deg F.  We had a
batch of boards that warp and twisted after the above mentioned bake.  The PCA
and PCB house are pointing fingers at each other as to
who is at fault.

     So far it has been only one date code that this has happened to.  Each PCB
is one up on a panel from the PCB house due
to its size.  The PCB vendor claims that in talking to other PCA houses in their
area, the boards should not be baked vert. in a rack because
it is a hit or miss as to whether or not the boards will twist during the bake.
The claim is that the boards should be baked horiz. stacked on top
of each other.  My question is: What is the correct method of doing a pre-bake
of the PCBs to remove moisture prior to assy, if there is one?


Best Regards,

Michael Forrester
Sr. Manufacturing Engineer
LeCroy Corp

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