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Reply To: | TechNet Mail Forum. |
Date: | Wed, 24 Sep 1997 11:48:00 -0700 |
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Technetters:
Let me make the scenario simpler:
The ficticous multilayer board (10" x 10", 0.062" FR4, HASL) has
already been fabricated and delivered to an assembly subcontractor for
stuffing.
For the sake of this scenario, the assumption is that the wrong
prepreg was selected in the layup process, leading to a partially
cured board. The board is flat at the time it begins the first reflow
process at the assembler. After first reflow, the board has twisted
(not just board sag on the conveyor rails).
Questions:
What effect does undercured prepreg have on warpage during the
assembly process?
Is subsequent warpage (if any) predictable as a percentage of the
original warpage?
Has a reliable process been developed to correct for the warpage after
assembly?
Thanks for your thoughts!
Bill Fabry
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