Hi Technetters,

I have a 14.5" x 4" PCB that bows after top side reflow.  I haven't measure the actural bow amount yet, but it looks like it will meet IPC spec.  However, I want to see what I can do to eliminate it.  

I run a blank board through the same reflow profile and don't see any bowing.  The production boards do not have any bowing after bottom side reflow.  Bowing only occur after the top side reflow.  I believe the bowing is due to the two 40mm2 BGAs on the board, which is located 4" from the long edge (center from the narrow width).  Both BGAs have large heat-sinks attached to them.  I reflowed three additional boards on a 10 zone reflow oven (instead of a 7 zone) oven, but didn't see any improvements.  Can anyone give me any other suggestion on how to eliminate the bowing?  Is my assumption of the cause correct?

Thanks all in advance.


Ted 


      

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