Dear Technetters

   We send some of our boards out of plant to be hot air leveled.  When we 
receive the boards back we have noticed a very small number of the boards 
have isolated surface mount pads that are missing.  There is no visible 
damage to the surface of the board surrounding the area where the pad was.  
The surface of the board under the surface mount pad looks rough like the pad 
was pulled off the base laminate.  There is evidence that mechanical force 
was exerted sufficient to break fibers and remove some of the glass epoxy 
with the pad.  We are only seeing 1 or 2 pads on a panel which seem to be in 
the same general area, however we don't have enough observations to draw any 
conclusions.  Has anyone seen this condition?  What could the possible cause 
be?