My previous response did not get through, so here goes -
     
     I have not seen any reference to the field intensity of the x-ray.
     
     Although I have no experience with X-ray techniques for excessive 
     Sn/Pn migration, I would have to be absolutely convinced from an 
     independent source - publication, standard, research paper, etc., 
     that xray techniques are allowed.
     
     Depending upon the level of field intensity, flooding 
     semiconductor material with x-rays can:
     
     1. Knock electrons loose create current flow and voltage
        potentials on an unconnected board.
     
     2. Introduce interstitial defects in semiconductor material.
     
     Doug McKean ADC Video Systems
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