The presence of vias in the pads causes it. Mind, though, that even such
large voids might not affect a long time reliability of the joints.

Regards,

Vladimir

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of shankar rao
Sent: Friday, August 31, 2007 11:49 AM
To: [log in to unmask]
Subject: [TN] vOID IN Micro BGA

Dear All,
   
  We are getting Large voids  in Micro BGA  on someof the pads having
PTH/via  (greater than 40% in dia) after reflow soldering in one of our
multi layer PCB. We are using ROHS paste and ROHS component.  Can I know
what may be the reason for  these voids
   
  Regards
   
  SHANKAR 


K. Shankar Rao
       
---------------------------------
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