If you are talking about the voids at the PTH walls, one way is to dip
     the PCB in a solder pot for a few seconds and then do cross-section
     throught the solder in the PTH. Outgassing will occur if there is a
     void, hence bubble is visible in the PTH solder. I tried this method
     before, and find it very difficult to discover the bubbles because of
     their small size. Anybody have a better method please let me know.


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Subject: [TECHNET] Viod Inspect
Author:  "TechNet Mail Forum." <[log in to unmask]>, at corp