Hey gang,
       In a previous life, we did not worry about plugging vias in
     reflow/reflow boards for vacuum pulldown, since we were lower volume,
     high mix military bds., and could afford the time at test to clamshell
     or overclamp (Technical test terms I learned recently from the test
     group guys...).

     We are no-clean, and high volume. We have Genrad inline testers, which
     work quickly with vacuum pull-down, and the test guys like it this
     way. And we have been playing with various methods of plugging test
     vias with printed solder paste, and all other vias with LPI, and
     either get flux-vs.-probe problems or HASL solder caught in the LPI
     via pockets that resurrect themselves as solder balls during reflow!
     We have one small 4" square board that has about 300 vias, and are
     having a-heck-of-a-time trying to find a good solution for this. Oh,
     and all via annular rings must be solder resist covered or conformal
     coat covered, due to extreme environmental uses.

     Can anyone out there share some insight into this issue.
     Thanx in advance for your collective insights!!!

     Jeff Hempton, Sr. SMD Mfg. Engineer
     United Technology Electronic Controls
     e-mail:   [log in to unmask]

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