Have you considered dryfilm soldermask?
Tim Reeves
> ----------
> From:         Jeff Hempton
> Sent:         Monday, October 18, 1999 11:48 AM
> Subject:      lpugged vias, or no plugged vias?
>
>      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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