At 04:55 PM 2/4/2008, Ryan Grant wrote:
>Hi All,
>
>I just got told by a design engineer that LaserJet printers are built
>using via in pad where the via is NOT plugged.  He claims the via is
>filled with solder first, then goes through the normal SMT process.
>
>He intends to use this to connect a BGA ball on one side of the board to
>a cap on the other side using an mechanically drill via that is not
>plugged.
>
>Before I call BS on this, and tell him "do not pass go until that via is
>plugged, flattened and plated over", has anyone been successful with a
>via in pad that is not plugged?
>If so, was it double sided?
>And, was one side connected to a BGA ball?

Yes, yes, and yes.

However as you might imagine, the devil's in the details.

Filled (not plugged) with matched CTE non-conductive epoxy (ie SanEi or 
Peters) and planarized (ie flattened) makes life easier and with less 
unintended consequences to manage.  However, there shouldn't be a need to 
overplate the via fill. Unless you're probing filled pads that's just 
needless extra plating process and adds risk of via failures (expansion 
lifts pad and cracks via at knee).



>Thanks,
>Ryan
>
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