Gary,

We at GenRad have all our VIA's Plugged & tented for just this reason, however
we are do note probe on the through VIA's, but to add extra bottom side Test
Pads for ICT.

This does cause 1 or 2 problems at the design stage, but gives great benifits
for out Test department, who get much better throughput, & much more reliable
results.

  ________________________________________________________________________
 | [log in to unmask]         David Tandy. EDA Specialist.   GenRad ADS. |
 | Tel: (+44) 161 491 9191     Orion Business Park, Bird Hall Lane,       |
 | Fax: (+44) 161 491 9106     Stockport, Cheshire, SK3 0XG, England.     |
 |________________________________________________________________________|


> Colleagues:
> 
> Our in house SMT assembly facility has asked that we tent our vias on top and 
> bottom sides to aid in solder bridge reduction.  If bottom tenting is not 
> possible becaues vias may double as test points, they ask that we still tent 
> the top (component) side.  They use a no clean process.  
> 
> I am concerned that contaminants will be trapped in vias tented only on one 
> side and cause premature failure down the road.  Normal via size is .012.  
> What are your thoughts on tented vias???  One side?  Both sides?  Not tented 
> ever?  Why???  What other problems may we encounter?
> 
> Thanks in advance for your opinions.
> 
> 
> gary ...
> 
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