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We plug from the bottom side only. If the bottom side is plugged, no
flux can get to the top when spray fluxed. No reliability problems
have been found.
I would be more worried about HASL flux and bare copper in the via
than about wave soldering, which uses considerably less aggressive
flus.
______________________________ Reply Separator _________________________________
Subject: Re: Tented vias???
Author: [log in to unmask] at internet
Date: 12/5/96 5:46 AM
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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