[log in to unmask] wrote:
>
> 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 

	Gary, although I've seen the one-side-tent in several applications
	it always scares me for the reasons you site.

	Another way to help the problem may be to base your top-side solder-
	mask on the drill size rather than the pad size.  At the end of the
	day, do we really care if the periphery of the top side via is SnPb
	or simply SMOBC?  This technique has worked well for us in many class
	2 applications, leaving the design flexibility of tented vias while
	maximizing the spacing presented to the solder world.

	Regards,
-- 

      Jeff Seeger                              Victor Johansen Fan Club
      Chief Technical Officer                      Tyngsboro, MA  01879
      [log in to unmask]                               508 649 9800

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************