In a message dated 3/23/99 2:52:22 PM Pacific Standard Time,
[log in to unmask] writes:

> Are you guys building cards with partially closed VIA's?  What about
>  >contamination getting trapped in the VIA?  Is this a valid concern?
>  >
>  >Appreciate any comments.
>  >
>  >Jim Kittel

Hi Jim,

    If your board is going to be waved and the vias are open on the side
exposed to the wave, then you do have some concern. Flux could get trapped
inside the vias by solder should there be surface area enough for the solder
to wet to.

    You may also see little solder bubbles from where the solder has tried to
close the via, but then the flux volatiles outgassed as the solder was going
solid forming these little bubbles that are attached to the via...they'll look
almost like a bunch of solderballs. If one side is going to have the vias
open, it should be the side away from the wave.

-Steve Gregory-

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