Scott,

Were the vias covered from one side or both with mask.

Steve,

One possible scenario to answer your question is this.  If the
board, assuming double sided SMT design, had vias covered
(tented) with mask and required electrical test the vendor may have
masked the board leaving the vias exposed for test by a single
sided tester (flip test), them over the vias as a separate process
post HASL.

We do this on occasion but have had no negative feedback on the
practice.  I am very interested in the specifics of this boards
construction (both Stephen's and Scott's) to see if we may
experience similar problems in the future.

Regards
John Parsons

> In a message dated 8/10/00 10:24:21 AM EST, [log in to unmask]
> writes:
>
> << I have a problem with via's that have been masked over having
> trapped solder in the via's after HASL.  The solder that is in the
> via's is surfacing after we reflow the bottom side of the board.  I
> have not had this problem before and wanted some advice from all of
> you.  I am sending this message again due to the lack of response I
> got.  Any help or advice would be greatly appreciated!
>  Thank you,
>
>  Scott Lefebvre
>  [log in to unmask] <mailto:[log in to unmask]> >>
>
> Hi Scott!
>
> I had the same thing happen quite a while ago. With the boards that I
> had it appeared that an attempt was made to tent the via's after HASL
> by applying the mask only on the via's...why that was done I have no
> idea. The boards were consigned to us by our customer. But just like
> you, we had these little balls all over the board after they had
> squirted out during reflow...some of them you could kinda' scrape off,
> but most were firmly attached to the anular pad of the via.
> Bottom-line, the boards were scrapped...
>
> Sorry, couldn't be of more help...
>
> -Steve Gregory-
>
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