Mark,

We've been successful in plugging via's using the following method:

+ plug the via's on one side of the board per normal LPI methods,
+ send the panel[s] through your UV oven for an extra cure
+ plug the via's on the opposite side of the board per normal LPI methods
+ send the panel[s] through your UV oven for an extra cure

The added UV cure hardens the mask a little more as well as removes any trapped
moisture in the exposed via hole. If you leave the smallest quantity of moisture in the
via it will surely erupt violently during assembly.

Once you've done a few panels it goes rather smooth and works very good.

Franklin


Mark Hargreaves wrote:

> Hi All,
>      Here's the scenario: We're making a small board with a 133 pin PGA.
> Many vias between pads (Vias are 12 mil hole/ 25 mil pad). Customer wants to
> avoid shorts under the PGA during assembly and is requesting that we plug
> via holes and cover the vias on the part side.  What's the best way to do
> this.  (We've got LPI and SR1000 to work with).
>
> Thanks,
> Mark Hargreaves
> EMDS
>
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