>In a recent inquiry on this general subject I received a variety  of views
>on the relative value and problems involved in plugging vias.  I would
>appreciate any views on the above option--just covering vias with LPI with
>no special operation to plug or tent.

We use curtain coat application often leaving via holes covered and have
no problem tinning the exposed copper in the holes during HASL even
though the ink runs up to and slightly into the holes. If the finish is
Ni/Au then it will coat the copper in the holes also.

There is no need to have a clearance in the solder mask photography
around these holes unless the customer wants to guarantee plugging them
with solder during assembly wave solder. This will not apply if they are
using infra-red reflowed solder paste.
Paul Gould
[log in to unmask]
Teknacron Circuits Ltd
Isle of Wight,UK

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