We are changing from dry film solder mask to LPI solder mask on all our
through-hole PCB's (LPI is already used on our relatively small number of
surface mount boards but we don't have long term field failure data on
these).  With respect to vias we are leaning toward covering them with LPI
as we now do with dry film (i.e. not tenting with dry film, not plugging
with LPI, epoxy etc.--just applying LPI in a single operation using the
same solder mask artwork we now use which covers the vias).  It may be
relevant to know that many of our boards are not used in temperature and
humidity controlled environments.  We do conformal coat most of our boards.

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.

Some of the earlier replies suggested partially filled vias cause more
problems than totally uncovered vias.  Has anyone tried the above option?
Problems?  No problems?  Would it be useful to minimize via diameters?  Is
there any useful literature on this subject.?

Thanks to all of you who replied to the earlier inquiry.

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