The IPC has a task group writing a document regarding Via Protection and I
personally think this is one of the most important topics needed to be covered
by the group.  The task group is D33-d and you can download the latest version
of the document, which is scheduled to be released this summer from the IPC
website.

Recently we have performed numerous failure analysis on vias that have
partial plugging/tenting that have contaminates trapped within the  via from both
the board fabrication and the assembly processes.  The hole walls are bare
copper and they did not survive the corrosion.

There are so many things to consider when choosing what to do for via
protection, but in my humble opinion if the barrels are left bare copper only
complete plugs and tents have a chance of protecting the vias.  If you are using ENIG
in the vias then you can concentrate on what is needed for your assembly
processes knowing the barrrels of the vias are protected from contaminates.

Susan Mansilla
Robisan Lab

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