Do you mean the via in the adjacent dogbone pad, or the via-in-pad? I guess it doesn't matter, they should both be plugged. The adjacent via should be soldermask plugged to prevent wicking (solder ball thieving). A solder mask dam alone is not sufficient to prevent this. Molten solder will wick right under the soldermask dam.
The via-in-pad needs to be filled (Peters or equivalent) and plated over so there is no dimple. This is required to prevent large solder voids and "blowouts" from occurring.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of prashant chopra
Sent: Tuesday, January 31, 2012 3:18 AM
To: [log in to unmask]
Subject: [TN] BGA via plugging

Hi,
 
I need help to have expert inputs on whether we need to have the via under the BGA plugged? Does all BGA via should be plugged or only required for fine-pitch BGA? What are the pros and cons? Is there any guideline related to this which can be referred?
 
Thanks.
 
Rgds
Prashant

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