Good morning Weemei -

In response to your questions:
1]  Yes, it is true that solder will flow thru a via, when that via is placed
in a component termination pad.  This results in a condition where solder is
stolen from the intended termination, resulting in an insufficient solder
connection.  In turn, a portion of that solder fills the via, and a bead may
form on the opposite side of the circuit board.  This was a design technique
that many of us tried in the late 1980's and discarded as a result of the
problems noted above.

2] The vias we experienced this problem with were in the .012-.018" finished
inner diameter range.  I have not experimented to determine whether a small
enough via could be created to prevent capillarity.  Given the flow
charactaristics of molten solder, I suspect this could not be accomplished in
a manner that can be repeated consistantly under production conditions.
Since proven design alternatives exist, this would seem to be an entertaining
science project with little or no practical application.

3] As noted in item 2 above - I have no answer for this question.

Regards - Kelly

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