1 You should not be using solder mask defined pads particularly if you are
going lead fre s gives a 90 degree wetting angle which acts as a stress
riser.

2 If you are plugging the vias, you will not be able to do this at most fab
shops on a silver finish.

3Yes I have reworked them obviously with the plugged via no problem on
degradation. If the vias are unplugged, have used a process to apply a
double layer of mask at the via hole only to protect it during re-work. This
works great if you can't plug.

4 Do not have cost data available.

John

http://www.rohsusa.com



-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Miswald, Ron
Sent: Wednesday, May 10, 2006 7:41 AM
To: [log in to unmask]
Subject: [TN] Unplugged via under BGA

All

There is a board where this recently came up on.  The vendor is one we
haven't dealt with before.  I looked in the tech net archives, and did not
find an answer to this specific question.  The vias under the BGA are 22 mil
pad, 18 mil solder mask, and 12 mil hole.  I usually ask for the vias to be
filled or plugged...

My question:
1) Has anyone else had experience with running this type of board?
2)If not, has anyone had them reworked?
a)by who?
b) what was cost per via, or board?

Any shared experiences appreciated
Ron

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