A few thoughts would be to mask off the hole with something that is not
solderable. The hole when heated acts as a heat drain and since molten
solder goes to the heat, the via is the place to fill. If it is possible
figure out the volume of the via and deposit enough paste on the pad to do
the entire job, i.e. fill the via and solder the lead. Personally I would
not go this way as it could get messy with too much solder paste and it
could increase the potential for shorts.

My cut would be to mask over the vias as the board is solder masked. By
applying the solder mask over the via this could be accomplished by working
with the design software and would resolve the  issue.

Hope this helps


Regards, Leo Lambert
EPTAC Corp.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Ken Patel
Sent: Monday, March 04, 2002 5:37 PM
To: [log in to unmask]
Subject: [TN] Via in Pad? Need Help!!!
Importance: High


Guys,
On our nickel gold board, solder joints are below IPC spec (insufficient
solder) where there are vias in pad. Solder is drained down the via
holes and deprived the joint of necessary solder.  I would like to know
the following.
(1) How about using the surface finish 63/37 coating HASL instead of
Ni-Gold? I think gold dissolves in solder so quickly that I rather use
HASL processed boards, any thoughts?
(2) Do you guys mask the via on bottom side to avoid solder draining out
on the other side?
(3) Does anybody try Hi Temp solder paste to fill the vias as our
assembly house ordered via stencils to fill the via using eutectic
(63/37) solder paste which didn't work?

Looking for
re,
Ken Patel

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