Hi,

        Need some advice on how to eliminate or reduce the solder on finger
that
we are having right now. So far what we understand is that 90% of the
problem is
due to the reflow process where solder traps in vias causing explosion when
subjected to high temp during reflow. Not sure whether this is the right
assumption but from what we have seen on the reject there are solder balls
all
over the 'exploded' vias.  The signature of solder on finger defects is
10-40
mils of 'dot' which could be caused by solder balls.  SO this is my
questions:

1.  Is it possible that the vias can 'explode' during reflow?

2.  Does the ramp from room temp to soaking time(145-160 deg C) and from
soaking
time (160-183 deg C) play an important role in determining the amount of
'explosion'.  So far our data shows that it does.

3.  Is there any other possible causes of solder explosion...Solder paste?


Thank you and really appreciate the help.

Masdi Muhammad,
Process Engineer.

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