Jason,

We have indeed seen evidence of problems associated with heating surrounding
components. They are particularly problematic for gull wing type parts
adjacent to repaired BGA's. What happens is what IBM originally called
"double reflow failures". As the adjacent component's solder joints are
heated, they are not heated evenly. Some solder joints pass through
liquidous prior to others. The remaining solder joints that are just below
melting now have all the stresses of the part concentrated within the few
remaining solder joints. The result can be a clean fracture at the weakest
part of the solder joint. This is usually at the pad's intermetallic/bulk
solder interface. The break is such that it is nearly undetectable. It can
easily pass In Circuit Test and may not show up until in the field. That is
what makes this type defect so insidious. I know "double reflow" has been
mentioned in the past on the TechNet, so you might want to check the
archives.

Thanks,
Robert Furrow
Printed Wiring Board Engineer
Strategic Supply Global Account Manager
Supply Chain Networks
Lucent Technologies
978-960-3224    [log in to unmask]


-----Original Message-----
From: JASON CROSS [mailto:[log in to unmask]]
Sent: Monday, November 05, 2001 9:24 AM
To: [log in to unmask]
Subject: [TN] Effect of BGA rework to surrounding components


Hello,
I am hoping someone here can help with the following:  recent inquiries
have come up with respect to the effect of BGA rework to surrounding
components.  Can the heat effect to surrounding components -- the
possibility (and probability) that they will reach reflow temperatures,
cause problems?  I am thinking of cases where some BGA balls might reach
reflow temperatures and others might not on a single package at
proximity to the reworked site.  Another case would be where BGA
packages at proximity to the reworked BGA are simply reaching high
temperatures - for possibly many heat/rework cycles..

Impact to solder joint metallurgy
Impact to solder joint reliability

Any help or reference would be greatly appreciated.

--
Jason Cross
Physical Technology Engineer
Alcatel Canada, Inc.
(613) 784-4793

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