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| Date: | Fri, 17 Feb 2012 18:42:37 -0600 |
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Hi Jeff - fillet lifting is the result of the solder alloy solidification
behavior. The tried and true Sn63Pb37 solder alloy the industry has used
for year is a eutectic alloy - it changes from a molten state to a solid
state at one specific temperature (183C). Many lead-free alloys, such as
SAC305, are not eutectic alloys - they change from a molten state to a
molten plus solid state (many folks call this the "mushy zone" to a solid
state. Fillet lifting is associated with that alloy solidification
behavior. It is easier to work with a metal alloy that has eutectic
behavior as we avoid issues such as fillet lifting or shrinkage voids that
are due to the alloy metallurgical reactions. Hope that helps.
Dave Hillman
Rockwell Collins
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Jeff Popp <[log in to unmask]>
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[TN] Lead Free Fillet Lift
The IPC-610E, section 5.2.11 describes lead-free fillet lift as a
"phenomenon in which the solder fillet is lifted off from the land on a
board mainly during the flow solder process."
It sounds a little supernatural to me using the term "phenomenon." I was
just curious what exactly the cause(s) of fillet-lift were and why
wouldn't it be considered a defect - similar to non-wetting?
Best Regards,
Jeff
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