Genny,
There seems to be a divided opinion on soldering Pb terminated
components with Lead-Free paste.  AIMS had published a study that showed
SJ strength reduction with mixed technology.  There is also a Japanese
study  that showed QFP joints delaminating when boards were going over
wave solder part of process.

It seems Pb forms a Sn-Ag-Pb ternary compound with a low melting phase.
That may affect SJ reliability. However, other variables as to the
component size, board warping/flexing during assembly process, TAL time
etc. may complicate these observations.  You may have to evaluate your
specific application and process. In your example of using LF wire
solder to rework Sn/Pb component joints, higher temperature may affect
both SJ due to mixed metallurgy (low melting phase ternary) and
component itself which is rated for low temperature.

_____________________
pratap singh
Tel./Fax: (512) 255-6820
email: [log in to unmask]
www.rampinc.com

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