Hi Jim,
You write: "Propagation of the fracture is usually through the IMC at the
lead surface."
I respectfully disagree; if you look closely, you see that the propagation of
the fracture is usually just outside the IMC at the lead surface, in the
region of the SJ where Sn has been somewhat depleted to form the Sn/Cu IMCs.
Lets not give IMCs a bum-rap where they do not deserve it. A truly
interfacial separation shows essentially only base metal on one fracture
surface and solder (rarely IMC because in most of these cases no
metallurgical bonding (wetting=formation of IMCs) has taken place) on the
other.
Re covering the lead ends with solder am in full agreement with you.

Werner Engelmaier

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