Electrorecrystallization of intermetallic compound in the Sn0.7Cu solder joint

The electrorecrystallization, recrystallization driven by electrical current stressing, of Cu6Sn5 intermetallic compound occurs in a Sn0.7Cu flip chip solder bump. The Cu6Sn5 dissolves in Sn0.7Cu at 1.0 × 104 A/cm2 of current stressing under 150 °C. The Cu flux in the solder joint, driven by the combination force of thermal gradient and electromigration, flows toward the cold side of the solder joint. The segregation of Cu results in recrystallization and thus redistribution of IMC at the cold side of the solder joint after current stops.

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► The intermetallic compounds in the solder redistributed upon current stressing.
► The thermomigration and electromigration combined to drive the IMC redistribution.
► The IMC Cu atoms dissolved and migrated to result in recrystallization of the IMC.