Effect of surface finishes on electromigration reliability in eutectic Sn–58Bi solder joints

• We studied the failure behavior induced by EM test on the Sn–Bi solder joint.
• We evaluated the EM reliability of Sn–Bi solder joint on various surface finishes.
• The Bi was segregated from cathode to anode side.
• The OSP surface finish showed longer time to failure than others.

This study focuses on the microstructural evolution and failure behavior induced by electromigration in a eutectic Sn–58Bi solder joint. In order to study their effects, surface finishes were prepared with OSP, ENIG, and ENEPIG. The test sample was a flip chip-type reaction module, and the diameter and height of the solder bump were 180 and 100 μm, respectively. A current was passed through the two solder joints, producing a current density of 1.3 × 104 A/cm2 at 100 °C. The time to fail test were carried out sequentially using a test kit under a current density of 1.3 × 104 A/cm2 at 100 °C. The Bi-rich layer was observed at the anode side of the solder joint during the electro migration test. The IMC growth at the interface of the solder joints with current applied was faster than with no-current applied because of a polarity effect. The different surface finished materials affected the behavior of electromigration in the eutectic Sn–58Bi solder joints with current stress. The time to fail (TTF) differed greatly with the surface finishes.

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