It was noted that, under constant-current electromigration, white Sn exhibited a resistance drop of up to 10%. It had a body-centered-tetragonal structure, and the resistivity along the a and b axes was 35% smaller than along the c-axis. Microstructure evolution under electromigration was thought to be responsible for the resistance drop. Synchrotron radiation white-beam X-ray micro-diffraction was used to study this evolution. Grain-by-grain analyses were made, using diffracted Laue patterns, of the changes in grain orientation before and after electromigration. It was observed that high-resistance grains re-oriented with respect to neighboring low-resistance grains; probably by grain growth of the latter.

Electromigration-Induced Microstructure Evolution in Tin Studied by Synchrotron X-Ray Microdiffraction. A.T.Wu, K.N.Tu, J.R.Lloyd, N.Tamura, B.C.Valek, C.R.Kao: Applied Physics Letters, 2004, 85[13], 2490-2