Current-stressing at densities of from 2.9 x 104 to 7.3 x 104A/cm2 had significant effects upon the atomic migration of eutectic SnBi solder alloys. At lower densities (2.9 x 104A/cm2), electromigration dominated the migration of both Sn and Bi, and drove Sn and Bi atoms to migrate towards the anode side. At higher densities (4.4 x 104 and 7.3 x 104A/cm2), the enhanced Bi electromigration induced a back-stress which promoted a reverse migration of Sn towards the cathode side. A large number of Sn atoms accumulated at the cathode side and formed lumps there.

Atomic Migration in Eutectic SnBi Solder Alloys due to Current Stressing. C.Chen, C.Huang: Journal of Materials Research, 2008, 23[4], 1051-6

Table 14

Diffusivity of B in α-Ti