Extreme anisotropy of electromigration: Nickel in single-crystal tin
A new approach is developed to fabricate single-crystal Sn solder joints.
Grain orientation of solder joints can be artificially controlled.
Ni3Sn4 forms on the surfaces of single-crystal Sn with regularity after electromigration (EM) test.
Experimental results unequivocally confirm the existence of extremely anisotropic EM system: Ni in single-crystal Sn.
A new approach is developed to fabricate single-crystal Sn solder joints with a line-type structure. The primary purpose is to investigate the diffusion characteristics of Ni in single-crystal Sn with four different grain orientations during electromigration. An interesting new experimental phenomenon that Ni3Sn4 forms on the surfaces of single-crystal Sn with regularity occurs which should be attributed to the extremely anisotropic diffusion property of Ni in single-crystal Sn. Besides, the diffusion velocity of Ni in single-crystal Sn during electromigration is ranked as followed: (001)> (101)> (301)> (100). Experimental observations are in good agreement with kinetic analysis.