Length-Dependent Electromigration Behavior of Sn58Bi Solder and Critical Length of Electromigration

Xu Zhao, Mikio Muraoka, Masumi Saka

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


On the basis of a developed test structure, electromigration (EM) tests of Sn58Bi solder strips with lengths of 50 μm, 100 μm, and 150 μm were simultaneously conducted at a current density of 27 kA/cm2 at 373 K. Length-dependent EM behavior was detected, and the mechanism is discussed. Bi atoms were segregated to the anode side more easily as the strip length increased, which resulted in the formation of a thicker Bi-rich layer or Sn-Bi mixed hillocks. The results reveal the existence of back flow that depends on the solder joint length. The back flow is most likely caused by an oxide layer formed on the Sn58Bi solder. By measuring the thicknesses of the Bi-rich layers, the Bi drift velocities were obtained. The critical length of the solder joint and the critical product of the length and the current density were estimated to be 16 μm and 43 A/cm, respectively. This observation will assist design of advanced electronic devices to anticipate EM reliability.

Original languageEnglish
Pages (from-to)1287-1292
Number of pages6
JournalJournal of Electronic Materials
Issue number2
Publication statusPublished - 2017 Feb 1


  • Sn58Bi solder
  • back flow
  • critical length
  • electromigration
  • simultaneous evaluation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry


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