Surface morphology of Sn-rich solder interconnects after electrical loading

Q. S. Zhu, H. Y. Liu, Z. G. Wang, J. K. Shang

Research output: Contribution to journalArticlepeer-review

Abstract

Morphological changes from electromigration were examined on microsized Sn-Ag-Cu, pure Sn, and single-crystal Sn solder interconnects. It was found that both grain structure and alloying had a strong influence on the form of electromigration damage. In polycrystal Sn, grain boundary grooves were the primary form of electromigration damage, while in single-crystal Sn interconnects wavy surface relief appeared following electromigration. Alloying with Ag and Cu encouraged formation of Sn hillocks and Cu 6Sn 5 intermetallic compound (IMC) segregation. The grain boundary grooves were related to the divergence of the vacancy concentration at grain boundaries, which induced Sn grain tilting or sliding. Removal of the grain boundaries in the single-crystal interconnect made surface diffusion the primary electromigration mechanism, resulting in wavy surface relief after long electromigration time. In Sn-Ag-Cu alloy, directional flow of Cu caused Cu 6Sn 5 IMC segregation, which produced large compressive stress, driving the stressed grains to grow into hillocks.

Original languageEnglish (US)
Pages (from-to)741-747
Number of pages7
JournalJournal of Electronic Materials
Volume41
Issue number4
DOIs
StatePublished - Apr 2012

Keywords

  • Solder interconnect
  • electromigration
  • grain boundary groove
  • hillock

ASJC Scopus subject areas

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

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