Current density redistribution from no current crowding to current crowding in Pb-free solder joints with an extremely thick Cu layer

Jung Kyu Han*, Daechul Choi, Masaru Fujiyoshi, Nobuhiko Chiwata, King-Ning Tu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

In order to remove the effect of current crowding on electromigration, thick Cu under-bump metallization has been widely adopted in the electronics industry. Three-dimensional (3-D) integrated circuits, using through Si via Cu column interconnects, is being developed, and it seems that current crowding may not be a reliability issue. However, statistical experiments and 3-D finite element simulation indicate that there is a transition from no current crowding to current crowding, caused by void growth at the cathode. An analysis of the electromigration-induced failure mechanism in solder joints having a very thick Cu layer is presented. It is a unique failure mechanism, different from that in flip chip technology. Moreover, the study of marker displacement shows two different stages of drift velocity, which clearly demonstrates the back-stress effect and the development of compressive stress.

Original languageEnglish
Pages (from-to)102-111
Number of pages10
JournalActa Materialia
Volume60
Issue number1
DOIs
StatePublished - 1 Jan 2012

Keywords

  • Current crowding
  • Current effect of microstructure
  • Electromigration
  • Soldering

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