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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: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

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. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)102-111
JournalActa Materialia
Volume60
Issue number1
DOIs
Publication statusPublished - Jan 2012
Externally publishedYes

Bibliographical note

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Research Keywords

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

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