Effect of migration and condensation of pre-existing voids on increase in bump resistance of flip chips on flexible substrates during electromigration

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

4 Scopus Citations
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Author(s)

  • S. W. Liang
  • Y. W. Chang
  • Chih Chen
  • Jackie Preciado
  • K. N. Tu

Detail(s)

Original languageEnglish
Pages (from-to)962-967
Journal / PublicationJournal of Electronic Materials
Volume37
Issue number7
Publication statusPublished - Jul 2008
Externally publishedYes

Abstract

In Pb-free solder joints formed by reflowing a bump of solder paste, voids are formed within the solder due to the residue of flux in the reflow process. These voids migrate toward the cathode contact during electromigration under current stressing. Accompanying the electromigration, resistance jumps of a few 100 mΩ were observed. It was postulated that a jump occurs when a void touches the cathode contact. This study investigated the effect of the void migration and condensation on the change in bump resistance using three-dimensional (3D) simulations and finite element analysis. It was found that there was negligible change in bump resistance during void migration towards the high-current-density region before touching the cathode contact opening. When a small void condensed on the contact opening and depleted 18.4% of the area, the bump resistance increased only 0.4 mΩ. Even when a large void depleted 81.6% of the opening, the increase in bump resistance was 3.3 mΩ. These values are approximately two orders of magnitude smaller than those reported in the literature for the change in resistance due to void migration in flip chips on flexible substrates. We conclude that the reported change in resistance was most likely that of the Al or Cu interconnection in the flip-chip samples. © 2008 TMS.

Research Area(s)

  • Electromigration, Flip-chip solder joints, Packaging

Bibliographic Note

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Citation Format(s)

Effect of migration and condensation of pre-existing voids on increase in bump resistance of flip chips on flexible substrates during electromigration. / Liang, S. W.; Chang, Y. W.; Chen, Chih et al.
In: Journal of Electronic Materials, Vol. 37, No. 7, 07.2008, p. 962-967.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review