Three-dimensional simulation on current-density distribution in flip-chip solder joints under electric current stressing

T. L. Shao, S. W. Liang, T. C. Lin, Chih Chen*

*Corresponding author for this work

Research output: Contribution to journalArticle

47 Scopus citations

Abstract

Three-dimensional simulations on current-density distribution in solder joints under electric current stressing were carried out by finite element method. Five underbump metallization (UBM) structures were simulated, including TiCr-CuCu thin-film UBM, AlNi (V) Cu thin-film UBM, Cu thick-film UBM, Ni thick-film UBM, and CuNi thick-film UBM. The maximum current density inside the solder occurs in the vicinity of the entrance of the Al trace into the solder joint, while there is no obvious current crowding effect in the substrate side of the joint. The crowding ratio, which is defined as the maximum current density inside the solder divided by the average value in the UBM opening, is as high as 24.7 for the solder with the TiCr-CuCu UBM. However, it decreases to 23.4, 13.5, 8.7, and 7.2 for the rest of the UBM structures, respectively. Solder joints with thick UBMs were found to have a better ability to relieve the current crowding effect. The simulation results are in reasonable agreement with limited published data. The solder joints with higher current crowding ratios have a shorter electromigration failure time.

Original languageEnglish
Article number044509
JournalJournal of Applied Physics
Volume98
Issue number4
DOIs
StatePublished - 15 Aug 2005

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