Effect of current crowding on whisker growth at the anode in flip chip solder joints

Fan-Yi Ouyang, Kai Chen, K. N. Tu, Yi-Shao Lai

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

57 Citations (Scopus)

Abstract

Owing to the line-to-bump configuration in flip chip solder joints, current crowding occurs when electrons enter into or exit from the solder bump. At the cathode contact, where electrons enter into the bump, current crowding induced pancake-type void formation has now been observed widely. At the anode contact, where electrons exit from the bump, we report here that whisker is formed. Results of both eutectic SnPb and SnAgCu solder joints are presented and compared. The cross-sectioned surface in SnPb showed dimple and bulge after electromigration, while that of SnAgCu remained flat. The difference is due to a larger back stress in the SnAgCu, consequently, electromigration in SnAgCu is slower than that in SnPb. Nanoindentation markers were used to measure the combined atomic fluxes of back stress and electromigration. © 2007 American Institute of Physics.
Original languageEnglish
Article number231919
JournalApplied Physics Letters
Volume91
Issue number23
DOIs
Publication statusPublished - 2007
Externally publishedYes

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