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

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 crowd...

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Bibliographic Details
Published in:Acta materialia 2012, Vol.60 (1), p.102-111
Main Authors: Han, Jung Kyu, Choi, Daechul, Fujiyoshi, Masaru, Chiwata, Nobuhiko, Tu, King-Ning
Format: Article
Language:English
Subjects:
Applied sciences
Brazing. Soldering
Compressive properties
Copper
Crowding
Current crowding
Current density
Current effect of microstructure
Electromigration
Electronics
Exact sciences and technology
Failure mechanisms
Joining, thermal cutting: metallurgical aspects
Metals. Metallurgy
Soldering
Solders
Three dimensional
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Summary: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.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2011.09.023