Effect of Au/Pd surface finishing on metastable Sn phase formation in microbumps

Yingxia Liu, Nobumichi Tamura, Dong Wook Kim, Sam Gu, King-Ning Tu

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

1 Scopus citations

Abstract

A metastable phase of Sn has been found to co-exist with ß-Sn in Pb-free SnAg microbumps in 3D integrated circuit (3D IC) technology. Synchrotron microbeam x-ray diffraction, high-resolution TEM imaging and selected-area electron diffraction were used to confirm the metastable phase, which has a orthorhombic lattice, with lattice parameter a = 0.635 nm, b = 0.639 nm, and c = 1.147 nm. Its composition is Sn containing about 10 percent of Ni, a few percent of Au and Pd. The structure is probably isostructural with those of Sn4Au, and Sn4Pd with Ni replacing the noble metal. The formation of this phase may be because of Au and Pd in surface finishing for Ni. With only one reflow, this new phase could form almost continuously in microbumps solder when the thickness of solder layer shrinks to 2 μm. The formation of this phase implies the well adopted Au/Pd surface finishing structure may cause potential reliability problems in 3D IC.

Original languageEnglish
Title of host publication2015 IEEE 65th Electronic Components and Technology Conference, ECTC 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages810-815
Number of pages6
ISBN (Electronic)9781479986095
DOIs
StatePublished - 15 Jul 2015
Event2015 65th IEEE Electronic Components and Technology Conference, ECTC 2015 - San Diego, United States
Duration: 26 May 201529 May 2015

Publication series

NameProceedings - Electronic Components and Technology Conference
Volume2015-July
ISSN (Print)0569-5503

Conference

Conference2015 65th IEEE Electronic Components and Technology Conference, ECTC 2015
CountryUnited States
CitySan Diego
Period26/05/1529/05/15

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