Microstructure characterization and creep behavior of Pb-free Sn-rich solder alloys: Part I. Microstructure characterization of bulk solder and solder/copper joints

R. S. Sidhu, Nikhilesh Chawla

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

Solders are used as interconnect materials in microelectronic packaging. Traditionally, eutectic and near-eutectic Pb-Sn solder alloys have been used. Due to the toxic nature of lead, environmentally-benign Sn-rich (Pb-free) solders are being developed. In this two part series of articles, we have focused on elucidating the relationship between microstructure and creep behavior of Sn-rich alloys, both in bulk form and at the solder sphere joint level. Part I of our study focuses on a detailed quantitative analysis of the effect of controlled cooling rates on solder microstructures. Bulk solder microstructures from cast bars were compared to smaller solder joint microstructures, reflowed from single solder spheres about 1 mm in diameter. Faster cooling rates resulted in much finer secondary dendrite size and spacing, as well as a much finer distribution of Ag3Sn and Cu6 Sn5 particles. The companion article, Part II, provides a unified mechanistic understanding of the creep behavior for the Sn-rich solder alloys, intimately linked to the microstructure characterization work reported in Part I.

Original languageEnglish (US)
Pages (from-to)340-348
Number of pages9
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume39
Issue number2
DOIs
StatePublished - Feb 2008

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Soldering alloys
Copper
Creep
Microstructure
Eutectics
Cooling
Poisons
Microelectronics
Packaging
Lead
Chemical analysis

ASJC Scopus subject areas

  • Materials Science(all)
  • Metals and Alloys

Cite this

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