Influence of reflow and thermal aging on the shear strength and fracture behavior of Sn-3.5Ag solder/Cu joints

X. Deng, R. S. Sidhu, P. Johnson, Nikhilesh Chawla

Research output: Contribution to journalArticle

131 Scopus citations

Abstract

The mechanical behavior of Sn-rich solder/Cu joints is highly sensitive to processing variables such as solder reflow time, cooling rate, and subsequent thermal aging. In this article, we focus on the lap shear behavior of Sn-3.5Ag/ Cu joints as a function of solder yield strength and intermetallic thickness. Experimental results showed that the shear strength of the solder joints is primarily controlled by the mechanical properties of the solder, and not the intermetallic thickness. The thickness of intermetallic, however, controlled the fracture mode of the solder joints. At intermetallic thicknesses greater than 20 μm, brittle fracture between Cu6Sn5 and Cu3Sn was the most common failure mechanism. Finite-element simulations were carried out to evaluate the effect of solder properties and of intermetallic thickness and morphology on lap shear behavior. The finite-element simulations corroborated the experimental findings, i.e., that increased solder strength results in increased joint strength. The simulations also showed that thicker intermetallics, especially of nodular morphology, yielded higher local plastic shear strain and work hardening rate.

Original languageEnglish (US)
Pages (from-to)55-64
Number of pages10
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume36 A
Issue number1
DOIs
StatePublished - Jan 2005

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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