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JOM

, Volume 45, Issue 7, pp 25–27 | Cite as

Microstructure and mechanical properties of Sn-In and Sn-Bi solders

  • J. W. MorrisJr.
  • J. L. Freer Goldstein
  • Z. Mei
Lead-Free Solder Overview

Abstract

This article presents information that helps to clarify the behavior of lead-free, low-melting, eutectic Sn-In and Sn-Bi solders. The Sn-Bi solder forms a well-defined eutectic microstructure at all solidification rates, while Sn-In solder forms an irregular eutectic that changes to a fine-grained two-phase mixture at high solidification rates. Both solders wet copper by forming tin-containing intermetallics; however, Sn-In forms Sn-In-Cu intermetallics with copper and Au-In intermetallics with gold. The steady-state creep behavior of Sn-In and Sn-Bi roughly resembles that of Sn-Pb with similar microstructures. Sn-Bi further resembles Sn-Pb in that its eutectic microstructure recrystallizes within inhomogeneous shear bands. This is not observed in Sn-In. Both Sn-Bi and Sn-In exhibit pronounced strain softening during shear deformation and show early transitions to tertiary creep. Shear stress-strain behavior at normal temperatures and moderate strain rates is governed by creep; the ultimate shear stress can be inferred from the steady-state creep behavior.

Keywords

Shear Band Solder Joint Tertiary Creep Eutectic Microstructure Ultimate Shear Stress 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© TMS 1993

Authors and Affiliations

  • J. W. MorrisJr.
    • 1
    • 2
  • J. L. Freer Goldstein
    • 1
    • 3
  • Z. Mei
    • 4
  1. 1.University of CaliforniaBerkeleyUSA
  2. 2.Center for Advanced MaterialsLawrence Berkeley LaboratoryUSA
  3. 3.Lawrence Berkeley LaboratoryUSA
  4. 4.Department of Materials Science and Mineral EngineeringUniversity of CaliforniaBerkeleyUSA

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