Some fundamental issues in the use of Zn-containing lead-free solders for electronic packaging

S. Vaynman, Gautam Ghosh*, M. E. Fine

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

A synergistic approach is applied to address the major concerns about the use of Zn-containing lead-free solders for electronic packaging. Using computational thermodynamics as a predictive tool, the phase stability of the Ag-Al-Cu-In-Sn-Zn system is examined to design a Zn-containing lead-free solder with melting characteristics similar to near-eutectic Pb-Sn solder. Theoretically, it is found that a Sn-0.3 mass%Al-4.2 mass%In-7.8 mass%Zn solder has a melting point (liquidus temperature) of 185°C and a solidification range of 10°C. It is demonstrated that environmentally benign fluxes containing tin-organometallics significantly improve the wetting behavior compared to rosin fluxes used for lead-tin solders. For the Sn-Zn eutectic solder on a Cu substrate at 260°C, it is found that the contact angle is reduced from 150° to about 25° when tin-organometallic fluxes are used instead of rosin flux. Severe accelerated tests (85% relative humidity at 85°C) for up to six weeks show that the mechanical properties of Sn-Zn eutectic solder interconnects are not affected adversely by the environment.

Original languageEnglish (US)
Pages (from-to)630-636
Number of pages7
JournalMaterials Transactions
Volume45
Issue number3
DOIs
StatePublished - Jan 1 2004

Keywords

  • Computational thermodynamics
  • Fluxes
  • Lead-free solders
  • Mechanical properties
  • Wetting angle
  • Zinc-containing solders

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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