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Journal of Electronic Materials

, Volume 32, Issue 3, pp 142–151 | Cite as

Time-independent mechanical and physical properties of the ternary 95.5Sn-3.9Ag-0.6Cu solder

  • Paul T. Vianco
  • Jerome A. Rejent
  • Alice C. Kilgo
Regular Issue Paper

Abstract

The development of a constitutive model for predicting the thermal-mechanical fatigue (TMF) of 95.5Sn-3.9Ag-0.6Cu (wt.%) Pb-free solder interconnects requires the measurement of time-independent mechanical and physical properties. Yield stress was measured over the temperature range of −25–160°C using strain rates of 4.2 × 10−5 s−1 and 8.3 × 10−4 s−1. The yield-stress values ranged from approximately 40 MPa at −25°C to 10 MPa at 160°C for tests performed at 4.2 × 10−5 s−1. The faster strain rate and specimen aging had a limited impact on the yield stress. The true stress/true strain curves indicated that dynamic-recovery and dynamic-recrystallization processes took place in as-cast samples exposed to temperatures of 125°C and 160°C, respectively, while tested at a strain rate of 4.2 × 10−5 s−1. Aging the sample prior to testing, as well as a faster strain rate, mitigated both phenomena. Dynamic Young’s modulus values ranged from 55 GPa at −50°C to 35 GPa at 200°C, while the coefficient of thermal expansion (CTE) increased from approximately 12 × 10−6°C−1 to 24 × 10−6°C−1 for the same temperature range. The aging treatment had little effect on either Young’s modulus or the CTE.

Key words

Tin-silver-copper (Sn-Ag-Cu) solder thermal-mechanical fatigue modeling constitutive equation yield stress elastic modulus thermal expansion 

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Copyright information

© TMS-The Minerals, Metals and Materials Society 2003

Authors and Affiliations

  • Paul T. Vianco
    • 1
  • Jerome A. Rejent
    • 1
  • Alice C. Kilgo
    • 1
  1. 1.Sandia National LaboratoriesAlbuquerque

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