This paper presents an investigation of lead-free Sn-Ag base alloy, 95.5Sn-3.9Ag-0.6Cu, both experimentally and analytically. Experimentally, the deformation behavior of the material was measured for different temperatures and over a range of strain rates to under isothermal and thermomechanical conditions. Development of a unified viscoplastic constitutive model followed, taking into account the effects of the measured strain rate and temperature changes. The temperature rate effects are considered in the evolution equation of back stress. In order to include material degradation in the solder, the theory of damage mechanics is applied by introducing two damage variables in the viscoplastic constitutive model. Finally, the constitutive model is coded into a general-purpose finite element computer program (ABAQUS) through its user-defined material subroutine (UMAT). The damage-coupled finite element analysis (FEA) is then employed to monitor the condition of failure of a notched component. The predicted and measured maximum loads have been compared and found to be satisfactory. In addition, the calculated damage distribution contours enable the identification of potential failure site for failure analysis.
Behavior of Lead-Free Solder Under Thermomechanical Loading
Contributed by the Electronic and Photonic Packaging Division for publication in the JOURNAL OF ELECTRONIC PACKAGING. Manuscript received December 2003; final revision, March 2004. Associate Editor: Guo-Quon Lu.
Wei , Y., Chow, C. L., Lau, K. J., Vianco , P., and Fang, H. E. (October 6, 2004). "Behavior of Lead-Free Solder Under Thermomechanical Loading ." ASME. J. Electron. Packag. September 2004; 126(3): 367–373. https://doi.org/10.1115/1.1773197
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