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SnSb is Tetraauricupride structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Sn2+ is bonded in a body-centered cubic geometry to eight equivalent Sb2- atoms. All Sn–Sb bond lengths are 3.29 Å. Sb2- is bonded in a body-centered cubic geometry to eight equivalent Sn2+ atoms.
SnSb is Zincblende, Sphalerite structured and crystallizes in the cubic F-43m space group. The structure is three-dimensional. Sn2+ is bonded to four equivalent Sb2- atoms to form corner-sharing SnSb4 tetrahedra. All Sn–Sb bond lengths are 3.00 Å. Sb2- is bonded to four equivalent Sn2+ atoms to form corner-sharing SbSn4 tetrahedra.
SnSb is SC16 CuCl, stable at 5GPa-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. Sn2+ is bonded to four equivalent Sb2- atoms to form corner-sharing SnSb4 trigonal pyramids. There are one shorter (2.90 Å) and three longer (2.98 Å) Sn–Sb bond lengths. Sb2- is bonded to four equivalent Sn2+ atoms to form corner-sharing SbSn4 trigonal pyramids.
Tin-lead-antimony (50Sn–47Pb–3Sb wt.%) soldered assemblies were mechanically tested approximately 30 years after initial production and found to have solder joints of reduced strength. The microstructure of this solder alloy exhibits a ternary eutectic structure with Sn-rich, Pb-rich, and SnSb phases. Accelerated aging was performed to evaluate solder microstructural coarsening and associated strength of laboratory solder joints to correlate these properties to the “naturally aged” solder joints. Isothermal aging was conducted at room temperature, 55, 70, 100, and 135 °C and aging times that ranged from 0.1 to 365 days. The coarsening kinetics of the Pb-rich phase were determined through optical microscopy and image analysis methods established in previous studies on binary Sn–Pb solder. A kinetic equation was developed with time exponent n of 0.43 and activation energy of 24000 J/mol, suggesting grain boundary diffusion or other fast diffusion pathways controlling the microstructural evolution. Compression testing and Vickers microhardness showed significant strength loss within the first 20–30 days after soldering; then, the microstructure and mechanical properties changed more slowly over long periods of time. Further, by combining accelerated aging data and the microstructure-based kinetics, strength predictions were made that match well with the properties of the actual soldered assemblies naturally aged for 30 years. However, aging at the highest temperature of 135 °C produced anomalous behavior suggesting that extraneous aging mechanisms are active. Therefore, data obtained at this temperature or higher should not be used. Overall, the combined microstructural and mechanical property methods used in this study confirmed that the observed reduction in strength of ~ 30-year-old solder joints can be accounted for by the microstructural coarsening that takes place during long-term solid-state aging.