Doping compression-tension

Cu-O bonds are under compression as in the T structure, while electrons can be doped when the Cu-O bonds are under tension as in the T structure. 

A comparison of the mechanical properties of an antimony (Sb)-doped Sn-Ag-Cu alloy with the benchmark alloy, eutectic Pb-Sn, is listed in Table 14. The Sn-Ag-Cu-Sb solder was determined to exhibit a superior tensile and compression strength compared to eutectic Sn-Pb, while exhibiting similar yield strength and plasticity (i.e., percent elongation) characteristics. The Sb-doped alloy is significantly stilfer (i.e., Young s Modulus) than eutectic Sn-Pb in tension, but only slightly stiffer in compression. 

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