On the investigation of reuse potential of SnPb-solder affected copper subjected to work-hardening and thermal ageing

Highlights: • SnPb-solder affected old Cu necessitates the characterization of properties to identify reuse potentials. • Micro-hardness values of Cu, Cu-Sn alloy, Cu-Pb alloy and solder affected Cu increase in curvilinear pattern with cold-rolling level up to 50– 55% and then get flatten. • Work-hardening level of ~35% is found as critical where Cu-Pb alloy supersedes pure Cu and Cu-Sn-Pb alloy supersedes Cu-Sn alloy on hardness. • Electrical conductivity of Cu falls drastically with the addition of only about 1% Sn or 1% Pb, which increases with work-hardening level up to ~35% and falls thereafter. • Alteration of phase transition temperature due to inclusion of SnPb-solder in Cu along with work hardening. The reuse potential of SnPb-solder affected old/waste copper is investigated under the influence of work hardening and thermal treatments. In fact, the urge of using old copper to manufacture new components necessitates useful characterization of various properties to explore its reuse potential. In this context, a number of physico-mechanical properties of interest, namely, hardness, conductivity, thermal stability, structure, etc. are chosen here to characterize the solder-affected copper materials as well as analyze their possible changes/improvements under the influence of work-hardening and thermal treatments. Since the old/waste copper usually contains little amount of lead and tin, three additional sample materials, such as, copper ingots, copper‑tin alloy, and copper‑lead alloy are taken into consideration to ascertain the influence of individual solder elements on the properties of the copper alloy. It is observed that addition of trace amount of tin and lead can significantly influence micro-hardness, conductivity, thermal capacity, etc. Micro-hardness values of all four sample materials have been found to be increasing in curvilinear pattern with the rise of cold-rolling level up to 50– 55% and then get flatten, and cold-rolled work-hardening level of ~35% is found to be a critical deformation level where the hardness of CuPb alloy supersedes pure Cu and Cu-Sn-Pb alloy supersedes CuSn alloy. Electrical conductivity of Cu falls drastically with the addition of only about 1% Sn or 1% Pb, which increases little initially after cold-rolled deformation up to ~35% and start falling again with the rise of deformation levels. Shifting of endothermic peak has occurred and thereby recrystallization temperature of Cu is transformed as an effect of alloying due to inclusion of SnPb-solder in Cu as well as work hardening. Micrographs have confirmed the structural changes responsible for the variation of electro-mechanical properties.