MECHANICAL AND FRACTURE BEHAVIOR OF VARIOUS LEVELS TIN-DOPED COPPER FROM LEAD-FREE SOLDER JOINTS SUBJECTED TO THERMAL AGINGPages 116-126 Abstract
Pure copper may be influenced by contamination from tin, which is frequently introduced during the melting or recycling of scrap material derived from lead-free solder. The research examines the effects of two different levels of tin on waste copper sourced from tin-based lead-free solder. Scrap copper is cleaned by cutting out the major solder joint and using mechanical wire brushing for other portions. Then the cast samples are plastically deformed up to 80% and isochronally aged for 1h at temperatures up to 500°C to analyze stress-strain behavior, hardness, toughness, microstructure, and fracture mode. Results reveal that recycled copper has a tin content of approximately 0.26% to 0.57%, depending on the cleaning process. It improves the alloy's tensile characteristics with the expenses of ductility particularly at lower temperatures for ageing, but is insufficiently beneficial at elevated ageing temperatures. Tin is enhanced through solid solution strengthening and establishes intermetallic bonds with copper and impurities in cast alloys, which obstructs dislocation movement, thereby increasing strength and affecting ductility during the ageing process. The coarsening of precipitates at elevated temperatures diminishes effectiveness, resulting in reduced strength. Rigid intermetallic phases induce crack formation within the matrix, as observed on the fracture surface.
Keywords:
Scrap copper,
Tin,
Lead-free solder,
Mechanical properties,
Fracture behavior,
Microstructure,
Thermal aging.
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Mohammad Salim Kaisera 
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