Investigation of microstructure and mechanical properties of lead freecomposite solder containing cobalt microparticles produced byaccumulative roll bonding

The miniaturization and compaction trends in electronic equipment and the removal oflead (Pb) element from solder alloys due to environmental considerations have created agreat challenge in the field of designing and developing of new solder alloys. Therefore,researchers have recently focused on composite solder alloys using reinforcing particlesto improve the reliability of lead-free solders. In this research, SAC۰۳۰۷ solder alloys(۹۹ wt.% Sn, ۰.۳ wt.% Ag, and ۰.۷ wt.% Cu) with different percentages of cobaltmicroparticles were made by the Accumulative Roll Bonding (ARB) method. Then, theeffect of the particles on wettability, microstructures and mechanical characteristics ofsolder alloys was investigated. The lowest contact angle was ۲۳◦ in ۰.۲ wt.% cobaltsample. By adding cobalt to the solder matrix, the size of intermetallic compounds(IMCs), Cu۶Sn۵ and Ag۳Sn, decreased and the percentage of eutectic phases increased.The shape of the interfacial intermetallic compounds changed from scallop to layer shapeby adding cobalt, and their average thickness increased about ۱۳-۷۳% in compositesamples. The shear strength of solders increased up to ۲۸% by enhancement of cobaltmicroparticles in the solder alloy containing ۰.۴ wt.% cobalt; however, shear strengthwas decreased in the composite solder containing ۱ wt.% cobalt due to the agglomerationof microparticles. The shear fracture surfaces showed that the nature of the fracturechanged from ductile fracture in the form of elongated dimples to brittle fracture in theform of cleavage with the increase in the percentage of cobalt microparticles. Thecomposite solder alloys containing ۰.۲-۰.۴ wt.% Co have the best wettability behaviorand tensile shear strength.

کلیدواژه ها:

Lead Free Solders ، Nanocomposite Materials ، Soldering ، Intermetallic Compound ، Accumulative Roll Bonding