محمدهادی نورمحمدی - Faculty of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
مجتبی موحدی - Faculty of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
امیرحسین کوکبی - Faculty of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.
معین تمیزی - Faculty of Materials Science and Engineering, Sharif University of Technology, Tehran, Iran.

The miniaturization and compaction trends in electronic equipment and the removal of lead (Pb) element from solder alloys due to environmental considerations have created a great challenge in the field of designing and developing of new solder alloys. Therefore, researchers have recently focused on composite solder alloys using reinforcing particles to 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 cobalt microparticles were made by the Accumulative Roll Bonding (ARB) method. Then, the effect of the particles on wettability, microstructures and mechanical characteristics of solder alloys was investigated. The lowest contact angle was ۲۳◦in ۰.۲ wt.% cobalt sample. 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 shape by adding cobalt, and their average thickness increased about ۱۳-۷۱% in composite samples. The shear strength of solders increased up to ۳۸% by enhancement of cobalt microparticles in the solder alloy containing ۰.۴ wt.% cobalt; however, shear strength was decreased in the composite solder containing ۱ wt.% cobalt due to the agglomeration of microparticles. The shear fracture surfaces showed that the nature of the fracture changed from ductile fracture in the form of elongated dimples to brittle fracture in the form of cleavage with the increase in the percentage of cobalt microparticles. The composite solder alloys containing ۰.۲-۰.۴ wt.% Co have the best wettability behavior and tensile shear strength.

Lead free solders, Nanocomposite Materials, Soldering, Intermetallic compound, Accumulative Roll Bonding., لحیم های نرم بدون سرب؛ نانوکامپوزیت ها؛ لحیم کاری؛ کامپوزیت های زمینه فلزی؛ ترکیبات بین فلزی؛ اتصال نورد انباشتی