Synthesis and analysis of the structure of modified-Al2O3 particles used to increase the strength and electrical conductivity of lead-free solder based on Sn–Ag–Cu

The trend toward miniaturized and highly integrated chip packaging has created a pressing need for lead-free solders with high strength, toughness, and conductivity. In this paper, we designed a scheme of Al 2 O 3 -modified nanomaterial-reinforced low silver Sn1.0Ag0.5Cu (SAC105) solder matrix. To begin with, a novel amorphous carbon and nickel core–shell structure plating modified on Al 2 O 3 (C/Ni/Al 2 O 3 ) were prepared by the electroless plating method. Then, the nano-C/Ni/Al 2 O 3 particle as reinforcement phase was mixed into the matrix solder alloy by ultrasonic vibration stirring. Finally, the morphology and relationship between coated carbon, deposited nickel and original solder interface were analyzed. The microstructure and main properties of the modified solders were also investigated. The experimental results suggested that amorphous carbon and nickel film were prepared on the surface of Al 2 O 3 by electroless plating method. The outer layer of nano-Al 2 O 3 was coated with non-uniform thickness of nickel and carbon coatings. The mass percentage of amorphous carbon was about 3.50%. Adding C/Ni/Al 2 O 3 (0–0.5%) into the SAC105 solder matrix resulted in a gradual increase in conductivity and wettability. The strength and toughness of the modified solder alloy improved as well with the adjunction of reinforced phase. The tensile fracture surface exhibited from a mixture of ductile and brittle, characterized by dimples and cleavage surface, to a purely ductile mode consisting mainly of dimples.