Interfacial Microstructure, Microhardness and Tensile Properties of Al Micro-Particle Doped Sn-9Zn Eutectic Pb-Free Solder Alloy for Microelectronics Applications

In this study, the effect of Al micro-particles (10μm) to Sn-9Zn eutectic solder, were examined in order to investigate the microstructural and mechanical properties as well as thermal behavior of the newly developed ternary solder alloys. Here, an approach to prepare a micro-composite solder alloy by mixing Al with a molten Sn-Zn solder alloy was developed. The composite solder was prepared by mechanically mixing Al micro-particles into the Sn–9Zn alloy melt to ensure a homogeneous distribution of the reinforcing particles. The Al particles reacted with the Zn and formed intermetallic compounds (IMC) with the eutectic solder alloy. The microstructures of newly developed ternary Sn- 9Zn-xAl solder alloys contain fine needle-like α-Zn phase with some IMCs dispersed in the β-Sn matrix. The compact shaped Al6Zn3Sn IMC uniformly distributed in the β-Sn phase which results in an increase in the tensile strength, due t o t he s econd phase dispersed strengthening mechanism. As the Al content increases, the microhardness of the Sn-9Zn-xAl ternary solder alloys also improves due to the presence of harder IMC in the microstructure. The thermal behavior was found in the sustainable working range for these composite solders