Sn-Pb solders was widely used in the electronic packaging industry for more than 50 years ago. However, as the environmental concerns on the usage of lead arise, the transition of lead solder to lead-free solder took placed. The introduction of lead-free solder nowadays still cannot meet the requirements and demands for current technologies. Moreover, the excessive formation of brittle intermetallic either as primary crystals or interfacial layer in Sn-3.0Ag-0.5Cu (SAC305) could degrade the reliability of the solder joints especially during the long-term service. Thus, this research was motivated to develop SAC305 lead-free solder with composite approaches. In this research, the composite solder was developed by using SAC305 lead-free solder as the matrix and kaolin geopolymer ceramic (KGC) as the reinforcement particles. The aims of this study were to investigate the effects of various weight percentage (0, 0.5, 1.0, 1.5 and 2.0 wt.%) of KGC to the properties of SAC305 lead-free solder and the performance of SAC305 with additions of KGC under isothermal ageing and multiple cycle of reflow soldering. The synthesized of the new SAC305 composite solder was through powder metallurgy route with hybrid microwave assisted sintering technique and was analyzed based on the microstructure formations, thermal properties, spreadability and shear strength. Scanning electron microscope (SEM) and synchrotron micro X-ray fluorescence was used to analyzed the microstructure formations. Besides that, differential scanning calorimetry (DSC) was used to investigate the thermal properties of composite solder. Meanwhile, the shear strength was obtained through a lap shear test. The results proved that with 1.0 wt.% KGC addition in SAC305 solder, the microstructure formations, thermal properties, spreadability and shear strength was greatly enhanced as compared to plain SAC305. Moreover, during isothermal ageing at ageing temperature of 85 °C, 125 °C and 150 °C with ageing time of 100 hours, 500 hours and 1000 hours, the coarsening of the intermetallic particles in SAC305 with KGC additions was not obvious. Although the shear strength showing a decreasing trend with increasing temperature and time, but still the decrement value in SAC305 with KGC additions lower than plain SAC305. Besides that, during multiple cycle of reflow soldering, it was proved that the suppression in the microstructure formations and the improvements in the shear strength was contributed by the existence of KGC at the grains of Cu6Sn5 IMC and primary crystals of Cu6Sn5 IMC through adsorption theory. Moreover, by using advance technique of in situ synchrotron imaging, the growth of primary crystals of Cu6Sn5 IMC could be in-situ observed during each cycle of reflow soldering. The primary crystals of Cu6Sn5 IMC in SAC305 with KGC additions growth at rate of 38 μm/s with shorter solidified length. As a conclusion, KGC reinforcement particles can be as a potential reinforcement in the lead-free solder alloy through composite technology approach.
