Effect of kaolin geopolymer ceramic addition on the properties of Sn-3.0Ag-0.5Cu solder joint

Abstract

This paper investigates the effects of different weight percentages (0, 0.5, 1.0, 1.5 and 2.0 wt.%) of kaolin geopolymer ceramic (KGC) on the microstructure formation, thermal properties, spreadability and joint strength in Sn-3.0Ag-0.5Cu (SAC305) lead-free solder alloys in order to develop a new composite solder system. Advanced characterization techniques such as Electron backscatter diffraction (EBSD) and synchrotron micro-XRF were used to study the behaviors of the pure SAC305 and KGC reinforced SAC305 composite solders. Experimental results shows that the addition of KGC refines the β-Sn area and increases the eutectic area with fine intermetallics formation. In addition, the thickness of the IMC layer is reduced with a reduction in undercooling value for the KGC reinforced SAC305 composite solder. The spreadability of the KGC reinforced SAC305 composite solder is significantly increased in the spreadable area with a higher strength of solder joint. Significantly, the results obtained prove that 1.0 wt.% KGC addition gives better performance in terms of microstructure formation, thermal properties, spreadability and joint strength. Synchrotron micro-XRF interestingly indicated that some Al and Si, which are the major elements in geopolymer systems, migrate into the solder area.