This study investigates the effect of various geopolymer ceramic particles addition in matrix SnCu solder paste on its geopolymer ceramic’s microstructure and their mechanical properties after being reinforced in solder alloy. The composite solder was prepared by mechanically mixed 1.0 wt.% geopolymer ceramic powder into SnCu powder and compacted via powder metallurgy (PM) technique. Based on microhardness results, the presence of slag geopolymer shows an improvement after being reinforced with SnCu.