Morphology-controlled assembly of silver microstructures for conductive silver paste

Abstract

Conductive silver paste is widely used in photovoltaics and other microelectronic devices owing to its electrical conductivity and processing versatility. Morphology-specific synthesis of silver powder is important for paste formulation. In this study, uniform silver microspheres (Ag-MSs) and microflakes (Ag-MFs) were successfully synthesized via a facile one-step chemical reduction method by systematically tuning the concentrations of silver precursors, reductants, and dispersants. The resulting Ag-MSs exhibited smooth surfaces, excellent dispersion, and uniform particle size distribution, while Ag-MFs displayed thin planar morphologies with high specific surface areas. Structural and compositional analysis identified crystalline silver as the main phase of the as-prepared products. Sodium citrate dosage also influenced particle morphology and aggregation. The mean recovered powder masses from three independent batches were 194.7 mg for Ag-MSs and 34.2 mg for Ag-MFs, corresponding to apparent gravimetric recoveries of 90.2% and 64.7%. To evaluate practical applicability, Ag-MSs and Ag-MFs were composited in controlled ratios to fabricate hybrid conductive pastes. The mean two-terminal resistances of the cured coatings were 2374.0, 79.2 and 184.8 mΩ for Ag-MSs, Ag-MFs and Ag-MS₁MF₁, respectively. At the same total silver loading, the 1:1 hybrid used 50% less flake powder than the all-flake formulation while retaining a lower coating resistance than the sphere-only paste. These results provide a basis for selecting mixed-morphology silver fillers by considering synthesis-stage powder recovery together with coating resistance.