Design of Experiments for Optimizing Silver–Graphene Composite as a Conductive Paste

Abstract

This study presents a systematic optimization of a silver–graphene-based conductive paste by integrating multiple design of experiments methodologies across its three core components: particle synthesis, binder formulation, and final paste compounding. Four key synthesis variables—solvent ratio (BCA/EtOH), ultrasonic power, reaction temperature, and synthesis time—were evaluated using a full factorial design to control the thickness of the carbon layer on Ag–graphene particles. Statistical analysis, including ANOVA and Pareto charts, identified solvent ratio, ultrasonic power, and temperature as significant factors affecting carbon thickness, with time being negligible. Response optimization revealed optimal synthesis conditions that minimize thickness while ensuring uniform dispersion. For binder development, a mixture design approach was employed to determine the ideal proportions of epoxy resin, hardener, and additives. The optimal binder formulation was identified at a ratio of 0.90:0.01:0.09 (Resin:Hardener:Additive), ensuring stability and processability. Finally, Central Composite Design was applied to optimize the conductive paste by evaluating the effects of binder ratio and synthesis temperature on electrical conductivity and shear strength. A total of nine experimental conditions enabled the construction of second-order polynomial models. Statistical analysis confirmed high model significance (P < 0.01) with R² values exceeding 0.95 for conductivity and 0.99 for shear strength. Contour plots revealed that reduced binder content improved conductivity, while both higher binder ratio and temperature enhanced mechanical strength. The optimized conditions achieved a balance between electrical performance and structural integrity, demonstrating the efficacy of the CCD approach for multivariable paste optimization.