TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The step of forming mixed solution comprises adding: at least one of cellulose-based resin, acryl-based resin, epoxy resin, vinyl-based resin, imide-based resin, amide based resin or butyral resin to the mixed solution; and a thixotrophic agent and a leveling agent to the mixed solution. The method-I further comprises adding at least one of thixotropic agent and a leveling agent to the reaction composition. The step of forming mixed solution comprises: injecting terpineol into the reactor, dissolving toluene, ethyl cellulose (preferred), cellulose acetate derivatives, and methyl methacrylate polymer into the terpineol, and adding copper nano particles having a particle size of 10 nm or less while lowering a temperature applied to the reactor; injecting butyl carbitol into the reactor and adding copper nano particles while dissolving hydroxypropyl methylcellulose and ethyl methacrylic acid polymer in the butyl carbitol; mixing terpineol, dihydroterpineol, and neodecanoate in the reactor, and dissolving ethyl cellulose, butyl methacrylate, and ethyl methacrylic acid polymer in the reactor while lowering a temperature applied to the reactor; and injecting terpineol into the reactor, dissolving butyl carbitol, cellulose acetate, and hydroxy propyl cellulose in the terpineol, and adding dioctyl phthalate and a surfactant to the reactor.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The step of preparing the substrate comprises preparing a substrate for a solar cell, in which a transparent conductive oxide is deposited, or preparing a polyimide substrate for a printed circuit board. The step of coating the copper nano paste comprises coating the copper nano paste on a polyimide substrate for the solar cell using a screen printing process. The step of calcining the copper nano paste comprises reduction-calcining the copper nano paste under an atmospheric temperature of 180 degrees C. The step of preparing the substrate comprises preparing any one of a silicon substrate, a polymer substrate, a glass plate, and a printed circuit board.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The capping material comprises at least one of fatty acid or fatty amine. The additive comprises a thixotropic agent and a leveling agent.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The binder comprises at least one of cellulose-based resin, acryl based resin, epoxy resin, vinyl-based resin, imide-based resin, amide-based resin, or butyral resin. EXAMPLE - Ethyl cellulose (2 g) was added to terpineol (41 g) in a reactor and dissolved by heating at a temperature of 60 degrees C. When the ethyl cellulose was completely dissolved, copper nano particles (220 g) having a particle size of 10 nm or less was slowly added, while lowering the temperature applied to the reactor to room temperature. Then, the obtained mixture was worked up to give a copper nano paste having a viscosity of 5500 cP by passing the copper nano particles through a triple roller mill.