Enhancement of Processability and Electrical Resistance by Use of Ag-Based Composite Inks Containing Ultrafine SAC305 Alloy Nanoparticles

We propose use of Ag/Sn-3.0 (wt.%) Ag-0.5 Cu (SAC305) composite ink to reduce sintering temperature, sintering time, and material costs. The SAC305 nanoparticle (NP) surfaces were not capped by any stabilizers, which are detrimental to the resistivity of the sintered tracks. Compared with commercial pure Ag ink, use of Ag/3.2 (vol.%) SAC305 composite ink containing ultrafine SAC305 NPs resulted in outstandingly enhanced processability, enabling faster sintering at low temperatures. The average sheet resistance of composite ink samples sintered for 25 min at 170°C was as low as 0.011 Ω/□, comparable with that of a pure Ag sample sintered for over 30 min at 220°C. The morphology and the differential scanning calorimetry curves enabled explanation of the changes in the sintering behavior and sheet resistance. The Ag/SAC305 clusters in the composite ink sintered at 170°C grew, on average, to ~201.1–226.1 nm as a result of faster local liquid-phase sintering, and most of the Ag particles were mutually linked, dramatically changing the microstructure.