Effects of amine types on the properties of silver oxalate ink and the associated film morphology

Silver conductive ink using silver oxalate as silver precursor has attracted considerable research interest due to its unique properties. However, silver oxalate has poor dissolvability in organic solvents and high thermal decomposition temperature, the latter is not desirable for pattern formation on some low cost polymer based flexible substrates. In this paper, different kinds of alkylamine were chosen as ligands to formulate silver oxalate inks to address the mentioned issues. The role of amines in silver oxalate based inks was studied in detail. The influence of amine types on thermal property, stability and electrical performance of the formulated silver oxalate inks was investigated. The relationships between them were established and elucidated. The results show that highly conductive silver films with controlled microstructure features can be achieved for low temperature sintering by selection of an appropriate amine as the latter has a strong influence on the decomposition temperature of the formed silver–amine complex and it determines the nucleation and growth of silver particles in the film formation process. The chemical reactions occurring within the ink were also studied. An optimal silver complex ink was prepared by using blended amines as ligands finally, producing a uniform silver film with good quality and favorable conductivity at 150 °C. The results are important for future design of stable and high conductive silver complex inks for practical applications.