Preparation Of Organic Acid Silver Based Particle-Free Conductive Ink

Printed electronics is a technology that uses traditional printing methods to manufacture circuits and electronic components.Compared with traditional circuit manufacturing methods,printed electronics is expected to be used to manufacture flexible electronic devices because of its simpler process and lower cost.The technology of printed electronics is mainly influenced by conductive ink and printing process.As a traditional craft,printing has been developed for hundreds of years and is very mature.The most critical issue to be addressed is the ink development and the most important component of conductive ink is the conductive component.To date,metals,conductive polymers,carbon materials and composites have been developed as conductive components in conductive ink.Among them,metals have become the mainstream of research due to their excellent electrical conductivity.Silver has the best comprehensive performance and is therefore most often used.Silver-based conductive ink can be divided into particle conductive ink and particle-free conductive ink according to the existing form of silver.Particle-free conductive ink has the advantages of simple process,low cost,low heat treatment temperature and high silver content,so it is the focus of research.Metal-based particle-free conductive ink also can be called MOD（metal-organic decomposition）ink.In this paper,we used organic acid silver as silver resource to prepare two types of particle-free MOD conductive ink with different viscosity for different printing methods.We also studied the heat treatment temperature and time of conductive inks,and finally found that:（1）The conductive ink was prepared with silver malonate as silver precursor,diethanolamine（DEA）as complexing agent and ethylene glycol as solvent.Silver malonate can be well dissolved when the molar mass ratio of silver malonate to DEA was 1:4.The ink was suitable for screen printing when the silver content was 20%.After heat treatment at 150°C for 1 h,the electrical conductivity of silver film can reach 1×10⁴ S·cm^-1,which corresponded to one sixty-third of the theoretical conductivity of bulk silver.（2）Low viscosity conductive ink was prepared by replacing DEA with ethanolamine（MEA）as complexing agent because MEA has lower viscosity.Through scanning electron microscopy,it was found that silver particles were not well connected to each other,so that the microstructure of the silver film was not dense,resulting in a lower conductivity of the silver film than that of silver malonate-DEA system.Subsequently,it was decided to replace the silver precursor for research.（3）The low viscosity conductive ink was prepared with silver succinate as silver precursor,MEA as complexing agent and ethylene glycol as solvent.Through scanning electron microscope,it was found that silver particles were fused tightly with each other,and the conductivity of the silver film was better than that of silver malonate-MEA system.