Study On Sintering Behavior Of Multi-Size Cu@Ag Nanoparticles And Their Applications In Printed Electronics

Inkjet printing technology has been considered to be an alternative for application on the field of sensor,thin film transistors(TFT),solar cells and radio frequency identification(RFID)due to its tolerance to substrates,economy and convenience.However,the high price and severe electro-migration of Ag nanoparticles as well as oxidation instability and high sintering temperature of Cu nanoparticles limit their applications.It is a big problem for inkjet printing to achieve great conductive performance with low-cost and low sintering temperature.Furthermore,various substrates which are not thermal instability can be used in the process with good mechanical stability in the meanwhile.In this study,the advantages of Cu and Ag were combined to synthesize multi-size core-shell Cu@Ag nanoparticles(NPs)though a chemical method.A sintering mechanism was proposed by comparing the different structures of Cu NPs and Cu@Ag NPs.Ag merged and dewetted into dependent groups over Cu core,then diffused and sintered into Ag necking between NPs.As the temperature developed,the exposed Cu began to coalesce to form Cu necking,leading to the denser structure.Due to the small size Ag NPs causing by the dewetting and merging of the Ag shell,bigger size Cu@Ag NPs had greater motivation and less sintering time,which means bigger size Cu@Ag NPs could form denser structure than smaller NPs as well as thick Ag shell contributed more than thin Ag shell.In the meantime,the best composition of the inkjet as well as the process of sintering was studied to achieve the best performances.The composition of solvent and solid content of Cu@Ag NPs placed important roles in the effect of printing.Besides,the impact of the temperature of procuring and sintering time to the conductive performance of pattern were analyzed.According to the mechanism,Cu@Ag NPs and Ag NPs were mixed to form a new inkjet.After sintering at 150 ℃ on PI film,the resistivity of the pattern was only 16.12 μΩ·cm,which decreased to 10.99 μΩ·cm as the temperature developed.Furthermore,after thousands time bending,the resistivity of the pattern had little change.This kind of inkjet satisfied the low sintering temperature in inkjet printing technology with great conductive and stability,which means it is promising application prospect on flexible electrical printing.