Preparation And Characterization Of Silver Based Particle-free Conductive Ink And Its Film Formation Investigation

Printed electronics is an emerging technology of manufacturing electronicdevices by printing functional inks. It’s the important innovation of microelectronics.At present, in the field of functional inks, silver based conductive ink has gained a lotof attention owing to its excellent electrical conductivity and strong chemicalinertness of silver element. This kind of ink could be divided into two types: one isbased on silver nanoparticles and the other is particle-free ink. The latter one doesn’tcontain any nanosized silver particles, thus it can obtain high stability even withoutdispersant. It also has low curing temperature, mostly between100℃～200℃,which could meet the requirement of ordinary substrates.In this study, particle-free conductive ink with high stability and low curingtemperature was prepared, taking silver citrate as conductive metal precursor, organicamines as complexing agent and alcohols as media adjusting the viscosity andwettability. The influence of amines on the solubility of silver citrate and amines,alcohols, the ratio of silver and amine and silver content on the thermal behavior andfilm-forming capability of the ink was explored. The results showed that amines withshorter hydrocarbon chain and fewer substituent had stronger capacity to complex anddissolve silver citrate, so conductive ink with high silver content was available usingthese amines; among the substances contained in the ink, like amine, alcohol-amineand alcohol, amine affected greatly the thermal behavior of the conductive ink whilealcohol, the ratio of silver and amine and silver content hardly had an impact on it;reducing agents, such as alcohol-amine and polyols, increased the decompositiontemperature instead of reducing it; both amines and alcohols influenced the wettabilityof the ink and the performance of the silver film.On the basis of the investigation above, conductive ink which could be printingby inkjet mode was prepared, taking1,2-diaminopropane as complexing agent. Theoptimal formula was obtained through orthogonality experiment. Through theexperiment, the conductive ink with optimal formula possessed a good printingperformance and high stability. Silver conductive film with resistivity of17μ cmwas obtained after the inkjet printed pattern on PET substrate was cured for50min at150℃. The adhesion rating of the conductive film on PET substrate was5B, which is the highest level in the standard of ASTM D3359. All these enable this kind ofconductive ink to be of good prospects for application.