Preparation And Property Of Copper Formate Based MOD Conductive Ink

With the rapid development of microelectronics manufacturing,printed electronics has been challenging conventional methods.Among the printing methods,inkjet printing is expected to replace the conventional methods in some files as the next generation of manufacturing technology due to its advantages of no-printing forme,low-cost and flexible manufacturing.In the inkjet printing process,small droplet of functional inks were produced and deposited directly on the substrate to form a specific structure under the digital control and obtain electronic devices after the post-processing.The advancement of functional inks,especially metal inks,is the premise to applying inkjet printing to practical production.Currently metal interconnect lines which created by silver based conductive inks have been widely used in thin film transistors,RF inductors,sensor and other devices.However,due to the high-cost and electromigration,silver based conductive inks are limited in the scale application.Comparing with silver,copper has a similar resistivity moreover it is cheap and low electromigration.Therefore copper base conductive inks are considered to be the best alternative to silver based conductive inks.Among the copper based conductive inks,copper MOD inks has attracted more attention to researchers because of strong stability,low processing temperature and non-blocking nozzle.In this work,copper formate tetrahydrate was used as metal precursor and1,2-Diaminopropane,isopropylamine,butylamine,Octylamine,ethanolamine were respectively used as complexing agent to formulate copper MOD conductive inks.It found that complexing agent have a great influence on thermal decomposition temperature,stability of conductive films and resistivity,morphology,organic residue of conductive film.When using 1,2-Diaminopropane as complexing agent,the conductive ink accessed maximum stability and the prepared conductive thin film showed the lowest resistivity about 10.5??·cm.At the same time,its low thermal decomposition temperature can meet the heat resistance requirement of most flexible substrates.Therefore,1,2-Diaminepropane was identified as the optimal complexing agent.But bubbles and dewetting phenomenon resulted in a fragmentized film with a lot of void and gaps.The formulation of conductive inks was further improved.Octylamine was added to the ink to effectively weaken the dewetting of the ink and aggregation of copper nanoparticles.And CuF/octylamine complex could be thermally decomposed to copper nanopaticles with 0.03?m particle size.The small copper nanoparticles filled the voids and gaps between the large copper nanoparticles from the thermal decomposition of CuF/1,2-Diaminopropane complex,leading to a uniform and dense copper conductive film.In addition,octylamine would increase the resistivity and decomposition temperature.Considering these factors,we determined that the optimal 1,2-Diaminopropane/Octylamine ratio is 1:2.The heat treatment conditions had a significant effect on the performance of the conductive films.Whether improving heating treatment temperature or extending heat treatment time,the resistivity of conductive thin film had a variation trend that declined sharply at first and then held steady.The resistivity of conductive film obtained by heating conductive ink at 150? for 40min was 28.1??·cm.We have prepared conductive films on flexible polyimide substrate and heat treating at 150? for 40min,indicating a resistivity of 29.9??·cm.The adhesion between copper film and polyimide was 0B.We further explored the effect of adhesive on the adhesion and resistivity of conductive film.The experimental results have shown that the optimal amounts of EC and PVP were 2.5%and 1%respectively.The resistivity increased to 36.8??·cm and 36.6??·cm and bond grade were 2B and3B respectively.Moreover the mechanical stability has been enhanced.