Electrohydrodynamic Jet Printing Of Sintered Type Silver Ink

Sintered type silver ink has been widely applied in photovoltaics and piezoceramics due to its distinctive electrical and mechanical properties.It requires thermal-field to hold its original patterned feature instantly when it is processed.The formation process is the key to improve the electrical and mechanical properties of the patterned structure.This paper presents a high temperature electrohydrodynamic jet（HTEJ）printing technique for direct printing high aspect ratio micro-scale silver structures using sintered type silver ink.It makes use of an external electrical field force to form a focused jet and enable produce smaller feature using large sized nozzle.A thermal field was combined in the electrohydrodynamic jet printing process,in order to accelerate volatilization of the solvent in the just printed structure and hold its original printed feature.Based on this technique,the experimental research on the HTEJ printing of sintered type silver ink is carried out,and the main research contents are as follows:First of all,one type of sintered type nano silver ink was chosen for HTEJ printing,which physical properties were tested before the experiment.An unique equipment with a controllable heating platform and a nozzle fixture were designed and produced for HTEJ printing of sintered type silver ink.The flatness and temperature uniformity of the heating platform were measured to make sure it meets the HTEJ printing requirement.Besides,through the LabVIEW programming development environment,a printing control program was written to realize the independent and coordinated control of each functional module and meet the requirement of real-time observation.Then,based on the HTEJ printing equipment and the sintered type silver ink,the printing parameters of temperature,electric strength,flow rate,printing height and substrate motion speed have been investigated to achieve stable jet and desired printed silver structures.Finally,according to the analysis of the working parameters above,silver micro-electrodes were produced on the multicrystalline silicon wafer covered with silicon nitride film using the HTEJ one-step printing technique.Thermal treated process was researched to increase the packing density and electrical conductivity of the printed silver structures.It was demonstrated that the HTEJ printed silver structure has a width of 50μm,an aspect ratio of 0.4,a resistivity of 6.5μ?·cm,a contact resistivity of 0.32?·cm².Furthermore,the 3D silver micro-pillar with diameter of 20μm was controllably produced using the HTEJ microdripping printing mode.Statistical analysis of the experiments can draw a conclusion that the growth rate of the height of the printed silver micro-pillar is about 30μm·s^-1 in this printing condition.