Electronic Circuit Printing, 3D Printing and Film Formation Utilizing Electrostatic Inkjet Technology

An investigation has been carried out on the control of a micro-droplet in electrostatic inkjet phenomena, because the electrostatic inkjet has a merit that the formation and locus of the droplet can be controlled by the application of the electric field and it is possible to treat highly viscous liquid. It was observed that a Taylor cone of the paste was formed at an end of a tube and the tip of the cone was broken to form a very small droplet at the beginning of the corona discharge. Droplets of paste that contains Ag nanoparticles are injected on a glass substrate to form electrode patterns. The formation of the droplet is controlled by the application of pulse voltage between the plate electrode and the fine tube that is filled with Ag paste. A multi-layered printing was realized by over-coating insulative glass paste on line electrodes. A direct 3D printing was also developed by taking advantage that highly viscous liquid can be ejected by the electrostatic inkjet system. Introduction We have been developing a mask-less printing technology for microelectronic circuits, film formation for coating technology, and three-dimensional micro rapid-prototyping utilizing an electrostatic inkjet system.[1][2] In the mask-less printing, drops of paste that contains Ag nano-particles are injected on a glass substrate by electrostatic force to form electrode patterns.[3] The formation of the droplet is controlled to realize the drop-on-demand (DOD) by the application of pulse voltage between the plate electrode and a fine tube that is filled with Ag paste. On the other hand, liquid is dispersed under a certain condition due to electrostatic instability and Coulomb repulsive force between dispersed droplets. This phenomenon is investigated to utilize for the micro coating technology. The last application is a 3D printing. Because highly viscous liquid can be ejected with the electrostatic inkjet system, it is expected to be utilized for the micro rapid-prototyping and manufacturing of a micro-mold for casting. In this study, we have investigated fundamental characteristics of the system to apply for these digital fabrication technologies. Experimental An experimental set-up shown in Fig. 1 was constructed to investigate characteristics of droplets formation.[2][3] A capillary tube made of silica coated by polyimide (PolymicroTechnologies, Phoenix, AZ) was equipped with a bottom of a syringe. This tube with liquid was hanged down perpendicular to a plate electrode made of stainless steel. DC voltage was applied by a DC power supply (Matsusada Precision Inc, Tokyo, HVR-10P) and pulse voltage was generated with a function generator (IWATSU, Tokyo, SG-4105) and a high voltage amplifier (Matsusada Precision Inc, Tokyo, HEOP-10B2). The voltage was measured by a digital gap 3