Study On The Fabrication Of Ink Chamber For Piezo Inkjet Printhead

The application of inkjet printing technology has spread from traditional to commercial printing and other fields, such as flexible integrated circuit, electrochemical cells, bio-cell printing. The ink chamber is a significant part of a piezo inkjet printhead, but the fabrication process of ink chamber is complex, time-consuming and reliant on special equipment. This paper describes a fabrication method for ink chamber based on SU-8 dry film lamination which is simple and only common equipment is needed. The following is the main research contents in the paper.(1) The material for fabricating ink chamber was selected. The thickness of nozzle plate was optimized. By analyzing the characteristic of the common materials in MEMS, the SU-8 negative photoresist was chosen to fabrication the ink chamber as its excellent physical and chemical properties. According to the piezoelectric vibratory plate theory and the fluid theory, the thickness of the nozzle plate was optimized and the stress nozzle plate suffered during the inkjet process was analyzed by numerical simulation in COMSOL software.(2) A method to fabricate the ink chamber for piezo inkjet printhead by dry film lamination was presented. The mechanical behavior of polymer during the bonding process and interface adhesion mechanism of polymer were analyzed. The main parameters of the lamination process were optimized. The bonding temperature of 60 ? and the dry film thickness of 20 um were chosen to achieve 100% bonding rate and 92.5% rate of through nozzle. And oxygen plasma process was optimized at RF power of 40 W and time of 25 s to improve the dry film lamination strength.(3) Fabrication process of ink chamber for piezo inkjet printhead was illustrated in detail. By improving the spin coating fixture and parameters of spin coating, the thickness error of SU-8 caused by edge bead was reduced. The inner stress of SU-8 generated during the baking process was decreased by the soft bake temperature rising and dropping slowly, and PEBwas taking at a low temperature instead of recommended temperature. The PDMS sheet was chosen as the substrate of the dry film. The 20 um thick dry film with the exposure dose of 189?210 mJ/cm2 and the PEB temperature of 65? and time of 10 min achieved the highest through nozzle rate and steady properties. The nozzle plate achieved the optimal thickness by two step lamination.(4) The bonding strength was tested by pumping compressed gas into chamber. And ink-charging test and inkjet test were operated on the inkjet test platform. There was no gas leakage in the test chamber fabricated by dry film lamination with compressed gas pressure of 0.7 MPa more than 10 min, while the maximum instant pressure the nozzle plate suffered was 0.543 MPa during inkjet. The ink chamber was charged by ink successfully and the piezo inkjet printhead realized inkjet on the inkjet test platform.It is expected that this method has a high potential for manufacturing ink chambers for inkjet printhead.