Design And Fabrication Of The Chamber For Piezo Inkjet Print-head

Inkjet printing technology has become an indispensable technology in the daily life due to its unique advantages.Its application is also increasingly widespread,from the traditional image printing extending to flexible integrated circuits printing,electrochemical cell printing and bio-chip printing.The inkjet chamber is an important part of the inkjet print-head,and its fabrication method directly determines the quality of droplets,droplet jetting behavior and controlling jetting process.In this paper,the method combining ultraviolet(UV)photolithography and thermal bonding was utilized to fabricating chamber for piezo inkjet print-head.(1)According to the material properties and requirement of fabricating inkjet chamber,many materials were compared,such as PDMS,Parylene,PMMA,PI and SU-8 photoresist.Finally,the SU-8 photoresist was chosen as chamber material owning to its excellent physical and chemical properties.(2)The each part dimension of the inkjet chamber was optimized based on Piezoelectric vibration theory,fluid theory and simulation by COMSOL.The dimension of inkjet chamber designed by this paper is 1000×120×140?m,the restrictor's is 1500×35×140?m,the nozzle's is conical with the outer diameter of 20?m and the inner diameter of 30?m and the height of nozzle plate is 40?m.(3)The parameters of thermal bonding was determined by thermal bonding principle,crosslinking theory and polymer mechanical properties.The crosslinked degree of nozzle plate directly determined its glass transition temperature(Tg)and Young's modulus which influence the chamber deformation rate,bonding strength and bonding rate in the bonding process.The crosslinked degree of nozzle plate was optimized by experiment.Finally,the bonding parameters are bonding temperature of 85?,bonding pressure of 80 KPa and bonding time of 10 min.The optimal nozzle plate parameters are softbake temperature of 75? and crosslinked degree of 40%.(4)In this paper,three kinds of optical exposure methods were analyzed and the proximity exposure method was proposed to fabricating conical nozzle.The diffraction model was set up by the MATLAB,according to the Fresnel diffraction theory.The influence of light intensity distribution and exposure gap on the conical nozzle was analyzed,and the exposure gap was optimized by experiment.Finally,the nozzle plate with outer diameter of 20?m,inner diameter of 30?m and height of 40?m was fabricated using the mask diameter of 30?m and exposure gap of 30?m.(5)The fabrication process of piezoelectric inkjet chamber was described in detail.Firstly,the open chamber was fabricated using fully crosslinked SU-8 photoresist on the Si substrate.Secondly,the nozzle plate was fabricated using soft crosslinked SU-8 photoresist on the PDMS substrate.Finally,the open chamber and the nozzle plate were aligned under the bonding alignment device and bonded with pressure and temperature.With this method,not only the high bonding strength,but also the ideal nozzle diameter and groove can be achieved.Also it shortens the manufacturing cycle and solves uncompleted development of chamber and nozzle clogging.etc.In the end,the ink-charge test and ink-jet test were carried out on the chamber of piezo inkjet print-head and the droplet injection process was observed successfully.