Study On The Fabrication Process Of SU-8 Chamber For Piezo Inkjet Print-head

Inkjet printing has become an indispensable technology with characteristics of non-contact,non-pressure and high efficiency,which has been gradually expanded from traditional graphic printing to industrial manufacturing field due to its rapid development.However,the core technology of inkjet printing has always been monopolized by foreign countries,and China lacks independent intellectual property rights in the inkjet printing field.As the pressure transmission and ink storage component of inkjet print-head,the chamber studied in this paper plays an important role in the formation of ink droplets and stable ejection.In this paper,the fabrication process of SU-8 integrated chamber was studied.The main research contents are as follows:(1)SU-8 negative photoresist was selected as the material of inkjet chamber by analyzing working environment of the inkjet chamber and properties of materials in the field of MEMS.Aiming at fabrication process problems of chamber blockage and poor experimental repeatability of conical nozzle,a fabrication method combining hot embossing and thermal bonding process was proposed for manufacturing SU-8 integrated chamber,and the overall structure and working principle of piezoelectric inkjet print-head were introduced.(2)According to strength theory,the effect of macroporous layer structure on thermal residual stress of monocrystalline silicon substrate in the process of thermal bonding was analyzed,and the macroporous layer structure was optimized by COMSOL finite element simulation.By adding stress relief structure to macroporous layer,the maximum thermal stress and deformation of silicon substrate,which were positive linearly correlated with the thickness of macroporous layer,were reduced by 56.7%and 48.8%respectively.Experiments was carried out and simulation results were consistent with experimental results.Based on the interface adhesion strength theory,ultrasonic development principle and SU-8 photoresist crosslinking mechanism,the process parameters of macroporous layer were optimized through experiments.Finally,the SU-8 macroporous layer with stress release structure,aperture of 150?m,thickness of 150-200?m and incompletely crosslinking degree was fabricated.The macroporous layer prepared with these parameter achieved 100%through hole rate,high bonding strength and no fracture failure of monocrystalline silicon substrate.(3)The mechanical properties of thermoplastic polymer and Maxwell viscoelastic model were analyzed to provide theoretical basis for reproduction quality.D_c(offset of conical nozzle)and R_h(filling ratio)were defined as the evaluation indexes of replication accuracy.The effect of thickness of imprinting photoresist,hydrophobic time of SU-8 master mold and hot embossing parameters on reproduction quality were analyzed,and the fabrication process parameters were optimized by experiments.Finally,the perfect reproduction quality of SU-8conical nozzle,of which large aperture was 40.01±1.24?m,small aperture was 27.12±1.07?m,the nozzle height was 50±1.26?m,R_h was 97.7%and D_c was 0.735?m,was successful fabricated by hot embossing technology based PDMS soft mold.(4)The process of integrated inkjet chamber was introduced in detail:the SU-8 open chamber on the silicon substrate was prepared by lithography process;the macroporous layer was bonded to open chamber by two-step thermal bonding processes;the nozzle plate fabricated by hot embossing was bonded to chamber with macroporous layer to form integrated SU-8 inkjet chamber.The ink filling and ink-jet est of piezoelectric inkjet print head was performed,and test results achieved 100%ink filling rate and ink droplet ejection.