Driving Technology Of Piezoelectric Thick Film Compatible With MEMS

Micro-driving technique plays a key role in the scope of MEMS-based actuators. Furthermore, Driving technology of PZT thick film compatible with MEMS has been, and still is, thought as a promising technology in the micro-driving field. Based on experiments and theory discussion, several study contents have been extensively investigated, including: PZT thick film fabrication processes; tests of PTZ thick film driving characteristics; optimizing designed of silicon-based PZT thick film structure; compatible processes of valveless micro pump using PZT thick film.Based on screen printing technology, PZT thick film molded using silicon wafer was succeeded. It was proved that anneal-overprint method could increase the film density. SEM and EDX were employed to analyze the components, structures and the inter-diffusion phenomenon between the PZT and the substrates. By optimizing the screen printing procedure of the silicon-based PZT thick film, the sintering temperature was dropped to 850℃.A couple of new structures, double cups on silicon substrate PZT thick film driving structure and silicon-based distributed PZT thick film driving structure were formed using the following processes: the screen printing technique, the MEMS technology such as thermal oxidation, optical lithography and deep wet etching. These structures are suitable to the in-chip driving MEMS actuators. Thus the bad compatibility between piezoelectric thick film driving and MEMS processes can be easily resolved.The piezoelectric constant d31 is chosen to characterize the piezoelectric driving characteristic of the silicon-based PZT thick film. The piezoelectric constant d31 of the film is -77.4×10-12 m/V using cantilever beam optical testing method. The volume density is 3592 g/cm3 tested by buoyancy method. The results showed that the silicon-based PZT thick film had certain piezoelectric driving capacity and the density of it by screen printing method was much smaller. Moreover, such testing methods can also be applied in other PZT thick film devices tests.The FEA software ANSYS was used to optimize the driving structure of the silicon-based PZT thick film. The static deformation and the mode frequency characteristics of silicon-based PZT thick film were compared with those of the piezoelectric ceramic on the copper substrate. Structure parameters of these PZT thick film devices on double silicon-cup substrates were optimized. The shape, structure, position and distribution of the silicon-based PZT thick film were also analyzed. Then the influences of static and mode driving of the Si-based PZT thick film were discussed. As a result, the optimized structure parameters valuable for micro-actuators were gained.A novel simple valveless micro-pump structure with PZT thick film was provided according to the orifice flow phenomenon of the engineering hydrodynamics. A PZT thick film on the double silicon cup substrate is used as a driving component. A micro-channel of such micro-pump inlet/outlet is substituted for a one-way valve of the valvate micro-pump inlet/outlet, so when the unsymmetrical triangle wave is applied the micro fluid can be commutated. The fabrication processes of a micro-pump include oxidation, double-side lithography, deep wet etching, anodic bonding, electrochemistry punching, and the PZT thick film screen printing. The micro-pump is proved to have certain pumping capacity. The screen printing PZT thick film method can be used to fabricate micro-pumps. It is proved that the PZT thick film can be applied in manufacturing micro-actuators.It was also found in this dissertation that the valveless micro-pumps using the piezoelectric ceramic as driving element had better pumping performances. As demonstrated in the dissertation, the design of the valveless micro-pump structure considering the macro orifice flow phenomenon is significant in academic study of micro-channel fluid flowing performances.