Electrophoretic deposition of insulation layers for termination process of PNN-PZT multilayer actuator

The termination process of PNN-PZT multilayer piezoelectric actuator is similar to that of multilayer ceramic chip capacitor. However, the insulation layers are required to cover the end surface of fine inner electrodes at the termination step to meet multilayer actuator requirements such as better piezoelectric performance and longer device life. Electrophoretic deposition (EPD) technique is used to cover every other fine inner Pd-Ag electrodes (similar to 3 mu m) with zinc borosilicate glass powder on two sides of multilayer actuator. The EPD technique offers some attractive features for film deposition such as process simplicity, lower equipment investment, patterning capability and fast deposition rates for both oxide and non-oxide films. The effects of tetramethylammonium hydroxide (TMAH) and nitrocellulose (NC) introduced in the suspension, containing the glass particles in the ethyl acetate and isopropyl alcohol solvent, on the suspension stability and electrophoretic deposition efficiency were studied. The electrophoretically deposited Zn-B-Si-O glass insulation layers sintered at 660 degrees C result in the insulation layer of 25 similar to 35 mu m thickness and 80 similar to 100 mu m width under various EPD process parameters. The glass layers coated on fine inner electrodes by EPD method at termination step for packaging of multilayer actuators exhibit reasonably dense, high resistivity and good adhesion.