Study On Vibration Characteristics Of Piezoelectric Driving Structure In MEMS/GMR Magnetic Sensor

Vertical motion flux modulation structures in the GMR magnetic sensor can suppress 1/f noise efficiently.But in practical the output signal of the sensor is unstable and cannot reach the expected performance,thus the study of characteristics of piezoelectric drive structure which is closely linked to the output signal is urgent.In this paper,the thermal characteristics and quality factor of the piezoelectric driving structure vibrating in its first order are studied using theory,simulation and experiment methods,and the main work is as follows:Based on theory of elasticity and piezoelectric equations,the kinetic equations are build,which establishes the theoretical foundation for solving the multi-physics coupling of the thermal characteristics and the vibration theory considering damping for quality factor characteristics.The stability of vibration frequency and amplitude are investigated in theoretical analysis and simulation method considering thermal stress,Young's modulus' temperature coefficient and thermoelectric coupling,and the main influence factors are also given.In terms of the rate of vibration amplitude change by temperature,the method of replacing the dynamic amplitude change rate by the static displacement change rate is proposed,which greatly simplifies the difficulty of analyzing.Based on Joule heat and heat consumption due to damping,the distribution and influence of temperature are studied,and the influence of temperature gradient is further investigated.The results show that Joule heat is the main heat source,and temperature gradient is the major influence factor.The simulation method on quality factor of the multilayer structure is proposed,and it is verified by experimental results on the quality factor of piezoelectric cantilever.Then the quality factor of piezoelectric driving structure in the sensor is studied based on the simulation method,obtaining that the quality factor is about 50 and it can be improved through decreasing the thickness,length of piezoelectric layer,the damping ratio of adhesive layer and increasing of Young modulus of adhesive.