A study on electrical impedance variations between transducer elements in one-dimensional piezoelectric arrays

摘要

This paper investigates sources for element to element variations in an ultrasound transducer array, measured by electrical impedance. A 3 MHz PZT transducer was made and diced into 53 elements, where the rotation speed of the dicing saw blade was varied between 10 000 and 30 000 rpm. The fabricated array was investigated under optical microscope, and electrical impedances of the elements were measured. A FEM model of the array was made, and parameters in the FEM model were varied to identify the most likely sources of variations. The results show that the frequencies of the main resonance peak deviate within 5%, while the magnitude of the impedance at resonance was found to vary by a factor two. Comparing the measurement to the FEM simulations, it was concluded that the dominating source of these variations is damage of the piezoelectric property close to the kerf, probably do to heating during the dicing. Spurious modes observed in some elements were explained by small amounts of debris in the kerfs. Geometric variations were found to have minor influence on the main resonance peak.