On the Effects of Package on the PMUTs Performances—Multiphysics Model and Frequency Analyses

Abstract

This paper deals with a multiphysics numerical modelling via finite element method (FEM) of an air-coupled array piezoelectric micromachined ultrasonic transducers (PMUTs). The proposed numerical model is fully 3D with the following features: the presence of the fabrication induced residual stresses, which determine a geometrically non-linear initial deformed configuration of the diaphragms and a remarkable shift of the fundamental frequency; the multiple coupling between different physics, namely electro-mechanical-coupling for the piezo-electric model, acoustic-structure interaction at the acoustic-structure interface and pressure acoustics in the surrounding air. The model takes into account the complete set of PMUTs belonging to the silicon die in a 4 × 4 array configuration and the protective package, as well. The results have been validated by experimental data, in terms of initial static pre-deflected configuration of the diaphragms and frequency response function of the PMUT. The numerical procedure was applied, to analyze different package configurations of the device, to study the influence of the holes on the acoustic transmission in terms of SPL and propagation pattern and consequently extract a set of design guidelines.

Air-coupled PMUTs array with residual stresses: experimental tests in the linear and non-linear dynamic regime

“…After the activation and poling treatment, this initial displacement decreases. Furthermore, the static voltage load induces a deformation recovery [11]. As a matter of fact, the system tends to the flat undeformed configuration.…”

“…The numerical modeling of the presented phenomenon is reported in Authors' work [11], where the PMUTs array eigen-modes and frequencies are obtained by means of a proper finite element modeling applied to the device. The value of the applied voltage bias influences the stiffness of the device, through affecting the internal stress state in the diaphragm.…”

PMUTs Arrays for Structural Health Monitoring of Bolted-Joints

“…Piezoelectric materials are used in a wide range of smart micro-systems [ 25 , 26 ]. Unlike bulky piezoelectric transducers, which utilize body modes, PMUTs generate waves through the bending motion of a thin piezoelectric active layer such as PZT [ 19 , 27 , 28 , 29 ]. The resonant frequency of the PMUT can be controlled by properly tailoring the in-plane dimension of the flexural membrane and the thicknesses of the constituent layers.…”

Efficient Modeling and Simulation of PMUT Arrays in Various Ambients

“…The multi-layered system is suspended on a cavity that provides enough space for the flexural movements of the plates. The active layer in the multi-layered system is typically a thin layer of a piezoelectric film made of lead zirconate titanate (PZT) deposited by sol-gel technique in hat configuration on a structural plate made of silicon [2,3]. The generation of the ultrasonic waves comes from the "inverse effect" of the piezoelectric material, causing a displacement in the membranes by applying an AC voltage signal between the electrodes.…”