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This paper presents a design optimization of a membrane-based ultrasonic piezoelectric transducer using micromachining by finite element simulation. The transducer can be used to generate ultrasound using the piezoelectric film to excite the vibration of the transducer membrane. The objective is to maximize the vibration magnitude of the membrane by optimizing the structure of the transducer, when the exciting signal is fixed. The size and the shape of the piezoelectric film were selected as the design parameters to optimize the structure of the transducer. Based on the theoretical analysis, it is found that the absolute values of the stresses in the center and the boundary of the diaphragm are greater than that on the other regions of the film, with the directions of the stress on center and boundary opposite to each other. In order to achieve the maximum exciting efficiency, the discrepancy in the stresses between the center and the boundary on the diaphragm should be maximized. In this paper, totally four different piezoelectric film structures are analyzed for optimizing the exciting efficiency of the transducer. The finite element models of the transducer were created using ANSYS. The simulations based on the three design options were performed; and through the comparison of the simulation results, the optimal structural parameters of the piezoelectric film are identified. Finally, the direction of the design improvement for the exciting efficiency of the transducer is provided.

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With the miniaturization of mobile electronic devices, the flexible electronics are being used more and more in the industry, such as the flexible printed circuit (FPC) and flexible displays [1]. With the products becoming flexible and bendable, the reliability could become a serious issue in some cases if not designed properly. Examples of such concerns are bending and impact reliability. Unfortunately, there is no any systematic method for analyzing the reliability of the flexible electronics that we want to follow at this stage. In this paper, the reliability of the FPC and the flexible displays are discussed. Specifically, ball drop simulation, and three-point bending and twisting simulation are used to analyze the reliability of the flexible displays; and simulations of bending FPC with different component layout patterns are computed in order to understand the mechanical behaviour of the FPC under the corresponding load conditions. Based on the comparison of maximum von Mises stresses, design suggestions are given. Moreover, based on the practical design of the flexible device, a simulation method for bending the device along wrist is presented to simulate the phenomena within the device during its practical use. At the same time, system level simulation model is built to simulate the assembly process. Finally, according to the simulation results, the device reliability is evaluated and design suggestions are provided.