Papers by Keyword: Ultrasonic Transducer

Abstract: This work reports the acoustic evaluation of a tungsten-epoxy composite which is functioned as a backing material of an ultrasonic transducer. The composite is prepared by mixing tungsten powder in epoxy at a weight ratio of 4:1 using a shaker milling and curing the mixture under a vacuum condition. The sound velocity and acoustic attenuation in the prepared composite is measured by propagating a 200-kHz ultrasonic wave with a through transmission mode. The prepared composite is subsequently assembled with a 1-MHz piezoelectric disk (PZT-8) and an epoxy layer as the active element and the matching layer, respectively, into a fabricated ultrasonic transducer. A square-wave burst pulse is used as an excitation signal for the evaluation of the fabricated transducer. The generated ultrasonic wave shows a higher damping in the presence the backing layer. In addition, the measured sound velocity and acoustic attenuation of prepared composite showed that the ratio of 4:1 is sufficient composition in order to apply as a backing material. In conclusion, control the transducer characteristics is determined by the acoustic properties of tungsten-epoxy composite.

Abstract: Silicon micromachining techniques developed over the last few decades’ aid in precise control over nanometer scale structures. Using these techniques to fabricate transducer elements with small electrode spacing efficient and broadband ultrasonic air transducers can be made. In this paper frequency response profile of a circular capacitive micromachined ultrasonic transducer (CMUT) element with silicon nitride as the membrane material is analytically modelled and compared with FEM simulation results. It is observed that the resonance frequency is highly dependent on the membrane material and structural properties. Silicon nitride serves as an excellent material for generation and detection of ultrasonic waves in air. The results are compared with published experimental values and appreciable agreement is obtained.

Abstract: The generation and detection of ultrasound in air has many applications in the field of ranging, non-destructive evaluation, microscopy and the most impactful in medical imaging. Conventional designs of electrostatic transducers have large electrode spacing of 50-100 μm which reduces the sensitivity of these capacitors. In the last one and a half decade silicon micromachining is used to define capacitors with gap spacing as small as 500Å, making it possible highly efficient capacitive micromachined ultrasonic transducers (CMUTs). In this paper a CMUT element is analytically characterized and FEM simulated. The observations are compared with published experimental results and excellent agreement is found between them.

Abstract: The model of ultrasonic propagation through contact interface, which is an important factor in the ultrasonic transducer used in wire bond, was established by Hertz contact theory. From the Hertz contact theory, it is found that higher order harmonic wave and waveform distortion occur when the ultrasonic wave propagate through a contact interface between two isotropic solids pressed together. Based on the model, the effect of the contact interface between horn and capillary in wire bond transducer are tested by Laser Doppler vibrometer. The experiment results show that when contact interface pressure is in the range of 6 kPa to 10 kPa, higher harmonic wave and nonlinear coefficient is minimum. When contact interface pressure is more than 10 kPa, the nonlinear coefficient increases and bonding strength decreases as increasing of the interface pressure.

Abstract: The basic principle of ultrasonic with time difference method of wind speed measurement was introduced, the design of ultrasonic anemometer based on ARM+Vxworks and its hardware, software and implementation were given. The system has the advantages of high accuracy, simple operation, intuitive display, scalability etc.

Abstract: When the ultrasonic transducer forwardly operates, it needs excitation signal to produce ultrasonic wave. We analyzed the ultrasonic transducer and learned from the experience in the actual project. And got two plans to drive the ultrasonic transducer through the pulse excitation and resonance methods. Both plans have been used in the current wind speed and flow rate measurements. Both are stable, feasible and reliable.

Abstract: The performances of ultrasonic testing systems are greatly affected by the impedance characteristics of ultrasonic transducers. Conventional methods for designing matching networks consider only the characteristics of matching elements and transducer, while ignoring the effects of other elements of emission circuit. As a consequence, such method cannot give out satisfactory results. In this paper, a modeling method for ultrasonic driving circuits is proposed, which takes into account the power supply, the transformer, the matching networks, as well as the ultrasonic transducer. This method focuses on the performances both in time domain and in frequency domain. A computer simulation and experiments show that this method can provide better attenuation characteristics and energy transmission, and can be widely used for analyzing and designing matching network for ultrasonic testing systems.

Abstract: The ultrasonic transducer converts electrical energy into mechanical vibration, and its vibration characteristics have a great effect on the bonding quality. Bond grid arrays (BGA) application and the ability to decrease the temperature of the wire bonding process urgently demand higher bonding frequencies. The ultrasonic transducer working at 135 KHz has been designed, simulated and tested. Based on electromechanical equivalent circuit theory, the dimensions of the transducer were designed. Through finite element method (FEM), the dynamic characteristics of the transducer were investigated. The 5th order axial mode of the transducer resonating at 133 KHz is the working mode. The undesirable modes near the working mode have a great influence on the quality of bonding and must be considered carefully in system design. At last, the experimental testing was conducted for verifying the design and simulation results of the transducer.

Abstract: Microelectronic substrates like silicon, alumina and LTCC (Low Temperature Cofired Ceramics) allow for high robustness and reliability, 3D packaging (electrical connection, channels, cavities and membranes) as well as integration and application of electronic components whereas piezoceramic materials offer sensor and actuator operations. To combine the advantages of both, integrated solutions are of great interest. This paper deals with two approaches of monolithic integration, (i) screen printing of piezoceramic thick films on microelectronic substrates and subsequent post firing and (ii) integration of pre-fired piezoceramic components into green LTCC multilayer packages and subsequent sintering. Functionality of smart microsystems not only depends on the outer design and construction but to a great part on interaction of substrate and piezoceramic material properties. A thorough choice of materials as well as the understanding and prevention of chemical reactions are necessary to build effective systems.

Abstract: In this paper, an ultrasonic transducer is designed and optimized in order to reduce the error of resonance frequency and maximize the amplitude of the radiating tip. In order to get the basic dimensions of an ultrasonic transducer easily, resonance frequency equations are derived by using the traditional analytic method. Using ANSYS FEM software, we analyzed the vibration model of the transducer, including Modal Analysis and Harmonic Response Analysis. Studied how the length of two resonance rods affects the resonance frequency. By optimizing the dimensions of the ultrasonic transducer, the error of resonance frequency is reduced to 0.03%; the amplitude of the vibrating tip is up to 6.20μm. The optimal results show that the transducer designed in this paper has superior performance parameters and meets the requirements of machining.