电容式微加工超声传感器的有限元分析及其薄膜的形变研究
发布时间：2019-05-13 08:13
【摘要】：超声技术在医疗成像和无损探伤等领域具有广泛应用,而作为各种超声应用的核心器件,超声传感器一直是研究的热点。其中,电容式微加工超声传感器(CMUT)克服了传统压电超声传感器阻抗失配的缺陷,同时还具有高带宽、高灵敏度和易集成等优点,因此具有极大的应用前景和研究价值。振动薄膜是CMUT的核心结构。通过薄膜的形变分布,既可以计算传感器的电容变化量,又可以分析传感器的稳定性,因此薄膜的形变量是传感器设计过程中需要考虑的一个重要因素。本文主要对CMUT的振动薄膜(矩形薄膜和椭圆薄膜)在静电力作用下的形变量进行了研究。首先,本文根据CMUT的结构特点,利用有限元分析软件ANSYS 15.0建立了CMUT的三维简化有限元模型,以CMUT的四分之一作为模型来分析整个传感器,提高了运算效率。对结构进行了静力分析,并且以塌陷电压为指标,验证了所建立的有限元模型及分析方法的有效性。为了更接近真实情况,本文还对模型进行了改善,考虑了顶部电极对薄膜形变的影响,并且对改进后的模型进行了模态分析,研究了结构的固有振动频率。其次,本文利用有限元分析的结果研究了直流偏压和薄膜尺寸对薄膜形变影响的规律,选取和提出了能大致描绘薄膜形变曲线的基础函数。在此基础上,本文首次分别提出了CMUT矩形薄膜和椭圆薄膜在静电力作用下的形变数学模型,并为模型提出了用来分析薄膜尺寸影响的二维函数。最后,本文利用新的形变数学模型,通过数值积分的方法计算了CMUT在薄膜发生形变后的电容值,并描绘了薄膜中心面的变形曲面,分析了模型对CMUT薄膜设计的指导意义。另外,本文在薄膜小形变和大形变的两种情况下,分别从薄膜形变曲线的吻合度和传感器电容值计算的精确度两个方面,验证了形变模型的准确性。特别地,随机抽取一批不同规格的薄膜,通过与有限元法计算的电容值进行比较,得到矩形薄膜形变模型计算的最大误差为0.436%,而椭圆薄膜形变模型计算的最大误差为2.920%。
[Abstract]:Ultrasonic technology is widely used in medical imaging and nondestructive testing. As the core device of various ultrasonic applications, ultrasonic sensor has always been the focus of research. Among them, capacitive micromachined ultrasonic sensor (CMUT) overcomes the defect of impedance mismatch of traditional piezoelectric ultrasonic sensor, and also has the advantages of high bandwidth, high sensitivity and easy integration, so it has great application prospect and research value. Vibrating thin film is the core structure of CMUT. Through the deformation distribution of the thin film, not only the capacitance change of the sensor can be calculated, but also the stability of the sensor can be analyzed. Therefore, the shape variable of the thin film is an important factor to be considered in the design process of the sensor. In this paper, the deformation of vibratory thin film (rectangular film and elliptical film) of CMUT under electrostatic force has been studied. Firstly, according to the structural characteristics of CMUT, the three-dimensional simplified finite element model of CMUT is established by using the finite element analysis software ANSYS 15.0, and the 1/4 of CMUT is used as the model to analyze the whole sensor, which improves the operation efficiency. The static analysis of the structure is carried out, and the validity of the established finite element model and analysis method is verified by taking the collapse voltage as the index. In order to get closer to the real situation, the model is improved, the influence of the top electrode on the film deformation is considered, and the modal analysis of the improved model is carried out, and the natural vibration frequency of the structure is studied. Secondly, the effects of DC bias and film size on the deformation of thin films are studied by using the results of finite element analysis, and the basic functions which can roughly describe the deformation curves of thin films are selected and put forward. On this basis, the deformation mathematical models of CMUT rectangular thin films and elliptical thin films under electrostatic force are proposed for the first time, and a two-dimensional function for analyzing the influence of thin film size is proposed for the model. Finally, by using the new deformation mathematical model, the capacitance of CMUT after thin film deformation is calculated by numerical integration method, and the deformation surface of the central surface of the film is described, and the guiding significance of the model to the design of CMUT thin film is analyzed. In addition, in the case of small deformation and large deformation of thin films, the accuracy of the deformation model is verified from two aspects: the coincidence of thin film deformation curves and the accuracy of sensor capacitance calculation, respectively. In particular, a batch of thin films of different specifications are randomly selected and compared with the capacitance values calculated by the finite element method. The maximum error of the rectangular thin film deformation model is 0.436%. The maximum error of elliptical thin film deformation model is 2.920%.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2;TP212
[Abstract]:Ultrasonic technology is widely used in medical imaging and nondestructive testing. As the core device of various ultrasonic applications, ultrasonic sensor has always been the focus of research. Among them, capacitive micromachined ultrasonic sensor (CMUT) overcomes the defect of impedance mismatch of traditional piezoelectric ultrasonic sensor, and also has the advantages of high bandwidth, high sensitivity and easy integration, so it has great application prospect and research value. Vibrating thin film is the core structure of CMUT. Through the deformation distribution of the thin film, not only the capacitance change of the sensor can be calculated, but also the stability of the sensor can be analyzed. Therefore, the shape variable of the thin film is an important factor to be considered in the design process of the sensor. In this paper, the deformation of vibratory thin film (rectangular film and elliptical film) of CMUT under electrostatic force has been studied. Firstly, according to the structural characteristics of CMUT, the three-dimensional simplified finite element model of CMUT is established by using the finite element analysis software ANSYS 15.0, and the 1/4 of CMUT is used as the model to analyze the whole sensor, which improves the operation efficiency. The static analysis of the structure is carried out, and the validity of the established finite element model and analysis method is verified by taking the collapse voltage as the index. In order to get closer to the real situation, the model is improved, the influence of the top electrode on the film deformation is considered, and the modal analysis of the improved model is carried out, and the natural vibration frequency of the structure is studied. Secondly, the effects of DC bias and film size on the deformation of thin films are studied by using the results of finite element analysis, and the basic functions which can roughly describe the deformation curves of thin films are selected and put forward. On this basis, the deformation mathematical models of CMUT rectangular thin films and elliptical thin films under electrostatic force are proposed for the first time, and a two-dimensional function for analyzing the influence of thin film size is proposed for the model. Finally, by using the new deformation mathematical model, the capacitance of CMUT after thin film deformation is calculated by numerical integration method, and the deformation surface of the central surface of the film is described, and the guiding significance of the model to the design of CMUT thin film is analyzed. In addition, in the case of small deformation and large deformation of thin films, the accuracy of the deformation model is verified from two aspects: the coincidence of thin film deformation curves and the accuracy of sensor capacitance calculation, respectively. In particular, a batch of thin films of different specifications are randomly selected and compared with the capacitance values calculated by the finite element method. The maximum error of the rectangular thin film deformation model is 0.436%. The maximum error of elliptical thin film deformation model is 2.920%.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.2;TP212
【参考文献】
相关期刊论文 前3条
1 张慧;宋光德;靳世久;官志坚;刘娟;;电容式微超声传感器的电极参数优化设计[J];传感技术学报;2010年07期
2 谷雨;;MEMS技术现状与发展前景[J];电子工业专用设备;2013年08期
3 徐s，
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