电容式微机械超声换能器封装设计

Design of Encapsulation on Capacitive Micromachined Ultrasonic Transducer

针对电容式微机械超声换能器(CMUT)封装材料阻抗匹配失衡,应力大及声波能量损失大等问题,设计了一种在水下10m透声性能好、弯曲形变小的聚氯乙烯封装结构。依据透声理论和材料属性,计算封装结构参数。利用COMSOL Multiphysics 5.0建立封装结构三维有限元模型,通过模态分析和静态分析分别得到封装结构的固有属性和水下机械性能。封装结构的一阶共振频率为792.47Hz,不会对CMUT 400kHz的工作频段产生干扰。利用压力平衡装置保护水下系统安全性,水下10m最大形变为1.12mm,最大应力为14.4 MPa,未超过聚氯乙烯的弯曲强度。实际测试声压与理论值最大误差为4.8%,物距测量误差为1mm,设计的CMUT封装结构满足设计要求。

Aiming at the problem of the imbalance of impedance matching,large stress and high acoustic energy loss in the current capacitive micromachined ultrasonic transducer（cMUT）encapsulation material,apolyvinyl chloride（PVC）material encapsulation structure with good acoustical transmission property underwater 10 m,small bending deformation is designed in this paper.The package structure parameters are calculated based on the theory of sound penetration and material properties.The three-dimensional finite element model of the encapsulation structure is established by using COMSOL Multiphysics 5.0.The inherent properties of the package structure and the underwater mechanical performance are obtained by the modal analysis and static analysis respectively.It shows that the first-order resonance frequency of the encapsulation structure is 792.47 kHz,which does not interfere with the working frequency of cMUT.The underwater system is protected by apressure equalization device.The maximum deformation underwater 10 mis 1.12 mm and the maximum stress is 14.4 MPa,which does not exceed the bending strength of PVC.The maximum error between the actual test sound pressure and the theoretical value is 4.8% and the distance measurement error is 1mm.Therefore,the designed encapsulation structure of cMUT can meet the requirements.