地震检波器用微加速度传感器低应力真空封装研究

Research on low stress vacuum packaging for MEMS accelerometers used in seismic geophones .Compared to conventional moving coil geophones, MEMS-based novel digital geophones have the advantages of wide frequency width, large dynamic range and high vector-fidelity, can meet the requirements of high resolution, high fidelity and high precision exploration. In China,we developed MEMS accelerometers used in seismic geophones first. In order to reduce noise and increase dynamic range, vacuum packaging of MEMS accelerometers must be conducted, but the stress induced by vacuum packaging has much effect on the sensor’s stability and thermal coefficient. In the project, all silicon sandwich structure capacitive accelerometer we developed as the prototype, the structure deformation in the die caused by different solder, attach position and packaging conditions are analyzed by FEM and establishing the whole physical model of sensor die,solder and ceramic shell. It is explored that the effect of packaging stress on the CV performance of sensing capacitors,output offset stability and thermal coefficient by vacuum packaging test and sensor measurement, the effect mechanism of packaging stress on the performance of the sensor is revealed and low stress vacuum packaging method is presented. The research will breakthrough the key base technology of low stress vacuum packaging of MEMS accelerometers used in seismic geophones for oil exploration, and provide strong technical base for the sensor applied in a new generation of oil exploration equipment.

以高性能微加速度传感器为核心的数字检波器与传统动圈检波器相比，具有频带宽、动态范围大、矢量保真度高等优点，可以满足石油勘探界提出的高分辨率、高保真、高精度勘探的需求。国内我们率先研制出了地震勘探微加速度传感器，为了降低噪声、提高动态范围，传感器必须进行真空封装，但是封装应力对传感器稳定性和温度系数影响很大，制约着应用。本项目首先建立传感器敏感芯片、金属焊料和封装结构的一体化模型，通过有限元模拟，研究不同类型焊料、芯片粘贴位置、封装工艺条件等引入的封装应力对敏感芯片结构变形的影响。并结合真空封装试验和传感器性能测试比对，探索封装应力对传感器敏感电容CV特性、输出零位稳定性和温度系数的影响效应，揭示封装应力对传感器性能的影响机理，提出传感器低应力真空封装方法。项目的开展将突破地震勘探检波器用微加速度传感器低应力真空封装方面的关键基础技术，为其在新一代石油勘探装备中的应用打下深厚的技术基础。

以高性能微加速度传感器为核心的数字检波器与传统动圈检波器相比，具有频带宽、动态范围大、矢量保真度高等优点，可以满足石油勘探界提出的高分辨率、高保真、高精度勘探的需求。为了降低噪声、提高动态范围，传感器必须进行真空封装，但是封装应力对传感器性能影响很大，制约着应用。本项目建立了传感器敏感芯片、金属焊料和封装结构的一体化模型，找到了传感器低应力真空封装方法。通过测试CV特性，建立了封装应力引起的传感器中间敏感质量块偏移和扭转的分析模型，测试分析结果表明封装后传感器的中间敏感质量块扭转角在10-4 度量级，中心点偏移在10-7m量级，这对传感器的二阶非线性影响较大。采用重力场翻滚四点测试法，搭建了传感器非线性测试补偿系统，经电容阵列补偿后可将二阶非线性由10-2量级补偿至10-4量级，达到了应用要求，与国外COLIBRYS公司产品的性能相当。研制的加速度传感器模块零偏稳定性小于0.1mg，温度系数小于0.1 mg/℃，性能稳定可靠，已提供给国内高端行业用户单位应用50套。项目的开展解决了地震勘探检波器用微加速度传感器低应力真空封装的关键基础问题，为其在新一代石油勘探装备中的应用打下深厚的技术基础。