Implementation of Silicon-on-Insulator (SOI) Control Electronics to Accelerometers for High Temperature Applications

Abstract

The requirement to install control systems integrated with sensors in high temperature environments has posed a challenge to the traditional limit of 125°C for conventional electronics. There is a need to operate at temperatures of 200°C and above in restricted space for example in down-well, aero-engine or geothermal applications in combination with high pressures, vibrations and potentially corrosive environments. Piezo-electric accelerometers based on ferro-electric ceramics have been used in a wide range of applications for measuring vibrations, fluid flow and turbulence and are capable of operating as a transducer alone at temperatures up to 250°C, which has made them attractive in sensing applications for down-well drilling and aero-engine health and usage monitoring. However, the electronics traditionally used to carry out the signal conditioning and processing (e.g. charge to voltage conversion, filtering) has been limited to a qualification limit of 125°C, which results in a reduced sensitivity of the transducer output as the signal conditioning and processing cannot be performed close to the sensor. With the development of Silicon-On-Insulator (SOI) semiconductor technology, which can operate at temperatures of up to 250°C, many of the signal conditioning and processing operations can be carried out in-situ with the accelerometers to create a new generation of high temperature products. In addition, the integration of many of the functions that used to require discrete components into one SOI based device has led to further miniaturisation opportunities and a protection against obsolescence of specialist analogue devices. This paper will describe the migration of the traditional low temperature electronics to a high temperature SOI based ASIC device and the implementation of high temperature electronics packaging technology to instrumentation for piezo-electric accelerometers, leading to products that are suitable for high temperature monitoring in restricted spaces in down-well drilling and aero-engine applications.