Research On Thick-film Integrated Technology Of Digital Accelerometer

With the development of Aerospace and weapon equipment industry, new and rigorous requirements in the use of products have stimulated the development of accelerometer with high properties as small size, low power and high reliability, etc. Based on the research of design technique and key fabrication process of thick-film hybrid circuit, a tri-axial accelerometer with digital output is developed by the adoption of improved thick-film process and new materials. Its distinctive characteristic is, by the combination of micro-machining technology, hybrid integration and surface mounting technology, micro-silicon sensitive component, signal-conditioning circuit, micro-computer and standard interface are integrated on a ceramic substrate. In this way, high-density integration, output digitalization and volume miniaturization are realized. The reliability and anti over-load ability are greatly improved.In this paper, the present research situation of accelerometer is briefly introduced. According to the comparisons and analysis of the main integration technologies, thick-film hybrid integration technique is adopted to realize the accelerometer integration. Then a detailed introduction to the working principle of the micro-silicon accelerometer and the design of signal conditioning circuit, conversion circuit and interface are presented. Based on the structure of micro-silicon sensitive element and the connection of the Wheatstone bridge, the schematic diagram is completed. Being strict with technical criterion of the thick-film circuit and current process level, the layout design of hybrid circuit is designed consequently. Materials and technical process are determined according to the current technical level and former practice. Then a practical and effective fabrication process is mapped out. In the process of design and fabrication, factors influencing the performance of the integrated sensor are discussed in detail. Moreover, some key process is modified and optimized. At last, circuit sintering, component mounting, interconnect and packaging and primary test are performed. Test results shows the integrated sensor is stable and reliable, by which the design scheme and processing technology are proved to be valid and feasible.