Research On Key Technology Of LTCC Micromachined Differential Capacitance Accelerometer

Accelerometer is an essential device measuring the movement overload or vibration acceleration of its carrier. It is one of the most basic sensing elements of the navigation and guidance system, as well as the state of motion monitoring system. Accelerometer has found important applications in the field of aerospace, weapons, drilling equipment,high-end consumer and automotive electronics products. With the development of the miniaturization and high density integration of electronic devices, low temperature co-fired ceramic(LTCC) technology is becoming the mainstream technology for microelectronic and micro/nano multifunctional device packaging and assembly. This dissertation studies a capacitive micro-accelerometer embedded into LTCC packaging substrate. It can be regarded as a hybrid product of micro-inertial devices technology and SIP substrate technology.This dissertation mainly studies several key technologies of LTCC micro-accelerometer, including structure design, simulation analysis, process control and capacitance detection technique. In the structural design, numerical simulation tools are used to explore the factors affecting the sensitivity, nonlinear and dynamic/static response characteristics of the accelerometer based on analytical analysis. Post-sintering bonding technology in the LTCC process is developed to realize LTCC large cavity structure. High density multilayer wiring supported by LTCC microfabrication reduces the length of the interconnect line between sensing elements and the associated parasitic capacitance. The signal detecting circuit based on the integrated chip solves the problem of large noise, circuit complexity, and so on.A test platform is built to verify the characteristics of the Z-type accelerometer. The results show that the accuracy of accelerometer is better than 2mg, the range is ±10g,the accelerometer scale factor is 30.65mV/g, bias value 2.0065(g), second-order nonlinear coefficient 8.97E-4(2g g). Therefore, micromachining and MEMS technology based on LTCC is expected to be an important supplement of the mainstream Si-based technology, and even may replace it in some special applications. With the potential of micromachining, micro assembly and three dimensional integration accomplished in a single LTCC packaging line, micro device or components fabricated in such a way can be easily integrated with intelligent circuitry and communication functions, acting assensor nodes and serving variable applications ranging from manufacturing, aerospace to smart house and consumer electronics and etc.