Papers by Author: Wu Zhou

Abstract: The attachment of the micromechanical silicon die to the substrate is one of the most critical steps in the packaging of highly accurate MEMS (microelectro-mechanical systems) accelerometer. The stress and strains, induced during die-attach process because of TCE (thermal coefficient of expansion) mismatches between different materials, will adversely affect the output characteristics of the accelerometer sensor. In this paper, three different materials: OE138, DG-3S and H70E are selected as the die-attach adhesives of a MEMS comb capacitive accelerometer. The stress and deformation of the silicon die, after the accelerometer model is cured from 80 °C to 20 °C, are evaluated with the aid of finite element analysis (FEA). As the results show, Young’s modulus and the thickness of the adhesives are the most significant factors influencing the stress and deformation of the silicon die. Soft adhesive material (OE138) have better stress absorption, and the stress and deformation of the silicon die decrease with the increasing thickness of the adhesive. Consequently, a soft and thick adhesive is recommended for the die-attach packaging of MEMS accelerometer.

Abstract: A universal capacitive readout integrated circuit MS3110 is used to measure capacitances in micro capacitance sensor. The configuration, operating principle and process of MS3110 are introduced and a method of programming the inner register on-chip with STM32 is presented with the control block diagram. Performance of MS3110 has been tested by the inner adjust capacitance. A comb micro accelerometer is designed and manufactured. A tentative equivalent electric model of accelerometer is built according to a series of capacitance tests, and the influence of parasitic capacitance in accelerometer system is discussed.

Abstract: Doping can lead to residual strain and change of elastic properties in silicon. Residual strain makes silicon wafer exhibit curvature, which are used for fabricate MEMS structure. The boron doping profile is not uniform through depth, which makes doped silicon become a inhomogeneous material or Functionally Graded Material. For boron-doped circular single crystal silicon wafer, a analytical method which based on functionally graded plate mechanics theory, is proposed to calculate its curvature. Example was used to verify the analytical method through 3D finite element simulation.

Abstract: An analytical method was presented to predict the three-dimensional (3-D) magnetic flux density distribution in the air gap produced by NdFeB permanent magnets of the planar motor. First, the analytical model of the planar motor was established, and Laplace equations of magnetic scalar potential and a series of boundary conditions were given. Then, the analytical expressions of magnet field strength and magnet flux density were obtained in the air gap of produced by NdFeB permanent magnets by the method of separation of variables. Finally, Comparisons the analytical results and finite element results, and the error never exceed five percent. Therefore, high precision has been derived. The analytical field results provide a basis for comparative studies, design optimization, and machine dynamic modelling of the planar motor.

Abstract: Parallel-plate capacitor whose plates both fixed to elastic supports is presented and analyzed in this paper, and its cantilevers model is analyzed to study the parameter dependence of pull-in voltage. The whole process of voltage calculation is based on material mechanics theories and analytical methods, and the results are verified by simulation of MEMS software, which is mainly aiming at the effects of plate dimensions on pull-in voltage. It is concluded that the longer are the supporting beams, the smaller are the effects of plate’s parameters on voltage, besides, the effect extent of longitudinal length of plate is little larger than that of transverse length.