Jing-hua Yin

Design and analysis of a novel low actuation voltage capacitive RF MEMS switches

The novel design of capacitive RF MEMS switches using torsion spring is presented and analyzed in this paper. The RF MEMS switches not only have ordinary folded suspending beams, but also add torsion springs. The simulation results show that compared with ordinary bending deflection, the torsion deflection is sensibly influenced by the ratio of the arm width (b) and the arm thickness (t), so the actuation voltage (VT) of the RF MEMS capacitive switches which have both the ordinary bending deflection and added torsion deflection will be obviously depressed. At same time, the theory analysis shows that the lower VT can be obtained with longer torsion arm length (LD), longer driven arm length (LD).By optimizing the structure design of RF MEMS switches, when LT, LD, b and t are 180 um, 120 um, 5 um and 1 um, respectively, the area actuation electrodes is 120times120 um2, the actuation voltages of RF MEMS switches is 1.5 V by computer simulating.

Study of Thermo-Mechanical Stress Distribution for CBGA Package

In this paper, the two-dimensional model of the CBGA device is established to study its mechanics behavior under thermal cycling conditions by ANSYS. The results show that the position of the maximum stress located on the outmost solder balls of the device, where it would cause cracks easily and damage the device. The three-dimensional model (containing a single solder ball) of the CBGA device is also established to simulate the stress distribution of the device affected by the shape of solder ball. According to the simulation results, when the radius of solder ball is about 0.45 mm and height is about 0.65 mm, the Von Mises stress and total strain are smaller comparatively, in the condition of the spot pitch 1.27 mm, thus the reliability of solder ball and devices can be improved.

Anisotropic Properties of Ultra-Thin Freestanding Multi-Walled Carbon Nanotubes Film for Terahertz Polarizer Application

Anisotropic transmission of ultrathin freestanding multi-walled carbon nanotubes (MWCNTs) film has been investigated using terahertz (THz) time-domain spectroscopy. The super-aligned MWCNTs films were fabricated by a novel method-drawing and winding carbon nanotubes on square-shaped polytetrafluoroethylene (PTFE) frame. The MWCNTs film exhibited anisotropic transmittance of THz wave depending on the alignment direction of carbon nanotubes relative to the THz wave polarization orientation, which proved that such MWCNTs film acts as an ideal polarizer in the THz regime. The degree of polarization (DOP) of 99.4% and the extinction ratio (ER) of 25.3 dB (average value) has been demonstrated for a MWCNTs film of 9- μm thickness in a wide frequency range from 0.1 to 2.5 THz. Furthermore, the value of DOP and ER can be engineered expediently by controlling the film thickness. Our approach opens the possibility of MWCNTs film in application of THz optoelectronic devices.

Properties of carbon nanotubes loop antenna at Terahertz range

It is the first time this paper investigates the fundamental characteristics of the loop antenna formed single-walled carbon nanotubes from 1.0∼10 terahertz frequency region using finite integral methods. The armchair single-walled carbon nanotubes can be considered due to their metallic conducting. The surface current dense, electric field and magnetic field distribution, scattering coefficient, input admittance, radiation patterns and gain are presented and compared to carbon nanotubes dipole antenna with the same size of the perimeter of the loop antenna. The results demonstrate that carbon nanotubes loop antenna with a radius of 15 µm takes on the resonant frequency properties from 7.35 terahertz to 7.46 terahertz in the center frequency of 7.4 terahertz, corresponding scattering coefficient less than −10dB. The maximum gain of carbon nanotubes loop antenna is 5.7 dB. All results is can be used for the design of carbon nanotubes antenna in the terahertz region.

Time response and dynamic behavior of electrostatic driven RF MEMS capacitive switches for phase shifter applications

This paper analyzes the effects of the materials, the driven voltage, the switch height, the width of the CPW signal line and the quality factor on the switching time and the dynamic behavior of electrostatic driven RF MEMS capacitive switches for the microwave distributed MEMS shifters to reduce the switching time and the impact velocity, and increase the capacitive ratio

Wafer Level Micropackaging for Distributed MEMS Phase Shifters

A novel packaging structure which is performed using wafer level micropackaging on the thin silicon substrate as the distributed MEMS phase shifters wafer with vertical feedthrough is presented. The RF performances of proposed structure are investigated using Microwave Studio (CST). The results show that the insertion loss (S21) and return loss (S11) was -0.4-1.84 dB and under -10 dB at 1-50 GHz. respectively. And especially, the phase shifts of 360deg are obtained at 48 GHz. Tins indicate that the proposed packaging structure for the distributed MEMS phase shifters can provide the maximum amount of phase shift with the minimum amount of insertion loss and with return loss of less than -10 dB.

Influence of Wafer Level Packaging Modes on RF Performance of MEMS Phase Shifters

With RF MEMS technology rapid development, the distributed RF MEMS phase shifters have exhibited excellent RF performance, such as high isolation, high phase shifts, low insertion loss and wide bandwidth operation features at high frequency. However, the applications of RF MEMS phase shifter are hampered by the lack of production-worthy wafer level packaging. Therefore, the problems on packaging solved are very stringent. This paper mainly investigates on the influence of wafer level packaging modes on the RF performance of distributed RF MEMS phase shifters. The insertion loss S21, return loss S11 and phase shifts parameters are analyzed using 3D electromagnetic simulation tool - microwave studio (CST). Simulation results show that the insertion loss of the distributed RF MEMS phase shifters for bonding wafer packaging and wafer level micropackaging is -0.59dB and -0.061dB at l0GHz, -0.79dB and -0.25dB at 50 GHz, respectively. The return loss -11.8366dB and -26.66906dB at l0GHz, -14.50227dB and -32.30596dB at 50GHz, and the phase shift is 170.78deg and 161.82deg at 50GHz, respectively. Therefore, we concluded that different wafer level packaging modes distinctly affect the microwave performance of the distributed RF MEMS phase shifters. Comparing the RF performance parameters of two modes, the wafer level micropackaging mode shows excellent RF performance (the average insertion loss of -0.ldB and the average return loss of deg22 dB) and no resonances at 1-60 GHz, and adapted to the packaging of distributed RF MEMS phase shifters

Stress Distribution of Stacked Chip Package in Curing Process

In this paper, packaging process for a typical stacked three-chip packaging structure has been studied in detail by finite element analysis (FEA) method. The simulation shows that thermal stress may result in die crack and delamination before package has been finished. During the each curing process, the stresses of joints of die in the bottom layer are largest and the system reliability is not lowered over three layers die. The package would be destroyed most easily in cure II step. Failure rate of upper die is also high in the cure III, as the epoxy molding compound (EMC) can bring residual stress of phase changing, and combining FEA results, the package structure has been optimized

Numerical simulation and analysis of an electroactuated MEMS capacitive switch using finite element method

The MEMS capacitive switch based on fixed-fixed microbeam have garnered significant attention due to their geometric simplicity and broad applicability, and the accurate models should be developed to predict their electromechanical behaviors. The improved macromodel of the fixed-fixed microbeam of MEMS capacitive switch is presented in this paper, the numerical analysis of mechanical characterizations of the MEMS capacitive switches under electric actuation are performed by the finite element discretization method, and the performances of static and dynamic of MEMS capacitive switch are obtained. The numerical results show that, with only a few nodes used in the computation, the finite element discretization method gives the identical results to other numerical methods, such as the shooting method and experiments. Moreover, the proposed model can offer proper and convenient approach for numerical calculations, and promote design of MEMS devices.

Vibration investigation of clamped-clamped microbeam of MEMS capacitive switch under mechanical shock

A numerical analytical method based on multi-mode Galerkin discretization is presented to investigate the nonlinear response of the clamped-clamped microbeam of the MEMS capacitive switch under the different mechanical shock loads. The results show that using five or more modes can be sufficient to capture the nonlinear dynamic response of clamped-clamped microbeam, and the microbeam experiences a mechanical shock load as a quasi-static load or a dynamic load depending on the ration between the natural periods of the structure and the period or requency of the shock load. Moreover, the proposed method gives the identical results to other numerical methods in the literature, and is straightforward to implement and could save computation efforts while not losing accuracy.