Key Engineering Materials Vols. 562-565

Abstract: To optimize the molding parameters investigating based on Finite Element Analysis is done for roll imprinting. The heat curable material PMMA is employed in the simulation, which is considered as an elastic perfectly-plastic material. Three factors are taken as the evaluation criterions, which are pattern transfer rate, maximum width ratio and maximum depth ratio. Several key parameters, such as the pattern size, the distance between mold and surface of PMMA, the duty cycle of the patterns, rotation velocity of the mold and Young’s modulus of the PMMA and pressing force, are analyzed systematically. Simulation show three of them are main influence factors on the imprinting quality, which are the distance between roller and surface of the polymer, the duty cycle of the patterns and the elastic modulus of the polymer. While the influence of pattern size and rotation speed can be ignored. The results indicate that the duty cycle should be greater than 2 and the distance between roller periphery and surface of the polymer should be -30um to ensure the fidelity of the pattern replication. The simulation results are significant for optimizing the parameters in the imprinting process.

Abstract: The paper developed a set of small split Hopkinson pressure/tensile bar testing system (SSHPB/SSHTB) to study the dynamic characteristics of the micro-electromechanical system (MEMS) material and components, by which the dynamic characteristics of MEMS nickel material and planar S-form micro-spring were got. The dynamic Youngs modulus of LIGA nickel under the strain rate of 2×10³s^-1 got by the SSHPB is about 250GPa, which is slightly higher than that under static condition. The deformation peculiarity of the planar S-form micro-spring is also got by the SSHTB, which is uneven due to the spreading of the stress wave in the micro-spring. The result of the paper is valuable for providing feasible directions to the optimization design and manufacture of the MEMS components.

Abstract: In order to get high tapered spatial complicated curved surface parts and solve the difficult problems of machining spatial curved surface parts in high-speed wire cut electronic discharge machining (WEDM), a turnover NC rotary table based on the mathematical models of spatial complicated curved surface was designed. Through establishing the mathematical equations of the general motion form, the several major processed forms are obtained. Then the multi-axis movement WEDM system and its experimental device were established. Through machining experiment of the several major processed forms, it shows that the multi-axis movement WEDM system has high machining quality and low cost and has practical applicability, to confirm the feasibility of the polar coordinates processing system in space ruled surface, and to produce a novel research direction for solving the difficult problems of machining spatial curved surface parts.

Abstract: UV radiation, oxygen plasma treatment and dynamical coating technique were the three main modification techniques to be widely applied in the surface modification of polymer materials. This paper presented the experiment results of PDMS surface modification with these three techniques. The contact angle was measured to test the modification effect, also the further verification testing of aging property after a long time storage were carried out. Of all the testing results, the dynamical coating technique, 10 layers 0.02% PDDA and PSS (V/V) alternatively adhesion on the PDMS surface, made the contact angle lowed to the 21°, and even after 15 days, it still kept as the 61°and exhibited the better hydrophilic character.

Abstract: Single phase pyrite has been successfully prepared via the reaction of FeSO₄·7H₂O, S and Na₂S·9H₂O using hydrothermal method. The X-ray powder diffraction measurements confirm the formation of iron disulfides in the pH range of 1-12. Marcasite is formed at pH<4, the marcasite contents in the final products increasing with decreasing pH; when the pH is higher than 4, the final product is single phase pyrite. Scanning electron microscope (SEM) images reveal that both the pH and temperatures have significant effects on the size and morphology of final products. Pyrite micro-nanocubes of 200-400nm in length were synthesized at pH=9. Detailed information of the experimental results are analyzed in the results and discussion part.

Abstract: Three dimensional integrated circuits (3D ICs) consisted of stacking and vertically interconnecting are an emerging technology with great potential for improving system performance. 3D integration relies on Through Silicon Via (TSV) interconnection and interlayer bonding between the silicon layers. Due to the advantages of higher device density, lesser signal delay, shorter interconnection length and smaller package size, this technology attracts growing attentions. A number of innovative processes contribute to the realization of 3D IC. These include back grinding, coating, cleaning, etching, wafer thinning, filling of high aspect ratio vias with electroplated copper and interlayer bonding, etc. In this work, finite element models for four-layer stacked TSV-based (Through Silicon Via) 3D IC are established based on the heat distribution of working process caused by heat source in device die, in order to investigate the thermal effects and determine the improvements required. The transient temperature fields of 3D IC structures are obtained. The effects of various geometric parameters and thermal properties on the overall temperature have been analyzed. The result indicates that TSV diameter, pitch, BCB thickness and BEOL conductivity play more important roles to the temperature increment and the maximum temperature of no TSV structures is several times of that of TSV-based structures. The copper provides for an effective heat conduction path, and reduces considerably the overall temperature. It is also shown that the heat path from chip to the bottom surface is the main way for the heat dissipation.

Abstract: Fast Ignition (FI) attracts much attention owing to its advantages. The fabrication of fast ignition targets is one of the key technologies in FI study. Based on the single point diamond turning (SPDT) technology, Diamond post-turning method is adopted in this paper for the fabrication of gold cone. It not only helps to reduce the end-effect of cone mandrel and consequently improve the coaxiality of internal and external cone surface, but also helps to improve the quality of cone surface and the wall thickness consistency. Besides, the processing parameter of diamond post-turning is experimentally studied in this paper for its effect on the cone surface roughness. According to results, the cone surface roughness is Ra 9.21nm, the wall thickness consistency is 3μm and the cone end surface roughness is Ra5.72nm。

Abstract: Mathematical model of the MEMS relay volume involves in mechanical, electrical, magnetic, thermal, etc., the MEMS relay optimization design is a constrained nonlinear function optimization problem. In this paper, aim at the disadvantages of standard Particle Swarm Optimization algorithm like being trapped easily into a local optimum, we improves the standard PSO and proposes a new algorithm to solve the overcomes of the standard PSO. The new algorithm keeps not only the fast convergence speed characteristic of PSO, but effectively improves the capability of global searching as well. Experiment results reveal that the proposed algorithm can find better solutions when compared to other heuristic methods and is a powerful optimization algorithm for MEMS relay optimization design.

Abstract: In the process of a physical procedure, more than one vibration signals should be measured, whose value and frequency are in a wide range. Therefore, in such a situation, a single sensor can hardly meet the testing requirement. To solve this kind of problems, a kind of aligned array MEMS bionic vector vibration sensor is proposed. This aligned array vibration sensor consists of four micro-structure sensors and the testing ranges are 10g, 100g, 500g, and 1000g. On the basis of the mathematical model, the array sensing unit was simulated by ANSYS. The test was presented at last. The experiment results show that both the two direction of the aligned array vibration sensor have high sensitivity, good linearity and good output stability. The sensitivity of the X direction is 2.6134mv/g and Y is 2.5563mv/g, the linearity of X direction is 0.99991and Y is 0.99968.

Abstract: Over the last decade, a relatively in-depth research on the different structures and types of the full SiC pressure sensors including the piezoresistive, the capacitive and the optical SiC pressure sensors etc. has been conducted with a view to realizing the pressure measurement in high temperature circumstances. The piezoresistive SiC pressure sensor has gradually become the focus of research due to its simple structure and convenience application. In our research, the piezoresistance strip is designed on the deep-etching sensitive circular diaphragm formed via deep etching. Firstly, the 6H-SiC strain coefficient GF value is compared on the radial direction and the transverse direction by analyzing the circular diaphragm deformation theory. It’s concluded that both in the radial direction, four resistance strips are assigned in the center of circular diaphragm and along the edge respectively, with equal number on these two locations. Better consistency and sensitivity are achieved by this solution. Secondly, the design size of the sensitive circular diaphragm and the pressure resistance strips are determined with the expected work temperature and the target measuring range being taken into consideration. The final layout scheme design of four pressure resistance strips is determined through simulation on the consideration of the thermal stress caused by the AlN packaging.