Papers by Keyword: Polishing

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Authors: Akira Miyasaka, Jun Norimatsu, Keisuke Fukada, Yutaka Tajima, Yoshiaki Kageshima, Daisuke Muto, Michiya Odawara, Taichi Okano, Kenji Momose, Yuji Osawa, Hiroshi Osawa, Takayuki Sato
Abstract: The production of 150 mm-diameter SiC epitaxial wafers is the key to the spread of SiC power devices. We have developed production technology of the epitaxial growth for 4° off Carbon face (C-face) 4H-SiC epitaxial layers on 150 mm diameter substrates. Several growth parameters and hardware were optimized to obtain high uniformity wafers. We have succeeded in fabricating high quality C-face wafers with smooth surface and high uniformity.
Authors: Ai Isohashi, Yasuhisa Sano, Shun Sadakuni, Kazuto Yamauchi
Abstract: A novel abrasive-free polishing method called catalyst-referred etching (CARE) has been developed. CARE can be used to chemically planarize a silicon carbide (SiC) surface with an etching agent activated by a catalyst. Platinum (Pt) and hydrofluoric (HF) acid are used as the catalyst and etchant, respectively. CARE can produce an atomically flat and crystallographically highly ordered surface of 4HSiC (0001) with a root-mean-square roughness of less than 0.1 nm regardless of the cut-off angle. However, industrial use of CARE is difficult because of HF acid usage. In this study, pure water was investigated as an alternative etchant to HF acid. We examined CARE using pure water by applying it to the planarization of a 4HSiC substrate and observed a feasible performance. The removal mechanism is considered to be the dissociative adsorption of water molecules to the SiC bonds of the topmost Si atom, namely the hydrolysis of the back bond, and the catalysis of Pt is considered to enhance the reaction. CARE with pure water is expected to represent a breakthrough method for surface processing of SiC, and will be widely applied in industrial processes such as planarization after high temperature processing in device fabrication.
Authors: Liang Chi Zhang, E.C.S. Kiat, Alokesh Pramanik
Abstract: To produce lifelong, harmless hip joint prostheses, considerable cross-disciplinary studies have been carried out. The research includes adaptability and sustainability of artificial materials to human body, selection of materials, precision fabrication and efficient replacement operation. This paper provides a brief review of some of these key aspects with some details in abrasive polishing.
Authors: Ying Chien Tsai, Guang Miao Huang, Jun Hong Chen, Inn Chyn Her
Abstract: The surfaces of the microlenses at the conical end-faces of optical fibers require high quality to keep the best performance of laser beam delivery. The polishing parameters play an important role to get the best quality of the microlenses. Most of the past researches study on the polishing parameters of flat surfaces. In this study, the polishing area of the conical end-face of the optical fiber is varied during fabrication. The relation between removed volume and removed thickness is built to determine the material removal rate. An experiment is carried out and the results show that the first two spinning turns are much effective for polishing under the parameters of the experiment.
Authors: Yong Bo Wu, Li Jun Wang
Abstract: Chemical mechanical polishing (CMP) is often employed to obtain a super smooth work-surface of a silicon wafer. However, as a conventional CMP is a loose abrasive process, it is hard to achieve the high profile accuracy and lots of slurry must be supplied during CMP operations. As an alternate solution, a fixed abrasive CMP process can offer better geometrical accuracy and discharges less waste disposal. In this paper, in order to enhance the polishing efficiency and improve the work-surface quality, a novel ultrasonic assisted fixed abrasive CMP (UF-CMP) is proposed and the fundamental machining characteristics of the UF-CMP of a silicon wafer is investigated experimentally. The results show that with the ultrasonic assistance, the material removal rate (MRR) is increased, and the surface quality is improved.
Authors: Jun Zhao, Ji Zhao, Lei Zhang, Cheng Fan, Fei Fei Han
Abstract: Getting the real-time information of spatial data, height and length of weld bead is the key point during the process of grinding and polishing large-scale part. To tackle this problem, a robot visual system is completed by building the double CCD and the laser on the mobile robot. Combining the image search algorithm with the image preprocessing algorithm in time domain, the laser single pixel feature line is obtained. The positions of each point in feature line are optimized by curve fitting so that the right spatial data and dimension are obtained. The result shows the proposed method can provides the precise information of weld bead, and the accuracy of measurement is within 0.15mm, as steady as repeatability.
Authors: Shao Hui Yin, Zhi Qiang Xu, Jian Wu Yu, Ze Biao Wang
Abstract: The basic principles of ultrasonic transducer and ultrasonic elliptical vibration polishing are investigated. A new kind of single-incentive ultrasonic transducer is designed, and the finite element simulation is conducted, a polishing device is developed based on the ultrasonic elliptical vibration. The polishing experiment is adopted to polish a tungsten carbide mold with the diameter 5cm. The experimental result shows that the tungsten carbide mould surface roughness changes from the original 0.026μm to 0.017μm.
Authors: Shuh Yi Wang
Abstract: The feasibility of mirror surface polishing by using the ring shaped tool (abbreviated as the RST) is studied. This novel polishing process is expected to apply in the fabrication of precise mold and optics. In order to reduce the tool wear effect, the semi-spherical tool was replaced by the ring shaped tool. The experimental results show that the machining rate is not affected by the tool wear, That is, this new process provides excellent machining repeatability. On the other hand, the mirror surface with Ra 4.4nm was yielded in the lager area polishing.
Authors: Takeshi Tanaka
Abstract: In this study, we proposed ER fluid-aided polisher (ERAP) using one-sided, patterned electrodes. The characteristics of ER fluid and ER fluid containing abrasive grit were investigated. The polishing performances of ER fluid containing abrasive grit were verified using an ERAP. The following conclusions were obtained. Thick clusters formed between both electrodes with increased voltage. Abrasive grit was condensed on the thick clusters of ER fluid-particles that formed around the electrodes with further increases in voltage. The ER effect is a hardening of ER fluid under loading by an electric field. The ER effect of ER fluid containing abrasive grit decreased because the grit clusters bound weakly to each other. The ER effect decreased with a decrease of grit size. The surface roughness showed little change when a Shower curtain (a nylon cloth) was used for a pad. An electric field was generated around the cutting zone when a Toraysee (a washable lens cloth) was used as a pad. This leads to large efficiency and high precision in polishing. The surface roughness decreased with increased voltage up to 1.0kV/mm, because the abrasive grit was tightly fixed by the ER effect. A minimum surface roughness was attained at approximately 1.0 kV/mm when using WA and SD grits. The surface roughness increased due to a hardening of the ER fluid, causing deep scratching of the workpiece at 2.0kV/mm.
Authors: Zhuo Lin Li, Wing Bun Lee, Benny C.F. Cheung, L.T. Ho, Yue Gang Fu
Abstract: Reflecting lens is an important component of optical systems, such as high-resolution cameras, large space telescopes and meteorological satellites etc. Among the lens materials, Silicon Carbide (SiC) has attracted a lot of attention as an important optical material because of its excellent mechanical and physical properties. Apart from the form accuracy, the attainment of a consistently high optical quality in polishing SiC is still of a concern. There are advanced ultra-precision polishing machines that can correct geometrical errors and surface finish of the workpiece. These include surface roughness and waviness. However, the hardness of SiC material itself put an challenge for polishing process. In this paper, A computer controlled ultra-precision polishing (CCUP) method based on mechanical polishing is used to produce the SiC lens. Experiments are being designed on a 7-axis ultra precision polishing machine (Zeeko IRP200). As it is difficult to find out slurry which is harder than SiC so that the conventional polishing slurry is be used. It provides a nice consequence that it also efficient when the polish powder is softer than the machined materials. The tool pressure, polishing head speed and the feed rate are varied and optimized to obtain the best reflectivity of the lens being polished. A pilot experiment will be conducted for the corrective polishing for the form error of the optical surface made of SiC. The result from the study will provide an important means to optimize the process for machining SiC reflective lens using the CCUP process.
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