• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.560-565
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• 2001

Recently, machining process monitoring technique based on AE(acoustic emission) signal is used widely and becomes very important technique in machining process for improving the efficiency and the confidence of the systems. In this study, we fabricated a cheap acoustic emission sensor and monitoring system and estimated the properties of them through comparing with commercial AE sensor systems. In addition, we evaluated the performance of the fabricated sensor in polishing process. Futhermore, we are scheduled to develop the multi-point polishing process monitoring system through fabrication of the more AE sensors and complement of the monitoring system.

• Design & Manufacturing
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• v.13 no.3
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• pp.12-18
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• 2019

Fluid jet polishing is a method of jetting a fluid to polish a concave or free-form surface. However, the fluid jet method is difficult to form a stable polishing spot because of the lack of concentration. In order to solve this problem, MR fluid jet polishing system using an abrasive mixed with an MR fluid whose viscosity changes according to the intensity of a magnetic field is under study. MR fluid jet polishing is not easy to formulate for precise optimal conditions and material removal due to numerous fluid compositions and process conditions. Therefore, in this paper, quantitative data on the factors that have significant influence on the machining conditions are presented using various simulations and the correlation studies are conducted. In order to verify applicability of the fabricated MR fluid jet polishing system by nozzle diameter, the flow pattern and velocity distribution of MR fluid and polishing slurry of MR fluid jet polishing were analyzed by flow analysis and shear stress due to magnetic field changes was analyzed. The MR fluid of the MR fluid jet polishing and the flow pattern and velocity distribution of the polishing slurry were analyzed according to the nozzle diameter and the effects of nozzle diameter on the polishing effect were discussed. The analysis showed that the maximum shear stress was 0.45 mm at the diameter of 0.5 mm, 0.73 mm at 1.0 mm, and 1.24 mm at 1.5 mm. The cross-sectional shape is symmetrical and smooth W-shape is generated, which is consistent with typical fluid spray polishing result. Therefore, it was confirmed that the high-quality surface polishing process can be stably performed using the developed system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.22-28
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• 2020

This paper investigates the effects of retaining ring materials, particularly PPS and PEEK, used in the CMP process, on wafer polishing and ring wear. CMP can be performed using bonded type retaining rings made with PPS or injection molding type retaining rings made with PEEK. In this study, after polishing a wafer with a PPS retaining ring, the average profile height of the wafer was 0.098 ㎛ less than that of the wafer polished with a PEEK retaining ring, implying that PPS retaining rings achieve a higher polishing rate. In addition, the center area of the wafer profile had less deviation and improved flatness after polishing with the PPS ring. These results indicate that a higher polishing rate and smaller profile height deviation can be achieved using retaining rings made with PPS compared to retaining rings made with PEEK. Therefore, with semiconductor circuit patterns becoming finer and wafer sizes becoming larger, the use of PPS in CMP retaining rings can obtain more stable wafer polishing results compared to that of PEEK.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.625-631
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• 2002

In the previous study, a polishing robot system was developed to automate the polishing process and to cope with the shortage of skilled workers. This polishing robot system has several advantages: reduced time for setting polishing work, decreased labor costs, effective operation, continuous polishing work without an operator, improved machine accuracy, and the ability to polish a free curved surface die. However, still the problem remains that a worker must stay to monitor the polishing process in the poor working conditions for a long time. Nowadays some advanced manufacturing companies need to find a way to check the performance of their production equipments and plants from remote sites. Thus, this study constructed the communication network and developed the monitoring programs (a servo program and a client program) to operate the polishing robot from remote sites. Using these programs, workers are able to monitor and control the polishing robot on the web page, in any place where internet service is possible. To guarantee a stable operation in spite of a variable computer operating environment, the monitoring system is implemented in Java. The experimental results showed that the developed monitoring programs provided a stable communication.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.97-104
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• 2006

ELID(Electrolytic In-process Dressing) grinding is an excellent technique for mirror grinding of various advanced metallic or nonmetallic materials. A polishing process is also required for elimination of scratches present on ELID grinded surfaces. MAP(Magnetic Assisted Polishing) has been used as polishing method due to its high polishing efficiency and to its resulting in a superior surface quality. This study is describing an effective fabrication method combining ELID and MAP of nano-precision mirror grinding for glass-lens molding mould. It also presents some techniques for achieving the nanometer roughness of the hard metals, such as WC-Co, which are extensively used in precision tooling material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.2
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• pp.26-32
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• 2010

This paper reports some experimental result in grinding and polishing of silicon cathodes used in semiconductor manufacturing process. Cup shape diamond core wheels were used in experiments and the radial and tangential grinding forces were measured with surface roughness. In polishing experiments, flat type and donut type wool polishing tools were tested. The experimental results indicate that the grinding forces are proportional to the material removal rates and the surface roughness are inversely proportional to the spindle speed. The surface roughness of polished Si decreases with polishing time and higher spindle speed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.7-12
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• 2012

Chemical mechanical polishing(CMP) technology is faced with the challenge of processing new electronic materials. This paper focuses on the balance between chemical and mechanical reactions in the CMP process that is required to cope with a variety of electronic materials. The material properties were classified into the following categories: easy to abrade(ETA), difficult to abrade(DTA), easy to react(ETR) and difficult to react(DTR). The chemical and mechanical balance for the representative ETA-ETR, DTA-ETR, ETA-DTR and DTA-DTR materials was considered for defect-free surfaces. This paper suggests the suitable polishing methods and examples for each electronic material.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.77-82
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• 2009

This paper reports a kinematic analysis and experimental results for the polishing process of G7 LCD glass. A kinematic analysis for the relative motion of the upper plate and lower plate has been done and computer simulation has been programmed. A series of polishing experiments has also been carried out and compared with analytical data. The experimental results agreed well with analytical ones. The experimental results indicate that the polishing removal is proportional to the relative speed and pressure.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.9
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• pp.438-443
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• 2001

In the shallow trench isolation(STI)-chemical mechanical polishing(CMP) process, the key issues are the optimized thickness control, within-wafer-non-uniformity, and the possible defects such as pad oxide damage and nitride residue. The defect like nitride residue and silicon (or pad oxide) damage after STI-CMP process were discussed to accomplish its optimum process condition. To understand its optimum process condition, overall STI related processes including reverse moat etch, trench etch, STI fill and STI-CMP were discussed. Consequently, we could conclude that law trench depth and high CMP thickness can cause nitride residue, and high trench depth and over-polishing can cause silicon damage.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.32-39
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• 2003

Pulse electrochemical machining process with high or low current density may produce a non-lustrous surface on workpiece surface. The usual polishing process to remove a black layer from the surface has been hand polish the part. But the milli-to-micro meter scale structure formed by the electrochemical machining process may be destroyed while polishing process. The application of ultra short voltage pulses based on the analysis of electrical double layer charging process allows high resolution electrochemical machining and polishing. This technique was based on the specific polarization resistance from the comparison of ideal and experimental potential variation during short voltage pulses.