• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.8-13
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• 2000

Die polishing technology is very critical to determine quality and performance of the final products. Die polishing processes have not been automated because the automation requires a great deal of experience and skill of experts. Thus, to implement a fully automated polishing process, the development of polishing status monitoring system replacing the skill of experts is critical. AE is known to be closely related to material removal rate(MRR). As the surface is rougher, MRR gets larger and AE increased. The surface roughness can be indirectly estimated using the AE signal measured during automatic die polishing process. In this study, The polishing state monitoring system using AEms signal was developed. This system can be not only to monitor the abnormal state but also to estimate a state of surface roughness of polishing surface qualitatively.

• Journal of Biosystems Engineering
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• v.24 no.4
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• pp.309-316
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• 1999

This study was conducted to develop a large-scale rice polisher with double polishing stages for producing clean rice with high quality in rice processing complexs. The performance of the developed rice polisher was evaluated and improved. The results obtained from this study were as followings : 1. A large-scale rice polisher with double polishing stages was developed, which consisted of two polishing chambers(polishing part I and II), two spraying parts, a feeding part, power of 37kW, control panel, etc. Especially, the purpose of polishing part Iwere to uniformly mix white rice sprayed with water and to remove bran particles from the rice. the roller surface of the polishing part I was coated with chromium. 2. The capacity of the developed rice polisher was 4t/h. The broken rice rate of the polisher was less than 0.2%, compared with about 1% of others. 3. The whiteness increment of the developed polisher was 2.6~3.0% compared with about 2.3~2.5% of others. 4. The energy consumption of the developed polisher was 0.5kWh/100kg. 5. The developed polisher was improved with the angle change of screen slot of the polishing chamber I. The broken rice rate was reduced from about 0.5% to about 0.2% as the max. internal pressure of the polishing chamber II decreased by 0.4kg/$\textrm{cm}^2$ due to the increase of resistance in the polishing chamber I. The whiteness of the polisher showed more than 38~39. 6. The developed rice polisher showed high performance, compared with other domestic and foreign polishers.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.464-467
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• 2005

Among several polishing techniques for micro structures, polishing process using magnetorheological(MR) fluid has advantages in the finishing process of 3-D micro structures because abrasives in the fluid can reach surfaces with complex feature and play their role. Although many researchers have been trying to reveal its polishing mechanism of the MR polishing, it has not been successful because in-situ measurement of state variables is difficult and process parameters are complex. In fact, one of the key factors for applying process control methodologies, such as Run-to-Run control, is the measuring and monitoring of slurry quality because the process strongly depends on the fluid property. Therefore, it is necessary to maintain consistent slurry quality to guarantee the process repeatability. The proposed equipment achieves the longer life cycle of MR fluid and reduces the variability of products. A new method to measure the material removal rate in MRF polishing process is also proposed and discussed.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.2 no.1
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• pp.15-21
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• 2003

The ultrasonic polishing machine was developed to get super finishing that consist of machine part that can rotate and travel the main shaft with power 1.5kW, ultrasonic generator with frequency 20kHz. By using this machine we were investigated the characteristics of ultrasonic polishing for three different ceramics, and so could be obtained following results. First, we could be obtained the excellent surface for hard-ta-difficult cutting materials. Second, the effect of surface roughness for the feed rate could be shown that the more the feed rate Increases, the more the value of surface roughness increases. Third, owing to the characteristics being progressed brittle fracture in $Al_2O_3$ polishing with this machine, the value of surface roughness is larger than other ceramics. Forth, because the ultrasonic polishing can be smoother than the existing grinding in discharging the chips, it could be possible to improve the surface roughness about up to 15%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1308-1311
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• 2004

It is very important that get polishing characteristic that to be stable that accomplish planarization of high efficiency in chemical mechanical polishing, and there is repeatability Groove of pad causes much effects in flow of slurry among various factors that influence in polishing characteristic, is expected to cause change of lubrication state and polishing characteristic in contact between wafer and pad. Therefore, divided factors of pad groove by groove pattern, groove profile, groove dimensions. This research wishes to study effect that dimension of pad groove gets in polishing performance. When changed dimension (width, depth, pitch of groove) of groove, measured change of removal rate and friction force. According as groove dimension changes, could confirm that removal rate and friction force change. While result of this experiment studies effect of pad groove in CMP, it is expected to become small help.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.4
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• pp.303-307
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• 2007

This paper investigated the effect of the pad buffing process on the material removal characteristics and pad stabilization during silicon chemical mechanical polishing. The pads surface were controlled by the buffing process using a buffer made by the sandpaper. The buffing process is based on abrasive machining by using a high speed sandpaper. The controlled pad by the buffing process show less deformation deviation and stable material removal rate during the CMP process. In addition, the controlled pad ensure better uniformity of removal rate than comparative pads. As a result of monitoring, the controlled pad by the buffing process demonstrated constant and stable friction force signals from initial polishing stage. Therefore, the tufting process could control the pad surface to be uniform and improve the performance of the polishing pad.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.761-766
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• 2012

Abrasive fluid jet polishing processes have been used for the polishing of optical surfaces with complex shapes. However, unstable and unpredictable polishing spots can be generated due to the fundamental property of an abrasive fluid jet that it begins to lose its coherence as the jet exits a nozzle. To solve such problems, MR fluid jet polishing has been suggested using a mixture of abrasives and MR fluid whose flow properties can be readily changed according to imposed magnetic field intensity. The MR fluid jet can be stabilized by imposed magnetic fields, thus it can remain collimated and coherent before it impinges upon the workpiece surface. In this study, MR fluid jet polishing characteristics of fused silica glass were investigated according to injection time and magnetic field intensity variations. Material removal rates and 3D profiles of the generated polishing spots were investigated. From the results, it can be confirmed that the developed MR fluid polishing system can be applied for stable and predictable precise polishing of optical parts.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.2
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• pp.267-274
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• 2010

Recently, the magnetorheological (MR) polishing process has been examined as a new ultra-precision polishing technology for mirror surface generation in many applications, such as aspheric lenses, biochips, micro parts, etc. This method uses MR fluids which contains micro abrasives as a polishing media, and can. It is possible to obtain nano level surface roughness under suitable process conditions, however, required polishing time is highly dependent on the applied pre-polishing methods due to its very small material removal rate. Thus, in this study, a combined polishing method is presented to reduce total polishing time for SUS304. First, the electropolishing (EP) method was applied to obtain fine surface roughness, and the MR polishing was followed. Surface roughness variations were investigated according to the process conditions. As the results of this study, it was possible to reduce total polishing time for SUS304 using the proposed combined polishing method.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.1
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• pp.196-203
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• 2002

Generally, non-uniformity and removal rate are important factors on measurements of both wafer and die scale. In this study, we verify the effects of the pressure and relative velocity on the results of the chemical mechanical polishing and the effect of pattern density on inter layer dielectric chemical mechanical polishing of patterned wafer. We suggest an appropriate modeling equation, transformed from Preston\`s equations which was used in glass polishing, and simulate the removal rate of patterned wafer in chemical mechanical polishing. Results indicate that the pressure and relative velocity are dominant factors for the chemical mechanical polishing and pattern density effects on removal rate of pattern wafers in die scale. The modeling is well agreed to middle and low density structures of the die. Actually, the die used in Fab. was designed to have an appropriate density, therefore the modeling will be suitable for estimating the results of ILD CMP.