• Tribology and Lubricants
• /
• v.34 no.3
• /
• pp.115-122
• /
• 2018

Chemical mechanical polishing (CMP) is a hybrid processing method in which the surface of a wafer is planarized by chemical and mechanical material removal. Since mechanical material removal in CMP is caused by the rolling or sliding of abrasive particles, interfacial friction during processing greatly influences the CMP results. In this paper, the trend of tribology research on CMP process is discussed. First, various friction force monitoring methods are introduced, and three elements in the CMP tribo-system are defined based on the material removal mechanism of the CMP process. Tribological studies on the CMP process include studies of interfacial friction due to changes in consumables such as slurry and polishing pad, modeling of material removal rate using contact mechanics, and stick-slip friction and scratches. The real area of contact (RCA) between the polishing pad and wafer also has a significant influence on the polishing result in the CMP process, and many researchers have studied RCA control and prediction. Despite the fact that the CMP process is a hybrid process using chemical reactions and mechanical material removal, tribological studies to date have yet to clarify the effects of chemical reactions on interfacial friction. In addition, it is necessary to clarify the relationship between the interface friction phenomenon and physical surface defects in CMP, and the cause of their occurrence.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.28 no.3
• /
• pp.222-229
• /
• 2004

In this paper, the torque of CNC spindle motor during machining is estimated without speed measuring sensor. The CNC spindle system is divided into two parts, the induction spindle motor part and mechanical part. In mechanical part, the variation of the frictional force due to the increment of the cutting torque and the effect of damping coefficient is investigated. Damping coefficient is found to be a function of spindle speed and not influenced by the weight of the load, while frictional force is a function of both the cutting torque and spindle speed. Experimental equations are drawn for damping coefficient and Coulomb friction as a function of spindle speed. Incremental frictional torque Is also obtained as a function of both cutting torque and spindle speed. Graphical programming is used to implement the suggested algorithm to monitor the torque of an induction motor in real time. Torque of the spindle induction motor is estimated well in about average 3% error range under various cutting conditions.

• Tribology and Lubricants
• /
• v.27 no.6
• /
• pp.293-301
• /
• 2011

Understanding of the tribological characteristics of polytetrafluoroethylen (PTFE) and ultra-high-molecular-weight polyethylene (UHMWPE) is crucial for their applications such as bearing and total joint replacement. In this work, the effect of the surface roughness of carbon steel on the tribological behaviors of PTFE and UHMWPE was experimentally investigated by using block-on-ring tribotester with friction force monitoring capability. It was found that that the amount of material transfer layers of PTFE formed on the carbon steel was significantly larger than those of UHMWPE, which was responsible the lower friction coefficient of PTFE. It was also concluded that the effect of surface roughness of carbon steel on the friction coefficient of UHMWPE was more significant than that of PTFE. For UHMWPE, it was found that the effect of surface roughness of counterface was varied with respect to applied normal force and sliding as well. Based on Archard's wear law, the wear coefficient of PTFE and UHMWPE was calculated to be $3{\times}10^{-5}$ ~ $8{\times}10^{-5}$ and $7{\times}10^{-6}$ ~ $2{\times}10^{-5}$, respectively.

• Tribology and Lubricants
• /
• v.33 no.6
• /
• pp.282-287
• /
• 2017

SU-8 is an epoxy-type photoresist widely used for the fabrication of high-aspect-ratio (HAR) micro-structures in micro-electro-mechanical systems (MEMS). To fabricate highly integrated structures, chemical mechanical polishing (CMP) has emerged as the preferred manufacturing process for planarizing the MEMS structure. In SU-8 CMP, an oxidizer decomposes organic impurities and particles in the CMP slurry remove the chemically reacted surface of SU-8. To fabricate HAR microstructures using the CMP process, the adhesion between SU-8 and substrate material is important to avoid the delamination of the SU-8 film caused by the mechanical-dominant material removal characteristic. In this study, the friction force during the CMP process is measured with a CMP monitoring system to detect the delamination phenomenon and investigate the delamination of the SU-8 film from the silicon substrate under various pressure conditions. The increase in applied pressure causes an increase in the frictional force and wafer-edge stress concentration. The frictional force measurement shows that the friction force changes according to the delamination phenomenon of the SU-8 film, and that it is possible to monitor the delamination phenomenon during the SU-8 CMP process. The delamination at a high applied pressure is explained by the effect of stress distribution and pad deformation. Consequently, it is necessary to control the pressure of polishing, which can avoid the delamination in SU-8 CMP.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.5
• /
• pp.99-105
• /
• 2004

Internet provides the useful method to monitor the current states of the machine tool no matter where a personnel monitors it. In this paper, a monitoring method of the torque of the machine tool's spindle induction motor using interne is suggested. To estimate the torque accurately, spindle driving system of an CNC lathe is divide into two parts, induction motor part and mechanical part attached to the induction motor spindle. Magnetizing current is calculated from the measured 3 phase currents without speed sensor used to estimate the torque generated by an induction motor. In mechanical part of the system, some of the torque is used to overcome friction and remaining torque is used to overcome cutting force. An equation to estimate friction torque is drawn as a function of cutting torque and rotation speed. Graphical programming is used to implement the suggested algorithm. to monitor the torque of an induction motor in real time and to make the estimated torque monitored on client computers. Torque of the spindle induction motor is well monitored on the client computers in about 3% error range under various cutting conditions.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.1
• /
• pp.11-14
• /
• 2007

Consumables used in Chemical Mechanical Polishing (CMP) have been played important role to improve quality and productivity. Since the properties of consumables constantly change with various reasons, such as shelf time, manufactured time, lot to lot variation from supplier and so on, CMP results are not constant during the process. Also, CMP process results are affected by multiple sources from wafer, conditioner, pad and slurry. Therefore, multiple sensing systems are required to monitor CMP process variation. In this paper, the authors focus on development of monitoring system for CMP process which consist of force, temperature and displacement sensor to measure the signal from CMP process. With monitoring systems mentioned above, complex CMP phenomena can be investigated more clearly.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.12 no.2
• /
• pp.113-119
• /
• 2019

We have developed the multi-functioned friction measuring instrument for the previous research. In here, we improved the performance of friction measuring instrument by applying the adaptive smoothing method and analyzed the friction of plate and monitoring function of friction surface through scratch tests. We substituted lubricant steel plate to lubricant oil used for reducing the friction when fabricating steel plate because lubricant oil was regarded as one of the major causes for the environmental pollution. In particular, the functions of various plate such as galvannealed steel sheets were analyzed because friction coefficient could be changed depending on the type of organic/inorganic plate or state of coating layer. Therefore, we demonstrated that adaptive smoothing method could enhance the accuracy of measuring instrument which eliminate the noise. As a result of using the method, it showed the reduction rate 0.0417% for the friction coefficient 0.16.

• Smart Structures and Systems
• /
• v.31 no.6
• /
• pp.585-599
• /
• 2023

Field monitoring techniques offer an attractive approach for understanding bridge behavior under in-service loads. However, the investigations on bridge behavior under high-speed train load using field monitoring data are limited. The focus of this study is to explore the structural behavior of an in-service long-span steel truss arch bridge based on field monitoring data. First, the natural frequencies of the structure, as well as the train driving frequencies, are extracted. Then, the train-induced bearing displacement and structural strain are explored to identify the effects of train loads and bearings. Subsequently, a sensitivity analysis is performed for the impact factor of strain responses with respect to the train speed, train weight, and temperature to identify the fundamental issues affecting these responses. Additionally, a similar sensitivity analysis is conducted for the peak acceleration. The results indicate that the friction force in bearings provides residual deformations when two consecutive trains are in opposite directions. In addition, the impact factor and peak acceleration are primarily affected by train speed, particularly near train speeds that result in the resonance of the bridge response. The results can provide additional insight into the behavior of the long-span steel truss bridges under in-service high-speed train loads.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.7 no.6
• /
• pp.90-96
• /
• 1998

The ductile cast iron is austempered at 300, 350 and 40$0^{\circ}C$ temperature in order to investigate the basic factors for monitoring drill wear in automatic production process, and cutting force and AE RMS signals are measured with changing cutting condition for ADI(Austempered Ductile Cast Iron) with different mechanical properties. The signals of cutting force were influenced by cutting speed and feedrate greatly. On the other hand AE RMS signals are influenced by cutting speed where as it is not related with feedrate. As the depth of drilling increases, cutting force shows a slow increase and the value of AE RMS increases until the range of h/d=4. But over the range it increases greatly due to an amount of chip discharge and friction with inner wall of drilling hole, etc. As the drill diameter increases at a constant depth of drilling. Cutting force increases linearly, but the level of AE RMS does not increases linearly due to circumferential velocity and great influence of h/d.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.1964-1969
• /
• 2006

In order to solve the problem of the existing gate it developed the solar energy gate. The solar energy gate quotient a friction force from the area contact which will call improved with line contact and it diminished. Because of the result, The operation power of the gate came to be small and the small-sized of the motor was possible. From the small-sized of the motor, the solar energy system introduction was possible and the expense for the production establishment of the gate was diminished. From KRC in 2005 demonstration it establishes the solar energy gate in nationwide 50 places and characteristic the monitoring efficiently.