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The demand for LCD (liquid crystal display) screens will maintain a rapid growth in the next decade. The high-speed edge-grinding process is important in this industry. One issue is the subsurface damage (SSD) induced by the edge-grinding. Glass is very sensitive to the micro-cracks of the processed surface. To investigate the SSD generated by the edge-grinding process, two grinding wheels with different grit sizes and bonding materials were employed to shape the edges of ultra-thin normal-glass panels and LCD-glass panels with 12 sets of grinding conditions. The cross-sectional microscopy, as a simple and direct assessment method, was utilized to measure the depths of subsurface cracks. It was found that bonding material, diamond concentration, and grit size imposed influences on the material removal mechanism of the edge-grinding process. The edge-grinding conducted using a wheel with grit size = 22-36 μm, diamond concentration = 100, and bonding material = resin induced little damage to the glass samples. With the smooth edge ground, the majority of the material was removed by plastic deformation. However, the subsurface damage of the LCD glass was smaller than that of the normal glass induced under the same grinding condition, and the LCD showed better machinability. The density of SSD of the LCD glass was also less than that of the normal glass. [ABSTRACT FROM AUTHOR]

Fixed abrasive polishing has some advantages in generating good planarization surfaces with low defects. The surfaces after polishing have better uniformity, and the material removal rate is much higher than that of the traditional chemical mechanical polishing using loose abrasives. One of the most important factors that have significant effects on the uniformity of the polished surface is the pad wear profile. The pad wear profile after a long time of polishing is almost concave, and it has been challenging to create a flat surface. Therefore, there is a requirement for creating a better pad wear profile to improve quality of machined surfaces in chemical-mechanical polishing processes. In this paper, kinematic aspects of the effects of operation parameters on the pad wear profile are investigated, combining with conditioner sizes, pattern, and positions. Based on that, a new model, including new designs of the conditioner and pad, is proposed. This new model has created a convex pad wear profile instead of a concave one. According to the result of the new model, the pad shape after the conditioning process is more uniform than the old one conditioned by the old model. The result was validated by an algorithm which was validated by the experiments reported in our previous paper. [ABSTRACT FROM AUTHOR]

In the grinding of thin-walled and honeycomb-structured components made up of Hastelloy, undesired burrs are often created. The formed burrs negatively affect the quality of the products. Subsequent deburring increases overall manufacturing process time and cost. This work was focused on development of high-speed grinding process and grinding strategies to reduce burr size and improve ground surface quality. An electroplated Cubic Boron Nitride (CBN) wheel with miniature concave and convex asperities on its circumferential working surface was developed. Grinding performance with the designed CBN wheel was compared with a normal CBN wheel without surface asperities. Special fixtures with the function of adjusting honeycomb orientation (change of grinding direction) were purposely designed and fabricated. Design of experiment (DOE) was adopted for optimization of grinding parameters. It was found that less burr (even burr-free) grinding was achieved with the utilization of the specially designed CBN wheel with concave and convex asperities under optimal grinding conditions investigated, i.e., rotational speed of 5,000 RPM, depth of cut of 25 μm, and feed rate of 7,500 mm/min. [ABSTRACT FROM AUTHOR]

Fixed abrasive chemical-mechanical polishing (CMP) is an efficient surface finishing method. The non-uniformity of substrates after polishing is one of the most interesting things in current trends in research. One of the reasons for the non-uniformity is pad wear. The pad in this polishing process has abrasive grains embedded on the surface. Researching on the pad wear will help improve the pad conditioning process to get a better pad surface. Some studies have used kinematic motion to show the correlation between the cutting path density and the pad wear. However, the effect of contact time between the conditioner's grains and the pad surface on the pad wear non-uniformity has not been integrated yet. In this research, an analytical model was established by combining of the kinematic motions and the contact time to investigate the pad wear non-uniformity. The results indicated that the cutting path density and the contact time near the pad center are more than that near the pad edge. They could be the main reasons of the non-uniformity of the pad wear. The model results showed a good agreement with experiments. [ABSTRACT FROM AUTHOR]

Glass disk substrates are used in a wide range of portable devices because of their relatively high resistance to heat and shocks compared to aluminum substrates. Chemical mechanical polishing (CMP) with fixed abrasive pad is an alternative glass disk substrates finishing method to loose abrasive lapping and polishing with traditional pad. In this paper, we developed a chemical mechanical polishing process for 2.5-inch glass disk substrates using a fixed abrasive pad. A serial of CMP experiments were carried out under different polishing variables and conditioning modes (ex situ and in situ conditioning). The polishing performances were evaluated and analyzed in terms of surface roughness, surface topography, and material removal rate. The polishing characteristics were also discussed to reveal material removal mechanism and surface generation involved in fixed abrasive CMP for glass disk substrates. [ABSTRACT FROM AUTHOR]

Chemical mechanical polishing (CMP) experiments are performed to study the effects of four key process factors on the flatness and surface finish of the polished optical silicon substrates and on the material removal rate (MRR). The experimental results and analyses reveal that the pad rotational speed and polish pressure have significant effects on the MRR, the interaction of the polish head rotational speed and slurry supply velocity and the interaction of the polish pressure and polish head rotational speed have significant effects on the flatness, and the pad rotational speed has a significant effect on the surface roughness R of the optical silicon substrates polished. The optimal combination of the four factors investigated is a polish pressure of 9,800 Pa, a pad rotational speed of 20 rpm, a polish head rotational speed of 20 rpm, and a slurry supply velocity of 100 ml/min. A confirmation CMP experiment has been carried out using the optimal process parameter setting obtained from the design of experiments analyses. The goal to attain optical silicon substrates with nanometric surface roughness and micrometric flatness by an optimized CMP process with a high MRR simultaneously so as to reduce the polishing time to only 15 min from over 8 h has been achieved. [ABSTRACT FROM AUTHOR]

This article discusses the recent developments in grinding of advanced materials. Eighty-four journal papers published recently are briefly introduced. The topics are advances in grinding of brittle materials, grinding of silicon, dressing/truing of grinding wheels, grinding fluids, grinding of mirrors and vibration-assisted grinding, measuring/monitoring of grinding, optimization of grinding, modelling and simulation of grinding, and size effect. Ductile mode grinding of brittle materials has been and will continue to be an intensive research area because of its increasing industrial applications and academic demands for fundamental understanding of the ductile mode grinding mechanism. Highly precision manufacturing of silicon substrates faces more and more new challenges. Grinding of silicon continues to be a popular research topic. Using lasers to true and dress grinding wheels has attracted great research interest, because it has significant advantages over mechanical processes. Environmentally friendly grinding fluids are increasingly highly demanded. Vibration-assisted grinding is promising. Monitoring, modelling and optimization of grinding processes help to understand grinding mechanisms and achieve better grinding performance. The size effect is more prominent in grinding than turning and can be used for obtaining a controlled work-hardening surface layer with higher wear resistance and hardness. [ABSTRACT FROM AUTHOR]

Thermally sprayed WC-Co coatings on steel rods were machined by grinding and turning using diamond tools, and thermally sprayed Inconel 625 coatings on steel rods were machined by turning using various WC tools. Four of these samples were selected for surface characterization using a stylus roughness tester. The results show that precision-machined WC-Co and Inconel-625 surfaces can be identified as self-affine fractals in the stochastic sense within the correlation length. The root-mean-square roughness ( R q ) depends on the scale of cut-off length (=sampling length in this paper) as a power law. The R q of the machined WC-Co surface was found to be dependent on the scale of cut-off length rather than the scale of evaluation length. The roughness exponent is a very useful parameter and can be used to predict the roughness value of the surfaces at any scale length, if the scale is within the correlation length and provided that one such value of a scale is known. It may be suitable to compare surfaces using roughness exponents, even if different cut-off lengths or scanning scales are used in the measurements to obtain roughness exponents. [ABSTRACT FROM AUTHOR]

Slurry plays an important role in the material removal of chemical mechanical polishing (CMP). However, the behavior of abrasive particles of the slurry in the interface between the wafer and the pad during CMP is not fully understood. In this paper, a new computational fluid dynamic (CFD) model was developed. It was a combination of multiphase and discrete phase modeling. The abrasive particles behavior and the slurry distribution in the interface were simulated using this model. The total numbers of particles in the gap were quantified to characterize their mechanical effects under different operating parameters. The simulation results showed that when the gap thickness increased and speeds of the wafer and the pad decreased, the total number of particles in the gap increased. It also found that the particles were non-uniformly distributed below the wafer. The results have the capacity of providing a deeper insight understanding of the material removal of the CMP mechanism. [ABSTRACT FROM AUTHOR]