Papers by Author: Jeng Haur Horng

Abstract: It is popular to wear the contact lens nowadays. Also, the output value of the contact lens is estimated more than 4 billion NT dollar every year. Because the phenomena of the contact lenses are very complicated, the relevant mechanisms are not well understood. Thus, the security of contact lens needs to be further investigated. In the lubricated mechanism of the contact lens, there is a layer of tear between the contact lens and cornea. The contact lens’ behavior is akin to that of a slider bearing. The lens represents the slider, the eye plays the role of the stationary pad, and the tear film is the lubricant. Hence, hydrodynamics and contact mechanisms of a contact lens are quite a fascinating subject that is relevant to the science of tribology. In the paper, the lubrication mechanisms include the partial hydrodynamic lubrication (contact lens roughness), contact mechanics and Newtonian fluid mechanics have been established. The parameters of roughness, flow factor, tear film geometry, and hydrodynamic pressure distribution are discussed. The developed technology increases the safety of contact lens.

Abstract: The novel method of using continuous variations of the electrical contact resistance and the friction coefficient for monitoring the tribological properties and the wear mechanisms of titanium pairs in air had been applied successfully by the authors. Therefore, this study further investigated the tribological properties and the wear mechanisms of self-mated titanium in pure water. In order to investigate the chemical reactions of titanium sliding against under water lubrication, the continuous variations of electrical contact resistance and friction coefficient were measured. SEM was used to observe the microstructures and of material transfer. The variations of electrical contact resistance were shown to produce clear and strong signals, superior to monitoring continuous friction coefficient variations for the self-mated titanium in pure water. According to the variations of electrical contact resistance, TiO2 was inferred to form at the interfaces of self-mated titanium in pure water. All of the experimental results demonstrated that the water lubrication has great potential for the research.

Abstract: The investigation of experiment becomes more important to increase the understanding of polishing performance. In this paper, a high precision polishing process test bench with in-situ measurement technology was applied to investigate the effects of operating parameters on polishing interfacial phenomena during mechanical polishing with IC1000 pad. The shear force and temperature rise were measured for stainless steel during mechanical polishing process. The surface temperature was measured by T-type thermocouples and the shear force was measured by a load transducer. The shear force for various particle size, applied load and rotation speeds during polishing process was demonstrated. Furthermore, the temperature rise under different slurry concentration was investigated. The experimental results contribute to the understanding of polishing mechanism and also provide an index to end-point-detection.

Abstract: The grain flow lubrication, based on Haff's grain flow theory and the Patir/Cheng flow factors method, is applied in the simulations of rough slider bearings and chemical mechanical polishing. In this paper, the results of flow factor, the performance of rough slider bearings and the mechanism of the CMP process for grain flow are briefly demonstrated. An improved CMP model, considering the partial hydrodynamic grain flow lubrication and elastic-plastic microcontact theory, is also proposed. The contact area ratio and the elastoplastic contact area ratio are presented to improve the understanding of CMP mechanisms.

Abstract: This paper analyzes theoretically the contact length derived from elastic-plastic mechanics and microcontact theory with the aim of improving the traditional method of predicting roughness factor though experiments. The accuracy of the analysis is verified through experiments. It transpires from the theoretical model that the contact length between a grinding wheel and a workpiece increases with decreasing curvature radius of peak, increasing hardness of the workpiece as well as increasing depth of cut. It is also revealed that the contact length is directly proportional to the square of 0.32 of the hardness, approximately, whilst the square root of surface roughness and the density of peak of the grinding wheel show less influence on the contact length. The analysis method has reduced the variation between predicted and experimental values than that of the old methods. These results will be beneficial in analysing and designing the product quality of grinding.

Abstract: Chemical mechanical polishing has been widely used to achieve global planarization of wafers. In this paper, an improved designed test rig is used to acquire the signals on chemical mechanical polishing. The shear force and temperature-rise are measured during chemical mechanical polishing process. The polishing temperature is measured by T-type thermocouples screwed behind the polishing interface of the carrier. The shear force is measured by a load transducer mounted on the lever and connected with the polishing head. The parameters including down force, rotation speed, particle size and volume flow rate of slurry are investigated. The experimental results provide a good index to end-point-detection. The theoretical simulation by the average lubrication equation coincides with the experimental results. This study contributes to the understanding of chemical mechanical polishing mechanism.

Abstract: In this study, a three-body microcontact model for rough surfaces is proposed in order to understand the effects of particles between surfaces on contact characteristics and its application on polishing of wafer. Both transitional surface-to-surface and particle-to-surface two-body microcontact simulations can be obtained according to the simplification of this model. In the three-body contact situation, the curves of contact area ratio versus dimensionless load are located in the range between two straight lines. The surface-to-surface two-body contact situation is the upper bound and the particle-to-surface two-body contact situation is the lower bound. As the value of D/σ increases, the contact situation will approach the pure particle-to- surface 2-body contact situation. The model also is used to study the wear mechanisms of the silicon wafer.