Orientador: Paulo Roberto de Aguiar / Banca: José Alfredo Covolan Ulson / Banca: Fabricio Guimarães Baptista / Banca: Arthur Alves Fiocchi / Banca: Alessandro Roger Rodrigues / Resumo: O processo de retificação é um processo amplamente utilizado para produzir formas complexas e tolerâncias precisas em peças que são necessárias especialmente para a fabricação de componentes de engenharia. A retificação é um processo de manufatura situado na parte final da cadeia de usinagem, consistindo em uma operação de remoção de material da superfície da peça usinada e utiliza como ferramenta de corte o rebolo. No decorrer do processo de retificação a ferramenta de corte sofre desgaste e com isso, torna-se necessária a realização do processo de dressagem, cuja finalidade é restaurar a eficiência de corte do rebolo. A grande dificuldade no processo de retificação consiste em identificar o momento correto para a realização da dressagem e, para isso torna-se necessária a realização do monitoramento da ferramenta de corte (rebolo). Neste contexto, no presente trabalho desenvolveu-se uma técnica inovadora de diagnóstico da integridade superficial do rebolo, durante o processo de dressagem, baseada em imagens acústicas obtidas por meio de diafragma piezelétrico. Para isso, foram realizadas marcas (falhas) em um rebolo e, posteriormente, realizados ensaios com várias profundidades de dressagem, coletando sinais por meio de um sensor de emissão acústica e de um diafragma piezelétrico. Com base nesses sinais, foram avaliadas bandas de frequência para a obtenção de imagens acústicas que representassem com maior fidelidade e nitidez as marcas impressas no rebolo. Por fim, ambos os ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The abrasive machining process is a widely used process for producing complex shapes in work pieces and for providing precise tolerances that are especially required for the production of engineering components. Grinding is a manufacturing process placed at the end of the machining chain, consisting of an operation to remove material from the surface of the machined part and uses grinding wheels as a cutting tool. During the grinding process the cutting tool suffers wear and tear, and thus, it is necessary to perform the dressing process, whose purpose is to restore the cutting efficiency of the grinding wheel. The great difficulty in the grinding process is to identify the correct moment to perform the dressing, and for that reason, it is necessary to perform the monitoring of the cutting tool (grinding wheel). In this context, the present work made possible the development of an innovative technique to diagnose the surface integrity of the grinding wheel, during the dressing process, based on acoustic maps obtained through the piezoelectric diaphragm. Therefore, some patterns (marks) on a grinding wheel were performed and, later, tests were carried out with several dressing depths, acquiring signals from a commercial acoustic emission sensor and a piezoelectric diaphragm. Based on these signals, frequency bands were evaluated to obtain acoustic maps that represented with more fidelity and sharpness the marks inserted in the grinding wheel. Finally, both sensors (acoustic em... (Complete abstract click electronic access below) / Doutor

<p><font face="TimesNewRomanPSMT"> <p align="left">The aim of this study was to investigate the color stability of two provisional restorative materials used in crown and bridge cases upon exposure to different tea staining solutions and to evaluate the effectiveness of a polishing technique in removing the tea stains from the stained provisional restorative materials.</p> </font></p>

Analytical force and dynamic models for material removal processes such as end and face milling do not account for material and process related uncertainties such as tool wear, tool breakage and material inhomogeneity. Optimization of material removal processes thus requires not only optimal process planning using analytical models but also on-line monitoring of the process so that adjustments, if needed, can be initiated to maximize the productivity or to avoid damaging expensive parts. In this thesis, a Polyvinylidene Fluoride (PVDF) sensor based process monitoring method that is independent of the cutting conditions and workpiece material is developed for measuring the cutting forces and/or torque in milling. The research includes the development of methods and hardware for wireless acquisition of time-varying strain signals from PVDF sensor-instrumented milling tools rotating at high speeds and transformation of the strains into the measurand of interest using quantitative physics-based models of the measurement system. Very good agreement between the measurements from the low cost PVDF sensors and the current industry standard, piezoelectric dynamometer, has been achieved. Three PVDF sensor rosettes are proposed for measuring various strain components of interest and are shown to outperform their metal foil strain gauge counterparts with significantly higher sensitivity and signal to noise ratio. In addition, a computationally efficient algorithm for milling chatter recognition that can adapt to different cutting conditions and workpiece geometry variations based on the measured cutting forces/torque signals is proposed and evaluated. A novel complex exponential model based chatter frequency estimation algorithm is also developed and validated. The chatter detection algorithm can detect chatter before chatter marks appear on the workpiece and the chatter frequency estimation algorithm is shown to capture the chatter frequency with the same accuracy as the Fast Fourier Transform (FFT). The computational cost of the chatter detection algorithm increases linearly with data size and the chatter frequency estimation algorithm, with properly chosen parameters, is shown to perform 10 times faster than the FFT. Both the cutting forces/torque measurement methodology and the chatter detection algorithm have great potential for shop floor application. The cutting forces/torque measurement system can be integrated with adaptive feedback controllers for process optimization and can also be extended to the measurement of other physical phenomena.

This thesis is devoted to development of techniques to quantify chemical and mechanical influences during chemical mechanical polishing (CMP) near the surface of a polymer film, poly (biphenyl dianhydride-p-phenylenediamine) (BPDA-PDA). To quantify chemical modifications during CMP, an iterative algorithm has been proposed to extract depth profiles based on Ficks second law of diffusion in a multi-element system from data supplied by angle resolved x-ray photoelectron spectroscopy. It has been demonstrated that the technique can be used to quantify the depth of chemical modification of BPDA-PDA surfaces treated with alkaline solutions. Polymer chains near the surface realign themselves during CMP and polarized infrared spectroscopy is chosen in this thesis to quantify chain orientations induced by CMP to evaluate the mechanical influence. A theoretical framework based on a 44 matrix method for spectral simulation together with an oscillator model for BPDA-PDA has been used to obtain quantitative chain orientation information on a post-CMP BPDA-PDA sample by fitting simulated polarized infrared spectra to experimentally generated spectra. Verification of the oscillator model was established from the complex refractive indices of BPDA-PDA films, which were determined using a new method (R/T ratio method) developed in this thesis to extract complex refractive indices of films with biaxial symmetry from polarized transmission and reflection spectra.

A novel mirror finishing method using a conductive polymer as the tool electrode is presented. It has been known that the conductive polymers have many advantages, such as to conduct a micro-current, to be easily processed into various shapes, to hold abrasives, and to have an excellent wear resistance. The effects of particle size, machining time, concentration of electrolyte, working current, and load on the surface roughness and the removal depth of SUS-304 stainless steel are investigated.When the operative parameters are set for the particle size of 3 £gm, the concentration of electrolyte of 10 wt%, the working current ranged from 10 to 20 mA, and the load of 10 N, the surface roughness Rmax, which originally is 1.4 £gm, can be reduced to 0.17~0.24 £gm after the machining time of 3 min. The surface roughness Ra can be achieved to 7.897 nm under the optimal condition. In addition, experimental results show that there is an optimal region of the working current at the concentration of electrolyte of 10 wt%. According to the surface profiles and SEM micrographs, three machining regions can be classified as (1) the mechanical polishing region, (2) the electro-chemical buffing (ECB) region, and (3) the excessive corrosion region. To achieve a high-quality mirror-like surface, the machining region must be operated at the ECB region.

In this study, the wastewater from oxide chemical mechanical polishing (oxide-CMP) process of semiconductor wafer fabrication was treated by crossflow electro-ultrafiltration with self-prepared tubular inorganic membranes. First of all, a recipe of alumina (72 wt%), bentonite (8 wt%) and water (20 wt%) was determined for the extrusion of green tubes. The porous ceramic green tubes of 200 mm in length thus obtained were subjected to further curing, drying, and sintering processes. The inner and outer radii of the porous ceramic supports were 6.0 mm and 10.0 mm, respectively. Then, nanoscale TiO2 (i.e., the slip) was prepared by sol-gel method. On the tops of porous ceramic supports thin layers of nanoscale TiO2 were applied by the dip-coating method. To analyze the microstructures of tubular inorganic membranes and confirm the nanoscale TiO2 films, a scanning electron microscope equipped with energy-dispersive X-ray analyzer (SEM-EDS) and X-ray diffractometer (XRD) were employed. The self-prepared tubular inorganic composite membranes (TICMs) were futher characterized by permporometry and Kelvin equation to determine their pore size distributions and nominal pore sizes. In addition, through the employment of polyethylene glycol (PEG) of different molecular weights and total organic carbon analysis method, the molecular weight cut-off (MWCO) and tightness coefficient of each TICM was determined. It was found that the self-prepared TICMs were suitable for ultrafiltration applications. In this work, wastewater from the oxide-CMP process of semiconductor wafer fabrication was treated by crossflow electro-ultrafiltration with self- prepared TICMs. The permeate qualities were evaluated. Experimental results have shown that permeate of a higher filtration rate, a turbidity of below 1 NTU, 90% removal of total suspended solids, and a removal efficiency of greater than 80% for soluable silica could be obtained under the conditions of an electric filed strength of 30 V/cm and transmembrane pressure of 5 kgf/cm2. For permeate to meet the feed water requirements for the ultrapure water system, it has to be further treated to lower its silica content to ¡Ø 6 mg/L. Overall speaking, by incorporation of the tubular inorganic composite membranes prepared in this work into the novel electrofiltration treatment module for the treatment of oxide-CMP wastewater would yield permeate suitable for the purpose of reclamation.

Magnesium oxychloride cement (MOC) based grinding and polishing bricks developed for polishing of granite based ceramic tiles were produced and characterized. For surface grinding 46 and 180 grit size SiO2 powder embedded MOC based abrasive bricks / for polishing 600 and 1200 grit size SiC powder embedded MOC based abrasive bricks followed by neat (unreinforced) MOC pastes were applied on ceramic tiles. Three different neat MOC pastes depending on MgO/MgCl2 molar ratio in the paste e.g. 6/1, 7/1, and 8/1, were formed and evaluated. Grinding bricks were formed by adding 30 weight percentage, wt%, of both SiO2 powders. Polishing bricks were formed by adding 20, 25, and 30 wt% of both SiC powders. X-Ray diffraction analyses revealed that MOC F5 was the main crystalline phase in the neat MOC pastes. Additions of both SiO2 and SiC powders enhanced mechanical properties namely / compressive strength and abrasion resistance, chemical durability in water and polishing ability of MOC paste. More than 25 wt% addition of SiC powders had a tendency to decrease the compressive strength and water resistance of MOC paste. Polishing performance of abrasive bricks was evaluated in terms of mean surface roughness of ceramic tiles and abrasive brick consumption upon polishing. Scanning Electron Microscope examinations revealed the evidences of the reasons that 25 wt% SiC powder embedded abrasive bricks has the best qualifications in terms of abrasion resistance and polishing performance.

This study addresses three major parts: (1) to establish the technology for the preparation of tubular ceramic membrane substrates; (2) to establish the technology for the preparation of tubular carbon/ceramic membranes; and (3) to reclaim water from chemical mechanical polishing (CMP) wastewaters by a combined treatment system of a novel simultaneous electrocoagulation/electrofiltration (EC/EF) process coupled with laboratory-prepared tubular composite membranes (TCMs) and evaluate its feasibility of water recycling and operating cost. First, in this work the green substrates of tubular porous ceramic membranes consisting of corn starch were prepared using the extrusion method, followed by curing, drying, and sintering processes. Experimental results have demonstrated that an addition of starch granules to the raw materials would increase the porosity, pore size, and permeability of the sintered matrices but accompanied by a decrease of the compressive strength. It revealed that the membrane substrates with desired pore sizes and permeability could be obtained by adding a proper amount of corn starch. The nominal pore sizes of the prepared membrane substrates were ranging from 1 to 2 £gm. The membrane substrates thus obtained are suitable for crossflow microfiltration applications. Second, the carbon/alumina TCMs and carbon fibers/carbon/alumina TCMs were obtained by the chemical vapor deposition (CVD) method resulting in a pore size distribution of 2 to 20 nm and a nominal pore size ranging from 3 to 4 nm. Besides, during the CVD process the reaction temperature was found to be the main factor for influencing the pore size of carbon fibers/carbon/alumina TCMs and the type of carbon fibers. When the reaction temperature was above or equal to 1000 ¢J, the pore size of TCMs increased due to the pyrolysis of thin carbon layers. The ¡§Tip-Growth¡¨ mechanism was found for tubular carbon fibers formation under such conditions. On the other hand, ¡§Base-Growth¡¨ (also known as ¡§Root-Growth¡¨) mechanism was found for curved and irregular carbon fibers formation when reaction temperature was under or equal to 950 ¢J. Third, for reclaiming water from CMP wastewaters, experimental results of laboratory-prepared carbon/alumina TCMs incorporated into the custom-made EC/EF treatment module used was found to be capable of treating oxide-CMP wastewater in a proper manner. Permeate thus obtained had a turbidity of below 0.5 NTU and the removal efficiencies of TS (total solids content) and Si were 80% and 93 %, respectively. Further, for understanding the applicability of fractional factorial design and Taguchi experimental design, two laboratory-prepared carbon fibers/carbon/alumina TCMs (i.e., Tube B and Tube E obtained from two different preparation conditions) incorporated into the EC/EF treatment module were chosen for evaluating the performance of CMP wastewaters treatment. Permeate obtained based on the fractional factorial design of experiments had a turbidity of below 1.0 NTU and the removal efficiencies of TOC (total organic carbon), Cu and Si were all above 80 % except for the TS (i.e., ranging from 72 to 74%). Permeate obtained based on the Taguchi experimental design had a turbidity of below 0.3 NTU and the removal efficiencies of TS, TOC, Cu and Si were ranging from 82 to 91%. Apparently, similar optimum operating conditions were obtained from the fractional factorial design and Taguchi experimental design. Permeate thus obtained could be reused as the make-up water of cooling towers. The operating cost of Cu-CMP wastewater treatment based on a total water reclaim of 600 m3 per day was determined to be NT$ 98 (i.e., US$ 3.22) and NT$ 35 (i.e., US$ 1.05) per m3 of permeate for Case 1 (i.e., the filtration area of 0.0189 m2 in one EC/EF module) and Case 2 (i.e., the filtration area of 0.0801 m2 in one EC/EF module), respectively.

This dissertation presents a series of studies related to the characterization and optimization of consumables during Chemical Mechanical Planarization (CMP). These studies are also evaluated with the purpose of reducing the cost of ownership as well as minimizing the potential environmental impacts. It is well known that pad-wafer contact and pad surface micro-structure have significant impacts on polishing performance. The first study in this dissertation investigates the effect of pad surface contact and topography on polishing performance during copper CMP. Two different types of diamond discs (3M A2810 disc and MMC TRD disc) are used to condition the polishing pad. Pad surface contact area and topography are analyzed using laser confocal microscopy and scanning electron microscopy (SEM) to illustrate how variations in pad surface micro-texture affect the copper removal rate and the coefficient of friction (COF). Polishing results show that the 3M A2810 disc generates significantly higher COF (16%) and removal rate (39%) than the MMC TRD disc. Pad surface analysis results show that the 3M A2810 disc and MMC TRD disc generate similar pad surface height probability density function and pad surface abruptness. On the other hand, the MMC TRD disc generates large flat near contact areas that correspond to fractured and collapsed pore walls while the 3M A2810 disc generates solid contact area and clear pore structures. The fractured and collapsed pore walls generated by the MMC TRD disc partly cover the adjacent pores, making the pad surface more lubricated during wafer polishing and resulting in a significantly lower COF and removal rate. In the next study, the individual "large" pad surface contact areas are differentiated from the "small" contact areas and their role in copper CMP is investigated. Surface topography and the structure of a typical individual large contact area are examined via laser confocal microscopy and SEM. In addition, the Young's Modulus of the pad surface material is simulated. A case study is presented to illustrate the role of the individual large contact area of IC1000 K-groove pad in copper CMP. SEM analysis shows that the individual large pad surface contact areas are induced by fractured pore walls and loosely attached pad debris. Simulation results indicate that individual large contact areas correspond to very low values of the Young's modulus (about 50 MPa). Such low values indicate that the pad material is soft and the summit underlying the individual large contact is not fully supported. As a result, individual large contact area implies low contact pressure and may contribute little to removal rate. Case study results confirm that the individual large contact area has minimal contribution to removal rate and indicate that the removal rate is mainly caused by small individual contact areas. In our case, small contact areas correspond to those smaller than 9 square microns. We believe that this methodology can be also applied for other kinds of pad, although the threshold values that may define "small" and "large" individual contact areas for different pads and processes need to be further investigated. In the third study, the effect of pad surface micro-texture in interlayer dielectric CMP is also investigated. Blanket 200-mm oxide wafers are polished and the polishing pad is conditioned under two different conditioning forces (26.7 and 44.5 N). Results show that when conditioning force is increased from 26.7 to 44.5 N, oxide removal rate increases by 65% while COF increases by only 7%. Pad surface contact area and topography are measured and analyzed to illustrate their effects on the oxide removal rate. While the two conditioning forces generate similar pad surface abruptness, pad surface contact area is significantly lower (by 71%) at the conditioning force of 44.5 N. Such dramatic decrease in pad surface contact area leads to a significant increase in local contact pressure and therefore results in a significant increase in oxide removal rate. The oxide removal rate and local contact pressure exhibits a Prestonian relationship. Besides the above studies on the effect of the pad surface micro-texture during blanket wafer polishing, the fourth study investigates how pad micro-texture affects dishing and erosion during shallow trench isolation (STI) patterned wafer polishing. Two different types of diamond discs (3M A2810 disc and MMC TRD disc) are used to condition the pad during wafer polishing. Dishing and erosion analysis for the patterned wafer polishing is performed using a surface profiler. To illustrate the effect of pad surface micro-texture on dishing and erosion, pad surface abruptness and mean pad summit curvature are analyzed using laser confocal microscopy. Polishing results show that the two discs generate similar blanket wafer removal rates, while the MMC TRD disc generate significantly higher dishing and erosion than the 3M A2810 disc during patterned wafer polishing. Results of pad surface micro-texture analysis show that the MMC TRD disc generates sharper asperities with higher mean pad summit curvature than the 3M A2810 disc, resulting in higher dishing and erosion. Another contribution of this dissertation is the development of a slurry film thickness quantification technique using ultraviolet-enhanced fluorescence. The technique is developed to measure slurry film thickness at any location of interest. In the next study of this dissertation, this new technique is applied to determine how two different slurry application/injection schemes (standard pad center area application method and novel slurry injection system) along with various polishing conditions such as sliding velocity, ring pressure and slurry flow rate affect slurry availability in the bow wave region of the polisher. For the standard pad center area application method, slurry is directly applied onto the pad center area and a large amount of fresh slurry flow directly off the pad surface without flowing to the pad-retaining ring interface due to the centrifugal forces. For the novel slurry injection system, slurry is introduced through an injector that is placed adjacent (<3 cm) to the retaining ring on the pad surface. Such a close distance between the injector and retaining ring allows most of the fresh slurry to be delivered efficiently to the leading edge of the retaining ring after it is injected onto the pad surface. Results show that the novel slurry injection system generates consistently thicker bow waves (up to 104 percent) at different sliding velocities, slurry flow rates and ring pressures, therefore providing more slurry availability for the pad-retaining ring interface and potentials for slurry consumption reduction in CMP processes. First order calculations yield estimates of slurry savings associated with the novel slurry injection system ranging between 8 and 48 percent depending on specific process conditions. In the last study of this dissertation, the effect of retaining ring slot design and polishing conditions on slurry flow dynamics at the bow wave is investigated. The ultraviolet-enhanced fluorescence technique is employed to measure the slurry film thickness at the bow wave for two retaining rings with different slot designs. Multiple sliding velocities, slurry flow rates and ring pressures are investigated. Results show that the retaining ring with the sharp angle slot design (PEEK-1) generates significantly thicker (on average 48%) slurry films at the bow wave than PEEK-2 which has a rounded angle slot design. For PEEK-1, film thickness at the bow wave increases with the increasing of flow rate and ring pressure and decreases with the increasing of sliding velocity. On the other hand, film thickness at bow wave does not change significantly for the PEEK-2 ring at different polishing conditions indicating an apparent robustness of the PEEK-2 design to various operating conditions. With retaining rings having different designs, and all else being the same, a thinner bow wave is preferred since it is indicative of a ring design that allows more slurry to flow into the pad-wafer interface. Therefore, the work underscores the importance of optimizing retaining ring slot design and polishing conditions for efficient slurry utilization.

Precision optics can be accurately fabricated by computer controlled optical surfacing (CCOS) that uses well characterized polishing tools driven by numerically controlled machines. The CCOS process is optimized to vary the dwell time of the tool on the workpiece according to the desired removal and the calibrated tool influence function (TIF), which is the shape of the wear function by the tool. This study investigates four major topics to improve current CCOS processes, and provides new solutions and approaches for the next generation CCOS processes.The first topic is to develop a tool for highly aspheric optics fabrication. Both the TIF stability and surface finish rely on the tool maintaining intimate contact with the workpiece. Rigid tools smooth the surface, but do not maintain intimate contacts for aspheric surfaces. Flexible tools conform to the surface, but lack smoothing. A rigid conformal (RC) lap using a visco-elastic non-Newtonian medium was developed. It conforms to the aspheric shape, yet maintains stability to provide natural smoothing.The second topic is a smoothing model for the RC lap. The smoothing naturally removes mid-to-high frequency errors while a large tool runs over the workpiece to remove low frequency errors efficiently. The CCOS process convergence rate can be significantly improved by predicting the smoothing effects. A parametric smoothing model was introduced and verified.The third topic is establishing a TIF model to represent measured TIFs. While the linear Preston's model works for most cases, non-linear removal behavior as the tool overhangs the workpiece edge introduces a difficulty in modeling. A parametric model for the edge TIFs was introduced and demonstrated. Various TIFs based on the model are provided as a library.The last topic is an enhanced process optimization technique. A non-sequential optimization technique using multiple TIFs was developed. Operating a CCOS with a small and well characterized TIF achieves excellent performance, but takes a long time. Sequential polishing runs using large and small tools can reduce this polishing time. The non-sequential approach performs multiple dwell time optimizations for the entire CCOS runs simultaneously. The actual runs will be sequential, but the optimization is comprehensive.