Micro-Quality Control on Ultra-Precision Machining of Sapphire Substrates

2010 ◽  
Vol 102-104 ◽  
pp. 738-741
Author(s):  
Hai Zhou ◽  
Li Gang Bai ◽  
Dai Pin Wang
Keyword(s):  
Surface Roughness ◽  
Ph Value ◽  
Diamond Wheel ◽  
Precision Machining ◽  
New Approach ◽  
Sapphire Substrates ◽  
Ductile Mode ◽  
Ultra Precision ◽  
Main Factors

This paper proposed a new approach to control the micro-quality of sapphire substrate, in order to grow GaN on substrate. The main factors that influence macro-quality are the method of slicing, grinding and polishing. Thread speed of slicing is less than 0.5m/s. Ductile mode grinding of substrate is achieved by #3000 diamond wheel and feed of 1μm/r. The suitable polishing conditions are that the SiO2 grain size is less than 10nm, the concentration SiO2 is 3％, pH value of polishing liquid is 10.5 and polishing stress is 190Pa. The undamaged substrates have been obtained steadily. The surface roughness RMS is less than 0.4 nm.

Grinding Performance Evaluation of the Developed Chemo-Mechanical Grinding (CMG) Tools for Sapphire Substrate

2012 ◽  
Vol 565 ◽  
pp. 105-110 ◽  
Author(s):  
Zhi Gang Dong ◽  
Shang Gao ◽  
P. Zhou ◽  
Ren Ke Kang ◽  
Dong Ming Guo
Keyword(s):  
Surface Roughness ◽  
Performance Evaluation ◽  
Surface Quality ◽  
Sapphire Substrate ◽  
Physicochemical Characteristics ◽  
Diamond Wheel ◽  
Mechanical Grinding ◽  
Sapphire Substrates ◽  
Grinding Performance

In order to improve the surface quality of sapphire substrates ground by diamond wheel, the chemo-mechanical grinding (CMG) tools for sapphire grinding was investigated in this paper. According to the processing principle of CMG, three CMG tools with different abrasives of SiO2, Fe2O3 and MgO were developed respectively. The compositions of the CMG tools were designed and optimized based on the physicochemical characteristics of sapphire. The grinding experiments were performed with the developed CMG tools and the grinding performance of three kind of tools were evaluated by comparing the surface roughness and the MRR of sapphire. The experiment results show that the grinding performance of SiO2 CMG tool was worst. The surface roughness and MRR corresponding to SiO2 CMG tool were all significantly poorer than Fe2O3 and MgO CMG tools. The highest MRR could be obtained by Fe2O3 CMG tool, but the best surface quality was obtained by MgO CMG tool.

Characterization of Cutting-Induced Heat Generation in Ultra-Precision Milling of Aluminium Alloy 6061

2013 ◽  
Vol 552 ◽  
pp. 201-206
Author(s):  
Su Juan Wang ◽  
Suet To ◽  
Xin Du Chen
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Heat Generation ◽  
Feed Rate ◽  
Dimensional Accuracy ◽  
Precision Machining ◽  
Machined Surface ◽  
Single Crystal Diamond ◽  
Ultra Precision ◽  
Alloy 6061

The technology of ultra-precision machining with single crystal diamond tool produces advanced components with higher dimensional accuracy and better surface quality. The cutting-induced heat results in high temperature and stress at the chip-tool and tool-workpiece interfaces therefore affects the materials and the cutting tool as well as the surface quality. In the ultra-precision machining of al6061, the cutting-induced heat generates precipitates on the machined surface and those precipitates induce imperfections on the machined surface. This paper uses the time-temperature-precipitation characteristics of aluminum alloy 6061 (al6061) to investigate the effect of feed rate on the cutting-induced heat generation in ultra-precision multi-axis milling process. The effect of feed rate and feed direction on the generation of precipitates and surface roughness in ultra-precision raster milling (UPRM) is studied. Experimental results show that heat generation in horizontal cutting is less than that in vertical cutting and a larger feed rate generates more heat on the machined workpiece. A smaller feed rate produces a better surface finish and under a larger feed rate, scratch marks are produced by the generated precipitates and increase surface roughness.

Study on the Effect of Tool Rake Angle on Cutting Vibration in Precision Machining

2004 ◽  
Vol 471-472 ◽  
pp. 127-131
Author(s):  
Gui Cheng Wang ◽  
Li Jie Ma ◽  
Hong Jie Pei
Keyword(s):  
Theoretical Analysis ◽  
High Speed ◽  
Cutting Speed ◽  
Rake Angle ◽  
Precision Machining ◽  
Turning Operation ◽  
Cutting Vibration ◽  
Main Factors ◽  
Theory And Experiment

The cutting vibration is one of the main factors to affect precision machining. In this paper, the influence of tool rake angle on cutting vibration is studied at different cutting speed in turning operation, and corresponding theoretical analysis is made. The experiment results show that: the amplitude of machining vibration gradually decreases with tool rake angle increasing; while rake angle o g <0°, the biggest amplitude occurs at V=50~70m/min; While o g ≥0°, it is at V=160~180m/min. Moreover, theory and experiment foundation is presented on avoiding the biggest amplitude range so as to guarantee quality of precision machining at high speed.

A Research on Ultra Precision Machining for Ti-6AL-4V Alloy Based Biomedical Applications Using Nanopositioning Mechanism

2013 ◽  
Vol 25 ◽  
pp. 157-173 ◽  
Author(s):  
Nam Su Kwak ◽  
Jae Yeol Kim ◽  
Dae Gwang Park
Keyword(s):  
Piezoelectric Actuator ◽  
Biomedical Applications ◽  
Power Transmission ◽  
Control Method ◽  
Precision Machining ◽  
Ductile Mode ◽  
Single Crystal Diamond ◽  
Ultra Precision ◽  
Flexure Guide ◽  
And Control

In this study, piezoelectric actuator, flexure guide, power transmission element and control method are considered for nanopositioning system apparatus. The main objectives of this thesis were to develop 2-axis nanostage which enables 2-axis control with the aid of piezoelectric actuator, and to improve the precision of the ultra-precision lathe (UP2) which is responsible for the ductile mode machining of the hardened-brittle material where the machining uses a the single-crystal diamond. Through simulation and experiments on ultra-precision positioning, stability and priority of the nanopositioning system with 2-axis nanostage and control algorithm are developed using Matlab/Simulink. Then the system, is applied to analyze surface morphology of the titanium alloy (Ti-6Al-4V)

Comparison of Processing Features between Semi Bonded Abrasive Lapping and Loose Abrasive Lapping

2009 ◽  
Vol 416 ◽  
pp. 439-442
Author(s):  
Xun Lv ◽  
Ju Long Yuan ◽  
Dong Hui Wen
Keyword(s):  
Surface Roughness ◽  
Material Removal Rate ◽  
Material Removal ◽  
Removal Rate ◽  
Processing Parameters ◽  
Good Surface ◽  
Ultra Precision ◽  
New Processing ◽  
Short Time

Semi bonded abrasive lapping is an effective ultra-precision lapping method. It can obtain good surface quality of workpiece in short time. This paper focused on the differences of processing features by comparing semi bonded abrasive lapping and loose abrasive lapping in several groups processing parameters. The results showed that the surface roughness of workpiece in semi bonded abrasive lapping was far superior to that of loose abrasive lapping in same processing parameters. And the MRR (material removal rate) of semi bonded abrasive lapping was slightly lower than that of loose abrasive lapping. For these features of semi bonded abrasive, a new processing flow would also be proposed in this paper.

Thermal Analysis of Laser Irradiation of Fused Silica

2011 ◽  
Vol 314-316 ◽  
pp. 1960-1964 ◽  
Author(s):  
Peng Yao ◽  
Ya Dong Gong ◽  
Suo Xian Yuan ◽  
Tian Feng Zhou ◽  
Ji Wang Yan ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Surface Roughness ◽  
Laser Irradiation ◽  
Fused Silica ◽  
Maximum Temperature ◽  
Precision Grinding ◽  
Micro Cracks ◽  
Ductile Mode ◽  
Ultra Precision ◽  
Simulation Results

To grind fused silica in ductile mode, surface and subsurface micro cracks (SSMC) on ground fused silica should be repaired by CO2 laser irradiation before ultra-precision grinding. In this paper, 2D thermal analysis of single pass laser irradiation of fused silica was conducted, and the simulation results were discussed by comparing with the experiment results. To repair SSMC and decrease the surface roughness of ground fused silica simultaneously, the maximum temperature on the surface during laser irradiation should be controlled higher than 3280 K and lower than 3550 K.

A Study on Surface Quality of GaN with CMP Polishing Process

2011 ◽  
Vol 291-294 ◽  
pp. 1764-1767
Author(s):  
Wei Li ◽  
Ming Ming Ma ◽  
Bin Hu
Keyword(s):  
Surface Roughness ◽  
Particle Size ◽  
Gallium Nitride ◽  
Surface Quality ◽  
Chemical Reaction ◽  
Experimental Result ◽  
Precision Machining ◽  
Polishing Process

This paper introduced a polishing process for planarization of gallium nitride (GaN) wafer by polishing slurry that is made up by the chemical reaction with H2O2 solution and iron. Some different polishing parameters in the polishing process has been analyzed, which affect the surface quality of wafers, such as slurry particle size, polishing times, polishing slurry etc., and trying to improve the polishing process by optimization of the polishing parameters. The experimental result showed that this polishing method has an effect on the surface quality of GaN wafers, finally, the efficient and precision machining with surface roughness of GaN wafers of Ra0.81 nm has been gained by the CMP polishing process.

An Experimental Investigation of Optimal Grinding Condition for Aspheric Surface Lens Using Full Factorial Design

2007 ◽  
Vol 329 ◽  
pp. 27-32 ◽  
Author(s):  
Seung Yub Baek ◽  
Jung Hyung Lee ◽  
Eun Sang Lee ◽  
H.D. Lee
Keyword(s):  
Surface Roughness ◽  
Ground Surface ◽  
Diamond Wheel ◽  
Aspheric Surface ◽  
Precision Grinding ◽  
Spherical Lens ◽  
Ultra Precision ◽  
Ground Surface Roughness ◽  
Grinding System ◽  
Micro Lens

To enhance the precision and productivity of ultra precision aspheric surface micro lens, the development of ultra-precision grinding system and process for the aspheric surface micro lens are described. In this paper, an ultra-precision grinding system for manufacturing the aspheric surface micro lens was developed by considering the factors affecting the grinding surface roughness and profile accuracy. This paper deals with the mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and with the spherical lens of BK7. The optimization of grinding conditions with respect to ground surface roughness and profiles accuracy is investigated by design of experiments.

Nondestructive Characterization of GaN Films Grown at Low and High Temperatures

1999 ◽  
Vol 591 ◽  
Author(s):  
C.H. Yana ◽  
H.W. Yao ◽  
J.M. Van Hove ◽  
A.M. Wowchak ◽  
P.P. Chow ◽  
...  
Keyword(s):  
Surface Roughness ◽  
High Temperatures ◽  
Sapphire Substrates ◽  
Wurtzite Crystal Structure ◽  
Phonon Spectra ◽  
Scattering Geometry ◽  
Back Scattering ◽  
Nondestructive Characterization

ABSTRACTGaN films grown on GaAs and sapphire substrates by molecular beam epitaxy (MBE) and metalorganic vapor phase epitaxy (MOVPE) at both low and high temperatures (LT and HT) were characterized by Raman scattering and variable angle spectroscopic ellipsometry (VASE). Optical phonon spectra of GaN films are obtained through back-scattering geometry. Crystal quality of these films was qualitatively examined using phonon line-width. Phonon spectra showed that the HT GaN has wurtzite crystal structure, while LT GaN and GaN/GaAs have cubic-like structures. Thickness nonuniformity and defect-related absorption can be characterized by pseudo dielectric functions directly. Surface roughness also can be determined by using an effective-medium approximation (EMA) over-layer in a VASE analysis. Anisotropic optical constants of GaN, both ordinary and extraordinary, were obtained in the spectral range of 0.75 to 6.5 eV with the consideration of surface roughness, through the small and large angles of incidence, respectively. The film thickness of the GaN was accurately determined via the analysis as well.

Experiment Study on ELID Grinding of TN85 Cermets

2011 ◽  
Vol 175 ◽  
pp. 131-135
Author(s):  
Fu Qiang Tong ◽  
Fei Hu Zhang ◽  
Dian Rong Luan
Keyword(s):  
Metal Matrix ◽  
High Hardness ◽  
Diamond Powder ◽  
Diamond Wheel ◽  
Precision Machining ◽  
Grinding Wheel ◽  
Powder Particle Size ◽  
Matrix Composites ◽  
Elid Grinding ◽  
Ultra Precision

TN85 cermets is one kind of particle reinforced metal matrix composites, which is high hardness, good wear resistance, and bring great difficulties in processing, so it is necessary to study the processing performance. During the test on ELID grinding TN85 cermets, it is found that plastic removal is the main ways during grinding TN85 cermets materials. The powder particle size of W2.5 diamond wheel is successfully used in full removal of TN85 cermets plastic, the surface roughness value of rms: 16.81nm and Ra: 12.52nm. The results showed that: ELID grinding wheel with diamond powder technology can be used in ultra-precision machining TN85 cermets.

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