Fundamental Study On The Processing Of Sapphire's Ductile Regime Based On The Semi-fixed Abrasive Plate

Sapphire (α-alumina, Al₂O₃) is one of the best substrate materials, which take on the brilliant physical and chemical property, and it is the typical crisp and hard advanced ceramics material at the same time. Sapphire is extensive used for high speed IC chipset, thin films substrate and electronic component and mechanical element. Along with the development of the technology of electronics and solid state lighting, the higher requirements for ultra-precision processing are suggested, the pursuit for effective and reducing or eliminating the surface defects inducing the ductile regime lapping processing technology, namely, the chip are cut thorough shear style by the abrasive when processing the crisp materials, there are not crack on the processed surface and subsurface and not irregularity caused by crisp peeling. So the ductile regime processing is a next to nothing defects processing style. It is the promising processing style for ceramics, glasses, and optics & semiconductor materials. In order to control effectively the ductile regime lapping, an original technology 'semi-fixed abrasive machining technology' is proposed by the project group, the 'semi-fixed abrasive plate' (SFAP) is a new abrasive tool that was molded with the organic bond and abrasive under the lower temperature, whose abrasive is arranged uniform and contour on the surface, the combine intensity of abrasive is weaker than the concretion abrasion wheel, so it could reduce or eliminate the compellent scratch and the processing randomicity of the abrasive distribution could be avoided too. The local acting force on the processed surface is uniform distribution, so the SFAP have the characteristic that the processed surface affected layer is thin, the surface quality controllability is good and have the higher processing efficiency.The ductile regime lapping experimental research is employed based on the SFAP. The critical condition of ductile to brittle transformation of sapphire is studied by the experiment method of nanoindentation and nano-scratch. In order to design the ductile lapping parameter the contact characteristic between the SFAP with workpiece is studied by fractal theory and contact experiment. The testing instrument and method such as nanoindentation, nano-scratch, microcosmic roughness, SEM, EDS, AFM and XRD are used to analyze the surface defect and integrality of the SFAP lapping process. At last the ductile processing appraisal is performed. The main works and research results in the paper are summaried as following:1. The critical condition of ductile to brittle transformation of sapphire was obtained by the nano test method such as the nanoindentation and nano-scratch. The critical cut is about 300nm.2. The contact action between SFAP and workpiece was analyzed by the fractal theory. At first, the surface topography of SFAP was simulated by the fractal theory according to the roughness eigenvalue that was obtained by Digital Microscope Resources Center (DMRC) (VHX-600 Series, the Keyence Corporation). The roughness eigenvalue of simulation surface was matching with the measured value, so the simulation results could be used to carry out the contact analysis. The relations of contact area with load were obtained by calculating and experiment; it was the basis of the experiment parameter.3. The mathematic model of ductile regime processing was set up according to the critical condition and contact parameter, and then the ductile control parameter was obtained. The contrast experiment of SFAP and loose abrasive processing were made to get the following results: the surface topography of workpiece that was processed by the W14 B4C SFAP was superior to that were processed by the W3.5 B4C loose abrasive. So the better surface topography could be obtained processing used the SFAP than the loose abrasive under the same time and condition. The SFAP processing could reduce the working procedure and increase production efficiency. The high resolution AFM and SEM were used to test the workpiece surfaces that were processed by SFAP, the microcracks were not found and the plastic flow similar metal-cutting were found. The plastic flow matters were measured by the EDS, the results showed that the compositions of it were 41.15% 0 and 58.85% Al, so the chips were the sapphire and not the cast of the SFAP. The abrasive of the SFAP were bonded by the bonding agent, so the abrasive processing was similar the micro-blade cutting and could achieve the ductile regime processing. On the basis of the above, the SFAP processing was more efficient and precision than the same granularity loose abrasive.4. The estimate of the ductile regime processing was that there were not flaw on the processed surface and the affected layer was less than hundreds nanometer. The nanoindentation and low-angle X-ray diffraction technology were employed to test the thickness of the affected layer based on the analysis of the existing test method. The measured value of the several test method were about 400nm. It could explain that the SFAP processing in this dissertation were in the ductile regime.