Papers by Author: Hui Yuan

Abstract: This paper studied the effects of the off-process conditioning parameters on the pad performances. The pad conditioning was evaluated based on the measurement of pad removal rate, the observation of the conditioned pad surface. The performances of conditioned pads were evaluated also by the material removal rate (MRR) and the surface roughness of polished wafers in the CMP experiments of LiTaO3 crystal wafers.

Abstract: In this paper, the wear behavior of the ID (inner diameter) saw blade in the cutting process of silicon ingot was observed with SEM. Its wear mechanism was discussed and the relation between the blade wear and vibration, deflection was analyzed. The results show that the blade worn manners include flatted diamond, micro-fractured diamond, macro-fractured diamond, pulled-out hole, tortoise-fractured bond, and polished bond. In the abnormal working stage of a blade, however, the working surface of the blade is displayed mainly with pulled out diamond, flatted diamond, macro-fractured diamond grains. Abnormal initial tension condition will induce severe vibration and deflection, and so then lots of diamond grits fractured or pulled out too early.

Abstract: Lithium tantalite (LiTaO3) possesses a combination of unique electro-optical, acoustic, piezoelectric, pyroelectric and non-linear optical properties, making it a suitable material for applications in high frequency, broad width-band SAW and BAW components, filters in television receivers, etc. The surface quality of LiTaO3 wafers decides the performances of the devices. In this paper, the technique of chemical mechanical polishing (CMP) was used to polish LiTaO3 wafers. The influences of the polishing parameters on the CMP processes of LiTaO3 wafers were analyzed in detail based on the measurement of the material removal rate, surface roughness and topograph of the polished wafers in different polishing conditions.

Abstract: In this paper, the scratching processes by a diamond indentor under the loads linearly increased from zero were studied to assess the mechanical behavior of LiTaO3 crystal wafer. Material removal mechanism of LiTaO3 crystal by mechanical loads was analyzed based on the measured acoustic signals in the scratching processes and the observation on the scratched surfaces of LiTaO3 wafers. The chemical mechanical polishing (CMP) processes of LiTaO3 wafers were analyzed in detail according to the observation and measurement of the polished surfaces of LiTaO3 wafers with SEM and XRD. The research results show that there exist four regimes along the scratched groove with the increasing of down force in a scratching process of LiTaO3 crystal wafer, and the critical load for each regime is affected by the loading speed and final load, etc. When H2O2 and KOH are added into the polishing slurry, the material of LiTaO3 wafer is removed by chemical reaction and mechanical action sequentially in the CMP processes, and the material removal rate increases while the surface roughness is improved.

Abstract: As one of the excellent decorative materials ceramic tiles must be ground and polished to present the glossy surface. In this paper the ceramic tiles were edge ground by diamond cup wheels in the special designed test machine. The surface morphology of the polished ceramic tiles and the wear of diamond cup wheel were examined by Scanning electron microscopy (SEM). The wear resistance of diamond cup wheel and the materials’ removal process of ceramic tiles had been tested. The results showed that the wear of diamond cup wheel was stable when grinding with high grinding ratio. The ground surface showed that only the fracture of ceramic tiles was acted by diamond grits during grinding with water by means of good quality diamond cup wheel.

Abstract: Diamond tool based on Ni-Al self-propagating high temperature synthesis (SHS) was introduced in this paper. Different heating methods such as muffle furnace, vacuum furnace and induction were used to ignite the Ni-Al-diamond SHS system. The morphology and microstructure of the Ni-Al-diamond composite were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). It was found that SHS Ni-Al-diamond composite ignited by induction heating owned the best morphology and microstructure to work as diamond tool.