Study on the rheological properties and polishing properties of SiO₂@CI composite particle for sapphire wafer

Abstract

To study the rheological properties and polishing performance of magnetorheological fluids (MRFs) prepared with SiO2@carbonyl iron (CI) core-shell particles, SiO2@CI core-shell particles with different shell thicknesses were synthesized by an improved Stöber method controlling the amount of tetraethyl orthosilicate (TEOS). Then, four types of MRFs which dispersed with core-shell particles with thin shells, core-shell particles with thick shells, SiO2 particles, or carbonyl iron were prepared for sapphire polishing. The results show that the rheological properties of MRF based on thicker shell SiO2@CI are enhanced compared to those of MRFs prepared by dispersing abrasive and CI. Comparing with other MRFs, sapphire can obtain better surface quality when using thicker shell SiO2@CI. The MRF fabricated by SiO2@CI core-shell particles can increase the contact area between the abrasive and the workpiece and enhance the contact stress, which improves the solid-phase reaction rate and mechanical removal efficiency of silica and sapphire, thereby improve the polishing efficiency.

Basic exploration and research on magnetoelectric synergistic rheological finishing

“…Table 1 presents the experimental conditions in detail. During the test, 10 sct simethicone, SiO2@CIP composite particles with an average particle size of 4 μm, and diamond abrasives with an average particle size of 0.25 μm are uniformly dispersed at ratios of 70 wt%, 25 wt%, and 5 wt% and prepared into an MER fluid, in which SiO2@CIP composite particles have satisfactory electrorheological effect and magnetorheological effect characteristics (Pan et al, 2020a). As shown in Figure 6, after processing, a surface profiler (TALOR HOBSON PGI1240) is used to measure the surface profile along the AB direction, and a white light interferometer (BRUKER Contour GT-X) is used to measure the surface roughness and surface topography.…”

“…Feng et al (2020a) prepared a magnetic composite fluid (MCF) with α-cellulose in which α-cellulose and clustered cellulose were interwoven to increase the strength of the polishing pad and improve the influence of abrasives on the surface of the workpiece. Pan et al, 2020a prepared SI@CIP composite particles by combining abrasives and dispersed particles into a complex, which could effectively solve the problem of abrasive utilization. However, due to the difficulty of preparing composite particles and the high cost, better methods are still needed.…”

Investigation of cluster magnetorheological electro-Fenton composite polishing process for single-crystal GaN wafer based on BBD experimental method

“…However, apart from the high cost of equipment, the processing efficiency of the MR polishing method is very low. In our previous work, our research group proposed a cluster MR polishing technology with 'the flexible polishing pad' formed by the cluster MR fluid [18][19][20]. Compared with the traditional MR polishing method, the surface roughness Ra of the single-crystal sapphire polished by the cluster MR polishing decreased from 1.36 nm to 0.76 nm, and the MRR increased from 4.37 to 9.53 nm min −1 [21].…”

Study on new magnetorheological chemical polishing process for GaN crystals: polishing solution composition, process parameters, and roughness prediction model

“…CMP can realize the smooth and flat processing of GaN crystals, but its efficiency needs to be improved further. Magnetorheological finishing is a non-damage processing technology [21][22][23][24][25], which can effectively realize sub-nanometer processing of hard and brittle crystal materials such as sapphire [26,27], silicon carbide [28,29], and optical glass [30][31][32]. However, research on GaN magnetorheological finishing has not been reported.…”