Experimental Study On Fabrication Of Fixed Soft/Hard Abrasive Pellet Combined Plate And Sapphire Lapping

Sapphire has become the main material for the preparation of LED substrates and optical windows due to its stable chemical properties,high mechanical strength and strong photoelectric permeability.The quality of the sapphire substrate directly affects the growth quality of the epitaxial layer,and the surface flatness of the sapphire window device has an important influence on the optical transmittance,so the requirements for the flatness of the sapphire surface are high.Sapphire has high hardness and brittleness,and is a typical difficult-to-process material,which makes its processing from raw materials to products extremely complex and long in processing cycles.Lapping is the key technology of sapphire flattening,and its tools are mostly fixed abrasives lapping plate.Because only a single soft abrasive or hard abrasive is consolidated on the lapping plate,it is difficult to balance processing efficiency and processing quality.Therefore,sapphire lapping methods that take into account processing efficiency and processing quality have become the focus of research.Based on the processing characteristics of soft and hard abrasives,this paper proposes the concept of processing sapphire with soft and hard abrasives in order to achieve both processing quality and processing efficiency.In order to explore whether the solid-phase reaction of sapphire occurs or not and its reaction efficiency under lapping conditions,the influencing factors of the solid-phase reaction of sapphire were investigated.Hard abrasives were work with soft abrasive to solve the problem of low materials removal rate of soft abrasives.In order to ensure the processing quality,the matching exploration of fixed soft abrasive pellets and fixed hard abrasive pellets was carried out.According to the matching conditions of the fixed soft abrasive pellets and fixed hard abrasive pellets,the arrangement design of the two kind pellets was carried out.The designed combined hard abrasive pellets and soft abrasive pellets lapping plate was prepared,and the lapping experiment of sapphire was carried out.The main contents and conclusions of this paper are as follows:（1）Based on the scratch test analysis,among the four soft abrasives of cerium oxide,magnesium oxide,chromium oxide and silicon dioxide,silicon dioxide is more conducive to the solid-phase reaction of sapphire.When the particle size of the silica abrasive is 10μm,the abrasive concentration is 60 wt%,the catalyst B₂O₃addition amount is 2 wt%,the load is 0.4 MPa,and the rotation speed is 50 r/min,the solid-phase reaction efficiency of sapphire better;（2）Based on the particle size and concentration of hard abrasive and soft abrasives,the matching analysis of consolidated soft abrasive tablets and consolidated hard abrasive tablets was carried out.Scratching tests of two kinds of fixed abrasive pellets with different quantity ratios were carried out,and it was found that the scratching effect was the best when the number ratio of the two types of pellets was 1:1;（3）The processing promotion effect of the mixed distribution and the combined distribution of the soft and hard abrasives was compared and analyzed,and the results showed that the effect of the two abrasives under the combined distribution was more compatible with the surface quality and processing efficiency,and the surface roughness reached 7 nm,PV value reaches 0.4μm,and the material removal rate increase rate reaches 47.2%,which is nearly twice the mixing distribution of soft and hard abrasives;（4）Based on the matching analysis of the pellets,the lapping plate of the fixed soft abrasive pellets and hard abrasive pellets arranged by the bionic sunflower seed structure was obtained.And the pellet diameter is 10 mm,the density parameter of the pellets is 6.7,the two kinds of pellets is divided and arranged along the bionic sunflower helical line step by step.In order to compare the processing performance,a fixed abrasives lapping plate with fixed soft abrasive pellets and fixed hard abrasive pellets and a fixed abrasives lapping plate with soft and hard abrasives mixed pellets were prepared at the same time;（5）Experiments were conducted to explore the processing performance of the two lapping plates.The results show that both of the two kind plates can improve the material removal rate and surface quality of the sapphire workpiece.The material removal rate of the lapping plate lapping plate with fixed soft abrasive pellets and fixed hard abrasive pellets reached 1.5μm/min,which was about 70%higher than that of the lapping plate with soft and hard abrasives mixed pellets.The surface roughness Ra and PV value of the workpiece after processing reached 7 nm and 1.02μm,respectively.The damaged depth of workpiece after processed is between 3μm and 7μm,which effectively combines processing efficiency and processing quality.