Experimental Study On Diamond Wheel Grinding Process Of Sapphire Wafer

Sapphire(α-Al2O3) is a typical hard and brittle material.As an excellent substrate material,sapphire has excellent physical properties and chemical properties such as high hardness,high melting point,good light transmission,and stable chemical properties.Sapphire is widely used in various electronic devices such as IC chips and substrate materials.Among them,the sapphire substrate thinning process is one of the key processes in the LED chip manufacturing process.In order to avoid damage in thinning,it is required to reduce the roughness of the machining surface and the residual stress of the surface layer as far as possible,and to reduce the wafer warping deformation.In this paper,the influence of relative technological parameters in grinding process is studied.In order to study the influence of grinding wheel wear and grinding process parameters on the machining surface of sapphire wafer in the grinding process,the grinding method of rotary table was adopted to study the grinding process with sapphire surface roughness Ra,surface morphology and warping degree as evaluation indexes.Firstly,the resin bonded diamond grinding wheel was developed,and 200#resin bonded diamond grinding wheel was developed by hot pressing process.Sapphire was ground and diamond particles in the grinding wheel morphology and fixed area were observed online,it is found that the main wear forms of resin diamond grinding wheel in grinding sapphire are:abrasion wear,abrasive particle breaking,abrasive particle falling off,adhesion wear and abrasion wear.All kinds of wear forms exist in the early wear stage,the stable wear stage and the rapid wear stage of the grinding wheel,but the abrasive particle breakage is obvious in the early wear stage,and the abrasive particle shedding and adhesion wear account for 45%in the later wear stage.The stable loss rate of grinding wheel is 0.0273mm~3/s,the wear ratio is 17.37,and the minimum roughness of sapphire can reach Ra0.260μm.The wear mechanism of grinding wheel and its influence on sapphire surface quality were analyzed.Secondly,the grinding process of sapphire wafer with ceramic bond grinding wheel was studied experimentally.It is found that the wear forms of ceramic bond diamond are:abrasion wear,abrasive particle shedding and pore filling.The wear process is divided into fast wear stage and steady wear stage,and the grinding wheel has better self-sharpness,With the increase of workpiece removal amount,grinding wheel wear amount and sapphire removal rate tend to be stable from high to stable,sapphire grinding surface roughness Ra shows a trend of increasing first and then decreasing to stable,sapphire wafer minimum roughness can reach Ra0.378μm,higher than that of resin bonded grinding wheel.Than,the sapphire thinning and grinding process was studied.Through single-factor experiments and orthogonal experiments,the effects of different wheel sizes,wheel binder types,spindle feed speed,workpiece speed,and wheel speed on the sapphire grinding effect were studied.The optimized process for sapphire grinding was obtained as follows:feed rate:0.1μm/s,wheel speed:1200r/min,workpiece speed:300r/min,and light grinding time:30s.Grinding sapphire under optimized process parameters can obtain a ground surface with a surface roughness of Ra0.290μm.Finally,the deformation of the sapphire after grinding was studied,and the effect of each processing parameter on the warpage of the sapphire after grinding was studied by single-factor experiments using warpage as an evaluation index.After the optimized process thinned the sapphire by 100μm,the warpage of the sapphire was 0.183mm.Finally,from the Angle of grinding residual stress,the deformation mechanism and control of lamborrine wafer thinning grinding were analyzed.