Study On High-Efficiency Precision Lapping Of Lithium Tantalite With Fixed-Abrasive Pad

Lithium tantalate(Li Ta O3,hereinafter referred to as LT)is a typical soft and brittle multifunctional crystal material.Because of its unique physical characteristics,such as piezoelectric,pyroelectric,ferroelectric,acousto-optic,and electro-optical effects,it has received extensive attention in the field of aviation,aerospace and commercial optoelectronic products.However,the low hardness and high brittleness of the LT crystals,the wafer is prone to problems such as fracture,cracks,and embedded abrasive particles during the traditional free abrasive processing,which results in relatively low processing efficiency.This paper proposes to use a new type of self-made fixed-abrasive pad to lapping the LT wafers.The mainly research work includes the following aspects:(1)Study on Mechanical Properties of Y-42 ° Lithium Tantalate CrystalThe nano-indentation technology was used to analyze the load-displacement curve of lithium tantalate crystal under variable load.The hardness and elastic modulus of the material were measured,and its nano-mechanical properties,elastoplastic deformation,and room temperature creep behavior were studied.The hardness and the elastic modulus of the Y-42° LT crystal measured by nano-indentation is 12.6 GPa and 235.8 GPa,respectively.With the increase of the indentation load,they all show a significant "size effect".Under the variable load test of three sizes of spherical indenters,the Pop-in phenomenon occurred,that is,the elastic deformation changed to the plastic deformation.(2)The preparation of fixed-abrasive padResearched the design criteria and process route of the fixed-abrasive pad,selected different kinds of abrasives and additives to make abrasive tools;Analyzed the formula design,manufacturing process and dressing process of the fixed-abrasive pad;Designed a fixed lapping pad with high processing efficiency and good quality;The physical characteristics of the fabricated abrasive pads were detected and analyzed,and the dressing process was performed.(3)Lapping lithium tantalite wafer by using fixed-abrasive padThe single-factor experimental method was used to analyze the effect of abrasive type and particle size on the surface roughness and material removal rate of lithium tantalate crystals.The results show that diamond abrasive particles are better than silicon dioxide abrasives in lapping process of lithium tantalate wafers.At the same time,with the size of the abrasive grains decreases,the quality of the processed surface improves,but the material removal rate decreases.Comparative study of free abrasive and fixed abrasive lapping of lithium tantalate wafers to reference the differences in surface morphology,surface roughness,and material removal rate.The results show that lapping effect of fixed abrasives is better than that of free abrasives.(4)Effect of physical properties on processing of lithium tantalate crystalsThe effects of the physical properties of lithium tantalate in the processing process were analyzed theoretically to reveal the damage mechanism of the LT materials,and propose an efficient and ultra-precision machining method based on the "coercive effect",which attempts to suppress the piezoelectric and thermoelectric effects of lithium tantalate with reverse thermal and electric fields,and then prevent cracks and propagation caused by polarization and thermal expansion-induced internal stress,improve processing yield,and provide a new direction for obtaining efficient,high-quality,and low-cost processing methods.Finally,the key process parameters were optimized through orthogonal experiments.The final surface roughness was about 30 nm and the material removal rate was about 64.34 ?m / h.