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Sapphire crystal with excellent properties is widely used as substrate materials for optoelectronics and microelectronics industries. Subsurface crack damage (SSD) will occur in the diamond wire saw slicing process of the sapphire wafer, which is related to the quality of the as-sawn wafer and the cost of subsequent processing. Therefore, rapid and effective detection of SSD is required in production. However, current detection methods are time-consuming and labor-intensive, thus requiring a fast, effective, and low-carbon evaluation method. In this paper, based on the current diamond wire saw slicing process parameters range of sapphire crystal in actual production, sawing experiments were carried out to study the surface and subsurface crack damage morphology characteristics, evolution law of surface roughness (Rz), and SSD. Furthermore, the mapping relationship between Rz and SSD was established by the numerical fitting method. The results show that, in the range of processing parameters for practical industrial applications, the surface of the as-sawn wafer was mainly formed by material brittleness removal, the subsurface presented a small number of micro-cracks and brittle fracture damage, and the median crack propagation direction was shifted. Within the range of process parameters used in this study, the maximum SSD value of the sapphire wafer is 20.07 µm, the minimum value is 11.67 µm, and the corresponding Rz values are 11.13 µm and 8.12 µm, respectively. Both SSD and Rz decreased with the increase in saw wire speed and the decrease in specimen feed speed. There is a nonlinear relationship of monotone increase between the two, which is SSD = 0.15Rz3 − 4.87Rz2 + 55.49Rz − 195.23. The research results can be used to evaluate SSD quickly and effectively by measuring as-sawn sapphire wafer Rz that can provide an experimental reference for wire-sliced SSD evaluation, wafer quality improvement, and processing parameter optimization. [ABSTRACT FROM AUTHOR]

The diamond wire sawing technology has been widely used in cutting sapphire crystal, and the surface roughness and morphology of as-sawn sapphire wafers are important indexes of the cutting quality. With the development of diamond wire saw cutting technology to high wire speed, this paper conducted diamond wire sawing sapphire crystal experiments within the industrial high saw wire speed of 1000–1600 m/min, and the effect of cutting parameters on the as-sawn wafers surface roughness and morphology was analyzed. Furthermore, a diamond wire saw cutting numerical calculation model was established based on the wire sawing mechanism and sapphire crystal material removal mechanism, and the model was verified by sawing experiments. The influences of abrasive density and size on the surface roughness of the as-sawn wafers were predicted using the sawing model which provides a theoretical reference for the rationally adopting saw wire parameters to improve the cutting quality of sapphire crystal under industrial cutting parameters. The results show that within the range of parameters studied in this paper, the sapphire crystal material is mainly removed in brittle mode. Increasing saw wire speed from 1000 to 1400 m/min and decreasing specimen feed speed from 0.5 to 0.05 mm/min, increasing the abrasive density, and decreasing the abrasive size are all beneficial to decrease the as-sawn wafers surface roughness. Increasing the saw wire speed and decreasing the feed speed are beneficial to reduce the number of brittle pits and saw marks, the period of waviness on the as-sawn wafer surface, and improve the as-sawn wafer surface morphology. [ABSTRACT FROM AUTHOR]

Diamond wire sawing has been developed to reduce the cutting loss when cutting silicon wafers from ingots. The surface of silicon solar cells must be flawless in order to achieve the highest possible efficiency. However, the surface is damaged during sawing. The extent of the damage depends primarily on the material removal mode. Under certain conditions, the generally brittle material can be machined in ductile mode, whereby considerably fewer cracks occur in the surface than with brittle material removal. In the presented paper, a numerical model is developed in order to support the optimisation of the machining process regarding the transition between ductile and brittle material removal. The simulations are performed with an GPU-accelerated in-house developed code using mesh-free methods which easily handle large deformations while classic methods like FEM would require intensive remeshing. The Johnson-Cook flow stress model is implemented and used to evaluate the applicability of a model for ductile material behaviour in the transition zone between ductile and brittle removal mode. The simulation results are compared with results obtained from single grain scratch experiments using a real, non-idealised grain geometry as present in the diamond wire sawing process. [ABSTRACT FROM AUTHOR]

Due to their excellent physical and mechanical properties, third-generation super hard semiconductor materials (such as SiC, GaN) are widely used in the field of microelectronics. From the crystal bar to electronic devices, slicing is the first machining procedure that directly affects the subsequent process. Fixed diamond wire saw has been widely used in cutting hard and brittle materials. However, the diamond grits of wire saw are bonded through the binding agent's mechanical embedding that slicing super hard crystal is very difficult and inefficient. In order to improve the slicing efficiency, it is necessary to improve the holding strength and wear resistance of the diamond wire saw. The electro-spark deposition (ESD) process can form metallurgical bonding between metal materials at low heat input. The holding strength and wear resistance of the diamond wire saw can be effectively improved. In this paper, the mechanism of the manufacturing process of ESD diamond wire saw (ESDDWS) is introduced, and the conditions of the manufacturing process of ESDDWS are put forward. A model of the surface heat source of saw wire is established considering the wire shape. The transient thermal analysis of the single discharge of ESDDWS is carried out in ANSYS, and the effect of material compaction on material physical properties is considered. According to the simulation results, the parameter range of the manufacturing process of ESDDWS is predicted. The predictions agreed with experiment observation. [ABSTRACT FROM AUTHOR]

KDP crystal is an important functional crystal material used in the fields of laser frequency conversion. Slicing is the first process of KDP crystal processing and the KDP crystal is usually sliced by the diamond wire saw. As KDP crystal is an anisotropic material, the properties of KDP contact with different diamond grits on the diamond wire saw during slicing would be different. The anisotropic properties may lead to the deviation of the diamond wire saw in the thickness direction and form the surface shape deviation of slice. The surface shape deviation would affect the amount of material to be removed and the accuracy of crystal positioning. The commonly used crystal planes of KDP crystal are the (001), the double-frequency, and the triple-frequency crystal plane. In this paper, a model of diamond wire saw considering the anisotropy of KDP crystal is established to obtain the sawing forces, while the anisotropic properties of KDP crystal used in slicing are obtained through coordinate changes. The obtained sawing forces are then applied to the diamond wire saw to obtain the surface shape deviation. Besides, the influence of the tension force on the surface shape deviation is also considered. Based on the established model, the variation rule of surface shape deviation with the feed angle of diamond wire saw is obtained. Results in this paper can reduce the surface shape deviation of slice caused by the anisotropic properties of KDP crystal. [ABSTRACT FROM AUTHOR]

Slicing is the initial procedure in silicon wafer manufacturing process. The cost of slicing process is about 30% of the total cost of chip fabrication. The effective approaches to decrease slicing cost are to reduce the slicing kerf loss and to decrease the thickness and breakage ratio of sliced wafer. The resin-bonded diamond wire saw has the advantages of uniform of abrasive protrusion height and the manufacturing process less impact on the core wire strength. It is expected to achieve a narrow kerf and ultra-thin wafer slicing of silicon crystal ingot with resin-bonded diamond wire saw. The aim of this paper is to develop high-performance resin-bonded diamond wire saw. Based on the analysis of fabrication process of resin bond diamond wire saw, the device for resin-bonded diamond wire saw manufacturing is developed. The mold in the fabrication device ensures the consistency of the wire saw outer diameter and the uniform of abrasive protrusion height. A test device for constant force feed slicing is developed for the slicing performance evaluation of resin-bonded diamond wire saw. The components of the coating layer materials of resin-bonded diamond wire saw are investigated via orthogonal test. Choosing the material removal rate, wire saw wear rate, coating layer binding force, and sliced surface roughness as evaluation indexes, the performance of developed resin-bonded diamond wire saw is evaluated. The optimal component ratio of the coating layer materials of resin-bonded diamond wire saw is obtained, and the verification test of the optimal component ratio of the coating layer materials is performed. The results of this paper are useful for the development of smaller-diameter diamond wire saw and high-quality slicing of optoelectronic crystal ingot. [ABSTRACT FROM AUTHOR]

In this study, the variation in diamond wire tension during the reciprocating wire-winding machining process is investigated to improve the cutting stability and machining precision of a reciprocating winding diamond wire saw. Furthermore, the main causes of wire tension variation are analyzed, a tension control method using a PI (proportional-integral) regulator is proposed, and a wire tension detection and control mechanism is developed to solve the problem of tension variation during the machining process. The performance of this mechanism is verified through experiments, in which polycrystalline silicon materials are cut. Experimental results show that the designed mechanism can effectively mitigate tension instability during the reciprocating wire-winding machining process, control the wire tension fluctuation within 0.6 N, and significantly improve cutting efficiency, cutting surface roughness, and machining dimension accuracy. [ABSTRACT FROM AUTHOR]

Wire deflection affects the shape precision of workpiece during the profile cutting process with diamond wire saw. This study proposes a method for solving this problem using wire deflection detection, called light projection method. This method is based on the space position of the diamond wire. This research also analyzes the effects of wire deflection on shape precision, develops a detection and control device that allows feedback control according to the change in wire projection position, judges the wire position change, and uses this device to perform validation tests with polycrystalline silicon materials. The test shows that this detection and controlling device can effectively control the wire deflection phenomenon in the process of diamond wire cutting process. The roundness of a polysilicon with 20 mm thickness and φ20 mm diameter can be controlled within 0.05 mm, enabling significant improvement in the cutting shape precision and cutting stability. [ABSTRACT FROM AUTHOR]