Wire Sawing Research Articles

Experimental investigation on diamond wire sawing of Si3N4 ceramics considering the evolution of wire cutting performance

When diamond wire saw is used in machining silicon nitride ceramics (Si3N4 ceramics), the ultra-hardness of Si3N4 causes the saw wire to wear out, which leads to the saw wire cutting performance constantly changing during its life cycle, and thus the machined quality of Si3N4 ceramics is affected. Surface roughness and topography are important indicators of the quality of the machined surface. In this paper, the diamond wire saw cutting experiment of Si3N4 ceramics was carried out, the effect of the evolution of saw wire cutting performance on the surface roughness and topography of Si3N4 ceramics as-sawn slices was investigated based on the analysis of the changes of saw wire wear topography, breaking force, bow angle and kerf loss during the sawing process. The results show that the surface roughness along the saw wire motion direction and the workpiece feed direction tends to decrease and then increase with the evolution of the cutting performance of the saw wire, which accords well with the trend of the as-sawn slices surface morphology. The results of the study can provide experimental reference for the development of high precision diamond wire saw cutting technology for Si3N4 ceramics.

Theoretical study on sawing force of ultrasonic vibration assisted diamond wire sawing (UAWS) based on abrasives wear

Wire saw cutting of monocrystalline silicon plays an important role in semiconductor manufacturing. The study of wire saw cutting silicon is important, and the grain wear has a great effect on the saw cutting force. Therefore, in this paper, considering abrasive wear on the wire saw, the ultrasonic vibration assisted sawing force theoretical model from a single abrasive to multiple abrasives is established. With the application of equal probability method, the surface profile model of wire saw is established. According to the abrasive wear law of wire saw, the finite element model (FEM) of wire saw with different abrasive wear is established. The influence of different abrasive wear on sawing force and workpiece surface morphology is analyzed by Abaqus. Finally, the experimental verification is carried out. The experimental results show that the sawing force of the ultrasonic vibration assisted diamond wire sawing (UAWS) decreases by 38% on average than that of the conventional diamond wire sawing (CWS), the surface roughness value is reduced, and the surface morphology is improved. With the increase of the abrasive wear value, the sawing force and the numbers of pits firstly decrease and then increase, the surface roughness value distribution firstly concentrates and then disperses, and the scratches show a smooth to intermittent trend.

Material-related fundamentals of cutting techniques for GaAs wafer manufacturing

Abstract Driven by the requirement of high cutting efficiency and improvement of wafer flatness, wire sawing of GaAs single crystals under brittle material removal conditions has been studied. Crack nucleation and crack propagation were investigated by indentation and scratching tests on polished {100}-oriented semi-insulating GaAs wafers. Based on these results a concept has been developed that allows to control the force balance in the cutting slits so that the deflection of the wires perpendicular to the cutting planes is minimal resulting in cuts of high flatness. The concept has been successfully introduced in mass production of GaAs wafers.

Influence of single diamond wire sawing of photovoltaic monocrystalline silicon on the feed force, surface roughness and micro-crack depth

To gain an in-depth understanding of the influence of diamond wire sawing of monocrystalline silicon on the feed force and wafer quality, experiments with a single diamond wire in the form of a loop were performed. The cutting parameters of wire cutting speed, feed rate and wire tension were varied. The feed force was monitored and surface roughness of the specimen was measured. The micro-crack depth was determined using an image processing. The results show that cutting conditions of higher feed rate and higher wire tension increased the feed force by 78% and 20%, respectively, since for chip removal these conditions is required a higher force per grain. On increasing the wire cutting speed, the feed force reduced by 66% due to a decrease in penetration depth of the grains. Based on an analytical model, it was evidenced that volume of material removed per wire length has a significant effect on feed force. The variation of the feed rate and wire cutting speed had a greater effect on surface roughness Ra and Rq, with a minor effect on Rz. With a higher feed rate the micro-crack depth increased, whereas it was reduced on increasing the wire cutting speed. A strong correlation between sawn surface and subsurface damage was found, indicating that the micro-crack depth is around 1.37 times higher than Rz value. The combination of a lower feed rate and lower wire tension with higher wire cutting speed resulted in lower feed force, smoother surface and shallower micro-crack depth.

Effect of Additives on Making Texture Surface on Multicrystalline Silicon Wafer by Diamond Wire Sawing

Effect of Additives on Making Texture Surface on Multicrystalline Silicon Wafer by Diamond Wire Sawing

Surface properties of diamond wire sawn photovoltaic mc-Si wafers by stirred slurry pretreated and additive-free acid textured

Diamond wire saw cutting multi-crystalline silicon (mc-Si) wafers has the advantage of high cutting rate. However, it is difficult to follow the current additive-free wet acid etching process to prepare the anti-reflective textured surface due to the obvious saw marks on the surface of the as-sawn wafer. In response to this problem, this paper proposes a turbine-type stirred slurry pretreatment process to modify the surface of mc-Si wafers cut by diamond wire to make it suitable for the subsequent conventional wet acid texturing process. The experimental results show that the consistency of the surface structure of the mc-Si wafers can be effectively improved after turbine-type stirred slurry pretreatment by choosing suitable process parameters. The reflectivity of the pretreated mc-Si wafers after acid texturing is greatly reduced compared with that before processing, which can meet the production requirements of solar photovoltaic cells. Furthermore, based on ANSYS Workbench and Fluent, numerical simulation of the surface pretreatment process of large-size silicon wafers in practical industrial applications was carried out, and the uniformity of the surface modification treatment was analyzed. The research results provide ideas for promoting the adaptation of the diamond wire sawing of mc-Si silicon wafers to the acid wet texturing technology.

Simulation analysis of cutting coolant flow field in fixed and free abrasive combined wire sawing polysilicon

Simulation analysis of cutting coolant flow field in fixed and free abrasive combined wire sawing polysilicon

Wet sandblasting pretreatment of diamond wire sawn multi-crystalline silicon wafer for surface acid texturization in photovoltaics

Wet sandblasting pretreatment of diamond wire sawn multi-crystalline silicon wafer for surface acid texturization in photovoltaics

An Analysis of the Formation Mechanisms of Abrasive Particles and Their Effects on Cutting Efficiency

Magnetic induction-free abrasive wire sawing (MIFAWS) is a method that combines magnetic fields with traditional free abrasive wire sawing technologies. Magnetic abrasive particles (MAPs) are attracted on a magnetized wire, thus leading to an increase in their number into the cutting zone. The number of instantaneous-effective abrasive particles (IEAPs) adsorbed on the wire surface has a great influence on the cutting efficiency of the saw wire. In this study, a mathematic model of the movement of the MAP is presented, and the factors influencing the IEAPs number, including slurry-supply speed and slurry dynamic viscosity, are investigated both by means of simulation analysis and experiments. The results indicate that the number of IEAPs decreases with an increase in the slurry supply speed. The cutting efficiency increases gradually with the increase of slurry supply speed, but the growth rate of wire saw cutting efficiency slows down when the slurry supply speed exceeds a given threshold. The number of IEAPs adsorbed by saw wire increases with a decrease in the dynamic viscosity of the cutting fluid, while the cutting efficiency first increases and then decreases. The cutting efficiency attains its highest value when the dynamic viscosity of the cutting fluid is 0.0047 Pa⋅s. The experimental results agree with the simulation results, and provide some guidance for the practical application of the MIFAWS process.

Composition and Structural Identification of Silicon Particles in Diamond Wire Saw Silicon Powder

Composition and Structural Identification of Silicon Particles in Diamond Wire Saw Silicon Powder

Machinability improvement in three-dimensional (3D) ultrasonic vibration assisted diamond wire sawing of SiC

Ultrasonic vibration assisted (UVA) cutting has been proven to be an effective method for improving machining behavior in processing hard and brittle materials. However, there is no investigation on three-dimensional (3D) UVA diamond wire sawing (DWS). In this paper, a novel 3D vibration assisted DWS system is developed. A theoretical model is established for predicating sawing forces. Experiments have been carried out on DWS of silicon carbide (SiC) ceramics. The effects of ultrasonic vibration assistance, input vibration direction and cutting parameters on sawing forces, surface morphologies and tool wear are studied respectively. The simulation results indicate that elliptical motion in 3D space can be obtained for the diamond abrasive. The experimental results reveal that the proposed model has sufficient accuracy to predict sawing forces. It is demonstrated that sawing forces can be reduced by ultrasonic vibration assistance either in vertical direction or in longitudinal direction. However, 3D ultrasonic vibration condition provides the lowest sawing force because of the combined advantages. Due to intermittent cutting mode, sawing forces are decreased by 31%, 40% and 29.8% in X, Y and Z direction, respectively. Because debris can be removed more easily from the contact surface and large ductile smooth area can be obtained, 3D ultrasonic vibration assistance generates higher surface integrity than that of traditional sawing process. Moreover, the wear of diamond wire saw can be effectively decreased.

Action mechanism of liquid bridge between electroplated diamond wires for ultrathin wafer slicing

Ultrathin wafer slicing with low kerf loss for electroplated diamond wire sawing is the primary means to improve the productivity in wafering and reduce the manufacturing costs in the photovoltaic industry. Nevertheless, the reduction of the diameter and spacing of the diamond wires makes the liquid bridge action between them significant, which will affect the slicing process. Therefore, based on the principle of minimum potential energy, an analytic model of adhesion caused by the liquid bridge between the diamond wires with protruding abrasives is established in this paper. The variation of the adhesion length with initial wire web gap, wire span, and wire tension as well as wire diameter is analyzed. The results show that the adhesion length was increased with the increase of the wire diameter. The reduction of the initial wire web gap would increase the adhesion length, that was, the limitation of the liquid bridge on the thinner wafers sawing was more obvious. The adhesion length was decreased with the decrease of the wire span or the increase of the wire tension. So it is effective to weaken the limitation of the liquid bridge on the wafers slicing by reducing the wire span or enhancing the wire strength. Then, an experiment on the action of the liquid bridge between the diamond wires was carried out. The theoretical results were in accord with the experimental ones well, and the maximum error was 8.27%. The research work is of great significance to further reduce kerf loss and wafer slicing thickness.

Surface formation, morphology, integrity and wire marks in diamond wire slicing of mono-crystalline silicon in the photovoltaic industry

The diamond wire sawing is superior for the wafers manufacturing in the photovoltaic and semiconductor industry. In this research, analytical models were emphasized and experiments were designed to describe the surface formation, wire marks formation and crack generation in diamond wire sawing (DWS). It was found that wire marks are mainly caused by the wire bow and the wire lateral motion. The width of the wire marks are alternately difference due to the reciprocating sawing and wire bow. The twisting effect of wire was introduced as a composition of surface formation. Chips are removed by abrasive grains, and residual material left forms sawn surface. Surface roughness was investigated regarding the combination of wire marks and sawn surface. It was found that roughness changes with the feeding position and wire motion. Wire number that forming the wire web has influence on the sawing quality. It was found that increasing of wire number was useful for improving roughness as the stiffness of wire web is enhanced. The wafer surface was observed by Scanning Electron Microscope (SEM) and 3D profiler to analysis the geometric characteristics of wire mark and wafer deformation. It was found the wire mark in the contact zone was related to the sawing direction and action force. Furthermore, the surface defects was analyzed on the aspect of bearing rate. Wafer surface profile of long-term deformation after stress relief was observed.

A novel tool monitoring approach for diamond wire sawing

Mobile diamond wire sawing is a highly flexible, productive and, versatile cutting process. Accordingly, it is used in many areas, such as the dismantling of nuclear power plants or wind turbines. Despite the widespread use of the process, the cutting process requires continuous manual monitoring by the machine operator. This is due to the continuously changing cutting conditions. A common process error is tool breakage. It is often caused by the displacement of the grinding segments (cutting beads). Due to the cutting speed (up to 30 m/s), these failures cannot be detected and prevented by the machine operator. However, a measuring system or process monitoring does not exist yet. Accordingly, a damaged diamond wire can become hooked, which often results in wire breaks. As a result, grinding segments break away from the wire, which can lead to deadly accidents. Therefore, a new approach for monitoring the tool for diamond wire grinding will be investigated. The paper is divided into five sections. First, the requirements for the sensor system are derived. After the selection of a measuring principle and the functional verification in the grinding process, the monitoring approach is presented and features for monitoring the tool with regard to the displacement of grinding segments are described. It was shown that the developed approach is suitable for monitoring the diamond wire tool during the sawing process. The investigation on a prepared diamond wire tool also demonstrated that the feature allows the detection of displacing grinding segments already from 2 mm.

Analysis of sawing characteristics of fine diamond wire slicing multicrystalline silicon

At present, the diamond wire sawing technology has been widely used in the slicing of photovoltaic multi-crystal silicon (mc-Si). The diameter of diamond saw wire becomes smaller and smaller, and the surface abrasive density and sawing process parameters affect the sawing characteristics of mc-Si wafer. In this paper, the sawing experiment of photovoltaic mc-Si with fine diameter electroplated diamond saw wire was carried out, and the effects of abrasive density and sawing process parameters on the sawing characteristics were analyzed. The results show that the cutting ability and sawing efficiency of diamond wire increase with the increase of surface abrasive density. However, too large surface abrasive density is easy to cause the accumulation of abrasives and the reduction of chip holding space. The core wire diameter is 60 μm and the surface fixed abrasives size is 8–10 μm, when the surface abrasive density is 200–300 grit/mm, the saw wire has relatively good sawing characteristics. The area formed by the material ductile removal domain accounts for a large proportion of the sawn surface, and the surface roughness and subsurface microcrack damage depth (SSD) of silicon wafer are lower. The surface quality of as-sawn wafer can be improved by decreasing the feed speed of workpiece and increasing the wire speed. The research results can provide a reference for the optimization of diamond wire sawing process of photovoltaic mc-Si cells.

Influence of the Agitation Pipe on the Flow Field of Electroplating Tank in the Electroplated Diamond Wire Saw

In order to solve the problem of diamonds sedimentation in electroplating tank and uneven distribution of diamonds in coatings, the fluid flow in the electroplating tank formed by three structure kinds of agitation pipe was compared and analysed. Results showed that the middle inlet type agitation pipe can significantly improve the fluid uniformity in the electroplating tank, and setting sand blasting ports at both ends of the agitation pipe can avoid the formation of fluid “dead zone”. Along the direction of the agitation pipe, the middle inlet type agitation pipe improves the overall flow of the fluid. In the position of the wire saw passing through, the difference of the speed in the electroplating tank of the middle inlet type is 47.17% and 15.25%, which is significantly lower than that of the water inlet structure of one end by 134.48%. As a result, it can significantly improve the plating effect of the wire saw.

Fluid Flow Analysis of Agitation Pipe in the Electroplated Diamond Wire Saw

Agitation pipe is the important part of the electroplated diamond wire saw in the suspension sanding process. The structure type and the sandblasting configuration in agitation pipe play a role on the flow uniformity. Fluid flow in the different structure forms of agitating pipe was studied and the influence of sandblasting angle and the diameter was also contrasted. Results found that the central water type of agitation pipe has the better performance, generating the flow field distribution in the middle part with high velocity and small velocity on both sides. The order of sandblasting in performance was 30°, 45° and 60°. The better flow uniformity occurred in the configuration of sandblasting with the diameter 7.5 mm, 7 mm and 7.5 mm.

Study on the subsurface damage depth of monocrystalline silicon in ultrasonic vibration assisted diamond wire sawing

Diamond wire sawing is one of the key technologies in solar cell manufacturing process and semiconductor chip manufacturing process. The subsurface damage depth (SSD) affects the quality of machined surface in diamond wire sawing, which must be evaluated. In this paper, a mathematical model of the SSD in monocrystalline silicon wafers induced by ultrasonic vibration assisted diamond wire sawing (UAWS) was proposed. In this model, the input is the depth and deflection angle of the median crack, the depth and length of the lateral crack, and ultrasonic vibration, and the output is the residual SSD on the chip. According to the model, the variation of SSD with position angle of diamond abrasives under ultrasonic vibration was analyzed on the cross section of wire saw, and the influence of shielding effect about median crack on SSD under ultrasonic vibration was analyzed later. Then, a finite element model (FEM) of diamond wire sawing monocrystalline silicon was established by ABAQUS,and the SSD under different slicing parameters was simulated. Finally, the interface bonding method was used to measure the SSD of monocrystalline silicon wafer. The experimental results showed that the SSD increases with the increase of the wire saw feed rate, and decreases with the increase of the wire saw speed and the workpiece rotation speed. The SSD in wafer sliced by UAWS is 18.95% on average lower than that in wafer sliced by conventional wire sawing (CWS). The maximum error between theoretical of mathematical model and experimental values is 15.9%, which verifies the validity of the mathematical model.

Research on suppressing brittle fracture and implementing ductile mode cutting for improving surface quality at silicon wafers manufacturing

Single crystal silicon is an important basic material used to manufacture electronic and photovoltaic devices. Ductile mode of diamond wire sawing is a promising method for silicon wafering in order to produce wafers with minimal surface damage. To achieve ductile mode, the correct applying of cutting parameters and careful wire design is necessary. This study investigates the scratching of monocrystalline silicon by the abrasive particles of different geometry, which simulates the material removal process in diamond wire sawing. Diamonds, crushed and spherical tungsten carbide (WC) particles served as abrasives. Experiments show that spherical abrasives enhance ductile mode cutting significantly decreasing brittle damage when compared to irregular shape particles. Spherical WC particles permit to increase the critical load and critical cut depth of ductile-to-brittle transition from 5 to 10 times. The depth of the damaged subsurface layer decreased from 5 µm to 0.2 µm due to the absence of brittle cracks. A uniform regular distribution and appropriate suitable density of abrasive particles is obligatory for cracking reduction. For that, the method of diamond particles uniform deposition with the controlled density by a polymer binder combining high modulus and adhesive capacity with good flexibility was elaborated. The method includes preliminary diamond particles fixation on a thin resin layer providing high uniformity and subsequent strong fixation by a thicker resin layer. The research on ovalization of diamond particles was performed for smoothening cutting edges. The method is based on the activation of the graphitization process at sharp edges of particles under the action of metal salts at increased temperatures.

An on-line inspection method for abrasive distribution uniformity of electroplated diamond wire saw

Electroplated diamond wire saws are widely used in the field of slicing hard and brittle materials. The slicing quality and efficiency are directly affected by the abrasive distribution uniformity of the wire saw. At present, the abrasive distribution uniformity can only be qualitatively analyzed manually. In this paper, the expanded circumferential surface image of the wire saw is obtained by the method of cylindrical unwrapping and image stitching. Then the image is segmented by the Voronoi diagram. On this basis, the quantitative characterization and the online inspection method of the abrasive distribution uniformity are proposed. Finally, the real-time performance of the method is tested through experiments. The results show that under the hardware environment of this paper, this method takes 0.156 s to detect a sampling point, which meets the online detection requirements of the wire saw.