硅晶圆磨削减薄工艺的磨削力模型

硅晶圆磨削减薄是一种有别于传统磨削的材料加工方式。磨削减薄过程中,硅晶圆和砂轮同时绕旋转轴旋转,砂轮沿垂直方向连续进给去除材料,其中磨削力是磨削质量的决定性因素。目前,尚缺少一个用于硅晶圆磨削减薄工艺的磨削力预测模型。为了得到磨削力模型,分析了磨削减薄过程中的硅晶圆材料去除机理,将磨削力分为摩擦力和切屑力,考虑了磨粒运动轨迹,分别计算了单颗磨粒在法向和切向上的摩擦力和切屑力,最后基于有效磨粒总数建立了总磨削力模型。模型综合考虑了磨削参数、砂轮和硅晶圆的几何参数和材料性质对磨削力的影响。讨论了砂轮进给速度、晶圆转速和砂轮转速三个主要磨削参数对磨削力的影响,讨论了硅晶圆上晶向对磨削力的影响,给出了磨削力在硅晶圆面上沿径向的分布情况。     

Sensitivity analysis of the surface integrity of monocrystalline silicon to grinding speed with same grain depth-of-cut

Mechanisms for removal of materials during the grinding process of monocrystalline silicon have been extensively studied in the past several decades. However, debates over whether the cutting speed significantly affects the surface integrity are ongoing. To address this debate, this study comprehensively investigates the effects of cutting speed on surface roughness, subsurface damage, residual stress, and grinding force for a constant grain depth-of-cut. The results illustrate that the changes in the surface roughness and subsurface damage relative to the grinding speed are less obvious when the material is removed in ductile-mode as opposed to in the brittle-ductile mixed mode. A notable finding is that there is no positive correlation between grinding force and surface integrity. The results of this study could be useful for further investigations on fundamental and technical analysis of the precision grinding of brittle materials.The full text can be downloaded at https://link.springer.com/content/pdf/10.1007%2Fs40436-020-00291-5.pdf     

An experimental study on grinding of Zr-based bulk metallic glass

There are limited studies in the literature about machinability of bulk metallic glass(BMG).As a novel and promising structural material,BMG material machining characteristics need to be verified before its utilization.In this paper,the effects of cutting speed,feed rate,depth of cut,abrasive particle size/type on the BMG grinding in dry conditions were experimentally investigated.The experimental evaluations were carried out using cubic boron nitride(CBN) and Al_2O_3 cup wheel grinding tools.The parameters were evaluated along with the results of cutting force,temperature and surface roughness measurements,X-ray,scanning electron microscope(SEM)and surface roughness analyse.The results demonstrated that the grinding forces reduced with the increasing cutting speed as specific grinding energy increased.The effect of feed rate was opposite to the cutting speed effect,and increasing feed rate caused higher grinding forces and substantially lower specific energy.Some voids like cracks parallel to the grinding direction were observed at the edge of the grinding tracks.The present investigations on ground surface and grinding chips morphologies showed that material removal and surface formation of the BMG were mainly due to the ductile chip formation and ploughing as well as brittle fracture of some particles from the edge of the tracks.The roughness values obtained with the CBN wheels were found to be acceptable for the grinding operation of the structural materials and were in the range of 0.34-0.58 μm.This study also demonstrates that conventional Al_2O_3 wheel is not suitable for grinding of the BMG in dry conditions.     

An investigation on machined surface quality and tool wear during creep feed grinding of powder metallurgy nickel-based superalloy FGH96 with alumina abrasive wheels

In this study, the machined surface quality of powder metallurgy nickel-based superalloy FGH96 (similar to Rene88DT) and the grinding characteristics of brown alumina (BA) and microcrystalline alumina (MA) abrasive wheels were comparatively analyzed during creep feed grinding. The influences of the grinding parameters (abrasive wheel speed, workpiece infeed speed, and depth of cut) on the grinding force, grinding temperature, surface roughness, surface morphology, tool wear, and grinding ratio were analyzed comprehensively. The experimental results showed that there was no significant difference in terms of the machined surface quality and grinding characteristics of FGH96 during grinding with the two types of abrasive wheels. This was mainly because the grinding advantages of the MA wheel were weakened for the difficult-to-cut FGH96 material. Moreover, both the BA and MA abrasive wheels exhibited severe tool wear in the form of wheel clogging and workpiece material adhesion. Finally, an analytical model for prediction of the grinding ratio was established by combining the tool wear volume, grinding force, and grinding length. The acceptable errors between the predicted and experimental grinding ratios (ranging from 0.6 to 1.8) were 7.56% and 6.31% for the BA and MA abrasive wheels, respectively. This model can be used to evaluate quantitatively the grinding performance of an alumina abrasive wheel, and is therefore helpful for optimizing the grinding parameters in the creep feed grinding process.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00305-2     

Continuous generating grinding method for beveloid gears and analysis of grinding characteristics

Continuous generating grinding has become an important gear processing method owing to its high efficiency and precision. In this study, an adaptive design model is proposed for the continuous generation of beveloid gears in common gear grinding machines. Based on this model, a method for determining the installation position and grinding kinematics is developed alongside an analytical meshing model for grinding contact trace and derivation of key grinding parameters. By combining these aspects, a general mathematical model for the continuous generation of beveloid gears is presented, comprising the entire grinding process from worm wheel dressing to the evaluation of grinding deviation. The effects of the worm and dressing wheel parameters on the grinding deviation were analysed, facilitating the development of an approach to improve the grinding accuracy. The presented procedure represents a novel design method for the continuous generation of beveloid gears in common gear grinding machines, facilitating the appropriate selection of worm and dressing wheel parameters.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00388-z     

An experimental investigation as to the effect of cutting parameters on roundness error and surface roughness in cylindrical grinding

This paper presents the results of an experimental investigation as to the effects of grinding parameters on roundness error and surface roughness in cylindrical grinding. Many variables including the wheel materials, wheel loading and dressing, workpiece metallurgy, work drive mechanisms, work holding methods, coolant types, feeds and speeds, machine stiffness and age, surface conditions, centre conditions, floor vibrations all influence the quality of ground parts. However, the composite sum of these grinding parameters creates static and dynamic forces. It is obvious that the roundness error and surface roughness are created by many parameters, but in this study, only the effects of the depth of cut, work speed and feed rate which create the grinding forces in cylindrical grinding are investigated. The grinding experiments were planned according to the principles of orthogonal arrays (OAs), developed by Taguchi, and were performed so as to understand the effects of these parameters on roundness error and surface roughness. The experimental data was analysed by using statistical tools: the percent contribution from an analysis of variance (ANOVA) and the correlation between machining parameters with roundness error (R) and also surface roughness (Ra). Roundness was found to be the most related with the cutting speed, grinding force and depth of cut, while surface roughness is related to feed rate and work speed.     

Study of chip strength due to backside grinding on wafer

Abstract

The strength distribution of semiconductor chips on a wafer was studied for this paper using the three‐point bending test method that complies with ASTM standard E855. It was found from thousands of testing results that a weak region in a wafer always exists when the wafer has been thinned by mechanical backside grinding method. This weak region was distributed in two sectorial regions 45 degrees wide and symmetric to the wafer center. The averaged chip strength in the weak region was found to be at least 30% lower than the averaged chip strength of the whole wafer, and was independent of chip aspect ratio, metallization, diameter of the wafer, and the equipment that the backside grinding process used. The existence of the weak region was due to the grinding mark produced by the equipment, and was physically explained by the experimental results in this study. This weak region was able to be eliminated by using either plasma etching or polishing after the mechanical backside grinding.     

Impact of dressing infeed on SiC wheel for grinding Ti-6Al-4V

Present experimental investigation is directed toward the optimization of dressing infeed for silicon carbide (SiC) wheel to be employed for grinding difficult-to-machine super alloy Ti-6Al-4V. Grinding wheels are dressed using separate, however, identical 0.75 carat single point diamond dressers at 5, 10, 15, 20 and 25 µm infeed values. Differently dressed wheels are consequently, applied for grinding Ti-6Al-4V under different infeed values of 5, 10 and 15 µm. All the operations have been performed at a constant velocity of 1810 m/min. The performances of the differently dressed SiC wheels are evaluated based on the variations of grinding force components, average surface roughness values, grinding ratio, chip forms and based on the analyses of the micrographs of wheel topologies and also of the ground surfaces, obtained using scanning electron microscope. Following the performance evaluation, the optimized dressing infeed has been found to be 20 µm for the operation range considered herein.     

Analysis of grinding kinetics in a laboratory ball mill using population-balance-model and discrete-element-method

Grinding processing consumes a lot of energy in mineral processing, but it is a low-efficiency process in which only approximately 1% of the total energy is used to reduce the actual particle size. Therefore, an efficient operation in the grinding process increases the competitiveness of the production and is an essential for enhancing the energy efficiency of the entire mineral processing procedure.Therefore, the study will focus on to finding a different method to predicting the particle size distribution of the ball mill, by using the PBM which reflects the actual size distributions of ground product and the DEM which can understand the internal particle behavior in the mill chamber. First, the grinding parameters were calculated by applying size distributions of ground product under various conditions to PBM and the behaviors of the particles inside the ball mill obtained through DEM were analyzed to predict the distribution of the impact energy used for grinding. Next, the relational expression between the grinding rate parameter and the normal force applied to the grinding materials was derived. Using the relational expression derived from this study, it was confirmed that the size distributions in other conditions can be predicted.     

工程陶瓷高效平面磨削表面波纹度试验研究

 以氧化铝和氧化锆两种工程陶瓷在高效磨削条件下的磨削振动和表面波纹度为研究对象,概述了磨削表面波纹度的定义和评价方法以及产生波纹度的原因,在超高速平面磨削实验台上进行磨削工艺试验,通过改变砂轮线速度、进给速度和磨削深度,分析了磨削参数对零件表面波纹度的影响。在试验研究的基础上,对磨削表面波纹度的影响因素和机理进行分析和讨论。试验结果表明,在陶瓷材料高效平面磨削中,砂轮线速度和进给速度是影响磨削颤振与表面波纹度的主导因素。在如120 m/s的较高砂轮线速度时,磨削过程振动主要是由强迫振动引起,工件表面质量好于低速情况。在保证较高磨削效率的前提下,陶瓷材料的高效磨削更适合在大切深和小进给速度条件下进行。     

Determination of grinding conditions for renewal of a wheel cutting ability allowing for its variation during the machining process

The authors discuss the determination of rigid-mode grinding conditions with a periodic electric discharge action on the wheel working surface in a separate zone, taking into account the in-process variation of the wheel cutting ability. The calculation is based on the mathematical relations that describe variation of the wheel cutting ability in elastic-mode infeed grinding with a constant workpiece-to-wheel pressing force, where the process kinematics is similar to that of the rigid-mode grinding. The workpiece speed is determined for a specified machined surface roughness. The workpiece-to-wheel pressing force is chosen such that the surface layer of the workpiece material should undergo no phase-structural transformations. The variations of the wheel cutting ability during the rigid-mode grinding are taken into account through the use of the equations that describe the variations of the wheel's current limited cutting ability in the elastic-mode grinding. Based on the discussion of various methods of calculation of one of the grinding parameters—depth of cut—the authors have found its value ensuring that no phase-structural transformations will occur in the surface layer of the workpiece material under maximum feasible removal rates.     

Increasing workpiece peripheral speed as a means for improving ergonomics of cylindrical up grinding with cubic boron nitride tools

The author pioneered in experimentally finding out that an increase in the workpiece peripheral speed proper in a wide range invariantly leads to a definitely better surface roughness, i.e., smaller thickness of cut, suggesting an improvement in the process ergonomics, in cylindrical centered up grinding under elastic attrition and linear wear conditions, with cubic boron nitride tools of various specifications, on the grinders differing in static stiffness (8.3 and 12.0 N/μm), with a wheel speed ranging from 32 to 91 m/s. A comparative assessment of grinding processes with a fixed and controllable levels of forced vibrations at idling speed has demonstrated that the weakening of the positive influence of the speed factor on the surface roughness and thickness of cut with increasing workpiece speed proper and/or wheel speed is due to the vibration-induced suppression—an increasing amplitude of the wheel-workpiece vibration displacements at rotational speeds of the wheel, workpiece, and other elements of the grinder-workpiece-tool system. Some recommendations are offered of how to improve the ergonomics of cylindrical up grinding with cBN tools by increasing the workpiece speed proper.     

Experimental investigations into electric discharge grinding and ultrasonic vibration-assisted electric discharge grinding of Inconel 601

The paper presents experimental investigations into electric discharge grinding (EDG) and ultrasonic vibration-assisted electric discharge grinding (UVAEDG) of Inconel 601. The process parameters selected for both processes were duty cycle, discharge current, pulse on time, grinding wheel speed, work speed, and speed ratio to study their influence on responses like surface roughness (R_a) and material removal rate (MRR). It was found that duty cycle, wheel speed, work speed, discharge current, speed ratio, and pulse duration significantly influenced MRR and R_a. It was inferred that MRR increased with increase in duty cycle, wheel speed, current, work speed, and pulse duration in both EDG and UVAEDG processes. It was also inferred that R_a increased with rise in duty factor, pulse on time, and discharge current in EDG and UVAEDG processes.     

The measurement and analysis of micro bonding force for electroplated CBN grinding wheels based on response surface methodology

The superabrasive (e.g. CBN or diamond) grain dislodgement occurrence on the wheel surface due to insufficient bonding force is the major failure phenomena in the grinding process with electroplated grinding tools. This failure leads to the abrupt increase of load on the immediate grains, accelerating more grain dislodgement on wheel surface. Ultimately, the aggregated grain dislodgement causes the workpiece profile accuracy degradation and catastrophic wheel sharpness loss. Therefore, the provision of sufficient and uniform micro bonding force all through the wheel surface is the critical task in electroplated superabrasive grinding wheel design. Considering the complexity in the micro bonding force enabling factors, e.g. the grain shape, dimensional size, spatial orientation, and bond layer thickness, it is vital to establish the quantitative and comprehensive relationship between these factors with the micro bonding force for optimal electroplated grinding wheel design. In this paper, an inclined micro-thread turning test is developed to measure the single grain micro bonding force. In addition, the finite element model of single CBN grain bonding force is established and validated to simulate the grain dislodgement. Finally, the response surface methodology (RSM) is applied to build the comprehensive correlation of the bonding force with its dimensional size, spatial orientation, and bond layer thickness. Therefore, the optimal bonding condition through regressed prediction model is identified to provide the quantitative basis for the electroplated CBN grinding wheels design, which indicates that the bonding force can be predicted for specific wheel manufacturing parameters and improved by related variable adjustment.     

2D-C/SiC高速深磨磨削特性及去除机制

采用树脂结合剂金刚石砂轮, 通过对2D-C/SiC复合材料高速深磨磨削加工, 并对磨削表面形貌和亚表面损伤进行了观察。提出了2D-C/SiC摩擦层(表面)的磨削力理论公式, 讨论了磨削加工用量对磨削力和磨削力比的影响。实验结果表明, 2D-C/SiC复合材料的高速深磨材料去除机制与其自身的微观结构相关, 既不同于塑性材料, 也不同于普通脆性材料, 而是以脆性断裂去除为主。     

立式玻璃磨边机砂轮离心振动特性分析

针对立式玻璃磨边机砂轮架的结构特点,建立其动力学模型及系统运动微分方程,导出砂轮离心力作用下砂轮架与砂轮振动的稳态响应幅值及其动力放大因子β1、β2的理论计算公式,着重分析砂轮离心力激振下砂轮架及砂轮的振动特性及规律,结果表明：β1、β2的大小和砂轮与砂轮架的质量之比µ、固有频率之比α,砂轮角频率与固有频率之比λ,阻尼比ξ等因素有关;合理选择µ、α、ξ值,可使砂轮与砂轮架具有相同且较小的动力放大因子;避免砂轮工作在λ=0.9~1.1对应的转速范围内,可有效减轻砂轮架及砂轮的振动程度。研究结果突破了现有研究将砂轮轴刚性化处理、试验测试装备复杂等缺陷,具有物理概念清晰、计算简单等特点。     

Optimization of diamond grinding conditions for steel R6M5F3 allowing for the process unsteadiness

The paper addresses optimization of machining conditions in diamond grinding of steel R6M5F3 taking into account the process unsteadiness. The optimization is accomplished for plunge-cut grinding by the elastic mode with a constant workpiece-to-wheel pressing force, the kinematics of the process being similar to the rigid-mode one. The region of possible machining conditions for an early stage of the elastic-mode diamond grinding is considered in the coordinates “workpiece speed—workpiece pressing force”. The workpiece speed is determined for a specified machined surface roughness. The workpiece pressing force is chosen to be minimal based on the condition of ensuring no phase-structural transformations in the surface layer of the workpiece material, no diamond oxidation, and no destruction of diamond grits. The process unsteadiness was allowed for through the use of the equations describing the time variation of the current limited cutting ability of the grinding wheel.     

Effects of grinding aids on the grinding kinetics and surface morphological characterization of quartz

The kinetic parameters of a grinding process can be used to study the variations in particle size reductions and grinding efficiencies. Appropriate grinding aids usually change the surfaces of a material and the properties of the pulp, thus improving the grinding efficiency. In this paper, pure quartz samples with mixed particle sizes and single particle sizes were selected as the raw materials. The effects of different sodium tripolyphosphate (STPP) and citric acid (CA) dosages on the dynamic parameters k, selection function S₁ and breakage function B for quartz grinding were studied. The results showed that the STPP and CA enhanced the grinding process of the quartz. In other words, the parameter k, the selection function S₁ and the breakage function B were all increased to varying degrees. The results of SEM, BET and contact angle measurements showed that the surfaces of the quartz particles became rounder, the specific surface area and average pore size increased, and the surface hydrophilicity increased. As a result, the grindability of the quartz increased, and the grinding kinetic parameters changed. Finally, the results showed that the improvements in the quartz grindability were consistent with the influence of grinding aids on the kinetic parameter k, selection function S₁ and breakage function B_i,1.     

Investigations on grinding process of woven ceramic matrix composite based on reinforced fiber orientations

Fiber orientations play the decisive role in grinding process of woven ceramic matrix composites, but the influence of woven fibers in grinding process is not clear. This paper studies the surface quality and grinding force by comparing different woven surfaces. Through a series of experiments in optimized sampling conditions, we analyze characteristics of the material surface topography height, wave distribution and surface support properties in details. And we find some outstanding characteristics of the surface microstructure. We also study the influence of grinding processing parameters on surface microstructure. The results show that machining surface which contains more parallel fibers is rougher and more keenness than gauss surface. Grinding wheel speed and depth of cut have great influence on surface topography and surface support properties. And it is discovered that grinding forces are also highly dependent on fiber orientations. The mechanism of the grinding phenomena is also analyzed in this paper according to knowledge of fracture mechanics and mechanical damage phenomenology. The research obtained will be an important technical support on improving the processing quality of woven ceramic matrix composites.     

Influence of dressing parameters on grinding performance of CBN/ Seeded Gel hybrid wheels in cylindrical grinding

Wide use of vitrified bond CBN grinding wheels in today's production grinding is due to their higher grinding efficiency and longer wheel life compared to other types of CBN wheels or conventional wheels. Trueing and dressing, however, strongly affect these advantages, since superabrasive wheels usually act dull after a dressing operation and require an initial break-in period. In this study, a rotary trueing and dressing process was investigated for vitrified bond CBN/ Seeded Gel wheels to determine optimum parameters required to eliminate the initial break-in period and to grind at steady-state right after dressing. This paper describes the effects and importance of dressing factors on wheel grinding performance. A limiting factor for useful wheel life between dresses is also suggested.