SIMULTANEOUS DOUBLE-SIDE GRINDING OF SILICON WAFERS: A REVIEW AND ANALYSIS OF EXPERIMENTAL INVESTIGATIONS

Simultaneous double-side grinding (SDSG) has become an important flattening process for manufacturing of 300 mm silicon wafers. However, the literature contains only a small number of papers on SDSG. In contrast, there are a large number of patents pertinent to this process. There is no review paper summarizing all these reported experimental results. This paper reviews the literature on experimental investigations on SDSG of silicon wafers. It first describes input variables in SDSG, and then presents their effects on output variables, covering warp, flatness, surface roughness, nanotopography, wafer-thickness variation, rotational asymmetry, grinding marks, subsurface damage, wheel wear, and process cycle time. It also discusses the definition, significance, and measurement of each of these output variables. Finally, it tabulates reported experiments to show what has and has not been reported in the literature.     

A NEW METHOD FOR MACHINING OF ELECTRICALLY NONCONDUCTIVE WORKPIECES USING ELECTRIC DISCHARGE MACHINING TECHNIQUE

In this study, a new method for machining of nonconductive ceramic workpieces in electric discharge machining (EDM) was developed. Machining surfaces of nonconductive workpieces were coated with a conductive layer (CL) and graphite powder was added to dielectric fluid for machining. Al₂O₃, ZrO₂, SiC, B₄C and glass workpiece samples were machined by using the method. Different machining conditions were tested for each sample and optimum machining parameters were determined. Effect of electrical conductivity, thermal conductivity and melting point of workpieces on material removal rate (MRR) was investigated. Optical microscope and SEM (Scanning Electron Microscope) surface photographs of workpieces taken after machining are presented and discussed.     

A GEOMETRICAL APPROACH FOR REDUCTION OF TOOL SHAPE DEGENERATION IN ELECTRIC DISCHARGE MACHINING (EDM)

In this study, the geometric wear characteristics of tool electrodes were obtained for various pulse time, discharge current and machining depth settings in electric discharge machining. Different forms of protrusions were machined on the front surface of the tool to reduce the geometric wear. Significant reductions in original tool geometric wear characteristics (front wear, side wear and edge wear) were obtained with the use of square cross-section protrusions. The dimensions of the square cross-section protrusions were modeled mathematically in terms of machining parameters used in the experiments.     

机械设备流固耦合动力分析的有效方法

提出流固耦合动力分析的新方法。该法通过结构动力学的有限元求解方程和Newmark法,导出了新的迭代公式。流场的动压力使弹性体的动态特性变为载荷非线性问题;同时,固体位移场的变形作用使流场成为可变域流场。这些问题都可用本法得以解决。文中给出算例和工程应用实例。数值解结果表明,该法收敛速度快,效率高,克服了耦合问题的求解困难。