Key Engineering Materials Vols. 389-390

Abstract: When many products were cut out from a wide base sheet by laser cutting in some conditions, an error occurred in a height regulator by the sheet's greatly bending. It is necessary to avoid occurring the error at unmanned processing. We paper investigated local deformation around cutting edge. The cutting path consists of piercing point, terminal point, straight lines, cranks and curves. We measured local deformation around terminal point, crank and straight line. It was clarified that base sheet bent greatly around terminal points and crank and the sheet curved gradually along the straight line. We investigated relationship between global deformation of the base sheet and the local deformation. It was able to presume the entire deformation of base sheet by overlapping the individual deformations around cutting edge.

Abstract: A new finish mode combination of grinding and electrochemical smoothing executes a finish processes on SKH 51 surface is investigated. In the experiment, a high rotational speed of finish tool produces a better finish. A thin electrode associated with higher current density provides a larger discharge space for a better finish. The design change from a full form finish-tool to a partial finish-tool leads more discharge space, which creates better finishes than full form tool. It is a great contribution that the synchronous finish processes has a high efficiency than the electrochemical smoothing to make the workpiece surface smooth and bright.

Abstract: TiO2 has some unique photocatalytic functions and some of them have been utilized industrially, and further functional enhancement and performance enhancement of TiO2 have been required. Under such circumstances, this study aims to clarify the influence of surface topography on the photocatalytic reaction of TiO2 film surface. As the first step, the optimum mixing ratio in film preparation by using TiO2 powder was examined and the films with several kinds of surface roughnesses were prepared. And, the influence of surface topography on the wettabilty, which is one of the photocatalytic functions of TiO2 was evaluated. As a result, it was confirmed that the wettability of TiO2 films could be improved by increasing both the surface roughness and actual surface area under the ultraviolet rays irradiation environment.

Abstract: A method to easily and economically manufacture more precise patterns compared with usual MEMS technique has been searched for. Under such circumstances, this research aims to clarify the formation of nano-scale protrusion structure produced by local anodic oxidation on Si wafer surface in expectation of the nano/micro mold production for nanoimprint lithography in future. In this report, the influences of contact width and distance between probe tip and Si wafer surface (distance between terminals) on the size and shape of protrusion patterns were examined in order to clarify the fundamental phenomena in local anodic oxidation. A scanning probe microscope equipped with a current measuring unit was utilized in local anodic oxidation experiments. As a result, it was confirmed that the size of generated protrusion structure became larger with increasing the contact width and became smaller with increasing the distance between probe tip and Si wafer surface. These facts will be useful in producing 3-D nanostructures in future.

Abstract: Electrical discharge machining (EDM) is an excellent technology to machining die and mold, but it is uneasy to obtain mirror-like surface. Powder-Mixed dielectric electrical discharge machining (PMD-EDM) is the innovative technology of EDM process, which can improve the quality of machined surface and applied in EDM finish machining now. The powder is usually hard particles, such as Al, Cu, Cr and Si in PMD-EDM. This paper presents a new research of PMD-EDM with suspending soft particles and abrasive grits in the dielectric fluid, especially focus on surface roughness. Experimental result shows the EDM process with polymer particles and abrasive grits can be carried out in silicone oil and the surface roughness has the finer improvement when increasing the rotation speed. Also, the effect of hard particles suspending in dielectric fluid are also discussed and compared. The surface roughness using polymer particles and abrasive in specific condition was better than only hard particles in silicone oil. Moreover, mixing abrasive and polymer in EDM can perform the polishing process.

Abstract: An investigation was undertaken to elucidate the mechanisms for the fracture failure of brazed diamonds in wire sawing. Diamonds were brazed by high-frequency induction in vacuum. The changes of compressive strength and the appearances of the diamonds at different brazing temperatures were obtained. The morphologies of the diamonds after sawing were also observed. Together with the stress analysis of a brazed grit, it is found that the fracture failure of brazed grit is the result of the brittle fracture happening on the root section of the grit, the interface between the grit and the brazing alloy. The degradation of mechanical properties of grits in brazing is a key factor to the reduction of their resistance to fracture. Lower machining forces as well as grit exposure are in favor of preventing grits from fracture.

Abstract: Warp accuracy and nanotopography in the silicon wafer slicing process influence the final quality of the wafer. Therefore, methods to improve these factors are important. And this will require the achievement of low costs and high quality processing – conflicting requirements – with larger sized wafers than in previous generations. The present study was performed to assess mechanical factors, such as machine static accuracy and thermal deformation, to improve the accuracy of multi-wire saws. This report deals with the influence of thermal deformation of the ingot and wire guides upon processing accuracy, and describes the assessment results.

Abstract: With increasing in size of glass substrates for flat panel, both high productivity and high quality are required for its edge rounding process. In order to understand the effect of process speed on the strength of glass substrate, this study performs a profile grinding at the substrate edge with varied feed rate. The obtained glass substrate then undergoes a four-point bending to evaluate its strength. Weibull distribution is used to analyze the fracture strength of glass substrate after edge-rounding process and to correlate the removal rate with the quality of the process.

Abstract: This paper investigates the “pop-in” behavior of monocrystalline silicon under nanoindentation with a Berkovich indenter. The indentation tests were carried out under ultra-low loads, i.e. 100 μN and 300 μN, with different loading/unloading rates. It was found that with the experimentally determined area function of the indenter tip, the mechanical properties of silicon can be accurately calculated from the load-displacement data, that a pop-in event represents the onset of phase transition, and that a lower loading rate favours a sudden volume change but a rapid loading process tends to generate a gradual slope change of the load-displacement curve.

Abstract: An innovative fixed abrasive grinding process of chemo-mechanical grinding (CMG) by using soft abrasive grinding wheel (SAGW) has been recently proposed to achieve a damage-free ground workpiece surface. The basic principle, ideas and characteristics of CMG with SAGW are briefly introduced in this paper. The CMG experiments using newly developed SAGW for Si wafer are conducted at the condition of dry grinding. The grinding performances are evaluated and analyzed in terms of surface roughness, surface topography and surface/subsurface damage of ground wafer by use of Zygo interferometer, Scan Introduction ning Electron Microscope (SEM) and Cross-section Transmission Electron Microscope (Cross-section TEM). The component of product of ground Si surface is studied by X-ray Photoelectron Spectroscopy (XPS) to verify chemical reaction between the abrasive / additives of grinding wheel and Si wafer. The CMG process model by using SAGW is developed to understand the material removal mechanism and generation principle of damage-free surface. The study results show that the material removal mechanism of CMG by using SAGW can be explained as a hybrid process of chemical and mechanical action.