Advanced Materials Research Vol. 1017

Abstract: Micro-drilling become more widely used from precision mechanics to electronics. Nowadays, the main commercial tools are planar point micro-drills. However, that geometry often causes a high thrust force, high temperature, and rapid wear during micro-drilling. Furthermore, it is difficult to adjust the four flank surfaces to accurately intersect at one point, particularly when the drill diameter becomes smaller. To solve this problem, non-coaxial helical drills points have been proposed by some researchers, and is characterized by a continuous helical flank instead of the piecewise planar flank. Its drilling performance is improved compared with planar drill point. This study presents a 5-axis coordinated CNC grinding method of the non-coaxial helical drill flank. Mathematical models of the drill flank and its engagement line between cylinder grinding wheel and drill tool are established, and then the path of the grinding wheel with respect to the drill tool is obtained. In order to verify the availability of the proposed methods, three dimension (3D) grinding simulation of non-coaxial helical drills with diameter 0.5mm was carried out using the CAD software, and then were fabricated on a 6-axis Makino CNC tool grinder. The ground micro-drills examined by 3D laser scanning microscope show good identity with the simulated result. These indicate that the manufacturing model presented in this paper provides a practical and efficient method to grind the flank of a non-coaxial helical micro-drill.

Abstract: Small angle neutron scattering (SANS) analysis using ellipsoidal neutron mirrors are highly demanded for basic researches of high tensile strength steel sheets, proteins and polymer materials. Although the mirror was conventionally assembled from multilayer neutron super mirrors deposited on ground and polished glass segments, it was difficult to align segmented mirrors with high accuracy and it took several months for the grinding and polishing process. An optimized manufacturing process is proposed utilizing optical function evaluation based on measured mirror surface profile. Optical aberration caused by surface form error and misalignment is evaluated by ray-tracing using mirror surface profile measured by non-contact high precision profilometer.

Abstract: A dual probe non-contact ball roundness measurement method is presented in this paper. With two probes aligned in opposite directions, the direct measurement of diameter variation can be obtained. The relationships between diameter variation and out of roundness of a precision ball are discussed. Attempts of error separation using multiple measurements are carried out and the eccentricity of ball and spindle axis is measured. Measurement results indicated that other than the spindle radial run out, which is synchronous in nature, there also exists high frequency non-synchronous variations. Such non-synchronous errors can be effectively eliminated with the dual probe arrangement for diameter variation measurement. The measurement results showed that such set up is capable of measuring high precision balls for diameter variation and out of roundness with uncertainty of less than 10nm. Single measurement can be completed in 10 seconds with over 10,000 data points. Faster measurement is possible with improved air bearing spindle. The method is suitable for online application of precision ball diameter variation and out of roundness measurement.

Abstract: A point autofocus instrument (PAI) is widely used for the roughness and contour measurement of various precision processing surfaces, because it is capable of measuring a large area in high precision. The only disadvantage of PAI is to require a long measurement time. Its conventional index measurement stops the scanning stage in order to obtain each coordinate value of the fixed sampling pitch. Hence, it was necessary to develop a scanning point autofocus instrument (SPAI) which can obtain coordinate values while the scanning stage is moving. As an achievement of the development, the SPAI offers 26 times faster measurement speed than that of the index measurement with equivalent accuracy. The SPAI easily measures 3D surface texture and provides quantitative evaluations of the precision processing surfaces.

Abstract: Wafer thickness meter by reflection spectroscopy is used for on-site thickness inspections in wafer thinning process, because of its excellent properties as high measurement accuracy in very thin wafers inspections by non-contact sensing. In practice, ground surfaces are not ideal flat surfaces. Thus the spectra suffers influences of the surface roughness and the waviness, as modifying spectral features by optical diffusion, and as decreasing the reflection received by dispersion of propagating directivity. In this paper, we investigate how the surface integrities of ground wafer surfaces are involved in the thickness measurements by both theoretical and experimental approach, to investigate the requirements in sample conditions and to guarantee the accuracy of the measurements.

Abstract: The surface of the grinding wheel and the conditions under which it is prepared has a profound influence upon the grinding performance as characterised by the grinding forces, power consumption, cutting zone temperature and component surface finish. Only by having a clear understanding of the wheel topography can the interaction of the grinding wheel surface with the workpiece be fully understood. Two dimensional measurements or profilometry, while being a relatively quick measurement to perform, suffers from information quality issues due to the subjectiveness of the profile location as well as questions regarding how representative a profile is of a three-dimensional real surface. While profilometric measurement has long been standardised in the form of various international standards, topographic standards have only recently been agreed upon and formalised as ISO 25178. In this paper a comprehensive approach to wheel topographic characterisation will be undertaken. Factors such as measurement strategy, filtering, active grain identification as well as the fidelity of surface replication will be considered. The paper will propose a recommended measurement strategy and surface parameter set deemed sufficient to provide a comprehensive understanding of the grinding wheel topography.

Abstract: For a cutting process using a low-rigidity end mill, it is very important to be able to estimate the degree of machining error caused by the deflection of the tool. The purpose of this study is to establish a method of estimating, in real time, the machining error caused by the deflection at the cutting point of an end mill. To this end, in this research, a method for estimating the machining error caused by the deflection of the tool used for the ball-end milling of a hemispherical surface was verified by comparing the estimated and measured deflections of the tool. As a result, it was found that the machining errors in ball-end milling could be estimated from the normal force at the moment when the radial direction of the peripheral cutting edge is normal to the feed direction of the tool.

Abstract: Large wear of diamond tools for ultra-precision cutting of soft metals deteriorates quality of machined surface, and the worn tools have to be replaced with new tools when the tool wear reaches limited wear land width of cutting edge generating finished surface. However, it is difficult to predict the tool life since all cutting tools have individual tool life. Therefore, the purpose of this study is to estimate wear land width of cutting edge of a single crystal diamond tool having large nose radius by using static cutting forces during machining. As a result of the cutting tests and measurements, it was found that the ratio of thrust force to principal force had good relation with the ratio of flank wear land area to cutting cross section area. Furthermore, according to some detailed observation of flank wear, width of flank wear land was greatly related to uncut chip thickness obtained under different cutting conditions and it was found that width of flank wear land could be estimated by measured static cutting forces and cutting conditions.

Abstract: CMP Technology is still expanding its application field to realize planarization of complicated structures for More-Moore and More-than-Moore devices. The CMP equipment has been developed based on simple rotary motion but with more sophisticated systems for 300mm wafer applications. This paper deals with future prospects of the CMP equipment for micro-and nanopatterns on different types of substrate which are recently on demand to meet technological requirements. These industrial environments make equipment makers grow out of insisting rotary type motions anymore and get new opportunities. This paper describes basic design considerations according to substrate size and shape, and shows a couple of examples for not only large sized wafer, display panels and printed circuit boards, but also thin, flexible and continuous films. Finally, we hope that the design considerations for future CMP equipment make many discussions and solutions to achieve higher quality and throughput in the field.

Abstract: Photovoltaic power, a well known renewable energy source, has been introduced on a global basis. A popular variation has many solar battery cells constituted by a polycrystalline or a single crystal silicon wafer. Therefore each cell’s conversion efficiency from solar energy to electrical energy is very essential. Recently, a fixed grain wire method, in which the wafer is sliced by a wire fixing grains on the surface with a bond or an electrodeposition, is employed in that slicing process. Thus, the wire surface topography must be obtained in order to sustain reliable accuracy. In this paper, the measurement method of a diamond wire surface topography using an image processing method is proposed. According to this method, the distribution of grains on the surface can be expressed numerically after grains are extracted from the captured images of the wire surface. Finally, the effectiveness of the proposed scheme was verified through a measurement experiment for a diamond wire.