Optimization of the beam shape for laser drilling is theoretically discussed. Laser drilling is widely used in manufacturing vias on printed wiring boards. For that purpose, instead of an ordinary Gaussian beam, a flat-top beam is required at an object surface. An optimization method of the beam shape is proposed that uses the Fourier-Bessel series expansion of the complex amplitude distribution at an object surface. Each term of the series is related to a certain spatial frequency and the spatial frequency distribution of the beam at the object surface is related to the amplitude distribution at the lens. Terms having a spatial frequency lower than that related to the lens radius are used to optimize the beam shape so that the optimized beam shape is realized by an actual lens that has a finite aperture. The coefficients are determined such that they minimize the residual between the target shape and the beam shape. The optimization method is validated numerically using a CO₂ laser drilling system, and the result shows that it is effective.

View full abstract

In order to study an unknown mechanism of defect initiation in Hertz indentation of monocrystalline silicon with no preexisting defect, analytical solution controlled-MD simulation proposed by the authors has been carried out using an MD model embedded on the surface of silicon. It has been shown that a defect that will become a ring crack can be generated just outside the outer periphery of the contact area between the silicon and indenter. The mechanism of the defect initiation is that the dynamic force associating with acoustic waves transforms monocrystal structure to polycrystal one at the outer periphery of the contact area and this phase change under a macroscopic/static tensile stress acting there triggers cross slips which result in micro-void defects.

View full abstract

To be attained a machining accuracy by Atomic Force Microscope (AFM) probe, it is necessary to make clear the machining mechanism by AFM probe material. Therefore, taking account of the new developed AFM probe materials, this paper proposes the groove generation processing model based on Fluctuation-dissipation theorem using friction force examined a groove machining on nano-sheets. The probability distribution estimated from the model allows us to provide that the correlation of the machining accuracy for groove width coarseness and the coefficients of friction between AFM probe and nano-sheets. Furthermore, the calculated dispersion from the probability distribution of the model is tended to be consistent with groove width coarseness evaluating machined groove.

View full abstract

As a surface reference conditioner, original flexible fiber conditioner was developed to realize uniform pad conditioning in CMP (Chemical Mechanical Polishing). The developed conditioner is composed of a lot of bundles of fine metal fibers to contact pad surface independently. Constant conditioning force can be applied to pad surface with fiber edges regardless of long range of height variation of pad surface. In fact, the developed conditioner made pad surface to be roughened with conforming to a protruding area of 50um on pad surface. Furthermore, an original evaluation on conditioning uniformity was demonstrated quantitatively by making use of relationship between in-depth color variation and pad conditioning depth using dyed pad. As the result, the developed pad conditioning was more uniform entirely across a pad than traditional disk type conditioner. The performance resulted in both contraction of pad break-in process and improvement of removal rate uniformity within wafer in the course of pad break-in process.

View full abstract

The simulation of lapping to correct the surface profile of a workpiece has been made very little study. In contrast, the simulation of polishing has been developed using the gap theory and it has been demonstrated that there is good agreement between simulated and experimental results. Our study investigates the application of polishing simulation to lapping. We have reported that a lapped profile can be calculated if a suitable value of relative elastic coefficient is used. This paper describes workpiece and tool profiles lapped with a small tool, and corresponding simulation results calculated using the gap theory, for oscillation lapping to planarize a quartz glass wafer. Under non-oscillation conditions, the experimental results for workpiece and tool profiles correspond roughly with simulated results. When the tool overhangs the workpiece, to a significant extent, the experimental results do not correspond with the simulated ones. Therefore, the slope of the pressure distribution for the simulation was adjusted to increase rapidly when the amount of overhang is more than 30 % of tool diameter. As a result, the experimental and simulation results corresponded very closely. In uniform-oscillation-speed lapping, it was demonstrated that the achieved workpiece and tool profiles coincide approximately with the results of the simulation.

View full abstract

Glass-like carbon (GC) is expected as a die material for mold-press of optical glass devices. However, the mechanical and thermal properties are not enough to use as mold die. Recently, glass-like carbon/carbon nanotube composite (GC-V) reinforced by vapor grown carbon fiber (VGCF) was developed to improve the properties. In this study, optimum machining conditions on electrical discharge machinability of GC-V were examined to enable wide area machining. The machined surface of GC-V with 5 or 14vol% VGCF was characterized by no crack and smaller roughness than that of the GC when machined in a voltage range of 50∼70V. Also, the machining time of the GC-V was shortened. Furthermore, the surface roughness of GC-V etched by focused ion beam (FIB) was enough to use as glass mold die.

View full abstract

In studying the process method for a nickel-cavity base-plate of an inkjet print head, the micro-press process (cold forging and micro-precise punching) was used to replace a silicon-cavity base-plate with a nickel-cavity base-plate. As a result, the punch life was extended to a mass-production level. Nevertheless, the deformation by the size of several micrometers resulted during the micro-press process still remained an issue. This paper introduces the processing technique to minimize the deformation when employing the double-sided micro polishing process. It flattens the bump of base-plate to the required 2micrometers or less in size. This study has found the hardness of polishing cloth and the supply quantity of slurry have an affect on the bump of base-plate.

View full abstract

Tungsten carbide films were synthesized on Si wafer by pulsed vacuum arc deposition using a sintered tungsten carbide cathode. Arc discharge voltage, capacitance of capacitor, and cathode-substrate distance were controlled for changing film properties. For the evaluation of crystal structure, X-ray diffraction analysis was performed. Mechanical properties of films were characterized using AFM, nano-indentation and ball-on-disc friction tests, and the results were compared to those of films deposited by R. F. magnetron sputtering. The hardness of films was in the range of 9-28 GPa. Friction coefficients were almost the constant values of 0.4-0.5. Harder film showed lower wear rate. Films deposited by pulsed arc deposition were smoother and high wear-resistant.

View full abstract

CMP (Chemical Mechanical Polishing) attracts attention as a technology polishing the glass base of the photo mask used for the liquid crystal products. The quartz glass is rubbed up by polishing pad that the chemical liquid slurry is soaked. The slurry has important roles on CMP because it promotes polishing and removing rubbish by flowing between the polishing pad and quartz glass. However, slurry flow can't be observed easily, numerical analysis is useful tool to clarify the slurry flow phenomenon. The lattice grooved pad is paid attention in this study as a basic grooved pad to make the slurry flow efficiency. None grooved pad and the lattice grooved pad are analyzed, and the feature of each pad is clarified. The analysis results show the slurry isn't replaced easily near the pad center under the square quartz glass on flat pad. On the other hand, it becomes easy for the slurry to be transported on lattice grooved pad by the grooves, and it flows to the whole uniformly. When this analysis results are compared with experimental results, they agree qualitatively. Therefore, to supply the slurry uniformly, and to polish efficiently, it has been understood that the lattice grooved pad is excellent.

View full abstract

The grindability of fine-ceramics is the most important information in order to determine the optimum grinding conditions and dressing intervals. This study proposed the method of grindability evaluation of fine-ceramics by using removal rate in constant pressure grinding. In this paper, constant pressure grinding of four kinds of alumina in which particle diameter differs was performed. And, the influence of particle diameter on removal rate was examined. As a result, it found that the removal rate increases by the 0.5th power of particle diameter based on the Griffith theory. Then, the removal rate in consideration of particle diameter was formulated based on this experimental result. The calculated removal rate was well corresponding to the removal rate obtained by experiments. From these results, the possibility of evaluating the grindability from both mechanical properties of fine-ceramics and particle diameter was found.

View full abstract

This paper presents an optimization method for maintenance scheduling in re-entrant production lines using Lagrangian decomposition coordination method. The proposed approach regards maintenances as jobs within limits of starting and finishing time, so that the schedule can realize not only proper maintenance to prevent facility troubles but also high productivity. A case study is presented for a semiconductor manufacturing system, in which it is difficult to find a proper plan because of complex process flow so that the jobs often re-enter into the facilities. The feasibility of the proposal is discussed using computer simulation results; the proposed method can realizes feasible solutions in the problems where the objective function is set to minimizing total tardiness.

View full abstract

This paper proposes a novel method of generating a 3D virtual foot model from multiple camera image data based on the GFFD deformation method. 3D virtual foot models for individual persons can be generated easily and rapidly with considerably low cost. By estimating the cause of errors that can occur in the whole process and endeavoring to lower the errors, we succeeded to achieve satisfactory accuracy. The errors are mainly classified into two kinds. One occurs in transforming process with use of the GFFD deformation method and the other in obtaining 3D coordinates of feature points. So, we devoted ourselves to eliminate the cause of both errors and repeated experiments again and again. As a result, we got to get a 3D virtual foot model within acceptable error range. The average error is 1.32∼1.72mm.

View full abstract

To fix precisely by laser wedding between an optical collimator and a main body of optical components, automatically laser trimming technique has been achieved by non-contact processing for the passive optical components. This control system is consists of a pulsed YAG laser and an optical power monitor only as simple configuration. From starting program, it spends a time within 150 seconds and forty welding points at most to produce the completed components in laser trimming processing.

View full abstract