This paper describes an automatic solder joint inspection system by X-ray imaging. The following were developed for highly reliable inspection of J-lead and gull-wing lead solder joints : (1) An automatic inspection method for double side-mounted PCBs (Printed Circuit Boards) by micro-focus X-ray imaging and board tilting, (2) Enhancement of X-ray image of solder joints by logarithmic transformation of a detected image, (3) Fillet judgement by comparison between a detected image and a number of typical nondefective images selected by a clustering procedure, (4) Bridge determination by multi-step thresholding and comparison between pattern frequency distribution of a detected image and that of a nondefective image. The inspection system developed with these technologies had a defect detection rate of 100% with the smallest detectable defect being 50 μm.
In order to develop Scanning Acoustic Microscope (SAM) having high resolving power, the acoustic lens for a high acoustic frequency range which has very small spherical concave has been fabricated by micromachining. Silicon single crystal is used as the material for the acoustic lens. Suitable etching conditions to obtain excellent sphericity and minimal surface roughness demanded for a lens profile, have been investigated. The optimum etchant was mixture of hydrofluoric, nitric and acetic acids in the ratio of 2 : 3 : 3, at 50°C. The influence of the aperture diameter of the etching mask and etching time on the spherical lens profile was examined. The etched concave profile for 1 GHz range lens fabricated under the above conditions showed a maximum deviation from a perfect sphere of less than 0.2 μm. Silicon lens designed for frequency 1 GHz exhibited the theoretical resolution expected from the wave length.
The self-maintenance machine is a machine that can maintain its function flexibly even though faults happen in it. To realize functions for diagnosing and repair planning, a model based approach based on qualitative physics is proposed. Repair methods of the selfmaintenance machine are conducted after qualitative simulations, but there are two problems with executing repair. The first problem is difficulty of the constructions with multiple repair operations. The other problem is the performance time. In this paper, we first discuss the validity of case based reasoning to these problems. Second, we propose the methodology for applying case based reasoning to repair executions for the self-maintenance machine.
A new method to improve the damping of stepping motors is proposed. The idea is to utilize the information on position and velocity contained in the back electromotive force (BEMF) induced in the coils. This information is extracted with a simple analog circuit and processed by a feedback controller. The performance of stepping motors can thus be improved at low cost, e. g. by increasing the mechanical damping characteristics of the rotor. Theoretical studies and experimental work are presented. A reduction of settling time from 120 ms to 5 ms has been obtained.
This paper presents the fundamentals for eliminating overshoot and vibration produced by dynamic loading, especially impact force in material tests. Overshoot and vibration are usually eliminated from original values with dampers and filters, since they prevent determination of true loading values. The fundamentals make it possible to determine values for eliminating undesirable phenomena.Three model sensors based on the above fundamentals were made to confirm effectiveness. From experimental results, the validity of the fundamentals as a load sensor for eliminating the overshoot and vibration was confirmed practically.
This paper presents a real-time SMART (separated mark TTL alignment) technique for optical lithography systems. The new TTL alignment optical system corrects lateral chromatic aberration which has made impossible reticle-to-wafer real-time alignment (during exposure) at all mark positions. The optical method of correcting lateral chromatic aberration is described. This correcting method was applied to a KrF excimer laser optical lithography aligner to demonstrate the principle of this alignment method. The simulation results of alignment beam positions were similar to the experimental results. At each alignment mark position, the alignment signal level was sufficient to allow detection as a positioning signal, an overlay accuracy of ± 0.05 μm (3σ) was achieved.
Several kinds of cam motion curves have been utilized to the high speed positioning or the contour tracing. To realize the same performance by servo motors, the bangbang or the optimum control and others are applied recently. This paper describes the feedforward methods to obtain the same high speed positioning as the mechanical cam motion by applying the inverse transfer function compensation for DC motor driving system with one degree of freedom vibration load, giving the Polydyne motion curve inputs. By this method to give the dwell-risedwell polynomial motion curve with continuous velocity, accelaration and the other higher order differential at start and final points, the output loads are able to be obtained the positioning at arbitrary setting conditions without the feedback from the load. By the adequate selection of Polydyne curves on the basis of the residual vibrating characteristics, the positioning stable for parameter variations are clarified to be obtained.
In recent years, needs for drilling small diameter holes (φ0.2-0.4 mm) are increasing, accompanying the development of higher wiring density of printed wiring boards. However, the drilling of small diameter holes includes many technically difficult problems which must be solved. In contrast to drilling of normal diameter (φ0.5-1.2 mm) where epoxy smear, surface roughness of the hole wall, tool life, etc. are important, small diameter drilling has a different set of performance criteria : drill breakage, initial positional accuracy and hole bending. This investigation was conducted to examine hole positional accuracy and hole bending in relation with tool wear using φ0.4 mm drill to several kinds of glass epoxy circuit board. Furthermore, to limit initial slippage and then bending, vibrant drilling and drilling with a cross-thinned drill were carried out. A numerical analysis was executed to obtain accurate flexural rigidity of the drill which has an effect on the slippage before the drill point has stayed at a certain position and on hole bending even more. Conclusions are summarized as follows : (1) Amount of hole bending is generally affected by that of tool wear, but initial positional accuracy is less affected. (2) Hole bending develops with drilled depth without hole wondering (Burnhum, 1980). (3) Vibrant drilling is effective for minimizing hole bending but less for limiting initial slippage. (4) The effect of cross-thinning on hole bending is as evident as of vibrant drilling, but not on initial slippage.
This paper deals with a new method for an adaptive control of cylindrical plunge grindings. A workpiece with high accuracy can be obtained in a conventional grinding method since finish timings of each grinding stage (rough grinding, fine grinding and spark-out grinding) are determined by a high accuracy sizing gage. However, this method often results in low grinding efficiency and low integrity of workpieces. These problems are caused by the fixed finish timings of the fine grinding stage and the spark-out grinding stage. In this study, a method based on variable timings is introduced. The timings are determined depending on a size generation curve which is calculated on the basis of the measured data of the workpiece diameter in the fine grinding stage. These results are instantaneously fed into an NC computer on the grinding machine and the grinding process is adaptively controlled for various grinding conditions and various workpieces. As a result of some experiments, it has been cleared that the proposed method is valid to the variation of the depth of grinding in the rough grinding stage, the variation of the velocity ratio and the structural stiffness, while there is some room for further study to the grinding of a workpiece with soft property.
The study deals with the development of a new cupped diamond wheel used in ultrasonic surface grinding of brittle materials such as fine ceramics. The wheel has a larger diameter and higher stiffness than the usual wheel, therefore it allows the user to grind brittle materials efficiently and precisely. By using the CAE system which has been developed to design an optimal high-intensity ultrasonic system, the wheel is designed optimally so as to resonate in half-wave at the resonance frequency of an employed ultrasonic vibrator. Then, the wheel is produced on the basis of the designed values, its vibrational properties are measured, and the experiments using it in ultrasonic surface grinding are carried out. As a result, the reasonabilities of the designed values are proved, and the potentiality of the wheel is confirmed.
No matter what wear mechanism controls tool wear, tool wear rate can be expressed as functions of stress and temperature on the tool face. Thus stress and temperature distributions on the rake face were measured with split tools and with thermocouples respectively to obtain wear equations. Specific crater wear rate of coated tools was linear with normal stress and increased exponentially with temperature. Using the wear equations, crater wear of coated tools was predicted through cutting temperature analysis by the newly proposed finite difference method. The calculated results for the tools with single and double coating layers were in good agreement with experimental results. The analysis for predicting crater wear of coated tools showed that thermal conductivity of substrate has a great influence on tool wear rate.
This paper deals with wafer chucking technology, a dominant factor in wafer flatness, in a one-by-one automatic mirror polishing process for large size silicon wafers. Rigid vacuum chucking generates wafer dimples from unexpected particles coming into the interface between wafer and chuck surfaces. Soft chucking with porous elastic film pads as chuck surfaces can prevent the generation of wafer dimples. Especially, controlling the moisture content distribution through the porous elastic film pads can achieve a good chucking accuracy to improve the wafer flatness in the chuck with a pressure detaching mechanism for automatic unloading.
This paper describes characteristics of machining burrs generated inside the main hole at the intersection where cross holes are drilled, and the ball burnishing method to be employed to remove the burrs. The results obtained are as follows : (1) Both height and width of the burrs are small in the order, free-cutting steels, commercial aluminum, low carbon steel (SS400). (2) The generation of the burrs depends on the diameter difference between a main hole and an intersecting hole, and the feed rate at the end of drilling as well. (3) The burrs are decreased by the penetration of a crossed hole due to the moving chips inside the main hole. (4) The removal rate reaches 89 % for the leadedresulphurized steel, but it decreases down to 45 5 for the aluminum. (5) The direction of drilling as well as the rolling direction of work materials influence the burr formation and the deburring characteristics.
A new unit type magnetic finishing apparatus composed of ferrite permanent magnets is developed to finish precisely the internal surface of a non-ferromagnetic tubing, as a substitute for the previous finishing apparatus with large and heavy electromagnetic coils. This new finishing unit is installed easily on the carriage of a conventional lathe. The finishing jig composed of rare earth permanent magnets is also developed by which the powerful finishing pressure is generated by a magnetic force. This paper described the new unit type finishing apparatus, the finishing jig and their internal finishing performances for cleaning stainless steel tubings.
In the theory of the screw thread analysis, it is often necessary to solve the transcendental equations. But it is difficult to solve the transcendental equations. So, the expanding calculation method is developed to derive an approximate formula from a transcendental equation of certain variable. In this article, an application of computer algebra, “REDUCE, ” which operates on personal computer to the expanding calculation method is reported. Through this application, new approximate formulas of the grinding wheel profile for the cutting face of the hob are derived. The complicated procedure of the expanding calculation method is made easy and quick by the successuful application of computer algebra. Also more accurate approximating formulas are now obtainable.