In nowaday, digital systems of PWB (Printed Wiring Board) and LSI (Large Scale Integlation) are very advancing to the high level function, complex circuits and many kinds of IC's. Therefore, the design of digital systems are applied by using CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) or HDL (Hardware Description Language), widely. On the other hand, the fundamental design of logical circuits is required to have technique and theory. In this paper, we discuss the fundamental design of variable sequential circuits and a method of synthesis by HDL. Then, we represent that a simplified circuit is obtained by using the state assignment of sequential circuit and the control assignment for variable function, and we describe the result of simulation.

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Recently, optical fiber network have been constructed for the high-speed and large-capacity communication system. One of the important technology related to the surface finishing is a metallization of the optical fibers. Since the optical fibers are usually connected using a resinbased sealing materials, a sealing strength is gradually damaged under the high humidity atmosphere. Therefore, a soldering technology is also proposed as the connection between the optical fibers and other optical components. If the soldering is applied, metal has to be coated on the fibers by the sputtering or other techniques. In addition, the smoothness of the coated metal surface is necessary for the improvement of the property of hermetic sealing. In this paper, we evaluated the applicability of the electroless Ni and Au on the optical fibers as the soldering base. As a result, the smooth Ni and Au films without extraneous deposition can be obtained using the fibers, which are free from organic or inorganic stain or particles on the fiber surface. The removal of particles existed in each treatment solution by the precision filtration is also effective to obtain the smooth deposited films. It is also confirmed that the solder fixed strength is excellent in the case of the smooth deposited films.

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Laser-enhanced gold electroless plating on Ni plated iron-nickel alloy, brass and copper was conducted in a cyanide free bath developed by us. The plating bath consists of chlorauric acid, sodium hypohosphite, succinimide, and potassium thiocyanate and the pH was 8.0. The thermal conductivity of the substrate is an important factor. Using nickel plated Ni-Fe alloy which is the lowest heat-conductive material in three materials, gold deposit height is the heighest at the same laser power and irradiation time. It was found that the gold deposit height and its diameter was controlled by laser power, irradiation time and the velocity of flow of the plating solution.

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The most promising candidate for Pb free solder would be the Sn-Ag alloys containing Bi or In to lower their melting points. In this paper, the mechanical properties of Sn-Ag alloys containing Bi have been evaluated in comparison with those of Pb-Sn eutectic solder. Our experiments indicated that these alloys have higher tensile strength and lower breaking elongation than Pb-Sn eutectic solder. Especially at room temperature, the coefficient expressing their sensitivity to strain rates was found to be lower than that of Pb-Sn eutectic solder. The breaking elongation of these alloys does not depend on strain rates. Therefore, it is predicted that the creep characteristics of these alloys are superior to those of Pb-Sn eutectic solder.

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The conductive resinous binding materials for bonding electrodes, recently drawing public attention in the field of surface mounting, contain conductive fine particles in the materials such as thermosetting resins. The electric properties of these resins will depend greatly on those of the dispersed conductive fine particles. Multiple particles have been measured in the conventional method, the measurement of a single particle, however, could not previously be attempted. For the development of the fine particles and/or the resinous binding materials, it is extremely significant to measure the electric properties of a single conductive fine particle. We have, therefore, newly developed a system measuring the contact resistance and the capacity of electric current, which are important factors as the electric properties of a single conductive fine particle. The relationship between the plated thickness of a metal coated resin particle and its electric property is quantitatively examined and reported in this paper.

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