Electromechanical devices such as relays, switches, connectors and printed wiring boards have shown quick growth along with remarkable progress of electronic products in a recent few decades. For the present, outstanding tasks common to these devices are further downsizing, higher density and broading of bandwidth, on the assumption of keeping high performance and high reliability. These tasks are realized by part production improvement for higher precision and automatic assemblies, development of constituent materials and development of breakthrough structural technologies such as a surface mount technology and an active assembly ferrule technology in optical connectors and so on. In this paper, the technical trends as well as the motive technologies are overviewed for each device.

Reliability of an electric contact can be defined by two parameters, contact resistance and wear, and the parameters of contacts operated in arcing condition are governed by the arc discharge. Thus the measurement on the relationship between the parameters and arc phenomena is necessary to improve the contact performance. The parameters for arcing electric contacts and problems were reviewed, and new concept for electric contact testing systems was proposed. Measurement with such an advanced system should be concurrent parallel measurement, quantitative measurement of degradation, systematic measurement, and analysis of arc discharge phenomena. Some examples of advanced measurement systems and new data obtained with such systems were described. Systematic results on relationships between condition and performance parameters were obtained by systematic measurement with systematically settled conditions, such as opening speed or material condition. A measurement method for the metallic phase arc duration was developed by the authors, and role of the metallic phase arc on contact performance parameters was found from interpretation of obtained data. The real-time surface profile measurement of an operating contact and the optical transient spectrum analyser for arc light radiated from breaking contact were also described.

A new self-holding optical switch that consists of an optical matrix board and a precision robot is proposed. Fabrication and evaluation of 33 optical matrix boards confirm the feasibility of large-size optical switching. Suppressing deviations in the groove position will realize lower loss optical matrix boards in the near future. The apparent roughness of the groove walls can be evaluated simply and effectively by measuring return loss with an interferometric optical-time-domain reflectometer.

This paper describes the optical characteristics and static fatigue reliability of a zirconia alignment sleeve, which is a component part of an optical connector with zirconia ferrules. This combination of sleeve and ferrules hardly generates any wear debris during connector insertion and removal cycles. This has reduced the cleaning frequency of the ferrule endface during cycles and greatly improved the return loss stability of the optical connectors. The zirconia alignment sleeve enables stable return loss characteristics to be achieved over a wide temperature range as it has the same thermal expansion coefficient as the zirconia ferrule. Furthermore, the gauge retention force for the zirconia alignment sleeve is defined with a view to its practical use. This force must be between 2.0 and 3.9 N to allow stable optical connections to be made under various mechanical and environmental conditions. We also clarify the conditions for a proof test by which to prevent the occurrence of static fatigue fractures in the sleeve, and we confirm the validity of the test. The static fatigue parameters for zirconia ceramics and derived from the static fatigue theory for brittle materials and fracture testing. We use these static fatigue parameters to predict the lifetime of a zirconia sleeve under working stress. An appropriate stress level for the proof test which eliminates weak sleeves, is about 3 times greater than working stress. The strength of the sleeve as demonstrated in the proof test is confirmed by accelerative stress aging. The performance of this sleeve is superior to that of a conventional copper alloy sleeve and the proof test confirms its reliability; under 0.1 FIT for 20 years of use.

High-speed pulse propagation, up to several hundred Mbps or higher, will play an important role in telecommunication systems for B-ISDN. High-performance packaging, especially high-speed, high-throughput interconnection, is strongly required. For advanced telecommunication systems, giga-bit signal transmission has been developed at the multi-chip module level, and 300 to 600 Mbps signal transmission has been reached at the printed circuit board level. Electrical inter-cabinet interconnections of 150 to 300 Mbps have been achieved for up to several tens of meters. High-speed, high-throughput connectors are the key to achieving high-performance telecommunication packaging systems. Two technologies are extremely important. One is for high-density, high-pin-count connectors, and the other is for high-speed signal transmission connectors. The requirements for the connectors needed for advanced high-performance telecommunication systems are described. Several high-density, high-bandwidth connectors developed for high-performance packaging system are introduced.

This paper describes a trial coaxial surface mounted connector for PGA-type high-speed multichip modules (MCM). An MCM connector is needed to ensure testability and connection reliability of MCMs mounted on a printed circuit board. Our connector consists of a coaxial elements, a common ground housing made of conductive resin, and a ground contact spring plate. It has 68 signal contacts. We investigated the performance of this connector by experiment and simulation. Its insertion force is only about 53 gf per signal pin. The characteristic impedance is from 45.6 Ω to 61.4 Ω. The average resistance between two contacts is 28 mΩ with a deviation of less than plus or minus 5 mΩ. The insertion is -0.4 dB at 1.0 GHz. Crosstalk noise is less than 1.2%. This prototype connector can transmit pulses of up to 1.2 Gb/s, showing that it is applicable to high-speed MCMs.

A magneto-optical head lens actuator was developed for use at a high information bit rate and high density recording. A high bit rate at the outer diameter of a 300 mm disk (velocity = 27.3 m/s) was attained by mounting an aspherical plastic lens and optimizing the shape of lens holder for achieving higher spurious frequency over 30 kHz, utilizing the finite element method (FEM). Another approach was focused on reducing gain peak at the natural frequnecy by adopting "multi-wire" and a silicone "gel box" damping system for stabilizing the pull-in characteristic for focusing and tracking. By the actuator realization, a high density recording of 0.34 µm/bit and high information bit rate 80 Mbps (1, 7 code modulation) recording were attained.

Single-crystal LiNbO₃ and LiTaO₃ piezo-electric resonators were developed for surface-mount technology (SMT) used in electronic equipment manufacturing. Using an energy-trapping design, a shear-mode piezoelectric resonator chip is bonded directly to the board with conductive resin and covered with a ceramic cap. The process occasionally produces nonlinear resonators, however, which led us to study the frequency characteristics of impedances for the abnormal samples. Their input impedances at the resonant frequency depended on the driving voltage. The insulator between the thin film metal electrode on the crystal strip or the thick film electrode on the ceramic base, in conjunction with silver balls in the adhesive resin, apparently caused the problem. Assuming that the insulator makes diode contacts, which show stable nonohmic phenonena or cause a discharge in a conductor causing a drastically changing in the impedance, we proposed the following corrective action：subject the nonohmic contacts to a high-voltage frequency-swept signal near the resonant frequency. The samples subjected to the high voltages recovered metalic contact and maintained even after severe thermal cycle testing.

Plating is applied to protect contact surfaces of contact devices such as switch, relay and connector from contaminations of oxidization and sulfuration etc. Furthermore it is known that the contact resistance can be reduced when there exist plated layers on the contact surfaces which have enough thickness and low resistivity compared with substratum materials. In this paper, contact resistance between plated conductors are calculated using three dimensional finite element method. Similariry, current density distribution in a contact spot with various resistivity of plated layers are shown and relative conductance depends on the contact area fraction with thickness of plated layers are presented.

The electric or electronic circuits have many contact devices such as relay and switch. The contact between two nominally conducting flat surface has a lot of micro contact spots. The constriction resistance of the contact is known to determine the sum of the parallel resistance of the micro contacts and the interaction of them. The constriction resistance of two circular conducting spots was approximately formulated by Greenwood. This formulation shows that the interacted resistance of two circular spots is in inverse proportion to the distance between two conducting spots. It was known that this effect is introduced by the interaction between two conducting spots. However, the condition of interaction in the spots is not clear. Calculating the current density distribution in the spots is important to clarify the condition of interaction. The numerical analysis is very suitable to calculate the current density in the spots. In the fundamental case of the computation of the current density the boundary element method (BEM) is more efficient and accurate than that of the finite element method (FEM) because the boundary condition at the infinite is naturally satisfied and is not required a great number of the element in a wide space. In this paper the current density in the square spots is computed by the BEM. As the distance between two conducting spots becomes small, the current density in the two spots decreases. It becomes clear that the constriction resistance of conducting spots is increased by this effect. The decrease of current density by interaction is not uniformly, that at the near location to the opposite spot is larger than that at the far location in the same spot. In this paper the constriction resistance of two conducting spots is also considered. It was known that the constriction resistance of one conducting spot is not influenced by the form of spot very much. However, that of two conducting spots is not clear. The constriction resistance of two square spots is also computed by the BEM. The computed values of the constriction resistance of two square spots are compared with that of two circular spots by Greenwood's formulation and other results. As the result, it is clear that they have the considerable discrepancy. However, the trend of the variations is almost agree each other.

The prediction of a relay contact's life is still very important for support and maintenance of the Crossbar Switching Systems. It was found through surveys and experiments that the protected shower arc is the main reason for switching-relay contact erosion at existing Crossbar Switching Systems, if the contacts were not heavily activated. If the contacts were heavily activated, a long sustained steady arc might occur and severely erode the contacts. This paper proposes an arch energy estimation method for the prediction of contact erosion using object-oriented simulation technology when a steady arc occurs at protected contacts. The arc energy is expressed in a simulation model through analysis, and the model was confirmed through experimentation. The simulation model was used for building block programs of an expert system to predict the life span of switching relays in the existing Crossbar Switching Systems.

On the surface of contacts which are exposed to the atmosphere, the reaction with gases in the atmosphere produces contaminant films including oxides. The contact reliability is degraded by the contaminant films. Humidity in the atmospheric environment also influences on the surface of contacts. However, influence of humidity on the surface has not been clarified. In the present paper, influence of humidity on the Cu surface and the oxides (CuO + Cu₂O) on it were studied with respect to the thickness of the oxide film and contact resistance characteristics both for static and for sliding contacts. The thickness was measured by ellipsometric analysis. Topographic image affected by humidification was also observed by scanning tunneling microscope (STM). In the atmospheric environment, the clean surface of Cu was found to oxidize with fluctuations of the thickness for lapse of exposure time due to the fluctuations of the humidity. It was also found that the thickness of the oxide film decreases immediately after the humidification, and increases under dehumidification. Changes in contact resistance affected by humidity was corresponding to the change in the film thickness. Immediately after humidification contact resistance decreased, and increased with dehumidification both for static and for sliding contacts. For the mechanism of the influence of humidity on the oxide, chemical reduction of hydrogen generated by decomposition of the absorbed water molecule (H₂O) was derived. The clean Cu surface was oxidized by oxygen due to absorbed water molecule and atmosphere.

In clad contacts of bonded dissimilar metals used in relays and switches, the bonding state affects the switching performance of those devices. Examining the bonding state and analyzing the relationship between the bonding state and the causes of malfunction, such as welding of the contact, leads to improvement in reliability of electromechanical devices. In this experiment we examined, with an ultrasonic microscope, the bonding state in riveted clad contacts which had been subjected to load-breaks of in-rush current, and were able to demonstrate the causal relation of the bonding state with malfunctions of the contacts. The use of the ultrasonic microscope made it possible to perform a hitherto difficult detailed analysis of the bonding state of clad contacts. It was also confirmed that this was an extremely effective method for studying the relationship with switching performance.

In this paper, the relationship between contact materials and sticking characteristics, and stability of contact resistance to obtain excellent contacts for telecommunication relays, is studied. The contact switching current for telecommunication relay is low. Moreover, contact force and opening force in these relay are respectively several mN. Nine kinds of contact materials are selected as a experimental factor. They are Ag, Ag-Ni (Ni: 0.03 to 20%), Ag-Cu 10%, Ag-Pd 60% and Pd-Ru 10%, and are overlaid with gold except Pd-Ru 10%. In this study, contact life tests on a commercial ultra-miniature telecommunication relay by mounting above-mentioned contacts are conducted. The sticking and the contact resistance are monitored at each switching operation in the contact life test. After the life test, the contact surfaces are observed, and the depth of crater, the height of pip and projected concave area are measured, then the relationship between the sticking morphologies and the composition of each material are studied. As the result of this study, the contact sticking of telecommunication rely is assumed to be the result of mechanical locking, and the effects of the Ni content in the Ag-Ni contacts is clarified. Moreover, it is confirmed that the effects of opening force on the sticking characteristics are remarkable.

This paper describes a simple system of measuring the spatial distributions of spectral intensities with AgI-421 nm and AgI-546 nm among many optical spectrums emitted from an arc discharge between separating Ag contacts. In order to detect the intensities of two optical spectrums, the prototype equipment has two sets assembled with a CCD color linear image sensor, a lens and optical filters, which are arranged on rectangularity. The intensities of two spectrums can be recorded with 2 ms time-resolution within a long arc duration on a digital memory. The recorded digital signals are processed by using a personal computer in order to reconstruct two spatial distributions of spectral intensities in a cross section of arc column with the Algebraic Reconstruction Technique.

The authors have studied mechanism of transition from metallic phase to gaseous phase in contact break arc. For further elucidation of the mechanism, we have carried out spectroscopic measurement. The spectrum measurement system which had high time resolution was composed using two monochromators and a bifurcated image fiber, which had one input port and two output ports. The input port received the arc light, and the two monochromators received the arc light from the two output ports, respectively. The spectral sensitivity of the two monochromators was corrected with a standard lamp. We have measured simultaneously two spectra of break arc for Ag in laboratory air, under the condition where source voltage E=48 V, load inductance L=2.3 mH, and closed contact current I₀=6 A. As a result, the time-varying tendency of spectrum intensity is similar for the same element, even if the wavelength is different. And from the comparison of time average spectrum intensity, it is clarified that average intensity for gas spectrum does not attain to 10% of that for metallic atomic spectrum (Ag I, 520.91 nm). In addition, the decrease point of Ag II (ion) spectrum has been found to correspond with the peak of Ag I (atom) spectrum.

The former experimental results have already shown that it is oxide films formed on contact surface causing the contact resistance to degrade in dc. breaking arcs for Ag and Pd materials. In order to understand the detailed information about it, the experiments are performed to break dc. inductive load at 20 V, 0.5 A and 1.0 A in nitrogen gas with different oxygen concentrations. The contact surface morphology and surface contamination are evaluated by SEM and AES, respectively. The tested results demonstrate that, for Ag contact, the severe oxidation occurs with increasing oxygen concentration, and the critical value of oxygen concentration is found to be about 10% and 5% in 0.5 A and 1.0 A, respectively, above those values the contact resistance degrades due to the oxide films formed on the contact surface, especially on the anode surface. While, for Pd contacts, a remarkable contact resistance degradation is not found even at 1.0 A in oxigen. Evidence shows that the arc duration, in particular the gaseous phase arc duration affects the anode oxidation, which in turn causes the significant fluctuation of contact resistance.

Arc discharge between electrodes of relays and switches often causes contact surface damage through material transfer and arc erosion. Especially, material transfer sometimes occurs and brings serious failure even under lower load that is quite smaller than the minimum arc current value of contact material. In this paper, contact surface configuration, material transfer, and arc erosion characteristics of Ag and AgPd 60 contacts were experimentally studied after 0.5 or 1 million switching operations at various load levels. The followings can be made clear. Firstly, it was confirmed that the arcs and material transfer occurred even under such current that was lower than the minimum arc current. Therefore, the definition of the arc occurrence boundary current was newly determined. Secondly, the relation between load conditions (current and power supply voltage) and contact surface configuration (craters and pips) caused by material transfer was studied. The arc erosion behaviors of tested samples could be classified into two types: material transfer type and wear-out type. As one of the primary factors of transition from the former type to the latter one, contact activation was considered. The influences of load conditions and organic gas emitted from relay structure on arc characteristics was experimentally examined. The results indicated that load current greatly influenced the amount of material transfer and that power supply voltage affected the occurrence of the wear-out type significantly. The activation behavior of the contact surface could be found through observing the bridge voltage waveform.

Composite materials of solid lubricants, such as graphite, MoS₂, WS₂, etc., and metals are being used as the sliding electrical contacts. However, few reports have so far been presented on the detailed characteristics of such composite materials. It is shown in this report that contact resistance and coefficient of friction of the sliding contact of the composite material of Cu-Nb system against Cu were higher than those of the sliding contact of the composite material of Cu-Sn system against Cu. It was, further, found that composite materials of Cu-Sn system were superior to those of Cu-Nb system being both contact resistances and coefficients of friction lowered. At the same time, it was found that performances of composite materials of Cu-Sn alloy base containing exclusively WS₂ were superior to those containing both WS₂ and MoS₂. It was, therefore, suggested that proper samples suitable for the service conditions should be selected from the composite materials of Cu-Sn system which contain exclusively WS₂ for the practical applications.

The methodology for latchup-free design in bipolar and PMOS merged gates, so-called BiPMOS gates, is considered. Although BiPMOS gates can provide higher switching characteristics than conventional, individually drawn, BiCMOS gates even when the supply voltage is reduced, the general methodology to prevent latchup has been lacking. This paper presents an approximate, but sufficiently correct, mathematical technique to solve the Laplace equation, which gives the distribution of latchup trigger current for the given BiPMOS drawings. It is shown that the resistances of the collector plug and the spreading resistance under the base-collector junction greatly influence latchup, and that the well-emitter overlapping space becomes a problem in the case of a single collector. The distribution of latchup triggering current for the double-emitter double collector NPN transistor indicates the optimum position of the source diffusion area.

We have studied in detail the effect of gas flow rates on the film properties of low-temperature (300) polycrystalline silicon (poly-Si) films prepared by conventional plasma enhanced chemical vapor deposition (13.56 MHz) with SiF₄/SiH₄/H₂ gases. The effect of SiH₄ flow rate on crystallization is shown to be large. A small amount of SiH₄ with high SiF₄ and H₂ flow rates (50[H₂]/[SiH₄]1200, 20[SiF₄]/[SiH₄]150, 1[H₂]/[SiF₄]16) is important to form poly-Si films. The poly-Si films deposited under such optimized conditions had shown preferential 〈110〉-orientation and the crystalline fraction is estimated to be more than 80%. The deposition rates are in the range of 5-30 nm/min. The conductivity is in the range of 10^-8-10^-6 S/cm. Further, the electrical conduction indicates an activation type, and the activation energy is in the range of 0.5-0.6 eV.

Measuring mechanical characteristics of optical disks is significant not only for designing drives but also for assuring disk interchangeability. This paper shows that the lens-movement detection method has the greatest overall potential and thus fits to a practical system for measuring mechanical characteristics. A system based on this method was constructed by developing simple and accurate capacitive sensors that can be built into an optical head to detect lens movement. The system configuration includes a precision turntable and a high-duarability reference disk to fully extract the potential. Test results show that this measuring system has adequate measuring range, accuracy, and stability. Some applications of this system are described in this paper. They show that the system is useful for evaluating and improving optical disk mechanical characteristics.

This paper describes a high-density, high-pin-count flexible SMD connector used for high-speed data buses between MCMs or daughter boards. This connector consists of a flexible film cable interconnection with accurately controlled characteristic impedance, and a contact housing composed of double-line contacts and SMD type leads. It has 98 contacts each with a pitch of 0.4 mm. The connector mounting area is 6 mm wide and 23 mm long. The flexible cable has a double-sided triple-parallel micro stripline structure with an insertion force of less than 2.9 kgf and characteristic impedance of 48 to 50 Ω. Insertion loss is -0.5 dB at 600 MHz and crosstalk noise is less than 110 mV at 250 ps rising time. This connector can be used for high-speed data transmission of up to 300 ps rising time.

Experimental optical gain characteristics of an erbium-doped fiber amplifier have not been explained well by conventional laser schemes in the case of two-channel amplification. Modified simple laser schemes including cross relaxation among degenerate levels were valid for the explanation of the optical gain dependence on input signal power and on the erbium-doped fiber length.

We predict that chemical waves can propagate as a guided mode in a reaction-diffusion system that consists of two regions with different wave speeds. In comparison with electromagnetic waveguides, unique features of the guided chemical waves can be seen in their dispersion characteristics. Conditions for supporting lowest-loss guided waves are discussed.