In recent years, electronic devices have demanded higher density of interconnection and packaging, since many electronic equipments have become downsized and multifunctional. Generally, organic materials are used as the insulating element of Printed Circuit Boards (PCBs) and packaging components in electronic instruments. The formation of conductive layers for wiring on these insulators is a key technology. In particular, the formation of a metal conductive layer with excellent adhesion is demanded for the manufacturing of fine-pitch PCBs. In addition, the formation of smooth conductive layers will be required for fine-pitch PCBs in the near future. We studied the formation of conductive layers on smooth insulation resin without the need for roughening of the insulation resin surface by conventional oxidizing agents. Chemical modification on the insulation resin can be achieved by UV light irradiation in the presence of TiO₂. Carbonyl groups are formed during the treatment. We confirmed that the modification of the insulation resin surface improves the adhesion between deposited copper and resin. Adhesion strength of 1.17 kgf/cm on plated copper films has been obtained, even on a smooth insulation resin surface, without roughening.

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For the panel plating process, the whole panel is initially electrodeposited with copper and after applying thin photo resist film, the fine conductor lines are chemically etched. Uniformity of copper thickness is a critical factor to achieve fine etching of the conductors. However, thickness of electrodeposit is originally higher at the panel edge, which often makes fine line etching difficult. In this report, the panel holders at the panel surroundings was modified in order to obtain the uniform copper thickness. Current distributions on the panel was simulated by the secondary current distribution by changing the insulating area and shape of the cathode holder (convexity) . Less than 1.0 percent minimum current nonuniformity was achieved by insulating the convexity from the cathode side including convexity sidewall. The higher and the longer the convexity, the copper thickness uniformity was improved. The results were applied to the actual panel plating machine and a drastic improvement of 2.98 percent maximum current non uniformity was achieved.

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This paper investigates the thermal properties, including the thermal conductivity and linear thermal expansion coefficient, of isotropic conductive adhesives (ICA) containing Cu filler particles. For randomly dispersed filler particles, it was shown that the thermal conductivity of the ICA agrees with that given by Kanari's equation, which is derived from Bruggeman's equation by generalizing the shape parameter of the filler particles. Furthermore, the effect of voids can be taken account into the theoretical analysis of the thermal conductivity by additionally applying Bruggeman's equation or Kanari's equation for a composite structure composed of a void and filler/adhesive matrix approximated as a mean-field. The linear thermal expansion coefficient of the ICA was characterized using a rule of mixture proposed by Schapery. The thermal expansion coefficient of ICA with a low volume fraction of filler particles agrees well with Schapery's upper limit. As the volume fraction of filler particles increases, the linear thermal expansion coefficient tends to approach Schapery's lower limit.

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The strength of micro solder joints was experimentally investigated under combined tensile and torsional loads. A new testing equipment for the combined loads was constructed to investigate to strength of micro solder joints. The testing specimen was prepared using a single solder ball according to the BGA model. The strength of the micro solder joint specimen was measured under various combined loading conditions. The load is applied to the joint specimen at higher strain rate than the steady state creep rate to reduce the effect of creep deformation on plastic deformation. The solder joint strength under combined loads at room tempereture was higher than that expected by the von Mises Criterion. But, at 100°C, the joint strength coincided with the Mises criterion.

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In this paper, the effect of hardening rule on stress and nonlinear strain estimation for lead free solder joint is examined using mechanical fatigue test and FEM analysis. From the results of mechanical shear cyclic test, it turns out that Sn-3.5Ag-75Cu and Sn-8Zn-3Bi solder show remarkable hardening characteristic of kinematic hardening. Based upon the FEM analytical results with mechanical and thermal cyclic loading conditions, it is shown that the hardening rule may cause 15% error at the most in evaluation of non-linear strain in solder joint and this degree of error will not significantly affect the fatigue strength evaluation of solder joint. And the error of maximum stress in solder joint between the both hardening rules increases to 40% for the mechanical loading case. However, the error in the evaluation of stress and nonlinear strain is 10% or less, when elasto-plasticity and creep analysis in which considered the kinematic hardening law in loading and holding time, but the creep only in holding time is carried out.

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The RF characteristics of multi-layered chip directional coupler comprised of LTCCs were successfully calculated on the basis of equivalent circuit. The main and sub electrode lines were coupled with the magnetic coupling coefficient of 0.2 or less. A LTCC consisting of non-magnetic and low-dielectric material was adequate for the directional coupler.

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We have succeeded in forming high aspect ratio nickel bumps. The high aspect ratio of 0.66 nickel bumps have been obtained with additive of Coumarin in Watt-type bath and with 0.5μm thin photo resist. This 0.66 aspect ratio is more than twice as high as previous results. The outer surrounding diffusion of Coumarin inhibits the outer surroundings of bump forming cathodes and forms hump at the center. This inhibition effect depends on the thickness of photo resist. The thinner the photo resist the higher the aspect ratio of bumps. The obtained high aspect ratio bump is suited for flip chip interconnection and also for probers.

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