The growth kinetics of intermetallic compounds formed on the boundary between Au and In-48Sn solder was researched with diffusion couples. On heating under the melting point of In-48Sn solder, the AuIn₂ layer was firstly formed on the boundary and grew toward the solder layer. Simultaneously, the γ layer was formed on the boundary between AuIn₂ layer and solder layer. On the other hand, the AnIn₂ layer, which was firstly formed, finally changed to the intermetallic compounds of Au-Sn system in heating over the melting point of that solder. That reaction was possible to be explained by the diffusion path described in the Au-In-Sn phase diagram. As the result of the Arrhenius plot for the growth rate constant, the activation energy of the growth of AuIn₂ was estimated at 42.8kJ/mol.

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Novel OLB technology onto PWB at 0.15mm lead pitch by means of soldering method has been developed. This technology includes two types of OLB structures which can be adopted for many kinds of applications. One is a lead-forming type in which leads are bent in the shape of gull wings, and the other is a non-lead-forming type. In the technology, the outer leads are connected to the PWB electrodes only with electro-plated solder on the outer leads, through non-cleaning process. It was confirmed that the samples using the developed tech-niques showed good results in terms of reliability and this OLB system proved to be a practical use level.

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When film or paste of an organic adhesive material, in which metallic balls or flakes of approximately 5μm in diameter have been dispersed, is used as an electrical connection material, the electrical junction is considered to be free from causing environmental pollution and capable of finer-pitch connection than the conventionally-used solder joint electrical connec-tions, and thus has attracted attention. In the past, do resistance has been well verified, and its problem is thought to have been solved. However, in spite of the fact that it is the junction where high frequency pulse signals flow in real applications, its high frequency characteristics have not been verified. The purpose of this study is to make actual measurement of the transmission characteristics of high frequency pulses through this junction and verify the practica-bility of the connection method. Applied pulse was of 2ns rise and fall time. When the peak voltage of the pulses was going down, the interconnection would be unstable in sometime, where points were measured. From this measurement data, it was found that conductive paste would show high-frequency transmission characteristics (over 100MHz) that are trou-ble-free with respect to the connection mesh like network having distances of 50μm or so. The reason for the stability despite the large number of contacts chained together can be deduced from the action of mechanical compressive force due to the resin filling, which resulted in the stable existence of each contact as a metallic (ohmic) contact.

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We have developed B²it^TM (Buried Bump interconnection technology) printed wiring boards (PWB's) for high density and high performance wiring boards or substrates. Ordinary PWB's have low thermal conductivity because of their organic materials, compared with ceramic substrates and so on. The B²it^TM PWB's have filled via holes by silver paste bumps to connect wiring lines between neighbor layers. The feature is different from ordinary PWB's having copper-plated through holes. This paper reports the thermal management properties for the B²it^TM PWB's by measuring the thermal resistance of several filled via hole situation. And a thermal conductivity of the via hole material was simulated from the measurement values. As the results, the thermal conductivity of the via hole was very high to compare with that of the normal printed silver paste, and the B²it^TM PWB's had good thermal management property enough to high density packaging.

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High performance build-up type multilayer boards with BVH were developed and we started producing them in mass production. They have blind via holes on surface to connect 1-2 layer and/or 1-3 layer. Also, they can have buried via holes to connect between inner layers. Laser drilling technology, which is one of important technologies in the process, was investigated.

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