With the evolution of power device elements, there is a demand for bonding materials that can bond devices with low thermal stress and realize high heat resistance bonding that supports high temperature operation. We propose a new bonding material that achieves high heat resistance in a low-temperature, short-time process by using metal fine particles and based on the characteristics of fine particles and the concept of liquid-phase diffusion bonding. In this study, we investigated the relationship between the metal composition in the bonding material and the bonding strength for bonding materials using SnBi and Cu, and reported that the particle structure affects the formation of the bonding layer.

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Localized, quick, and non-contact soldering technique has been required for soldering leaded components to printed circuit board. In order to satisfy these requirements, induction heating （IH） soldering technique was studied. In the case of conventional iron soldering, many factors affecting heat loss in the heat pass from heat source to component lead exists. On the other hand, in the case of IH soldering, component lead can be directly heated by IH. Therefore, adopting simulation technique for IH soldering is reasonable. Using the thruhole - lead model, heating power of IH heating was calculated by magnetic simulation. Joule loss densities of the IH soldering model were calculated. Skin-depth effect in component lead during IH soldering was confirmed by the calculation. Temperatures of component lead were also calculated from joule loss density. The calculated temperatures agreed with observed temperatures of component lead during IH soldering.

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The authors developed a test system to easily measure the fatigue life of wire bonding. The test specimens were prepared by bonding Al wires onto Al electrodes with current applied and voltage measured area. By applying a 10 A square-wave current to them, the current application path was heated and a repetitive thermal load of 110－240℃ was applied to the wire bonding part. At the same time, we attempted to measure the thermal fatigue nondestructively by measuring the resistance change ratio（ ΔR/R₀） of the wire bonding part using the 4-terminal method. As a result of the verification, it was found that Δ R/R₀ and crack length of wire bonding parts are closely correlated. Then, the observed fatigue lifetime was close to those predicted from conventional thermal shock test results. These results indicate that the developed system is a reasonable lifetime measurement technique and that this system has the potential to efficiently collect the fatigue life of wire bonding, which is necessary for the reliability design of power devices.

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Improving the electrical conductivity and reliability is a critical issue for developing copper-filled electrically conductive pastes that are expected to alternate the conventional silver-filled pastes in the electronics packaging field. This work investigated the effect of surface treatment through amino ethanol and its derivatives on copper fillers to improve the electrical conductivity and reliability of copper-filled electrically conductive pastes composed of a resol-phenolic resin binder. The amino ethanol surfactants effectively accelerated the electrical conductivity development in the pastes during curing, increasing the magnitude of the acceleration effect with the number of terminal hydroxyl groups. Although using amino ethanol surfactant alone could not improve the electrical reliability during exposure to a humid environment, co-treatment with oleic acid enhanced the reliability. By contrast, introducing a terminal amino group to the surfactant improved electrical conductivity and reliability. The chemical behavior of copper complexes formed by the interfacial reaction during the surface treatment is needed to clarify the mechanisms of enhancing electrical conductivity and reliability. This means control of the interfacial chemistry will be essential for developing advanced copper-filled conductive pastes.

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We investigated a method of copper plating on glass substrates wit h high smoothness and insulation properties and excellent transmission characteristics, while maintaining the smoothness of the substrate. The tin oxide deposited by the liquid phase deposition method acts as an adhesion layer between the glass substrate and the plating film, which was obtained to copper plating film with excellent adhesion. In this report, we discuss the microstructure of the plating film interface where high adhesion is obtained.

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We have tech nology to manufacture copper nanoparticles by dry process. In this study, we investigated the basic characteristics of transfer bonding sheet using our copper nanoparticles with the goal of developing transfer bonding sheet that can be transferred to the same size as SiC and can be bonded at low temperature （250℃ or less）. As a result, transfer bonding sheet with shear strength of 70 MPa or more was produced under the bonding conditions of 250℃, 10 MPa and 5 min in nitrogen atmosphere.

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In electronic devices, a crack initi ation and propagation of solder joints lead to failure. A cross-sectional observation and bonding strength test （pull or shear） are often carried out to confirm whether a crack exists or not. However, it has been known that bonding strength of solder joints depends on various factors so that it is unidentified the condition of a crack contributes to the value of strength. In this study, we obtained a 3-dimentional crack structure from X-ray CT data by using deep-learning technique before pull strength test and investigated their correlation.

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Soldering technique using formic acid is being applied to power module’s assembly process, but detailed research on this process has been few reported. This paper presents the results of basic evaluation focusing on the gas generated by chemical reduction with formic acid atmosphere and reduction rate. It was observed that a compound of formic acid and tin oxide was formed at 150℃, and the compound was decomposed into hydrogen and carbon dioxide at 180℃ or higher. Furthermore, it was found that the chemical reduction rate of tin oxide is proportional to the temperature and concentration of formic acid if the amount of formic acid is more than the amount of oxide, but it does not increase if the amount of formic acid is less than the amount of oxide.

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Many studies have examined electromagnetic shield packages for preventing electromagnetic interference, and several have discussed adhesion between the mold resin and the electromagnetic wave shielding film. In this study, we investigated the interfacial behavior between mold resin and sputtered stainless steel film as an electromagnetic wave shielding film. Two mold resin samples with different amounts of SiO₂ filler formed on an organic wiring substrate were plasma etched with different gas flow ratios of Ar and N₂. After etching, stainless steel film and Cu film were formed on the mold resin by sputtering. Adhesion was evaluated by the crosscut method. The results showed that adhesion between the mold resin and the sputtered stainless steel film improved as the exposure of the SiO₂ filler increased and as the N₂/（Ar + N₂） gas flow ratio in the etching gas was increased. As the N₂/（Ar + N₂） gas flow rate ratio increased, the amount of resin etched increased, exposing more SiO₂ filler. XPS analysis showed that this increased adhesion by enabling polar interactions between metal atoms and amino group nitrogen atoms. IR reflow after moisture absorption decreased the amount of nitrogen at the interface, breaking the metal-nitrogen polar interaction and oxidizing the metal, resulting in reduced adhesion.

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