Conventional printed circuits have been manufactured by using etching technologies. In recent years, printed electronics has been attracting attention as an alternative method. This technique is performed by a simple process of applying a conductive paste to a solid substrate and sintering. Due to the recent energy situation and in order to use a flexible polymer substrate, sintering at a lower temperature in a shorter time is required. In this paper, copper nanoparticles stabilized with alkylcarboxylic acid, prepared by a liquid-phase reduction process is proposed. The paste of these copper nanoparticles were successfully prepared by using a bead mill. The product films sintered under 3% hydrogen / nitrogen mixed gas showed a good volume resistivity of 5.1×10^-6 Ω・cm. Conductivity was also confirmed with the product sintered under nitrogen, but the surface oxidation of copper nanoparticles limited the necking growth of the nanoparticles.

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 The reductive solvents for Cu sinter paste were successfully de veloped. The solvents generate reductive gas by heating, and temperature of reducing gas’s generation from the solvents can be controlled. Designing the stability and sinterability of Cu paste can be modified by the selection of solvents. The Cu paste using reductive solvents can sinter at 180℃ for 5 min in N₂ atmosphere, and the sintered body’s electrical resistivity is very low（11μΩ・cm）. The factor of sinterability is expected to be obtained by generation of Cu nano particles in Cu paste with solvents. The Cu paste using reductive solvents can be applied to bonding materials. The Cu paste can make Cu-Cu joints by void-less and crack-less sinter layer by pressure sintering process.

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 The technology for manufacturing electronic devices by the printing method （PE: Printed Electronics） has been energetically studied in recent years as a next-generation electronic device manufacturing technology. Among them, the ceramics coating technology by the solution process is a functional material. It is attracting a great deal of attention as a next-generation energysaving, resource-saving, and low-cost process used as a thin film. In this paper, we explain the coating technology of nano-thin films and nano-structured thin films by metal organic decomposition （MOD） method for electronics applications such as buffer layers of solar cells and gas sensors, and so on.

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 Integration of flexible electronics into the living system is expected for advancing medical diagnostics and therapeutics. Such devices should be conformable to the physical and mechanical environment of our body, in which acquired biosignals should be wirelessly transmitted to external device. In this regard, we envisage ultra-flexible wearable or implantable devices based on the polymer nanosheet technology. The polymer nanosheet shows tens- to hundreds-of-nanometer thickness close to the scale of biomembranes, in which various types of polymers （e.g., biodegradable polymers, conductive polymers, and elastomers） are formed into the ultra-thin structure. The free-standing nanosheet showed flexible and adhesive properties derived from ultra-small flexural rigidity. In this study, the development of nanosheet （or thin film）-based electronics is introduced by combining nanosheet and printing technologies. The nanosheet electronics has been utilized as tissue-interfaced electronics to direct biosignals or functions for advanced medicine and health-care applications.

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Ag sinter joining has attractive attent ion as a promising process for the electronic packaging to realize high reliable joints. However, Ag sinter joining to Cu material, which is used as direct bonded copper substrate, sometimes involves the degradation of joint properties after thermal storage test owing to the excess progress of Ag sintering. In the present study, we evaluated the heat resistance of the Ag-Cu hybrid sintering to Cu substrate prepared by the mixture among Ag₂O, Cu microflakes and polyethylene glycol. Simultaneous X-ray diffraction and differential scanning calorimetry measurements showed that the joining could be achieved for the joining temperature below 300℃ with little oxidation of Cu. Thermal storage test at 250℃ showed the improved shear strength and the robustness for the hybrid sintering even at the joining temperature at 240℃ compared to the Ag sintering at 300℃. Microstructural observations revealed that Cu oxides on the Cu substrate grow through not only the oxidation of Cu substrate, but also the aggregation of oxidized Cu flakes by the thermal storage test under the air ambient, which is influenced by the preferential progress of Ag sintering. It was supposed that the gathering of those Cu oxides led to the formation of micropores, which is usually formed in the vicinity of the interface between oxide layer and the substrate, inside the oxide layer, contributing to obtain the high heat resistance and robust joints.

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