Papers by Author: Katsuaki Suganuma

Abstract: Heat-resistance of novel mold compound made of silsesquioxane nanocomposite with silica fillers is demonstrated in a TO247 package of SiC SBD. The test specimens are exposed to thermal cycling between -50°C and 250°C, and the thermal damage of the mold are precisely evaluated by using nanoscale dynamical mechanical analysis based on nanoindentation technology. The results reveal that the excellent heat-resistance is brought by the miscibility between the thermosetting nanocomposite and silica fillers.

Abstract: The electronic packaging has developed in the changing trend from soldering to solderless technology bonding to achieve higher performance of devices. Moreover, power electronic devices have searching for an alternative interconnection technology to replace the high temperature solder with high Pb contents, particularly suitable for next-generation wide band-gap (WBG) semiconductors such as SiC or GaN. In this study, our pressureless Ag thin-film die-attach gives an opportunity to produce the mass production by realizing low-temperature process. We demonstrate the pressureless Ag thin-film die-attach with Si and SiC to explain the mechanisms underlying the bonding process. The variation of the substrate material modifies the thermal expansion mismatch between sputtered Ag film and the substrate, and changes the bonding property, in particular die-shear strength. We reveal that the thermal stress generated by heating plays one of key roles to control the pressureless Ag thin-film die-attach process.

Abstract: Applications of various noble metal nanoparticles were investigated for newly, ecology and economy home electric appliances (microwave, ultrasonic) used system. Noble metal oxides have merit in metal particles fabrication, as one of these example example, there are decomposed by only heating in air. That is, noble metal oxide don't use strong reduction atmosphere. This reduction is ecologically clean, because many noble metal oxides are not toxic and during decomposition O2 is evolved. We have reduced noble metal oxides by microwave and ultrasound, and tried to fabricate noble metal nanoparticles, and investigated various processing. These energy are widely used by home electric appliances. By choosing suitable process and conditions, it is reasonable to expect that home electric appliances ecology and economy fabrications can be extended to obtain simply various noble metal nanoparticles related materials.

Abstract: We have developed a novel technique of joining a pair of glass substrates. In the process, molten solder penetrates the gap between the glass substrates while the solder-glass interfaces are being activated by friction. The activation is given by a metal plate, which slides through the gap along the edge of the paired glass substrates and brings in the molten solder by capillary-action. A Ti-doped Sn-Zn eutectic solder showed good hermetic sealing of glass. A eutectic In-Sn solder also yielded good joining, especially at low sealing temperatures.

Abstract: β-tricalcium bis (orthophosphate) [Ca3(PO4)2] (β-TCP) was mechanochemically treated with mortar grinder. The ground β-TCP was hydrolyzed in an aqueous ammonium solution (pH=11.0) at 90
to give Ca-deficient HAp involving small amount of CO3 2- ions. With an increase in grinding time of β-TCP, it was hydrolyzed easily. Well-crystalline Ca-deficient HAp was obtained after grinding of β-TCP for 7 hours and the successive hydrolysis.

Abstract: Calcium phosphate-AMP layered material was synthesized by the hydrolysis of α−TCP in the presence of AMP at pH=6.2. The resulting composite was a mixture of DCPD and calcium phosphate-AMP layered material. The composition and structures of the calcium phosphate-AMP layered material were estimated based on elemental analysis, thermal analysis, and spectroscopic analyses. About 30 wt% of the composite comprises AMP, which is oriented in alternately layered structure of AMP and calcium phosphate layers. Furthermore, the composite showed better cell adhesion than DCPD.

Abstract: Nano-sized metal particles have recently attracted considerable interest owing to their application potential. Such particles can be synthesized using physical and chemical methods. In this study, nano-sized noble metals were synthesized through the reaction of metal oxides by ultrasonic. This means that the chemical reactions which take place under conventional conditions can be accelerated by ultrasonic cavitations. In general, the chemical effects of ultrasonic irradiation fall into three areas: homogeneous sonochemical efffects of liquids, heterogeneous sonochemical effects of liquid-liquid or liquid-solid systems, and sonocatalytic effects. It has been proposed that liquid-liquid systems are used for the fabrication of nano-metal particles in the past. In this study, the fabrication of nano-metal particles and supported composites was investigated for the liquid-solid system from a viewpoint of economy and ecology. By choosing suitable conditions, it is reasonable to expect that these simple ultrasonic processes can be extended to obtain nano-sized metal particles. Thus applications by using these reactions were investigated to prepare the nano-sized metal particle supported materials, and mechanisms were investigated.

Abstract: Applications of silver nano-sized metal particles were investigated for a new, ecologically friendly and economical liquid-solid (silver oxide-alcohol) system. Silver metal oxides as starting materials have merits in metal particles fabrication because these materials are decomposed only by heating in air. That is, noble metal oxide does not use thestrong reduction atmosphere. This reduction is ecologically clean because many noble metal oxides are not toxic, and because O2 is evolved during decomposition. We reduced silver metal oxides by ultrasound and fabricated silver nano metal nanoparticles at room temperature, and various applications were investigated. By choosing a suitable process and conditions, it is reasonable to expect that ultrasonic eco-fabrications can be extended to obtain various silver nano-particles containing materials.

Abstract: To clarify the effects of parameters of porous ceramics form on the characteristics of composites fabricated by high-pressure infiltration, Alumina forms with different porosity (15~70vol %) and pore morphology were fabricated by Freeze and Dry Process and Partial Sintering Process. Alumina/aluminum composites were made by the squeeze casting. The composites contained the different volume fraction of aluminum depending on the initial porosity of the ceramics form. The coefficient of thermal expansion (CTE) and thermal conductivity of composites were measured. The results indicated clearly that variation of the structure of porous ceramics form fairly affected CTE but the effects on thermal conductivity were small.