High-Temperature-Resistant Interconnection Using Nickel Nanoparticles

The bonding characteristics of nickel nanoparticles as a new alternative bonding material for high-temperature soldering was considered and a high bonding strength was achieved at a bonding temperature of 300°C. It was also revealed in a bonding experiment using a silicon dummy chip with a deposited aluminum layer that direct bonding to an aluminum electrode was possible. On the other hand, a stress-relaxation structure using a metal film was presented as a new structure for resolving the problem of deteriorating bonding reliability due to thermal stress arising from differences in the coefficient of thermal expansion between the chip and the substrate. A silicon carbide device was assembled using the new bonding method and an operating test was performed to verify normal operation in a high-temperature environment of approximately 300°C.

STABILITY OF STEADY SOLUTIONS TO REACTION-HYPERBOLIC SYSTEMS FOR AXONAL TRANSPORT

We are concerned with the stability of steady solutions to the initial and boundary value problem associated with reaction-hyperbolic systems for axonal transport. Under proper structural assumptions, we clarify the relaxation structure of the reaction-hyperbolic systems and establish the large-time asymptotic stability of steady solutions and relaxation boundary-layers.

Oxygen Diffusion in Ti-20Mo Alloys, Used as Biomaterial, Measured by Mechanical Spectroscopy

Titanium alloys are favorable implant materials for orthopedic applications, due to their desirable properties such as good corrosion resistance, low elasticity modulus, and excellent biocompatibility. The research on titanium alloys is concentrated in the β type, as the Ti-20Mo alloys and the addition of interstitial elements in these metals cause changes in their mechanical properties. The mechanical spectroscopy measurements have been frequently used in order to verify the behavior of these interstitials atoms in metallic alloys. This paper presents the study of oxygen diffusion in Ti-20Mo alloys using mechanical spectroscopy measurements. A thermally activated relaxation structure was observed in the sample after oxygen doping. It was associated with the interstitial diffusion of oxygen atoms in a solid solution in the alloy. The diffusion coefficient for the oxygen diffusion in the alloy was obtained by the frequency dependence of the peak temperature and by using a simple mathematical treatment of the relaxation structure and the Arrhenius law.