Takeo Tomiyama

Rewritable optical-disk fabrication with an optical recording material made of naphthalocyanine and polythiophene

A novel rewritable optical disk that uses an optical recording material made of naphthalocyanine and polythiophene as the recording layer is described. In this system the complex refractive index of the recording material changes reversibly, depending on the aggregation states of naphthalocyanine induced by a conformation change of the polythiophene matrix. After recording, the imaginary part of the refractive index of the recording material increases to three times that of the unrecorded part, at a wavelength of 790 nm at which a semiconductor laser emits light. The fabricated polythiophene naphthalocyanine optical disk shows a high reflectivity of 58% and a large readout modulation amplitude (I(11)/I(top)) of 0.63. It is confirmed that the polythiophene/naphthalocyanine optical disk can be played back on conventional compact-disc players even after ten cycles of rewriting.

Material system for high performance DRAM-CSP

The /spl mu/BGA/sup (R)/ which Tessera Inc. developed is one of the most suitable chip scale packages (CSP) for high speed DRAMs. However, the larger the chip size, the harder it is to achieve high levels of package reliability. Based on the thermal stress analysis, we have determined the threshold values of elastic modulus and coefficient of thermal expansion (CTE) of both the adhesive film and the liquid encapsulant to achieve higher thermal cyclic properties. Through this study, we have developed new polymer alloys composed of a low modulus polymer and an epoxy resin. CSPs fabricated with the newly developed materials showed high reliability including thermal cyclic properties and solder reflow resistance at high temperature under Pb-free requirements.