Yasushi Kumashiro

Development of cell gap spacer in LCD for ink-jet printing

We have developed the novel ink material for the ink-jet fabrication of the cell gap spacer in LCD. We applied the thermosetting resin to the ink for the gap spacer with the concept of forming the bead-less spacer. The thermosetting resin was solved in the organic solvent to enable jetting. And it formed the centroclinal-shape as the gap spacer through the printing and drying processes. We evaluated the influence of the cure rate of the resin and the surface tension of the ink on the shape of the gap spacer. It became clear that the faster cure rate of the resin made the shape of the gap spacer flat. And the surface tension of the ink and the surface free energy of the substrate had the effect on the shape of the spacer. In consequence, the average height of the gap spacer was to be controllable and the standard deviation of the height was less than 0.03 mum.

Epoxy adhesive sheet with copper foil for multiple IVH build-up technology

The interstitial via hole (IVH) structure, in which the interconnections of signal layers are designed with nonthrough holes, is strongly focused to meet the need for small and high-performance electronic equipment with thinner and high wiring density multilayer boards (MLBs). A new epoxy adhesive sheet with copper foil was developed for multiple IVH build-up technology. Since no glass cloth is used for reinforcement, the adhesive sheet allows IVH structure fabrication by CO/sub 2/ laser ablation. It has superior resin flow properties for filling both inner-pattern and inner-layer IVH structures. The surface flatness of the build-up layer with this new sheet allows very fine wiring patterns on to be fabricated. This sheet, which does not concave during the wire-bonding process since its surface is hard at high temperature, is suitable for MLBs with semiconductor chips. This material is effective for manufacture of thin MLBs with IVH structure and high wiring densities.

Investigation of Low-Cost Copper Interconnection Cleaning Using Hydrogen Radicals Generated by Heated Catalyst

We investigated hydrogen radical copper cleaning via the hot-wire method using only a rotary pump for the vacuum exhaust system. The copper oxide surface was successfully reduced. The treatment also increased the resistance of copper to oxidation.