Ceramics with many micro holes are used as MCP (Microchannel Plate) for electron amplification, catalytic converters, filters, electrical insulators and thermal conductors in integrated circuits. However, ceramics with many micro-holes have been employed only for high performance and compact electrical equipments because of their high fabricating cost. The conventional wire drawing method of fabricating micro-holes in ceramics has low productivity because of their high hardness and brittleness.
In this work, micro holes of 200 micrometer for micro channels were drilled in alumina green body using a high speed air turbine spindle of 150,000 RPM because the alumina green body composed of alumina powder and epoxy binder could be more easily drilled than sintered alumina itself. The micro-drill was composed of tungsten carbide shank and diamond grits that were nickel-electroplated. The machinability and surface quality of drilled holes of the alumina green body were experimentally investigated with respect to feed rate and lubrication conditions. The tool life of the drills were measured by optical and SEM microscopes and the drilling force variation during the micro drilling of the alumina green body were measured using a tool dynamometer.. The sintering of the micro drilled green body resulted in the shrinkage of diameter of micro-holes, which was another advantage of reducing the size of micro holes. The shrinkage of alumina ceramics during sintering was also measured.
From the experimental measurement of surface quality of drilled holes, tool life of micro drills as well as the productivity of hole drilling, it was concluded that the developed micro drilling method using micro drills and high speed air turbine was competitive with the conventional wire drawing method.
