the tooling and process techniques for hand-punching holes in green (unfired) 99.5 percent alumina ceramic substrates were investigated to determine the requirements for obtaining holes with good surface finish and a minimum number of defects. such holes are needed to provide low electrical resistance ground paths from frontside to backside of vacuum-metallized ceramic substrates used to manufacture hybrid microcircuits. it was determined that holes having excellent surface finish and maximum via resistance of 9 m omega (with a 6 mu m surface thickness of chromium/gold metallization) could be obtained with the following processing and tooling: use heat-treated drill bushings to line the template holes; use a conical-tipped punch; use oil as a lubricant; spin the punch approximately five revolutions during the punching operation; and blow compressed air through the hole after punching. the as-fired hole diameter should be approximately 78 percent of the nominal punch diameter. (era citation 02:005589)