Abstract
As integrated circuits continue to be miniaturized, the penetration holes of bonding jigs have also become smaller. However, micro-drills have a tendency to break drilling small holes with high aspect ratios. Moreover, to reduce the impact on the environment, there has been a recent trend towards the use of lead-free brass as jig materials, and these are very difficult to drill. In the present research, small holes were drilled in lead-free brass using a micro-drill, and the influence of web thinning, the helix angle and the nick geometry on chip evacuation was investigated. The results indicated that a drill with a helix angle of 15° exhibited a long tool life. The formation of a nick on the cutting edge was found to be effective in decreasing the thrust force during deep drilling. A drill with a relatively shallow nick perpendicular to the cutting edge had excellent chip discharge performance, and its cutting force was stable. Nick treatment is effective in decrease of a thrust force at a deep drilling position.
