Evaluation of Drilled Hole Quality as a Function of Speed and Feed in Multilayer Boards

Studies of the drilling process have shown that a direct correlation exists between the quality of a drilled hole and the energy expended by the drilling system in forming the hole. As the drilling energy increases (for a given board and drill) the quality of the hole decreases. Hence drilling energy can be used as a measure of drilled hole quality. A drilling energy monitor which can evaluate drilled hole quality on line is being used to investigate several aspects of the drilling process. One of these studies, the effect of feed‐rate and spindle speed on drill performance is the subject of this paper. Drilling energy as a function of drill age has been investigated at several combinations of feed‐rate and spindle speed. No. 56 drills were aged in 8 layer multilayer boards for up to 3000 holes while monitoring the drilling energy. Spindle speed was varied between 60 and 300 inches per minute. It was found that the rate of increase of drilling energy is lower for drills worn at a high advance per revolution than for drills worn at a low advance per revolution. Longer drill life can be obtained by drilling at a high advance per revolution. Spindle speed had little effect on the rate of increase of drill energy over the range of feed and speed used in this study. This paper presents the experimental data and makes recommendations on the proper usage of No. 56 drills.