Practical formula for predicting drill wear in micro-drilling of printed circuit boards containing high hardness fillers

This paper describes micro-drilling processes for Printed Circuit Boards (PCBs) containing fillers with high hardness and high thermal conductivity. Powered primarily by devices such as digital cameras, laptop computers, and wireless communications devices, current the electronics field today is continuously demanding smaller, lighter, and more technologically advanced high performance devices. It has been a problem from such a tendency that the increase in amount of semiconductor-generated heat has a undesirable influence on such devices. Additionally, from a viewpoint of environmental problems, electric vehicles and LEDs are developed actively. One of the principal components for building such devices is Printed Circuit Boards (PCBs). In recent years, PCBs containing alumina fillers with high thermal conductivity have been developed and begun to be widely used. However, when processing these PCBs, the drill tools severely wear because of the filler's high hardness. We therefore examined the drill wear characteristics and derived the practical drill wear formulas from the results to develop a suitable CAM system. It can be seen that these equations are similar to Taylor's tool life equation. We also investigated the thermal conductivity effect on temperature during drilling processes. The temperature around the drill hole was shown to be a complex phenomenon according to increasing filler content to PCBs.