Study on effect of drilling rotational speed and tool wear on chip evacuation of micro drilling of printed circuit board

Abstract

In recent years, needs for micro drilling are increasing, accompanying the development of higher wiring density of printed circuit board (PCB). When drilling PCB for the purpose of making the electric through holes, it has been said that the drill breakage is caused by being filled the chips of GFRP and copper of PCB in the drill flutes. Series of drilling tests of PCB have been carried out to investigate the shape of chips produced and the chips evacuation behavior out of drilling hole of the drill at the rotational speed of from 20×10³min^-1 to 160×10³min^-1. The chips evacuation behavior out of drilling hole of the drill is filmed by a high-speed motion camera and the shape of chips produced is observed by a microscope. The chips of GFRP are short and small pieces with an increase in the drilling rotational speed. The evacuation out of drilling hole of the drill is very well and both of maximum cutting torque and average cutting torque are decreasing with an increase in the drilling rotational speed. When drilled at rotational speed of 160×10³min^-1, the chips of GFRP are long and large pieces, on the other hand, the chips of copper are short pieces, and chips evacuation out of drilling hole of the drill is almost not worse with an increase in the tool wear.