Study on cutting temperature 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 surface quality of PCB hole wall is affected by drill temperature. The aim of this study is to clarify the effect of depth of hole, tool wear and chip evacuation on temperature on surface of PCB hole wall using cemented carbide drill. Series of drilling tests of PCB have been carried out to investigate the temperature of cutting edge, dill margin and chips, the cutting torque, the amount of drill wear, the chips evacuation behavior out of drilling hole of the drill and the shape of chips produced during drilling hole. The temperature of cutting edge, dill margin and chips are measured with copper-constantan thermocouples. The cutting torque is measured by a dynamometer; Kistler 9329A. The chips evacuation behavior out of drilling hole of the drill is filmed by a high-speed motion camera and the shape of chips is observed by a microscope. The temperature of cutting edge is higher than that of drill margin and chips. The temperature of cutting edge, dill margin and chips are increasing with an increase of the tool wear. Being filled the chips of PCB in the drill flutes causes an increase of friction between chips and hole wall surface, an increase of temperature of chips.