Machinability of the uncoated and Ta–C-coated single-flute microdrills in dry machining of PCBs

Printed circuit boards (PCBs) were the carriers of electronic components, and microhole machining is an essential step for the connection of the different layers in PCBs. Although Ta–C coatings have been used for the cutting tools to increase tool life, the effect of Ta–C coating on microdrills in the dry microhole machining of FR-4 PCBs is unclear. This study focuses on the effect of Ta–C-coated single-flute microdrill on its machinability in drilling of PCBs. The drilling experiments were conducted, and the drilling force signals, hole dimensions, hole accuracy, and tool wear were analyzed in paper. The results show that the Ta–C-coated microdrill exhibited the improved chip evacuation, greater stability, and higher sustainable machinability during the drilling of PCBs. With the feed rate of 5μm/rev, the averaged thrust force and torque reduced 6.0% and 34.6%, respectively. In terms of sustainable machinability, the Ta–C-coated microdrill showed an increase of 13.5% in hole accuracy. After continuous drilling 2800 holes, both the coated and uncoated microdrills exhibited the similar tool wear patterns and mechanisms. However, the Ta–C-coated microdrill experienced a reduction of 10.2% in flank face wear and a decrease of 2.2% in thrust force. In dry machining, Ta–C coating offers the enhanced chip removal and improved sustainable machinability compared to uncoated microdrills.