Challenges and developments of micro drill bit for printed circuit board: a review
Purpose ‐ The purpose of this paper is to present a clear picture of the challenges of micro drill bit and the developments of novel micro-drill bits for flexible circuit boards, environmental-friendly printed circuit boards (PCBs), high aspect ratio drill bit and ultra-small micro drill bit, as well as the developments of geometry design of micro drill bit. Design/methodology/approach ‐ The paper details the developments trend and challenges of micro drill and PCBs first. Then the current research status of novel micro drill bits for flexible circuit boards, environmental-friendly PCBs, high aspect ratio drill bit, ultra-small micro drill bit are described. Finally, the developments of geometry design and drilling process are reviewed. Findings ‐ To achieve excellent performance for drilling flexible PCB, a large helical angle, large flute/land ratio and small web thickness that guarantee the sharp evacuation capability, are adopted in drill bit design. A small helix angle and an appropriate primary face angle are employed for drill bit to process environmental-friendly printed circuit boards. It is beneficial to implement big helix angle, small primary face angles and small point angles in the design of ultra-small micro drill bit. An optimum web thickness and step feed should be taken into consideration in high aspect ratio drill bits design. Originality/value ‐ The paper reviews different solutions of micro drill bits for the state-of-the-art PCB and the developments of geometry design of drill bit for printed circuit boards.
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