Abstract: In the modern electronics manufacturing field, the production of printed circuit boards（PCBs） plays a crucial role, and the micro-drilling technology is the cornerstone of precision manufacturing for electronic products. Depositing high-performance diamond-like carbon（DLC） composite coatings on hard alloy micro-drills can improve the quality of micro-hole drilling. The cathodic arc deposition method with magnetic filtering was employed to investigate the effects of duty cycle variation on the morphology, structure, thickness, and the adhesion of Al Cr Si N-DLC composite coatings deposited on hard alloy specimens. The impact of duty cycle on the quality of PCB drilling was also stndied. The results indicate that the Al Cr Si N-DLC composite coatings exhibit excellent adhesion to the substrate. As the duty cycle increases, the coating thickness and surface roughness decrease, while the wear on the micro-drill’s cutting edge initially decreases and then increases. The positional accuracy of the holes and the roughness of the hole walls are positively correlated with the wear on the cutting edge. The micro-drills exhibit a "self-sharpening" process, which can resolves the issue of chip winding during PCB drilling. Specifically, when the duty cycle is 50%, the prepared coated micro-drills exhibit optimal tool wear and hole wall roughness during drilling, leading to the best overall performance. Optimizing the duty cycle can effectively enhance the performance of Al Cr Si N-DLC coatings, thereby improving the drilling quality and lifespan of hard alloy micro-drills.