Hongyan Shi

Micro-holes are channels for signal connection between layers of printed circuit boards (PCBs), and excess invalid hole copper in through holes can destroy the integrity of signal, which is usually removed by back-drilling. However, as high-speed PCBs evolve towards miniaturization and high density, it is difficult to remove chips during back-drilling and easily cause micro-holes plugging, seriously affecting the performance of high-speed PCBs and even leading to scrap. Therefore, the chip removal mechanism of high-speed PCB back-drilling is studied to solve hole plugging in this paper. Firstly, kinematics method is used to analyze the mechanical behavior and motion law of chip formation, and then the expressions of chip removal force and chip moving speed are proposed. Secondly, the chip removal model of backdrilling is established, an evaluation index of chip removal capability is put forward, and the influence rule of machining parameters on chip removal of back-drilling is analyzed afterwards. Finally, back-drilling experiments of high-speed PCB are carried out to observe the chips winding around drill bit and calculated the hole plugging rate of back-drilling. The experimental result demonstrates that the number and density of winding chips in the drill bit slightly decrease with the increase of feed rate, and the hole plugging rate rises almost proportionally. Increasing the spindle speed can greatly improve the chip winding of tools and hole plugging, and effectively reduce the chip removal force of back-drilling. The research presented provides theoretical guidance for solving the bottleneck problem of micro-holes plugging during backdrilling in the high-speed PCB industry.

The interdependence between the scheduling method and the production efficiency of a micro-hole drilling production line for printed circuit boards (PCBs) holds significant importance, necessitating the optimization of such a production line’s scheduling. Consequently, this research paper presents a scheduling optimization approach for the micro-hole drilling production line of a PCB, utilizing complex events as its foundation. Initially, a complex event model was constructed to establish correlations among extensive production line data. Subsequently, the typical complex events associated with the micro-hole drilling production line of a PCB were defined, thereby enabling the all-around monitoring of the operation state of such a production line. Furthermore, this study presents the establishment of a production scheduling model for PCB micro-hole drilling. With the goal of minimizing the maximum completion time, the catastrophe genetic algorithm was used to solve the initial scheduling scheme of the printed circuit board micro-hole drilling production line. The reliability and effectiveness of the catastrophe genetic algorithm in solving the hybrid-driven production scheduling problem of complex events were verified. Dynamic scheduling was performed when three complex events occurred in the production line: emergency order insertion, abnormal equipment operation, and tool failure. The scheduling optimization rate after identifying the emergency insertion event could reach 25.1%. The scheduling optimization rate of the production equipment operation event was related to the specific failure time of the equipment. The scheduling optimization rate after identifying the tool failure event could reach 25%. Rescheduling immediately after identifying the tool failure event could exert no effect on the initial scheduling process. It was proven that the identification and rescheduling of complex events can improve the production efficiency of a PCB micro-hole drilling production line.