<p>Microholes serve as channels for signal connections between layers of printed circuit boards (PCBs). Excess copper in holes can compromise signal integrity, which is typically removed by backdrilling. However, as high-speed PCBs evolve toward miniaturization and high density, removing chips during backdrilling becomes more difficult, often leading to micro-hole plugging. This significantly impacts the performance of high-speed PCBs and can even result in product scraping. To address this issue, this paper investigates the chip removal mechanism during backdrilling of high-speed PCBs to prevent hole plugging. Firstly, a kinematics method is conducted to examine the mechanical behavior and motion law of chip formation, followed by the derivation of expressions for chip removal force and chip moving speed. A chip removal model is then established, along with an evaluation index of chip removal capability. The effects of machining parameters on chip removal efficiency are also analyzed. Finally, backdrilling experiments are carried out to observe the chips winding around the drill bit and measure the hole plugging rate. The experimental results demonstrate that as feed rate increases, the number and density of chips wound around the drill bit slightly decrease, while the hole plugging rate increases proportionally. However, increasing the spindle speed significantly reduces chip winding of tools, lowers hole plugging rates, and decreases the chip removal force during backdrilling. This research provides theoretical insights for overcoming the challenge of microhole plugging in the high-speed PCB industry.</p>