<p>Processing of polymer films with CO₂ lasers often results in significant thermal effects, such as carbonization and melting, due to the use of typical commercial CO₂ lasers with pulse widths of 10 ns or longer. This study proposes a vapor-absorption-based water-assisted technique for reducing the heat-affected zone (HAZ) during laser drilling of polyimide (PI) films using a short-pulse CO₂ laser. The method involves placing water beneath the PI film and irradiating it with multiple laser pulses. Once a through-hole is formed, subsequent pulses interact with the water through the hole, generating water vapor and fine droplets that disperse around and above the film surface. Due to the strong absorption of CO₂ laser light by water, these droplets absorb the subsequent laser pulses, preventing them from reaching the film and thereby suppressing the expansion of thermal damage. Drilling experiments were conducted on PI films with thicknesses of 50&#xa0;μm and 200&#xa0;μm using a CO₂ laser pulse with a 160 ns spike, a 65.8 µs tail, and a spike-to-tail energy ratio of 1:50 at a repetition rate of 200&#xa0;Hz. The results demonstrate a significant reduction in HAZ size compared to conventional dry processing, confirming the effectiveness of the proposed water-assisted approach in mitigating thermal damage during laser drilling.</p>