Ablation threshold and etch rate measurements in high-speed ultra-violet (uv) micro-machining of polymers with uv-copper vapour lasers

Material removal rates (etch rates) are given for the ultra-violet (uv) ablation of polyimide, mylar and PETG by uv-Copper Vapour Lasers (CVLs) operating at 255 nm and at pulse repetition rates (prfs) from 4.25 to 20 kHz for fluences in the range 0.08 to 2.2 J/cm². These results and the extrapolated thresholds are compared with those obtained by excimer laser ablation at similar wavelengths and fluences, and with the ablation model of Srinivasan, Smrtic and Babu. Qualitative results for PMMA, which has lower absorption at this wavelength, are also presented. Possible thermal effects of ablation at these high prfs are discussed.