Selective Ablation of Cu-Coated PEEK using Femtosecond Lasers

Femtosecond laser direct writing represents a powerful tool for the precise ablation and patterning of Cu/Ni/Au-coated PEEK substrates, essential for lightweight circuits and conformal antennas in aerospace applications. This study investigates the dynamic interaction between femtosecond laser pulses and multilayer materials, examining how variable pulse widths impact the ablation thresholds of copper and PEEK. Results indicate that, while both materials exhibit increased thresholds with longer pulse durations, copper consistently requires a higher threshold, making selective copper ablation challenging at a wavelength of 1030 nm. This inherent difference necessitates careful control to minimize substrate damage, as copper removal typically leads to partial ablation of the underlying PEEK. We implemented an in-situ monitoring system based on Laser-Induced Breakdown Spectroscopy (LIBS), providing real-time compositional and depth feedback during repeated scans. This system enabled precise identification of the copper-PEEK interface, allowing efficient material removal with minimized impact on the substrate. Post-ablation characterization, utilizing SEM, Raman spectroscopy, and XPS, revealed that optimized femtosecond laser parameters effectively preserve the chemical integrity and morphology of PEEK, reducing thermal degradation and carbonization. This work establishes femtosecond laser direct writing as a viable alternative to traditional multi-step processes, offering refined control over ablation depth and precision in polymer-metal composites, with promising implications for advanced aerospace applications.