Pulsed laser ablation of electrically insulated features in thin NiCr films

Laser ablation is considered a promising alternative to conventional mask fabrication methods for flexible sensors. For the efficient and high-quality patterning of circuit and electrode geometries, numerous process parameters must be optimized to obtain the necessary laser fluence and pulse overlap that allow for precise, clean cuts in thin, heat-sensitive materials. This study investigates the ability to achieve target cut widths and depths during the pulsed UV laser ablation of NiCr films at various laser powers (0.2 to 1 W), laser scan speeds (0.1 to 0.6 m/s), and pulse frequencies (30 to 100 kHz). Significant variation is observed in the depth, width, and quality of ablated microchannels formed at similar laser fluence and pulse overlap, with the typical fluence-based model giving poor predictions ( R 2 = 0.37 to 0.57). To address this, an improved fluence-based model that incorporates the effect of a moving laser source using a physics-based approach is proposed ( R 2 = 0.62 to 0.82). This model is then used to select process parameters for the fabrication of electrically insulated features (> 5 µm cut depth) with the smallest channel width possible (13.7 µm). This process parameter selection approach has the ability to shorten development times and facilitate the fabrication of custom flexible sensors.