Depth and surface roughness control on laser micromachined polyimide for direct-write deposition

We are examining surface characteristics of ultraviolet pulsed-laser micromachined structures in polyimide as a function of the incident laser energy and the distance between subsequent laser spots in order to prepare surfaces for laser direct-write deposition of metals. Variations in the spot-to-spot translation distance provide an alternative means of average depth and roughness control when compared to fluence changes and focal distance variations. We find that the average depth is proportional to the inverse of the translation distance, while the root mean square surface roughness reaches a minimum when the translation distance is approximately equal to the full width half maximum of a single ablation mark on the surface. Conductive silver metal lines are deposited on the surface machined features demonstrating the ability to produce conductors with good adhesion over stepped structures on polyimide.