Description of 355 nm laser ablation of polyimide as a thermal process

UVNd:YAG lasers are widely used in the electronics industry for microvia drilling, cutting, window opening and other selective material removal processes. The models of the laser-material interaction describing these manufacturing processes are mainly based on the experiences of excimer lasers. The different wavelength and energy distribution of frequency tripled Nd:YAG lasers, however require some new approaches. It is still contradictory in the literature how important role the thermal and photochemical processes play in the ablation process. The experimental results presented in this paper show that the models used for excimer lasers are not adaptable to the Gaussian Nd:YAG laser beam. Our model describes the ablation process as a simple thermal process. The simulation and experimental results presented in this paper are in qualitative agreement.