Role of photochemical processes in ablative photodecompostion of polyimide

A model of ablative photodecomposition of polyimide is proposed to describe the experimentally observed change of the ablation kinetics from logarithmic to linear, depending on the laser pulse energy. This effect is attributed to a deeper effective penetration of laser radiation into the polymer because of photochemical destruction of the chromophore groups. The newly derived dependence of the etch depth on the energy of a nanosecond laser pulse satisfactorily describes the experimental results.