Microstructural changes occurring in polyimide films with a thickness of 100 and 200 μm during raster scanning of a 7 × 7 mm surface area with a Nd:YAG laser (wavelength of 1.06 μm) in pulsed mode are studied. Changes in the surface morphology of films, as well as their internal structure, under the influence of various laser processing modes are shown. The stages of formation of bulges on the film surface are shown, and characteristic types of their destruction are identified. It is shown that the formation of pores in the film volume is related to the presence of impurity inclusions containing Si and F. Threshold values of dynamic energy density, which the formation of bulges on the surface of films begins at, are established. The dependences of area, density, and average size of the bulges on the front and back surfaces of a polyimide film with a thickness of 100 and 200 μm on the average power of laser radiation (from 1.60 to 4.75 W) at a pulse repetition frequency of 3, 4, and 5 kHz and a scanning velocity of 3, 7, and 10 cm/s are determined.
Matveev et al. (Wed,) studied this question.