Studies On Temperature For Laser Ablation Of Metal Thin Films On Polyimide Substrate

In order to improve ability of satellite communications and meet the demands for light weighted. Now, the satellite is often equipped with antenna reflector which is light weighted. Such antenna reflector components are made of polymer coated with metal thin films(sometimes patterned). Laser etching is used to fabricate for metal thin film patterns so as to achieve high-precision machining on the metal films of material combination system, and protect the polymer base from damage. There are substantial differences in the thermal physical properties between polymer and metal materials, so it is still a challenging technical issue in the actual laser etching process.In this thesis, a special polyimide plates coated with metal(aluminum or copper) thin film which were used more widely as advanced antenna reflector was selected as object of study. Based on the heat conduction theory, a two-dimensional transient physical model of Gaussian distribution pulse laser irradiation composite material was established by software COMSOL Multiphysics. The temperature distribution of metal thin films on polyimide substrate was calculated under irradiation of laser by means of solving the thermal conduction equations, and the influences of the laser parameters changes on the etching process were discussed. The main results have been summarized as follows:(1) copper film is much more difficult than aluminum film for laser etching. Laser power density is the main factor of ablation depth and ablation depth decreases at first then keeps constant with increasing of metal film′s thickness;(2) During the multiple pulse laser etching process, ablation depth linearly increases and ablation radius modestly increases with the increase of pulse number(less than or equal to 10), and ablation morphology develop into horn gradually. As heat is accumulated in the polyimide with the laser etching process, it is appropriate to choose laser parameters of higher power density to well protect the substrate from damage;(3) In the process of laser etching multilayer metal films on polyimide substrate, as the thermal conductivity of metal sandwich is higher than polyimide, ablation depth of upper metal thin film increase and ablation radius decrease. These results of computer simulation can provide a reasonable guidance to the actual process of laser ething metal thin film on polyimide substrate.