Simulation Analysis Of Movable Laser Etching Of Resin Matrix Composite

The emergence of the laser technology undoubtedly promoted the development of material processing field,especially the short pulse laser with high energy,constant direction,and no contact,which is useful to elaborate processing.Nanosecond pulse laser has great advantages in the surface processing of some satellite antenna reflectors.This kind of antenna reflectors is based on polyimide coated with metal film.The metal film should be processed with highly precision for certain distribution of pattern according to the function requirements.The traditional machining method can’t meet the requirements because the processing size is very small: the metal film is only few microns and the polymer substrate can’t be damaged during processing.However,there are many factors which affect the laser etching result.In order to determine the suitable experimental parameters,a lot of the laser etching testing experiments should be performed.This procedure is not only time-consuming and a waste for materials,but blindly.In this thesis,we used the finite element simulation software COMSOL Multiphysics to simulate the process of laser etching metalpolyimide composites.We hope our work can help to speed experiments and reduce cost.This work mainly includes the following points:(1)The procedure of laser etching metal materials was analyzed and modeled.Beginning with the mechanism of laser and matter interaction,the important thermal physical parameters involved in the heat transfer process and etching process was discussed,and the characteristics of the finite element software and the calculation process was introduced.(2)Geometry model for the laser etching monolayer and multilayer metal-polyimide composites was established.We selected "solid heat transfer interface",and defined the physical parameters used in simulation.We consider the laser as a high energy heat source,and explained the heat transfer equation and boundary conditions of heat conduction,convection,and radiation.The density of grids in the metal film was elaborately increased.(3)Because the heating mode of pulse laser is different from the continuous laser,the etching simulation process can be into the heating and the cooling stage.We calculated the temperature field at any moment through the heating stage and from screened the data: the metal evaporates and becomes metal vapor during etching when the temperature approaches to the evaporation point.The etching profile and temperature field was calculated after the heating stage.The output values are considered as the initial value of the cooling stage.In this way the etching depth and etching contour after sever pulses under a certain movement speed was achieved.By comparing the etching results in different speed,we find that with the increase of the laser scanning pulses,the etching depth increased and gradually reach its maximum,then stayed the same depth,and the etching topography was just like a basin.The laser with higher speed reached its maximum earlier,and its etching topography is shallower.The temperature change in the interface of metal film and polyimide substrate lagged behind the metal film surface.(4)To study the effect of metal interlayer to etching results,the process of laser etching for double metal films is simulated.The etched topography of pure aluminum layer,aluminum-copper metal layers with different thickness,and aluminum-gold metal layers with different thickness were compared.Results showed that,the peak temperature in the interface of aluminum-copper layers and polyimide was lower than that in the single aluminum film,and the interface temperature was lower when the copper film became thicker.So we can selected the interlayer with high thermal conductivity to protect the polyimide base.