Thermal and Mechanical Damage in polyimide irradiated by Pulsed CO2 Laser

Polyimide (PI) irradiated by pulsed CO2 laser was simulated by finite element method. The finite element model of PI damaged by pulsed CO2 laser was established. We analyzed the temperature and stress characteristics of PI sample under laser irradiation. The effects of laser pulse width and laser spot radius on the damage effect were discussed. The simulation results show that when the stress does not reach the tensile limit,PI will have melt damage,and the body damage is prior to the surface damage. Under the same laser energy irradiation,the thermal stress produced by short pulsed laser is larger than that produced by long pulsed laser,and the effect of thermal stress damage is better. The peak value of stress decreases with the increase of laser spot radius. The larger spot radius is,the worse damage effect is. The occurrence time of peak stress is independent of spot radius.