248 nm excimer laser drilling PI film for nozzle plate application

In this study, drilling of polyimide (PI) film by using a 248 nm excimer laser through photomask projection is presented. The parameter effects of laser fluence, shot number and repetition rate on the processing results are realized. A high-quality of microhole array with 50 μm thick PI film has been fabricated. When the projection process is carried out, differences in the diameters of the microhole in the front and back sides of the PI are observed, which cause a conical shape in the kerf. The formation of this conical shape in terms of laser process parameters is discussed. Besides, to improve the laser machining quality of PI microholes, the effects of the process parameters are investigated and characterized. In addition, before excimer laser drilling PI is conducted, the PI surface is pre-coated with, or left without, a thin film material to observe the formation of debris. The results shows that the formation of debris can be reduced significantly when a pre-coated thin film is applied on the PI surface.