An established application in industry is the UV micromachining of polyimide polymer foils to produce nozzle arrays for commercial ink-jet printer cartridges. This application requires the illumination of a hole array of 60 to 90mm length and 2 to 5mm width at the mask. The mask openings are 5x demagnified on the substrates. High precision nozzles of 10 to 50 microns in diameter are drilled into the polyimide. Typically a few hundred laser pulses are needed to ablate the nozzles. LEAP Series 5X Optical Systems
LAMBDA SX-Series
Excimer Lasers
Ink-jet nozzle drilling is performed at either excimer laser wavelengths 248 and 308nm at an energy density range of 600 to 800mJ/cm². The ink-jet printer nozzle plate typically has two arrays of nozzles. The homogenizer forms a respective illumination field at the mask of one or two lines of 2mm width where the two arrays are separated by several millimeters. The illuminated mask field contains as much as 300 holes. Telecentric 5x imaging of the mask field on the polyimide substrate ensures the drilling of concentric entrance and exit hole nozzles through typically 50µm thick polyimide foil. A number of 15,000 concentric holes were repetitively drilled in 50µm thick polyimide over the course of a day in the applications lab in order to measure the degree of process repeatability. Statistics on both entrance hole and exit hole diameters exhibit extraordinary precise drilling characteristics achieved with the high power 308nm excimer laser. The overall tolerance of the hole diameters is better than ±0.2µm and the overall tolerance of the roundness never exceeds 0.5µm. Using high UV power of 100 to 300W hundreds of holes can be produced within one second.

Fig. 1 - Through hole ablated in 50µm thick polyimide foil at a wavelength of 308nm.

Click on image for larger view. Fig. 2 - Reproducibility of 308nm drilled ink-jet nozzles (hole diameter and roundness).

Due to the parallel nature of UV excimer laser mask processing of ink-jet nozzles excellent repeatability is achieved. Polymer processing with UV excimer lasers occurs without any heat affected zones and yields particularly clean ablation results. Processing rate is fast and scales with the excimer laser power.

Material	Plastic
Process	Drilling Ablation-Material Removal