PARAMETRIC STUDY OF LIPAA PROCESS AND ITS APPLICATIONS

Abstract

The importance and need of laser application in engineering materials processing is well recognized and is the current field of research. The laser is a uniquely versatile tool for processing a remarkable range of metals, alloys, ceramics, glasses, polymers and composites in both laboratory and industrial environments. Light can be produced in pulsed or continuous form, with a wavelength extending from sub ultraviolet through the visible to beyond the infra red, at power levels that spans decades between milli watts and multi kilo watts. Laser based fabrication is possible on both microscopic and macroscopic scales. The application of laser in Micro Electro Mechanical Systems (MEMS) is a novel field of study and is the demand of the day. To fulfill this demand for a simple and cost effective method of transparent materials micromachining, Laser Induced Plasma Assisted Ablation (LIPAA) was developed. In this method, the glass substrate must be transparent at the laser wavelength, so that the laser beam first goes through the substrate, then irradiates a metal target (placed beneath the substrate). At a laser fluence above the ablation threshold for the target and below the damage threshold for the substrate, the plasma generated from the target quickly propagates to the rear surface of the substrate. The strong interactions occur between the laser beam, the plasma, and the substrate. This results in high quality ablation free of cracks and severe distortions on the rear side of the substrate. In the same context the research undertaken was an endeavor to move a step forward in this rapidly advancing field of study. This research work was concentrated on parametric study of LIPAA process with different target materials i.e. stainless steel, cupper, brass and silver with different substrate materials i.e. borosilicate glass, soda lime glass(BK-7) and quartz. This research was carried out at zero to few hundreds microns distance between substrate and target which resulted in achieving the best ablation depth with stainless steel target and quartz as the substrate material. With the increase in gap between target and substrate the ablation depth decreased and surface roughness improved. Moreover colored metallization with silver and brass was successfully carried out. Micro fabrication of a reticule has also been made possible with a line width of 50 micron by the application of LIPAA.