Via drilling

Abstract

Six years after the first commercial excimer lasers had found their way into research laboratories, in 1982 Srinivasan and co-workers reported their discovery of the laser ablation phenomenon [1]. Organic polymers were etched by pulsed ultraviolet (UV) radiation of an ArF excimer laser with a wavelength of 193nm. This discovery led to further activities in academic and industrial research laboratories. Important advances in laser ablation technology took place during the years 1984 and 1985 when researchers at IBM [2, 3] demonstrated that laser ablation of polymers could also be performed with excimer lasers at longer wavelengths: 248nm (KrF), 308nm (XeCl) and 351nm (XeF). This meant simplification of the laser beam propagation and shaping and played a key role in the transfer of the excimer laser from the research laboratory to the manufacturing environment. The KrF excimer laser was the first excimer laser used in an industrial application. Siemens AG put pulsed 248nm radiation in their production line for drilling vias with diameters of 80μm in polyimide dielectric layers of printed circuit boards [4]. © 2005 Springer-Verlag Berlin Heidelberg.