Improving image quality and pixel resolution via laser pulse dosage increase for fast imaging of large areas with LIBS

Abstract

Laser induced breakdown spectroscopy is a powerful method for spatially resolved and fast elemental analysis of solid samples and represents a handy tool for elemental mapping of micro- structured samples with relatively high sensitivity. However, besides the pulse energy of the laser, the sensitivity of the analysis is further depending on the spot size of the laser pulse and, thus, is competing with the lateral resolution. By applying larger spot sizes and an increased laser dosage, which is the measurement with partially overlapping shots, in imaging experiments followed by the according post data treatment the pixel resolution can be increased while maintaining higher signal-to-noise-ratios compared to the measurement directly with smaller spot sizes. This work explores the influence of different spot sizes and laser dosages on the image quality regarding pixel resolution and sensitivity using a 193 nm excimer laser and a multichannel broadband LIBS spectrometer for imaging experiments on structures of printed circuit boards and microchips. While main and minor constituents, such as copper, tin, zinc, lead, can be measured simultaneously with broadband-LIBS, an additional high-resolution spectrometer with ICCD camera gives access to selected traces, e.g., impurities and contaminants inside materials utilized in PCB and microchip manufacturing.