Quantitative analysis of trace lead in tin-base lead-free solder by laser-induced plasma spectroscopy in air at atmospheric pressure.

A quantitative analysis of trace lead in tin-base lead-free solder was carried out with laser-induced plasma spectroscopy (LIPS). In order to evaluate the applicability of the technique for rapid in situ analytical purposes, measurements were performed in air at atmospheric pressure, and the emission characteristics of the plasma produced by a Q-switched Nd:YAG laser over a laser energy range of 10 - 90 mJ were investigated using time-resolved spectroscopy. The experimental results showed that the emission intensity of the analysis line (Pb I 405.78 nm) was maximized at a laser energy of around 30 mJ, and a time-resolved measurement of a spectrum with a delay time of 0.4 micros after the laser pulse was effective for reducing the background continuum. Based on the results, lead-free solder certified reference materials were analyzed for trace lead (concentration 174 - 1940 ppm), and a linear calibration curve was obtained with a detection limit of several tens ppm.