レーザプレーティングの析出速度に関するめっき液流動の影響

Abstract

Laser plating of fine gold spots was carried out in a flowing solution and the effects of flow rate, argon laser power, and cathode potential were studied on obtaining a high deposition rate and good controllability of the size of deposited spot. High deposition rates of several μm/s are obtained under solution flow conditions. In situ observations revealed that vigorous boiling occurs even in the flowing solution and laser plating is enhanced by strong microstirring due to ejection of bubbles. The main function of solution flow is to remove bubbles rather than to reduce the thicknees of a diffusion layer. The relation between deposition rates, v (μm/s), and flow rates, u (m/s), is written in an empirical equation, v= Cua (C, a; constant), and the values of the exponent are about 0.3 at laser powers less than 1.5 W and about 0.5 at laser powers more than 2 W. Deposition rates increase with increasing laser power, and then they are saturated at laser powers more than 2 W. This is explained by saturation of the effect of solution flow on removal of bubbles, which cause scattering of laser beam and an increase in electrical resistance of the solution. Solution flow has a cooling effect for locally heated solution, resulting in reducing the size of deposited spots.