亜硫酸金塩を用いた自触媒型無電解金めっき浴

Abstract

We studied cyanide-free autocatalytic electroless gold plating baths using sodium gold sulfite and found that gold was autocatalytically deposited when sodium thiocyanate or sodium iodide was added to the sodium gold sulfite solution.We began by studying the effect of pH, additional sodium thiocyanate, gold concentration, and bath temperature on the deposition rate in the bath to which sodium thiocyanate was added. The pH and gold concentration had more pronounced effect than the other parameters studied. Lowering pH increased the deposition rate and increasing the gold concentration proportionally increased the deposition rate. This bath yielded a smooth lemon-yellow gold deposit of 1.28μm at a deposition rate of 0.43μm/h.Gold was provided also autocatalytically deposited by adding sodium iodide. Using this bath, we studied the effect of gold concentration, pH, and the addition of sodium sulfite or sodium iodide on the deposition rate. The gold concentration and the pH had more pronounced effect than the other parameters studied, same as in the case of the bath containing sodium thiocyanate. But the deposit from sodium iodide bath was reddish and rough, then some additional agents were examined. Addition of nicotinic acid and polyethyleneimine gave smoother deposit. In sodium iodide bath, about 1μm/h of deposition rate was given, but according as increase of the plating thickness, growth of dendrite crystal was observed. As for this bath, continuous use more than 1M. T. O. was possible.