Gold sulfide replacements of cyanide solutions

At Sandia National Laboratories we have introduced a non-cyanide gold electroplating solution in the Solid State Circuit Processing Lab. This commercially available solution is based on gold sulfite salts. An evaluation of the plating bath and the deposited gold for use in microelectronic circuit fabrication was conducted. The tests included selective plating compatability, wire bonding, soldering, gold resistivity, adherence, and step coverage. The results were all favorable. Precision gold patterns with line widths as small as 2μm and gold thickness over 4μm were selectively plated using a positive photoresist as a plating mask. Also the gold sulfite solution was used to fabricate gold air bridge crossovers for GaAs circuits. The introduction of the non-hazardous sulfite solution for plating high purity gold films will lead to manufacturing processes which are safer to work with and less damaging to the environment.