| An electroplating process has been developed to deposit gold rich, Au-Sn eutectic alloys onto metallized semiconductor substrates. Commercial exploitation is, however, limited by plating bath lifetime and plating rates. The most effective factors influencing these limitations were determined to be the concentrations of ammonium citrate, potassium tetrachloroaurate, and tin (II) chloride in the electroplating bath. A statistical design of experiments for the gold tin electrodeposition process was performed, and an inverse relationship between shelf life and plating rate were readily apparent from the data analysis. From the obtained process model, two altered optimized solutions were obtained to maximize the shelf life and plating rates. The altered optimized solutions were characterized and plating rates of double and four times that of the standard process were attainable. The shelf life was not improved significantly since turbidity behaviour, which was chosen as a measure of shelf life, and shelf life did not correlate as expected. |
