The eutectic gold-tin solder has been widely used in the optoelectronics/electronics industry. The prominent characteristics of this solder include high thermal fatigue resistance in addition to excellent thermal properties. An electroplating process was used in this study to deposit Au-30Sn (at%) solder on photoresist laminated substrates, based on previous successful attempts at depositing this alloy on unpatterned, metallized substrates. Difficulties were encountered in the course of electroplating photoresist patterned substrates. The problems were resolved by changing the chemistry of the electroplating solution through decreasing the gold:tin ratio. The problems arose because of penetration of the electroplating solution through pinholes in the photoresist, thus increasing the actual opening area for electroplating.