Gold plating on wafers is used in the semiconductor industry. The dimensions of these microsystems are typically in the order of 5-50 mum with a distance of < 20 mum between the structures. This requires a high and reproducible accuracy. To this purpose, a cupplater for 4-in. wafers was tested and evaluated. The required layer thickness for the process of interest was I tm, with a standard deviation of 30 min. In the first tests it became clear that this uniformity could not be guaranteed under all circumstances. A number of experiments were conducted to identify the parameters influencing the layer thickness distribution. This approach could not reveal the main source of the deviation on the layer thickness. Therefore a different approach was used. Using the ELSY + software package (ELSY + is a non-commercial software package produced by Elsyca, www.elsyca.com), the fluid flow, mass transport and electrochemistry in the cell were calculated. These calculations described the performance of the cupplater very accurately. All the dependencies found before could be validated with the model. Using the software tool, calculations were done to improve the performance of the cupplater by changing the cell geometry.