The thinner the electroplated coating, the more difficult it is for manufacturers to reach definitive conclusions regarding its physical properties. A typical example is the assessment of thin gold-cobalt layers on plug connectors, electrical contacts and edge connectors for printed circuit boards. In this case the layer thickness is nowadays only 600 to 800 nanometers. The usual way of determining Vickers hardness is to press a diamond pyramid indenter into the surface and measure the remaining hardness indentation optically. A definitive result is obtained if the indentation depth is equal to a maximum of one-tenth of the depth of the coating being measured. Applying this criterion to thin gold coatings produces indentation depths of only 60 nanometers. At this thickness the long-established Vickers test to ASTM B488-01 has reached its limits.
