Abstract
In Co‐hardened Au electroplate, the Co will diffuse to the surface with time, where it can form an insulating film. It is of interest to know the chemical form of this surface Co on electrical connectors. Secondary ion mass spectrometry is used to distinguish Co, 
, 
, and cobalt hydroxides in less than full monolayer quantities on impure surfaces. This distinction of compounds is made by comparing the positive and negative secondary ion spectra of Au electroplate with standard samples. Both Ar and 
are used for the primary beam. Spectra are compared from before and after UHV bakeout. It is shown that electroplated Au samples have different Co compounds on their surface depending upon the sample histories. For Co‐hardened Au electroplate heat‐treated at 150°C in air, the surface Co is in the form of 
and Co. When heat‐treated at 200°C in air, the surface Co appears to be in the form of a cobalt hydroxide. Numerous other surface species are also identified and discussed.